Medium alloy wear-resistant cast steel and its preparation method

Abstract

The application belongs to the technical field of alloys, and particularly discloses a medium-alloy wear-resistant cast steel and a preparation method thereof; the medium-alloy wear-resistant cast steel is composed of the following elements in percentage by mass: C 0.27-0.34%, Si 2.25-2.55%, Mn 2.00-3.50%, Cr 0.1-0.3%, precious metal ≤0.3%, Ti 0.01-0.05%, V 0.06-0.10%, Al 0.02-0.05%, N 0.03-0.08%, S ≤0.02%, P ≤0.02%, unavoidable impurities, and the balance of Fe; the medium-alloy wear-resistant cast steel is prepared by optimizing the chemical composition elements of the alloy, so that the prepared alloy has higher Rockwell hardness, higher room temperature impact absorption energy, excellent tensile strength and wear resistance, and can be used in wear-resistant parts of mechanical equipment.

Description

Technical Field

[0001] This invention belongs to the field of alloy technology, and specifically relates to a medium alloy wear-resistant cast steel and its preparation method. Background Technology

[0002] Medium-alloy wear-resistant cast steel is widely used in high-end grinding, crushing, and excavating machinery in mining, construction, cement, metallurgy, and marine industries, and is a key material affecting the efficiency of mechanical operations. Currently widely used silicon-manganese and low-chromium low-alloy wear-resistant cast steels suffer from difficulties in achieving a balance between strength, Rockwell hardness, and toughness, resulting in limited improvements in wear resistance. While ensuring control over the content of precious metal elements, increasing the content of low-cost elements such as Si and Mn, as well as micro-alloying modification, holds promise for breaking through the material's performance limits and offering high cost-effectiveness. However, these medium-alloy cast steels often exhibit insufficient strength, brittleness, and require long and complex manufacturing processes, necessitating breakthroughs in material design and preparation technologies.

[0003] CN112195417A discloses a high wear-resistant and high-strength-toughness excavator bucket tooth steel bar and its preparation method. Its chemical composition is as follows: C: 0.18%-0.22%; Si: 2.1%-2.5%; Mn: 2.8%-3.2%; Cr: 0.35%-0.55%; Mo: 0.07-0.13%; Ni: 0.35%-0.45%; V: 0.010%-0.015%; Ti: 0.06%-0.10%; B: 0.0015%-0.0035%; N: 0.010%-0.015%; Al: 0.035%-0.065%; P≤0.015%; S≤0.010%; balance Fe. The steel bars used for bucket teeth need to undergo blast furnace smelting, LF and VD refining, and subsequent series of heat treatments. The overall preparation process is lengthy, and only the steel bars for bucket teeth are obtained; further complex processing is required to produce the final product components.

[0004] CN111996436A discloses a large excavator bucket tooth and its manufacturing method. It is made of silicon-manganese medium-carbon alloy steel with the following chemical composition and mass fraction: C: 0.41-0.48%, Si: 2.85-2.97%, Mn: 2.17-2.34%, P: <0.035%, S: <0.030%, Cr: 0.55-0.70%, B: 0.0033-0.0057%, Al: 0.016-0.037%, with the balance being Fe. The tooth steel obtained after undergoing complex graded double-cooling rapid heat treatment has high hardness, but its impact toughness is <25 J / cm². 2 With a tensile strength of <1600 MPa, it still poses a safety hazard of fracture and spalling under strong impact conditions.

[0005] CN102877008A discloses a method for preparing bainitic wear-resistant cast steel, with the following chemical composition: C: 0.2-0.6%; Si: 0.7-2.5%; Mn: 0.3-3.0%; Mo: 0.1-1.5%; Cr: 0.2-3.0%; Ti≤0.5%; V≤0.5%; RE≤0.5%; S, P≤0.06%, with the remainder being Fe. This cast steel can achieve a bainitic structure after high-temperature holding and isothermal quenching in a salt bath. It has advantages such as relatively low cost and a good balance of strength and toughness. However, its overall strength (1206~1321 MPa) and toughness (10.1-25.6 J) still have room for improvement.

[0006] In summary, medium alloy wear-resistant cast steel exhibits good performance potential. However, the key to promoting the industry's development lies in how to fully utilize the material's potential and achieve a high level of matching between strength, hardness, and toughness, while ensuring relatively low element costs and relatively short process flow, so as to support the safe and long-term service of mechanical wear-resistant parts. Summary of the Invention

[0007] In order to overcome at least one of the technical problems existing in the prior art, one of the objectives of the present invention is to provide a medium alloy wear-resistant cast steel.

[0008] The second objective of this invention is to provide a method for preparing medium alloy wear-resistant cast steel.

[0009] The third objective of this invention is to provide a wear-resistant component for mechanical equipment.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a medium-alloy wear-resistant cast steel, wherein the medium-alloy wear-resistant cast steel is composed of the following elements in mass percentage: C 0.27-0.34%, Si 2.25-2.55%, Mn 2.00-3.50%, Cr 0.1-0.3%, precious metals ≤0.3%, Ti 0.01-0.05%, V 0.06-0.10%, Al 0.02-0.05%, N 0.03-0.08%, S ≤0.02%, P ≤0.02%, unavoidable impurities ≤0.2%, and the balance being Fe; The precious metal is selected from at least one of Mo and Ni.

[0011] This invention avoids dependence on precious elements such as molybdenum and nickel, compresses the Cr content to below 0.3%, and ensures that the total amount of precious metals (i.e., Ni and / or Mo) does not exceed 0.3%, thus avoiding the material premium of high-chromium molybdenum alloy systems.

[0012] In some embodiments of the present invention, the mass percentage of C is any value or a range formed by any two of 0.27%, 0.28%, 0.29%, 0.30%, 0.31%, 0.32%, 0.33%, and 0.34%. Carbon is a fundamental element that ensures that medium-alloy wear-resistant cast steel obtains sufficient strength and hardness. In the present invention, carbon forms carbides or carbonitrides with microalloying elements such as vanadium and titanium, producing a dispersion strengthening effect, while cooperating with silicon and manganese to regulate the stability of austenite. If the mass percentage of carbon is less than 0.27%, the strength of medium-alloy wear-resistant cast steel is difficult to meet the requirements of high-stress wear conditions; if the mass percentage of carbon is greater than 0.34%, the toughness is compromised. Limiting carbon to the range of 0.27-0.34% can provide a suitable microstructure basis for subsequent heat treatment while ensuring hardenability.

[0013] In some embodiments of the present invention, the mass percentage of Si is any value or a range formed by any two of 2.25%, 2.30%, 2.35%, 2.40%, 2.45%, 2.50%, and 2.55%. Silicon is one of the core alloying elements of the present invention, and its key role is to strongly suppress the precipitation of carbides during the isothermal transformation, promote the enrichment of carbon into austenite, and ultimately obtain a dual-phase structure composed of carbide-free bainite and carbon-rich austenite. Practice shows that a silicon content of 2.25-2.55% can obtain a dual-phase structure composed entirely of bainitic ferrite and stable retained austenite. If the silicon content is below 2.25%, the effect of suppressing carbides is insufficient; if it is above 2.55%, it is easy to lead to coarsening of the structure and decrease in toughness. Therefore, 2.25-2.55% is selected as the preferred range.

[0014] In some embodiments of the present invention, the medium-alloy wear-resistant cast steel contains carbon-rich austenitic and carbon-free bainitic structures; in some embodiments of the present invention, the medium-alloy wear-resistant cast steel is composed of both carbon-rich austenitic and carbon-free bainitic structures. In the present invention, the alloy matrix of the medium-alloy wear-resistant cast steel is composed of both carbon-rich austenitic and carbon-free bainitic structures, and precipitates selected from at least one of metal carbides, metal nitrides, and metal carbonitrides are distributed within the alloy matrix.

[0015] In some embodiments of the present invention, the mass percentage of Mn is any value or a range formed by any two of the following: 2.00%, 2.20%, 2.40%, 2.50%, 2.60%, 2.80%, 3.00%, 3.20%, 3.40%, and 3.50%. Manganese, as an austenite stabilizing element, works synergistically with silicon and nitrogen in this invention, adjusting its stability by enriching it in austenite. Controlling the manganese content within the range of 2.00-3.50% retains sufficient residual austenite to produce a transformation-induced plasticity effect, while avoiding the problems of high cost and excessively rapid work hardening associated with high-manganese steel (>10%). Practice has shown that within this range, manganese can work with silicon to inhibit carbide formation, which is beneficial for carbon diffusion into austenite, laying the foundation for excellent strength and toughness.

[0016] In some embodiments of the present invention, the mass percentage of Cr is any value or a range formed by any combination of 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.20%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, and 0.30%. Chromium primarily plays a supporting role in improving hardenability in this invention. Although chromium can form carbides to improve wear resistance, excessively high content increases cost and easily forms coarse carbides that impair toughness. Limiting chromium to a low level of 0.1-0.3% is only used to ensure the hardenability of the core in thick-section medium-alloy wear-resistant cast steel, while avoiding adverse interactions with silicon. Within this content range, chromium dissolved in the matrix of medium-alloy wear-resistant cast steel has no negative impact on the uniformity of the microstructure, achieving a balance between cost and performance.

[0017] In some embodiments of this invention, the mass percentage of precious metals is any value or a range formed by any combination of 0%, 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, and 0.3%. This invention strictly controls the total amount of transition elements (i.e., Mo and / or Ni) to no more than 0.3%, which can significantly reduce costs. Although nickel can improve toughness and hardenability, and molybdenum can prevent temper brittleness, both are expensive alloying elements. Through the synergistic design of high silicon, medium manganese, nitrogen, and vanadium, the target strength and toughness can be achieved without relying on nickel and molybdenum for strengthening. This limitation can significantly reduce alloy costs, meeting the economic requirements of industrial applications, while avoiding the complexity of heat treatment processes caused by excessive alloying elements.

[0018] In some embodiments of the present invention, the mass percentage of Ti is any value or a range formed by any combination of 0.01%, 0.02%, 0.03%, 0.04%, and 0.05%. Titanium is a strong nitride-forming element and preferentially combines with nitrogen in the present invention to form high-temperature stable TiN particles. These fine TiN particles precipitate during the solidification and heating of molten steel, effectively pinning austenite grain boundaries and refining the grains. The titanium content is controlled at 0.01-0.05% to ensure the formation of a sufficient number of TiN particles while avoiding the formation of coarse inclusions that would impair toughness due to excessive titanium content. At the same time, an appropriate amount of titanium can protect some nitrogen from excessive consumption, retaining free nitrogen for subsequent austenite stabilization.

[0019] In some embodiments of the present invention, the mass percentage of V is any value or a range formed by any combination of 0.06%, 0.07%, 0.08%, 0.09%, and 0.1%. Vanadium is a key microalloying element in the present invention, and its role is manifested in two aspects: first, it forms nanoscale V(C,N) precipitates with carbon and nitrogen, producing a significant precipitation strengthening effect during tempering; second, partially dissolved vanadium can improve the stability of austenite. The vanadium content is limited to a microalloying range of 0.06-0.10%, contributing to the increase in strength without compromising toughness.

[0020] In some embodiments of the present invention, the mass percentage of Al is any value or a range formed by any combination of 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, and 0.055%. Aluminum is added as a strong deoxidizing element primarily to purify the molten steel and reduce its oxygen content. Simultaneously, aluminum and nitrogen can form AlN particles to help refine the grains. Controlling the aluminum content at 0.02-0.05% ensures sufficient deoxidation while avoiding the excessive formation of AlN that would consume too much nitrogen and affect the stabilizing effect of free nitrogen on austenite.

[0021] In some embodiments of this invention, the mass percentage of N is any value or a range formed by any combination of 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, and 0.08%. Nitrogen is a core element in the synergistic design with silicon and manganese in this invention. An appropriate amount of nitrogen in a solid solution state within austenite can significantly improve austenite stability and promote the formation of multi-scale retained austenite. Simultaneously, nitrogen forms carbonitrides with vanadium and titanium, contributing to precipitation strengthening. Controlling the nitrogen content to 0.03-0.08% ensures sufficient free nitrogen to stabilize austenite while avoiding excessive nitrogen leading to ingot porosity or the precipitation of coarse nitrides. This range matches the content of titanium, vanadium, and aluminum, ensuring effective nitrogen utilization.

[0022] In some embodiments of the present invention, the mass percentage of S is any value of 0%, 0.01%, 0.15%, 0.02%, or a range formed by any two of them.

[0023] In some embodiments of the present invention, the mass percentage of P is any value of 0%, 0.01%, 0.15%, 0.02%, or a range formed by any combination of both. Sulfur and phosphorus are both harmful impurity elements in steel and are controlled at a low level of ≤0.02%.

[0024] In some embodiments of the present invention, the medium alloy wear-resistant cast steel contains at least one selected from lower bainite, austenite, metal carbides, metal nitrides, and metal carbonitrides.

[0025] In some embodiments of the present invention, the average particle size of the metal carbide, metal nitride, and metal carbonitride is 100 nm-2 μm.

[0026] In some embodiments of the present invention, the average particle size of the metal carbide is 100 nm-2 μm; in some embodiments of the present invention, the average particle size of the metal carbide is any value or a range formed by any two of the following: 100 nm, 200 nm, 400 nm, 500 nm, 600 nm, 800 nm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm.

[0027] In some embodiments of the present invention, the average particle size of the metal nitride is 100 nm-2 μm; in some embodiments of the present invention, the average particle size of the metal nitride is any value or a range formed by any two of the following: 100 nm, 200 nm, 400 nm, 500 nm, 600 nm, 800 nm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm.

[0028] In some embodiments of the present invention, the average particle size of the metal carbonitride is 100 nm-2 μm; in some embodiments of the present invention, the average particle size of the metal carbonitride is any value or a range formed by any two of the following: 100 nm, 200 nm, 400 nm, 500 nm, 600 nm, 800 nm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm.

[0029] In some embodiments of the present invention, the metal nitride is selected from at least one of TiN and AlN.

[0030] In some embodiments of the present invention, the metal carbide is selected from at least one of VC and TiC.

[0031] In some embodiments of the present invention, the metal carbonitride includes at least one of vanadium carbonitride (denoted as V(C,N)) and titanium carbonitride (denoted as Ti(C,N)). In some embodiments of the present invention, the mass percentage of nitrogen element in the medium alloy wear-resistant cast steel is denoted as M. N The mass percentage of Ti element is denoted as M. Ti The mass percentage of element V is denoted as M. V The mass percentage of Al is denoted as M. Al Then M N M Ti M V and M Al Satisfy: M N ≥1.5×(0.292×M Ti +0.275×M V +0.519×M Al This formula is based on the dual requirements of nitride precipitation kinetics and free nitrogen stabilizing austenite in actual smelting. The nitrogen design of this invention ensures sufficient dissolved nitrogen to participate in austenite enrichment while avoiding porosity or coarse impurities caused by excessive nitrogen. The addition of titanium and vanadium achieves grain refinement and secondary hardening by pinning grain boundaries with TiN and dispersing V(C,N) precipitation, respectively, without relying on chromium and molybdenum, resulting in significant strengthening efficiency.

[0032] In some embodiments of the present invention, the Rockwell hardness of the medium alloy wear-resistant cast steel is ≥48 HRC; in some embodiments of the present invention, the Rockwell hardness of the medium alloy wear-resistant cast steel is 48-55 HRC; in some embodiments of the present invention, the Rockwell hardness of the medium alloy wear-resistant cast steel is 48-50 HRC.

[0033] In some embodiments of the present invention, the impact absorption energy of the medium alloy wear-resistant cast steel is ≥33J; in some embodiments of the present invention, the impact absorption energy of the medium alloy wear-resistant cast steel is 33-55J; in some embodiments of the present invention, the impact absorption energy of the medium alloy wear-resistant cast steel is 33-50J.

[0034] In some embodiments of the present invention, the tensile strength of the medium alloy wear-resistant cast steel is ≥1650MPa; in some embodiments of the present invention, the tensile strength of the medium alloy wear-resistant cast steel is 1650-1750MPa; in some embodiments of the present invention, the tensile strength of the medium alloy wear-resistant cast steel is 1662-1744MPa.

[0035] In some embodiments of the present invention, the relative wear resistance of the medium alloy wear-resistant cast steel is 1.4-1.7; in some embodiments of the present invention, the relative wear resistance of the medium alloy wear-resistant cast steel is 1.4-1.65.

[0036] The second aspect of the present invention provides a method for preparing the medium alloy wear-resistant cast steel described in the first aspect of the present invention, comprising the following steps: The raw materials used to prepare the medium alloy wear-resistant cast steel are melted to obtain molten steel; The molten steel is mixed with ferrotitanium particles and then cast to obtain a steel casting. The steel casting is subjected to solution quenching, critical zone carbon and nitrogen enrichment isothermal quenching heat treatment, and tempering heat treatment in sequence to obtain the medium alloy wear-resistant cast steel.

[0037] In this invention, the critical region refers to the austenite-ferrite two-phase region that exists during the heating and temperature rise of steel castings.

[0038] In some embodiments of the present invention, the raw materials used to prepare the medium alloy wear-resistant cast steel include scrap steel, manganese source, silicon source, chromium source, molybdenum source, nickel source, vanadium source, and nitrogen source.

[0039] In some embodiments of the present invention, the vanadium source includes ferrovanadium.

[0040] In some embodiments of the present invention, the nitrogen source includes ferrochromium nitride.

[0041] In some embodiments of the present invention, the vanadium source and nitrogen source need to be added 8-12 minutes before the smelting step is completed, and the electromagnetic stirring or mechanical stirring rate is increased after addition to promote uniform distribution of alloying elements.

[0042] In some embodiments of the present invention, the melting temperature is ≥1560°C.

[0043] In some embodiments of the present invention, the preparation method further includes the steps of deoxidizing and removing slag from pure aluminum; the steps of deoxidizing and removing slag from pure aluminum are located after the smelting step and before the step of mixing the molten steel with ferrotitanium particles.

[0044] In some embodiments of the present invention, the temperature of the molten steel before mixing with the ferrotitanium particles is ≥1600°C.

[0045] In some embodiments of the present invention, the step of mixing the molten steel with ferrotitanium particles involves pouring the molten steel into a ladle containing ferrotitanium particles, and then performing pure aluminum deoxidation, slag removal, and modification treatment in the ladle. The ferrotitanium particles in the ladle will directly contact and mix with the molten steel poured from the furnace, and will completely melt. The ferrotitanium particles mainly play a role in modification and grain refinement.

[0046] In some embodiments of the present invention, the particle size of the iron-titanium particles is ≤15mm, so as to fully exert the effects of alteration and grain refinement.

[0047] In some embodiments of the present invention, the temperature of the iron-titanium particles is ≥600°C, which facilitates the rapid melting of the iron-titanium particles after they come into contact with the molten steel and allows them to exert a metamorphic effect.

[0048] In some embodiments of the present invention, the casting temperature is 1500-1550°C.

[0049] In some embodiments of the present invention, the casting process is as follows: when the temperature of the molten steel is 1500~1550°C, the casting is carried out. After the casting is completed, the steel is slowly cooled in a sand mold to below 500°C, then the mold is opened and cleaned to obtain the cast steel part.

[0050] In some embodiments of the present invention, the smelting is carried out in a short-process medium-frequency electric furnace (i.e., a medium-frequency induction furnace). The preparation method of the present invention uses short-process medium-frequency induction furnace smelting, which eliminates the need for large-scale equipment such as converter refining, continuous casting, or forging and rolling, and allows the process to proceed directly from the casting stage to heat treatment, significantly reducing the production threshold and energy consumption per ton of steel.

[0051] In some embodiments of the present invention, the solution quenching temperature is 1120-1170℃; in some embodiments of the present invention, the solution quenching temperature is any value of 1120℃, 1130℃, 1140℃, 1150℃, 1160℃, 1170℃, or a range formed by any two of these values.

[0052] In some embodiments of the present invention, the heating rate of the solution quenching treatment is 100-120℃ / h; in some embodiments of the present invention, the heating rate of the solution quenching treatment is any value of 100℃ / h, 110℃ / h, 120℃ / h, or a range formed by any two of them.

[0053] In some embodiments of the present invention, the solution quenching treatment time is 3-6 hours.

[0054] In some embodiments of the present invention, the solution quenching process is as follows: the steel casting is first heated to 1120-1170°C for solution quenching, and then water-cooled to 20-40°C.

[0055] In some embodiments of the present invention, the solution quenching process is as follows: the steel casting is heated to 1120-1170°C at a heating rate of 100-120°C / h and held for 3-5 hours, and then cooled in water to 20-40°C after being taken out of the furnace.

[0056] In some embodiments of the present invention, the solution quenching process is as follows: first, the steel casting is heated to 630-670℃ and held for 2-3 hours, then heated to 1120-1170℃ and held for 1-3 hours, and then water-cooled to 20-40℃.

[0057] The present invention performs solution quenching at 1120-1170℃, which can completely eliminate as-cast segregation and allow elements such as vanadium and titanium to fully dissolve into the alloy matrix.

[0058] In some embodiments of the present invention, the steps of the critical zone carbon and nitrogen enrichment isothermal quenching heat treatment are as follows: first, the steel casting is heated to 760-800°C to enrich carbon and nitrogen, then isothermal quenching is performed in a salt bath, and then cooled in air to 20-40°C.

[0059] In some embodiments of the present invention, the carbon and nitrogen enrichment temperature is 760-800℃; in other embodiments, the carbon and nitrogen enrichment temperature is any value of 760℃, 770℃, 780℃, 790℃, or 800℃, or a range formed by any two of these values. The present invention utilizes the difference in solubility of carbon and nitrogen between ferrite and austenite by holding the temperature in the two-phase region of 760-800℃, thus "squeezing" interstitial atoms into austenite and forming a high concentration gradient. Since the solid solubility of carbon and nitrogen atoms in austenite is much higher than that in ferrite, carbon and nitrogen atoms diffuse from ferrite to austenite during the holding process and enrich in austenite, significantly increasing the carbon and nitrogen concentration in austenite. This results in a high concentration gradient of carbon and nitrogen in austenite, while the carbon and nitrogen concentration in ferrite drops to extremely low levels. This creates a significant concentration gradient on both sides of the phase interface, providing a compositional basis for obtaining highly stable retained austenite through subsequent isothermal quenching.

[0060] In some embodiments of the present invention, the heat preservation time for carbon and nitrogen enrichment is 2-3 hours.

[0061] In some embodiments of the present invention, the heating rate of the carbon and nitrogen enrichment is ≤100℃ / h; in some embodiments of the present invention, the heating rate of the carbon and nitrogen enrichment is any value or a range formed by any two of 10℃ / h, 20℃ / h, 30℃ / h, 40℃ / h, 50℃ / h, 60℃ / h, 70℃ / h, 80℃ / h, 90℃ / h, and 100℃ / h.

[0062] In some embodiments of the present invention, the carbon and nitrogen enrichment involves heating the solution-quenched cast steel part to 760-800℃ at a heating rate of ≤100℃ / h and holding it at that temperature for 2-3 hours. Carbon and nitrogen enrichment is primarily performed in the critical region to create a carbon and nitrogen concentration gradient between ferrite and austenite. The high carbon content gives austenite higher stability, allowing it to maintain its austenitic structure during subsequent isothermal quenching, ultimately forming a bainite + austenite matrix. The presence of austenite imparts high toughness and work hardening ability under wear, thereby improving the wear resistance of medium alloy cast steel.

[0063] In some embodiments of the present invention, the tempering heat treatment temperature is 200-250°C; in some embodiments of the present invention, the tempering heat treatment temperature is any value of 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, or a range formed by any two of them.

[0064] In some embodiments of the present invention, the tempering heat treatment time is 2-3 hours.

[0065] In some embodiments of the present invention, the heating rate of the tempering heat treatment is ≤100℃ / h; in some embodiments of the present invention, the heating rate of the tempering heat treatment is any value or a range formed by any two of 10℃ / h, 20℃ / h, 30℃ / h, 40℃ / h, 50℃ / h, 60℃ / h, 70℃ / h, 80℃ / h, 90℃ / h, and 100℃ / h.

[0066] In some embodiments of the present invention, the tempering heat treatment step is as follows: the steel casting that has undergone the critical zone carbon and nitrogen enrichment isothermal quenching heat treatment is heated to 200-250°C for tempering heat treatment, and then cooled in air to 20-40°C.

[0067] In some embodiments of the present invention, the tempering heat treatment step is as follows: the steel casting that has undergone the critical zone carbon and nitrogen enrichment isothermal quenching heat treatment is heated to 200-250°C at a heating rate of ≤100°C / h for tempering heat treatment, the holding time of the tempering heat treatment is 2-3 hours, and then it is taken out and cooled in air to 20-40°C.

[0068] In some embodiments of the present invention, the temperature of the isothermal quenching in the salt bath is 280-320°C; in some embodiments of the present invention, the temperature of the isothermal quenching in the salt bath is any value of 280°C, 290°C, 300°C, 310°C, 320°C, or a range formed by any two of them.

[0069] In some embodiments of the present invention, the isothermal time for salt bath isothermal quenching is 2-4 hours.

[0070] This invention obtains a multiphase microstructure of lower bainite and carbon-nitrogen-rich retained austenite through isothermal quenching in a salt bath at 280-320℃. Combined with a tempering heat treatment step, this achieves secondary precipitation of vanadium-containing carbides and other substances, thereby further strengthening the alloy.

[0071] A third aspect of the present invention provides a wear-resistant component for mechanical equipment, comprising a component made of medium-alloy wear-resistant cast steel as described in the first aspect of the present invention.

[0072] In some embodiments of the present invention, the mechanical equipment is selected from mechanical equipment used for mining crushing, mechanical equipment used for building material crushing, mechanical equipment used for metallurgy, and mechanical equipment used for marine industry.

[0073] The beneficial effects of this invention are as follows: By optimizing the chemical composition of the alloy, the medium alloy wear-resistant cast steel of this invention produces an alloy with high Rockwell hardness, high room temperature impact energy, excellent tensile strength, and wear resistance. Specifically, the Rockwell hardness is ≥48 HRC, the room temperature impact energy (V-notch) is ≥33 J, and the tensile strength is ≥1650 MPa. It can be used in wear-resistant parts of machinery and equipment used in mining, construction, cement, metallurgy, and marine industries, thereby improving the mechanical properties, wear resistance, and service life of the machinery and equipment. Attached Figure Description

[0074] Figure 1 The image shows the metallographic microstructure of the medium alloy wear-resistant cast steel in Example 1. Detailed Implementation

[0075] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0076] Example 1 This embodiment provides a medium alloy wear-resistant cast steel with the following chemical composition by mass percentage: C: 0.33%, Si: 2.25%, Mn: 2.50%, Cr: 0.2%, Mo: 0.2%, Ni: 0.1%, V: 0.08%, Ti: 0.03%, Al: 0.03%, N: 0.05%, S≤0.02%, P≤0.02%, unavoidable impurities≤0.2%, and the balance being iron.

[0077] The medium-alloy wear-resistant cast steel in this example is prepared using a method that includes the following steps: (1) Raw materials such as scrap steel, manganese source, silicon source, chromium source, molybdenum source, nickel source, vanadium source, and nitrogen source are put into the medium frequency induction furnace for smelting according to the proportion. Among them, vanadium source and nitrogen source are ferrovanadium and ferrochrome nitride, and are added 10 minutes before the completion of the smelting step. After adding, electromagnetic stirring or manual stirring should be strengthened. The smelting temperature is controlled at 1570℃ until the raw materials are completely melted. Then, pure aluminum deoxidation (pure aluminum deoxidizer is added for treatment, at 0.10% of the total weight of the steel liquid) and slag removal treatment are carried out. After adjusting the composition of the steel liquid and making it qualified, the temperature of the steel liquid is adjusted to 1600℃. (2) Place titanium iron particles with a size of less than 15 mm that have been baked at 700℃ at the bottom of the ladle in advance, pour the molten steel obtained in step (1) into the ladle, and continue to carry out pure aluminum deoxidation, slag removal and deterioration treatment in the ladle. (3) When the temperature of the molten steel drops to 1540℃, it is poured. After pouring, it is slowly cooled in the sand mold to below 500℃, then the mold is opened and cleaned to obtain the cast steel parts.

[0078] (4) The obtained cast steel parts are subjected to solution quenching, critical zone carbon and nitrogen enrichment isothermal quenching heat treatment and tempering heat treatment in sequence. Solution quenching treatment: The obtained cast steel parts are heated to 650°C in a heat treatment furnace at a rate of 110°C / h, held for 3 hours, and then heated to 1150°C and held for 4 hours before being taken out of the furnace and cooled in water to room temperature. Critical zone carbon and nitrogen enrichment isothermal quenching heat treatment: The cast steel part is heated to 780℃ at a heating rate of 80℃ / h and held for 2h; after the holding period, the cast steel part is quickly transferred to a salt bath furnace preheated to 300℃ and isothermally held at this temperature for 3 hours. After the isothermally holding period, the cast steel part is taken out and air-cooled to room temperature. Tempering heat treatment: The quenched cast steel parts are heated to 250℃ at a heating rate of 80℃ / h, held at that temperature for 2 hours, and then taken out and air-cooled to room temperature.

[0079] Example 2 This embodiment provides a medium alloy wear-resistant cast steel with the following chemical composition by mass percentage: C: 0.30%, Si: 2.55%, Mn: 3.50%, Cr: 0.3%, Mo: 0.15%, Ni: 0.15%, V: 0.1%, Ti: 0.05%, Al: 0.05%, N: 0.08%, S≤0.02%, P≤0.02%, unavoidable impurities≤0.2%, and the balance being iron.

[0080] The medium alloy wear-resistant cast steel in this embodiment is prepared by a method including the following steps: (1) Raw materials such as scrap steel, manganese source, silicon source, chromium source, molybdenum source, nickel source, vanadium source, and nitrogen source are put into the medium frequency induction furnace for smelting according to the proportion. Among them, vanadium source and nitrogen source are ferrovanadium and ferrochrome nitride. They are added 10 minutes before the smelting step is completed. After adding them, electromagnetic stirring or manual stirring should be strengthened. The smelting temperature is controlled at 1580℃ until the raw materials are completely melted and pure aluminum deoxidation (pure aluminum deoxidizer is added for treatment, at 0.10% of the total weight of the steel liquid) and slag removal treatment are carried out. After adjusting the composition of the steel liquid and making it qualified, the temperature of the steel liquid is adjusted to 1620℃. (2) Place pre-baked ferro-titanium particles with a size of less than 15 mm at the bottom of the ladle, pour the molten steel obtained in step (1) into the ladle, and continue to carry out pure aluminum deoxidation, slag removal and deterioration treatment in the ladle. (3) When the temperature of the molten steel drops to 1530℃, pour it. After pouring, cool it slowly in the sand mold to below 500℃, then open the mold and clean it to obtain the cast steel parts.

[0081] (4) The obtained cast steel parts are subjected to solution quenching, critical zone carbon and nitrogen enrichment isothermal quenching heat treatment and tempering heat treatment in sequence. Solution quenching treatment: The obtained cast steel parts are heated to 650°C in a heat treatment furnace at a rate of 120°C / h, held for 3 hours, and then heated to 1170°C and held for 5 hours before being taken out of the furnace and cooled to room temperature in water. Critical zone carbon and nitrogen enrichment isothermal quenching heat treatment: The cast steel part is heated to 800℃ at a heating rate of 80℃ / h and held for 3h; after the holding period, the cast steel part is quickly transferred to a salt bath furnace preheated to 320℃ and isothermally held at this temperature for 4 hours. After the isothermally holding period, the cast steel part is taken out and air-cooled to room temperature. Tempering heat treatment: The quenched cast steel parts are heated to 220℃ at a heating rate of 80℃ / h, held at that temperature for 3 hours, and then taken out and air-cooled to room temperature.

[0082] Example 3 This embodiment provides a medium alloy wear-resistant cast steel with the following chemical composition by mass percentage: C: 0.27%, Si: 2.45%, Mn: 2.25%, Cr: 0.1%, Mo: 0.1%, Ni: 0.2%, V: 0.06%, Ti: 0.02%, Al: 0.04%, N: 0.06%, S≤0.02%, P≤0.02%, unavoidable impurities≤0.2%, and the balance being iron.

[0083] The medium alloy wear-resistant cast steel in this embodiment is prepared by a method including the following steps: (1) Raw materials such as scrap steel, manganese source, silicon source, chromium source, molybdenum source, nickel source, vanadium source, and nitrogen source are put into the medium frequency induction furnace for smelting according to the proportion. Among them, vanadium source and nitrogen source are ferrovanadium and ferrochrome nitride. They are added 10 minutes before the smelting step is completed. After adding them, electromagnetic stirring or manual stirring should be strengthened. The smelting temperature is controlled at 1570℃ until the raw materials are completely melted and pure aluminum deoxidation (pure aluminum deoxidizer is added for treatment, at 0.10% of the total weight of the steel liquid) and slag removal treatment are carried out. After adjusting the composition of the steel liquid and making it qualified, the temperature of the steel liquid is adjusted to 1600℃. (2) Place pre-baked ferro-titanium particles with a size of less than 15 mm at the bottom of the ladle, pour the molten steel obtained in step (1) into the ladle, and continue to carry out pure aluminum deoxidation, slag removal and deterioration treatment in the ladle. (3) When the temperature of the molten steel drops to 1520℃, pour it. After pouring, cool it slowly in the sand mold to below 500℃, then open the mold and clean it to obtain the cast steel parts.

[0084] (4) The obtained cast steel parts are subjected to solution quenching, critical zone carbon and nitrogen enrichment isothermal quenching heat treatment and tempering heat treatment in sequence. Solution quenching treatment: The obtained cast steel parts are heated to 650°C in a heat treatment furnace at a rate of 100°C / h, held for 3 hours, and then heated to 1140°C and held for 5 hours before being taken out of the furnace and cooled to room temperature in water. Critical zone carbon and nitrogen enrichment isothermal quenching heat treatment: The cast steel part is heated to 800℃ at a heating rate of 80℃ / h and held for 3h; after the holding period, the cast steel part is quickly transferred to a salt bath furnace preheated to 320℃ and isothermally held at this temperature for 4 hours. After the isothermally holding period, the cast steel part is taken out and air-cooled to room temperature. Tempering heat treatment: The quenched cast steel parts are heated to 220℃ at a heating rate of 80℃ / h, held at that temperature for 3 hours, and then taken out and air-cooled to room temperature.

[0085] Example 4 This embodiment provides a medium alloy wear-resistant cast steel with the following chemical composition by mass percentage: C: 0.34%, Si: 2.4%, Mn: 2.00%, Cr: 0.3%, Mo: 0.3%, V: 0.06%, Ti: 0.01%, Al: 0.02%, N: 0.03%, S≤0.02%, P≤0.02%, unavoidable impurities≤0.2%, and the balance being iron.

[0086] The medium alloy wear-resistant cast steel in this embodiment is prepared by a method including the following steps: (1) Raw materials such as scrap steel, manganese source, silicon source, chromium source, molybdenum source, nickel source, vanadium source, and nitrogen source are put into the medium frequency induction furnace for smelting according to the proportion. Among them, vanadium source and nitrogen source are ferrovanadium and ferrochrome nitride. They are added 10 minutes before the smelting step is completed. After adding them, electromagnetic stirring or manual stirring should be strengthened. The smelting temperature is controlled at 1570℃ until the raw materials are completely melted and pure aluminum deoxidation and slag removal are carried out. After adjusting the composition of the molten steel and making it qualified, the temperature of the molten steel is adjusted to 1600℃. (2) Place pre-baked ferro-titanium particles with a size of less than 15 mm at the bottom of the ladle, pour the molten steel obtained in step (1) into the ladle, and continue to carry out pure aluminum deoxidation, slag removal and deterioration treatment in the ladle. (3) When the temperature of the molten steel drops to 1530℃, pour it. After pouring, cool it slowly in the sand mold to below 500℃, then open the mold and clean it to obtain the cast steel parts.

[0087] (4) The obtained cast steel parts are subjected to solution quenching, critical zone carbon and nitrogen enrichment isothermal quenching heat treatment and tempering heat treatment in sequence. The solution quenching process involves heating the resulting cast steel parts in a heat treatment furnace at a rate of 110℃ / h to 650℃, holding them at that temperature for 2 hours, then continuing to heat them to 1120℃, holding them at that temperature for 3 hours, and finally removing them from the furnace and cooling them in water to room temperature. Critical zone carbon and nitrogen enrichment isothermal quenching heat treatment: The cast steel part is heated to 770℃ at a heating rate of 80℃ / h and held for 2h; after the holding period, the cast steel part is quickly transferred to a salt bath furnace preheated to 300℃ and isothermally held at this temperature for 3 hours. After the isothermally holding period, the cast steel part is taken out and air-cooled to room temperature. Tempering heat treatment: The quenched cast steel parts are heated to 210℃ at a heating rate of 80℃ / h, held at that temperature for 2 hours, and then taken out and air-cooled to room temperature.

[0088] Comparative Example 1 The specific composition of the medium-alloy wear-resistant cast steel in this comparative example is ZGM30Mn2SiCr steel as specified in GB / T 26651-2025 Wear-resistant Steel Castings, specifically: C: 0.33%, Si: 1.2%, Mn: 2.2%, Cr: 0.8%, Mo: 0.2%, Ni: 0.2%, S≤0.04%, P≤0.04%, unavoidable impurities≤0.2%, and the balance being iron. Its smelting, casting, and heat treatment adopt the general methods recommended by national standards, and the specific steps are as follows: (1) Raw materials such as scrap steel, manganese source, silicon source, manganese source, chromium source, molybdenum source, and nickel source are put into the medium frequency induction furnace for smelting in proportion. The smelting temperature is controlled at 1570℃ until the raw materials are completely melted and pure aluminum deoxidation (pure aluminum deoxidizer is added for treatment, at 0.10% of the total weight of the molten steel) and slag removal treatment are carried out. After adjusting the composition of the molten steel and making it qualified, the temperature of the molten steel is adjusted to 1600℃. (2) Pour the molten steel obtained in step (1) into a ladle and continue the pure aluminum deoxidation and slag removal process in the ladle; (3) When the temperature of the molten steel drops to 1530℃, pour it. After pouring, cool it slowly in the sand mold to below 500℃, then open the mold and clean it to obtain the cast steel parts.

[0089] (4) The obtained cast steel parts are heated to 650°C in a heat treatment furnace at a rate of 110°C / h, held for 2 hours, and then heated to 920°C and held for 3 hours before being taken out of the furnace and cooled in water to room temperature; the quenched cast steel parts are heated to 210°C at a rate of 80°C / h, held for 2 hours, and then taken out and air-cooled to room temperature.

[0090] Comparative Example 2 This comparative example provides an alloy wear-resistant cast steel with the following chemical composition by mass percentage: C: 0.33%, Si: 2.25%, Mn: 2.50%, Cr: 0.2%, Mo: 0.2%, Ni: 0.1%, V: 0.08%, Ti: 0.03%, Al: 0.03%, S≤0.02%, P≤0.02%, unavoidable impurities≤0.2%, and the balance being iron.

[0091] Compared to Example 1, this comparative example did not add N.

[0092] The alloy wear-resistant cast steel in this example was prepared using the preparation method described in Example 1.

[0093] Comparative Example 3 This comparative example provides an alloy wear-resistant cast steel with the following chemical composition by mass percentage: C: 0.33%, Si: 2.25%, Mn: 2.50%, Cr: 0.2%, Mo: 0.2%, Ni: 0.1%, V: 0.08%, Ti: 0.03%, Al: 0.03%, N: 0.1%, S≤0.02%, P≤0.02%, unavoidable impurities≤0.2%, and the balance being iron.

[0094] Compared with Example 1, the amount of N added in this comparative example is 0.1%.

[0095] The alloy wear-resistant cast steel in this example was prepared using the preparation method described in Example 1.

[0096] Comparative Example 4 This example provides a medium alloy wear-resistant cast steel with the following chemical composition by mass percentage: C: 0.33%, Si: 1.8%, Mn: 2.50%, Cr: 0.2%, Mo: 0.2%, Ni: 0.1%, V: 0.08%, Ti: 0.03%, Al: 0.03%, N: 0.05%, S≤0.02%, P≤0.02%, unavoidable impurities≤0.2%, and the balance being iron.

[0097] Compared to Example 1, this comparative example has a lower silicon content, making it difficult to support sufficient lower bainite formation.

[0098] The alloy wear-resistant cast steel in this example was prepared using the preparation method described in Example 1.

[0099] Comparative Example 5 This example provides a medium alloy wear-resistant cast steel with the following chemical composition by mass percentage: C: 0.33%, Si: 2.25%, Mn: 1.50%, Cr: 0.2%, Mo: 0.2%, Ni: 0.1%, V: 0.08%, Ti: 0.03%, Al: 0.03%, N: 0.05%, S≤0.02%, P≤0.02%, unavoidable impurities≤0.2%, and the balance being iron.

[0100] Compared to Example 1, this comparative example has a lower manganese content, making it difficult to support sufficient hardening.

[0101] The alloy wear-resistant cast steel in this example was prepared using the preparation method described in Example 1.

[0102] Comparative Example 6 This example provides a medium alloy wear-resistant cast steel with the following chemical composition by mass percentage: C: 0.33%, Si: 2.25%, Mn: 2.50%, Cr: 0.2%, Mo: 0.2%, Ni: 0.1%, V: 0.08%, Al: 0.03%, N: 0.05%, S≤0.02%, P≤0.02%, unavoidable impurities≤0.2%, and the balance being iron.

[0103] Compared to Example 1, no titanium was added to this comparative example.

[0104] The only difference between the preparation method of the alloy wear-resistant cast steel in this example and that in Example 1 is that titanium iron particles were not placed in the ladle in step (2) of this example.

[0105] Comparative Example 7 This comparative example provides an alloy wear-resistant cast steel with the following chemical composition by mass percentage: C: 0.33%, Si: 2.25%, Mn: 2.50%, Cr: 0.2%, Mo: 0.2%, Ni: 0.1%, Al: 0.03%, S≤0.02%, P≤0.02%, unavoidable impurities≤0.2%, and the balance being iron.

[0106] Compared to Example 1, this comparative example did not contain V, Ti, and N.

[0107] The alloy wear-resistant cast steel in this example was prepared using the preparation method described in Example 1.

[0108] Comparative Example 8 The chemical composition of the medium alloy wear-resistant cast steel in this comparative example is the same as that in Example 1.

[0109] The difference between the preparation method of the medium alloy wear-resistant cast steel in this comparative example and that in Example 1 is only that: in this example, step (4) is as follows: the steel casting is heated to 650°C in a heat treatment furnace at a rate of 110°C / h, held for 3 hours, and then heated to 1150°C and held for 4 hours before being taken out of the furnace and cooled to room temperature in water; then the cast steel is heated to 940°C at a rate of 80°C / h and held for 2 hours; after the holding is completed, it is quenched in water and cooled to room temperature; the quenched cast steel is heated to 250°C at a rate of 80°C / h and held for 2 hours, and then taken out and air-cooled to room temperature.

[0110] Compared with Example 1, this comparative example uses a conventional solution quenching and tempering process.

[0111] Performance testing The metallographic microstructure of the medium alloy wear-resistant cast steel in Example 1 was examined using a metallographic microscope, as shown in the following figure. Figure 1 As shown. By Figure 1 It can be seen that the medium alloy wear-resistant cast steel matrix in Example 1 is composed of bainite and a small amount of bright blocky retained austenite. The overall structure is fine, and fine precipitates can be seen in some areas.

[0112] The mechanical properties of Examples 1-4 and Comparative Examples 1-8 were tested according to the following standards, and the test results are shown in Table 1. The tensile test was conducted according to GB / T 228.1-2021 Metallic Materials Tensile Testing; the Rockwell hardness test was conducted according to GB / T230.1-2018 Metallic Materials Rockwell Hardness Test; the impact toughness test was conducted according to GB / T 229-2020 Metallic Materials Charpy Pendulum Impact Test Method, and the specimen was a V-notch specimen; the wear test was conducted according to T / CFA 010604-3-2016 Steel Materials Impact Abrasive Wear Test Method.

[0113] Table 1 Performance Test Results

[0114] As shown in Table 1, compared with Comparative Examples 1-8, the comprehensive mechanical properties and wear resistance of Examples 1-4 are superior to those of the Comparative Examples. Comparative Examples 1, 3, 4, and 8 have low impact absorption energy, are prone to cracking, and thus suffer severe damage during wear, accelerating failure. Comparative Examples 2, 4, 5, 6, and 7 have low Rockwell hardness, making them easily damaged by abrasives during abrasive wear, accelerating failure.

[0115] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A medium-alloy wear-resistant cast steel, characterized in that: The medium alloy wear-resistant cast steel is composed of the following elements by mass percentage: C 0.27-0.34%, Si 2.25-2.55%, Mn 2.00-3.50%, Cr 0.1-0.3%, precious metals ≤0.3%, Ti 0.01-0.05%, V 0.06-0.10%, Al 0.02-0.05%, N 0.03-0.08%, S ≤0.02%, P ≤0.02%, unavoidable impurities ≤0.2%, and the balance being Fe; The precious metal is selected from at least one of Mo and Ni; The medium alloy wear-resistant cast steel is prepared by a method including the following steps: The raw materials used to prepare the medium alloy wear-resistant cast steel are melted to obtain molten steel; The molten steel is mixed with ferrotitanium particles and then cast to obtain a steel casting. The steel casting is subjected to solution quenching, critical zone carbon and nitrogen enrichment isothermal quenching heat treatment, and tempering heat treatment in sequence to obtain the medium alloy wear-resistant cast steel. The steps of the critical zone carbon and nitrogen enrichment isothermal quenching heat treatment are as follows: first, heat the steel casting to 760-800℃ to enrich carbon and nitrogen, then perform salt bath isothermal quenching, and then cool it in air to 20-40℃. The tempering heat treatment steps are as follows: the steel casting that has undergone the critical zone carbon and nitrogen enrichment isothermal quenching heat treatment is heated to 200-250℃ for tempering heat treatment, and then cooled in air to 20-40℃.

2. The medium-alloy wear-resistant cast steel according to claim 1, characterized in that: The medium alloy wear-resistant cast steel contains at least one selected from lower bainite, austenite, metal carbides, metal nitrides, and metal carbonitrides.

3. The medium-alloy wear-resistant cast steel according to claim 2, characterized in that: The metal nitride includes at least one of TiN and AlN; And / or, the metal carbide includes at least one of VC and TiC; And / or, the metal carbonitride includes at least one of V carbonitride and Ti carbonitride.

4. The medium-alloy wear-resistant cast steel according to claim 1, characterized in that: In the aforementioned medium alloy wear-resistant cast steel, the mass percentage of nitrogen element is denoted as M. N The mass percentage of Ti element is denoted as M. Ti The mass percentage of element V is denoted as M. V The mass percentage of Al is denoted as M. Al Then M N M Ti M V and M Al Satisfy: M N ≥1.5×(0.292×M Ti +0.275×M V +0.519×M Al ).

5. The medium-alloy wear-resistant cast steel according to any one of claims 1-4, characterized in that: The medium alloy wear-resistant cast steel has at least one of the following characteristics: (a1) The Rockwell hardness of the medium alloy wear-resistant cast steel is ≥48HRC; (a2) The impact absorption energy of the medium alloy wear-resistant cast steel is ≥33J; (a3) The tensile strength of the medium alloy wear-resistant cast steel is ≥1650MPa; (a4) The relative wear resistance of the medium alloy wear-resistant cast steel is 1.4-1.

7.

6. The method for preparing medium alloy wear-resistant cast steel according to any one of claims 1-5, characterized in that: Includes the following steps: The raw materials used to prepare the medium alloy wear-resistant cast steel are melted to obtain molten steel; The molten steel is mixed with ferrotitanium particles and then cast to obtain a steel casting. The steel casting is subjected to solution quenching, critical zone carbon and nitrogen enrichment isothermal quenching heat treatment, and tempering heat treatment in sequence to obtain the medium alloy wear-resistant cast steel. The steps of the critical zone carbon and nitrogen enrichment isothermal quenching heat treatment are as follows: first, heat the steel casting to 760-800℃ to enrich carbon and nitrogen, then perform salt bath isothermal quenching, and then cool it in air to 20-40℃. The tempering heat treatment steps are as follows: the steel casting that has undergone the critical zone carbon and nitrogen enrichment isothermal quenching heat treatment is heated to 200-250℃ for tempering heat treatment, and then cooled in air to 20-40℃.

7. The method for preparing medium-alloy wear-resistant cast steel according to claim 6, characterized in that: The solution quenching treatment has at least one of the following characteristics: (b1) The solution quenching temperature is 1120-1170℃; (b2) The heating rate of the solution quenching treatment is 100-120℃ / h; (b3) The heat treatment time for the solution quenching is 3-6 hours; (b4) The solution quenching process is as follows: first, the steel casting is heated to 1120-1170℃ for solution quenching, and then water-cooled to 20-40℃; or, the steel casting is heated to 630-670℃ for heat preservation, and then heated to 1120-1170℃ for solution quenching, and then water-cooled to 20-40℃.

8. The method for preparing medium-alloy wear-resistant cast steel according to claim 6, characterized in that: The heat preservation time for carbon and nitrogen enrichment is 2-3 hours.

9. The method for preparing medium-alloy wear-resistant cast steel according to claim 6, characterized in that: The heating rate for carbon and nitrogen enrichment is ≤100℃ / h.

10. The method for preparing medium-alloy wear-resistant cast steel according to claim 6, characterized in that: The temperature for isothermal quenching in the salt bath is 280-320℃.

11. The method for preparing medium-alloy wear-resistant cast steel according to claim 6, characterized in that: The isothermal quenching time in the salt bath isothermal quenching is 2-4 hours.

12. The method for preparing medium-alloy wear-resistant cast steel according to claim 6, characterized in that: The tempering heat treatment time is 2-3 hours; And / or, the heating rate of the tempering heat treatment is ≤100℃ / h.

13. A wear-resistant component for mechanical equipment, characterized in that: Includes components made of medium alloy wear-resistant cast steel as described in any one of claims 1-5.

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