Fine-grain high-hardness and high-toughness martensite wear-resistant cast steel as well as preparation method and application thereof

Abstract

The invention discloses fine-grain high-hardness and high-toughness martensite wear-resistant cast steel as well as a preparation method and application thereof, and belongs to the technical field of wear-resistant cast steel and heat treatment thereof. The fine-grain high-hardness and high-toughness martensite wear-resistant cast steel comprises the following chemical components in percentage by mass: 0.45-0.65% of C, 0.5-2.0% of Si, 0.4-1.0% of Mn, 0.6-1.4% of Cr, 0.3-1.2% of Ni, 0.2-0.7% of Mo, 0.01-0.06% of Zr, less than or equal to 0.032% of P, less than or equal to 0.040% of S and the balance of Fe and inevitable impurities, and [Zr] [C] wt% is more than or equal to 5.5 * 10 <-7 > and less than or equal to 35 * 10 <-7 >. The high-hardness and high-toughness martensite wear-resistant cast steel obtained by optimizing alloy components and a heat treatment process and refining grains by utilizing liquation Zr (C, N) is particularly suitable for preparing wear-resistant parts under the working condition of medium-low stress impact abrasive wear.

Description

Technical Field

[0001] The invention belongs to the technical field of wear-resistant cast steel and heat treatment thereof, and specifically 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 way to cause component failure, which is common in mining, metallurgy, cement and other fields, such as bucket teeth of excavators, hammer heads and tooth plates of crushers, and linings of ball mills. The direct economic losses caused by impact wear in the mining machinery industry alone amount to hundreds of billions of yuan each year. The development of new impact-resistant abrasive wear steel materials is of great significance to extending the service life of components, reducing equipment maintenance costs, and promoting national economic construction, which is in line with the policy of green, low-carbon and high-quality development of the steel industry.

[0003] The loss of components under impact wear conditions mainly comes from low-toughness fracture failure and low-strength deformation and wear failure. Therefore, the material needs to have both high strength (hardness) and high toughness. Low-alloy wear-resistant steel is based on the composition of alloy structural steel and adopts quenching + low-temperature tempering process to obtain higher hardness and toughness. With the deepening of the understanding of the application limitations of high manganese steel and high chromium cast iron, low-alloy wear-resistant steel has received more and more attention from domestic and foreign scientific researchers.

[0004] Chinese patent CN105856725A discloses a bainite-martensite composite wear-resistant lining plate and its preparation method. By adopting a two-liquid bimetallic layered casting process, optimizing the alloy composition and isothermal quenching heat treatment process, a composite lining plate with a higher inner layer hardness / lower impact toughness and a lower outer layer hardness / higher impact toughness is obtained, achieving an excellent combination of liner hardness and toughness. However, the production process of the composite lining plate is complex and the cost is high, making it difficult to promote in actual engineering applications.

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

[0006] Chinese patent CN109913751A discloses a high-strength and tough bainite wear-resistant steel suitable for large semi-autogenous mill liners and its preparation method. Through forging or rolling, the defects such as looseness and inclusions inside the ingot structure are improved while the grains are refined, and then combined with spheroidizing annealing and water-air alternating quenching heat treatment methods, carbide-free bainite and film-like residual austenite are obtained, thereby making the low-alloy steel present 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 complicated, the manufacturing cost is relatively high, and it is not easy to form more complex wear-resistant parts.

[0007] In the prior art, there is a contradiction between the hardness-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 toughness martensitic wear-resistant cast steel, wherein the wear-resistant cast steel is prepared by adding an appropriate amount of Zr to conventional low-alloy wear-resistant steel, and after normalizing, quenching and tempering heat treatment, a composite structure is obtained which is mainly martensite, supplemented by a small amount of residual austenite and uniformly distributed micro / nano-sized Zr (C, N). The composite structure has good toughness while maintaining high hardness, and exhibits a good combination of hardness and toughness. In addition, the preparation process of the high-hardness and 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 guard plates, and crusher hammers.

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

[0012] A fine-grained, high-hardness and toughness martensitic wear-resistant cast steel has the following chemical compositions, 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 remainder 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 value 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 performing inoculation treatment 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 a 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 into 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 the temperature, and then placing it in a tank containing a quenching medium to cool it to room temperature to obtain a quenched casting;

[0023] S5) Tempering: The quenched casting obtained in step S4 is sent to the heat treatment furnace again, and heated to 200-300° C. for 6-18 hours, preferably 250° C. for 12 hours, and 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 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 insulation 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 above-mentioned fine-grained, high-hardness and high-toughness martensitic wear-resistant cast steel is used in the manufacture of wear-resistant parts.

[0030] Preferably, the above-mentioned fine-grained high-hardness and high-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 prepared by the present invention is obtained by adding an appropriate amount of Zr element on the basis of traditional low-alloy wear-resistant steel, combining appropriate normalizing, quenching and tempering heat treatment processes, and obtaining a multiphase structure mainly composed 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 normalizing. The refinement of grains can simultaneously improve the hardness and impact toughness of the material, thereby making the strength and toughness of the multiphase structure better matched. The hardness value of the martensitic wear-resistant steel prepared by the present invention is 51.5-58.5HRC, and its V-notch impact absorption energy is 6.2-9.6J, which has good hardness and toughness matching, and is better than the currently in-service martensitic cast steel and high chromium cast iron.

[0033] The preparation method of 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) can effectively refine the grains, so that the hardness and toughness of the prepared fine-grained martensitic wear-resistant cast steel are higher than those of the traditional Zr-free martensitic wear-resistant steel. Compared with high-chromium cast iron, its hardness is reduced but its toughness is significantly improved. At the same time, the production cost is low and it has a wide range of application prospects.

[0034] The fine-grained, high-hardness and toughness martensitic wear-resistant cast steel prepared by the 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 further explanation of the present invention through specific implementations in the form of examples. However, the scope of the above subject matter of the present invention is not limited to the following examples, and for process parameters not specifically noted, conventional techniques can be used.

[0038] The raw materials used in the embodiments, 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 ferro-zirconium alloy is as follows: the ferro-zirconium 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 performing inoculation treatment with zirconium-iron alloy to obtain molten steel to be poured;

[0044] S2) casting: pouring the molten steel obtained in step S1 through a 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 into 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, 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;

[0047] S5) Tempering: The quenched casting obtained in step S4 is sent to the heat treatment furnace again, and heated to 250° C. and kept warm for 12 hours, and then air-cooled to room temperature.

[0048] Example 2: A fine-grained, high-hardness and high-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 performing inoculation treatment with zirconium-iron alloy to obtain molten steel to be poured;

[0052] S2) casting: pouring the molten steel obtained in step S1 through a 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 into 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 it to room temperature to obtain a quenched casting;

[0055] S5) Tempering: The quenched casting obtained in step S4 is sent to the heat treatment furnace again, and heated to 250° C. and kept warm for 12 hours, and then air-cooled to room temperature.

[0056] Figure 1 It shows the morphology and composition of Zr(C,N) in steel. The micron-scale 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 performing inoculation treatment with zirconium-iron alloy to obtain molten steel to be poured;

[0061] S2) casting: pouring the molten steel obtained in step S1 through a 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 into 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, keeping the temperature for 6 hours, and then placing it in a tank filled with PAG quenching liquid to cool it to room temperature to obtain a quenched casting;

[0064] S5) Tempering: The quenched casting obtained in step S4 is sent to the heat treatment furnace again, and heated to 250° C. and kept warm for 12 hours, and then air-cooled to room temperature.

[0065] Example 4: A fine-grained, high-hardness and high-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 performing inoculation treatment with zirconium-iron alloy to obtain molten steel to be poured;

[0069] S2) casting: pouring the molten steel obtained in step S1 through a 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 into 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., keeping the temperature for 6 hours, and then placing it in a tank filled with PAG quenching liquid to cool it to room temperature to obtain a quenched casting;

[0072] S5) Tempering: The quenched casting obtained in step S4 is sent to the heat treatment furnace again, and heated to 250° C. and kept warm for 12 hours, and then air-cooled to room temperature.

[0073] Example 5: A fine-grained, high-hardness and high-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 performing inoculation treatment with zirconium-iron alloy to obtain molten steel to be poured;

[0077] S2) casting: pouring the molten steel obtained in step S1 through a 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 into a tank filled with PAG quenching liquid to cool it to room temperature to obtain a quenched casting;

[0080] S5) Tempering: The quenched casting obtained in step S4 is sent to the heat treatment furnace again, and heated to 250° C. and kept warm for 12 hours, 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 remainder 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 performing inoculation treatment with zirconium-iron alloy to obtain molten steel to be poured;

[0085] S2) casting: pouring the molten steel obtained in step S1 through a 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 into 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., keeping the temperature for 8 hours, and then placing it in a tank filled with PAG quenching liquid to cool it to room temperature to obtain a quenched casting;

[0088] S5) Tempering: The quenched casting obtained in step S4 is sent to the heat treatment furnace again, and heated to 250° C. and kept warm for 12 hours, 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 remainder 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 performing inoculation treatment with zirconium-iron alloy to obtain molten steel to be poured;

[0093] S2) casting: pouring the molten steel obtained in step S1 through a 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 into 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, keeping the temperature for 4 hours, and then placing it in a tank filled with PAG quenching liquid to cool it to room temperature to obtain a quenched casting;

[0096] S5) Tempering: The quenched casting obtained in step S4 is sent to the heat treatment furnace again, and heated to 250° C. and kept warm for 12 hours, and then air-cooled to room temperature.

[0097] Examples and Comparative Examples Material Performance Tests

[0098] Experimental method: The performance test of the cast steel prepared in Examples 1-5 and Comparative Examples 1-2 was carried out using a V-notch impact test. The test surface of the sample was ground and polished before the Rockwell hardness test. The impact abrasive wear test was carried out on an MLD-10 dynamic abrasive wear tester. 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 tested 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 needs 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 51.5-58.5HRC, and at the same time, the V-notch impact absorption energy reaches 6.2-9.6J, 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% (4.3HRC) and 45% (2.7J) 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 the Zr content or [Zr][C] wt% value, the less amount of precipitated Zr (C, N) phase, and the weaker heterogeneous nucleation effect. Too high Zr content or [Zr][C] wt% value, as shown in Comparative Example 2 in Table 1, leads to the precipitation of larger Zr(C,N) phases. Large Zr(C,N) will split the matrix and cause the toughness of the material to drop sharply.

[0105] The invention optimizes the composition and heat treatment process to make the low alloy steel have good toughness while maintaining high hardness, and the production cost is low, which overcomes the contradiction between the hardness and toughness matching of existing metal materials and the production cost under medium and low stress impact abrasive wear conditions. Zr-containing martensitic steel with high hardness and good impact toughness shows better wear resistance than traditional Zr-free martensitic steel in medium and low impact abrasive wear tests, and 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.

[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 equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A fine-grained, high-hardness and high-toughness martensitic wear-resistant cast steel, characterized in that: Measured in percentage by mass, the chemical composition of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel is: 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 remainder is Fe and unavoidable impurities.

2. The fine-grained, high-hardness and high-toughness martensitic wear-resistant cast steel according to claim 1, characterized in that: Measured by mass percentage, the chemical composition of the fine-grained, high-hardness and toughness martensitic wear-resistant cast steel is: 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 as claimed in 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: 5.5×10 -7 ≤[Zr][C]wt%≤35×10 -7 .

4. The fine-grained, high-hardness and high-toughness martensitic wear-resistant cast steel according to claim 3, 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 .

5. 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 4, characterized in that: The following steps are involved: 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 performing inoculation treatment with an inoculant zirconium-iron alloy to obtain molten steel to be poured; S2) casting: pouring the molten steel obtained in step S1 through a 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 into a heat treatment furnace, heated, kept warm, and then air-cooled to room temperature to obtain a normalized casting; S4) quenching: reheating the normalized casting obtained in step S3, keeping the temperature, and then placing it in a tank containing a quenching medium to cool it to room temperature to obtain a quenched casting; S5) Tempering: The quenched casting obtained in step S4 is sent to the heat treatment furnace again, and heated to 200-300° C. for 6-18 hours, and air-cooled to room temperature.

6. The method for preparing the high hardness and toughness martensitic wear-resistant cast steel as claimed in claim 5, 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 dried, and then wrapped with iron foil to obtain the inoculant.

7. The method for preparing the high hardness and toughness martensitic wear-resistant cast steel as claimed in claim 5, characterized in that: The heating in step S3 is heating to 980-1080° C., and the heat preservation time is 6-10 hours.

8. The method for preparing the high hardness and toughness martensitic wear-resistant cast steel as claimed in claim 5, characterized in that: The reheating temperature in step S4 is 880-980° C., and the insulation time is 4-8 hours.

9. The method for preparing the high hardness and toughness martensitic wear-resistant cast steel as claimed in claim 5, characterized in that: The quenching medium in step S4 is PAG quenching liquid.

10. Use of the high hardness and toughness martensitic wear-resistant cast steel according to any one of claims 1 to 4 in the manufacture of wear-resistant parts.

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