A method for inhibiting linear slag inclusion defects in ductile iron castings

Abstract

This invention belongs to the field of high-end ductile iron casting, specifically relating to a method for suppressing linear inclusion defects in ductile iron castings. This method reduces the formation of related oxides, sulfides, and complex inclusions in the molten iron by controlling the combined Mg, Ca, and Al content of the spheroidizing agent, combined with in-ladle inoculation and in-flow inoculation, composite coating of the mold surface, and low-humidity drying control. It also suppresses interface reactions in the molding sand and near-surface sulfur diffusion, thereby reducing near-surface linear inclusion defects in ductile iron castings, improving process stability and casting quality, and is suitable for the production of high-end ductile iron castings.

Description

Technical Field

[0001] This invention belongs to the field of high-end ductile iron casting, specifically relating to a method for suppressing linear inclusion defects in ductile iron castings. Background Technology

[0002] Ductile iron castings, due to their excellent mechanical properties and good casting performance, are widely used in high-end equipment manufacturing fields such as wind power castings, injection molding machine molds, and gearboxes. With the development of industrial equipment towards larger size, higher load capacity, and longer service life, more stringent requirements are being placed on the internal quality and service reliability of ductile iron castings. Inclusions in castings, a common internal defect in ductile iron production, directly affect the mechanical properties and fatigue life of castings. Linear inclusions, in particular, are difficult to detect with conventional visual inspection due to their linear distribution near the surface of the casting, but are clearly visible under fluorescent magnetic particle testing, becoming a challenge and pain point in the quality control of high-end ductile iron castings. These defects can become stress concentration sources during the service life of the casting, leading to material propagation fracture failure under static or dynamic loads, seriously threatening the operational safety of equipment. Therefore, how to effectively prevent linear inclusions in ductile iron castings has become a key technical problem urgently needing to be solved in this field.

[0003] Several solutions exist in current technology to address the problem of slag inclusions in castings. In ferrometallurgy, methods such as carefully selecting furnace charge, controlling the composition of molten iron, and optimizing the ratio of spheroidizing agents and inoculants can effectively reduce the formation of primary and metallurgical reaction inclusions. In mold-making processes, employing multi-layer coatings, controlling the moisture content of molding sand, and optimizing the gating system design can also reduce the incidence of surface inclusions in castings to some extent. Furthermore, some technical solutions involve preheating the mold with hot air before casting to prevent cold shut defects in the casting. These methods have achieved certain results in solving some slag inclusion problems.

[0004] However, existing technologies primarily focus on controlling primary inclusions and metallurgical reaction inclusions, offering limited effectiveness in preventing in-mold regenerated inclusions. In-mold regenerated inclusions refer to secondary inclusions formed after molten iron enters the mold cavity and undergoes complex physicochemical reactions at the mold interface. Microscopic composition analysis shows they are mainly composed of oxides and sulfides of Mg, Al, and Ca. While existing literature discloses control ranges for calcium and aluminum content in spheroidizing agents, such controls often rely on empirical component adjustments, failing to delve into the intrinsic relationship between calcium and aluminum elements and the formation of in-mold regenerated inclusions. Furthermore, they lack a systematic, synergistic design integrating spheroidizing agent composition control with mold interface treatment and cavity drying. Conventional coatings, while preventing sand adhesion, are ineffective in preventing the migration of harmful substances like sulfur and oxygen from the molding sand to the molten iron. Mold preheating technology, focused on raising temperature, does not consider humidity as a control indicator, lacking effective management of moisture content in the mold cavity. The independent optimization of these aspects fails to create a synergistic effect, leaving the problem of in-mold regenerated inclusions unresolved.

[0005] Therefore, developing a method to systematically solve the linear inclusion defect in ductile iron castings by starting from the formation mechanism of in-mold regenerative inclusions has become an urgent need for technological development in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a method for suppressing linear inclusion defects in ductile iron castings. This invention provides an innovative solution for effectively controlling and reducing linear inclusion defects formed by the polymerization of oxides and sulfides of Mg, Al, Ca, and S within the mold cavity through the systematic synergy of a functional coating barrier at the mold interface, humidity control of the mold cavity environment, molten iron smelting purification treatment, control of spheroidizing agent composition, and in-flow inoculation process.

[0007] The first objective of this invention is achieved through the following technical solution:

[0008] A method for suppressing linear inclusion defects in ductile iron castings includes the following steps:

[0009] (a) A functional composite coating is applied to the inner surface of a resin sand casting mold to obtain a casting mold with a coating barrier; the functional composite coating consists of a zircon powder coating layer applied to the inner surface of the casting mold, an anti-sulfur coating layer applied to the zircon powder coating layer, and a graphite coating layer applied to the anti-sulfur coating layer.

[0010] (b) The coated mold is dried with hot air to control the humidity of the mold before pouring to ≤25%RH, so as to obtain a dry mold;

[0011] (c) The furnace charge is added to an electric furnace for smelting to obtain molten iron;

[0012] (d) The molten iron obtained in step (c) is subjected to spheroidization treatment by the immersion method to obtain spheroidized inoculated molten iron;

[0013] The spheroidizing treatment is spheroidizing inoculation inside the molten iron ladle;

[0014] The spheroidizing process involves the addition of a spheroidizing agent and a low-silicon calcium-barium inoculant.

[0015] The spheroidizing agent is a single spheroidizing agent or is composed of two or more spheroidizing agents; when the spheroidizing agent is composed of two or more spheroidizing agents, its Mg, Ca and Al content is calculated as the weighted average of the amount of each spheroidizing agent added;

[0016] The overall chemical composition of the spheroidizing agent satisfies: Mg 4.2-6.0wt%, Ca 0.35-1.00wt%, Al 0.40-0.90wt%;

[0017] The chemical composition of the low-silicon calcium-barium inoculant includes: Si 46-50wt%, Ba 1.0-2.0wt%, Ca 0.2-0.6wt%, Al 0.3-0.8wt%, with the balance being Fe;

[0018] (e) Pour the molten iron obtained in step (d) after spheroidization and inoculation into the dry mold obtained in step (b). During pouring, a low-silicon sulfur-oxygen inoculant is used for in-flow inoculation to obtain ductile iron castings.

[0019] The chemical composition of the low-silicon sulfur-oxygen inoculant includes: Si 50-60wt%, Al 0.5-1.0wt%, Ca 0.5-1.0wt%, RE 1.5-2.0wt%, S≤0.50wt%, O≤1.0wt%, and the balance is Fe.

[0020] The chemical composition of the ductile iron casting is as follows (by mass percentage): Fe 90.0-94.5wt%, C 3.30-3.80wt%, Si 1.80-3.90wt%, Mn≤0.50wt%, P≤0.040wt%, S 0.0050-0.015wt%, Mg 0.035-0.060wt%, RE 0.001-0.010wt%, Ti≤0.030wt%, Cu≤1.0wt%.

[0021] Preferably, in step (a), the Baumé degree of the zircon powder coating is controlled at 50-60 Bé, the Baumé degree of the anti-sulfur coating is controlled at 30-40 Bé, and the Baumé degree of the graphite coating is controlled at 35-45 Bé.

[0022] More preferably, in step (a), the zircon powder coating, anti-sulfur coating and graphite coating are mixed with alcohol before application. The weight ratio of the first coating to alcohol is 4:1.5, and the weight ratio of the second and third coatings to alcohol is 4:2. The mixture is stirred until it is in a suspended state before use.

[0023] In a further preferred embodiment, in step (a), after each layer of coating is applied, it is ignited and burned, and then baked with a blowtorch within 20 seconds after the fire is extinguished; after each layer is applied, wait until the surface temperature of the mold drops below 35°C before applying the next layer of coating; after all coatings are applied, use a blowtorch to bake the mold and core until they are completely dry.

[0024] More preferably, the thickness of the zircon powder coating layer is 100-150 μm.

[0025] More preferably, the thickness of the anti-sulfur coating layer is 100-150 μm.

[0026] More preferably, the thickness of the graphite coating layer is 50-100 μm.

[0027] Preferably, in step (b), the humidity of the mold before casting is controlled to be ≤20%RH.

[0028] Preferably, in step (b), the hot air drying process is as follows: hot air at 80-120°C is introduced into the mold sprue for 4-8 hours, and the hot air is turned off at least 30 minutes before tapping.

[0029] Preferably, in step (c), the furnace charge comprises, by mass percentage: 60-70 wt% pig iron, 25-30 wt% scrap steel, 5-10 wt% recycled material, 0.9-3.10 wt% ferrosilicon, and 0.35-1.0 wt% carbon raiser.

[0030] More preferably, the recycled material is a casting made of QT400-18 material.

[0031] More preferably, the chemical composition of the recycled material satisfies: C 3.6-3.8wt%, Si 1.90-2.20wt%, Mn≤0.20wt%, P≤0.030wt%, S≤0.015wt%, Mg 0.035-0.060wt%, RE≤0.010wt%, Ti≤0.030wt%.

[0032] More preferably, the chemical composition of the scrap steel satisfies: C≤0.30wt%, Si≤0.60wt%, Mn≤0.80wt%, P≤0.030wt%, S≤0.020wt%, Ti≤0.030wt%, Cr≤0.040wt%.

[0033] More preferably, the chemical composition of the pig iron satisfies: C≥4.0wt%, Si0.3-0.6wt%, Mn≤0.1wt%, P≤0.030wt%, S≤0.02wt%, Ti≤0.030wt%, B≤0.009wt%.

[0034] More preferably, the chemical composition of the ferrosilicon satisfies: Si 72-80wt%, Al≤1.20wt%, Mn≤0.50wt%, Cr≤0.50wt%.

[0035] More preferably, the chemical composition of the carbon raiser satisfies: C ≥ 99.0 wt%, S ≤ 0.040 wt%, H ≤ 0.010 wt%, N ≤ 0.010 wt%, ash ≤ 0.40 wt%, volatile matter ≤ 0.50 wt%, and moisture ≤ 0.50 wt%.

[0036] Preferably, in step (c), 0.20 wt% of silicon carbide is added during the batching process for pre-deoxidation.

[0037] More preferably, the chemical composition of the silicon carbide satisfies the following: silicon carbide ≥ 98 wt%, SiO2 ≤ 1.5 wt%, free carbon ≤ 0.5 wt%, free silicon ≤ 1.0 wt%, and particle size 0.2-5 mm ≥ 90 wt%.

[0038] Preferably, in step (c), 80 wt% of the total ferrosilicon is added first during smelting, and the remaining 20 wt% of ferrosilicon is added after removing the slag to adjust the composition.

[0039] Preferably, in step (d), the overall chemical composition of the spheroidizing agent satisfies: Mg 4.2-5.8wt%, Ca 0.35-0.95wt%, Al 0.4-0.85wt%.

[0040] Preferably, in step (d), the spheroidizing agent includes spheroidizing agent A and spheroidizing agent B. The chemical composition of spheroidizing agent A includes: Mg 5.55-6.20wt%, RE 0.30-0.60wt%, Si 44-48wt%, Ca 0.35-1.30wt%, Al 0.40-1.50wt%, with the balance being Fe; the chemical composition of spheroidizing agent B includes: Mg 4.20-4.90wt%, RE 0.40-0.60wt%, Si 44-48wt%, Ca 0.35-1.00wt%, Al 0.35-0.80wt%, with the balance being Fe.

[0041] More preferably, the chemical composition of the A spheroidizing agent includes: 5.55-6.15 wt%, RE 0.30-0.60 wt%, Si 44-48 wt%, Ca 0.8-1.2 wt%, Al 0.40-1.40 wt%, with the balance being Fe; and the chemical composition of the B spheroidizing agent includes: 4.20-4.80 wt%, RE 0.40-0.60 wt%, Si 44-48 wt%, Ca 0.40-0.80 wt%, Al 0.4-0.60 wt%, with the balance being Fe.

[0042] More preferably, the A spheroidizing agent accounts for 70-85 wt% of the total weight of the spheroidizing agent, the B spheroidizing agent accounts for 15-30 wt% of the total weight of the spheroidizing agent, and the total amount added is 1.00-1.15 wt% of the weight of the molten iron.

[0043] More preferably, the particle size of the spheroidizing agent A and the spheroidizing agent B is 8-30 mm.

[0044] Preferably, in step (d), the spheroidizing agent is a single spheroidizing agent with the following chemical composition: Mg 4.20-4.90wt%, RE 0.40-0.60wt%, Si 44-48wt%, Ca 0.35-1.00wt%, Al 0.35-0.80wt%, with the balance being Fe, and the total amount added is 1.30-1.40wt% of the weight of the molten iron.

[0045] Further preferred, the chemical composition of the single spheroidizing agent satisfies: Mg 4.20-4.80wt%, RE 0.40-0.60wt%, Si 44-48wt%, Ca 0.40-0.80wt%, Al≤0.60wt%, with the balance being Fe.

[0046] Preferably, in step (d), the spheroidizing agent is a single spheroidizing agent with the following chemical composition: Mg 5.55-6.00wt%, RE 0.35-0.55wt%, Si 44-48wt%, Ca 0.35-1.00wt%, Al 0.40-0.90wt%, with the balance being Fe, and the total amount added is 1.00-1.10wt% of the weight of the molten iron.

[0047] Further preferred, the chemical composition of the single spheroidizing agent satisfies: Mg 5.55-5.80wt%, RE 0.35-0.55wt%, Si 44-48wt%, Ca 0.80-0.95wt%, Al 0.65-0.85wt%, with the balance being Fe.

[0048] Preferably, in step (d), the particle size of the low-silicon calcium-barium inoculant is 1-6 mm, and the amount added is 0.3-0.5 wt% of the weight of the molten iron.

[0049] More preferably, in step (d), the chemical composition of the low-silicon calcium-barium inoculant includes: Si 46-50wt%, Ba 1.0-2.0wt%, Ca 0.2-0.6wt%, Al 0.3-0.8wt%, with the balance being Fe.

[0050] Preferably, in step (d), molten iron is poured into the other side of the spheroidized alloy during tapping, the tapping time is controlled within 100s, and the magnesium explosion time is controlled within 120-300s.

[0051] Preferably, in step (d), a silicon steel sheet is coated on the low-silicon calcium barium inoculant, and the coating amount of the silicon steel sheet is 0.5-0.8 wt% of the weight of the molten iron.

[0052] More preferably, the silicon steel sheet is carbon steel with the following composition: carbon ≤ 0.3 wt%, silicon ≤ 0.6 wt%, manganese ≤ 0.3 wt%, phosphorus ≤ 0.030 wt%, sulfur ≤ 0.020 wt%, titanium ≤ 0.030 wt%, chromium ≤ 0.040 wt%, copper ≤ 0.030 wt%, molybdenum ≤ 0.010 wt%, aluminum ≤ 0.050 wt%, lead ≤ 0.004 wt%, and the balance being iron.

[0053] Preferably, in step (d), antimony is added to the low-silicon calcium-barium inoculant, and the amount of antimony added is 0.004-0.007 wt% of the weight of the molten iron.

[0054] More preferably, the antimony is metallic antimony with an antimony content of ≥99.9 wt%.

[0055] Preferably, in step (e), the particle size of the low-silicon-sulfur-oxygen inoculant is 0.2-0.7 mm, and the amount added is 0.15-0.25 wt% of the weight of the molten iron.

[0056] More preferably, in step (e), the chemical composition of the low-silicon-sulfur-oxygen inoculant includes: Si 50-60wt%, Al 0.5-1.0wt%, Ca 0.5-1.0wt%, RE 1.5-2.0wt%, S≤0.50wt%, O≤1.0wt%, and the balance is Fe.

[0057] Preferably, before step (e), the molten iron obtained in step (d) is transferred, and during the transfer process, an insulating covering agent is applied to the surface of the molten iron, and the transfer time is controlled to be 6-15 minutes.

[0058] More preferably, the thermal insulation covering agent comprises 62-65 wt% silicon dioxide, 12-15 wt% aluminum oxide, 2.5-3.5 wt% ferric oxide, 0.5-1.5 wt% iron oxide, 1.5-3.5 wt% sodium oxide and 1-1.5 wt% calcium oxide, with a particle size of 0.3-1 mm.

[0059] Preferably, in step (e), the temperature of the molten iron being lifted is 1370-1400℃, and the pouring temperature is 1320-1370℃.

[0060] Preferably, in step (e), the molten iron obtained from step (d) after spheroidization and inoculation treatment is poured within 20 minutes to obtain ductile iron castings.

[0061] More preferably, the ductile iron part is a single bearing housing.

[0062] More preferably, the length of the single bearing housing is 2500-2700mm, the width is 1650-1800mm, and the height is 750-850mm.

[0063] Preferably, the linear slag inclusion depth of the ductile iron casting is ≤8mm.

[0064] This solution, based on the analysis of the microstructure of linear inclusions, reveals that this defect is mainly formed by the polymerization of magnesium, aluminum, and calcium oxides and sulfides within the mold cavity. Magnesium originates from the spheroidizing agent, while aluminum and calcium come from the spheroidizing agent and inoculant. Sulfur and oxygen primarily originate from the molding sand and moisture. Based on this understanding, this invention reduces the tendency for linear inclusions to form by controlling the Mg, Ca, and Al content in the spheroidizing agent within a suitable comprehensive range, combined with inoculant control, mold interface blocking, and low-humidity drying control. For a single spheroidizing agent, its composition is directly controlled; for mixtures of two or more spheroidizing agents, the overall Mg, Ca, and Al content is controlled by the weighted average of the amounts of each agent added. Excessive levels of these elements can increase the formation of oxides, sulfides, and complex inclusions; conversely, excessively low levels may lead to insufficient deoxidation capacity, increased fluctuations in the spheroidizing reaction, or an increased risk of spheroidizing degradation. Therefore, the key to this invention is not to use a single spheroidizing agent, but to control the spheroidizing agent's Mg, Ca, and Al content within a suitable window, so as to coordinate the spheroidizing effect, process stability, and inclusion suppression effect.

[0065] Regarding inoculation control, this invention employs a combination of in-lamb inoculation and in-flow inoculation. During spheroidizing treatment, a low-silicon calcium-barium inoculator is coated onto the spheroidizing agent to reduce ineffective magnesium consumption and promote inclusion flotation and removal. During casting, a low-silicon sulfur-oxygen inoculator is used for in-flow inoculation to supplement the inoculation effect and slow down spheroidization decay, thereby improving the stability of the molten iron and reducing inclusion defects. By controlling the composition and amount of the in-lamb and in-flow inoculators, the risk of increased inclusions due to excessive introduction of active elements such as calcium and aluminum by the inoculator can be reduced.

[0066] Regarding mold interface control, this invention sequentially coats the inner surface of the resin sand mold with zircon powder coating, anti-sulfur coating, and graphite coating to form a three-layer functional composite coating. This composite coating can reduce the possibility of interfacial reactions between sulfur, oxygen, and water vapor in the molding sand and molten iron, thereby reducing the formation of secondary inclusions. Simultaneously, by subjecting the coated mold to deep hot air drying and controlling the mold humidity to below 25% RH before pouring, the amount of oxygen and reaction media introduced by water vapor can be further reduced, lowering the probability of near-surface linear inclusion defects.

[0067] Furthermore, this invention can reduce the adverse effects of spheroidization reaction fluctuations, secondary oxidation of molten iron, and spheroidization decay on inclusion defects by controlling relevant process parameters during molten iron smelting, spheroidization, transfer, and casting. Through the synergistic effect of comprehensive spheroidizing agent composition control, dual inoculation, three-layer composite coating blocking, and low-humidity mold control, this invention can effectively reduce the occurrence of near-surface linear inclusion defects in ductile iron castings. The spheroidizing agent can be a mixture of spheroidizing agent A and spheroidizing agent B to balance compositional flexibility and cost control, but this invention is not limited to this mixing method; as long as the comprehensive Mg, Ca, and Al content of the spheroidizing agent meets the corresponding control requirements, the purpose of this invention can be achieved.

[0068] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0069] 1. This invention reduces the tendency of magnesium, calcium, and aluminum oxides, sulfides, and their complex inclusions to form from the source by controlling the Mg, Ca, and Al in the spheroidizing agent within a suitable comprehensive range, thereby coordinating the spheroidizing effect, process stability, and inclusion suppression effect, and effectively reducing the risk of linear inclusion defects in ductile iron castings.

[0070] 2. This invention uses a low-silicon calcium-barium inoculant for in-lamb inoculation and a low-silicon sulfur-oxygen inoculant for in-flow inoculation, forming a low-inclusion inoculation system that runs through the spheroidizing treatment and casting process. This can reduce the ineffective consumption of magnesium, reduce the risk of inclusion formation, and improve the stability of molten iron.

[0071] 3. By drying the mold with hot air and controlling the mold humidity to below 25%RH before pouring, this invention can effectively reduce the oxygen and reaction medium introduced by water vapor, and significantly reduce the tendency of regenerable inclusions in the mold.

[0072] 4. This invention controls the type, Baumé degree, and coating sequence of the coating on the mold surface, which can improve the stability of the isolation layer on the mold surface, reduce the adverse effects of unfavorable reactions at the molding sand interface on linear inclusion defects, and thus further improve process stability.

[0073] 5. This invention does not rely on a single spheroidizing agent brand or a fixed spheroidizing agent form. As long as the spheroidizing agent meets the corresponding control requirements for Mg, Ca, and Al, it can effectively suppress linear inclusion defects. Therefore, it has a strong applicability and process implementation flexibility. In addition, the mixing method of spheroidizing agent A and spheroidizing agent B can also take into account cost control. Attached Figure Description

[0074] Figure 1 This is a schematic diagram of the structure of the single bearing housing in Embodiment 18 of the present invention;

[0075] Figure 2 A linear inclusion MT photograph of the single bearing housing surface after grinding 1-2 mm, prepared in Example 18 of this invention;

[0076] Figure 3 A linear inclusion MT photograph of the single bearing housing surface after grinding 2-3 mm, prepared in Example 18 of this invention;

[0077] Figure 4 A linear inclusion MT photograph of the single bearing housing surface after grinding 3-4 mm, prepared in Example 18 of this invention;

[0078] Figure 5 Metallographic image (100x) of the single bearing housing prepared in Example 18 of the present invention. Detailed Implementation

[0079] The following will provide a clear and complete description of the concept, specific structure, and technical effects of the present invention in conjunction with the embodiments and accompanying drawings, so as to fully understand the purpose, solution, and effects of the present invention. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0080] The materials used in the embodiments and comparative examples of this invention are described below:

[0081] Pig iron: Q10 pig iron, whose chemical composition meets the following requirements: C≥4.0wt%, Si 0.3-0.6wt%, Mn≤0.1wt%, P≤0.030wt%, S≤0.02wt%, Ti≤0.030wt%, B≤0.009wt%;

[0082] Scrap steel: Ordinary carbon scrap steel, with a chemical composition satisfying C≤0.30wt%, Si≤0.60wt%, Mn≤0.80wt%, P≤0.030wt%, S≤0.020wt%, Ti≤0.030wt%, Cr≤0.040wt%;

[0083] The recycled material is ductile iron recycled material from our own factory;

[0084] Carbide recarrier: Graphitized carbide recarrier with the following chemical composition: C ≥ 99.0 wt%, S ≤ 0.040 wt%, H ≤ 0.010 wt%, N ≤ 0.010 wt%, ash ≤ 0.40 wt%, volatile matter ≤ 0.50 wt%, moisture ≤ 0.50 wt%, and particle size 1-5 mm ≥ 90 wt%.

[0085] Ferrosilicon: FeSi 75 Its chemical composition meets the following requirements: Si 72-80wt%, Al≤1.20wt%, Mn≤0.50wt%, Cr≤0.50wt%.

[0086] Silicon carbide: Metallurgical grade silicon carbide, with a chemical composition that meets the following requirements: silicon carbide ≥ 98 wt%, SiO2 ≤ 1.5 wt%, free carbon ≤ 0.5 wt%, free silicon ≤ 1.0 wt%, and particle size ≥ 90 wt% (0.2-5 mm).

[0087] Zircon powder coatings: Commercially available high-temperature resistant coatings made with zircon powder, whose main components are aluminosilicate and zircon powder, have a gas evolution of ≤25wt%, a zircon powder content of 15-25wt%, and a density of 1.5-2.5g / cm³. 3， Solid content ≥70wt%, original barrel Baumé degree ≥100Bé;

[0088] The present invention will be further illustrated by specific embodiments below, but the scope of protection of the present invention is not limited thereto.

[0089] The ductile iron parts prepared in the examples and comparative examples are single-unit bearing seats. The single-unit bearing seats are prepared by mold preparation, coating application, mold drying, molten iron melting, spheroidizing treatment, in-lamb inoculation, transfer and heat preservation, and in-flow inoculation casting. First, zircon powder coating, anti-sulfur coating, and graphite coating are sequentially applied to the inner surface of the resin sand mold. The Baumé degree of the zircon powder coating is controlled at 50-60 Bé, the anti-sulfur coating at 30-40 Bé, and the graphite coating at 35-45 Bé. After each layer of coating is applied, it is ignited and then baked with a blowtorch within 20 seconds after the flame has burned out. After each layer is applied, the mold surface temperature is allowed to drop below 35℃ before applying the next layer. The thickness of the zircon powder coating layer is 100-150μm, the thickness of the graphite coating layer is 100-150μm, and the thickness of the anti-sulfur coating layer is 50-100μm. After all coatings are applied, hot air at 80-120℃ is introduced into the mold sprue for drying for 4-8 hours. The hot air is turned off 30 minutes before tapping, and the humidity of the mold before pouring is controlled within the range shown in Table 1-3. Subsequently, the hot metal was smelted in an electric furnace according to the following proportions: 10 wt% recycled material, 30 wt% scrap steel, 60 wt% pig iron, 0.90 wt% ferrosilicon, and 0.95 wt% recarburizer. After adjusting the composition of the molten iron, the temperature was raised to 1450°C, and the slag in the furnace was removed before tapping. Next, the obtained molten iron was spheroidized using the pouring method. The type, proportion, composition, and amount of spheroidizing agent were set as shown in Table 1-3. A low-silicon calcium-barium inoculant was then coated on the spheroidizing agent, and the composition and amount of the low-silicon calcium-barium inoculant were set as shown in Table 1-3. Silicon steel sheets were then coated on the inoculant, with a coating amount of 0.5-0.8 wt% of the weight of the molten iron, and 0.004 wt% of antimony by weight of the molten iron was added to the silicon steel sheets. During tapping, the molten iron is flushed onto the other side of the spheroidizing alloy. The tapping time is controlled at 60 seconds, and the magnesia bursting time is controlled at 155 seconds. After the spheroidizing reaction is completed, the spheroidizing slag is removed, and an insulating covering agent is applied to the surface of the molten iron during the transfer process. Finally, a low-silicon, sulfur, and oxygen inoculant is used for in-flow inoculation. The composition and dosage of the low-silicon, sulfur, and oxygen inoculant are set as shown in Tables 1-3. The total time for lifting, transferring, and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1320-1370℃, resulting in a single-unit bearing seat.

[0090] The variation parameters of Examples 1-25 and Comparative Examples 1-18 and 25-42 are detailed in Tables 1, 2 and 3.

[0091] Table 1 Variation parameters of Examples 1-19

[0092]

[0093] Table 2. Variation parameters of Examples 20-25 and Comparative Examples 1-14

[0094]

[0095] Table 3. Variation parameters of comparative examples 15-18 and 25-42

[0096]

[0097] Example 1

[0098] The method for preparing the single bearing housing in Example 1 includes the following steps:

[0099] (1) Zircon powder coating, anti-sulfur coating, and graphite coating are sequentially applied to the inner surface of the resin sand casting mold. The Baumé degree of the zircon powder coating is 55 Bé, the Baumé degree of the anti-sulfur coating is 35 Bé, and the Baumé degree of the graphite coating is 40 Bé. The thickness of the zircon powder coating layer is 130 μm, the thickness of the graphite coating layer is 120 μm, and the thickness of the anti-sulfur coating layer is 95 μm. After each layer of coating is applied, it is ignited and burned, and then baked with a blowtorch within 20 seconds after the fire is extinguished. After each layer is applied, the surface temperature of the casting mold is allowed to drop below 35°C before the next layer of coating is applied.

[0100] (2) After all the coating is completed, hot air at 100°C is introduced into the direct sprue of the mold for drying, and the hot air is turned off 30 minutes before tapping the iron, so that the humidity of the mold before pouring is controlled to 25%RH.

[0101] (3) Weigh out 30wt% scrap steel, 40wt% pig iron, 30wt% recycled material, 0.5wt% ferrosilicon and 0.7wt% carbon raiser by mass percentage, and add them to the electric furnace for smelting; after smelting, adjust the composition of the molten iron to the appropriate level, raise the temperature to 1450℃, and remove the slag in the furnace before tapping the iron.

[0102] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0103] During the transfer of molten iron, an insulating covering agent is applied to the surface of the molten iron. A low-silicon, sulfur, and oxygen inoculant is used for in-flow inoculation. The inoculant composition is 0.70 wt% Ca, 0.80 wt% Al, and 1.70 wt% RE, with an addition amount of 0.15 wt% of the molten iron weight. The total time for lifting, transferring, and pouring the molten iron is controlled to be within 11 minutes, and the pouring temperature is 1350℃. The resulting single-unit bearing housing of Example 1 is obtained.

[0104] Example 2

[0105] The method for preparing the single bearing housing in Example 2 includes the following steps:

[0106] (1-3) Proceed according to step (1-3) of Example 1.

[0107] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. 0.40wt% of the weight of the molten iron is covered on the spheroidizing agent with a low-silicon calcium barium inoculant, the composition of which is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then 0.50wt% of the weight of the molten iron is covered on the inoculant with a silicon steel sheet, and 0.004wt% of the weight of the molten iron is added to the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0108] (5) During the transfer of molten iron, an insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is 0.70wt% Ca, 0.80wt% Al, and 1.70wt% RE, and the amount added is 0.20wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the single bearing seat of Example 2 is obtained by pouring.

[0109] Example 3

[0110] The method for preparing the single bearing housing in Example 3 includes the following steps:

[0111] (1-3) Proceed according to step (1-3) of Example 1.

[0112] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. 0.50wt% of the weight of the molten iron is covered on the spheroidizing agent with a low-silicon calcium barium inoculant, the composition of which is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then 0.50wt% of the weight of the molten iron is covered on the inoculant with a silicon steel sheet, and 0.004wt% of the weight of the molten iron is added to the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0113] (5) During the transfer of molten iron, a heat-insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is 0.70wt% Ca, 0.80wt% Al, and 1.70wt% RE, and the amount added is 0.25wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Example 3 is obtained by pouring.

[0114] Example 4

[0115] The method for preparing the single bearing housing in Example 4 includes the following steps:

[0116] (1-3) Proceed according to step (1-3) of Example 1.

[0117] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 80wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 20wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.10wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0118] (5) Following step (5) of Example 1, the single bearing housing of Example 4 was obtained by casting.

[0119] Example 5

[0120] The method for preparing the single bearing housing in Example 5 includes the following steps:

[0121] (1-3) Proceed according to step (1-3) of Example 1.

[0122] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 80wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 20wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.10wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.40wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0123] (5) During the transfer of molten iron, an insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is 0.70wt% Ca, 0.80wt% Al, and 1.70wt% RE, and the amount added is 0.20wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Example 5 is obtained by pouring.

[0124] Example 6

[0125] The method for preparing the single bearing housing in Example 6 includes the following steps:

[0126] (1-3) Proceed according to step (1-3) of Example 1.

[0127] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 80wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 20wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.10wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. 0.50wt% of the weight of the molten iron is covered on the spheroidizing agent with a low-silicon calcium barium inoculant, the composition of which is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then 0.50wt% of the weight of the molten iron is covered on the inoculant with a silicon steel sheet, and 0.004wt% of the weight of the molten iron is added to the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0128] (5) During the transfer of molten iron, an insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is 0.70wt% Ca, 0.80wt% Al, and 1.70wt% RE, and the amount added is 0.25wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Example 6 is obtained by pouring.

[0129] Example 7

[0130] The method for preparing the single bearing housing in Example 7 includes the following steps:

[0131] (1-3) Proceed according to step (1-3) of Example 1.

[0132] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 85wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 15wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.09wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0133] (5) Following step (5) of Example 1, the single bearing housing of Example 7 was obtained by casting.

[0134] Example 8

[0135] The method for preparing the single bearing housing in Example 8 includes the following steps:

[0136] (1-3) Proceed according to step (1-3) of Example 1.

[0137] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 85wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 15wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.09wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.40wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0138] (5) During the transfer of molten iron, an insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is 0.70wt% Ca, 0.80wt% Al, and 1.70wt% RE, and the amount added is 0.20wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Example 8 is obtained by pouring.

[0139] Example 9

[0140] The method for preparing the single bearing housing in Example 9 includes the following steps:

[0141] (1-3) Proceed according to step (1-3) of Example 1.

[0142] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 85wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 15wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.09wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. 0.50wt% of the weight of the molten iron is covered on the spheroidizing agent with a low-silicon calcium barium inoculant, the composition of which is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then 0.50wt% of the weight of the molten iron is covered on the inoculant with a silicon steel sheet, and 0.004wt% of the weight of the molten iron is added to the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0143] (5) During the transfer of molten iron, a heat-insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is 0.70wt% Ca, 0.80wt% Al, and 1.70wt% RE, and the amount added is 0.25wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Example 9 is obtained by pouring.

[0144] Example 10

[0145] The method for preparing the single bearing housing in Example 10 includes the following steps:

[0146] (1-3) Proceed according to step (1-3) of Example 1.

[0147] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the flushing method. B spheroidizing agent is used, with a total addition amount of 1.36 wt% of the molten iron weight. The composition of B spheroidizing agent is Al 0.40 wt%, Ca 0.60 wt%, and Mg 4.50 wt%. A low-silicon calcium-barium inoculant of 0.30 wt% of the molten iron weight is placed on the spheroidizing agent, the composition of which is Ba 1.85 wt%, Ca 0.50 wt%, and Al 0.65 wt%. Then, a silicon steel sheet of 0.50 wt% of the molten iron weight is placed on the inoculant, and antimony of 0.004 wt% of the molten iron weight is added to the silicon steel sheet. When tapping the iron, the molten iron is flushed to the other side of the spheroidizing alloy. The tapping time is controlled at 60 s, and the magnesium explosion time is controlled at 155 s. After the spheroidizing reaction is completed, the slag is removed, ideally until no floating slag is visible on the surface of the molten iron.

[0148] (5) Following step (5) of Example 1, the single bearing housing of Example 10 was obtained by casting.

[0149] Example 11

[0150] The method for preparing the single bearing housing in Example 11 includes the following steps:

[0151] (1-3) Proceed according to step (1-3) of Example 1.

[0152] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the flushing method. A single spheroidizing agent is used, and the total amount of spheroidizing agent added is 1.05 wt% of the weight of the molten iron. The composition of the single spheroidizing agent is Al 0.85 wt%, Ca 0.90 wt%, and Mg 5.80 wt%. A low-silicon calcium-barium inoculant of 0.30 wt% of the weight of the molten iron is covered on the spheroidizing agent. The composition of the low-silicon calcium-barium inoculant is Ba 1.85 wt%, Ca 0.50 wt%, and Al 0.65 wt%. Then, a silicon steel sheet of 0.50 wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004 wt% of the weight of the molten iron is added to the silicon steel sheet. When tapping the iron, the molten iron is flushed into the other side of the spheroidized alloy. The tapping time is controlled at 60 s, and the magnesium explosion time is controlled at 155 s. After the spheroidizing reaction is completed, the spheroidizing reaction slag is removed, and it is advisable that there is no floating slag visible on the surface of the molten iron.

[0153] (5) Following step (5) of Example 1, the single bearing housing of Example 11 was obtained by casting.

[0154] Example 12

[0155] The method for preparing the single bearing housing in Example 12 includes the following steps:

[0156] (1-3) Proceed according to step (1-3) of Example 1.

[0157] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.20wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0158] (5) Following step (5) of Example 1, the single bearing housing of Example 12 was obtained by casting.

[0159] Example 13

[0160] The method for preparing the single bearing housing in Example 13 includes the following steps:

[0161] (1-3) Proceed according to step (1-3) of Example 1.

[0162] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 80wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 20wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.10wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.20wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0163] (5) Following step (5) of Example 1, the single bearing housing of Example 13 was obtained by casting.

[0164] Example 14

[0165] The method for preparing the single bearing housing in Example 14 includes the following steps:

[0166] (1-3) Proceed according to step (1-3) of Example 1.

[0167] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 85wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 15wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.09wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.20wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0168] (5) Following step (5) of Example 1, the single bearing housing of Example 14 was obtained by casting.

[0169] Example 15

[0170] The method for preparing the single bearing housing in Example 15 includes the following steps:

[0171] (1-3) Proceed according to step (1-3) of Example 1.

[0172] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.20wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0173] (5) Following step (5) of Example 1, the single bearing housing of Example 15 was obtained by casting.

[0174] Example 16

[0175] The method for preparing the single bearing housing in Example 16 includes the following steps:

[0176] (1-3) Proceed according to step (1-3) of Example 1.

[0177] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 80wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 20wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.10wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.20wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0178] (5) Following step (5) of Example 1, the single bearing housing of Example 16 was obtained by casting.

[0179] Example 17

[0180] The method for preparing the single bearing housing in Example 17 includes the following steps:

[0181] (1-3) Proceed according to step (1-3) of Example 1.

[0182] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 85wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 15wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.09wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.20wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0183] (5) Following step (5) of Example 1, the single bearing housing of Example 17 was obtained by casting.

[0184] Example 18

[0185] The method for preparing the single bearing housing in Example 18 includes the following steps:

[0186] (1) Follow the steps (1) of Example 1.

[0187] (2) After all the coating is completed, hot air at 100°C is introduced into the direct sprue of the mold for drying, and the hot air is turned off 30 minutes before tapping the iron, so that the humidity of the mold before pouring is controlled at 18%RH.

[0188] (3-5) Following the steps (3-5) of Example 1, the single bearing housing of Example 18 was obtained by casting.

[0189] Example 19

[0190] The method for preparing the single bearing housing in Example 19 includes the following steps:

[0191] (1) Follow the steps (1) of Example 1.

[0192] (2) After all the coating is completed, hot air at 100°C is introduced into the direct sprue of the mold for drying, and the hot air is turned off 30 minutes before tapping the iron, so that the humidity of the mold before pouring is controlled at 19%RH.

[0193] (3-5) Following the steps (3-5) of Example 1, the single bearing housing of Example 19 was obtained by casting.

[0194] Example 20

[0195] The method for preparing the single bearing housing in Example 20 includes the following steps:

[0196] (1) Follow the steps (1) of Example 1.

[0197] (2) After all the coating is completed, hot air at 100°C is introduced into the direct sprue of the mold for drying, and the hot air is turned off 30 minutes before tapping the iron, so that the humidity of the mold before pouring is controlled at 20%RH.

[0198] (3-5) Following the steps (3-5) of Example 1, the single bearing housing of Example 20 was obtained by casting.

[0199] Example 21

[0200] The method for preparing the single bearing housing in Example 21 includes the following steps:

[0201] (1) Follow the steps (1) of Example 1.

[0202] (2) After all the coating is completed, hot air at 100°C is introduced into the direct sprue of the mold for drying, and the hot air is turned off 30 minutes before tapping the iron, so that the humidity of the mold before pouring is controlled at 21%RH.

[0203] (3-5) Following the steps (3-5) of Example 1, the single bearing housing of Example 21 was obtained by casting.

[0204] Example 22

[0205] The method for preparing the single bearing housing in Example 22 includes the following steps:

[0206] (1) Follow the steps (1) of Example 1.

[0207] (2) After all the coating is completed, hot air at 100°C is introduced into the direct sprue of the mold for drying, and the hot air is turned off 30 minutes before tapping the iron, so that the humidity of the mold before pouring is controlled at 22%RH.

[0208] (3-5) Following the steps (3-5) of Example 1, the single bearing housing of Example 22 was obtained by casting.

[0209] Example 23

[0210] The method for preparing the single bearing housing in Example 23 includes the following steps:

[0211] (1) Follow the steps (1) of Example 1.

[0212] (2) After all the coating is completed, hot air at 100°C is introduced into the direct sprue of the mold for drying, and the hot air is turned off 30 minutes before tapping the iron, so that the humidity of the mold before pouring is controlled at 23%RH.

[0213] (3-5) Following the steps (3-5) of Example 1, the single bearing housing of Example 23 was obtained by casting.

[0214] Example 24

[0215] The method for preparing the single bearing housing in Example 24 includes the following steps:

[0216] (1) Follow the steps (1) of Example 1.

[0217] (2) After all the coating is completed, hot air at 100°C is introduced into the direct sprue of the mold for drying, and the hot air is turned off 30 minutes before tapping the iron, so that the humidity of the mold before pouring is controlled at 24%RH.

[0218] (3-5) Following the steps (3-5) of Example 1, the single bearing housing of Example 24 was obtained by casting.

[0219] Example 25

[0220] The method for preparing the single bearing housing in Example 25 includes the following steps:

[0221] (1-5) Following the steps (1-5) of Example 1, the single bearing housing of Example 25 was obtained by casting.

[0222] Comparative Example 1

[0223] The method for preparing the single bearing housing of Comparative Example 1 includes the following steps:

[0224] (1-3) Proceed according to step (1-3) of Example 1.

[0225] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the flushing method. The spheroidizing agent used is A spheroidizing agent, and the total amount of spheroidizing agent added is 1.05 wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90 wt%, Ca 1.00 wt%, and Mg 5.80 wt%. A low-silicon calcium-barium inoculant of 0.30 wt% of the weight of the molten iron is covered on the spheroidizing agent. The composition of the low-silicon calcium-barium inoculant is Ba 1.85 wt%, Ca 0.50 wt%, and Al 0.65 wt%. Then, a silicon steel sheet of 0.50 wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004 wt% of the weight of the molten iron is added to the silicon steel sheet. When tapping the iron, the molten iron is flushed into the other side of the spheroidized alloy. The tapping time is controlled at 60 s, and the magnesium explosion time is controlled at 155 s. After the spheroidizing reaction is completed, the spheroidizing reaction slag is removed, and it is advisable that there is no floating slag visible on the surface of the molten iron.

[0226] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 1 was obtained by casting.

[0227] Comparative Example 2

[0228] The method for preparing the single bearing housing of Comparative Example 2 includes the following steps:

[0229] (1-3) Proceed according to step (1-3) of Example 1.

[0230] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.50wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0231] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 2 was obtained by casting.

[0232] Comparative Example 3

[0233] The method for preparing the single bearing housing of Comparative Example 3 includes the following steps:

[0234] (1-3) Proceed according to step (1-3) of Example 1.

[0235] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 80wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 20wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.10wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.50wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0236] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 3 was obtained by casting.

[0237] Comparative Example 4

[0238] The method for preparing the single bearing housing of Comparative Example 4 includes the following steps:

[0239] (1-3) Proceed according to step (1-3) of Example 1.

[0240] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 85wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 15wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.09wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.50wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0241] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 4 was obtained by casting.

[0242] Comparative Example 5

[0243] The method for preparing the single bearing housing of Comparative Example 5 includes the following steps:

[0244] (1-3) Proceed according to step (1-3) of Example 1.

[0245] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 2.00wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0246] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 5 was obtained by casting.

[0247] Comparative Example 6

[0248] The method for preparing the single bearing housing of Comparative Example 6 includes the following steps:

[0249] (1-3) Proceed according to step (1-3) of Example 1.

[0250] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 80wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 20wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.10wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 2.00wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent with a low-silicon calcium barium inoculant, the composition of which is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then 0.50wt% of the weight of the molten iron is covered on the inoculant with a silicon steel sheet, and 0.004wt% of the weight of the molten iron is added to the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0251] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 6 was obtained by casting.

[0252] Comparative Example 7

[0253] The method for preparing the single bearing housing of Comparative Example 7 includes the following steps:

[0254] (1-3) Proceed according to step (1-3) of Example 1.

[0255] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 85wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 15wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.09wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 2.00wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0256] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 7 was obtained by casting.

[0257] Comparative Example 8

[0258] The method for preparing the single bearing housing of Comparative Example 8 includes the following steps:

[0259] (1-3) Proceed according to step (1-3) of Example 1.

[0260] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.10wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0261] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 8 was obtained by casting.

[0262] Comparative Example 9

[0263] The method for preparing the single bearing housing of Comparative Example 9 includes the following steps:

[0264] (1-3) Proceed according to step (1-3) of Example 1.

[0265] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 80wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 20wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.10wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.10wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0266] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 9 was obtained by casting.

[0267] Comparative Example 10

[0268] The method for preparing the single bearing housing of Comparative Example 10 includes the following steps:

[0269] (1-3) Proceed according to step (1-3) of Example 1.

[0270] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 85wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 15wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.09wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.10wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium-barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium-barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0271] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 10 was obtained by casting.

[0272] Comparative Example 11

[0273] The method for preparing the single bearing housing of Comparative Example 11 includes the following steps:

[0274] (1-3) Proceed according to step (1-3) of Example 1.

[0275] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 1.20wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0276] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 11 was obtained by casting.

[0277] Comparative Example 12

[0278] The method for preparing the single bearing housing of Comparative Example 12 includes the following steps:

[0279] (1-3) Proceed according to step (1-3) of Example 1.

[0280] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 80wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 20wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.10wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 1.20wt%, Mg 4.55wt%. A low-silicon calcium-barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium-barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0281] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 12 was obtained by casting.

[0282] Comparative Example 13

[0283] The method for preparing the single bearing housing of Comparative Example 13 includes the following steps:

[0284] (1-3) Proceed according to step (1-3) of Example 1.

[0285] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 85wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 15wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.09wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 1.20wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0286] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 13 was obtained by casting.

[0287] Comparative Example 14

[0288] The method for preparing the single bearing housing of Comparative Example 14 includes the following steps:

[0289] (1-3) Proceed according to step (1-3) of Example 1.

[0290] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 1.00wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0291] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 14 was obtained by casting.

[0292] Comparative Example 15

[0293] The method for preparing the single bearing housing of Comparative Example 15 includes the following steps:

[0294] (1-3) Proceed according to step (1-3) of Example 1.

[0295] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 80wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 20wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.10wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 1.00wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0296] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 15 was obtained by casting.

[0297] Comparative Example 16

[0298] The method for preparing the single bearing housing of Comparative Example 16 includes the following steps:

[0299] (1-3) Proceed according to step (1-3) of Example 1.

[0300] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 85wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 15wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.09wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 1.00wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0301] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 16 was obtained by casting.

[0302] Comparative Example 17

[0303] The method for preparing the single bearing housing of Comparative Example 17 includes the following steps:

[0304] (1) Follow the steps (1) of Example 1.

[0305] (2) After all the coating is completed, hot air at 100°C is introduced into the direct sprue of the mold for drying, and the hot air is turned off 30 minutes before tapping the iron, so that the humidity of the mold before pouring is controlled at 30%RH.

[0306] (3-5) Following the steps (3-5) of Example 1, the single bearing housing of Comparative Example 17 was cast.

[0307] Comparative Example 18

[0308] The method for preparing the single bearing housing of Comparative Example 18 includes the following steps:

[0309] (1) Follow the steps (1) of Example 1.

[0310] (2) After all the coating is completed, hot air at 100°C is introduced into the direct sprue of the mold for drying, and the hot air is turned off 30 minutes before tapping the iron, so that the humidity of the mold before pouring is controlled at 35%RH.

[0311] (3-5) Following the steps (3-5) of Example 1, the single bearing housing of Comparative Example 18 was cast.

[0312] Comparative Example 19

[0313] The method for preparing the single bearing housing of Comparative Example 19 includes the following steps:

[0314] (1) Apply ordinary paint to the inner surface of the resin sand casting mold. After each layer of paint is applied, it is ignited and burned, and then baked with a blowtorch within 20 seconds after the fire is extinguished. After each layer is applied, wait for the surface temperature of the casting mold to drop below 35°C before applying the next layer of paint.

[0315] (2) After all the coating is completed, hot air at 100°C is introduced into the direct sprue of the mold for drying, and the hot air is turned off 30 minutes before tapping the iron, so that the humidity of the mold before pouring is controlled to 25%RH.

[0316] (3-5) Following the steps (3-5) of Example 1, the single bearing housing of Comparative Example 19 was cast.

[0317] Comparative Example 20

[0318] The method for preparing the single bearing housing of Comparative Example 20 includes the following steps:

[0319] (1) Zircon powder coating, anti-sulfur coating and graphite coating were sequentially applied to the inner surface of the resin sand mold. The Baumé degree of the zircon powder coating was 45 Bé, that of the anti-sulfur coating was 25 Bé, and that of the graphite coating was 30 Bé. During the application process, the coating adhesion was poor, the sand mold was knocked off, and the casting was not completed.

[0320] Comparative Example 21

[0321] The method for preparing the single bearing housing of Comparative Example 21 includes the following steps:

[0322] (1) Zircon powder coating, anti-sulfur coating and graphite coating were sequentially applied to the inner surface of the resin sand mold. The Baumé degree of the zircon powder coating was 65 Bé, that of the anti-sulfur coating was 45 Bé, and that of the graphite coating was 50 Bé. During the application process, the coating adhesion was poor, the sand mold was knocked off, and the casting was not completed.

[0323] Comparative Example 22

[0324] The method for preparing the single bearing housing of Comparative Example 22 includes the following steps:

[0325] (1) Graphite coating, anti-sulfur coating and zircon powder coating were applied sequentially to the inner surface of the resin sand mold. During the application process, the coating foamed and powder fell off, the sand mold was destroyed, and the casting was not completed.

[0326] Comparative Example 23

[0327] The method for preparing the single bearing housing of Comparative Example 23 includes the following steps:

[0328] (1) Anti-sulfur coating, graphite coating and zircon powder coating were applied sequentially to the inner surface of the resin sand mold. During the application process, the coating foamed and powder fell off, the sand mold was destroyed, and the casting was not completed.

[0329] Comparative Example 24

[0330] The method for preparing the single bearing housing of Comparative Example 24 includes the following steps:

[0331] (1) Apply anti-sulfur coating, zircon powder coating and graphite coating to the inner surface of the resin sand casting mold in sequence. After each layer of coating is applied, it is ignited and burned, and then baked with a blowtorch within 20 seconds after the fire is extinguished. After each layer is applied, wait for the surface temperature of the casting mold to drop below 35°C before applying the next layer of coating.

[0332] (2) After all the coating is completed, hot air at 100°C is introduced into the direct sprue of the mold for drying, and the hot air is turned off 30 minutes before tapping the iron, so that the humidity of the mold before pouring is controlled to 25%RH.

[0333] (3-5) Following the steps (3-5) of Example 1, the single bearing housing of Comparative Example 24 was obtained by casting.

[0334] Comparative Example 25

[0335] The method for preparing the single bearing housing of Comparative Example 25 includes the following steps:

[0336] (1-3) Proceed according to step (1-3) of Example 1.

[0337] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the flushing method. Ordinary spheroidizing agent is used, and the total amount of spheroidizing agent added is 1.13 wt% of the weight of molten iron. The composition of the ordinary spheroidizing agent is Al 1.20 wt%, Ca 1.40 wt%, and Mg 5.90 wt%. A low-silicon calcium-barium inoculant of 0.30 wt% of the weight of molten iron is covered on the spheroidizing agent. The composition of the low-silicon calcium-barium inoculant is Ba 1.85 wt%, Ca 0.50 wt%, and Al 0.65 wt%. Then, a silicon steel sheet of 0.50 wt% of the weight of molten iron is covered on the inoculant, and antimony of 0.004 wt% of the weight of molten iron is added to the silicon steel sheet. When tapping the iron, the molten iron is flushed into the other side of the spheroidized alloy. The tapping time is controlled at 60 s, and the magnesium explosion time is controlled at 155 s. After the spheroidizing reaction is completed, the spheroidizing reaction slag is removed, and it is advisable that there is no floating slag visible on the surface of the molten iron.

[0338] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 25 was obtained by casting.

[0339] Comparative Example 26

[0340] The method for preparing the single bearing housing of Comparative Example 26 includes the following steps:

[0341] (1-3) Proceed according to step (1-3) of Example 1.

[0342] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. 0.30wt% of ordinary ladle inoculant by weight of molten iron is covered on the spheroidizing agent, wherein the composition of ordinary ladle inoculant is Ba 2.40wt%, Ca 1.40wt%, Al 1.30wt%; then 0.50wt% of silicon steel sheet by weight of molten iron is covered on the inoculant, and 0.004wt% of antimony by weight of molten iron is added to the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0343] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 26 was obtained by casting.

[0344] Comparative Example 27

[0345] The method for preparing the single bearing housing of Comparative Example 27 includes the following steps:

[0346] (1-4) Proceed according to steps (1-4) of Example 1.

[0347] (5) During the transfer of molten iron, an insulating covering agent is applied to the surface of the molten iron. A common inoculant is used for in-flow inoculation. The composition of the common inoculant is Ca 1.40wt%, Al 1.30wt%, RE 0, and the amount added is 0.15wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Comparative Example 27 is obtained by pouring.

[0348] Comparative Example 28

[0349] The method for preparing the single bearing housing of Comparative Example 28 includes the following steps:

[0350] (1-3) Proceed according to step (1-3) of Example 1.

[0351] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 1.20wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0352] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 28 was obtained by casting.

[0353] Comparative Example 29

[0354] The method for preparing the single bearing housing of Comparative Example 29 includes the following steps:

[0355] (1-3) Proceed according to step (1-3) of Example 1.

[0356] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.40wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 1.20wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0357] (5) During the transfer of molten iron, a heat-insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is 0.70wt% Ca, 0.80wt% Al, and 1.70wt% RE, and the amount added is 0.20wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Comparative Example 29 is obtained by pouring.

[0358] Comparative Example 30

[0359] The method for preparing the single bearing housing of Comparative Example 30 includes the following steps:

[0360] (1-3) Proceed according to step (1-3) of Example 1.

[0361] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. 0.50wt% of the weight of the molten iron is covered on the spheroidizing agent with a low-silicon calcium barium inoculant, the composition of which is Ba 1.85wt%, Ca 1.20wt%, Al 0.65wt%; then 0.50wt% of the weight of the molten iron is covered on the inoculant with a silicon steel sheet, and 0.004wt% of the weight of the molten iron is added to the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0362] (5) During the transfer of molten iron, a heat-insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is 0.70wt% Ca, 0.80wt% Al, and 1.70wt% RE, and the amount added is 0.25wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Comparative Example 30 is obtained by pouring.

[0363] Comparative Example 31

[0364] The method for preparing the single bearing housing of Comparative Example 31 includes the following steps:

[0365] (1-3) Proceed according to step (1-3) of Example 1.

[0366] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent with a low-silicon calcium barium inoculant, the composition of which is Ba 0.50wt%, Ca 0.50wt%, Al 0.65wt%; then 0.50wt% of the weight of the molten iron is covered on the inoculant with a silicon steel sheet, and 0.004wt% of the weight of the molten iron is added to the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0367] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 31 was obtained by casting.

[0368] Comparative Example 32

[0369] The method for preparing the single bearing housing of Comparative Example 32 includes the following steps:

[0370] (1-3) Proceed according to step (1-3) of Example 1.

[0371] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.40wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 0.50wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0372] (5) During the transfer of molten iron, a heat-insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is 0.70wt% Ca, 0.80wt% Al, and 1.70wt% RE, and the amount added is 0.20wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Comparative Example 32 is obtained by pouring.

[0373] Comparative Example 33

[0374] The method for preparing the single bearing housing of Comparative Example 33 includes the following steps:

[0375] (1-3) Proceed according to step (1-3) of Example 1.

[0376] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 1.00wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. 0.50wt% of the weight of the molten iron is covered on the spheroidizing agent with a low-silicon calcium barium inoculant, the composition of which is Ba 0.50wt%, Ca 0.50wt%, Al 0.65wt%; then 0.50wt% of the weight of the molten iron is covered on the inoculant with a silicon steel sheet, and 0.004wt% of the weight of the molten iron is added to the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0377] (5) During the transfer of molten iron, a heat-insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is 0.70wt% Ca, 0.80wt% Al, and 1.70wt% RE, and the amount added is 0.25wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Comparative Example 33 is obtained by pouring.

[0378] Comparative Example 34

[0379] The method for preparing the single bearing housing of Comparative Example 34 includes the following steps:

[0380] (1-4) Proceed according to steps (1-4) of Example 1.

[0381] (5) During the transfer of molten iron, a heat-insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is 0.70wt% Ca, 2.00wt% Al, and 1.70wt% RE, and the amount added is 0.15wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Comparative Example 34 is obtained by pouring.

[0382] Comparative Example 35

[0383] The method for preparing the single bearing housing of Comparative Example 35 includes the following steps:

[0384] (1-4) Proceed according to steps (1-4) of Example 1.

[0385] (5) During the transfer of molten iron, a heat-insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is 0.70wt% Ca, 2.00wt% Al, and 1.70wt% RE, and the amount added is 0.20wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Comparative Example 35 is obtained by pouring.

[0386] Comparative Example 36

[0387] The method for preparing the single bearing housing of Comparative Example 36 includes the following steps:

[0388] (1-4) Proceed according to steps (1-4) of Example 1.

[0389] (5) During the transfer of molten iron, a heat-insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is 0.70wt% Ca, 2.00wt% Al, and 1.70wt% RE, and the amount added is 0.25wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Comparative Example 36 is obtained by pouring.

[0390] Comparative Example 37

[0391] The method for preparing the single bearing housing of Comparative Example 37 includes the following steps:

[0392] (1-4) Proceed according to steps (1-4) of Example 1.

[0393] (5) During the transfer of molten iron, a heat-insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is Ca 2.00wt%, Al 0.80wt%, RE 1.70wt%, and the amount added is 0.15wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Comparative Example 37 is obtained by pouring.

[0394] Comparative Example 38

[0395] The method for preparing the single bearing housing of Comparative Example 38 includes the following steps:

[0396] (1-4) Proceed according to steps (1-4) of Example 1.

[0397] (5) During the transfer of molten iron, a heat-insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is Ca 2.00wt%, Al 0.80wt%, RE 1.70wt%, and the amount added is 0.20wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Comparative Example 38 is obtained by pouring.

[0398] Comparative Example 39

[0399] The method for preparing the single bearing housing of Comparative Example 39 includes the following steps:

[0400] (1-4) Proceed according to steps (1-4) of Example 1.

[0401] (5) During the transfer of molten iron, a heat-insulating covering agent is applied to the surface of the molten iron. A low-silicon-sulfur-oxygen inoculant is used for in-flow inoculation. The composition of the low-silicon-sulfur-oxygen inoculant is Ca 2.00wt%, Al 0.80wt%, RE 1.70wt%, and the amount added is 0.25wt% of the weight of the molten iron. The total time for lifting, transferring and pouring the molten iron is controlled within 11 minutes, and the pouring temperature is 1350℃. The single bearing seat of Comparative Example 39 is obtained by pouring.

[0402] Comparative Example 40

[0403] The method for preparing the single bearing housing of Comparative Example 40 includes the following steps:

[0404] (1-3) Proceed according to step (1-3) of Example 1.

[0405] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 70wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 30wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.13wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 0.30wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium-barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium-barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0406] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 40 was obtained by casting.

[0407] Comparative Example 41

[0408] The method for preparing the single bearing housing of Comparative Example 41 includes the following steps:

[0409] (1-3) Proceed according to step (1-3) of Example 1.

[0410] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 80wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 20wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.10wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 0.30wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0411] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 41 was obtained by casting.

[0412] Comparative Example 42

[0413] The method for preparing the single bearing housing of Comparative Example 42 includes the following steps:

[0414] (1-3) Proceed according to step (1-3) of Example 1.

[0415] (4) The molten iron obtained in step (3) is subjected to spheroidizing treatment by the pouring method. The spheroidizing agent is a mixture of spheroidizing agent A and spheroidizing agent B, wherein spheroidizing agent A accounts for 85wt% of the total weight of the spheroidizing agent, spheroidizing agent B accounts for 15wt% of the total weight of the spheroidizing agent, and the total amount of spheroidizing agent added is 1.09wt% of the weight of the molten iron. The composition of spheroidizing agent A is Al 0.90wt%, Ca 0.30wt%, Mg 5.80wt%; the composition of spheroidizing agent B is Al 0.40wt%, Ca 0.60wt%, Mg 4.55wt%. A low-silicon calcium-barium inoculant of 0.30wt% of the weight of the molten iron is covered on the spheroidizing agent, wherein the composition of the low-silicon calcium-barium inoculant is Ba 1.85wt%, Ca 0.50wt%, Al 0.65wt%; then a silicon steel sheet of 0.50wt% of the weight of the molten iron is covered on the inoculant, and antimony of 0.004wt% of the weight of the molten iron is added on the silicon steel sheet. When tapping the molten iron, flush it to the other side of the spheroidizing alloy. The tapping time should be controlled at 60 seconds, and the magnesia explosion time should be controlled at 155 seconds. After the spheroidizing reaction is complete, remove the spheroidizing slag until there is no visible slag on the surface of the molten iron.

[0416] (5) Following step (5) of Example 1, the single bearing housing of Comparative Example 42 was obtained by casting.

[0417] The single bearing housings prepared in Examples 1-25 and Comparative Examples 1-42 were subjected to linear inclusion defect detection and magnetic particle testing. The results are shown in Tables 4, 5, and 6. The test methods are as follows:

[0418] (1) Linear inclusion depth detection

[0419] The surface of the cast single bearing housing is polished layer by layer, and the surface is subjected to MT test at each polishing depth to observe the display of linear inclusion defects; the range of polishing depth before the linear inclusion defects disappear is recorded, and this range of depth is used to characterize the linear inclusion depth of the single bearing housing.

[0420] (2) Metallographic observation

[0421] Metallographic observation was performed on the single bearing housing sample to verify whether there were interface defects such as sulfur infiltration in the near-surface area of ​​the casting.

[0422] Table 4. Results of linear inclusion depth detection in Examples 1-25 and Comparative Examples 1-42

[0423]

[0424] Table 5. Results of linear inclusion depth detection in Comparative Examples 1-21

[0425]

[0426] Table 6. Results of linear inclusion depth detection in Comparative Examples 22-42

[0427]

[0428] As shown in Tables 4-6, under the process system of this invention, the linear inclusion depth of the single bearing housing is generally well controlled. In Examples 1-25, the linear inclusion depth of most samples is controlled within the range of 3-7 mm, and some samples can be further reduced to 2-6 mm, 2-4 mm, or even 1-3 mm. This indicates that the present invention, through the synergistic effect of comprehensive control of the spheroidizing agent composition, inoculation control, mold interface blocking, and low humidity control, can effectively reduce near-surface linear inclusion defects. Among these, Example 18 shows the best results, with a linear inclusion depth of 1-3 mm. Combined with... Figures 2-5 It can be seen that the linear inclusion defects in the planar MT at different grinding depths in Example 18 gradually decrease with the increase of grinding depth, and the metallographic structure shows that there are no sulfur penetration defects in the near-surface area of ​​the casting. This indicates that the process of the present invention can not only effectively reduce linear inclusion defects, but also inhibit the penetration of sulfur from the mold interface into the near-surface layer of the casting.

[0429] Comparative examples 18-25 and 17 and 18 show that as the mold humidity before casting gradually increases from 18%RH to 35%RH, the depth of linear inclusions in the casting generally increases. Specifically, the depth is 1-3 mm at 18%RH, increases to 3-7 mm at 25%RH, and further increases to 3-9 mm and 3-12 mm at 30%RH and 35%RH, respectively. This indicates that mold humidity is a significant factor affecting linear inclusion defects. Higher humidity introduces more oxygen and reaction media from the molding sand and moisture, making it easier for magnesium, aluminum, and calcium oxides, sulfides, and complex inclusions in the molten iron to accumulate near the surface, thus exacerbating linear inclusion defects.

[0430] Comparing Example 1 with Comparative Examples 19-24 reveals that the type of coating, Baumé degree, and coating sequence significantly affect the slag-prevention effect and the feasibility of the process. When using ordinary coatings, the slag depth in the trial production was approximately 5-12 mm, significantly higher than the results obtained by applying the special functional coating according to the process in Example 1. When using special functional coatings but with incorrect Baumé degree, sagging, blistering, or coating peeling easily occur during the trial production process, failing to meet the usage requirements. When using special functional coatings but changing the coating sequence, the first coat of graphite coating has a high viscosity, leading to poor adhesion of the subsequent two coats and making it prone to blistering and peeling; the first coat of anti-sulfur coating, due to its lower refractoriness than zircon powder coating, easily causes sand adhesion to the casting. This indicates that although mold surface treatment is not the only key point of this invention, it plays a crucial role in the stable implementation of the process. To obtain a good slag-prevention effect, the type of coating, Baumé degree, and coating sequence must be strictly followed according to Example 1.

[0431] By comparing Examples 1, 10, and 11 with Comparative Example 1, it can be seen that the key to this invention is not the fixed form of mixing spheroidizing agent A and spheroidizing agent B, but whether the spheroidizing agent's overall Mg, Ca, and Al content is controlled within a suitable range. When using spheroidizing agent A alone, the linear inclusion depth increases to 5-9 mm, indicating that using spheroidizing agent A alone with higher Ca and Al levels is not conducive to inclusion control. However, when using spheroidizing agent B alone, the linear inclusion depth can be controlled between 3-6 mm and 3-7 mm. When using a single spheroidizing agent corresponding to the overall composition after mixing A and B, the linear inclusion depth can also be controlled between 2-6 mm and 3-7 mm. This shows that as long as the spheroidizing agent's overall Mg, Ca, and Al content meets the appropriate requirements, a good slag prevention effect can be obtained regardless of whether spheroidizing agent B is used alone or a single spheroidizing agent is used. On the other hand, the experimental results also show that although spheroidizing agent B can achieve a good slag-prevention effect, its addition ratio is significantly increased, requiring higher-quality low-aluminum and low-calcium raw materials, resulting in a significant increase in cost. While a single spheroidizing agent can also achieve a good slag-prevention effect, the cost of developing new spheroidizing agent grades is also high. Therefore, using a mixture of spheroidizing agents A and B is more beneficial in balancing slag-prevention effect and cost.

[0432] By comparing Example 1 with Comparative Examples 2-7, it can be seen that when the Ca or Al content in spheroidizing agent A increases, the depth of linear inclusions in the castings increases significantly. Specifically, when the Ca content in spheroidizing agent A is increased to 1.5 wt%, the slag depth increases to 5-12 mm, 6-11 mm, and 7-11 mm; when the Al content in spheroidizing agent A is increased to 2.0 wt%, the slag depth increases to 5-12 mm, 6-13 mm, and 7-14 mm. This indicates that when the Ca and Al content in spheroidizing agent A is too high, it will significantly increase the tendency for the formation of related oxides, sulfides, and complex inclusions, which is not conducive to the control of linear inclusions.

[0433] Comparing Example 1 with Comparative Examples 40-42, it can be seen that when the Ca content in spheroidizing agent A is further reduced to 0.3 wt%, the linear inclusion depth of the casting can be controlled between 2-6 mm and 3-6 mm, and the surface still exhibits a good slag-prevention effect. However, the experimental results also show that the magnesium explosion is more severe than usual at this point, the magnesium residual value is lower, and there is a potential risk of spheroidization degradation. This indicates that the Ca content in spheroidizing agent A is not necessarily better the lower it is; rather, it is necessary to consider both the inclusion depth and the stability of the spheroidization reaction and the safety of subsequent processes.

[0434] Comparing Example 1 with Comparative Examples 8-10, it can be seen that when the Al content in spheroidizing agent A is reduced to 0.1 wt%, the linear inclusion depth in the castings actually increases to 3-8 mm, 3-9 mm, and 2-11 mm, respectively. This indicates that excessively low Al content is also detrimental to linear inclusion control. When the aluminum content is reduced too much, the oxygen and silicon complexes in the molten iron during spheroidization will further consume magnesium, forming inclusions, and some of these inclusions will form silicate inclusions that enter the casting.

[0435] Comparing Example 1 with Comparative Examples 11-16 reveals that the Ca and Al content in the B spheroidizing agent also exhibits a suitable range. When the Ca content in the B spheroidizing agent is increased to 1.2 wt%, the linear inclusion depth in the casting increases to 3-8 mm, 3-10 mm, and 4-8 mm; when the Al content in the B spheroidizing agent is increased to 1.0 wt%, the linear inclusion depth increases to 4-8 mm, 4-9 mm, and 3-9 mm, indicating that higher levels of relevant active elements in the B spheroidizing agent also exacerbate inclusion formation. Furthermore, it shows that while the linear inclusion depth can still be maintained at a low level when the Ca or Al content in the B spheroidizing agent is reduced to 0.2 wt%, further reduction does not bring about significant improvement; instead, it increases raw material requirements and costs, indicating that there is also a reasonable range for Ca and Al content in the B spheroidizing agent that balances effectiveness and cost.

[0436] Comparative studies of Examples 1-3 and Comparative Examples 28-33 show that the composition and dosage of the inoculant in the ladle have a significant impact on linear inclusion defects. When the Ca content in the low-silicon calcium-barium inoculant is increased to 1.2 wt%, the depth of linear inclusions increases to 4-9 mm, 5-9 mm, and 4-10 mm, respectively; when the Ba content is decreased to 0.5 wt%, the depth of linear inclusions increases to 3-9 mm, 4-9 mm, and 4-8 mm, respectively. This indicates that the inoculant in the ladle not only plays an inoculation role but also affects the effective utilization of magnesium and the removal of inclusions. Barium has a stronger reactivity with oxygen and sulfur than calcium and aluminum. After barium participates in the reaction in the ladle inoculant, it is equivalent to protecting magnesium, reducing magnesium reaction consumption, improving the inoculation modification effect, and promoting the precipitation of barium-containing slag in a more easily removable form. However, when the barium content is too low, magnesium consumption increases, inclusions increase, and linear inclusion defects in the casting are aggravated.

[0437] Comparing Examples 1-3 with Comparative Examples 34-39 reveals that controlling the composition of the in-flow inoculant is also crucial. When the Al content in the in-flow inoculant increased to 2.0 wt%, the linear inclusion depth in the castings increased to 3-8 mm, 4-10 mm, and 4-11 mm, respectively; when the Ca content increased to 2.0 wt%, the linear inclusion depth in the castings increased to 3-8 mm, 3-9 mm, and 3-11 mm, indicating that higher levels of relevant active elements in the in-flow inoculant further exacerbate inclusion formation during the casting stage. Inoculation itself is very important for ductile iron. After spheroidizing treatment, the sulfur and oxygen content of the molten iron is significantly reduced, and the number of graphite nuclei decreases. Therefore, it is necessary to combine in-ladle inoculation and in-flow inoculation to both supplement the inoculation effect and slow down its decay.

[0438] When the low-aluminum, low-calcium spheroidizing and inoculating system in Example 1 was replaced with a common spheroidizing agent and a barium silicon inoculant, the inclusions increased by 2-5 mm compared to Example 1, all other conditions being the same. This indicates that simply meeting general spheroidizing and inoculating requirements is insufficient to solve the linear inclusion problem; what truly matters is the synergistic control of key elements such as Mg, Ca, and Al in the spheroidizing agent and inoculant.

[0439] The above results show that linear inclusion defects are not caused by a single factor, nor can they be eliminated by a single measure. Instead, they are related to Mg, Ca, and Al in the spheroidizing agent, Ca, Al, Ba, and RE in the inoculant, as well as sulfur, oxygen, and moisture introduced from the mold interface. This invention addresses this by controlling the spheroidizing agent's Mg, Ca, and Al content within a suitable window, combined with ladle inoculation and in-flow inoculation control, three-layer composite coating blocking, and low-humidity mold control. This synergistically reduces the tendency of magnesium, aluminum, and calcium-related oxides, sulfides, and composite inclusions to accumulate near the surface, thereby stabilizing and mitigating linear inclusion defects in single-unit bearing housings. Figures 2 to 5 It can be further explained that the process of the present invention can not only reduce the depth of linear inclusions, but also reduce the abnormal reaction at the near-surface interface, thus having good process stability and practical application value.

[0440] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for suppressing linear inclusion defects in ductile iron castings, characterized in that, Includes the following steps: (a) A functional composite coating is applied to the inner surface of a resin sand casting mold to obtain a casting mold with a coating barrier; the functional composite coating is composed of a zircon powder coating layer applied to the inner surface of the casting mold, an anti-sulfur coating layer applied to the zircon powder coating layer, and a graphite coating layer applied to the anti-sulfur coating layer. (b) The coated mold is dried with hot air to control the humidity of the mold before pouring to ≤25%RH, so as to obtain a dry mold; (c) The furnace charge is added to an electric furnace for smelting to obtain molten iron; (d) The molten iron obtained in step (c) is subjected to spheroidization treatment by the pouring method to obtain spheroidized inoculated molten iron; The spheroidization treatment is intra-encapsulated spheroidization incubation; The spheroidizing process involves the addition of a spheroidizing agent and a low-silicon calcium-barium inoculant. The spheroidizing agent is a single spheroidizing agent or is composed of two or more spheroidizing agents; when the spheroidizing agent is composed of two or more spheroidizing agents, its Mg, Ca and Al content is calculated as the weighted average of the amount of each spheroidizing agent added; The overall chemical composition of the spheroidizing agent satisfies: Mg 4.2-6.0wt%, Ca 0.35-1.00wt%, Al 0.40-0.90wt%; The chemical composition of the low-silicon calcium-barium inoculant includes: Si 46-50wt%, Ba 1.0-2.0wt%, Ca 0.2-0.6wt%, Al 0.3-0.8wt%, with the balance being Fe; (e) Pour the molten iron obtained in step (d) after spheroidization and inoculation into the dry mold obtained in step (b). During pouring, a low-silicon sulfur-oxygen inoculant is used for in-flow inoculation to obtain ductile iron castings. The chemical composition of the low-silicon-sulfur-oxygen inoculant includes: Si 50-60wt%, Al 0.5-1.0wt%, Ca 0.5-1.0wt%, RE 1.5-2.0wt%, S≤0.50wt%, O≤1.0wt%, with the balance being Fe; The chemical composition of the ductile iron casting is as follows (by mass percentage): Fe 90.0-94.5wt%, C 3.30-3.80wt%, Si 1.80-3.90wt%, Mn≤0.50wt%, P≤0.040wt%, S 0.0050-0.015wt%, Mg 0.035-0.060wt%, RE 0.001-0.010wt%, Ti≤0.030wt%, Cu≤1.0wt%.

2. The method according to claim 1, characterized in that, In step (d), the spheroidizing agent includes spheroidizing agent A and spheroidizing agent B. Spheroidizing agent A accounts for 70-85 wt% of the total weight of the spheroidizing agent, and spheroidizing agent B accounts for 15-30 wt% of the total weight of the spheroidizing agent. The total amount added is 1.00-1.15 wt% of the weight of the molten iron. The chemical composition of spheroidizing agent A includes: Mg 5.55-6.20 wt%, RE 0.30-0.60 wt%, Si 44-48 wt%, Ca 0.35-1.30 wt%, Al 0.40-1.50 wt%, with the balance being Fe. The chemical composition of spheroidizing agent B includes: Mg 4.20-4.90 wt%, RE 0.40-0.60 wt%, Si 44-48 wt%, Ca 0.35-1.00 wt%, Al 0.35-0.80 wt%, with the balance being Fe.

3. The method according to claim 1, characterized in that, In step (d), the spheroidizing agent is a single spheroidizing agent with the following chemical composition: Mg 4.20-4.90wt%, RE 0.40-0.60wt%, Si 44-48wt%, Ca 0.35-1.00wt%, Al 0.35-0.80wt%, with the balance being Fe, and the total amount added is 1.30-1.40wt% of the weight of the molten iron.

4. The method according to claim 1, characterized in that, In step (d), the spheroidizing agent is a single spheroidizing agent with the following chemical composition: Mg 5.55-6.00wt%, RE 0.35-0.55wt%, Si 44-48wt%, Ca 0.35-1.00wt%, Al 0.40-0.90wt%, with the balance being Fe, and the total amount added is 1.00-1.10wt% of the weight of the molten iron.

5. The method according to claim 1, characterized in that, In step (d), the particle size of the low-silicon calcium-barium inoculant is 1-6 mm; the amount of the low-silicon calcium-barium inoculant added is 0.3-0.5 wt% of the weight of the molten iron.

6. The method according to claim 1, characterized in that, In step (e), the particle size of the low-silicon-sulfur-oxygen inoculant is 0.2-0.7 mm; the amount of the low-silicon-sulfur-oxygen inoculant added is 0.15-0.25 wt% of the weight of the molten iron.

7. The method according to claim 1, characterized in that, In step (a), the Baumé degree of the zircon powder coating is controlled at 50-60 Bé, the Baumé degree of the anti-sulfur coating is controlled at 30-40 Bé, and the Baumé degree of the graphite coating is controlled at 35-45 Bé.

8. The method according to claim 1, characterized in that: In step (a), after each layer of coating is applied, it is ignited and burned, and then baked with a blowtorch within 20 seconds after the fire is extinguished; after each layer is applied, wait until the surface temperature of the mold drops below 35°C before applying the next layer of coating; after all coatings are applied, use a blowtorch to bake the mold and core until they are completely dry. And / or, the hot air drying process described in step (b) is as follows: hot air at 80-120°C is introduced into the sprue of the mold for 4-8 hours, and the hot air is turned off at least 30 minutes before tapping the iron; And / or, in step (c), after the molten iron is melted, it is heated to 1480-1500℃ and left to stand for 10-15 minutes to remove the slag and obtain purified molten iron; And / or, in step (c), 80 wt% of the total amount of ferrosilicon is added first during smelting, and the remaining 20 wt% of ferrosilicon is added after removing the slag to adjust the composition; And / or, in step (d), the iron tapping time is controlled within 100 seconds, and the magnesium explosion time is controlled between 120 and 300 seconds; And / or, in step (d), a silicon steel sheet is further coated on the low-silicon calcium-barium inoculant, the coating amount of the silicon steel sheet being 0.5-0.8 wt% of the weight of the molten iron; And / or, in step (d), antimony is added to the low-silicon calcium-barium inoculant, the amount of antimony added being 0.004-0.007 wt% of the weight of the molten iron; And / or, before step (e), the molten iron obtained in step (d) is transferred, and during the transfer process, an insulating covering agent is applied to the surface of the molten iron, and the transfer time is controlled to be 6-15 minutes. And / or, in step (e), the temperature of the molten iron being lifted is 1370-1400℃; And / or, in step (e), the pouring temperature is 1320-1370°C; And / or, in step (e), the molten iron obtained from step (d) after spheroidization inoculation treatment is poured within 20 minutes to obtain ductile iron castings.

9. The method according to claim 1, characterized in that, The linear inclusion depth of the ductile iron casting is ≤8mm.

10. The method according to claim 1, characterized in that, In step (c), the furnace charge comprises, by mass percentage: 60-70 wt% pig iron, 25-30 wt% scrap steel, 5-10 wt% recycled material, 0.9-3.10 wt% ferrosilicon, and 0.35-1.0 wt% carbon raiser; The chemical composition of the scrap steel meets the following requirements: C≤0.30wt%, Si≤0.60wt%, Mn≤0.80wt%, P≤0.030wt%, S≤0.020wt%, Ti≤0.030wt%, Cr≤0.040wt%. The chemical composition of the pig iron meets the following requirements: C ≥ 4.0 wt%, Si 0.3-0.6 wt%, Mn ≤ 0.1 wt%, P ≤ 0.030 wt%, S ≤ 0.02 wt%, Ti ≤ 0.030 wt%, B ≤ 0.009 wt%. The chemical composition of the recycled material meets the following requirements: C 3.6-3.8wt%, Si 1.90-2.20wt%, Mn≤0.20wt%, P≤0.030wt%, S≤0.015wt%, Mg 0.035-0.060wt%, RE≤0.010wt%, Ti≤0.030wt%. The chemical composition of the ferrosilicon satisfies: Si 72-80wt%, Al≤1.20wt%, Mn≤0.50wt%, Cr≤0.50wt%. The chemical composition of the carbon raiser meets the following requirements: C ≥ 99.0 wt%, S ≤ 0.040 wt%, H ≤ 0.010 wt%, N ≤ 0.010 wt%, ash ≤ 0.40 wt%, volatile matter ≤ 0.50 wt%, and moisture ≤ 0.50 wt%.

Images