Nodular cast iron material as well as preparation method and application thereof

Abstract

The invention provides a nodular cast iron material and a preparation method and application thereof. The preparation method of the nodular cast iron material comprises the following steps that S1, a mixture of pig iron, low-manganese waste steel and foundry returns is heated to be completely molten, alloy and auxiliary materials are supplemented and adjusted to target components, and base iron is obtained; s2, a spheroidizing agent is added into the base iron to conduct spheroidizing treatment, ladle-to-ladle inoculation is conducted after spheroidizing treatment, and an efficient inoculant is added during ladle-to-ladle inoculation; s3, pouring is conducted, and during pouring, a long-acting stream inoculant is added for instantaneous inoculation; and S4, carrying out vibration aging treatment to obtain the nodular cast iron material. According to the nodular cast iron material, collaborative upgrading is achieved in the three dimensions of graphite form-matrix strength-thermal stress dissipation, in a bench test, the number of hot cracks is greatly increased, the service life is obviously prolonged, and reliable guarantee is provided for braking safety of heavy vehicles.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cast iron materials, in particular to a spheroidal graphite cast iron material and a preparation method and application thereof. BACKGROUND

[0002] The thermal conductivity of gray iron brake disc is high, which can quickly dissipate the heat generated by the brake disc, reduce the risk of thermal recession, and is widely used in passenger cars and commercial vehicles (such as heavy trucks). The spheroidal graphite brake disc has higher strength and toughness, better wear resistance, and excellent thermal fatigue resistance, and becomes a better choice in the application of modern high-performance, high-safety and long-life brake discs.

[0003] At present, most of the existing technologies improve the strength, toughness, wear resistance and other properties of spheroidal graphite cast iron materials by optimizing the element composition and content in the spheroidal graphite cast iron materials. However, on the one hand, the existing spheroidal graphite cast iron material composition is relatively complex, and more element components are added, and most of them need to add rare earth elements, thereby greatly increasing the material cost; on the other hand, the graphite balls prepared by the existing spheroidal graphite cast iron material production process mostly have defects such as poor roundness and uniformity, large size and morphology, which is not conducive to the obvious improvement of material performance. In addition, the existing spheroidal graphite cast iron material production process needs to heat treat the castings, which not only reduces the production efficiency, but also has a limited improvement range for the thermal cracking resistance of the material.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The purpose of the present application is to provide a spheroidal graphite cast iron material and a preparation method and application thereof, which realizes synergistic upgrading in three dimensions of "graphite morphology-matrix strength-thermal stress dissipation", and greatly improves the thermal cracking resistance of the spheroidal graphite cast iron material.

[0006] The present application provides a preparation method of a spheroidal graphite cast iron material, comprising the following steps:

[0007] S1: heating the mixed materials of pig iron, low-manganese scrap steel and recycled materials to complete melting, adding alloys and auxiliary materials to adjust to the target composition to obtain raw molten iron;

[0008] S2: adding a spheroidizing agent to the raw molten iron for spheroidizing treatment, and then performing tapping and inoculation, and adding a high-efficiency inoculant during tapping;

[0009] S3: performing pouring and adding a long-acting stream inoculant for instantaneous inoculation during pouring;

[0010] S4: performing vibration aging treatment to obtain a spheroidal graphite cast iron material.

[0011] The main indexes of the pig iron in step S1 are as follows: C: 4-5%, Ti: 0.04-0.05%, Si: 0.8-0.9%, Mn: 0.1-0.2%, P: 0.04-0.05%, S: 0.01-0.02%, and the balance of Fe and inevitable impurities.

[0012] The main indexes of the low-manganese scrap steel are as follows: Mn: 0.1-0.2%, P: 0.01-0.03%, S: 0.01-0.02%, Cu: 0.1-0.2%, Ti: 0.01-0.03%, and the balance of Fe and inevitable impurities.

[0013] The main indexes of the recycled material are as follows: C: 3.8-4.2%, Si: 2.2-2.5%, Mn: 0.5-0.9%, Mo: 0.2-0.4%, Cu: 0.4-06%, Ni: 0.3-0.5%, Sn: 0.01-0.03%, Sb: 0.005-0.015%, Mg: 0.035-0.045%, and the balance of Fe and inevitable impurities.

[0014] The use of the pig iron, the low-manganese scrap steel, and the recycled material as the raw materials is beneficial to maximizing the metallurgical quality of the molten iron, and generally strictly controls the contents of harmful elements (S, P), interfering elements (Ti, etc.), and key alloying elements (Mn), thereby ensuring the purity of the material and being beneficial to improving the key performance indicators (such as strength, hot cracking resistance, fatigue life, etc.) of the ductile iron material, and simultaneously reducing the risks (such as spheroidization recession, slag inclusion defects, etc.) in the production process.

[0015] The mass ratio of the pig iron, the low-manganese scrap steel, and the recycled material in the mixture can be (5.5-6.5):(0.8-1.2):(2.5-3.5), for example, 6:1:3.

[0016] Further, a pretreatment agent can be added to the mixture; the pretreatment agent includes silicon carbide, the particle size of the silicon carbide can be 0.5-2mm, and the amount of the pretreatment agent can be 0.8-1.2% of the weight of the mixture. The core role of the pretreatment agent adding silicon carbide is pretreatment activation, carbon and silicon increase, nucleation, and molten iron purification, which is beneficial to obtaining more fine and round graphite balls with more uniform distribution after subsequent spheroidization treatment and ladle inoculation treatment, and is beneficial to making the mechanical properties of the ductile iron material better.

[0017] Preferably, the pretreatment agent comprises the following components by weight percentage: 40-60% of silicon carbide, 20-30% of gray iron, and 10-20% of nodular iron; wherein the weight percentage of each component in the gray iron is as follows: C: 2.6-4.0%, Si: 2.0-2.8%, Mn: 0.5-1.4%, P≤0.3%, S≤0.2%, and the balance of Fe and inevitable impurities; the particle size of the gray iron can be 1-5 mm; the weight percentage of each component in the nodular iron is as follows: C: 3.6-3.9%, Si: 1.1-3.0%, Mn: 0.1-1%, P≤0.05%, S≤0.04%, and the balance of Fe and inevitable impurities; the particle size of the nodular iron can be 2-8 mm. Compared with using single silicon carbide as the pretreatment agent, by adding the gray iron and the nodular iron, the problems of burning loss of the iron liquid, deoxidation and decarburization of the iron liquid can be overcome, the spheroidization rate of the material can be greatly improved, the inoculation effect of the inoculant can be ensured, and the comprehensive performance of the graphite cast iron material can be greatly improved.

[0018] When the mixture is heated to be melted, the heating temperature can be controlled to be 1420-1480°C, and the heating can be stopped until the mixture is completely melted. After the iron liquid is completely melted, the slag inhibitor is added and stirred, and then the slag is removed. The composition of the iron liquid is detected by a carbon-silicon analyzer and a direct-reading spectrometer, and the alloy and the auxiliary material are added according to the detection result to adjust the target composition. Specifically, the alloy containing Mo, Cu, Ni, Sn and Sb is added as needed, so that the alloy is completely melted in 5-10 min; the auxiliary material includes carbonizing agent, ferrosilicon, ferromanganese, ferrochrome and ferromolybdenum, and the auxiliary material is added as needed to finely adjust the composition to the target composition, wherein the carbonizing agent is used for carbonization, the ferrosilicon is used for silicon increase, the ferromanganese is used for manganese increase, the ferrochrome is used for chromium increase, and the ferromolybdenum is used for molybdenum increase; then, the temperature is increased to 1420-1480°C, and the chemical composition of the iron liquid is detected.

[0019] In step S2, the smelting material is heated to be overheated, and then spheroidization treatment is performed; wherein the overheating temperature is 1500-1530°C, and the overheating time is 5-10 min.

[0020] The weight percentage of each component in the spheroidizing agent is as follows: Mg: 21-23%, La: 1-2%, Si: 44-46%, Ca: 0.8-1%, Al: 1-1.5%, MgO: 1-2%, Ti: 0.2-0.4%, and the balance of Fe and inevitable impurities; the amount of the spheroidizing agent is 0.9-1.1% of the weight of the mixture. The spheroidizing agent has strong spheroidizing ability, good spheroidizing reaction kinetics condition, and stable spheroidizing reaction, which is beneficial to improve the spheroidizing effect of the ductile iron.

[0021] The weight percentage of each component in the high-efficiency inoculant is as follows: Si: 70-72%, Ca: 1-1.5%, Ba: 3-4%, Al: 1-2%, and the balance is Fe and inevitable impurities; the particle size of the high-efficiency inoculant can be 3-8 mm; and the dosage of the high-efficiency inoculant is 0.4-0.5% of the weight of the mixed material.

[0022] Further, step S2 further comprises adding an auxiliary agent to the inverted ladling inoculated iron liquid, the auxiliary agent comprising the following weight percentage of components: SiO2: 30-40%, Al2O3: 20-30%, CaC2: 30-40%, and the dosage of the auxiliary agent is 0.2-0.3% of the weight of the mixed material. Research shows that adding the above auxiliary agent to the inverted ladling inoculated iron liquid not only helps to improve the roundness and uniformity of the ductile cast iron, but also helps to reduce the size and morphology of the ductile cast iron, thereby maximizing the comprehensive performance of the ductile cast iron material.

[0023] In step S3, the weight percentage of each component in the long-acting stream inoculant is as follows: Si: 60-62%, Ca: 1-1.5%, Re: 3-3.5%, and the balance is Fe and inevitable impurities. The particle size of the long-acting stream inoculant can be 0.2-0.8 mm; and the dosage of the long-acting stream inoculant is 0.1-0.15% of the weight of the mixed material.

[0024] The pouring temperature can be controlled at 1400-1420℃; in addition, the inverted ladling inoculated iron liquid should be poured within 10 min to avoid spheroidization inoculation recession.

[0025] In step S4, the vibration frequency during the vibration aging treatment is 120-200 Hz, and the treatment time is 5-30 min. The above specific vibration aging treatment can obtain good homogenization effect without changing the performance and surface state of the component, which is beneficial to improving the comprehensive performance of the material.

[0026] The weight percentage of each component in the ductile cast iron material of the application is as follows: C: 3.8-4.2%, Si: 2.2-2.5%, Mn: 0.5-0.9%, Mo: 0.2-0.4%, Cu: 0.4-0.6%, Ni: 0.3-0.5%, Sn: 0.01-0.03%, Sb: 0.005-0.015%, Mg: 0.035-0.045%, and the balance is Fe and inevitable impurities.

[0027] Preferably, the weight percentage of each component in the spheroidal graphite cast iron material of the present application is as follows: C: 3.83-3.95%, Si: 2.2-2.42%, Mn: 0.52-0.73%, Mo: 0.27-0.36%, Cu: 0.43-0.51%, Ni: 0.32-0.41%, Sn: 0.013-0.02%, Sb: 0.007-0.011%, Mg: 0.038-0.043%, and the balance being Fe and inevitable impurities.

[0028] Further preferably, the weight percentage of each component in the spheroidal graphite cast iron material of the present application is as follows: C: 3.83-3.95%, Si: 2.2-2.41%, Mn: 0.52-0.59%, Mo: 0.27-0.36%, Cu: 0.43-0.47%, Ni: 0.32-0.33%, Sn: 0.017-0.02%, Sb: 0.007-0.011%, Mg: 0.038-0.039%, and the balance being Fe and inevitable impurities.

[0029] Molybdenum (Mo) can form high-melting-point carbides (MoC, Mo2C) in spheroidal graphite, which are not easy to decompose at high temperatures and can significantly improve the thermal stability of the material; at the same time, molybdenum dissolves between ferrite and cementite, which can refine pearlite and strengthen the matrix. In addition, molybdenum has small phase transition stress at high temperature, which can reduce the volume expansion caused by the decomposition of carbides, thereby reducing the accumulation of thermal stress; molybdenum can effectively hinder the propagation of thermal fatigue cracks by improving the creep resistance and fracture toughness of the material.

[0030] Nickel (Ni) forms a solid solution in the iron matrix, enhancing the plastic deformation ability and promoting austenite stabilization. The addition of nickel can reduce the thermal expansion coefficient, reduce the thermal stress during braking, and delay the initiation of thermal cracks.

[0031] Antimony (Sb) is adsorbed on the graphite-metal interface, hindering carbon diffusion, reducing graphite ball size and distributing uniformly. Fine spherical graphite reduces stress concentration and delays crack initiation, thereby improving the number of thermal fatigue cycles.

[0032] By complex alloying of molybdenum, nickel and antimony, and reasonable control of other chemical components, the synergistic effect of each element in different environments and the synergistic optimization effect of metal elements on collective organization, graphite morphology and thermal stability are fully utilized, significantly improving the strength, hardness and bench thermal crack life of the spheroidal graphite cast iron material.

[0033] The present application also provides a spheroidal graphite cast iron material prepared according to the above preparation method.

[0034] The tensile strength of the spherulitic cast iron material of the present application is greater than or equal to 580 MPa, for example, 580-642 MPa; the yield strength is greater than or equal to 362 MPa, for example, 362-389 MPa; the elongation is greater than or equal to 9%, for example, 9-15%; the hardness is greater than or equal to 185 HB, for example, 185-217 HB; and the hot cracking frequency is greater than or equal to 500 times, for example, 501-563 times.

[0035] The present application also provides the use of the above-mentioned spherulitic cast iron material in the preparation of a spherulitic cast iron brake disc.

[0036] The implementation of the present application has at least the following advantages:

[0037] 1. The spherulitic cast iron material of the present application has a simple composition, fewer added element components, and does not require the addition of rare earth elements, greatly reducing production costs; through scientific and reasonable optimization of the material composition, the synergistic effect between elements is fully utilized, and under the premise of fewer added element components and without the addition of rare earth elements, better comprehensive performance is obtained, especially the hot cracking resistance is significantly improved.

[0038] 2. The preparation process of the present application is optimized from multiple aspects of raw materials, pretreatment agents, spherulizing agents, inoculants, and additives, which is conducive to obtaining more graphite balls with good roundness and uniformity and smaller size and morphology, and is conducive to greatly improving the mechanical properties of the spherulitic cast iron material.

[0039] 3. The preparation process of the present application does not require heat treatment, thereby greatly improving the production efficiency and comprehensive performance of the material; the prepared spherulitic cast iron material realizes synergistic upgrading in three dimensions of "graphite morphology-matrix strength-thermal stress dissipation", which is reflected in a great improvement in the hot cracking frequency in the bench test, and the strength, hardness, and hot cracking life of the material are significantly improved, providing a reliable guarantee for the braking safety of heavy vehicles. DETAILED DESCRIPTION

[0040] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains.

[0041] It should be noted that the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form also includes the plural form unless the context clearly indicates otherwise, and furthermore, it should be understood that when the terms "comprise" and / or "include" are used in the present description, they indicate the presence of a feature, step, operation, device, component, and / or combination thereof.

[0042] The technical solutions of the present application will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of the present application.

[0043] The raw materials used in each embodiment are as follows:

[0044] Pig iron: C: 4.42%, Ti: 0.047%, Si: 0.84%, Mn: 0.18%, P: 0.048%, S: 0.012%, the balance being Fe and inevitable impurities.

[0045] The main indexes of low-manganese scrap steel are as follows: Mn: 0.18%, P: 0.021%, S: 0.018%, Cu: 0.12%, Ti: 0.019%, the balance being Fe and inevitable impurities.

[0046] The main indexes of the re-melted material are as follows: C: 3.87%, Si: 2.27%, Mn: 0.62%, Mo: 0.34%, Cu: 0.46%, Ni: 0.35%, Sn: 0.013%, Sb: 0.015%, Mg: 0.042%, the balance being Fe and inevitable impurities.

[0047] Spherulitic agent: Mg: 22%, La: 1.5%, Si: 45%, Ca: 0.9%, Al: 1.2%, MgO: 1.5%, Ti: 0.3%, the balance being Fe and inevitable impurities; the diameter of the cored wire is 13 mm, the thickness of the steel strip is 0.3 mm, the total weight per meter is 430 g, the weight of the core material per meter is 270 g, and the moisture content is 0.3%;

[0048] High-efficiency inoculant: Si: 70.42%, Ca: 1.39%, Ba: 3.24%, Al: 1.46%, the balance being Fe and inevitable impurities.

[0049] Long-acting stream inoculant: Si: 60.32%, Ca: 1.24%, Re: 3.26%, the balance being Fe and inevitable impurities.

[0050] Embodiment 1

[0051] The weight percentages of each component of the spheroidal graphite cast iron material of this embodiment are as follows: C: 3.95%, Si: 2.41%, Mn: 0.52%, Mo: 0.27%, Cu: 0.43%, Ni: 0.32%, Sn: 0.02%, Sb: 0.007%, Mg: 0.039%, the balance being Fe and inevitable impurities.

[0052] The preparation method of the spheroidal graphite cast iron material of the embodiment is as follows:

[0053] a. The raw materials are weighed from the material pool by the electronic platform scale, and the pig iron, low-manganese scrap steel and recycled materials are weighed according to the batching list, respectively, with the pig iron accounting for 60%, the low-manganese scrap steel accounting for 10% and the recycled materials accounting for 30%.

[0054] b. The recycled materials, low-manganese scrap steel and pig iron are added to the electric furnace, and 1% of silicon carbide by weight of the mixed materials is added as a pretreatment agent, with the particle size of the silicon carbide being 0.5-2 mm. The electric furnace is started and the mixed materials are heated at 1450°C. When the molten iron is completely melted, the poly-slag agent is scattered and stirred, and then the slag is removed. The composition of the molten iron is detected by a carbon-silicon analyzer and a direct-reading spectrometer, and the target composition is adjusted by adding alloys and auxiliary materials according to the detection results.

[0055] c. The temperature is raised to 1510°C and overheated for 10 min, and 39 m of spheroidizing wire (i.e. spheroidizing agent) is added for spheroidization. The amount of spheroidizing wire is 0.986% of the weight of the smelted materials, and the amount is adjusted according to the residual magnesium content. After spheroidization, secondary pouring and inoculation are performed, and 0.4% of high-efficiency inoculant is added during pouring;

[0056] d. The pouring starts, and 0.1% of long-acting stream-inoculant is added for instantaneous inoculation during pouring. The pouring temperature is 1410°C, and the pouring is completed within 10 min.

[0057] e. Vibration aging treatment is performed, with a vibration frequency of 160 Hz and a treatment time of 10 min, to obtain the spheroidal graphite cast iron material.

[0058] The spheroidal graphite cast iron material is detected, and the chemical composition meets the following requirements: C: 3.95%, Si: 2.41%, Mn: 0.52%, Mo: 0.27%, Cu: 0.43%, Ni: 0.32%, Sn: 0.02%, Sb: 0.007%, Mg: 0.039%, and the balance being Fe and unavoidable impurities.

[0059] Example 2

[0060] The weight percentage of each component of the spheroidal graphite cast iron material of the embodiment is as follows: C: 3.83%, Si: 2.2%, Mn: 0.59%, Mo: 0.36%, Cu: 0.47%, Ni: 0.33%, Sn: 0.017%, Sb: 0.011%, Mg: 0.038%, and the balance being Fe and unavoidable impurities.

[0061] The preparation method of the spheroidal graphite cast iron material of the embodiment is as follows:

[0062] a. The raw materials are weighed from the material pool by the electronic platform scale, and the pig iron, low-manganese scrap steel and recycled materials are weighed according to the batching list, respectively, with the pig iron accounting for 60%, the low-manganese scrap steel accounting for 10% and the recycled materials accounting for 30%.

[0063] b. Add the return material, low manganese scrap, pig iron into the electric furnace, then add 0.8% silicon carbide as the pretreatment agent, start the electric furnace, heat the mixture at 1480℃, when the molten iron is completely melted, add the poly-agglomerate agent, stir and then remove the slag, detect the composition of the molten iron by the carbon-silicon analyzer and the direct-reading spectrometer, and then add the alloy and the auxiliary material according to the detection result to adjust to the target composition.

[0064] c. Heat to 1500℃ and superheat for 10 minutes, then feed the wire and spheroidize 40m of the spheroidizing wire, adjust according to the residual magnesium content, the spheroidizing wire is 1.0% of the weight of the smelting material, after spheroidization, perform secondary pouring and inoculation, add 0.45% of the high-efficiency inoculant during pouring;

[0065] d. Start pouring, add 0.1% of the long-acting stream inoculant for instantaneous inoculation, the pouring temperature is 1400℃, and the pouring is completed within 10 minutes;

[0066] e. Perform vibration aging treatment, the vibration frequency is 120Hz, the treatment time is 25 minutes, and the ductile cast iron material is prepared.

[0067] The ductile cast iron material is detected, and the chemical composition meets: C: 3.83%, Si: 2.2%, Mn: 0.59%, Mo: 0.36%, Cu: 0.47%, Ni: 0.33%, Sn: 0.017%, Sb: 0.011%, Mg: 0.038%, and the balance is Fe and inevitable impurities.

[0068] Example 3

[0069] The weight percentage of each component of the ductile cast iron material of the present example is as follows: C: 3.95%, Si: 2.42%, Mn: 0.73%, Mo: 0.31%, Cu: 0.51%, Ni: 0.41%, Sn: 0.013%, Sb: 0.007%, Mg: 0.043%, and the balance is Fe and inevitable impurities.

[0070] The preparation method of the ductile cast iron material of the present example is as follows:

[0071] a. Use the electronic platform scale to weigh the raw materials from the material pool, and weigh the pig iron 60%, low manganese scrap 10%, and return material 30% according to the batching list.

[0072] b. Add the return material, low manganese scrap, pig iron into the electric furnace, then add 1.2% silicon carbide as the pretreatment agent, start the electric furnace, heat the mixture at 1420℃, when the molten iron is completely melted, add the poly-agglomerate agent, stir and then remove the slag, detect the composition of the molten iron by the carbon-silicon analyzer and the direct-reading spectrometer, and then add the alloy and the auxiliary material according to the detection result to adjust to the target composition.

[0073] c. heating to 1530°C and superheating for 5 minutes, feeding a 41 mm wire for spheroidization, adjusting the amount of spheroidization wire according to the residual magnesium content, the amount of spheroidization wire being 1.1% of the weight of the smelted material; after spheroidization, carrying out secondary teeming and inoculation, adding 0.5% of a high-efficiency inoculant during teeming;

[0074] d. starting pouring, adding 0.15% of a long-acting stream inoculant for instantaneous inoculation, the pouring temperature being 1420°C, and completing pouring within 10 minutes;

[0075] e. carrying out vibration aging treatment, the vibration frequency being 200 Hz, and the treatment time being 5 minutes, to obtain the nodular cast iron material.

[0076] The nodular cast iron material is detected, and the chemical composition satisfies: C: 3.95%, Si: 2.42%, Mn: 0.73%, Mo: 0.31%, Cu: 0.51%, Ni: 0.41%, Sn: 0.013%, Sb: 0.007%, Mg: 0.043%, the balance being Fe and inevitable impurities.

[0077] Example 4

[0078] This example is the same as Example 1 except that the pre-treatment agent used in step b is different.

[0079] The pre-treatment agent of this example is composed of the following components by weight percentage: silicon carbide 50%, gray iron 30%, nodular iron 20%, and the amount of the pre-treatment agent being 1% of the weight of the mixed material; the particle size of the silicon carbide is 0.5-2 mm; the weight percentage of each component in the gray iron is as follows: C: 4.0%, Si: 2.2%, Mn: 0.9%, P≤0.3%, S≤0.2%, the balance being Fe and inevitable impurities; the particle size of the gray iron is 1-5 mm; the weight percentage of each component in the nodular iron is as follows: C: 3.8%, Si: 2.5%, Mn: 0.5%, P≤0.05%, S≤0.04%, the balance being Fe and inevitable impurities; the particle size of the nodular iron is 2-8 mm.

[0080] Example 5

[0081] This example is the same as Example 1 except that step c is different.

[0082] Step c of this example is as follows:

[0083] c. heating to 1510°C and superheating for 10 minutes, feeding a spheroidizing wire (i.e. spheroidizing agent) of 39 m, adjusting according to the residual magnesium content, the spheroidizing wire being used in an amount of 0.986% of the weight of the smelted material; after spheroidizing, carrying out secondary teeming and inoculation, adding 0.4% of a high-efficiency inoculant during teeming; subsequently, adding an auxiliary agent to the teemed and inoculated iron liquid, the auxiliary agent being composed of the following components in percentage by weight: SiO2: 30%, Al2O3: 30%, CaC2: 40%, the auxiliary agent being used in an amount of 0.2% of the weight of the mixed material.

[0084] Comparative Example 1

[0085] The weight percentage of each component of the ductile cast iron material of the present comparative example is as follows: C: 3.8%, Si: 2.0%, Mn: 0.10%, Mg: 0.04%, RE: 0.008%, P: 0.02%, S: 0.01%, Cu: 0.2%, Mo: 0.02%, Ni ： 1.2%, Sn: 0.04%, Ti: 0.01%, V: 0.02%, B: 0.0008%, Sb: 0.004%, Cr: 0.05%, the balance being Fe and inevitable impurities; the preparation method is referred to Example 1, and the amount of each raw material, auxiliary material, etc. is adjusted according to the above components.

[0086] Comparative Example 2

[0087] The weight percentage of each component of the ductile cast iron material of the present comparative example is as follows: C: 3.8%, Si: 3.6%, Mn: 0.2%, Sn: 0.02%, Ge: 0.008%, Ni: 0.5%, Ti: 0.35%, Mo: 0.5%, Sb: 0.008%, RE: 0.03%, P≤0.04%, S≤0.02%, the balance being Fe and inevitable impurities; the preparation method is referred to Example 1, and the amount of each raw material, auxiliary material, etc. is adjusted according to the above components.

[0088] Comparative Example 3

[0089] The weight percentage of each component of the ductile cast iron material of the present comparative example is as follows: C: 3.65%, Si: 2.60%, Mn: 0.41%, P: 0.04%, S: 0.019%, Cu: 0.60%, Sb: 0.010%, Ni: 1.0%, Mo: 0.3%, V: 0.1%, the balance being Fe and inevitable impurities; the preparation method is referred to Example 1, and the amount of each raw material, auxiliary material, etc. is adjusted according to the above components.

[0090] Comparative Example 4

[0091] The weight percentage of each component in the nodular cast iron material of the present comparative example is as follows: C: 3.4%, Si: 2.9%, Cr: 0.4%, Mn: 0.3%, Al: 0.2%, Ni: 0.6%, Mg: 0.4%, Cu: 0.5%, Mo: 0.3%, Ta: 0.08%, Y: 0.05%, Sb: 0.02%, S≤0.02%, P≤0.04%, the balance being Fe and inevitable impurities; the preparation method refers to Example 1, and the amount of each raw material, auxiliary material, etc. is adjusted according to the above components.

[0092] Comparative Example 5

[0093] Except that the spherification agent composition is different, the rest is the same as Example 1.

[0094] The weight percentage of each component in the spherification agent of the present comparative example is as follows: Mg: 8.5%, Ca: 3.5%, Ti: 0.45%, V: 0.1%, Nb: 0.15%, Ce: 0.2%, the balance being Fe and inevitable impurities.

[0095] Comparative Example 6

[0096] Except that step e is different, the rest is the same as Example 1.

[0097] Step e of the present comparative example is: heat treatment is carried out, specifically as follows: first, the furnace temperature is raised to 900 DEG C and kept for 2h, then the furnace temperature is cooled to 560 DEG C and kept for 3h, when the furnace temperature is cooled to 300 DEG C, the furnace is discharged and air-cooled to obtain the nodular cast iron material.

[0098] Test Example 1

[0099] The nodular cast iron materials prepared in each example and comparative example are detected by the following method:

[0100] The tensile strength, yield strength and elongation detection method is GB / T 228.1-2021 “Metallic Materials Tensile Test”; the Brinell hardness detection method is GB / T 231.1-2021 “Metallic Materials Brinell Hardness Test”; the hot cracking frequency detection method is Q / ZZ 11656-2021 “Automobile Air Pressure Disc Brake Brake Disc”.

[0101] The detection results are shown in Table 1.

[0102] Table 1 Detection results of each nodular cast iron material

[0103]

[0104]

[0105] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing ductile iron material, characterized in that: The steps include: S1: heating a mixture of pig iron, low-manganese scrap steel, and recycled materials until completely melted, adding alloys and auxiliary materials to adjust the target composition to obtain molten iron; S2: adding spheroidizing agent to the original molten iron for spheroidizing treatment, and then performing inoculation by pouring ladle, and adding high-efficiency inoculant during pouring ladle; S3: pouring, adding long-lasting inoculant for instant inoculation during pouring; S4: Perform vibration aging treatment to obtain ductile iron material.

2. The preparation method according to claim 1, characterized in that In step S1, the mass ratio of pig iron, low-manganese scrap steel, and recycled materials in the mixture is (5.5-6.5):(0.8-1.2):(2.5-3.5); a pretreatment agent is added to the mixture, the pretreatment agent comprising silicon carbide, and the amount of the pretreatment agent is 0.8-1.2% by weight of the mixture; Preferably, the pretreatment agent comprises the following components in weight percentage: 40-60% silicon carbide, 20-30% gray iron, and 10-20% ductile iron.

3. The preparation method according to claim 1, characterized in that In step S2, the weight percentages of the components in the spheroidizing agent are as follows: Mg: 21-23%, La: 1-2%, Si: 44-46%, Ca: 0.8-1%, Al: 1-1.5%, MgO: 1-2%, Ti: 0.2-0.4%, and the balance is Fe and inevitable impurities; the amount of the spheroidizing agent used is 0.9-1.1% of the weight of the mixture.

4. The preparation method according to claim 1, characterized in that In step S2, the weight percentages of the components in the high-efficiency inoculant are as follows: Si: 70-72%, Ca: 1-1.5%, Ba: 3-4%, Al: 1-2%, and the remainder is Fe and unavoidable impurities; the amount of the high-efficiency inoculant used is 0.4-0.5% of the weight of the mixture.

5. The preparation method according to claim 1, characterized in that Step S2 also includes: adding an additive to the molten iron after the inoculation, the additive including the following components in weight percentage: SiO2: 30-40%, Al2O3: 20-30%, CaC2: 30-40%, and the amount of the additive is 0.2-0.3% of the weight of the mixture.

6. The preparation method according to claim 1, characterized in that In step S3, the weight percentages of the components in the long-acting flow-inoculating agent are as follows: Si: 60-62%, Ca: 1-1.5%, Re: 3-3.5%, and the balance is Fe and unavoidable impurities; the amount of the long-acting flow-inoculating agent used is 0.1-0.15% of the weight of the mixture.

7. The preparation method according to claim 1, characterized in that In step S4, the vibration frequency during the vibration aging treatment is 120-200 Hz, and the treatment time is 5-30 minutes.

8. The preparation method according to claim 1, characterized in that In step S4, the weight percentages of the components in the ductile iron material are as follows: C: 3.8-4.2%, Si: 2.2-2.5%, Mn: 0.5-0.9%, Mo: 0.2-0.4%, Cu: 0.4-0.6%, Ni: 0.3-0.5%, Sn: 0.01-0.03%, Sb: 0.005-0.015%, Mg: 0.035-0.045%, and the remainder is Fe and unavoidable impurities.

9. A ductile iron material, characterized in that: Prepared according to the preparation method according to any one of claims 1-8.

10. Use of the ductile iron material according to claim 9 in the preparation of a ductile iron brake disc.

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