Casting system suitable for vertical line automobile brake part, pouring process and casting

Abstract

The invention discloses a casting system suitable for a vertical line automobile brake part, a pouring process and a casting, and belongs to the technical field of pouring. The pouring system comprises a pouring cup; the dead head is positioned below the sprue cup; the pouring gate comprises a transverse pouring gate and a vertical pouring gate, the transverse pouring gate comprises a first transverse pouring gate connected with the pouring cup, a second transverse pouring gate connected with the upper riser and a third transverse pouring gate located at the bottom of the pouring system; the vertical pouring gate is used for connecting the first transverse pouring gate, the second transverse pouring gate and the third transverse pouring gate; a side water inlet is formed in the side edge of the cavity, and the cavity is connected with the vertical pouring gate through the side water inlet; a bottom water inlet is formed below the cavity, and the cavity is connected with the third cross gate through the bottom water inlet. By regulating and controlling parameters and pouring speed of a pouring system and adopting bottom pouring, side pouring and top auxiliary pouring, the appearance of the product is guaranteed, slag inclusion defects such as cold shut, sand holes and air holes are avoided, the product is free of shrinkage porosity or small in shrinkage porosity area, and the product is high in internal quality and high in mechanical performance.

Description

Technical Field

[0001] The invention belongs to the technical field of casting, and more specifically, relates to a casting system, a casting process and a casting suitable for a vertical line automobile brake part. Background Art

[0002] The caliper in the brake system is one of the key components of automobile safety, such as Figure 1 It is an open-type 22.5-inch brake caliper made of QT600-3. It requires no shrinkage in the processing area, and no defects such as sand holes and shrinkage holes on the surface of the casting blank. It has high mechanical property requirements and its structural feature is a complex structure thin-walled casting.

[0003] The general process improves the casting surface by controlling the relevant parameters of the molding sand, and adds risers at the top and both sides to improve internal shrinkage. However, the disadvantage is that the shrinkage tendency of other hot spots except the top is large, and the gate has external shrinkage holes, which leads to unqualified tensile strength of the casting, and sand holes are easily generated on the surface of the casting, which cannot meet the use requirements. Although the traditional process can control casting defects to a certain extent, its adaptability to castings with complex geometric structures and thin-walled features is limited, especially in the vertical line production process, the internal quality and mechanical properties of the castings are more stringent.

[0004] After searching, patent CN214079121U discloses a double-layer filtering pouring device, including a pouring cup, an upper runner extending from the lower end of the pouring cup to both sides, a straight runner extending downward from both ends of the upper runner, and a lower runner installed below the straight runner and connected to the two straight runners at the same time; an upper filter is provided inside the connection between the straight runner and the upper runner, and a lower filter is provided inside the connection between the straight runner and the lower runner. The slag retaining capacity is enhanced by providing an upper and lower filter to purify the molten metal, and the design position is placed directly below the straight runner with a large drop, which greatly reduces the scouring effect of the molten metal on the casting. However, the patent adopts the method of placing the filter alone below the pouring system, which cannot be applied to vertical processes with limited space.

[0005] Patent CN113680958A discloses a vertically parted pouring system and pouring process for a crankshaft, the pouring system includes a horizontal runner, three vertical runners connected to the lower part of the horizontal runner, a pressure edge symmetrically connected to the periphery of the vertical runner, a thin sheet connected to the lower part of the vertical runner, a vertical crank connected to one end of the thin sheet and connected to the pressure edge, a straight pouring runner reversely overlapped at the lower part of the pressure edge located in the middle of the three pressure edges, and a horizontal crank connected to both ends of the straight pouring runner. The invention places the vertical crank vertically, and water is introduced from the pressure edge and the thin sheet, which increases the water flow rate when entering the water and speeds up the pouring speed of the vertical crank; the thin sheet can filter impurities in the molten iron, and the pressure edge is convenient for decompressing the upward molten iron, slowing down the pouring speed, and reducing the sand flushing of the vertical crank, but the patent is aimed at small-sized castings. Compared with large-sized castings, small-sized castings are easier to maintain temperature uniformity during the pouring process.

[0006] Therefore, for large-sized vertical line automobile brake parts, how to ensure temperature uniformity during the casting process is an urgent problem to be solved. Summary of the invention

[0007] 1. Problem to be solved

[0008] Aiming at the problem that uneven temperature leads to many casting defects during the casting process of existing large-size vertical line automobile brake parts, the present invention provides a casting system and casting process suitable for vertical line automobile brake parts, which improves the temperature uniformity during the casting process, and the obtained castings have fewer defects and high product quality.

[0009] 2. Technical solution

[0010] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] The first object of the present invention is to provide a casting system suitable for large-sized vertical line automobile brake parts, and the large-sized vertical line automobile brake parts particularly refer to automobile brake parts with a size of 17.5 inches to 22.5 inches, such as calipers, brackets, etc. Since large-sized automobile brake parts need to be injected with more casting liquid during the casting process, how to ensure the temperature uniformity of the casting liquid is an urgent problem to be solved, so the casting system of the present invention includes:

[0012] Pouring cup: used to inject liquid metal;

[0013] Riser: Located below the pouring cup, it feeds the top of the casting;

[0014] Runner: including a horizontal runner and a vertical runner, wherein the horizontal runner includes a first horizontal runner connected to the pouring cup, a second horizontal runner connected to the riser, and a third horizontal runner located at the bottom of the pouring system;

[0015] The vertical runner is used to connect the first horizontal runner, the second horizontal runner and the third horizontal runner;

[0016] Cavity: A side water inlet is provided on the side of the cavity, and is connected to the vertical pouring channel through the side water inlet;

[0017] A bottom water inlet is provided below the cavity and is connected with the third cross runner through the bottom water inlet.

[0018] Also includes:

[0019] A filter slag sheet is provided between the horizontal runner and the vertical runner; a filter slag sheet is provided between the vertical runner and the side water inlet, the filter slag sheets of the horizontal runner and the vertical runner preliminarily filter the loose sand and slag in the molten iron, and the filter slag sheet between the vertical runner and the side water inlet secondarily filters the loose sand and slag in the molten iron.

[0020] Among them, the pouring channels of the side water inlet and the bottom water inlet are made of 3mm thick thin sheets to speed up the pouring speed. They not only serve as the bottom water inlet but also serve as the third filter to prevent loose sand and slag in the molten iron from entering the mold cavity.

[0021] Furthermore, the vertical pouring channel is provided with a flow-blocking overlap for regulating the pouring speed.

[0022] The design of the gating system will directly affect the quality of the casting. About 30% of the scrap castings are caused by unreasonable gating system design. Therefore, the requirements for the gating system design of castings must meet the following requirements:

[0023] 1) Determine the parameters of the gate in the gating system according to the solidification principle of the casting;

[0024] 2) The metal liquid flows smoothly during the filling process to avoid turbulence during the flow process, and prevent the metal liquid from being drawn into the gas, causing oxidation or generating pores;

[0025] 3) When the molten metal enters the cavity from the ingate, the tangential velocity during inflow should not be too large, otherwise it will cause splashing, scouring the inner wall of the cavity and the sand core;

[0026] 4) The pouring system should not be too large, which may cause waste and reduce the output rate. At the same time, it is necessary to fill the cavity within the specified time to avoid the local temperature drop caused by the slow rise of the metal liquid level, thereby forming defects such as sand inclusion scars and cold shuts.

[0027] 5) The pouring system is simple and easy to make, reducing the volume of the sand box.

[0028] Another object of the present invention is to use the above-mentioned pouring system to cast a vertical line automobile brake part. The process adopts a bottom pouring plus side and top auxiliary pouring process, and its specific steps include:

[0029] a) Smelting: 500-1000kg of pig iron, 2400-3000kg of scrap steel and 2400-3500kg of recycled materials are heated and melted at a temperature of 1500-1580°C for 0.5-1h. The obtained molten iron contains the following components: C 3.7%-3.9%; Si 1.6%-1.8%; Mn 0.3%-0.4%; S<0.015%; P<0.05%; Cr<0.1%; Sb<0.01%; Cu 0.2%-0.35%; Sn 0.03%-0.035%, and the rest is Fe and unavoidable impurities.

[0030] b) Spheroidization: the molten iron in front of the furnace enters a pit-type treatment bag, is spheroidized by adding a spheroidizing agent, and is covered with iron sheets. The spheroidizing agent uses an alloy spheroidizing agent with a Mg content of less than 15%, and is spheroidized by a pit-type flushing method, so that the composition of the molten iron after the furnace is C3.7%-3.8%; Si 2.2%-2.3%; Mn 0.3%-0.4%; S<0.015%; P<0.05%, Cr<0.1%, Mg0.04%-0.05%, Sb<0.01%, Cu 0.20%-0.35%, Sn 0.03%-0.035%, and the rest is Fe and unavoidable impurities.

[0031] c) Pouring: After spheroidization, inoculant is added and pouring is carried out. During the pouring process, inoculation is carried out. The pouring liquid is injected into the cavity from the bottom water inlet, the side water inlet and the riser respectively. The pouring temperature is 1380-1450℃ and the pouring time is 10-11 seconds. The casting is unpacked after cooling in the cavity for 60-65 minutes.

[0032] The inoculant is a high rare earth inoculant, and its components include Si 65%-75%, Al 0.5%-1.5%, Ca 0.5%-1.5%, Ce 1%-2.5%, and the rest is Fe and inevitable impurities.

[0033] The braking system is one of the core components of automobile safety. Its castings must meet strict mechanical performance standards and adapt to changing usage environments. Therefore, optimization of the casting production process is crucial to improving the overall performance and braking response of the vehicle.

[0034] In view of the fact that the brake system castings, especially the calipers, have complex geometric structures, thin wall thicknesses and large sizes, especially the thinnest wall thickness is on both sides, which is 8-15mm. During the pouring process, the thinner the wall thickness is, the faster the cooling rate will be over time. Therefore, the present invention designs and plans the layout of the pouring system based on these characteristics to ensure that the molten metal can evenly fill the mold cavity and improve the temperature uniformity, thereby effectively preventing the occurrence of casting defects such as cold shuts and pores. The performance of the casting is affected by the pouring system and process, material, pouring temperature and cooling rate, and the above factors affect the temperature uniformity of the casting during the pouring process.

[0035] Among them, uneven temperature has the following effects on castings: there are hot spots in the casting structure. The hot spots occur near the pouring channel, the root of the riser or the thick part of the product. The heat dissipates slowly or is concentrated at a certain point. The outer layer of the molten iron has solidified, but the hot node is still in liquid state. The solidified layer gradually forms dendrites and continues to grow to divide the remaining molten iron into several different molten pools. As the temperature decreases, the hot spot begins to shrink and the volume decreases. At this time, the molten iron cannot be replenished, and the pore wall after solidification is rough and filled with loose pores of dendrites, forming a large number of dispersed shrinkage cavities.

[0036] In addition, when the pouring temperature is too low, the inclusions in the molten iron cannot float to the surface, causing the inclusions to be wrapped in the casting, forming defects and affecting the performance of the casting.

[0037] The consistency of the casting structure is critical to the performance of the casting. Uneven microstructures may lead to local changes in performance and affect overall performance. In order to improve the temperature uniformity during the pouring process, this application improves the pouring process in the following aspects:

[0038] (1) Casting system and process:

[0039] Since the high-temperature molten iron cools rapidly in the pouring system, the temperature distribution of the molten iron in the pouring channel is uneven. In order to improve the uniformity of the molten iron temperature, this application adopts a composite pouring system of bottom pouring plus side and top auxiliary pouring. At the same time, considering the influence of the pouring system on the filling speed, in order to prevent sand hole defects caused by unreasonable pouring speed and angle, this application controls the structural parameters of the pouring system, controls the pouring speed, and adopts the bottom pouring + side + top auxiliary method to pour smoothly, and the sand hole defect rate is lower. The filling speed is regulated by controlling the cross-sectional area flow rate. The calculation formula of the cross-sectional area in this application satisfies:

[0040]

[0041] Wherein, F is the cross-sectional area, K is a constant, which covers the gravitational acceleration and the density of the pouring liquid at 1400°C. When the pouring liquid is molten iron, K is 1036; G is the total weight of metal flowing through the cross section F during the entire pouring process; t is the pouring time. The present invention controls the pouring time to be 10-11 seconds. G / t is the weight of metal passing through the cross section of the pouring system within t time, that is, the flow rate, and m is the loss coefficient; H is the metal static height, that is, the height from the upper surface of the metal in the pouring cup to the pressurized cross section.

[0042] The loss coefficient m describes the overall reduction effect on the speed or flow rate of the metal in the pouring system, and the value is between 0 and 1. In the present invention, m is controlled to be 0.45-0.6, which is obtained from experience, wherein m is affected by the metal flow energy and metal speed, and the metal speed mainly depends on the metal type, pouring temperature and metal composition. Therefore, the present application combines the metal type, pouring temperature and metal composition to adjust the m value, and finally determines that the value range of m is 0.45-0.6.

[0043] Further homogenize the temperature field during the pouring process, combine bottom pouring, side and top auxiliary pouring to form a multi-directional flow pattern, improve the filling efficiency of the molten metal, and reduce the risk of casting cold shut defects. This multi-directional pouring strategy not only optimizes the flow characteristics of the molten metal, controls the filling speed by controlling the cross-sectional flow rate, avoids turbulence and air holes caused by too fast flow of molten metal, and reduces the impact on the mold wall to reduce the occurrence of sand holes and sand washing, but also helps to reduce problems such as cold shut caused by excessive temperature gradients.

[0044] Composite casting technology:

[0045] During the pouring process, the molten iron enters the pouring cup and then transfers to the first horizontal runner. After being filtered by the first filter residue sheet, the pure molten iron enters the vertical runner. The molten iron passes through the flow-blocking overlap and the speed is slowed down as it continues to flow downward. After reaching the bottom, it flows into the third horizontal runner at the bottom through the filter residue sheet for a second filtration. Subsequently, it enters the casting cavity first after being filtered for a third time through the 3mm thick water inlet at the bottom. When 1 / 5-1 / 3 of the water is injected from the bottom, the molten iron filtered through the measured water inlet enters the cavity. Finally, when the cavity is filled with 2 / 3-4 / 5 of the molten iron, it flows into the riser from the second horizontal runner, forming a simultaneous water filling of the bottom + side + top, and finally the casting is poured.

[0046] (2) Pouring temperature and cooling rate

[0047] The present application controls the pouring temperature at 1380-1450℃, the temperature of the molten iron out of the furnace is 1500~1550℃, and after the transfer temperature loss, the temperature of the molten iron at the entrance is 1380-1450℃, and flows into the pouring channel. The cooling rate affects the solid phase temperature, and the pouring temperature and solid phase temperature have a significant impact on the organizational structure of the casting and the performance of the final product, which is mainly manifested in the following aspects:

[0048] Pouring temperature, that is, the liquid temperature of molten iron: the pouring temperature affects the fluidity and filling capacity of the molten metal. Too high a pouring temperature may cause shrinkage defects in the casting and the risk of sand sticking to the surface of the casting. If the pouring temperature is too low, the fluidity of the molten metal will decrease, which may cause the formation of pores, slag inclusions, incomplete filling, cold shut and other defects in the casting. Therefore, this application controls the casting temperature at 1380-1450℃.

[0049] Cooling rate: The cooling rate determines the shape and size of graphite nodules and the formation of matrix structure. A slower cooling rate promotes the formation of large-sized graphite nodules and the development of ferrite, while rapid cooling may increase the formation of pearlite. Too fast or too slow cooling may lead to irregular graphite morphology. Therefore, the present application controls the cooling rate of molten iron during the casting process to promote the formation of graphite nodules. After the cavity is finally filled with pouring liquid, the unpacking cooling method is adopted. The cooling time is 60-65 minutes, and the unpacking temperature is 450-600℃.

[0050] Eutectic transformation temperature: When cast iron is close to the eutectic transformation temperature of 1148℃, carbon precipitates in the form of spheroidal graphite to form the typical structure of ductile iron. Therefore, controlling the temperature during the pouring process to meet the eutectic transformation temperature is crucial to obtain a high spheroidization rate. At this temperature, carbon precipitates in the form of spheroidal graphite, and the size of the spheroidal graphite formed is 5 to 8, and the spheroidization rate is greater than 80%. At the same time, by improving the temperature uniformity so that the temperature during the pouring process meets the eutectic transformation temperature, it is possible to avoid the coarse grains caused by the high local casting temperature, resulting in uneven particle size distribution in the material, uneven stress distribution, and affecting the mechanical properties of the material.

[0051] During the rapid cooling process, the alloying elements chromium (Cr) and manganese (Mn) in the molten iron can form carbides with carbon. The presence of these carbides will affect the hardness and toughness of the material. The present application controls the content of the alloying elements within a lower range, preferably, controls the total content of chromium (Cr) and manganese (Mn) to 0.4%≤Cr+Mn≤0.5%, to avoid the formation of carbides that reduce the graphite formation nuclei and lead to poor spheroidization of graphite.

[0052] This will form a casting with uniform structure, avoiding uneven internal structure of the casting caused by uneven temperature, generating thermal stress, causing deformation or cracking.

[0053] (3) Filling speed

[0054] During the pouring process, special attention is paid to controlling the filling speed. This application controls the size of the pouring system so that the instantaneous speed of each point in the casting is controlled below 1.2m / s, avoiding turbulence and pores caused by too fast flow of molten metal, while reducing the impact on the mold wall to reduce the occurrence of sand holes and sand flushing. The pouring speed is regulated by controlling the overlap area, and the optimal water entry time is determined in combination with the fluidity of the alloy and the wall thickness of the casting. The optimal water entry time is controlled to be 10-11 seconds to ensure smooth filling of the molten metal.

[0055] Among them, the adjustment of the filling speed is based on the design of the pouring system on the one hand. Based on the geometric complexity and dimensional parameters of the casting, an optimized pouring system is designed, including gates, runners, ingates and risers, to achieve balanced distribution and flow of the molten metal. By adjusting the structural parameters of the pouring system, such as the cross-sectional area and length of the runner overlap, the filling speed is precisely controlled to meet the fluidity requirements of the molten metal; on the other hand, the composition of the molten metal is controlled, the temperature uniformity is improved, and the temperature field is homogenized to ensure that the pouring system design can achieve uniform distribution of the temperature field.

[0056] (4) Material

[0057] The present application adopts QT600-3 alloy as the raw material of the casting, which includes the following components in mass percentage: C 3.7%-3.8%; Si 2.2%-2.3%; Mn 0.3%-0.4%; S<0.015%; P<0.05%, Cr<0.1%, Mg 0.04%-0.05%, Sb<0.01%, Cu 0.20%-0.35%, Sn 0.03%-0.035%, and obtains the best microstructure and mechanical properties by optimizing key process parameters such as pouring temperature, cooling rate, and top shrinkage feeding.

[0058] It makes the pouring liquid have good fluidity while ensuring the mechanical properties of the casting.

[0059] Therefore, the present application improves the uniformity of temperature distribution during the pouring process by optimizing key process parameters such as pouring temperature, cooling rate, and top shrinkage compensation, so as to obtain the best microstructure and mechanical properties.

[0060] In the castings, the graphite size is 5 to 8, the spheroidization rate is greater than 80%; 45% ≤ pearlite ≤ 95%, cementite <

[0061] 3%, internal casting defects meet the following requirements: no defects in metallographic and tensile sampling areas, and the defect level in other parts does not exceed level 2.

[0062] Mechanical properties: tensile strength Rm (N / mm 2 )≥600MPa, elongation A≥3%.

[0063] Hardness (cross section): 190-270 HBW.

[0064] The graphite in the casting is spherical graphite of grade 5 to 8: the size of graphite particles will affect the microstructure of cast iron, and smaller graphite particles usually provide better mechanical properties; spherical graphite can better absorb impact energy and improve the toughness of the casting due to its spherical structure.

[0065] Spheroidization rate > 80%: Spheroidization rate refers to the proportion of spheroidal graphite in cast iron. High spheroidization rate is usually associated with better toughness and ductility.

[0066] Metallographic structure: 45% ≤ pearlite ≤ 95%, cementite < 3%, and the rest is ferrite. The composition of the metallographic structure directly affects the hardness, strength and toughness of the material. Cast iron containing a higher proportion of pearlite usually has higher strength and hardness, but if the pearlite content is too high, the toughness is lower. Therefore, this application controls the metallographic structure to be 45% ≤ pearlite ≤ 95%.

[0067] The final performance of the casting is improved by regulating the size and shape of graphite, the spheroidization rate and the metallographic structure. Spheroidal graphite can absorb and disperse stress more effectively, thereby improving the impact strength of the material; the pearlite in the metallographic structure improves the strength of the casting; the fine graphite particles and pearlite help to improve the hardness of the casting; the pearlite with higher hardness and the fine graphite particles help to improve the wear resistance of the casting.

[0068] The casting system and process of the present application are suitable for vertical line automobile brake parts, especially for large-sized brake parts, such as common brake parts such as brackets, calipers, etc.

[0069] 3. Beneficial effects

[0070] Compared with the prior art, the present invention has the following beneficial effects:

[0071] (1) The pouring system of the present invention connects the bottom water inlet, the side water inlet and the riser to the mold cavity, so as to realize the bottom pouring + side pouring + top auxiliary pouring into the mold cavity respectively, thereby improving the temperature uniformity of the molten iron in the pouring system;

[0072] (2) The pouring system of the present invention avoids turbulence and pores caused by excessively fast flow of molten metal by designing the parameters of the pouring system, and reduces the impact on the mold wall, thereby reducing the occurrence of sand holes and sand flushing;

[0073] (3) The pouring process of the present invention adopts a bottom pouring + side pouring + top auxiliary pouring process, by injecting molten iron into the mold cavity from the bottom water inlet, the side water inlet and the riser respectively, thereby improving the temperature uniformity of the molten iron in the pouring system;

[0074] (4) The pouring process of the present invention improves the uniformity of temperature distribution during the pouring process by optimizing key process parameters such as pouring temperature, cooling rate, and top shrinkage feeding, and improves the final performance of the casting by regulating the size and shape of graphite, spheroidization rate, and metallographic structure;

[0075] (5) The castings produced by the pouring process and pouring system of the present invention have a higher spheroidization rate and a higher proportion of pearlite, which helps to improve the hardness and mechanical properties of the castings. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but it should be understood that these drawings are designed only for explanation purposes and are not intended to limit the scope of the present invention. In addition, unless otherwise specified, these drawings are intended only to conceptually illustrate the structural configurations described herein and are not necessarily drawn to scale.

[0077] Figure 1 It is a structural diagram of the pouring system of the present invention;

[0078] Figure 2 The metallographic structure of the casting obtained in Example 1;

[0079] In the figure: 1, pouring cup; 2, riser; 31, horizontal runner; 311, first horizontal runner; 312, second horizontal runner; 313, third horizontal runner; 32, vertical runner; 41, side water inlet; 42, bottom water inlet; 5, filter residue sheet; 6, flow-blocking overlap; 7, cavity. DETAILED DESCRIPTION

[0080] The following detailed description of exemplary embodiments of the present invention refers to the accompanying drawings, which form a part of the description, and in which exemplary embodiments of the present invention that can be implemented are shown as examples. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments can be implemented and various changes can be made to the present invention without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but is only for the purpose of illustrating and not limiting the description of the characteristics and features of the present invention, so as to propose the best mode for performing the present invention and to enable those skilled in the art to implement the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

[0081] It should be understood that the following text is only used to describe one or several specific embodiments of the present invention, and does not strictly limit the scope of protection of the specific claims of the present invention. As used herein, the terms "parallel" and "perpendicular" are not limited to their strict geometric definitions, but include tolerances for reasonable and inconsistent machining or human errors.

[0082] Although traditional processes can control casting defects to a certain extent, they are limited in adaptability to castings with complex geometric structures and thin-walled features. Especially in the vertical line production process, the internal quality and mechanical properties of the castings are more stringent. In response to these challenges, the present invention significantly improves the overall quality of the castings through innovative gating system design and precise process control, effectively controls common defects such as shrinkage, shrinkage holes and surface sand holes in traditional processes, and meets the high standard requirements of automotive brake systems for casting performance.

[0083] At the same time, the vertical DISA line shows significant advantages in the production of caliper castings compared to traditional horizontal casting. Vertical casting technology quickly creates boxless, high-precision vertical parting molds through automated processes, greatly improving production efficiency. In addition, vertical casting technology reduces material waste by reducing scrap rates and improving casting quality.

[0084] Example 1

[0085] A pouring system of Example 1 includes: a pouring cup 1, a riser 2, and a runner, which form a mold cavity 7 of the casting.

[0086] Pouring cup: used to inject liquid metal;

[0087] Riser 2: located below the pouring cup 1, with its opening facing upward, to compensate for the top of the casting;

[0088] Runner 3: includes a horizontal runner 31 and a vertical runner 32, wherein the horizontal runner 31 includes a first horizontal runner 311 connected to the pouring cup 1, a second horizontal runner 312 connected to the riser, and a third horizontal runner 313 located at the bottom of the pouring system;

[0089] The vertical runner 32 is used to connect the first horizontal runner 311, the second horizontal runner 312 and the third horizontal runner 313;

[0090] The side of the cavity 7 is provided with a side water inlet 41, which is connected to the vertical pouring channel 32 through the side water inlet 41;

[0091] A bottom water inlet 42 is provided below the cavity 7 , and is connected to the third runner 313 via the bottom water inlet 42 .

[0092] Also includes:

[0093] A filter residue sheet 5 is provided between the horizontal runner 31 and the vertical runner 32; a filter residue sheet is provided between the vertical runner 32 and the side water inlet 41, the filter residue sheets of the horizontal runner 31 and the vertical runner 32 preliminarily filter the loose sand and slag in the molten iron, and the filter residue sheet between the vertical runner 32 and the side water inlet 41 secondarily filters the loose sand and slag in the molten iron.

[0094] The side water inlet 41 and the bottom water inlet 42 are both made of 3 mm thin sheets, and the vertical pouring channel 32 is provided with a flow-blocking overlap 6 for regulating the pouring speed.

[0095] A casting process suitable for vertical line automobile brake parts, the process steps include:

[0096] a) Smelting: 500 kg of pig iron, 2400 kg of scrap steel and 3400 kg of recycled materials are heated and melted at a temperature of 1550±20°C for 1 hour. The obtained molten iron contains the following components: C 3.7%-3.9%; Si 1.6%-1.8%; Mn 0.3%-0.4%; S<0.015%; P<0.05%; Cr<0.1%; Sb<0.01%; Cu 0.2%-0.35%; Sn 0.03%-0.035%, and the rest is Fe and unavoidable impurities.

[0097] b) Spheroidization: The molten iron in front of the furnace enters the pit-type treatment bag, and the spheroidizer is added for spheroidization and covered with iron sheets. The spheroidizer adopts an alloy spheroidizer with a Mg content of less than 15%, and the spheroidization is carried out by the pit-type flushing method. In Example 1, the spheroidizer is ferrosilicon magnesium, so that the composition of the molten iron after the furnace is C 3.72%; Si 2.25%; Mn 0.35%; S 0.010%; P 0.03%, Cr0.09%, Mg0.043%, Sb<0.01%, Cu 0.32%, Sn 0.031%, and the rest is Fe and unavoidable impurities. Preferably, when the treatment bag is 900kg, the amount of spheroidizer added is 8.1kg.

[0098] c) Pouring: After spheroidization, an inoculant is added, and molten iron is poured. During the pouring process, inoculation is performed, and the pouring liquid is injected into the mold cavity 7 from the bottom water inlet 42, the side water inlet 41 and the riser 2 respectively. The pouring temperature is 1400±20℃, the pouring time is controlled at 10.5 seconds, and the instantaneous speed of each point in the casting is controlled below 1.2m / s. The casting is unpacked after natural cooling in the mold cavity for 60 minutes. The inoculant is a high rare earth inoculant, and its components include Si65%, Al 1.0%, Ca 1.0%, Ce1.5%, and the rest is Fe and unavoidable impurities.

[0099] The structural parameters of the pouring system of Example 1 are:

[0100] The length of the overlap between the vertical runner 32 and the first horizontal runner 311 is 123.49 mm, and the thickness is 3 mm. The product of the length and the thickness is the cross-sectional area.

[0101] Runner 31: The first runner 311 has a width of 25.76 mm and a thickness of 19.5 mm. The product of the width and the thickness is the cross-sectional area.

[0102] The second runner 312 has a width of 14.42 mm and a thickness of 15.9 mm. The length of the overlap is 60.49 mm and the thickness is 3 mm. The product of the length (width) and the thickness is the cross-sectional area.

[0103] The third horizontal runner 313 has a width of 11 mm and a thickness of 12 mm. The length of the third horizontal runner 313 at the joint with the vertical runner 31 is 40 mm and the thickness is 3 mm. The product of the length and the thickness is the cross-sectional area.

[0104] The width of the vertical pouring channel 32 is 17.18 mm and the thickness is 24.4 mm. The product of the width and the thickness is the cross-sectional area;

[0105] The length of the bottom water inlet 42 is 34 mm and the thickness is 3 mm. The product of the length and the thickness is the cross-sectional area.

[0106] The side water inlet 41 has a length of 51 mm and a thickness of 3 mm, and the product of the width and thickness is the cross-sectional area;

[0107] The width of the flow-blocking overlap 6 is 17.18 mm, the length of the upper end is 27 mm, the length of the lower end is 27 mm, and the thickness is 24 mm. The product of the width and the thickness is the cross-sectional area.

[0108] The cross-sectional area and pouring time meet the following conditions:

[0109]

[0110] Wherein, F is the cross-sectional area, K is a constant, covering the gravitational acceleration and the density of the pouring liquid at 1400°C. When the pouring liquid is molten iron, K is 1036; G is the total weight of metal flowing through the cross section F during the entire pouring process; t is the pouring time. In Example 1, the pouring time is controlled to be 10.5 seconds. G / t is the weight of metal passing through the cross section of the pouring system within t time, that is, the flow rate, and m is the loss coefficient; H is the metal static height, that is, the height from the upper surface of the metal in the pouring cup to the pressurized cross section.

[0111] The temperature field during the pouring process is simulated and analyzed to ensure that the pouring system design can achieve a uniform distribution of the temperature field. The simulation results are as follows: Figure 1 As shown, if water is only poured in from the bottom and slowly floats up to fill, the molten iron that enters first will float on the surface for a longer cooling time and at a lower temperature, resulting in a cold shut in appearance, poor shrinkage compensation effect at the top, and a large shrinkage area. However, this application controls the uniformity of the temperature field by adjusting the parameters and pouring speed of the pouring system, using bottom pouring + side pouring + top auxiliary pouring, and the highest temperature is 1430°C at the entrance of the molten steel. As the pouring process progresses, the temperature gradually cools, the lowest temperature is higher than 1148°C, and the temperature difference does not exceed 300°C.

[0112] like Figure 2 As shown in the figure, the average graphite size of the casting is 7, the spheroidization rate is 85%, the pearlite content is 75%, there is no carbide, and the internal casting defects meet the following requirements: no defects in the metallographic and tensile sampling areas, and the defect level of other parts does not exceed 2 levels. Effectively reduce shrinkage, X-ray flaw detection standard every 2500mm2 The area allows shrinkage ≤ 100mm 2 The shrinkage area of ​​one casting of Example 1 is 22 mm 2 .

[0113] Mechanical properties: tensile strength Rm (N / mm 2 ) is 691.4MPa, the yield strength is 473.7MPa, and the elongation A is 9.7%.

[0114] Hardness (cross section): 223-241 HBW.

[0115] The weight of the caliper single type (caliper + pouring channel) obtained by Example 1 is 34.86KG, the pouring channel weighs 13.32KG, the caliper weighs 21.54KG, the yield rate is 61.79%, the shape is more complex, and the wall thickness is thinner. The caliper obtained by this process has fewer defects.

[0116] Example 2

[0117] The caliper produced in Example 2 is 22.5 inches. Its casting process and casting system are the same as those in Example 1, except that the casting temperature is 1430±20°C, the casting time is controlled at 11 seconds, the instantaneous speed of each point in the casting is controlled below 1.2 m / s, and the casting is unpacked after naturally cooling in the mold cavity for 60 minutes.

[0118] The average graphite size of the castings is 7, the spheroidization rate is 82%, the pearlite content is 78%, there is no carbide, and the internal casting defects meet the following requirements: no defects in the metallographic and tensile sampling areas, and the defect level of other parts does not exceed 2 levels. Effectively reduce shrinkage, X-ray flaw detection standard every 2500mm 2 The area allows shrinkage ≤ 100mm 2 The shrinkage area of ​​one casting of Example 2 is 25 mm 2 .

[0119] Mechanical properties: tensile strength Rm (N / mm 2 ) is 675.9MPa, the yield strength is 483.4MPa, and the elongation A is 11.2%.

[0120] Hardness (cross section): 227-246 HBW.

[0121] The weight of the caliper (caliper + pouring channel) obtained by Example 2 is 27.65KG, the pouring channel weighs 10.12KG, the caliper weighs 17.53KG, the yield rate is 63.40%, the shape is more complex, and the wall thickness is thinner. The caliper obtained by this process has fewer defects.

[0122] Example 3

[0123] The caliper produced in Example 3 is 22 inches, and its casting process is the same as that in Example 1, except that the casting temperature is 1425±20°C, the casting time is controlled at 10 seconds, the instantaneous speed of each point in the casting is controlled below 1.2 m / s, and the casting is unpacked after naturally cooling in the mold cavity for 60 minutes.

[0124] The average graphite size of the castings is 7, the spheroidization rate is 82%, the pearlite content is 76%, there is no carbide, and the internal casting defects meet the following requirements: no defects in the metallographic and tensile sampling areas, and the defect level of other parts does not exceed 2 levels. Effectively reduce shrinkage, X-ray flaw detection standard every 2500mm 2 The area allows shrinkage ≤ 100mm 2 The shrinkage area of ​​one casting of Example 3 is 21 mm 2 .

[0125] Mechanical properties: tensile strength Rm (N / mm 2 ) is 700.6MPa, the yield strength is 458.2MPa, and the elongation A is 8.3%.

[0126] Hardness (cross section): 229-252HBW.

[0127] The weight of the caliper (caliper + pouring channel) obtained by Example 3 is 24.98KG, the pouring channel weighs 9.85KG, the caliper weighs 15.13KG, the yield rate is 60.65%, the shape is more complex, and the wall thickness is thinner. The caliper obtained by this process has fewer defects.

[0128] Comparative Example 1

[0129] The comparative example 1 produces a 22.5-inch caliper using a horizontal casting process. The casting system for implementing the process refers to patent CN218224541U. The shell mold and the inner sand core are assembled and then cast. The casting temperature is 1400±20°C, and the casting time is controlled at 12±0.5 seconds. The casting is unpacked after naturally cooling in the mold cavity for 1-1.5 hours.

[0130] Since the present application does not adopt the method of bottom pouring plus side and top auxiliary pouring, the pouring liquid takes longer to enter the pouring channel, and the pouring liquid that enters first takes a long time to cool down, resulting in uneven temperature, cold shut, and more defects.

[0131] The average graphite size of the castings is 5, the spheroidization rate is 60%, the pearlite content is 45%, the carbide content is more than 3%, and the casting is 2500mm 2 Shrinkage area of ​​the area >100mm 2 The caliper prepared by comparative example 1 has more defects, and its mechanical properties and hardness are much lower than those of the castings of examples 1-3.

[0132] Comparative Example 2

[0133] The comparative example 2 produced a 22.5-inch caliper, and its pouring system was the same as that of the embodiment 1. The shell mold and the inner cavity sand core were assembled and then poured. The pouring temperature was 1400±20°C, and the pouring time was controlled at 18±0.5 seconds. The casting was naturally cooled in the cavity for 1-1.5 hours before unpacking.

[0134] This application adopts the method of bottom pouring plus side and top auxiliary pouring, but because the pouring liquid takes too long to enter the pouring channel, the pouring liquid that enters first takes a long time to cool down, resulting in uneven temperature, cold shut, and more defects.

[0135] The average graphite size of the castings is 4, the spheroidization rate is 65%, the pearlite content is 52%, the carbide content is more than 3%, and the casting is 2500mm 2 Shrinkage area of ​​the area >100mm 2 The caliper prepared by comparative example 2 has more defects, and its mechanical properties and hardness are much lower than those of the castings of examples 1-3.

[0136] Comparative Example 3

[0137] The comparative example 3 produces a 22.5-inch caliper, and its pouring system is the same as that of the embodiment 1. The shell mold and the inner cavity sand core are assembled and then poured. The pouring temperature is 1400±20°C, and the pouring time is controlled at 6±0.5 seconds. The casting is unpacked after naturally cooling in the cavity for 1-1.5 hours.

[0138] This application adopts the method of bottom pouring plus side and top auxiliary pouring, but because the pouring liquid enters the pouring channel too quickly, the instantaneous speed in the casting exceeds 1.2m / s, the metal liquid flows too fast, causing turbulence and air holes, and at the same time severely impacts the mold wall, resulting in excessive sand holes and sand flushing.

[0139] The average graphite size of the castings is 5, the spheroidization rate is 68%, the pearlite content is 42%, the carbide content is more than 3%, and the casting is 2500mm 2 Shrinkage area of ​​the area >100mm 2 The caliper prepared by comparative example 3 has more defects, and its mechanical properties and hardness are much lower than those of the castings of examples 1-3.

[0140] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope involved in the present application is not limited to the technical solution formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept, such as a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

[0141] Except for the technical features described in the specification, the remaining technical features are known technologies to those skilled in the art. In order to highlight the innovative features of the present invention, the remaining technical features will not be described here in detail.

Claims

1. A casting system for vertical line automobile brake parts, characterized in that: The pouring system comprises: Pouring cup (1): used for injecting liquid metal; Riser (2): located below the pouring cup (1); The runner comprises a horizontal runner (31) and a vertical runner (32), wherein the horizontal runner (31) comprises a first horizontal runner (311) connected to the pouring cup (1), a second horizontal runner (312) connected to the riser (2), and a third horizontal runner (313) located at the bottom of the pouring system; the vertical runner (31) is used to connect the first horizontal runner (311), the second horizontal runner (312), and the third horizontal runner (313); The mold cavity (7): a side water inlet (41) is provided on the side of the mold cavity (7), and is connected to the vertical pouring channel (31) through the side water inlet (41); A bottom water inlet (42) is provided below the mold cavity (7) and is connected to the third runner (313) via the bottom water inlet (42).

2. The casting system according to claim 1, characterized in that: The runner cross-sectional area satisfies the formula: Where F is the cross-sectional area, K is a constant, G is the total weight of metal flowing through the cross-sectional area F during the entire pouring process; t is the pouring time, G / t is the weight of metal passing through the cross-sectional area of ​​the pouring system within the time t; m is the loss coefficient; and H is the static height of the metal.

3. The casting system according to claim 1, characterized in that: It also comprises a filter residue sheet, wherein a filter residue sheet (5) is provided between the horizontal runner (31) and the vertical runner (32), and a filter residue sheet is provided between the vertical runner (31) and the side water inlet (41).

4. The casting system according to claim 1, characterized in that: The vertical pouring channel (31) is provided with a flow-blocking overlap (6).

5. A process for casting a vertical line automobile brake part using the pouring system according to any one of claims 1 to 4, characterized in that: The bottom pouring plus side and top auxiliary pouring process is adopted, which includes the following steps: The pouring liquid is respectively injected into the mold cavity (7) through the bottom water inlet (42), the side water inlet (41) and the riser (2), the pouring temperature is 1380-1450°C, the pouring time is 10-11 seconds, and the casting is unpacked after cooling in the mold cavity (7) for 60-65 minutes.

6. The casting process according to claim 5, characterized in that: The instantaneous speed of each point in the casting is controlled below 1.2m / s, and the maximum temperature difference does not exceed 300℃.

7. The casting process according to claim 6, characterized in that: The casting liquid contains the following components: C 3.7%-3.8%; Si 2.2%-2.3%; Mn 0.3%-0.4%; S＜0.015％； P<0.05%, Cr<0.1%, Mg 0.04%-0.05%, Sb<0.01%, Cu 0.20%-0.35%, Sn 0.03%-0.035%, and the rest are Fe and unavoidable impurities.

8. A casting obtained by the pouring process according to any one of claims 5 to 7, characterized in that: The casting has no defects in internal metallographic structure and tensile sampling area, and the defect level of other parts does not exceed level 2.

9. The casting according to claim 8, characterized in that The tensile strength Rm (N / mm 2 )≥ 600MPa, elongation A≥3%, hardness: 190-270HBW.

10. The casting according to claim 9, characterized in that In the casting, the graphite size is 5 to 8, the spheroidization rate is greater than 80%, 45%≤pearlite≤95%, cementite<3%, and the rest is ferrite.

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