A fine-grained, high-hardness and toughness martensitic wear-resistant cast steel and its preparation method and application

Abstract

The present invention discloses a fine-grained, high-hardness and toughness martensitic wear-resistant cast steel and its preparation method and application, belonging to the technical field of wear-resistant cast steel and its heat treatment. The chemical composition of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel is, by mass percentage, C: 0.45-0.65%, Si: 0.5-2.0%, Mn: 0.4-1.0%, Cr: 0.6-1.4%, Ni: 0.3-1.2%, Mo: 0.2-0.7%, Zr: 0.01-0.06%, P≤0.032%, S≤0.040%, the balance being Fe and unavoidable impurities, 5.5×10 ‑7 ≤[Zr][C]wt%≤35×10 ‑7 The present invention optimizes the alloy composition and heat treatment process and utilizes liquid precipitation Zr (C, N) to refine the grains. The high-hardness and toughness martensitic wear-resistant cast steel obtained is particularly suitable for the preparation of wear-resistant parts under medium and low stress impact abrasive wear conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of wear-resistant cast steel and heat treatment thereof, and particularly relates to fine-grained high-hardness and toughness martensitic wear-resistant cast steel and a preparation method and application thereof. Background Art

[0002] Impact wear is a typical cause of component failure, common in mining, metallurgy, cement, and other industries, such as excavator bucket teeth, crusher hammers and tooth plates, and ball mill liners. The development of new impact-resistant steel materials is of great significance for extending component life, reducing equipment maintenance costs, and promoting national economic development. This is consistent with the steel industry's policy of green, low-carbon, and high-quality development.

[0003] Component wear under impact wear conditions primarily stems from low-toughness fracture failure and low-strength deformation and wear failure. Therefore, materials must possess both high strength (hardness) and high toughness. Low-alloy wear-resistant steel is based on the composition of alloy structural steel and uses a quenching and low-temperature tempering process to achieve high hardness and toughness. With increasing understanding of the application limitations of high-manganese steel and high-chromium cast iron, low-alloy wear-resistant steel is gaining increasing attention among researchers both domestically and internationally.

[0004] Chinese patent CN105856725A discloses a bainite-martensite composite wear-resistant liner and its preparation method. Using a two-liquid bimetallic layered casting process, optimized alloy composition, and austempering heat treatment, the resulting composite liner features an inner layer with higher hardness and lower impact toughness, and an outer layer with lower hardness and higher impact toughness, achieving an excellent balance of hardness and toughness. However, the production process of this composite liner is complex and costly, making it difficult to implement in practical engineering applications.

[0005] Chinese patent CN105018859A discloses a wear-resistant bainitic cast steel and its preparation method. By optimizing the alloy composition and combining a secondary normalizing and austempering process, a carbide-free bainite + martensite / retained austenite structure is obtained. Because the secondary normalizing eliminates the coarse structure inheritance of the as-cast structure and refines the original austenite grains before austempering, the structure achieves a good balance of strength and toughness. However, both secondary normalizing and austempering extend the material production cycle, resulting in higher costs.

[0006] Chinese patent CN109913751A discloses a high-strength and toughness bainitic wear-resistant steel suitable for large semi-autogenous mill liners and its preparation method. By forging or rolling, the defects such as looseness and inclusions in the ingot structure are improved while the grains are refined. Combined with the heat treatment of spheroidizing annealing and water-air alternating quenching, carbide-free bainite and film-like retained austenite are obtained, thereby making the low-alloy steel exhibit excellent hardness and toughness. However, the production and preparation process of this complex phase steel includes vacuum melting, refining, forging or multi-pass rolling, multiple heat treatment processes, etc. The process path is complex, the manufacturing cost is relatively high, and it is not easy to form more complex wear-resistant parts.

[0007] In the existing technology, there is a contradiction between the hardness and toughness matching of metal materials and the production cost. Therefore, providing a metal material with simple process, low cost, good toughness and wear resistance has broad application prospects. Summary of the Invention

[0008] In order to overcome the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a fine-grained, high-hardness and high-toughness martensitic wear-resistant cast steel.

[0009] Another object of the present invention is to provide a method for preparing fine-grained, high-hardness and high-toughness martensitic wear-resistant cast steel. This wear-resistant cast steel is prepared by adding an appropriate amount of Zr to conventional low-alloy wear-resistant steel. After normalizing, quenching, and tempering, the resulting structure is primarily martensite, supplemented by a small amount of retained austenite and uniformly distributed micro- and nano-sized Zr(C,N). This structure maintains high hardness while also exhibiting good toughness, demonstrating an excellent balance of hardness and toughness. Furthermore, the preparation process for this high-hardness and high-toughness wear-resistant cast steel is simple and low-cost.

[0010] Another object of the present invention is to provide an application of the above-mentioned fine-grained, high-hardness and toughness martensitic wear-resistant cast steel, which is particularly suitable for manufacturing wear-resistant parts under medium and low stress impact abrasive wear conditions such as small and medium-sized ball mill liners, impact crusher guards, and crusher hammers.

[0011] The present invention adopts the following technical solutions:

[0012] Disclosed is a fine-grained, high-hardness and toughness martensitic wear-resistant cast steel. The chemical composition of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel, measured by mass percentage, is as follows: C: 0.45-0.65%, Si: 0.5-2.0%, Mn: 0.4-1.0%, Cr: 0.6-1.4%, Ni: 0.3-1.2%, Mo: 0.2-0.7%, Zr: 0.01-0.06%, P≤0.032%, S≤0.040%, and the balance is Fe and unavoidable impurities.

[0013] Preferably, the chemical composition of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel is, by mass percentage, C: 0.50-0.60%, Si: 1.0-1.5%, Mn: 0.5-0.7%, Cr: 0.6-0.8%, Ni: 0.3-1.1%, Mo: 0.2-0.4%, Zr: 0.02-0.05%, P≤0.023%, S≤0.038%, and the remainder is iron and unavoidable impurities.

[0014] Preferably, the chemical composition of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel is, by mass percentage, C: 0.50%, Si: 1.5%, Mn: 0.7%, Ni: 1.1%, Cr: 0.8%, Mo: 0.4%, Zr: 0.05%, P: 0.021%, S: 0.030%, and the remainder is iron and unavoidable impurities.

[0015] Preferably, the Zr and C in the chemical composition of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel meet the following conditions: 5.5×10 -7 ≤[Zr][C]wt%≤35×10 -7 .

[0016] Preferably, the Zr and C in the chemical composition of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel meet the following conditions: -7 ≤[Zr][C]wt%≤30×10 -7 .

[0017] Preferably, the hardness of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel is 51.5-58.5HRC, and the V-notch impact absorption energy is 6.2-9.6J.

[0018] A method for preparing fine-grained, high-hardness and high-toughness martensitic wear-resistant cast steel comprises the following steps:

[0019] S1) smelting: adding pig iron, scrap steel, pure iron metal and ferroalloy into an electric furnace for smelting, placing the molten steel out of the furnace into a steel ladle, and inoculating it with an inoculant zirconium-iron alloy to obtain molten steel to be poured;

[0020] S2) casting: pouring the molten steel obtained in step S1 through the pouring gate, solidifying and cooling to obtain a casting;

[0021] S3) normalizing: the casting obtained in step S2 is subjected to sand removal treatment, and then sent to a heat treatment furnace, heated, kept warm, and then air-cooled to room temperature to obtain a normalized casting;

[0022] S4) Quenching: reheating the normalized casting obtained in step S3, keeping it warm, and then placing it in a tank filled with a quenching medium to cool it to room temperature, thereby obtaining a quenched casting;

[0023] S5) Tempering: The quenched casting obtained in step S4 is sent back into a heat treatment furnace and heated to 200-300° C. for 6-18 hours, preferably 250° C. for 12 hours, and then air-cooled to room temperature.

[0024] Preferably, the preparation method of the inoculant in step S1 is as follows: the ferro-zirconium alloy is crushed into particles with a diameter of ≤5 mm by mechanical grinding, and the particles are dried, and then wrapped with iron foil to obtain the inoculant.

[0025] Preferably, the heating in step S3 is heating to 980-1080° C. and the holding time is 6-10 hours.

[0026] Preferably, the reheating temperature in step S4 is 880-980° C., and the holding time is 4-8 hours.

[0027] Preferably, the quenching medium in step S4 is PAG quenching liquid.

[0028] Preferably, the pig iron, scrap steel, pure iron metal and ferroalloy in step S1 are well-known commercial common raw materials and can be purchased from the market.

[0029] The application of the above-mentioned fine-grained, high-hardness and toughness martensitic wear-resistant cast steel in the manufacture of wear-resistant parts.

[0030] Preferably, the above-mentioned fine-grained, high-hardness and toughness martensitic wear-resistant cast steel is used in the manufacture of wear-resistant parts under medium and low stress impact abrasive wear conditions.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] The high-hardness and toughness martensitic wear-resistant cast steel produced by the present invention is obtained by adding an appropriate amount of Zr element to traditional low-alloy wear-resistant steel, combined with appropriate normalizing, quenching, and tempering heat treatment processes, to obtain a dual-phase structure composed mainly of martensite, supplemented by a small amount of residual austenite and uniformly distributed micro / nano-sized Zr(C,N). Martensite has high strength, and Zr(C,N) as a heterogeneous phase can promote the nucleation of δ-Fe, thereby refining the grains. In addition, the high melting point of Zr(C,N) can inhibit the coarsening of grains during the normalizing process. The refinement of grains can simultaneously improve the hardness and impact toughness of the material, thereby achieving a better match between the strength and toughness of the dual-phase structure. The martensitic wear-resistant steel produced by the present invention has a hardness value of 51.5-58.5HRC, and its V-notch impact absorption energy is 6.2-9.6J, which has a good hardness-toughness match and is superior to the martensitic cast steel and high-chromium cast iron currently in service.

[0033] The method for preparing the high-hardness and toughness martensitic wear-resistant cast steel provided by the present invention is simple and easy to control. The in-situ generated Zr(C,N) effectively refines the grains, resulting in a fine-grained martensitic wear-resistant cast steel with higher hardness and toughness than conventional Zr-free martensitic wear-resistant steel. Compared to high-chromium cast iron, its hardness is reduced but its toughness is significantly improved. Furthermore, the production cost is low, and it has broad application prospects.

[0034] The fine-grained, high-hardness and toughness martensitic wear-resistant cast steel produced by the present invention is particularly suitable for manufacturing wear-resistant parts under medium and low stress impact abrasive wear conditions such as small and medium-sized ball mill liners, impact crusher guard plates, and crusher hammers. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The morphology of Zr(C,N) in the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel produced in Example 2 of the present invention ( Figure 1 a) and ingredients ( Figure 1 b).

[0036] Figure 2 The fine-grained, high-hardness and toughness martensitic wear-resistant cast steel ( Figure 2 a) and comparative example 1 Zr-free martensitic wear-resistant steel ( Figure 2 b) Fracture morphology of unnotched impact specimen. DETAILED DESCRIPTION

[0037] The following is a detailed description of the present invention by way of examples. However, the scope of the present invention is not limited to the following examples, and any process parameters not specifically noted may be carried out in accordance with conventional techniques.

[0038] The raw materials used in the examples, such as pig iron, scrap steel, pure iron metal and ferroalloy, are all well-known commercial common raw materials and can be purchased from the market.

[0039] The preparation method of the inoculant ferrozirconium alloy is as follows: the ferrozirconium alloy is crushed into particles with a diameter of ≤5 mm by mechanical grinding, dried, and wrapped with iron foil.

[0040] Example 1: A fine-grained, high-hardness, and high-toughness martensitic wear-resistant cast steel

[0041] The chemical composition and mass content of the high-hardness and toughness martensitic wear-resistant cast steel are as follows: C: 0.45%, Si: 1.0%, Mn: 0.9%, Cr: 0.8%, Ni: 0.8%, Mo: 0.4%, Zr: 0.05%, P: 0.023%, S: 0.033%, and the balance is iron and unavoidable impurities, [Zr][C] wt% = 22.5×10 -7 .

[0042] The preparation method of the high-hardness and toughness martensitic wear-resistant cast steel comprises the following steps:

[0043] S1) smelting: adding pig iron, scrap steel, pure iron metal and ferroalloy into an electric furnace for smelting, placing the molten steel out of the furnace into a steel ladle, and inoculating it with ferrozirconium alloy to obtain molten steel to be poured;

[0044] S2) casting: pouring the molten steel obtained in step S1 through the pouring gate, solidifying and cooling to obtain a casting;

[0045] S3) Normalizing: The casting obtained in step S2 is subjected to sand removal treatment, and then sent to a heat treatment furnace, heated to 1080° C., kept at this temperature for 6 hours, and then air-cooled to room temperature to obtain a normalized casting;

[0046] S4) Quenching: reheating the normalized casting obtained in step S3 to 980° C., holding the temperature for 4 hours, and then placing it in a tank filled with PAG quenching liquid to cool to room temperature to obtain a quenched casting;

[0047] S5) Tempering: The quenched casting obtained in step S4 is sent back into a heat treatment furnace, heated to 250° C. and kept at this temperature for 12 h, and then air-cooled to room temperature.

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

[0049] The chemical composition and mass content of the high-hardness and toughness martensitic wear-resistant cast steel are as follows: C: 0.50%, Si: 1.5%, Mn: 0.7%, Ni: 1.1%, Cr: 0.8%, Mo: 0.4%, Zr: 0.05%, P: 0.021%, S: 0.030%, and the balance is iron and unavoidable impurities, [Zr][C] wt% = 25×10 -7 .

[0050] The preparation method of the high-hardness and toughness martensitic wear-resistant cast steel comprises the following steps:

[0051] S1) smelting: adding pig iron, scrap steel, pure iron metal and ferroalloy into an electric furnace for smelting, placing the molten steel out of the furnace into a steel ladle, and inoculating it with ferrozirconium alloy to obtain molten steel to be poured;

[0052] S2) casting: pouring the molten steel obtained in step S1 through the pouring gate, solidifying and cooling to obtain a casting;

[0053] S3) Normalizing: The casting obtained in step S2 is subjected to sand removal treatment, and then sent to a heat treatment furnace, heated to 1060° C., kept at this temperature for 6 hours, and then air-cooled to room temperature to obtain a normalized casting;

[0054] S4) Quenching: reheating the normalized casting obtained in step S3 to 960° C., keeping the temperature for 4 hours, and then placing it in a tank filled with PAG quenching liquid to cool to room temperature to obtain a quenched casting;

[0055] S5) Tempering: The quenched casting obtained in step S4 is sent back into a heat treatment furnace, heated to 250° C. and kept at this temperature for 12 h, and then air-cooled to room temperature.

[0056] Figure 1 The morphology and composition of Zr(C,N) in steel are shown. Micron-sized Zr(C,N) is mainly concentrated in the range of 2.1-4.5μm.

[0057] Example 3: A fine-grained, high-hardness and high-toughness martensitic wear-resistant cast steel

[0058] The chemical composition and mass content of the high-hardness and toughness martensitic wear-resistant cast steel are as follows: C: 0.55%, Si: 1.4%, Mn: 0.6%, Ni: 0.4%, Cr: 1.0%, Mo: 0.3%, Zr: 0.06%, P: 0.022%, S: 0.032%, and the balance is iron and unavoidable impurities, [Zr][C] wt% = 33×10 -7 .

[0059] The preparation method of the high-hardness and toughness martensitic wear-resistant cast steel comprises the following steps:

[0060] S1) smelting: adding pig iron, scrap steel, pure iron metal and ferroalloy into an electric furnace for smelting, placing the molten steel out of the furnace into a steel ladle, and inoculating it with ferrozirconium alloy to obtain molten steel to be poured;

[0061] S2) casting: pouring the molten steel obtained in step S1 through the pouring gate, solidifying and cooling to obtain a casting;

[0062] S3) Normalizing: The casting obtained in step S2 is subjected to sand removal treatment, and then sent to a heat treatment furnace, heated to 1040° C., kept at this temperature for 8 hours, and then air-cooled to room temperature to obtain a normalized casting;

[0063] S4) Quenching: reheating the normalized casting obtained in step S3 to 940° C., holding the temperature for 6 hours, and then placing it in a tank filled with PAG quenching liquid to cool to room temperature to obtain a quenched casting;

[0064] S5) Tempering: The quenched casting obtained in step S4 is sent back into a heat treatment furnace, heated to 250° C. and kept at this temperature for 12 h, and then air-cooled to room temperature.

[0065] Example 4: A fine-grained, high-hardness and toughness martensitic wear-resistant cast steel

[0066] The chemical composition and mass content of the high-hardness and toughness martensitic wear-resistant cast steel are as follows: C: 0.60%, Si: 1.4%, Mn: 0.5%, Cr: 0.7%, Ni: 0.3%, Mo: 0.2%, Zr: 0.03%, P: 0.023%, S: 0.033%, and the balance is iron and unavoidable impurities, [Zr][C] wt% = 18×10 -7 .

[0067] The preparation method of the high-hardness and toughness martensitic wear-resistant cast steel comprises the following steps:

[0068] S1) smelting: adding pig iron, scrap steel, pure iron metal and ferroalloy into an electric furnace for smelting, placing the molten steel out of the furnace into a steel ladle, and inoculating it with ferrozirconium alloy to obtain molten steel to be poured;

[0069] S2) casting: pouring the molten steel obtained in step S1 through the pouring gate, solidifying and cooling to obtain a casting;

[0070] S3) Normalizing: The casting obtained in step S2 is subjected to sand removal treatment, and then sent to a heat treatment furnace, heated to 1020° C., kept at this temperature for 10 hours, and then air-cooled to room temperature to obtain a normalized casting;

[0071] S4) Quenching: reheating the normalized casting obtained in step S3 to 920° C., holding the temperature for 6 hours, and then placing it in a tank filled with PAG quenching liquid to cool to room temperature to obtain a quenched casting;

[0072] S5) Tempering: The quenched casting obtained in step S4 is sent back into a heat treatment furnace, heated to 250° C. and kept at this temperature for 12 h, and then air-cooled to room temperature.

[0073] Example 5: A fine-grained, high-hardness and toughness martensitic wear-resistant cast steel

[0074] The chemical composition and mass content of the high-hardness and toughness martensitic wear-resistant cast steel are as follows: C: 0.65%, Si: 1.4%, Mn: 0.5%, Cr: 0.6%, Ni: 0.9%, Mo: 0.2%, Zr: 0.02%, P: 0.023%, S: 0.038%, and the balance is iron and unavoidable impurities, [Zr][C] wt% = 13×10 -7 .

[0075] The preparation method of the high-hardness and toughness martensitic wear-resistant cast steel comprises the following steps:

[0076] S1) smelting: adding pig iron, scrap steel, pure iron metal and ferroalloy into an electric furnace for smelting, placing the molten steel out of the furnace into a steel ladle, and inoculating it with ferrozirconium alloy to obtain molten steel to be poured;

[0077] S2) casting: pouring the molten steel obtained in step S1 through the pouring gate, solidifying and cooling to obtain a casting;

[0078] S3) Normalizing: The casting obtained in step S2 is subjected to sand removal treatment, and then sent into a heat treatment furnace, heated to 1000° C., kept at this temperature for 10 hours, and then air-cooled to room temperature to obtain a normalized casting;

[0079] S4) Quenching: reheating the normalized casting obtained in step S3 to 900°C, keeping the temperature for 8 hours, and then placing it in a tank filled with PAG quenching liquid to cool to room temperature to obtain a quenched casting;

[0080] S5) Tempering: The quenched casting obtained in step S4 is sent back into a heat treatment furnace, heated to 250° C. and kept at this temperature for 12 h, and then air-cooled to room temperature.

[0081] Comparative Example 1: Zr-free quenched martensitic wear-resistant cast steel

[0082] The chemical composition and mass content of the Zr-free quenched martensitic wear-resistant cast steel are: C: 0.50%, Si: 1.4%, Mn: 0.7%, Ni: 1.0%, Cr: 0.8%, Mo: 0.3%, P: 0.023%, S: 0.032%, and the balance is iron and unavoidable impurities, [Zr][C]wt%=0.

[0083] The preparation method of the Zr-free quenched martensitic wear-resistant cast steel comprises the following steps:

[0084] S1) smelting: adding pig iron, scrap steel, pure iron metal and ferroalloy into an electric furnace for smelting, placing the molten steel out of the furnace into a steel ladle, and inoculating it with ferrozirconium alloy to obtain molten steel to be poured;

[0085] S2) casting: pouring the molten steel obtained in step S1 through the pouring gate, solidifying and cooling to obtain a casting;

[0086] S3) Normalizing: The casting obtained in step S2 is subjected to sand removal treatment, and then sent to a heat treatment furnace, heated to 1060° C., kept at this temperature for 6 hours, and then air-cooled to room temperature to obtain a normalized casting;

[0087] S4) Quenching: reheating the normalized casting obtained in step S3 to 960° C., holding the temperature for 8 hours, and then placing it in a tank filled with PAG quenching liquid to cool to room temperature to obtain a quenched casting;

[0088] S5) Tempering: The quenched casting obtained in step S4 is sent back into a heat treatment furnace, heated to 250° C. and kept at this temperature for 12 h, and then air-cooled to room temperature.

[0089] Comparative Example 2

[0090] The chemical composition and mass content of the martensitic wear-resistant cast steel are as follows: C: 0.45%, Si: 1.1%, Mn: 0.9%, Cr: 0.8%, Ni: 0.8%, Mo: 0.4%, Zr: 0.07%, P: 0.022%, S: 0.032%, and the balance is iron and unavoidable impurities, [Zr][C] wt% = 31.5×10 -7 .

[0091] The preparation method of the martensitic wear-resistant cast steel comprises the following steps:

[0092] S1) smelting: adding pig iron, scrap steel, pure iron metal and ferroalloy into an electric furnace for smelting, placing the molten steel out of the furnace into a steel ladle, and inoculating it with ferrozirconium alloy to obtain molten steel to be poured;

[0093] S2) casting: pouring the molten steel obtained in step S1 through the pouring gate, solidifying and cooling to obtain a casting;

[0094] S3) Normalizing: The casting obtained in step S2 is subjected to sand removal treatment, and then sent to a heat treatment furnace, heated to 1080° C., kept at this temperature for 6 hours, and then air-cooled to room temperature to obtain a normalized casting;

[0095] S4) Quenching: reheating the normalized casting obtained in step S3 to 980° C., holding the temperature for 4 hours, and then placing it in a tank filled with PAG quenching liquid to cool to room temperature to obtain a quenched casting;

[0096] S5) Tempering: The quenched casting obtained in step S4 is sent back into a heat treatment furnace, heated to 250° C. and kept at this temperature for 12 h, and then air-cooled to room temperature.

[0097] Material performance test of embodiments and comparative examples

[0098] Experimental method: The performance test of the cast steel prepared in Examples 1-5 and Comparative Examples 1-2 was carried out. The impact test adopted the V-notch impact test. Before the Rockwell hardness test, the test surface of the sample was ground and polished. The impact abrasive wear test was carried out on an MLD-10 dynamic load abrasive wear testing machine. The wear impact energy was 1.0J, the impact frequency was 100 times per minute, the lower sample was 45# steel, the rotation speed was 100 revolutions per minute, the abrasive used in the test was quartz sand with a particle size between 60 and 80 meshes, and the flow rate of the abrasive was controlled at about 50kg per hour. Each group of samples needed to be pre-ground for 30 minutes before the test. During the impact wear process, the weight loss was measured once with 30 minutes as a wear cycle, and a total of five cycles were carried out, totaling 2.5 hours.

[0099] The test results are listed in Table 1.

[0100] Table 1 Performance test results

[0101]

[0102] The hardness in Table 1 is the average of 10 values, and the V-notch impact absorption energy and wear weight loss are the average of 3 values.

[0103] It can be concluded from Table 1 that the hardness of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel produced by the present invention can reach 51.5 to 58.5 HRC, while the V-notch impact absorption energy reaches 6.2 to 9.6 J, with a good hardness and toughness ratio. Under similar components and the same process, the hardness and V-notch impact absorption energy of Example 2 (containing Zr) are respectively increased by about 8.4% (4.3 HRC) and 45% (2.7 J) compared with Comparative Example 1 (without Zr). Figure 2 As shown, a large number of equiaxed dimples can be observed in the impact fracture of Example 2, while the number of dimples in the impact fracture of Comparative Example 1 is significantly reduced.

[0104] The obvious difference between the present invention and the existing low-alloy wear-resistant steel is that the steel contains an appropriate amount of Zr. By optimizing the ratio of Zr and C elements and the normalizing heat treatment process, a complex phase structure with fine grains, a small amount of residual austenite and uniformly distributed micro / nano Zr(C,N) can be obtained. Zr(C,N) as a heterogeneous phase can promote the nucleation of δ-Fe, thereby refining the grains. In addition, the high melting point of Zr(C,N) can inhibit the coarsening of grains during heat treatment. Grain refinement can simultaneously improve the hardness and impact toughness of the material, and high-hardness Zr(C,N) can improve the hardness of the material, but the lower Zr content or [Zr][C]wt% value results in a small number of precipitated Zr(C,N) phases and a weaker heterogeneous nucleation effect. Excessively high Zr content or [Zr][C] wt% value, as shown in Comparative Example 2 in Table 1, leads to the precipitation of larger-sized Zr(C,N) phases. Large-sized Zr(C,N) will split the matrix and cause a sharp decrease in the toughness of the material.

[0105] By optimizing the composition and heat treatment process, the present invention achieves low-alloy steel that maintains high hardness while maintaining good toughness at a low production cost. This overcomes the conflict between the hardness-toughness balance and production costs of existing metal materials in low- to medium-stress impact abrasive wear conditions. This Zr-containing martensitic steel, combining high hardness with good impact toughness, exhibits superior wear resistance compared to conventional Zr-free martensitic steel in low- to medium-impact abrasive wear tests. It is particularly suitable for manufacturing wear-resistant parts subjected to low- to medium-stress impact abrasive wear conditions, such as liners for small and medium-sized ball mills, guard plates for impact crushers, and hammer heads for crushers.

[0106] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A fine-grained, high-hardness and toughness martensitic wear-resistant cast steel, characterized in that: The chemical composition of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel is, by mass percentage, C: 0.45-0.65%, Si: 0.5-2.0%, Mn: 0.4-1.0%, Cr: 0.6-1.4%, Ni: 0.3-1.2%, Mo: 0.2-0.7%, Zr: 0.01-0.06%, P ≤ 0.032%, S ≤ 0.040%, and the balance is Fe and unavoidable impurities; The chemical composition of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel satisfies the following conditions: 5.5×10 -7 ≤[Zr][C] wt% ≤35×10 -7 ; The hardness of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel is 51.5-58.5HRC, and the V-notch impact absorption energy is 6.2-9.6J.

2. The fine-grained, high-hardness and high-toughness martensitic wear-resistant cast steel according to claim 1, characterized in that: The chemical composition of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel is, by mass percentage, C: 0.50-0.60%, Si: 1.0-1.5%, Mn: 0.5-0.7%, Cr: 0.6-0.8%, Ni: 0.3-1.1%, Mo: 0.2-0.4%, Zr: 0.02-0.05%, P≤ 0.023%, S≤ 0.038%, and the remainder is iron and unavoidable impurities.

3. The fine-grained, high-hardness and high-toughness martensitic wear-resistant cast steel according to claim 1, characterized in that: The chemical composition of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel satisfies the following conditions: -7 ≤[Zr][C] wt%≤30×10 -7 .

4. The method for preparing the fine-grained, high-hardness and high-toughness martensitic wear-resistant cast steel according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloy are added to an electric furnace for smelting. The molten steel from the furnace is placed in a steel ladle and inoculated with an inoculant, ferrozirconium alloy, to obtain molten steel to be poured; S2) Casting: pouring the molten steel obtained in step S1 through the pouring gate, solidifying and cooling to obtain a casting; S3) Normalizing: The casting obtained in step S2 is subjected to sand removal treatment, and then sent to a heat treatment furnace for heating, insulation, and air cooling to room temperature to obtain a normalized casting; S4) Quenching: reheating the normalized casting obtained in step S3, keeping it warm, and then placing it in a tank containing a quenching medium to cool it to room temperature, thereby obtaining a quenched casting; S5) Tempering: The quenched casting obtained in step S4 is placed in a heat treatment furnace again, heated to 200-300°C for 6-18 hours, and air-cooled to room temperature.

5. The method for preparing high hardness and toughness martensitic wear-resistant cast steel according to claim 4, characterized in that: The preparation method of the inoculant in step S1 is as follows: the ferro-zirconium alloy is crushed into particles with a diameter of ≤5 mm by mechanical grinding, and the particles are dried, and then wrapped with iron foil to obtain the inoculant.

6. The method for preparing high hardness and toughness martensitic wear-resistant cast steel according to claim 4, characterized in that: The heating in step S3 is heating to 980-1080° C. and keeping the temperature for 6-10 h.

7. The method for preparing high hardness and toughness martensitic wear-resistant cast steel according to claim 4, characterized in that: The reheating temperature in step S4 is 880-980° C., and the holding time is 4-8 h.

8. The method for preparing high hardness and toughness martensitic wear-resistant cast steel according to claim 4, characterized in that: The quenching medium in step S4 is PAG quenching liquid.

9. Use of the high hardness and toughness martensitic wear-resistant cast steel according to any one of claims 1 to 3 in the manufacture of wear-resistant parts.

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