A high-hardness, high-toughness tempered sorbitic wear-resistant cast steel, its preparation method and application

Abstract

This invention belongs to the field of wear-resistant cast steel and its heat treatment technology, and discloses a high-hardness, high-toughness tempered sorbitic wear-resistant cast steel, its preparation method, and its application. The chemical composition of this wear-resistant cast steel, by mass percentage, is: C: 0.30-0.70%, Si: 0.2-0.7%, Mn: 0.4-1.2%, Cr: 2.0-3.4%, Ni: 0.4-1.0%, Mo: 0.5-1.0%, V: 0.05-0.2%, P≤0.035%, S≤0.040%, with the balance being Fe and unavoidable impurities; and 2.8%≤(Cr+Mo+V)≤3.8%. This invention, by optimizing the alloy composition and heat treatment process, suppresses the formation of "ghost martensite," resulting in a high-hardness, high-toughness tempered sorbitic cast steel that is particularly suitable for the preparation of wear-resistant parts under medium-to-high stress impact abrasive wear conditions.

Description

Technical Field

[0001] This invention belongs to the field of wear-resistant cast steel and its heat treatment technology, specifically relating to a high-hardness and toughness tempered sorbitic wear-resistant cast steel, its preparation method and application. Background Technology

[0002] Semi-autogenous mills and ball mills are core grinding equipment in mineral processing. Liners are functional inner linings installed on the inner wall of the mill cylinder to protect the cylinder, enhance the grinding media, and optimize grinding action. Their service life directly affects equipment efficiency, energy consumption, and operating costs. To resist the impact and cutting of ore and grinding balls, liner materials need to possess both excellent toughness and high hardness. However, there is usually an inverse relationship between the hardness and toughness of a material. Traditional wear-resistant steel materials have insufficient hardness-toughness matching, resulting in annual liner wear reaching millions of tons and hindering the application of large-scale equipment in cost reduction and efficiency improvement in grinding processes. Therefore, research on the control of hardness and toughness of steel materials used for liners has always been a hot topic in the field of mining machinery.

[0003] Chinese patent CN119372552B discloses a martensitic wear-resistant liner and its preparation method. Based on traditional low-alloy wear-resistant steel, this patent adds trace amounts of refining agents (RE) and appropriate amounts of Zr, utilizing the heterogeneous nucleation effect of the Zr (C, N) phase during solidification and its hindering effect on grain boundary movement during normalizing to refine the grains. Combined with appropriate heat treatment processes, a martensitic steel with both high toughness and hardness (hardness: 52.5-59.5 HRC, V-notch impact absorption energy: 6.2-9.6 J) is obtained. However, this martensitic steel has sufficient hardness but insufficient toughness, and is only suitable for preparing liners for small-to-medium diameter semi-autogenous grinding mills and ball mills.

[0004] Chinese patent CN109913751A discloses a high-strength and high-toughness bainitic wear-resistant steel and its preparation method. By forging and rolling, defects such as porosity and inclusions within the cast billet microstructure are reduced, while grain refinement is achieved. Combined with spheroidizing annealing and alternating water-air quenching heat treatment, a bainitic microstructure with both high hardness and toughness is obtained. However, this production process involves vacuum melting, refining, forging or multi-pass rolling, and various heat treatment processes, resulting in a complex process path, relatively high manufacturing costs, and difficulty in forming complex and large-sized wear-resistant parts.

[0005] Chinese patent CN106591731B discloses an alloy material for the liner plate of a large semi-autogenous grinding mill. Based on traditional pearlitic steel, by reducing the carbon content and employing a heat treatment process of austenitization, oil quenching, and high-temperature tempering, a wear-resistant steel with a pearlitic + sorbitic microstructure is prepared. However, its innovation lies mainly in the improved heat treatment process, which greatly increases production efficiency, but its performance and service life are not significantly improved compared to traditional pearlitic steel. Furthermore, the oil quenching process results in significant thermal stress, which, combined with martensitic phase transformation stress, makes large components prone to quenching cracks and exhibits poor stability.

[0006] In summary, existing wear-resistant parts are mostly made of martensitic, bainitic, or pearlitic wear-resistant steels, with tempered sorbitic wear-resistant steels rarely reported. Furthermore, these steel materials suffer from difficulties in achieving a balance between hardness and toughness, high production costs, and poor adaptability to large parts. Therefore, there is an urgent need to develop a new type of wear-resistant steel that balances strength and toughness, is cost-effective, and is suitable for producing large wear-resistant parts, meeting the practical application requirements of medium-to-high stress impact abrasive wear conditions. Summary of the Invention

[0007] In order to overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a high-hardness, high-toughness tempered sorbitic wear-resistant cast steel.

[0008] Another objective of this invention is to provide a method for preparing high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel. This wear-resistant cast steel is based on traditional pearlitic wear-resistant steel, with the addition of appropriate amounts of Cr, Mo, and V. After normalizing, subcritical isothermal, staged quenching, and high-temperature tempering heat treatments, the blocky ferrite structure is refined and reduced, resulting in a multiphase structure where spherical carbides are dispersed within a fine equiaxed ferrite matrix. This multiphase structure maintains high hardness while exhibiting good toughness, demonstrating a good balance between hardness and toughness. Furthermore, the preparation process of this high-hardness, high-toughness, and wear-resistant cast steel is simple and low-cost.

[0009] Another object of the present invention is to provide applications for the above-mentioned high-hardness and toughness tempered sorbitic wear-resistant cast steel, especially suitable for manufacturing wear-resistant parts under medium and high stress impact abrasive wear conditions such as large semi-autogenous mill liners and impact crusher guard plates.

[0010] The present invention adopts the following technical solution:

[0011] A high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel, wherein the chemical composition of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel, by mass percentage, is: C: 0.30-0.70%, Si: 0.2-0.7%, Mn: 0.4-1.2%, Cr: 2.0-3.4%, Ni: 0.4-1.0%, Mo: 0.5-1.0%, V: 0.05-0.2%, P≤ 0.035%, S≤ 0.040%, with the balance being Fe and unavoidable impurities.

[0012] Preferably, the chemical composition of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel, by mass percentage, is: C: 0.40-0.65%, Si: 0.3-0.6%, Mn: 0.6-1.0%, Cr: 2.0-3.2%, Ni: 0.4-0.8%, Mo: 0.6-0.9%, V: 0.05-0.2%, P ≤ 0.032%, S ≤ 0.038%, with the balance being Fe and unavoidable impurities.

[0013] Preferably, the chemical composition of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel, by mass percentage, is: C: 0.45-0.60%, Si: 0.3-0.6%, Mn: 0.7-0.9%, Cr: 2.2-3.0%, Ni: 0.5-0.8%, Mo: 0.6-0.9%, V: 0.1-0.2%, P ≤ 0.031%, S ≤ 0.035%, with the balance being iron and unavoidable impurities.

[0014] Preferably, the chemical composition of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel, by mass percentage, is: C: 0.50%, Si: 0.3%, Mn: 0.8%, Cr: 2.6%, Ni: 0.8%, Mo: 0.7%, V: 0.1%, P: 0.031%, S: 0.032%, with the balance being iron and unavoidable impurities.

[0015] Preferably, the chemical composition of the high-hardness, high-toughness tempered sorbitic wear-resistant cast steel, in terms of Cr, Mo, and V, satisfies the following condition by mass percentage: 2.8% ≤ (Cr + Mo + V) ≤ 3.8%.

[0016] Preferably, the chemical composition of the high-hardness, high-toughness tempered sorbitic wear-resistant cast steel, in terms of Cr, Mo and V, satisfies the following condition by mass percentage: 3.0% ≤ (Cr + Mo + V) ≤ 3.6%.

[0017] Preferably, the high-hardness and toughness tempered sorbitic wear-resistant cast steel has a hardness value of 37.5-43.6 HRC and a V-notch impact absorption energy of 13.7-18.2 J.

[0018] A method for preparing high-hardness, high-toughness, tempered martensitic wear-resistant cast steel includes the following steps:

[0019] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are smelted, and the resulting molten steel is inoculated to obtain molten steel to be cast.

[0020] S2) Casting: The molten steel obtained in step S1 is poured, solidified and cooled to obtain the casting;

[0021] S3) Normalizing: After cleaning the sand from the casting obtained in step S2, heat and hold it at that temperature, then air cool it to room temperature to obtain the normalized casting.

[0022] S4) Subcritical graded quenching: The normalized casting obtained in step S3 is reheated to the subcritical isothermal region, held at that temperature, and then graded quenched to room temperature to obtain the quenched casting.

[0023] S5) Tempering: Temper the quenched casting obtained in step S4 and keep it at the same temperature, then air cool it to room temperature to obtain the final product.

[0024] Preferably, the graded quenching step in step S4 is as follows: first, air-cooling to 290~310℃, followed by air cooling to room temperature.

[0025] Preferably, the tempering temperature in step S5 is 570-610℃, and the holding time is 6-10 h.

[0026] Preferably, the heating in step S3 is to heat to 980-1050℃ and hold for 4-8 hours.

[0027] Preferably, the reheating temperature in step S4 is 800-860℃, and the holding time is 6-10 h.

[0028] Preferably, the tempering temperature in step S5 is 570-610℃, and the holding time is 6-10 h.

[0029] Preferably, the pig iron, scrap steel, pure iron metal and ferroalloys mentioned in step S1 are well-known commercial raw materials that can all be purchased from the market.

[0030] Preferably, the inoculation treatment in step S1 is an inoculation treatment using a rare earth alloy.

[0031] The application of the above-mentioned high-hardness and toughness tempered martensitic cast steel in the manufacture of wear-resistant parts.

[0032] Preferably, the above-mentioned high-hardness and toughness tempered sorbitic wear-resistant cast steel is used in the manufacture of wear-resistant parts under high-stress impact abrasive wear conditions.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] As carbon content increases, the morphology of martensite changes from lath to blocky. During high-temperature tempering, carbides pin grain boundaries, severely hindering recrystallization. This results in some larger blocky martensite retaining the martensite block outline in the ferrite formed after high-temperature tempering, commonly known as "ghost martensite." "Ghost martensite" contains high-density dislocations and fine but unevenly distributed carbides, exhibiting high hardness but significantly reducing the material's impact toughness. The tempered sorbitic wear-resistant cast steel produced in this invention is based on traditional pearlitic wear-resistant steel, with the addition of appropriate amounts of Cr, Mo, and V. Through normalizing, subcritical isothermal, staged quenching, and high-temperature tempering heat treatment, incomplete austenitization (subcritical isothermal) and staged quenching are used to suppress the formation of "ghost martensite," thereby enabling the tempered sorbite to possess both high hardness and excellent toughness. The tempered sorbitic wear-resistant steel prepared by this invention has a hardness value of 37.5-43.6 HRC, while its V-notch impact absorption energy is 13.7-18.2 J, exhibiting a good hardness-toughness match, which is superior to the currently used martensitic and pearlitic wear-resistant steels.

[0035] The method for preparing high-hardness, high-toughness tempered sorbitic wear-resistant cast steel provided by this invention is simple and easy to control. After effectively suppressing "ghost martensite," the resulting tempered sorbitic wear-resistant cast steel has a slightly lower hardness than the traditional sorbitic wear-resistant steel obtained by fully austenitizing quenching and then tempering, but its toughness is significantly improved. Compared with pearlitic wear-resistant steel, both its hardness and toughness are improved. At the same time, the production cost is low, and it has broad application prospects.

[0036] The high-hardness, high-toughness tempered sorbitic wear-resistant cast steel prepared by this invention is particularly suitable for manufacturing wear-resistant parts for medium- and high-stress impact abrasive wear conditions, such as large ball mills, semi-autogenous mills and liners, and impact crusher guard plates. Attached Figure Description

[0037] Figure 1 The microstructure of the tempered sorbitic cast steel of the present invention is shown in (a)-(d). The microstructure of the tempered sorbitic cast steel produced in Example 2 and Comparative Examples 1, 2 and 3 is shown in (a)-(d). The blocky microstructure is "ghost martensite".

[0038] Figure 2 The images show the impact fracture morphology of the tempered martensitic cast steel of the present invention. (a) and (b) show the impact fracture morphology of the tempered martensitic cast steel produced in Example 2 and Comparative Example 1. The number of dimples in the impact fracture of Example 2 is significantly greater than that of Comparative Example 1. Detailed Implementation

[0039] The following detailed embodiments further illustrate the content of the present invention. However, the scope of the present invention is not limited to the following embodiments, and conventional techniques can be referred to for process parameters not specifically specified.

[0040] The raw materials used in the embodiments, such as pig iron, scrap steel, pure iron metal, and ferroalloys, are all well-known commercial raw materials that can be purchased from the market.

[0041] Example 1: A high-hardness, high-toughness, tempered martensitic wear-resistant cast steel

[0042] The chemical composition and mass content of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel are as follows: C: 0.40%, Si: 0.3%, Mn: 1.0%, Cr: 2.8%, Ni: 0.8%, Mo: 0.8%, V: 0.1%, P: 0.03%, S: 0.028%, with the balance being Fe and unavoidable impurities, (Cr + Mo + V): 3.7%. The preparation method of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel includes the following steps:

[0043] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The molten steel is placed in a steel ladle and inoculated with rare earth alloys to obtain molten steel to be poured.

[0044] S2) Casting: The molten steel obtained in step S1 is poured through the gate, and the casting is solidified and cooled to obtain the casting.

[0045] S3) Normalizing: The casting obtained in step S2 is cleaned of sand and then sent to a heat treatment furnace, heated to 1050℃, held for 8 hours and then air-cooled to room temperature to obtain the normalized casting.

[0046] S4) Subcritical graded quenching: The normalized casting obtained in step S3 is reheated to 860℃ and held for 6 hours. Then it is first cooled to 300℃ by air mist, and then air cooled to room temperature to obtain the casting after subcritical graded quenching.

[0047] S5) Tempering: The casting obtained in step S4 after subcritical grade quenching is sent back into the heat treatment furnace and heated to 610℃ and held for 6 hours, then air-cooled to room temperature to obtain the final product.

[0048] Example 2: A high-hardness, high-toughness, tempered martensitic wear-resistant cast steel

[0049] The chemical composition and mass content of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel are as follows: C: 0.50%, Si: 0.3%, Mn: 0.8%, Cr: 2.6%, Ni: 0.8%, Mo: 0.7%, V: 0.1%, P: 0.031%, S: 0.032%, with the balance being Fe and unavoidable impurities, (Cr + Mo + V): 3.4%. The preparation method of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel includes the following steps:

[0050] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The molten steel is placed in a steel ladle and inoculated with rare earth alloys to obtain molten steel to be poured.

[0051] S2) Casting: The molten steel obtained in step S1 is poured through the gate, and the casting is solidified and cooled to obtain the casting.

[0052] S3) Normalizing: The casting obtained in step S2 is cleaned of sand and then sent to a heat treatment furnace, heated to 1020℃, held for 8 hours and then air-cooled to room temperature to obtain the normalized casting.

[0053] S4) Subcritical graded quenching: The normalized casting obtained in step S3 is reheated to 840℃ and held for 8 hours. Then it is first cooled to 300℃ by air mist, and then air cooled to room temperature to obtain the casting after subcritical graded quenching.

[0054] S5) Tempering: The casting obtained in step S4 after subcritical grade quenching is sent back into the heat treatment furnace and heated to 600℃ and held for 6 hours, then air-cooled to room temperature to obtain the final product.

[0055] Example 3: A high-hardness, high-toughness, tempered martensitic wear-resistant cast steel

[0056] The chemical composition and mass content of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel are as follows: C: 0.60%, Si: 0.4%, Mn: 0.7%, Cr: 2.4%, Ni: 0.7%, Mo: 0.6%, V: 0.1%, P: 0.028%, S: 0.030%, with the balance being Fe and unavoidable impurities, (Cr + Mo + V): 3.1%. The preparation method of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel includes the following steps:

[0057] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The molten steel is placed in a steel ladle and inoculated with rare earth alloys to obtain molten steel to be poured.

[0058] S2) Casting: The molten steel obtained in step S1 is poured through the gate, and the casting is solidified and cooled to obtain the casting.

[0059] S3) Normalizing: The casting obtained in step S2 is cleaned of sand, then sent to a heat treatment furnace, heated to 1000℃, held for 10 h and then air-cooled to room temperature to obtain the normalized casting.

[0060] S4) Subcritical graded quenching: The normalized casting obtained in step S3 is reheated to 820℃ and held for 8 hours. Then it is first cooled to 300℃ by air mist, and then air cooled to room temperature to obtain the casting after subcritical graded quenching.

[0061] S5) Tempering: The casting obtained in step S4 after subcritical grade quenching is sent back into the heat treatment furnace and heated to 590℃ and held for 8 hours, then air-cooled to room temperature to obtain the final product.

[0062] Example 4: A high-hardness, high-toughness, tempered martensitic wear-resistant cast steel

[0063] The chemical composition and mass content of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel are as follows: C: 0.65%, Si: 0.6%, Mn: 0.60%, Cr: 2.2%, Ni: 0.50%, Mo: 0.60%, V: 0.05%, P: 0.026%, S: 0.031%, with the balance being Fe and unavoidable impurities, (Cr + Mo + V): 2.85%. The preparation method of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel includes the following steps:

[0064] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The molten steel is placed in a steel ladle and inoculated with rare earth alloys to obtain molten steel to be poured.

[0065] S2) Casting: The molten steel obtained in step S1 is poured through the gate, and the casting is solidified and cooled to obtain the casting.

[0066] S3) Normalizing: The casting obtained in step S2 is cleaned of sand and then sent to a heat treatment furnace, heated to 980°C, held for 12 hours and then air-cooled to room temperature to obtain the normalized casting.

[0067] S4) Subcritical graded quenching: The normalized casting obtained in step S3 is reheated to 800℃ and held for 8 hours. Then it is first cooled to 300℃ by air mist, and then air cooled to room temperature to obtain the casting after subcritical graded quenching.

[0068] S5) Tempering: The casting obtained in step S4 after subcritical grade quenching is sent back into the heat treatment furnace and heated to 570℃ and held for 8 hours, then air-cooled to room temperature to obtain the final product.

[0069] Comparative Example 1: A High-Hardness Tempered Martensitic Cast Steel

[0070] The chemical composition and mass content of the high-hardness tempered sorbitic cast steel are as follows: C: 0.50%, Si: 0.3%, Mn: 0.8%, Cr: 2.6%, Ni: 0.8%, Mo: 0.7%, V: 0.1%, P: 0.031%, S: 0.032%, with the balance being Fe and unavoidable impurities, (Cr + Mo + V): 3.4%. The preparation method of the high-hardness tempered sorbitic cast steel includes the following steps:

[0071] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The molten steel is placed in a steel ladle and inoculated with rare earth alloys to obtain molten steel to be poured.

[0072] S2) Casting: The molten steel obtained in step S1 is poured through the gate, and the casting is solidified and cooled to obtain the casting.

[0073] S3) Normalizing: The casting obtained in step S2 is cleaned of sand and then sent to a heat treatment furnace, heated to 1020℃, held for 8 hours and then air-cooled to room temperature to obtain the normalized casting.

[0074] S4) Full austenitization + graded quenching: The normalized casting obtained in step S3 is reheated to 920℃ and held for 8 hours. Then it is first cooled to 300℃ by air cooling and then air cooled to room temperature to obtain the casting after full austenitization + graded quenching.

[0075] S5) Tempering: The casting obtained in step S4 after subcritical grade quenching is sent back into the heat treatment furnace and heated to 600℃ and held for 6 hours, then air-cooled to room temperature to obtain the final product.

[0076] Comparative Example 2: A High-Hardness Tempered Martensitic Cast Steel

[0077] The chemical composition and mass content of the high-hardness tempered sorbitic cast steel are as follows: C: 0.50%, Si: 0.3%, Mn: 0.8%, Cr: 2.6%, Ni: 0.8%, Mo: 0.7%, V: 0.1%, P: 0.031%, S: 0.032%, with the balance being Fe and unavoidable impurities, (Cr + Mo + V): 3.4%. The preparation method of the high-hardness tempered sorbitic cast steel includes the following steps:

[0078] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The molten steel is placed in a steel ladle and inoculated with rare earth alloys to obtain molten steel to be poured.

[0079] S2) Casting: The molten steel obtained in step S1 is poured through the gate, and the casting is solidified and cooled to obtain the casting.

[0080] S3) Normalizing: The casting obtained in step S2 is cleaned of sand and then sent to a heat treatment furnace, heated to 1020℃, held for 8 hours and then air-cooled to room temperature to obtain the normalized casting.

[0081] S4) Subcritical quenching: The normalized casting obtained in step S3 is reheated to 840℃, held for 8 hours, and then cooled to room temperature by air and mist to obtain the subcritical quenched casting.

[0082] S5) Tempering: The subcritical quenched casting obtained in step S4 is sent back into the heat treatment furnace and heated to 600℃ and held for 6 hours. It is then air-cooled to room temperature to obtain the final product.

[0083] Comparative Example 3: A High-Hardness Tempered Martensitic Cast Steel

[0084] The chemical composition and mass content of the high-hardness tempered sorbitic cast steel are as follows: C: 0.50%, Si: 0.4%, Mn: 0.8%, Cr: 3.5%, Ni: 0.7%, Mo: 0.8%, V: 0.1%, P: 0.031%, S: 0.032%, with the balance being Fe and unavoidable impurities, (Cr + Mo + V): 4.4%. The preparation method of the high-hardness tempered sorbitic cast steel includes the following steps:

[0085] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The molten steel is placed in a steel ladle and inoculated with rare earth alloys to obtain molten steel to be poured.

[0086] S2) Casting: The molten steel obtained in step S1 is poured through the gate, and the casting is solidified and cooled to obtain the casting.

[0087] S3) Normalizing: The casting obtained in step S2 is cleaned of sand and then sent to a heat treatment furnace, heated to 1020℃, held for 8 hours and then air-cooled to room temperature to obtain the normalized casting.

[0088] S4) Subcritical graded quenching: The normalized casting obtained in step S3 is reheated to 840℃ and held for 8 hours. Then, it is first cooled to 300℃ by air and then air cooled to room temperature to obtain the casting after subcritical graded quenching.

[0089] S5) Tempering: The casting obtained in step S4 after subcritical grade quenching is sent back into the heat treatment furnace and heated to 600℃ and held for 6 hours, then air-cooled to room temperature to obtain the final product.

[0090] Comparative Example 4: Conventional Pearlitic Cast Steel

[0091] The chemical composition and mass content of the conventional pearlitic cast steel are as follows: C: 0.50%, Si: 0.3%, Mn: 0.8%, Cr: 2.6%, Ni: 0.8%, Mo: 0.7%, V: 0.1%, P: 0.031%, S: 0.032%, with the balance being Fe and unavoidable impurities, (Cr + Mo + V): 3.4%. The preparation method of the conventional pearlitic cast steel includes the following steps:

[0092] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The molten steel is placed in a steel ladle and inoculated with rare earth alloys to obtain molten steel to be poured.

[0093] S2) Casting: The molten steel obtained in step S1 is poured through the gate, and the casting is solidified and cooled to obtain the casting.

[0094] S3) Normalizing: The casting obtained in step S2 is cleaned of sand and then sent to a heat treatment furnace, heated to 1020℃, held for 8 hours and then air-cooled to room temperature to obtain the normalized casting.

[0095] S4) Isothermal transformation: The normalized casting obtained in step S3 is reheated to 920℃ and held for 8 hours. Then it is transferred to a heat treatment furnace at 600℃ and held for 8 hours. Finally, it is air-cooled to room temperature to obtain the isothermal transformation pearlitic casting.

[0096] Example and Comparative Material Performance Tests

[0097] Experimental Methods: Performance tests were conducted on the cast steels prepared in Examples 1-4 and Comparative Examples 1-4. The room temperature impact test employed a V-notch impact test. Before the Vickers hardness test, the test surfaces of the samples were ground and polished. The impact abrasive wear test was conducted on an MLD-10 dynamic load abrasive wear testing machine. The impact energy was 4.0 J, the impact frequency was 100 times per minute, the sample was 45# steel, the rotation speed was 100 revolutions per minute, and the abrasive used in the impact wear test was 5 kg of quartz sand with a particle size between 60 and 80 mesh. Each group of samples was pre-ground for 30 minutes before the test. During the impact wear process, the weight loss was measured once every 30 minutes as one wear cycle, for a total of five cycles, totaling 2.5 hours.

[0098] The test results are listed in Table 1.

[0099] Table 1 Performance Test Results

[0100]

[0101] The hardness in Table 1 is the average of 10 values, and the V-notch impact energy absorption and wear weight loss are the average of 3 values.

[0102] As shown in Table 1, the hardness of the high-hardness and toughness tempered sorbitic wear-resistant cast steel prepared by the present invention can reach 37.5 to 43.6 HRC, while the V-notch impact absorption energy reaches 13.7 to 18.2 J, which has a good hardness and toughness ratio. Under different phase composition processing conditions, the hardness and V-notch impact absorption energy of Example 2 (subcritical staged quenching) decreased by approximately 5.5% and 4.5% (2.2 and 1.8 HRC) compared to Comparative Example 1 (fully austenitized + staged quenching) and Comparative Example 2 (subcritical quenching), respectively, but the toughness increased by 120.5% and 74.2% (9.3 and 7.5 J), respectively. Under similar composition and processing conditions, the hardness of Example 2 (Cr + Mo + V: 3.4%) decreased by 5.8% (2.3 HRC) compared to Comparative Example 3 (Cr + Mo + V: 4.4%), but the toughness increased by 50.4% (5.9 J). Under different matrix structures and the same composition, the hardness and toughness of Example 2 (tempered sorbite) increased by 12.4% (4.8 HRC) and 45.4% (5.5 J) compared to Comparative Example 4 (isothermal pearlite), respectively.

[0103] The differences between this invention and existing heat treatment processes and compositions for wear-resistant steel are as follows: (1) Subcritical isothermal: On the one hand, it can retain some carbides, reducing the content of blocky martensite after staged quenching; on the other hand, it can refine the grains, reducing the size of blocky martensite after quenching, thereby reducing the content and size of "ghost martensite" after high-temperature tempering, and improving the impact toughness of the material; (2) Staged quenching: On the one hand, it can reduce thermal stress; on the other hand, rapid cooling at high temperature avoids pearlite transformation, and slow cooling at low temperature precipitates a small amount of carbides, reducing the content of blocky martensite after quenching, thereby reducing the content of "ghost martensite" after high-temperature tempering. Figure 1 As shown in (a) to (c), the content and size of "ghost martensite" are inversely proportional to impact toughness. (3) 2.8% ≤ (Cr + Mo + V) ≤ 3.8%. In order to improve the hardness of tempered sorbite, appropriate amounts of Cr, Mo, and V elements need to be added. However, excessive Cr, Mo, and V will cause the carbides to coarsen after high-temperature tempering (e.g. Figure 1 As shown in (a) and (d), this reduces the toughness of tempered sorbitic steel. In summary, this invention significantly reduces the content and size of "ghost martensite" after high-temperature tempering by optimizing alloy composition and quenching heat treatment process, thereby obtaining a tempered sorbitic structure that combines high hardness and toughness.

[0104] This invention optimizes the composition and heat treatment process, enabling tempered sorbitic cast steel to maintain high hardness while retaining good toughness, and at a low production cost. This overcomes the contradiction between the hardness-toughness balance and production cost of existing metallic materials under medium-to-high stress impact abrasive wear conditions. The tempered sorbitic steel, possessing both high hardness and good impact toughness, exhibits better wear resistance than traditional pearlitic steel in high-stress impact abrasive wear tests, making it particularly suitable for manufacturing wear-resistant parts for medium-to-high stress impact abrasive wear conditions, such as liners for large semi-autogenous mills, ball mills, and impact crusher plates.

[0105] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A high-hardness, high-toughness, tempered martensitic wear-resistant cast steel, characterized in that, The chemical composition of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel, by mass percentage, is: C: 0.30-0.70%, Si: 0.2-0.7%, Mn: 0.4-1.2%, Cr: 2.0-3.4%, Ni: 0.4-1.0%, Mo: 0.5-1.0%, V: 0.05-0.2%, P ≤ 0.035%, S ≤ 0.040%, with the balance being Fe and unavoidable impurities; The chemical composition of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel contains Cr, Mo, and V that satisfy the following condition: 2.8% ≤ (Cr + Mo + V) ≤ 3.8%; The preparation method of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel includes the following steps: S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are smelted, and the resulting molten steel is inoculated to obtain molten steel to be cast. S2) Casting: The molten steel obtained in step S1 is poured, solidified and cooled to obtain the casting; S3) Normalizing: After cleaning the sand from the casting obtained in step S2, heat and hold it at that temperature, then air cool it to room temperature to obtain the normalized casting. S4) Subcritical stage quenching: The normalized casting obtained in step S3 is reheated to the subcritical isothermal region, held at that temperature, and then stage quenched to room temperature to obtain the quenched casting. S5) Tempering: Temper the quenched casting obtained in step S4 and keep it at a certain temperature, then air cool it to room temperature to obtain the final product. The reheating temperature in step S4 is 800-860℃, and the holding time is 6-10 h; the graded quenching step is: first air-cooled to 290~310℃, and then air-cooled to room temperature.

2. The high-hardness, high-toughness, tempered martensitic wear-resistant cast steel as described in claim 1, characterized in that, The chemical composition of the high-hardness, high-toughness, tempered sorbitic wear-resistant cast steel, by mass percentage, is: C: 0.45-0.60%, Si: 0.3-0.6%, Mn: 0.7-0.9%, Cr: 2.2-3.0%, Ni: 0.5-0.8%, Mo: 0.6-0.9%, V: 0.1-0.2%, P≤ 0.031%, S≤ 0.035%, with the balance being iron and unavoidable impurities.

3. The high-hardness, high-toughness, tempered martensitic wear-resistant cast steel as described in claim 1, characterized in that, The chemical composition of the high-hardness, high-toughness tempered sorbitic wear-resistant cast steel, based on mass percentage, contains Cr, Mo, and V that satisfy the following condition: 3.0% ≤ (Cr + Mo + V) ≤ 3.6%.

4. The method for preparing the high-hardness, high-toughness, tempered martensitic wear-resistant cast steel according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are smelted, and the resulting molten steel is inoculated to obtain molten steel to be cast. S2) Casting: The molten steel obtained in step S1 is poured, solidified and cooled to obtain the casting; S3) Normalizing: After cleaning the sand from the casting obtained in step S2, heat and hold it at that temperature, then air cool it to room temperature to obtain the normalized casting. S4) Subcritical stage quenching: The normalized casting obtained in step S3 is reheated to the subcritical isothermal region, held at that temperature, and then stage quenched to room temperature to obtain the quenched casting. S5) Tempering: Temper the quenched casting obtained in step S4 and keep it at a certain temperature, then air cool it to room temperature to obtain the final product. The reheating temperature in step S4 is 800-860℃, and the holding time is 6-10 h; the graded quenching step is: first air-cooled to 290~310℃, and then air-cooled to room temperature.

5. The method for preparing high-hardness, high-toughness, tempered martensitic wear-resistant cast steel as described in claim 4, characterized in that, The heating in step S3 is to heat to 980-1050℃ and hold for 4-8 hours.

6. The method for preparing high-hardness, high-toughness, tempered martensitic wear-resistant cast steel as described in claim 4, characterized in that, The tempering process in step S5 is performed at a temperature of 570-610℃ for 6-10 hours.

7. The application of the high-hardness and toughness tempered sorbitic wear-resistant cast steel according to any one of claims 1 to 3 in the manufacture of wear-resistant parts.

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