A wear-resistant steel with both high hardness and excellent impact toughness and its preparation method

Abstract

This invention relates to the field of wear-resistant steel technology, and more specifically to a wear-resistant steel with both high hardness and excellent impact toughness, and its preparation method. To overcome the defects and shortcomings still existing in the current research and development of high-stress impact wear parts, the preparation method of this application includes repeated temperature control during smelting, casting, normalizing, isothermal quenching, and tempering. The resulting wear-resistant steel has the following chemical composition and mass percentages: C: 0.25-0.42%, Si: 1.0-2.0%, Mn: 0.8-1.5%, Cr: 1.2-1.6%, Ni: 0.5-1.0%, Mo: 0.3-0.5%, Cu: 0.4-0.7%, RE: 0.03-0.08%, P≤0.032%, S≤0.040%, with the balance being Fe and unavoidable impurities; and (Mn+Ni+Cu)≥2.0%. The method optimizes the alloy composition and rationally designs the isothermal quenching process below the Ms point, enabling the martensitic + metastable austenitic steel to maintain high hardness while retaining excellent toughness, overcoming the shortcomings of traditional technologies. Combining high hardness and excellent impact toughness, this martensitic wear-resistant steel exhibits better wear resistance under high stress than traditional water-quenched martensitic steel and isothermally quenched bainitic steel.

Description

Technical Field

[0001] This invention relates to the field of wear-resistant steel technology, and more specifically to a wear-resistant steel with both high hardness and excellent impact toughness, and its preparation method. Background Technology

[0002] High-stress impact abrasive wear is a special type of wear in engineering, commonly found in metallurgy, mineral processing, cement, chemical, and power coal milling fields, such as excavator bucket teeth and semi-autogenous mill liners. Due to the combined effects of high loads and abrasive wear, components fail prematurely. For example, due to repeated impact wear from ore and grinding balls, liners have become the most easily worn parts of semi-autogenous mills, accounting for one-third of their production cost. Hundreds of thousands of tons of semi-autogenous mill liners are consumed annually due to impact wear. Research on the failure behavior of semi-autogenous mill liners shows that liner materials need to possess good toughness to inhibit crack initiation and propagation under impact loads, while also needing high hardness to resist micro-cutting by abrasives. Therefore, developing materials with both high hardness and high impact toughness has always been a key focus and hot topic in the field of wear-resistant cast steel.

[0003] A method for preparing a bimetallic composite bainitic-martensitic multiphase steel wear-resistant liner is disclosed in announcement number CN105856725A. The resulting liner has an inner layer hardness of 55-57 hRC and an impact toughness of 11-14 J / cm², while the outer layer has a hardness of 45-50 hRC and an impact toughness of 19-21 J / cm². However, the impact toughness of the aforementioned multiphase steel wear-resistant liner remains relatively low, limiting its application to medium and small-sized mills. With my country's economic development, the volume of materials requiring crushing and grinding is increasing daily, and medium and small-sized mills will gradually be replaced by large, efficient, and energy-saving mills. The increasing size of mills places higher demands on the comprehensive mechanical properties of wear-resistant cast steel, especially its impact toughness.

[0004] A method for preparing bainitic wear-resistant cast steel, disclosed in announcement number CN102877008B, yields a bainitic wear-resistant cast steel with an HRC of 45–52 and a V-notch impact absorption energy of 25–35 J, suitable for high-stress impact abrasive wear conditions. However, to obtain the aforementioned bainitic structure with both high hardness and high toughness, the isothermal quenching temperature is 280–360℃, higher than the martensitic transformation point temperature. The isothermal time is 4–8 hours, which is relatively long. Both the increased isothermal temperature and duration lead to reduced equipment utilization efficiency and significantly increased material production costs, thus limiting the application of bainitic wear-resistant cast steel.

[0005] In addition, high-manganese steel and pearlitic steel are also commonly used materials for mill liners. While high-manganese steel possesses excellent impact toughness (absorbing over 118J of U-notch impact energy) and significant hardening capacity under high stress (from 200-260 hV in the matrix to 580-620 hV in the hardened structure), making it a preferred material for semi-autogenous mill liners, its low yield strength makes it prone to plastic deformation under impact during use, leading to premature failure and significant difficulties in maintenance and disassembly. Pearlitic steel, on the other hand, has sufficient toughness but insufficient hardness, resulting in more severe wear failure. Therefore, there are still shortcomings and deficiencies in the current research and development of high-stress impact wear-resistant components. Summary of the Invention

[0006] This invention provides a wear-resistant steel with both high hardness and excellent impact toughness, and a method for preparing the same. The aim is to significantly improve the hardness and toughness of the wear-resistant steel through a reasonable processing method.

[0007] The above objectives are achieved through the following technical solutions:

[0008] A method for preparing wear-resistant steel with both high hardness and excellent impact toughness includes the following steps:

[0009] S1. Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace to smelt and obtain molten steel. The steel ladle is placed in the casting equipment to solidify, and the molten steel is placed in the steel ladle.

[0010] S2. Casting: The molten steel to be poured is placed in the pouring gate of the mold, and solidified and cooled to obtain the casting;

[0011] S3. Normalizing: The casting is cleaned of sand and then sent to a heat treatment furnace for heating and holding. After heating, it is air-cooled to room temperature to obtain the normalized casting.

[0012] S4. Isothermal quenching: The casting after normalizing is reheated, held at the temperature, and then sent to a salt bath furnace for isothermal quenching and holding. Then it is taken out of the furnace and air-cooled to room temperature to obtain the casting after isothermal quenching.

[0013] S5. Tempering: The isothermal quenched castings are sent back to the heat treatment furnace and heated to 250°C and held at that temperature. Then they are air-cooled to room temperature to obtain wear-resistant steel with both high hardness and excellent impact toughness.

[0014] Furthermore, the metal includes pig iron, scrap steel, pure iron metal, and iron alloys.

[0015] Furthermore, the salt bath medium comprises 45% NaNO2 and 55% KNO3 by mass percentage.

[0016] Furthermore, in step S1, the molten steel is placed in a steel container and subjected to inoculation and modification treatment using rare earth ferrosilicon alloy.

[0017] Furthermore, in step S3, the temperature is heated to 950-1050℃ and held for 4-8 hours.

[0018] Furthermore, the reheating temperature in S4 is 940-980℃, and the holding time is 4-8h.

[0019] Furthermore, in step S4, the isothermal quenching temperature in the salt bath furnace is 220-260℃, and the holding time is 2-4 hours.

[0020] Furthermore, in step S5, the heating temperature is 250°C, and the holding time is 12 hours.

[0021] The wear-resistant steel with high hardness and excellent impact toughness prepared by the above-mentioned method has the following chemical composition and mass percentage: C: 0.25-0.42%, Si: 1.0-2.0%, Mn: 0.8-1.5%, Cr: 1.2-1.6%, Ni: 0.5-1.0%, Mo: 0.3-0.5%, Cu: 0.4-0.7%, RE: 0.03-0.08%, P≤0.032%, S≤0.040%, with the balance being Fe and unavoidable impurities; and (Mn+Ni+Cu)≥2.0%.

[0022] The aforementioned wear-resistant steel, which combines high hardness and excellent impact toughness, is preferably used in abrasive wear conditions.

[0023] The beneficial effects of this invention, which provides a wear-resistant steel with both high hardness and excellent impact toughness, and its preparation method, are as follows:

[0024] This invention, through optimized alloy composition and a rationally designed isothermal quenching process below the Ms point, enables martensitic + metastable austenitic steel to maintain high hardness while retaining excellent toughness, overcoming the shortcomings of traditional technologies. Combining high hardness and excellent impact toughness, this martensitic wear-resistant steel exhibits better wear resistance under high stress than traditional water-quenched martensitic steel and isothermally quenched bainitic steel. For example, the hardness range of various embodiments of this invention is 471–545 HV, and the V-notch impact absorption energy range is 19.5–32.6 J. Its hardness is slightly lower than that of martensitic cast steel (530 HV), but its impact toughness is significantly higher than that of martensitic cast steel (V-notch impact absorption energy: 13.8 J), and both its hardness and impact toughness are slightly higher than those of bainitic cast steel (hardness: 488 HV, V-notch impact absorption energy: 30.8 J). This application demonstrates a good balance between hardness and toughness, showing promising application prospects in wear-resistant parts under high-stress impact abrasive wear conditions. Attached Figure Description

[0025] Figure 1This is a thermal expansion curve of the wear-resistant steel with high hardness and excellent impact toughness produced in Example 2 of the preparation method of the wear-resistant steel with high hardness and excellent impact toughness of the present invention.

[0026] Figure 2 A contrast image of the Kikuchi belt produced in Embodiment 2 of the present invention, which combines high hardness and excellent impact toughness.

[0027] Figure 3 This is a phase composition diagram of the high-hardness and high-toughness martensitic wear-resistant cast steel produced in Example 2 of the present invention, which shows the presence of martensite and retained austenite phases.

[0028] Figure 4 This is a schematic diagram of the overall structure of the casting operation equipment;

[0029] Figure 5 This is a schematic diagram of the frame structure;

[0030] Figure 6 This is a structural diagram of the connecting components;

[0031] Figure 7 This is a schematic diagram showing the positional relationship between the fixed rod, limit rod I, limit rod II, and limit rod III.

[0032] Figure 8 This is a structural diagram of the guide seat and the fixing rod;

[0033] Figure 9 This is a structural schematic diagram of shaft I, base I, annular groove, and bending seat I;

[0034] Figure 10 A schematic diagram of shaft I, base I, and bending seat I;

[0035] Figure 11 This is a structural diagram of the telescopic cylinder, base II, limit rod I, limit rod II, limit rod III, stabilizing rod, motor I, and gear I;

[0036] Figure 12 This is a structural diagram of shaft II, gear II, disc, bending seat II, straight rod, friction ring, and force-bearing plate;

[0037] Figure 13 This is a schematic diagram of the frame structure. Detailed Implementation

[0038] A method for preparing wear-resistant steel with both high hardness and excellent impact toughness:

[0039] Example 1 includes the following steps:

[0040] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The steel ladle is placed in the casting operation equipment and fixed. The molten steel is placed in the steel ladle and inoculated with rare earth ferrosilicon alloy to obtain the molten steel to be poured.

[0041] S2) Casting: The molten steel to be poured is placed in the pouring gate of the mold, and solidified and cooled to obtain the casting;

[0042] S3) Normalizing: The casting is cleaned of sand and then sent to a heat treatment furnace, heated to 1050℃, held for 5 hours and then air-cooled to room temperature to obtain the normalized casting.

[0043] S4) Isothermal quenching: The normalized casting is reheated to 940℃ and held for 6 hours, then sent to a 260℃ salt bath furnace for isothermal quenching and holding for 2.5 hours; the salt bath medium consists of 45% NaNO2 and 55% KNO3. Then it is taken out of the furnace and air-cooled to room temperature to obtain the isothermal quenched casting.

[0044] S5) Tempering: The castings after isothermal quenching are sent back into the heat treatment furnace and heated to 250℃ and held for 12 hours. They are then air-cooled to room temperature to obtain wear-resistant steel with both high hardness and excellent impact toughness.

[0045] The chemical composition of the wear-resistant steel, which combines high hardness and excellent impact toughness, is as follows (by mass percentage): C: 0.25%, Si: 1.1%, Mn: 1.4%, Cr: 1.2%, Ni: 0.9%, Mo: 0.3%, Cu: 0.5%, RE: 0.03%, P: 0.023%, S: 0.038%, with the balance being iron and unavoidable impurities.

[0046] Example 2 includes the following steps:

[0047] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The steel ladle is placed in the casting operation equipment and fixed. The molten steel is placed in the steel ladle and inoculated with rare earth ferrosilicon alloy to obtain the molten steel to be poured.

[0048] S2) Casting: The molten steel to be poured is placed in the pouring gate of the mold, and solidified and cooled to obtain the casting;

[0049] S3) Normalizing: The casting is cleaned of sand and then sent to a heat treatment furnace, heated to 1000℃, held for 5 hours and then air-cooled to room temperature to obtain the normalized casting.

[0050] S4) Isothermal quenching: The normalized casting is reheated to 940℃ and held for 6 hours. Then it is sent to a 250℃ salt bath furnace for isothermal quenching and held for 3 hours. The salt bath medium consists of 45% NaNO2 and 55% KNO3. Then it is taken out of the furnace and air-cooled to room temperature to obtain the isothermal quenched casting.

[0051] S5) Tempering: The castings after isothermal quenching are sent back into the heat treatment furnace and heated to 250℃ and held for 12 hours. They are then air-cooled to room temperature to obtain wear-resistant steel with both high hardness and excellent impact toughness.

[0052] The chemical composition and mass content of the wear-resistant steel with both high hardness and excellent impact toughness are as follows: C: 0.30%, Si: 1.3%, Mn: 1.3%, Ni: 0.8%, Cr: 1.2%, Mo: 0.4%, Cu: 0.5%, RE: 0.03%, P: 0.022%, S: 0.030%, with the balance being iron and unavoidable impurities.

[0053] Figure 2 and Figure 3 This shows the martensite and retained austenite microstructure in the steel.

[0054] Example 3 includes the following steps:

[0055] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The steel ladle is placed in the casting operation equipment and fixed. The molten steel is placed in the steel ladle and inoculated with rare earth ferrosilicon alloy to obtain the molten steel to be poured.

[0056] S2) Casting: The molten steel to be poured is placed in the pouring gate of the mold, and solidified and cooled to obtain the casting;

[0057] S3) Normalizing: The casting is cleaned of sand and then sent to a heat treatment furnace, heated to 980℃, held for 6 hours and then air-cooled to room temperature to obtain the normalized casting.

[0058] S4) Isothermal quenching: The normalized casting is reheated to 940℃ and held for 6 hours. Then it is sent to a 250℃ salt bath furnace for isothermal quenching and held for 3 hours. The salt bath medium consists of 45% NaNO2 and 55% KNO3. Then it is taken out of the furnace and air-cooled to room temperature to obtain the isothermal quenched casting.

[0059] S5) Tempering: The isothermal quenched casting is sent back into the heat treatment furnace and heated to 250°C and held for 12 hours. It is then air-cooled to room temperature to obtain wear-resistant steel with both high hardness and excellent impact toughness. The martensitic phase transformation temperature of the wear-resistant steel with both high hardness and excellent impact toughness of this invention is calculated to be 320°C.

[0060] The chemical composition and mass content of the wear-resistant steel with high hardness and excellent impact toughness are as follows: C: 0.34%, Si: 1.5%, Mn: 1.1%, Ni: 0.7%, Cr: 1.1%, Mo: 0.3%, Cu: 0.5%, RE: 0.04%, P: 0.024%, S: 0.030%, with the balance being iron and unavoidable impurities.

[0061] Example 4 includes the following steps:

[0062] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The steel ladle is placed in the casting operation equipment and fixed. The molten steel is placed in the steel ladle and inoculated with rare earth ferrosilicon alloy to obtain the molten steel to be poured.

[0063] S2) Casting: The molten steel to be poured is placed in the pouring gate of the mold, and solidified and cooled to obtain the casting;

[0064] S3) Normalizing: The casting obtained in step S2 is cleaned of sand and then sent to a heat treatment furnace, heated to 1000℃, held for 6 hours and then air-cooled to room temperature to obtain the normalized casting.

[0065] S4) Isothermal quenching: The normalized casting is reheated to 940℃ and held for 6 hours. Then it is sent to a 240℃ salt bath furnace for isothermal quenching and held for 4 hours. The salt bath medium consists of 45% NaNO2 and 55% KNO3. Then it is taken out of the furnace and air-cooled to room temperature to obtain the isothermal quenched casting.

[0066] S5) Tempering: The castings after isothermal quenching are sent back into the heat treatment furnace and heated to 250℃ and held for 12 hours. They are then air-cooled to room temperature to obtain wear-resistant steel with both high hardness and excellent impact toughness.

[0067] The chemical composition and mass content of the wear-resistant steel with both high hardness and excellent impact toughness are as follows: C: 0.38%, Si: 1.7%, Mn: 1.0%, Ni: 0.8%, Cr: 1.3%, Mo: 0.5%, Cu: 0.4%, RE: 0.03%, P: 0.022%, S: 0.035%, with the balance being iron and unavoidable impurities.

[0068] Example 5 includes the following steps:

[0069] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The steel ladle is placed in the casting operation equipment and fixed. The molten steel is placed in the steel ladle and inoculated with rare earth ferrosilicon alloy to obtain the molten steel to be poured.

[0070] S2) Casting: The molten steel to be poured is placed in the pouring gate of the mold, and solidified and cooled to obtain the casting;

[0071] S3) Normalizing: The casting obtained in step S2 is cleaned of sand and then sent to a heat treatment furnace, heated to 980°C, held for 6 hours and then air-cooled to room temperature to obtain the normalized casting.

[0072] S4) Isothermal quenching: The casting after normalizing in step S3 is reheated to 940℃ and held for 6 hours. Then it is sent to a 230℃ salt bath furnace for isothermal quenching and held for 4 hours. The salt bath medium consists of 45% NaNO2 and 55% KNO3. Then it is taken out of the furnace and air-cooled to room temperature to obtain the casting after isothermal quenching.

[0073] S5) Tempering: The castings after isothermal quenching in step S4 are sent back into the heat treatment furnace and heated to 250℃ and held for 12 hours. They are then air-cooled to room temperature to obtain wear-resistant steel with both high hardness and excellent impact toughness.

[0074] The chemical composition and mass content of the wear-resistant steel with both high hardness and excellent impact toughness are as follows: C: 0.42%, Si: 2.0%, Mn: 1.0%, Ni: 0.8%, Cr: 1.5%, Mo: 0.4%, Cu: 0.4%, RE: 0.03%, P: 0.022%, S: 0.032%, with the balance being iron and unavoidable impurities.

[0075] Comparative Example 1: The preparation method of conventional quenched martensitic wear-resistant cast steel includes the following steps:

[0076] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The molten steel is placed in a steel container and inoculated with rare earth ferrosilicon alloy to obtain molten steel to be cast.

[0077] 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.

[0078] S3) Normalizing: The casting obtained in step S2 is cleaned of sand, then sent to a heat treatment furnace, heated to 1000℃, held for 5 hours and then air-cooled to room temperature to obtain the normalized casting.

[0079] S4) Isothermal quenching: The normalized casting is reheated to 940℃, held for 6 hours, and then water quenched to room temperature to obtain the casting after conventional water quenching.

[0080] S5) Tempering: The castings after conventional water quenching are sent back into the heat treatment furnace and heated to 250℃ and held for 12 hours. They are then air-cooled to room temperature to obtain conventional water-quenched martensitic wear-resistant steel.

[0081] The chemical composition and mass content of the conventional quenched martensitic wear-resistant cast steel are as follows: C: 0.30%, Si: 1.3%, Mn: 1.3%, Ni: 0.8%, Cr: 1.2%, Mo: 0.4%, Cu: 0.5%, RE: 0.03%, P: 0.022%, S: 0.030%, with the balance being iron and unavoidable impurities.

[0082] Comparative Example 2: The preparation method of conventional isothermal bainitic wear-resistant cast steel includes the following steps:

[0083] S1) Smelting: Pig iron, scrap steel, pure iron metal and ferroalloys are added to an electric furnace for smelting. The steel ladle is placed in the casting operation equipment and fixed. The molten steel is placed in the steel ladle and inoculated with rare earth ferrosilicon alloy to obtain the molten steel to be poured.

[0084] S2) Casting: The molten steel to be poured is placed in the pouring gate of the mold, and solidified and cooled to obtain the casting;

[0085] S3) Normalizing: The obtained castings are cleaned of sand and then sent to a heat treatment furnace, heated to 1000℃, held for 5 hours and then air-cooled to room temperature to obtain the normalized castings.

[0086] S4) Isothermal quenching: The normalized casting is reheated to 940℃ and held for 6 hours. Then it is sent to a 330℃ salt bath furnace for isothermal quenching and held for 6 hours. The salt bath medium consists of 45% NaNO2 and 55% KNO3. Then it is taken out of the furnace and air-cooled to room temperature to obtain the isothermal quenched casting, which is a conventional casting.

[0087] S5) Tempering: The castings after conventional water quenching in step S4 are sent back into the heat treatment furnace and heated to 250℃ and held for 12 hours. They are then air-cooled to room temperature to obtain conventional isothermal bainitic wear-resistant cast steel.

[0088] The chemical composition and mass content of conventional isothermal bainitic wear-resistant cast steel are as follows: C: 0.30%, Si:

[0089] 1.3%, Mn: 1.3%, Ni: 0.8%, Cr: 1.2%, Mo: 0.4%, Cu: 0.5%, RE: 0.03%, P: 0.022%, S: 0.030%, balance is iron and unavoidable impurities.

[0090] Among them, reference Figure 4 and 5 Because casting operations are relatively dangerous, especially the receiving of molten steel and during casting, although manual operation can improve the quality of castings based on experience, the risk is high due to excessively high temperatures. The casting operation equipment includes a frame-shaped machine (1), and the inner end face of the vertical section of the machine (1) is provided with longitudinal channels, for reference. Figure 6 It also includes a connecting component, which includes a guide (21), combined with Figure 8 A fixing rod (22) is fixedly connected to the upper side of the right end of the guide seat (21);

[0091] Furthermore, the guide seat (21) is rotatably connected to the center of shaft I (23), and a base I (24) is fixedly connected to the left side of shaft I (23). Each of the four corners of the guide seat (21) has a mounting hole I, and each of the four corners of the base I (24) has a mounting hole II. The axes of the four mounting holes I and the four mounting holes II are respectively aligned, so that the base I (24) and the guide seat (21) can be detachably fixed by using bolt and nut assemblies passing through the mounting holes I and II. The left end of the base I (24) has an annular groove (…). 25), the center of the annular groove (25) coincides with the axis of shaft I (23), the right end of the fixing rod (22) is fitted with clearance in the annular groove (25), a bending seat I (26) is fixed on the base I (24), the bent section of the bending seat I (26) is located on the right side of the base I (24), a telescopic cylinder (31) is fixed on the left end of the base I (24), the left end of the telescopic cylinder (31) is located on the right side of the guide seat (21), the movable end of the telescopic cylinder (31) passes through the base I (24) from left to right, combined with Figure 11 A base II (32) is fixedly connected to the movable end of the telescopic cylinder (31). A limiting rod I (33) is fixedly connected to the upper side of the left end of the base II (32). A limiting rod II (34) is fixedly connected to the lower side of the left end of the base II (32). A limiting rod III (35) located in front of the limiting rod I (33) is fixedly connected to the upper side of the left end of the base II (32). The limiting rod I (33), limiting rod II (34) and limiting rod III (35) pass through the base I (24) from right to left. The diameter of the hole in the base I (24) that mates with the limiting rod I (33), limiting rod II (34) and limiting rod III (35) is preferably slightly larger than the diameter of the limiting rod I (33), limiting rod II (34) and limiting rod III (35). The limiting rod III (35) is located in front of the fixed rod (22). 3) Located on the rear side of the fixed rod (22), there is a gap between the limiting rod III (35) and the fixed rod (22), and there is a gap between the limiting rod III (35) and the fixed rod (22), so that the base I (24) can swing back and forth within an acute angle range relative to the fixed rod (22). The right end of the base II (32) is fixedly connected to the stabilizing rod (36), and the stabilizing rod (36) is slidably connected to the bending seat I (26). When the telescopic cylinder (31) is started, it can drive the base II (32) to move to the right, so that the limiting rod I (33), the limiting rod II (34), the limiting rod III (35) and the gear I (38) can move left and right. The left end of the limiting rod III (35) is located on the right side of the limiting rod I (33). The motor I (37) preferably has a brake function, such as an electromagnetic brake.

[0092] Furthermore, a motor I (37) is fixedly connected to the right end of the base II (32). The output shaft of the motor I (37) is set to the right. A gear I (38) is fixedly connected to the output shaft of the motor I (37). A circular groove is provided at the right end of the shaft I (23). A shaft II (41) is rotatably connected to the circular groove of the shaft I (23) through a bearing. The outer ring of the bearing is fixedly connected to the inner wall of the shaft I (23). The inner ring of the bearing is fixedly connected to the outer circumference of the shaft II (41). A flange I is integrally connected to the right end of the shaft I (23). A flange II is integrally connected to the left side of the shaft II (41). The flange I and the flange II are detachably fixedly connected by a bolt and nut assembly. A gear II (42) located on the right side of the flange II is fixedly connected to the shaft II (41). The right end of the gear I (38) abuts against the left end of the gear II (42). When the gear I (38) and the gear II (42) rotate relative to each other and move towards each other, they can mesh to achieve transmission.

[0093] Furthermore, in combination Figure 12 A disc (43) is fixed to the right end of gear II (42). Multiple bending seats II (44) are fixed to the right end of disc (43). A straight rod (45) is fixed to the left end of bending seat II (44). The straight rod (45) is slidably connected to disc (43). The straight rod (45) passes through disc (43) from right to left. Multiple straight rods (45) are evenly distributed circumferentially. The left end of multiple straight rods (45) is fixed to the same friction ring (46). A force-bearing plate (47) is fixed to the straight rod (45). The force-bearing plate (47) is located between disc (43) and bending seat II (44). A compression spring is sleeved on the straight rod (45). The two ends of the compression spring are in contact with the bending seat II (44) and the force plate (47) respectively, and the left end of the friction ring (46) is in contact with the right end face of the gear I (38) to achieve friction transmission. When the flange I and the flange II are disassembled, the motor I (37) is started. The output shaft of the motor I (37) drives the gear I (38) to rotate. The gear I (38) drives the friction ring (46) to rotate. The friction ring (46) drives the shaft II (41) to rotate, so that the gear II (42) rotates around the shaft II (41), and the gear I (38) moves to the right until the gear I (38) meshes with the gear II (42).

[0094] The casting operation equipment is symmetrically arranged in the left and right radial directions and includes a clamp (51). The left and right ends of the clamp (51) are respectively fixed to the inner ends of two shafts II (41). Two guide seats (21) are respectively slidably connected in the guide grooves at the inner end of the vertical section of the frame (1) to achieve vertical movement. The clamp (51) is used to place the steel drum. The opening of the steel drum faces upward, and the steel drum and the clamp (51) are detachably fixed. Preferably, a screw is threaded to each of the left and right sides of the upper end of the clamp (51). The two screws are distributed in a V shape. The inner ends of the two screws clamp the left and right ends of the steel drum. The front and rear ends of the inner end of the clamp (51) limit the movement of the front and rear ends of the steel drum. A motor II is fixed to the upper end of the frame (1). A roller is fixed to the output shaft of the motor II. One end of a rope is fixed to the roller. The other end of the rope is fixed to the upper end of the frame (1). The rope is preferably a steel cable or iron cable. The frame (1) is fixed to the mobile chassis, which is preferably a base with casters. The upper ends of the caster seats are fixed to the four corners of the lower end of the base. The front end of the frame (51) is fixed with a handle that extends forward. The handle is preferably 1 to 2 meters long and is located below the shaft II (41) to form a force-saving lever.

[0095] The casting operation equipment can be operated manually or electrically. In manual operation, flange I and flange II are fixedly connected. The bolt and nut assembly between guide seat (21) and base I (24) is removed. Since the fixed rod (22) is located between limit rod I (33) and limit rod II (34), the rotation range of shaft II (41) is acute. Shaft II (41) is used to drive the bracket (51) and the steel bucket on the bracket (51) to swing, so that the operator can pull the handle to slightly adjust the elevation angle of the opening of the steel bucket, so as to better receive the molten steel poured down from the top of the steel bucket. This acute angle range will not cause the molten steel to be poured out, and it is also convenient for the operator to manually pull the handle to move the chassis. Furthermore, when the telescopic cylinder (31) is started, base II (32) moves to the right until the limit rod III (35) is located on the right side of the fixed rod (22), and the limit rod I (33) is still located in the annular groove (25). At this time, the operator can face one side of his body. When the handle is pulled from the front, the limiting rod I (33) rotates counterclockwise away from the fixed rod (22) when viewed from the right. At this time, both shaft I (23) and shaft II (41) rotate counterclockwise to drive the bracket (51) to rotate counterclockwise. At the same time, the limiting rod II (34) limits the rotation range to nearly 180 degrees, preventing the steel drum opening from facing the operator when it is facing down. The operator also pulls the handle away from the steel drum, making it safer. When electric control operation is required, the guide seat (21) and The base I (24) is fixed by bolt and nut assembly. The bolt and nut assembly between flange I and flange II is disassembled, so that gear I (38) and gear II (42) mesh. Gear I (38) drives gear II (42) to rotate, and gear II (42) drives shaft II (41) to rotate, which can control the flexible rotation of the bracket (51). At this time, limit rod I (33), limit rod II (34) and limit rod III (35) should all be located on the right side of the fixed rod (22).

[0096] Example and Comparative Material Performance Tests

[0097] Experimental Methods: Performance tests were conducted on the cast steel prepared in Examples 1-5 and the liners prepared in Comparative Examples 1 and 2. The impact test used V-notch impact specimens of 10×10×55mm³. Before the Vickers hardness test, the test surfaces of the specimens were ground and polished. The test load was 50g, and the loading time was 15s. The impact abrasive wear test was conducted on an MLD-10 dynamic load abrasive wear testing machine. The wear impact energy was 3J, the impact frequency was 100 times per minute, the lower specimen was 45# steel, the rotation speed was 100 revolutions per minute, and the abrasive used was quartz sand with a particle size between 60 and 80 mesh. The abrasive flow rate was controlled at approximately 50 kg per hour. Each group of specimens needed to be pre-ground for 30 minutes before the test. During the impact wear process, the weight loss was measured once every 30 minutes as one wear cycle. A total of five cycles were conducted, for a total of 2.5 hours. The test results are listed in Table 1.

[0098] Table 1 Performance Test Results

[0099]

[0100]

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

[0102] Table 1 shows that the V-notch impact absorption energy of the high-hardness and high-toughness martensitic wear-resistant cast steel prepared by the present invention can reach 19.5-32.6 J, while the hardness can reach 471-545 hV, possessing both high hardness and high toughness. Under the same composition but different process treatment, the hardness of Example 2 is reduced by about 6.8% (32 hV) compared with Comparative Example 1, but the V-notch impact absorption energy of the former is 2.36 times that of the latter. At the same time, the hardness and impact toughness of Example 2 are slightly higher than those of Comparative Example 2. The obvious difference between the present invention and existing cast steel is that (1) it has a higher content of element Si and a certain content of Mn, Ni and Cu, where (Mn+Ni+Cu)≥2.0%. The precipitation of carbides will significantly reduce the impact toughness of the material, and the element Si helps to suppress the precipitation of carbides during the isothermal process. C, Mn, Ni and Cu are stable austenite elements, which can ensure that a certain amount of metastable austenite remains in the martensitic matrix. Too little Cu, Mn and Ni not only makes it difficult to guarantee the hardenability of steel, but also weakens the stability of the retained austenite, making it difficult to guarantee excellent toughness and plasticity. In addition, rapid cooling to below the martensitic transformation temperature (Ms) of 220-260℃ and holding for a period of time promotes the diffusion of supersaturated carbon atoms in martensite into the retained austenite, obtaining a certain amount of metastable retained austenite. (2) Quenching to below Ms point and holding for a period of time. During the isothermal process, supersaturated carbon atoms in martensite diffuse into the retained austenite, obtaining "carbon-rich" retained austenite, which significantly improves the stability of retained austenite and thus improves impact toughness. In addition, the content of retained austenite and the diffusion thermal / kinetic behavior of carbon atoms are significantly affected by the isothermal temperature and isothermal time. For example, if the temperature is too high, the volume fraction of retained austenite increases, which leads to a decrease in its internal average carbon content, a decrease in stability, and thus a deterioration in impact toughness.

Claims

1. A method for preparing wear-resistant steel with both high hardness and excellent impact toughness, characterized in that, Includes the following steps: S1. Smelting: Metal is added to an electric furnace for smelting to obtain molten steel. The steel ladle is placed in the casting equipment for fixation, and the molten steel is placed in the steel ladle. S2. Casting: The molten steel to be poured is placed in the pouring gate of the mold, and solidified and cooled to obtain the casting; S3. Normalizing: The casting is cleaned of sand and then sent to a heat treatment furnace for heating and holding. After heating, it is air-cooled to room temperature to obtain the normalized casting. S4. Isothermal quenching: After normalizing, the casting is reheated and held at the same temperature. Then it is sent to a salt bath furnace at 220-260℃ for isothermal quenching and held at the same temperature for 2-4 hours. Then it is taken out of the furnace and air-cooled to room temperature to obtain the casting after isothermal quenching. S5. Tempering: The castings after isothermal quenching are sent back into the heat treatment furnace and heated to 250°C and held at that temperature. Then they are air-cooled to room temperature to obtain wear-resistant steel with both high hardness and excellent impact toughness. The chemical composition and mass percentage of the wear-resistant steel with both high hardness and excellent impact toughness are as follows: C: 0.25-0.42%, Si: 1.0-2.0%, Mn: 0.8-1.5%, Cr: 1.2-1.6%, Ni: 0.5-1.0%, Mo: 0.3-0.5%, Cu: 0.4-0.7%, RE: 0.03-0.08%, P≤0.032%, S≤0.040%, with the balance being Fe and unavoidable impurities; and (Mn+Ni+Cu)≥2.0%.

2. The method for preparing wear-resistant steel with both high hardness and excellent impact toughness according to claim 1, characterized in that, The metals include pig iron, scrap steel, pure iron metal, and iron alloys.

3. The method for preparing wear-resistant steel with both high hardness and excellent impact toughness according to claim 1, characterized in that, The salt bath medium consists of 45% NaNO2 and 55% KNO3 by mass percentage.

4. The method for preparing wear-resistant steel with both high hardness and excellent impact toughness according to claim 1, characterized in that, In step S1, the molten steel is placed in a steel container and subjected to inoculation and modification treatment using rare earth ferrosilicon alloy.

5. The method for preparing wear-resistant steel with both high hardness and excellent impact toughness according to claim 1, characterized in that, The temperature in step S3 is heated to 950-1050℃ and held for 4-8 hours.

6. The method for preparing wear-resistant steel with both high hardness and excellent impact toughness according to claim 1, characterized in that, The reheating temperature in S4 is 940-980℃, and the holding time is 4-8h.

7. In the method for preparing wear-resistant steel with both high hardness and excellent impact toughness according to claim 1, in step S5, the heating temperature is 250°C and the holding time is 12h.

8. Wear-resistant steel with high hardness and excellent impact toughness prepared by the preparation method of wear-resistant steel with high hardness and excellent impact toughness according to any one of claims 1 to 7.

9. An application of the wear-resistant steel with high hardness and excellent impact toughness as described in claim 8, characterized in that, It is used in abrasive wear conditions.

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