High-hardness and high-toughness abrasion-resistant cast steel and preparation method and application thereof

Abstract

The application belongs to the technical field of wear-resistant cast steel, and discloses a high-hard-tough wear-resistant cast steel and a preparation method and application thereof.The chemical composition of the high-hard-tough wear-resistant cast steel comprises, in percentage by mass, C: 0.20-0.45%, Si: 1.0-2.3%, Mn: 0.4-0.9%, Cr: 0.6-1.4%, Ni: 0.8-1.8%, Mo: 0.2-0.6%, Cu: 0.5-1.5%, RE: 0.03-0.08%, P≤0.032%, S≤0.040%, and the balance of Fe and inevitable impurities; Si / C≥4.2, and 1.4%≤(Ni+Cu)≤2.8%. The cast steel prepared by optimizing the alloy composition and the heat treatment process has high hardness, excellent toughness and corrosion resistance, the preparation process of the high-hard-tough wear-resistant cast steel is simple, the cost is low, and the high-hard-tough wear-resistant cast steel has a good application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wear-resistant cast steel, and particularly relates to a high-hardness and high-toughness wear-resistant cast steel as well as a preparation method and application thereof. BACKGROUND

[0002] Impact-abrasive wear is a very harsh wear condition. Mechanical parts, such as the digging teeth of a tunneling machine, the hammer heads and tooth plates of a crusher, and the lining plates of a ball mill, will be subjected to impact load and abrasive wear simultaneously during work. The direct economic loss caused by impact-abrasive wear in the mining machinery industry alone is as high as tens of billions of yuan per year. Related research shows that the failure of parts under impact-abrasive wear conditions is mainly caused by low toughness fracture and low strength deformation and wear failure. Therefore, steel materials with excellent strength and toughness are widely used as impact-abrasive wear-resistant parts. At present, a large number of studies have been carried out on the relationship between the alloy composition, heat treatment process, microstructure, and impact-abrasive wear performance of steel materials, and various impact-abrasive wear-resistant steels have been developed. However, the service conditions of many wear-resistant parts are corrosive, and the safety and service life of the parts are affected by the combined action of corrosion and impact-abrasive wear. At the same time, a large number of studies have pointed out that the corrosion-wear resistance of materials is quite different from their wear resistance. Therefore, the development of impact-corrosion-abrasive wear-resistant steel materials has gradually attracted attention in the field of wear-resistant steel.

[0003] Chinese Patent CN111549277A discloses a martensitic wear-resistant steel plate resistant to atmospheric corrosion and a manufacturing method thereof. Chinese Patent CN108930001A discloses a high-hardness wear-resistant steel plate for slurry dredging and a production method thereof. Chinese Patent CN110387507A discloses an HB500-grade wear-resistant steel for corrosive slurry transport containers and a production method thereof. Chinese Patent CN117684100A discloses a heat treatment-free martensitic wear-resistant steel and a manufacturing method thereof. Chinese Patent CN113025888B discloses a wear-resistant high-strength steel and a preparation method thereof. The above-mentioned five kinds of steels have excellent wear resistance and corrosion resistance. However, their production processes all include vacuum melting, refining, forging or multi-pass rolling, etc., and the process path is complex, the production cycle is long, the energy consumption is large, and it is not easy to form complex wear-resistant parts.

[0004] Chinese Patent CN109825774B discloses a preparation method of a Bemaao multiphase wear-resistant steel. Although the preparation process of castings is involved, the composition contains up to 3.5% Mn (mass fraction). Mn is easy to oxidize, so the early smelting process also involves vacuum melting and refining, resulting in a significant increase in production cost.

[0005] There is a contradiction between wear resistance, corrosion resistance and production cost of steel materials in the prior art. Therefore, it has a broad application prospect to provide a steel material with simple process, low cost, good wear resistance and corrosion resistance. SUMMARY

[0006] In order to overcome the defects and shortcomings of the prior art, the primary purpose of the present application is to provide a high hard and tough wear-resistant and corrosion-resistant cast steel.

[0007] Another purpose of the present application is to provide a preparation method of the high hard and tough wear-resistant and corrosion-resistant cast steel. The high hard and tough wear-resistant and corrosion-resistant cast steel is obtained by adding appropriate amounts of Si, Cu and Ni on the basis of traditional low-alloy wear-resistant steel, and then performing normalizing, isothermal quenching and tempering heat treatment, so as to obtain a complex phase structure mainly composed of martensite and a small amount of metastable residual austenite. The complex phase structure has high hardness and good toughness, and has good corrosion resistance. In addition, the preparation process of the high hard and tough wear-resistant and corrosion-resistant cast steel is simple and low in cost.

[0008] Still another purpose of the present application is to provide the application of the high hard and tough wear-resistant and corrosion-resistant cast steel, which is especially suitable for manufacturing parts applied to medium and high stress impact corrosion and abrasive wear conditions, such as large ball mill liner, impact crusher guard plate, crusher hammer and the like.

[0009] The present application adopts the following technical scheme:

[0010] A high hard and tough wear-resistant and corrosion-resistant cast steel, the chemical composition of the high hard and tough wear-resistant and corrosion-resistant cast steel comprises, by mass percentage, C: 0.20-0.45%, Si: 1.0-2.3%, Mn: 0.4-0.9%, Cr: 0.6-1.4%, Ni: 0.8-1.8%, Mo: 0.2-0.6%, Cu: 0.5-1.5%, RE: 0.03-0.08%, P≤0.032%, S≤0.040%, and the balance is Fe and inevitable impurities, and Si / C≥4.2, 1.4%≤(Ni+Cu)≤2.8%.

[0011] Preferably, the chemical composition of the high hard and tough wear-resistant and corrosion-resistant cast steel comprises, by mass percentage, C: 0.25-0.35%, Si: 1.4-1.8%, Mn: 0.5-0.8%, Ni: 0.9-1.0%, Cr: 0.7-0.8%, Mo: 0.3-0.4%, Cu: 0.7-1.0%, RE: 0.05%, P: 0.022-0.024%, S: 0.032-0.035%, and the balance is Fe and inevitable impurities, Si / C≥4.7, 1.5%≤(Ni+Cu)≤2.5%.

[0012] Preferably, the high hard and tough abrasion-resistant cast steel has a chemical composition, in terms of mass percentage, of C: 0.35%, Si: 1.8%, Mn: 0.5%, Ni: 1.0%, Cr: 0.7%, Mo: 0.3%, Cu: 1.0%, RE: 0.05%, P: 0.022%, S: 0.032%, and the balance being iron and inevitable impurities.

[0013] Preferably, the high hard and tough abrasion-resistant cast steel has a hardness of 431-554 HV, a V-notch impact energy of 16.4-30.1 J, and an anti-corrosion wear performance that is 47.8% and 81.1% higher than that of traditional martensitic steel and high manganese steel, respectively.

[0014] Preferably, the high hard and tough abrasion-resistant cast steel is mainly composed of martensite and a small amount of metastable residual austenite.

[0015] A preparation method of a high hard and tough abrasion-resistant cast steel, comprising the following steps:

[0016] S1) smelting: smelting pig iron, scrap steel, pure iron metal, and iron alloy, and subjecting the smelted steel liquid to inoculation modification treatment with a rare earth alloy to obtain a steel liquid to be poured;

[0017] S2) casting: pouring the steel liquid to be poured obtained in step S1 through a pouring gate to obtain a casting after solidification and cooling;

[0018] S3) normalizing: subjecting the casting obtained in step S2 to sand cleaning treatment, then heating, and after holding, air cooling to room temperature to obtain a normalized casting;

[0019] S4) isothermal quenching: re-heating the normalized casting obtained in step S3, holding, then isothermal quenching and holding, and then air cooling to room temperature to obtain an isothermal quenched casting;

[0020] S5) tempering: re-tempering the isothermal quenched casting obtained in step S4, and then air cooling to room temperature to obtain the high hard and tough abrasion-resistant cast steel.

[0021] Preferably, the heating in step S3 is heating to 950-1050℃, and the holding time is 4-8h.

[0022] Preferably, the re-heating in step S4 is at a temperature of 940-980℃, and the holding time is 4-8h.

[0023] Preferably, the isothermal quenching in step S4 is at a temperature of 200-260℃, and the holding time is 2-6h.

[0024] Preferably, the isothermal quenching in step S4 is salt bath isothermal quenching, and the salt bath medium is composed of NaNO2 and KNO3, more preferably 45% NaNO2 and 55% KNO3.

[0025] Preferably, the temperature of the tempering treatment in step S5 is 180-240 DEG C, and the holding time is 4-10h.

[0026] Preferably, the pig iron, scrap steel, pure iron metal and iron alloy in step S1 are known commercial ordinary raw materials, and can be purchased from the market.

[0027] Application of the high-hardness and high-toughness abrasion-resistant and corrosion-resistant cast steel in manufacturing abrasion-resistant parts or corrosion-resistant parts.

[0028] Preferably, the high-hardness and high-toughness abrasion-resistant and corrosion-resistant cast steel is applied in manufacturing abrasion-resistant parts under medium-high stress impact corrosion and abrasive wear working conditions.

[0029] Compared with the prior art, the application has the following advantages and beneficial effects:

[0030] The high-hardness and high-toughness martensitic abrasion-resistant and corrosion-resistant cast steel prepared by the application is based on traditional low-alloy abrasion-resistant steel, and a proper amount of Si, Cu and Ni elements are added, and a normalizing, isothermal quenching and tempering heat treatment process is combined to obtain a complex phase structure mainly composed of martensite and a small amount of metastable residual austenite. The martensite has high strength, and the transformation induced plasticity (TRIP effect) of the metastable residual austenite can make the material have good toughness. In addition, Si can inhibit the precipitation of carbides, reduce the heterogeneous phase in the structure, slow down the galvanic corrosion and improve the corrosion resistance of the material. The addition of Cu and Ni elements can reduce the corrosion current density of the material, thereby improving the corrosion resistance of the material.

[0031] The high-hardness and high-toughness martensitic abrasion-resistant and corrosion-resistant cast steel prepared by the application has a hardness of 431-554 HV and a V-shaped notch impact absorption energy of 16.4-30.1 J, has good matching of hardness and toughness, and the corrosion and wear resistance is improved by 47.8% and 81.1% respectively compared with traditional martensitic steel and high manganese steel.

[0032] The preparation method of the high-hardness and high-toughness martensitic abrasion-resistant and corrosion-resistant cast steel provided by the application is simple and easy to control. Only by optimizing the alloy composition and the heat treatment process based on the traditional low-alloy abrasion-resistant steel, a steel material with good wear resistance and corrosion resistance can be prepared. At the same time, the production cost is low, and the application prospect is wide.

[0033] The high-hardness and high-toughness martensitic abrasion-resistant and corrosion-resistant cast steel prepared by the application is especially suitable for manufacturing parts under medium-high stress impact corrosion and abrasive wear working conditions, such as large-scale ball mill lining plates, impact crusher guard plates and crusher hammers for mines. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1SEM image of the microstructure of the high hard tough martensitic erosion resistant cast steel produced in Example 4 of the present application.

[0035] Figure 2 SEM image of the microstructure of the conventional martensitic erosion resistant cast steel produced in Comparative Example 3 of the present application.

[0036] Figure 3 Tafel polarization curve of the microstructure of the cast steel produced in Example 4 and Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0037] The above subject matter of the present application will be further explained by way of specific embodiments in the form of examples. However, the scope of the above subject matter of the present application is not limited only to the following examples, and for the process parameters not specifically mentioned, the conventional techniques can be referred to.

[0038] The raw iron, scrap steel, pure iron metal and iron alloy and other raw materials used in the examples are all known commercial ordinary raw materials, which can be purchased from the market.

[0039] Example 1, a high hard tough martensitic erosion resistant cast steel

[0040] The chemical composition and mass content of the high hard tough martensitic erosion resistant cast steel are as follows: C: 0.20%, Si: 1.0%, Mn: 0.9%, Cr: 1.2%, Ni: 0.8%, Mo: 0.4%, Cu: 0.7%, RE: 0.06%, P: 0.025%, S: 0.035%, the balance being iron and unavoidable impurities, Si / C = 5, (Ni + Cu) = 1.5%.

[0041] The preparation method of the high hard tough martensitic erosion resistant cast steel comprises the following steps:

[0042] S1) smelting: raw iron, scrap steel, pure iron metal and iron alloy are added to an electric furnace for smelting, and the molten steel is placed in a steel ladle, and a rare earth alloy is used for inoculation modification treatment to obtain a molten steel to be poured;

[0043] S2) casting: the molten steel to be poured obtained in step S1 is poured through a pouring gate, and a casting is obtained by solidification and cooling;

[0044] S3) normalizing: the casting obtained in step S2 is subjected to sand cleaning treatment, and then is sent to a heat treatment furnace, heated to 1050°C, and after holding for 8h, air cooled to room temperature to obtain a normalized casting;

[0045] S4) isothermal quenching: the normalized casting obtained in step S3 is reheated to 980°C, held for 6h, and then sent to a 260°C salt bath furnace for isothermal quenching for 2h, the salt bath medium is composed of 45% NaNO2 and 55% KNO3, and then air cooled to room temperature again to obtain an isothermally quenched casting;

[0046] S5) tempering: the quenched castings obtained in step S4 are again put into a heat treatment furnace and heated to 240℃ for 6h, and air-cooled to room temperature to obtain the castings.

[0047] Example 2, a high-hardness and high-toughness martensitic erosion-resistant cast steel

[0048] The chemical composition and mass content of the high-hardness and high-toughness martensitic erosion-resistant cast steel are as follows: C: 0.25%, Si: 1.4%, Mn: 0.8%, Cr: 1.0%, Ni: 1.0%, Mo: 0.4%, Cu: 0.7%, RE: 0.05%, P: 0.024%, S: 0.035%, and the balance being iron and inevitable impurities, Si / C = 5.6, and (Ni+Cu) = 1.7%.

[0049] The preparation method of the high-hardness and high-toughness martensitic erosion-resistant cast steel comprises the following steps:

[0050] S1) smelting: pig iron, scrap steel, pure iron metal and iron alloy are added into an electric furnace for smelting, and the molten steel is placed in a steel ladle, and a rare earth alloy is used for inoculation modification treatment to obtain a molten steel to be poured;

[0051] S2) casting: the molten steel to be poured obtained in step S1 is poured through a pouring gate, and a casting is obtained by solidification and cooling;

[0052] S3) normalizing: the casting obtained in step S2 is subjected to sand cleaning treatment, and then is put into a heat treatment furnace, heated to 1020℃, and air-cooled to room temperature after holding for 8h to obtain a normalized casting;

[0053] S4) isothermal quenching: the normalized casting obtained in step S3 is re-heated to 960℃ and held for 6h, and then is put into a 240℃ salt bath furnace for isothermal quenching for 3h, the salt bath medium is composed of 45% NaNO2 and 55% KNO3, and then the molten steel is again discharged and air-cooled to room temperature to obtain an isothermally quenched casting;

[0054] S5) tempering: the quenched castings obtained in step S4 are again put into a heat treatment furnace and heated to 240℃ for 6h, and air-cooled to room temperature to obtain the castings.

[0055] Example 3, a high-hardness and high-toughness martensitic erosion-resistant cast steel

[0056] The chemical composition and mass content of the high-hardness and high-toughness martensitic erosion-resistant cast steel are as follows: C: 0.30%, Si: 1.5%, Mn: 0.6%, Cr: 0.8%, Ni: 0.9%, Mo: 0.3%, Cu: 0.9%, RE: 0.05%, P: 0.022%, S: 0.032%, and the balance being iron and inevitable impurities, Si / C = 5.0, and (Ni+Cu) = 1.8%.

[0057] The preparation method of the high-hardness and high-toughness martensitic erosion-resistant cast steel comprises the following steps:

[0058] S1) smelting: pig iron, scrap steel, pure iron metal and iron alloy are added into an electric furnace for smelting, and the molten steel is placed in a ladle, and a rare earth alloy is used for inoculation modification treatment to obtain a molten steel for pouring;

[0059] S2) casting: the molten steel for pouring obtained in step S1 is poured through a pouring gate, and a casting is obtained through solidification and cooling;

[0060] S3) normalizing: the casting obtained in step S2 is subjected to sand cleaning treatment, and then is sent into a heat treatment furnace, heated to 1000 DEG C, and then air-cooled to room temperature after holding for 8 hours to obtain a normalized casting;

[0061] S4) isothermal quenching: the normalized casting obtained in step S3 is re-heated to 960 DEG C, and then is held for 6 hours, and then is sent into a 230 DEG C salt bath furnace for isothermal quenching for 4 hours, the salt bath medium is composed of 45% NaNO2 and 55% KNO3, and then is air-cooled to room temperature after being discharged again to obtain an isothermally quenched casting;

[0062] S5) tempering: the quenched casting obtained in step S4 is sent into a heat treatment furnace again, heated to 220 DEG C, and held for 8 hours, and then air-cooled to room temperature.

[0063] Embodiment 4, a high-hardness and high-toughness martensitic erosion-resistant cast steel

[0064] The chemical composition and mass content of the high-hardness and high-toughness martensitic erosion-resistant cast steel are as follows: C: 0.35%, Si: 1.8%, Mn: 0.5%, Cr: 0.7%, Ni: 1.0%, Mo: 0.3%, Cu: 1.0%, RE: 0.05%, P: 0.024%, S: 0.033%, and the balance is iron and inevitable impurities, Si / C = 5.1, and (Ni+Cu) = 2.0%.

[0065] The preparation method of the high-hardness and high-toughness martensitic erosion-resistant cast steel comprises the following steps:

[0066] S1) smelting: pig iron, scrap steel, pure iron metal and iron alloy are added into an electric furnace for smelting, and the molten steel is placed in a ladle, and a rare earth alloy is used for inoculation modification treatment to obtain a molten steel for pouring;

[0067] S2) casting: the molten steel for pouring obtained in step S1 is poured through a pouring gate, and a casting is obtained through solidification and cooling;

[0068] S3) normalizing: the casting obtained in step S2 is subjected to sand cleaning treatment, and then is sent into a heat treatment furnace, heated to 1000 DEG C, and then air-cooled to room temperature after holding for 8 hours to obtain a normalized casting;

[0069] S4) isothermal quenching: the normalized castings obtained in step S3 are reheated to 940°C, and held for 6h, and then sent into a 220°C salt bath furnace for isothermal quenching for 5h, the salt bath medium is composed of 45% NaNO2 and 55% KNO3, and then taken out of the furnace and air cooled to room temperature again to obtain the isothermally quenched castings;

[0070] S5) tempering: the quenched castings obtained in step S4 are sent into a heat treatment furnace again, heated to 220°C, held for 8h, and air cooled to room temperature to obtain the final product.

[0071] Example 5, a high hard and tough martensitic erosion-resistant cast steel

[0072] The chemical composition and mass content of the high hard and tough martensitic erosion-resistant cast steel are as follows: C: 0.45%, Si: 2.1%, Mn: 0.5%, Cr: 0.7%, Ni: 1.1%, Mo: 0.4%, Cu: 1.4%, RE: 0.06%, P: 0.024%, S: 0.030%, and the balance being iron and inevitable impurities, Si / C = 4.7, and (Ni+Cu) = 2.5%.

[0073] The preparation method of the high hard and tough martensitic erosion-resistant cast steel comprises the following steps:

[0074] S1) smelting: pig iron, scrap steel, pure iron metal and iron alloy are added into an electric furnace for smelting, and the molten steel is placed in a steel ladle, and a rare earth alloy is used for inoculation modification treatment to obtain a molten steel to be poured;

[0075] S2) casting: the molten steel to be poured obtained in step S1 is poured through a pouring gate, and a casting is obtained by solidification and cooling;

[0076] S3) normalizing: the casting obtained in step S2 is subjected to sand cleaning treatment, and then sent into a heat treatment furnace, heated to 980°C, held for 8h, and then air cooled to room temperature to obtain a normalized casting;

[0077] S4) isothermal quenching: the normalized castings obtained in step S3 are reheated to 940°C, and held for 6h, and then sent into a 220°C salt bath furnace for isothermal quenching for 5h, the salt bath medium is composed of 45% NaNO2 and 55% KNO3, and then taken out of the furnace and air cooled to room temperature again to obtain the isothermally quenched castings;

[0078] S5) tempering: the quenched castings obtained in step S4 are sent into a heat treatment furnace again, heated to 220°C, held for 8h, and air cooled to room temperature to obtain the final product.

[0079] Comparative Example 1, a high hard martensitic cast steel

[0080] The high-hardness martensite cast steel has the following chemical components and mass contents: C: 0.35%, Si: 1.8%, Mn: 0.5%, Cr: 0.7%, Ni: 1.0%, Mo: 0.3%, Cu: 1.0%, RE: 0.05%, P: 0.024%, S: 0.033%, and the balance of iron and inevitable impurities, Si / C = 5.1, and (Ni+Cu) = 2.0%.

[0081] The preparation method of the high-hardness martensite cast steel comprises the following steps:

[0082] S1) smelting: smelting pig iron, scrap steel, pure iron metal and iron alloy in an electric furnace, placing the tapped molten steel in a steel ladle, and performing inoculation modification treatment with a rare earth alloy to obtain a molten steel to be poured;

[0083] S2) casting: pouring the molten steel to be poured obtained in step S1 through a pouring gate, and obtaining a casting by solidification and cooling;

[0084] S3) normalizing: performing sand cleaning treatment on the casting obtained in step S2, then feeding the casting into a heat treatment furnace, heating to 1000 DEG C, holding for 8 hours, and then air cooling to room temperature to obtain a normalized casting;

[0085] S4) quenching: re-heating the normalized casting obtained in step S3 to 940 DEG C, holding for 6 hours, then feeding the casting into a tank containing PAG quenching liquid, and cooling to room temperature to obtain a quenched casting;

[0086] S5) tempering: feeding the quenched casting obtained in step S4 into a heat treatment furnace again, heating to 220 DEG C, holding for 8 hours, and then air cooling to room temperature.

[0087] Comparative Example 2, a high-hardness martensite cast steel

[0088] The high-hardness martensite cast steel has the following chemical components and mass contents: C: 0.35%, Si: 1.8%, Mn: 0.5%, Cr: 0.7%, Ni: 1.5%, Mo: 0.3%, Cu: 1.5%, RE: 0.05%, P: 0.025%, S: 0.032%, and the balance of iron and inevitable impurities, Si / C = 5.1, and (Ni+Cu) = 3.0%.

[0089] The preparation method of the high-hardness martensite cast steel comprises the following steps:

[0090] S1) smelting: smelting pig iron, scrap steel, pure iron metal and iron alloy in an electric furnace, placing the tapped molten steel in a steel ladle, and performing inoculation modification treatment with a rare earth alloy to obtain a molten steel to be poured;

[0091] S2) casting: pouring the molten steel to be poured obtained in step S1 through a pouring gate, and obtaining a casting by solidification and cooling;

[0092] S3) normalizing: the castings obtained in step S2 are sand cleaned, then put into a heat treatment furnace, heated to 1000℃, kept for 8h, and then air cooled to room temperature to obtain normalizing castings;

[0093] S4) isothermal quenching: the normalizing castings obtained in step S3 are re-heated to 940℃, kept for 6h, and then put into a 220℃ salt bath furnace for isothermal quenching for 5h, the salt bath medium is composed of 45% NaNO2 and 55% KNO3, and then air cooled to room temperature again to obtain isothermal quenching castings;

[0094] S5) tempering: the quenched castings obtained in step S4 are put into a heat treatment furnace again, heated to 220℃, kept for 8h, and then air cooled to room temperature to obtain the castings.

[0095] Comparative Example 3, conventional martensitic wear-resistant cast steel

[0096] The chemical composition and mass content of the conventional martensitic wear-resistant cast steel are as follows: C: 0.35%, Si: 0.7%, Mn: 0.6%, Cr: 0.7%, Ni: 1.0%, Mo: 0.3%, RE: 0.05%, P: 0.022%, S: 0.032%, and the balance is iron and inevitable impurities, Si / C = 2.0, (Ni+Cu) = 1.0%.

[0097] The preparation method of the conventional martensitic wear-resistant cast steel comprises the following steps:

[0098] S1) smelting: pig iron, scrap steel, pure iron metal and iron alloy are added into an electric furnace for smelting, and the molten steel is placed in a steel ladle, and a rare earth alloy is used for inoculation modification treatment to obtain a molten steel for pouring;

[0099] S2) casting: the molten steel for pouring obtained in step S1 is poured through a pouring gate, and a casting is obtained by solidification and cooling;

[0100] S3) normalizing: the castings obtained in step S2 are sand cleaned, then put into a heat treatment furnace, heated to 1000℃, kept for 8h, and then air cooled to room temperature to obtain normalizing castings;

[0101] S4) quenching: the normalizing castings obtained in step S3 are re-heated to 940℃, kept for 6h, and then put into a tank containing PAG quenching liquid and cooled to room temperature to obtain quenched castings;

[0102] S5) tempering: the quenched castings obtained in step S4 are put into a heat treatment furnace again, heated to 220℃, kept for 8h, and then air cooled to room temperature to obtain the castings.

[0103] Comparative Example 4, conventional wear-resistant high manganese steel

[0104] The chemical composition and mass content of the conventional wear-resistant high manganese steel are as follows: C: 1.0%, Si: 0.8%, Mn: 13.0%, Cr: 1.0%, RE: 0.06%, P: 0.025%, S: 0.035%, and the balance being iron and inevitable impurities.

[0105] The preparation method of the conventional wear-resistant high manganese steel comprises the following steps:

[0106] S1) smelting: pig iron, scrap steel, pure iron metal and iron alloy are added into an electric furnace for smelting, the composition of the molten steel is adjusted to be within the error range of the designed composition, and the temperature of the molten steel is adjusted to 1480 DEG C, and then the molten steel is discharged;

[0107] S2) inoculation treatment: an inoculant made of rare earth alloy is placed in the ladle, and the molten steel obtained in step S1 is subjected to inoculation treatment by using the ladle pouring method, so as to obtain the molten steel to be poured;

[0108] S3) casting: the molten steel obtained in step S2 is cooled to 1430 DEG C, and then poured through a pouring gate, and then solidified and cooled to obtain a casting;

[0109] S4) water toughening treatment: the casting obtained in step S3 is subjected to sand cleaning treatment, and then sent into a heat treatment furnace, heated to 1070 DEG C, and then held for 6 hours, and then water cooled to room temperature.

[0110] Performance test of materials of examples and comparative examples

[0111] Experimental method: the cast steels prepared in examples 1-5 and comparative examples 1-4 are subjected to performance test. The impact test at room temperature is V-shaped notch impact test. Before the Vickers hardness test, the test surface of the sample is ground and polished. The impact abrasive wear test and the impact corrosion abrasive wear test are both carried out on an MLD-10 type dynamic load abrasive wear testing machine. The impact energy is 2.0 J, the impact frequency is 100 times per minute, the lower sample is 45# steel, the rotating speed is 100 revolutions per minute, the abrasive for the impact wear test is 5 Kg of quartz sand, and the particle size of the quartz sand is between 60-80 meshes. The abrasive for the impact corrosion wear test is 5 Kg of quartz sand + 1000 mL of corrosion solution. The corrosion solution simulates the service environment of the semi-autogenous mill liner for copper mine grinding. The pH value is 6, and it is mixed by 12.5 mg / L CuSO4, 11.6 mg / L NaCl and 4.14 g / L Na2SO4. Each group of samples is pre-ground for 30 minutes before the test. During the impact wear process, the weight loss is weighed once every 30 minutes, a total of five periods, for a total of 2.5 hours.

[0112] Table 1: performance test results

[0113]

[0114] 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.

[0115] As shown in Table 1, the high-hardness, high-toughness martensitic wear-resistant cast steel prepared by this invention has a hardness of 431–554 HV, while the V-notch impact absorption energy reaches 16.4–30.1 J, exhibiting a good hardness-toughness ratio. Figure 1 and Figure 2 As shown, the retained austenite content (statistically) in Example 4 was 9.3%, significantly higher than the 3.5% in Comparative Example 3. Compared to conventional martensitic wear-resistant cast steel with the same carbon content as Comparative Example 3, the hardness of Example 4 decreased by approximately 2.6% (14HV), but the V-notch impact absorption energy increased by 98.5% (12.8J). Therefore, the impact abrasive wear resistance was improved by 27.2%. Meanwhile, as... Figure 3 As shown, the corrosion current density in the simulated solution of Example 4 can be obtained from the Tafel polarization curve by extrapolation as 6.02 × 10⁻⁶. -6 A / cm 2 This is lower than the 3.55 × 10⁻⁶ of Comparative Example 3. -5 A / cm 2 Due to its superior corrosion resistance, the impact corrosion abrasive wear resistance of Example 4 was improved by 47.8% compared to Comparative Example 3 and by 81.1% compared to Comparative Example 4.

[0116] The present application has the following obvious differences from the existing wear-resistant cast steel: (1) After austenitizing treatment of the steel, quenching is performed to a temperature between the martensite transformation start temperature (Ms) and the martensite transformation end temperature (Mf) and then kept for a period of time. During the isothermal process, the supersaturated carbon atoms in the martensite diffuse into the residual austenite, obtaining "carbon-rich" austenite. The martensite matrix can ensure that the material has high hardness. The TRIP effect of the metastable residual austenite makes the material have excellent impact toughness. The combination of high hardness and excellent impact toughness makes the martensitic wear-resistant steel have good impact-resistant abrasive wear performance. (2) The steel has high Si, Ni and Cu contents, wherein Si / C≥4.2 and 1.4%≤(Ni+Cu)≤2.8%. The precipitation of carbides not only significantly reduces the impact toughness of the material, but also induces galvanic corrosion, reducing the corrosion resistance of the material. The Si element helps to inhibit the precipitation of carbides during the isothermal process, but too high Si will significantly reduce the plasticity and toughness of the steel. The metastable residual austenite can improve the impact toughness of the material, but it will also reduce the corrosion resistance of the material due to galvanic corrosion. Ni and Cu can effectively reduce the corrosion current density of the steel and thus improve the corrosion resistance of the material. Too little Ni and Cu cannot guarantee the improvement of the corrosion resistance of the material. Ni and Cu are austenite stabilizing elements, and too much will increase the content of residual austenite, causing the residual austenite to change from a film to a block, significantly reducing the toughness of the material, leading to a significant decrease in wear resistance, and thus reducing the wear and corrosion resistance of the material. In addition, the diffusion of carbon atoms and the precipitation of carbides are significantly affected by the isothermal temperature and time. For example, if the temperature is too low, the carbon atoms are difficult to diffuse. The increase in the content of carbides in the structure worsens the impact toughness and corrosion resistance.

[0117] The present application optimizes the alloy composition content and reasonably designs the heat treatment process, so that the medium alloy steel has high hardness, excellent toughness and good corrosion resistance, and the production cost is low, overcoming the contradiction between the wear resistance, corrosion resistance and production cost of the existing metal materials under the condition of medium and high stress impact corrosion abrasive wear. The martensitic steel with high hardness, excellent toughness and good corrosion resistance shows better wear and corrosion resistance than traditional martensitic steel and high manganese steel in medium and high impact corrosion abrasive wear tests, and is especially suitable for manufacturing parts under the condition of medium and high stress impact corrosion abrasive wear, such as medium and large ball mill liner, impact crusher guard plate and crusher hammer.

[0118] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above embodiments, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods and shall be included in the protection scope of the present application.

Claims

1. A high-hardness, high-toughness, wear-resistant and corrosion-resistant cast steel, characterized in that, The chemical composition of the high-hardness, toughness, and wear-resistant cast steel, by mass percentage, is as follows: C: 0.20-0.45%, Si: 1.0-2.3%, Mn: 0.4-0.9%, Cr: 0.6-1.4%, Ni: 0.8-1.8%, Mo: 0.2-0.6%, Cu: 0.5-1.5%, RE: 0.03-0.08%, P≤0.032%, S≤0.040%, with the balance being Fe and unavoidable impurities; and Si / C≥4.7, 1.5%≤(Ni+Cu)≤2.5%.

2. The high-hardness, high-toughness, wear-resistant and corrosion-resistant cast steel as described in claim 1, characterized in that, The chemical composition of the high-hardness, high-toughness, wear-resistant and corrosion-resistant cast steel, by mass percentage, is as follows: C: 0.25-0.35%, Si: 1.4-1.8%, Mn: 0.5-0.8%, Ni: 0.9-1.0%, Cr: 0.7-0.8%, Mo: 0.3-0.4%, Cu: 0.7-1.0%, RE: 0.05%, P: 0.022-0.024%, S: 0.032-0.035%, with the balance being iron and unavoidable impurities.

3. The high-hardness, high-toughness, wear-resistant and corrosion-resistant cast steel as described in claim 2, characterized in that, The chemical composition of the high-hardness, toughness, wear-resistant and corrosion-resistant cast steel, by mass percentage, is: C: 0.35%, Si: 1.8%, Mn: 0.5%, Ni: 1.0%, Cr: 0.7%, Mo: 0.3%, Cu: 1.0%, RE: 0.05%, P: 0.022%, S: 0.032%, with the balance being iron and unavoidable impurities.

4. A method for preparing the high-hardness, high-toughness, and wear-resistant cast steel according to claim 1, 2, or 3, characterized in that, Includes the following steps: S1) Smelting: Smelting pig iron, scrap steel, pure iron metal and ferroalloys, and then using rare earth alloys to perform inoculation and modification treatment on the molten steel to obtain the molten steel to be cast. 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. S3) Normalizing: The casting obtained in step S2 is cleaned of sand, then heated, held at the temperature, and then air-cooled to room temperature to obtain the normalized casting. S4) Isothermal quenching: The normalized casting obtained in step S3 is reheated, held at the temperature, and then isothermal quenched and held at the temperature. Then it is air-cooled to room temperature again to obtain the isothermal quenched casting. S5) Tempering: The isothermal quenched casting obtained in step S4 is tempered and held at the same temperature, and then air-cooled to room temperature to obtain high hardness, toughness and wear resistance cast steel.

5. The method for preparing high-hardness, toughness, and wear-resistant cast steel as described in claim 4, characterized in that, The heating in step S3 is to heat to 950-1050℃ and hold for 4-8 hours.

6. The method for preparing high-hardness, toughness, and wear-resistant cast steel as described in claim 4, characterized in that, The reheating temperature in step S4 is 940-980℃, and the holding time is 4-8 h.

7. The method for preparing high-hardness, toughness, and wear-resistant cast steel as described in claim 4, characterized in that, The isothermal quenching temperature in step S4 is 200-260℃, and the holding time is 2-6 h.

8. The method for preparing high-hardness, toughness, and wear-resistant cast steel as described in claim 4, characterized in that, The isothermal quenching described in step S4 is salt bath isothermal quenching, and the salt bath medium consists of NaNO2 and KNO3.

9. The method for preparing high-hardness, toughness, and wear-resistant cast steel as described in claim 4, characterized in that, The tempering process in step S5 is carried out at a temperature of 180-240℃ for 4-10 hours.

10. The use of the high-hardness, high-toughness, wear-resistant and corrosion-resistant cast steel as described in any one of claims 1 to 3 in the manufacture of wear-resistant or wear-resistant parts.

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