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

Abstract

The invention belongs to the technical field of wear-resistant cast steel, and discloses high-hardness and high-toughness wear-resistant cast steel as well as a preparation method and application thereof. The high-hardness and high-toughness wear-corrosion-resistant cast steel is prepared from the following chemical components in percentage by mass: 0.20 to 0.45 percent of C, 1.0 to 2.3 percent of Si, 0.4 to 0.9 percent of Mn, 0.6 to 1.4 percent of Cr, 0.8 to 1.8 percent of Ni, 0.2 to 0.6 percent of Mo, 0.5 to 1.5 percent of Cu, 0.03 to 0.08 percent of RE, less than or equal to 0.032 percent of P, less than or equal to 0.040 percent of S and the balance of Fe and inevitable impurities. Si / C > = 4.2, and 1.4% < = (Ni + Cu) < = 2.8%. By optimizing alloy components and a heat treatment process, the prepared cast steel has high hardness, excellent toughness and corrosion resistance, and the high-hardness and high-toughness wear-resistant steel is simple in preparation process, low in cost and good in application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of wear-resistant cast steel, and particularly relates to a high-hardness, tough and wear-resistant corrosion-resistant cast steel and a preparation method and application thereof. Background Art

[0002] Impact abrasive wear is an extremely harsh wear condition. Mechanical components, such as the cutting teeth of roadheaders, the hammers and tooth plates of crushers, and the liners of ball mills, will be simultaneously subjected to impact loads and abrasive wear during operation. The direct economic loss caused by impact abrasive wear in the mining machinery industry alone reaches tens of billions of yuan every year. Relevant research shows that the failure of components under impact wear conditions mainly stems from low-toughness fracture and low-strength deformation and abrasive wear failure. Therefore, steel materials with excellent strength and toughness are widely used as components resistant to impact abrasive wear. 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 based on this. However, the service conditions of many wear-resistant components are corrosive, and their service safety and life are affected by the combined action of corrosion and impact abrasive wear behavior. At the same time, a large number of studies have pointed out that there are significant differences between the corrosion-resistant wear performance and the wear-resistant performance of materials. Therefore, the research on developing steel materials resistant to impact corrosion abrasive wear has gradually attracted the attention of the wear-resistant steel field.

[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 and corrosion-resistant steel plate for slurry dredging and a production method thereof. Chinese Patent CN110387507A discloses an HB500-grade wear-resistant steel for corrosive slurry transportation containers and a production method thereof. Chinese Patent CN117684100A discloses a heat-treatment-free martensitic wear-resistant and corrosion-resistant steel and a manufacturing method thereof. Chinese Patent CN113025888B discloses a wear-resistant and corrosion-resistant high-strength steel and a preparation method thereof. The above 5 kinds of steels have both excellent wear resistance and corrosion resistance. However, their production processes all include processes such as vacuum melting, refining, forging, or multi-pass rolling. The process route 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 bainite-martensite-austenite duplex wear-resistant and corrosion-resistant steel. Although there is a preparation process for castings involved, due to the content of up to 3.5% Mn (mass fraction) in the composition, and Mn elements are easy to oxidize, the previous smelting process also involves vacuum melting and refining, resulting in a significant increase in production costs.

[0005] In the prior art, there are contradictions among the wear resistance, corrosion resistance and production cost of steel materials. Therefore, providing a steel material with simple process, low cost and good wear resistance and corrosion resistance at the same time has broad application prospects. Summary of the Invention

[0006] In order to overcome the disadvantages and deficiencies of the prior art, the primary object of the present invention is to provide a high-hardness, tough, wear-resistant and corrosion-resistant cast steel.

[0007] Another object of the present invention is to provide a preparation method of the high-hardness, tough, wear-resistant and corrosion-resistant cast steel. Based on the traditional low-alloy wear-resistant steel, appropriate amounts of Si, Cu, and Ni are added to this wear-resistant and corrosion-resistant cast steel. After normalizing, isothermal quenching, and tempering heat treatments, a duplex structure mainly composed of martensite and supplemented by a small amount of metastable retained austenite is obtained. This duplex structure has good corrosion resistance while having both high hardness and good toughness. In addition, the preparation process of this high-hardness, tough, wear-resistant and corrosion-resistant cast steel is simple and the cost is low.

[0008] Another object of the present invention is to provide the application of the above-mentioned high-hardness, tough, wear-resistant and corrosion-resistant cast steel, which is particularly suitable for manufacturing components used in medium-high stress impact corrosion and abrasive wear working conditions, such as medium and large-sized ball mill liners for mines, impact crusher liners, crusher hammers, etc.

[0009] The present invention adopts the following technical solutions:

[0010] A high-hardness, tough, wear-resistant and corrosion-resistant cast steel. By mass percentage, the chemical composition of the high-hardness, tough, wear-resistant and corrosion-resistant cast steel 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%, and the balance is Fe and inevitable impurities. And, Si / C ≥ 4.2, 1.4% ≤ (Ni + Cu) ≤ 2.8%.

[0011] Preferably, by mass percentage, the chemical composition of the high-hardness, tough, wear-resistant and corrosion-resistant cast steel 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%, and the balance is iron and inevitable impurities, Si / C ≥ 4.7, 1.5% ≤ (Ni + Cu) ≤ 2.5%.

[0012] Preferably, by mass percentage, the chemical composition of the high-hardness, tough and corrosion-resistant cast steel is as follows: 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 is iron and unavoidable impurities.

[0013] Preferably, the hardness of the high-hardness, tough and corrosion-resistant cast steel is 431 - 554 HV, the impact energy absorbed by V-notch is 16.4 - 30.1 J, and the corrosion-resistant wear performance is increased by up to 47.8% and 81.1% compared with traditional martensitic steel and high manganese steel respectively.

[0014] Preferably, the high-hardness, tough and corrosion-resistant cast steel is mainly composed of martensite, supplemented with a small amount of metastable retained austenite.

[0015] A preparation method of high-hardness, tough and corrosion-resistant cast steel includes the following steps:

[0016] S1) Smelting: Smelt pig iron, scrap steel, pure iron metal and ferroalloy, and perform inoculation modification treatment on the smelted steel liquid with rare earth alloy to obtain the steel liquid to be poured.

[0017] S2) Casting and forming: Pour the steel liquid to be poured obtained in step S1 through the gate, and solidify and cool to obtain a casting.

[0018] S3) Normalizing: Sandblast the casting obtained in step S2, then heat it, keep it warm, and then air-cool it to room temperature to obtain the normalized casting.

[0019] S4) Austempering: Reheat the normalized casting obtained in step S3, keep it warm, then perform austempering and keep it warm, and then air-cool it to room temperature again to obtain the austempered casting.

[0020] S5) Tempering: Temper the austempered casting obtained in step S4 again and keep it warm, and then air-cool it to room temperature to obtain the high-hardness, tough and corrosion-resistant cast steel.

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

[0022] Preferably, the temperature of the reheating in step S4 is 940 - 980 °C, and the holding time is 4 - 8 h.

[0023] Preferably, the temperature of the austempering in step S4 is 200 - 260 °C, and the holding time is 2 - 6 h.

[0024] Preferably, the austempering in step S4 is salt bath austempering, and the salt bath medium consists of NaNO 2 and KNO 3Composition, more preferably 45% NaNO 2 and 55% KNO 3 Composition.

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

[0026] Preferably, the pig iron, scrap steel, pure iron metal and ferroalloy in step S1 are well-known commercial ordinary raw materials and can be obtained by purchasing from the market.

[0027] Application of the above high-hardness, tough and wear-resistant corrosion-resistant cast steel in manufacturing wear-resistant parts or wear-resistant and corrosion-resistant parts.

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

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

[0030] The high-hardness, tough and wear-resistant martensitic corrosion-resistant cast steel prepared by the present invention is based on traditional low-alloy wear-resistant steel. By adding appropriate amounts of Si, Cu, and Ni elements and combining appropriate normalizing, austempering, and tempering heat treatment processes, a duplex structure mainly composed of martensite and supplemented with a small amount of metastable retained austenite is obtained. Martensite has high strength, and the transformation-induced plasticity (TRIP effect) of metastable retained austenite can make the material exhibit good toughness. In addition, Si can inhibit the precipitation of carbides, reduce the heterogeneous phases in the structure, slow down 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, tough and wear-resistant martensitic corrosion-resistant cast steel prepared by the present invention has a hardness of 431 - 554 HV and a V-notch impact energy absorption of 16.4 - 30.1 J, with good hardness-toughness matching. The corrosion and wear resistance are 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, tough and wear-resistant martensitic corrosion-resistant cast steel provided by the present invention is simple and easy to control. Only by optimizing the alloy composition and heat treatment process on the basis of traditional low-alloy wear-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 it has a wide application prospect.

[0033] The high-hardness, tough and wear-resistant martensitic corrosion-resistant cast steel prepared by the present invention is particularly suitable for manufacturing parts under medium-high stress impact corrosion and abrasive wear conditions: such as medium and large-sized ball mill liners, impact crusher liners, crusher hammers, etc. used in mines. Description of the Drawings

[0034] Figure 1 This is the SEM micrograph of the structure of the high-hardness and tough martensitic wear-resistant and corrosion-resistant cast steel produced in Example 4 of the present invention.

[0035] Figure 2 This is the SEM micrograph of the structure of the traditional martensitic wear-resistant cast steel produced in Comparative Example 3 of the present invention.

[0036] Figure 3 This is the Tafel polarization curve of the cast steel structures produced in Example 4 and Comparative Example 3 of the present invention. Detailed Description of the Invention

[0037] The following is a further explanation of the content of the present invention through specific embodiments in the form of examples. However, the scope of the above subject matter of the present invention is not limited to the following examples. For process parameters not specifically noted, conventional techniques can be referred to.

[0038] The raw materials such as pig iron, scrap steel, pure iron metal, and ferroalloys used in the examples are all well-known commercial ordinary raw materials and can be obtained by purchasing from the market.

[0039] Example 1. A High-Hardness and Tough Martensitic Wear-Resistant and Corrosion-Resistant Cast Steel

[0040] The chemical composition and its mass content of the high-hardness and tough martensitic wear-resistant and corrosion-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%, and the balance is iron and inevitable impurities. Si / C = 5, (Ni + Cu) = 1.5%.

[0041] The preparation method of the high-hardness and tough martensitic wear-resistant and corrosion-resistant cast steel includes the following steps:

[0042] S1) Smelting: Add pig iron, scrap steel, pure iron metal, and ferroalloys to an electric furnace for smelting. Place the molten steel tapped from the furnace in a ladle and perform inoculation modification treatment with rare earth alloy to obtain the molten steel to be poured.

[0043] S2) Casting and forming: Pour the molten steel to be poured obtained in step S1 through a gate, and solidify and cool to obtain a casting.

[0044] S3) Normalizing: Carry out sand cleaning treatment on the casting obtained in step S2, then send it into a heat treatment furnace, heat it to 1050 °C, hold for 8 h, and then air-cool to room temperature to obtain the normalized casting.

[0045] S4) Austempering: Reheat the normalized casting obtained in step S3 to 980 °C, hold for 6 h, then send it into a salt bath furnace at 260 °C for austempering and hold for 2 h. The salt bath medium consists of 45% NaNO 2 and 55% KNO 3 and then take it out of the furnace again and air-cool it to room temperature to obtain the austempered casting;

[0046] S5) Tempering: Send the quenched casting obtained in step S4 into the heat treatment furnace again, heat it to 240 °C, hold for 6 h, and air-cool it to room temperature to obtain the product.

[0047] Example 2. A high-hardness and tough martensitic wear-resistant cast steel

[0048] The chemical composition and mass content of the high-hardness and tough martensitic wear-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 is iron and inevitable impurities. Si / C = 5.6, (Ni + Cu) = 1.7%.

[0049] The preparation method of the high-hardness and tough martensitic wear-resistant cast steel includes the following steps:

[0050] S1) Smelting: Add pig iron, scrap steel, pure iron metal and ferroalloy to an electric furnace for smelting. Place the molten steel obtained from the furnace in a ladle and perform inoculation and modification treatment with rare earth alloy to obtain the molten steel to be poured;

[0051] S2) Casting and forming: Pour the molten steel to be poured obtained in step S1 through the gate, and solidify and cool to obtain a casting;

[0052] S3) Normalizing: Carry out sand cleaning treatment on the casting obtained in step S2, then send it into the heat treatment furnace, heat it to 1020 °C, hold for 8 h, and then air-cool it to room temperature to obtain the normalized casting;

[0053] S4) Austempering: Reheat the normalized casting obtained in step S3 to 960 °C, hold for 6 h, then send it into a salt bath furnace at 240 °C for austempering and hold for 3 h. The salt bath medium consists of 45% NaNO 2 and 55% KNO 3 and then take it out of the furnace again and air-cool it to room temperature to obtain the austempered casting;

[0054] S5) Tempering: Send the quenched casting obtained in step S4 into the heat treatment furnace again, heat it to 240 °C, hold for 6 h, and air-cool it to room temperature to obtain the product.

[0055] Example 3. A high-hardness and tough martensitic wear-resistant cast steel

[0056] The chemical composition and its mass content of the high-hardness and tough martensitic wear-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 is iron and inevitable impurities. Si / C = 5.0, (Ni + Cu) = 1.8%.

[0057] The preparation method of the high-hardness and tough martensitic wear-resistant cast steel includes the following steps:

[0058] S1) Smelting: Add pig iron, scrap steel, pure iron metal and ferroalloy into an electric furnace for smelting. Place the molten steel after tapping into a ladle, and conduct inoculation and modification treatment with rare earth alloy to obtain the molten steel to be poured;

[0059] S2) Casting and forming: Pour the molten steel to be poured obtained in step S1 through a gate, and solidify and cool to obtain a casting;

[0060] S3) Normalizing: Carry out sand cleaning treatment on the casting obtained in step S2, then send it into a heat treatment furnace, heat it to 1000 °C, hold for 8 h, and then air-cool to room temperature to obtain the normalized casting;

[0061] S4) Austempering: Reheat the normalized casting obtained in step S3 to 960 °C, hold for 6 h, then send it into a salt bath furnace at 230 °C for austempering and holding for 4 h. The salt bath medium consists of 45% NaNO 2 and 55% KNO 3 Then take it out of the furnace again and air-cool to room temperature to obtain the austempered casting;

[0062] S5) Tempering: Send the quenched casting obtained in step S4 into the heat treatment furnace again, heat it to 220 °C, hold for 8 h, and air-cool to room temperature to obtain the product.

[0063] Example 4. A high-hardness and tough martensitic wear-resistant cast steel

[0064] The chemical composition and its mass content of the high-hardness and tough martensitic wear-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, (Ni + Cu) = 2.0%.

[0065] The preparation method of the high-hardness and tough martensitic wear-resistant cast steel includes the following steps:

[0066] S1) Smelting: Add pig iron, scrap steel, pure iron metal and ferroalloy into an electric furnace for smelting. Place the molten steel tapped from the furnace into a ladle, and conduct inoculation and modification treatment with rare earth alloy to obtain the molten steel to be poured.

[0067] S2) Casting and forming: Pour the molten steel to be poured obtained in step S1 through a gate, and solidify and cool to obtain a casting.

[0068] S3) Normalizing: Conduct sand cleaning treatment on the casting obtained in step S2, then send it into a heat treatment furnace, heat it to 1000 °C, keep it warm for 8 h, and then air cool it to room temperature to obtain the normalized casting.

[0069] S4) Austempering: Reheat the normalized casting obtained in step S3 to 940 °C, keep it warm for 6 h, then send it into a salt bath furnace at 220 °C for austempering and keep it warm for 5 h. The salt bath medium consists of 45% NaNO 2 and 55% KNO 3 , and then take it out of the furnace again and air cool it to room temperature to obtain the austempered casting.

[0070] S5) Tempering: Send the quenched casting obtained in step S4 into the heat treatment furnace again, heat it to 220 °C and keep it warm for 8 h, and then air cool it to room temperature to obtain the product.

[0071] Example 5. A high-hardness and tough martensitic wear-resistant cast steel

[0072] The chemical composition and its mass content of the high-hardness and tough martensitic wear-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 is iron and inevitable impurities. Si / C = 4.7, (Ni + Cu) = 2.5%.

[0073] The preparation method of the high-hardness and tough martensitic wear-resistant cast steel includes the following steps:

[0074] S1) Smelting: Add pig iron, scrap steel, pure iron metal and ferroalloy into an electric furnace for smelting. Place the molten steel tapped from the furnace into a ladle, and conduct inoculation and modification treatment with rare earth alloy to obtain the molten steel to be poured.

[0075] S2) Casting and forming: Pour the molten steel to be poured obtained in step S1 through a gate, and solidify and cool to obtain a casting.

[0076] S3) Normalizing: Conduct sand cleaning treatment on the casting obtained in step S2, then send it into a heat treatment furnace, heat it to 980 °C, keep it warm for 8 h, and then air cool it to room temperature to obtain the normalized casting.

[0077] S4) Austempering: Reheat the normalized casting obtained in step S3 to 940 °C, hold for 6 h, then send it into a salt bath furnace at 200 °C for austempering and hold for 6 h. The salt bath medium consists of 45% NaNO 2 and 55% KNO 3 After that, take it out of the furnace again and air-cool it to room temperature to obtain the austempered casting;

[0078] S5) Tempering: Send the quenched casting obtained in step S4 into a heat treatment furnace again, heat it to 200 °C and hold for 8 h, then air-cool it to room temperature to obtain the product.

[0079] Comparative Example 1. A high-hardness martensitic cast steel

[0080] The chemical composition and mass content of the high-hardness martensitic 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, (Ni + Cu) = 2.0%.

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

[0082] S1) Smelting: Add pig iron, scrap steel, pure iron metal and ferroalloy to an electric furnace for smelting. Place the molten steel poured out of the furnace in a ladle, and perform inoculation and modification treatment with rare earth alloy to obtain the molten steel to be poured;

[0083] S2) Casting and forming: Pour the molten steel to be poured obtained in step S1 through the gate, and solidify and cool to obtain a casting;

[0084] S3) Normalizing: Sandblast the casting obtained in step S2, then send it into a heat treatment furnace, heat it to 1000 °C, hold for 8 h and then air-cool it to room temperature to obtain the normalized casting;

[0085] S4) Quenching: Reheat the normalized casting obtained in step S3 to 940 °C, hold for 6 h, then send it into a tank filled with PAG quenching liquid and cool it to room temperature to obtain the quenched casting;

[0086] S5) Tempering: Send the quenched casting obtained in step S4 into a heat treatment furnace again, heat it to 220 °C and hold for 8 h, then air-cool it to room temperature to obtain the product.

[0087] Comparative Example 2. A high-hardness martensitic cast steel

[0088] The chemical composition and its mass content of the high-hardness martensitic cast steel are as follows: 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 is iron and inevitable impurities. Si / C = 5.1, (Ni + Cu) = 3.0%.

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

[0090] S1) Smelting: Add pig iron, scrap steel, pure iron metal and ferroalloys to an electric furnace for smelting. Place the molten steel discharged from the furnace in a ladle and perform inoculation modification treatment with rare earth alloy to obtain the molten steel to be poured.

[0091] S2) Casting and forming: Pour the molten steel to be poured obtained in step S1 through a sprue, and solidify and cool to obtain a casting.

[0092] S3) Normalizing: Sandblast the casting obtained in step S2, then send it into a heat treatment furnace, heat it to 1000 °C, hold for 8 h, and then air-cool to room temperature to obtain the normalized casting.

[0093] S4) Austempering: Reheat the normalized casting obtained in step S3 to 940 °C, hold for 6 h, then send it into a salt bath furnace at 220 °C for austempering and hold for 5 h. The salt bath medium consists of 45% NaNO 2 and 55% KNO 3 Then take it out of the furnace again and air-cool to room temperature to obtain the austempered casting.

[0094] S5) Tempering: Send the quenched casting obtained in step S4 into the heat treatment furnace again, heat it to 220 °C, hold for 8 h, and air-cool to room temperature to obtain the product.

[0095] Comparative Example 3: Conventional martensitic wear-resistant cast steel

[0096] The chemical composition and its 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 includes the following steps:

[0098] S1) Smelting: Add pig iron, scrap steel, pure iron metal and ferroalloys to an electric furnace for smelting. Place the molten steel discharged from the furnace in a ladle and perform inoculation modification treatment with rare earth alloy to obtain the molten steel to be poured.

[0099] S2) Casting and forming: Pouring the molten steel to be poured obtained in step S1 through the gate, and solidifying and cooling to obtain a casting;

[0100] S3) Normalizing: Sand cleaning the casting obtained in step S2, then sending it into a heat treatment furnace, heating to 1000 °C, holding for 8 h, and then air cooling to room temperature to obtain the normalized casting;

[0101] S4) Quenching: Reheating the normalized casting obtained in step S3 to 940 °C, holding for 6 h, and then sending it into a tank filled with PAG quenching liquid to cool to room temperature to obtain the quenched casting;

[0102] S5) Tempering: Sending the quenched casting obtained in step S4 into the heat treatment furnace again, heating to 220 °C, holding for 8 h, and air cooling to room temperature to obtain the product.

[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 is iron and inevitable impurities.

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

[0106] S1) Smelting: Adding pig iron, scrap steel, pure iron metal and ferroalloy into an electric furnace for smelting, adjusting the composition of the molten steel within the error range of the designed composition, and the temperature of the molten steel to 1480 °C, then tapping;

[0107] S2) Inoculation treatment: Placing an inoculant made of rare earth alloy inside the ladle, and performing inoculation treatment on the molten steel obtained in step S1 by in-ladle impingement method to obtain the molten steel to be poured;

[0108] S3) Casting and forming: Cooling the molten steel obtained in step S2 to 1430 °C, pouring through the gate, and solidifying and cooling to obtain a casting;

[0109] S4) Solution treatment: Sand cleaning the casting obtained in step S3, then sending it into a heat treatment furnace, heating to 1070 °C, holding for 6 h, and then water cooling to room temperature to obtain the product.

[0110] Material property tests of examples and comparative examples

[0111] Experimental methods: The performance of the cast steels prepared in Examples 1-5 and Comparative Examples 1-4 was tested. The V-notch impact test was used for the room temperature impact test. Before the Vickers hardness test, the test surface of the specimen was ground and polished. Both the impact abrasive wear test and the impact corrosive abrasive wear test were carried out on an MLD-10 type dynamic load abrasive wear testing machine. The impact energy was 2.0 J, the impact frequency was 100 times per minute, the lower specimen was 45# steel, the rotation speed was 100 revolutions per minute, the abrasive for the impact wear test was 5 Kg of quartz sand, and the particle size of the quartz sand was between 60 and 80 mesh. The abrasive for the impact corrosive wear test was 5 Kg of quartz sand + 1000 mL of corrosive solution. The corrosive solution simulated the service environment of the semi-autogenous mill liners used for copper ore grinding. Its pH value was 6, which was composed of 12.5 mg / L CuSO 4 4, 11.6 mg / L NaCl, 4.14 g / L Na 2 2 4 4 mixed. Each group of specimens was pre-ground for 30 min before the test. During the impact wear process, the weight loss was weighed once every 30 min as a wear cycle, and a total of five cycles were carried out, for a total of 2.5 h.

[0112] Table 1 Performance test results

[0113]

[0114] The hardness in Table 1 is the average value of 10 values, and the V-notch impact absorption energy and wear weight loss are the average values of 3 values.

[0115] As can be seen from Table 1, the hardness of the high-hardness and tough martensitic wear-resistant and corrosion-resistant cast steel prepared by the present invention can reach 431-554 HV. At the same time, the V-notch impact absorption energy reaches 16.4-30.1 J, having a good hardness and toughness ratio. As Figure 1 and Figure 2 shown, the content of retained austenite in Example 4 (statistically) is 9.3%, much higher than 3.5% in Comparative Example 3. Compared with the conventional martensitic wear-resistant cast steel with the same carbon content as Comparative Example 3, the hardness of Example 4 decreased by about 2.6% (14 HV), but the V-notch impact absorption energy increased by 98.5% (12.8 J). Therefore, the anti-impact abrasive wear performance increased by 27.2%. At the same time, as Figure 3 shown, the corrosion current density of Example 4 in the simulated solution can be obtained from the Tafel polarization curve by extrapolation as 6.02×10 -6 -8 2 A / cm -5 2 2 2, lower than 3.55×10 -5 -7 2 A / cm -5 2 2 2 of Comparative Example 3. Due to its good corrosion resistance, the anti-impact corrosive abrasive wear performance of Example 4 increased by 47.8% compared with Comparative Example 3 and 81.1% compared with Comparative Example 4.

[0116] The obvious differences between the present invention and the existing wear-resistant cast steel are as follows: (1) After the steel is austenitized, it is quenched to a temperature between the martensite transformation start temperature (Ms) and the martensite transformation finish temperature (Mf) and held for a period of time. During the isothermal process, the supersaturated carbon atoms in the martensite diffuse into the retained austenite, obtaining "carbon-rich" austenite. The martensite matrix can ensure that the material has a high hardness. The TRIP effect of the metastable retained austenite endows the material with better impact toughness. The combination of high hardness and excellent impact toughness makes the martensitic wear-resistant steel exhibit good impact abrasive wear resistance. (2) It has relatively high Si, Ni, and Cu contents, where Si / C ≥ 4.2 and 1.4% ≤ (Ni + Cu) ≤ 2.8%. The precipitation of carbides will not only significantly reduce the impact toughness of the material but also induce galvanic corrosion and reduce the corrosion resistance of the material. The Si element helps to inhibit the precipitation of carbides during the isothermal process, but too much Si will significantly reduce the plasticity and toughness of the steel. Although the metastable retained austenite can improve the impact toughness of the material, 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, thereby improving the corrosion resistance of the material. Too little Ni and Cu are difficult to ensure the improvement of the corrosion resistance of the material. Ni and Cu are austenite-stabilizing elements. Excessive amounts will increase the content of retained austenite, causing the retained austenite to change from a film-like shape to a blocky shape, significantly reducing the toughness of the material, resulting in a significant decline in wear resistance, and further reducing the wear and corrosion resistance of the material. In addition, behaviors such as the diffusion of carbon atoms and the precipitation of carbides are significantly affected by the isothermal temperature and isothermal time. For example, when the temperature is too low, it is difficult for carbon atoms to diffuse. The content of carbides in the structure increases, deteriorating the impact toughness and corrosion resistance.

[0117] Through optimizing the alloy composition content and reasonably designing the heat treatment process, the medium alloy steel of the present invention not only has high hardness and excellent toughness but also exhibits good corrosion resistance, and has a low production cost, overcoming the contradiction between the wear resistance, corrosion resistance matching and production cost of existing metal materials under medium and high stress impact corrosion abrasive wear conditions. 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 the medium and high impact corrosion abrasive wear test, and is especially suitable for manufacturing components under medium and high stress impact corrosion abrasive wear conditions, such as medium and large-sized ball mill liners for mines, impact crusher liners, crusher hammers, etc.

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

Claims

1. A high hardness, toughness and wear-resistant cast steel, characterized in that: Measured by mass percentage, the chemical composition of the high hardness, toughness and wear-resistant cast steel is: 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 remainder is Fe and unavoidable impurities; and Si / C≥4.2, 1.4%≤(Ni+Cu)≤2.8%.

2. The high hardness, toughness and wear-resistant cast steel according to claim 1, characterized in that: Measured by mass percentage, the chemical composition of the high hardness, toughness and wear-resistant cast steel is: 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 iron and unavoidable impurities, Si / C ≥ 4.7, 1.5% ≤ (Ni+Cu) ≤ 2.5%.

3. The high hardness, toughness and wear-resistant cast steel according to claim 2, characterized in that: Measured by mass percentage, the chemical composition of the high hardness, toughness and wear-resistant cast steel 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%, and the remainder is iron and unavoidable impurities.

4. A method for preparing the high hardness, toughness and wear-resistant cast steel according to claim 1, 2 or 3, characterized in that: The following steps are involved: S1) smelting: smelting pig iron, scrap steel, pure iron metal and ferroalloy, and subjecting the smelted steel liquid to inoculation and modification with a rare earth alloy to obtain a 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: performing sand removal treatment on the casting obtained in step S2, and then heating it, keeping it warm, and then air cooling it to room temperature to obtain a normalized casting; S4) austempering: reheating the normalized casting obtained in step S3, keeping the temperature, and then austempering and keeping the temperature, and then air-cooling to room temperature again to obtain an austempering casting; S5) Tempering: The casting obtained in step S4 after austempering is tempered again and then air-cooled to room temperature to obtain a high-hardness, toughness, and wear-resistant cast steel.

5. The method for preparing high hardness, toughness and wear-resistant cast steel according to claim 4, characterized in that: The heating in step S3 is heating to 950-1050° C., and the heat preservation time is 4-8 hours.

6. The method for preparing high hardness, toughness, and wear-resistant cast steel according to claim 4, characterized in that: The reheating temperature in step S4 is 940-980° C., and the insulation time is 4-8 hours.

7. The method for preparing high hardness, toughness and wear-resistant cast steel according to claim 4, characterized in that: The isothermal quenching temperature in step S4 is 200-260° C., and the holding time is 2-6 hours.

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

9. The method for preparing high hardness and toughness martensitic wear-resistant cast steel according to claim 4, characterized in that: The temperature of the tempering treatment in step S5 is 180-240° C., and the holding time is 4-10 hours.

10. Use of the high hardness, toughness, wear-resistant and corrosion-resistant cast steel according to any one of claims 1 to 3 in manufacturing wear-resistant parts or corrosion-resistant parts.

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