Nm450 grade wear-resistant steel and production method thereof

Abstract

This application belongs to the field of steel materials technology, specifically to an NM450 grade wear-resistant steel and its production method. The NM450 grade wear-resistant steel has a Brinell hardness of 435HBW-460HBW. The NM450 grade wear-resistant steel comprises the following components by weight percentage: C: 0.19%-0.22%, Si: 0.35%-0.55%, Mn: 1.25%-1.40%, P≤0.012%, S≤0.003%, Cr: 0.30%-0.75%, Nb: 0.010%-0.020%, Ti: 0.012%-0.022%, B: 0.0012%-0.0023%, As≤0.007%, Als: 0.025%-0.050%, N≤0.0050%, with the remainder being Fe and impurities.

Description

Technical Field

[0001] This application relates to the field of steel materials technology, specifically to an NM450 grade wear-resistant steel and its production method. Background Technology

[0002] The demand for wear-resistant steel in the construction machinery industry is growing. Wear-resistant steel not only needs to have high hardness and excellent wear resistance, but also needs to have good machinability and toughness to meet the long-term stable use requirements under complex working conditions.

[0003] While NM450 wear-resistant steel is currently a mainstream product in the market, it still has significant shortcomings in actual production and application. On the one hand, the composition design of NM450 wear-resistant steel does not include differentiated alloy ratio optimization for different thicknesses. When the thickness of NM450 wear-resistant steel exceeds 20mm, the hardness uniformity is poor, with hardness fluctuations reaching ±40HBW across all thicknesses. On the other hand, the rolling and heat treatment process parameters are not designed for variations in the thickness of NM450 wear-resistant steel, easily leading to internal defects such as microstructure segregation and excessive hardness. This results in unstable wear resistance, making it difficult to meet the requirements of high-end engineering machinery. Summary of the Invention

[0004] This application provides an NM450 grade wear-resistant steel and its production method. By controlling the weight percentage of each component in the NM450 grade wear-resistant steel, a Brinell hardness of 435HBW-460HBW with a hardness fluctuation of ≤25HBW is achieved across the entire thickness specification, thus solving the problems of large hardness fluctuation and unstable wear resistance of NM450 grade wear-resistant steel.

[0005] In a first aspect, embodiments of this application provide an NM450 grade wear-resistant steel, wherein the NM450 grade wear-resistant steel has a Brinell hardness of 435HBW-460HBW and comprises the following components in weight percentage: C: 0.19%-0.22%, Si: 0.35%-0.55%, Mn: 1.25%-1.40%, P≤0.012%, S≤0.003%, Cr: 0.30%-0.75%, Nb: 0.010%-0.020%, Ti: 0.012%-0.022%, B: 0.0012%-0.0023%, As≤0.007%, Als: 0.025%-0.050%, N≤0.0050%, with the remainder being Fe and impurities.

[0006] In one possible implementation, the NM450 grade wear-resistant steel contains Si: 0.35%-0.45%, Mn: 1.30%-1.40%, Cr: 0.30%-0.40%, and B: 0.0012%-0.0022%, and the thickness of the NM450 grade wear-resistant steel is L1, where L1 satisfies: 10mm≤L1≤20mm.

[0007] In one possible implementation, the NM450 grade wear-resistant steel contains Si: 0.45%-0.55%, Mn: 1.25%-1.35%, Cr: 0.60%-0.75%, and B: 0.0013%-0.0023%, and the thickness of the NM450 grade wear-resistant steel is L2, where L2 satisfies: 20mm < L2 ≤ 50mm.

[0008] In one possible implementation, the Brinell hardness fluctuation of the NM450 grade wear-resistant steel is ≤25HBW.

[0009] Secondly, embodiments of this application provide a method for producing NM450 grade wear-resistant steel. The method includes: mixing and smelting the components of NM450 grade wear-resistant steel to a target thickness to obtain a billet; subjecting the billet to slow cooling, heating treatment, and descaling treatment in sequence; subjecting the descaled billet to two-stage rolling to obtain a steel plate conforming to the target thickness, wherein the preset rolling temperature of the first rolling stage is higher than the preset rolling temperature of the second rolling stage; and subjecting the rolled steel plate to cooling and heat treatment to obtain the NM450 grade wear-resistant steel.

[0010] In one possible implementation, the process of mixing and smelting the components of the NM450 grade wear-resistant steel to produce the target thickness includes: preparing the components of the NM450 grade wear-resistant steel according to the target thickness; subjecting the mixed components of the NM450 grade wear-resistant steel to vacuum circulation degassing to obtain a first molten steel, wherein the vacuum holding time of the vacuum circulation degassing is T1, and T1 satisfies: T1≥15min; and subjecting the first molten steel to continuous casting to obtain the billet, wherein the continuous casting superheat temperature of the continuous casting is 10℃-25℃.

[0011] In one possible implementation, the two-stage rolling of the dephosphorized billet includes: in the first rolling stage, the dephosphorized billet is rolled at a preset rolling temperature, and the reduction rate of the last pass is controlled to be ≥20% to obtain a billet of the target thickness; in the second rolling stage, a second preset starting rolling temperature and a second preset finishing rolling temperature are controlled according to the target thickness of the NM450 grade wear-resistant steel, and the cumulative reduction rate of the last three passes is controlled to be ≥25%.

[0012] In one possible implementation, the preset rolling temperature is ≥1080℃; when the target thickness of the NM450 grade wear-resistant steel is L1, the second preset initial rolling temperature is ≤920℃, and the second preset final rolling temperature is 840℃-880℃; when the target thickness of the NM450 grade wear-resistant steel is L2, the second preset initial rolling temperature is ≤900℃, and the second preset final rolling temperature is 820℃-860℃.

[0013] In one possible implementation, the heat treatment of the rolled billet includes: heating the rolled steel plate to a preset quenching temperature and maintaining it for a preset quenching time, wherein the preset quenching time is controlled according to the target thickness of the NM450 grade wear-resistant steel; and heating the quenched steel plate to a preset tempering temperature and maintaining it for a preset tempering time.

[0014] In one possible implementation, the preset quenching time is controlled according to the target thickness of the NM450 grade wear-resistant steel, including: when the target thickness of the NM450 grade wear-resistant steel is L1, the preset quenching time of the steel plate is L1+T2, where T2 satisfies: 20min≤T2≤30min; when the target thickness of the NM450 grade wear-resistant steel is L2, the preset quenching time of the steel plate is 1.5×L2+T3, where T3 satisfies: 25min≤T3≤35min.

[0015] The precise control of the weight percentage of each component in the NM450 grade wear-resistant steel provided in this application embodiment enables the NM450 grade wear-resistant steel to have good hardness consistency, thereby ensuring stable hardness and wear resistance of the NM450 grade wear-resistant steel across the entire thickness specification. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is one of the schematic diagrams of the production process of NM450 grade wear-resistant steel provided in the embodiments of this application;

[0018] Figure 2 This is the second schematic diagram of the production process of NM450 grade wear-resistant steel provided in the embodiments of this application;

[0019] Figure 3 The third schematic diagram of the production process of NM450 grade wear-resistant steel provided in the embodiments of this application;

[0020] Figure 4 Fourth schematic diagram of the production process of NM450 grade wear-resistant steel provided for the embodiments of this application;

[0021] Figure 5 A metallographic diagram of a quarter-thickness NM450 grade wear-resistant steel provided for an embodiment of this application;

[0022] Figure 6 A metallographic diagram showing half the thickness of NM450 grade wear-resistant steel provided in an embodiment of this application. Detailed Implementation

[0023] The embodiments of this application are described in detail below, examples of which are illustrated in the accompanying drawings. In the drawings, for clarity, the dimensions of layers, regions, and elements, as well as their relative dimensions, may be exaggerated. Throughout, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0024] It should be noted that the terms "first," "second," etc., used in this application's specification are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0025] In this application, the term "numerical interval" (i.e., numerical range) refers to a range of values. Unless otherwise specified, the distribution of selectable values ​​within this numerical interval is considered continuous, and includes the two endpoints (i.e., the minimum and maximum values) of the interval, as well as every value between these endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoints of the range and every integer between them, effectively listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in this numerical interval can be any quantitative value, such as a number, percentage, or proportion. The term "numerical interval" can broadly include percentage intervals, proportion intervals, ratio intervals, and other quantitative intervals.

[0026] NM450 grade wear-resistant steel is the most widely used mainstream product on the market, but it still has many obvious defects in actual production and application, making it difficult to meet the requirements of high-end engineering machinery.

[0027] On the one hand, the composition design of NM450 grade wear-resistant steel did not adjust the alloy ratio according to the thickness specifications of NM450 grade wear-resistant steel, resulting in extremely poor hardness uniformity of NM450 grade wear-resistant steel with a thickness >20mm. The hardness fluctuation range of NM450 grade wear-resistant steel of all thicknesses can reach ±40HBW, resulting in significant differences in the wear resistance performance of NM450 grade wear-resistant steel.

[0028] On the other hand, the rolling process and heat treatment parameters for NM450 wear-resistant steel lack thickness-specific design. Most manufacturers use a uniform rolling temperature and heat treatment holding time for NM450 wear-resistant steel of different thicknesses. This process design ignores the differences in heat transfer properties, phase transformation kinetics, and microstructure formation mechanisms of NM450 wear-resistant steel with different thicknesses. NM450 wear-resistant steel with a thickness >20mm is prone to incomplete martensitic transformation in the core region, leading to segregation in the latter half of the microstructure, resulting in unstable wear resistance and a significantly shortened service life. NM450 wear-resistant steel with a thickness ≤20mm is prone to localized coarse grains or excessive retained austenite, leading to excessive overall hardness, reduced toughness, and a risk of processing cracks.

[0029] Third, there is an imbalance between production cost and quality for NM450 grade wear-resistant steel. To increase the hardness of NM450 grade wear-resistant steel, excessive amounts of precious alloying elements such as molybdenum and nickel are added, leading to a 15%-20% increase in production cost compared to conventional products. Furthermore, some products suffer from inadequate impurity control during production, with phosphorus content ≥0.015% and sulfur content ≥0.005%, making NM450 grade wear-resistant steel prone to cracking defects during processing and welding, affecting product qualification rate and safety in use.

[0030] An embodiment of the first aspect of this application provides an NM450 grade wear-resistant steel, wherein the Brinell hardness of the NM450 grade wear-resistant steel is 435HBW-460HBW. The NM450 grade wear-resistant steel comprises the following components in weight percentage: C: 0.19%-0.22%, Si: 0.35%-0.55%, Mn: 1.25%-1.40%, P≤0.012%, S≤0.003%, Cr: 0.30%-0.75%, Nb: 0.010%-0.020%, Ti: 0.012%-0.022%, B: 0.0012%-0.0023%, As≤0.007%, Als: 0.025%-0.050%, N≤0.0050%, with the remainder being Fe and impurities.

[0031] In the composition design of the NM450 grade wear-resistant steel in this application:

[0032] Carbon (C): 0.19%-0.22%. Carbon is the balancing element between hardness and toughness in NM450 grade wear-resistant steel. Carbon is a solid solution strengthening element in NM450 grade wear-resistant steel. Carbon atoms are dissolved in the ferrite lattice, causing ferrite lattice distortion. This lattice distortion forms localized stress concentration regions around carbon atoms. These stress concentration regions hinder dislocation movement under stress in NM450 grade wear-resistant steel, thereby increasing its yield strength, tensile strength, and hardness, and ultimately improving its wear resistance. The carbon weight percentage is controlled at 0.19%-0.22%, based on the strengthening mechanism of lattice distortion and the need for hardness balance. If the carbon content is too low, the number of carbon atoms embedded in the interstitial lattice is insufficient, the degree of ferrite lattice distortion is weak, the solid solution strengthening effect is not obvious, and the hardness of NM450 grade wear-resistant steel is low. If the carbon content is too high, the excess carbon atoms will exceed the solid solution limit of ferrite. The excess carbon atoms will precipitate in large quantities, forming a continuous network of carbides. This not only exacerbates the inhomogeneity of the crystal lattice distortion but also leads to a decrease in the toughness of NM450 grade wear-resistant steel. NM450 grade wear-resistant steel is prone to defects such as cold brittleness and weld cracks, making it unsuitable for the processing requirements of engineering machinery. Therefore, controlling the carbon content allows carbon atoms to fully and uniformly dissolve in the ferrite lattice, achieving appropriate control of lattice distortion, thus balancing the hardness, wear resistance, and toughness of NM450 grade wear-resistant steel.

[0033] Si: 0.35%-0.55%. Silicon acts as a deoxidizer in NM450 grade wear-resistant steel. At the end of steelmaking, silicon combines with oxygen to form silicon dioxide, thus removing dissolved oxygen from the molten steel and improving its purity. Silicon atoms can also dissolve in ferrite, enhancing the strength and hardness of NM450 grade wear-resistant steel. During the rolling and heat treatment process of NM450 grade wear-resistant steel, the billet forms a uniform austenitic structure after high-temperature heating. Silicon atoms dissolve in the austenite lattice, causing slight distortion of the austenite lattice. This slight distortion hinders the phase transformation from austenite to ferrite and pearlite, thus prolonging the transformation time. When the thickness of NM450 wear-resistant steel is greater than 20mm, the core cooling rate of NM450 wear-resistant steel is slower. The longer transformation time from austenite to ferrite and pearlite can enable the core to obtain martensitic structure, thereby improving the hardenability and hardness uniformity of NM450 wear-resistant steel.

[0034] Mn: 1.25%-1.40%. Manganese is used to expand the austenite region, lowering the critical transformation temperature of the billet and widening the temperature range in which austenite can stably exist. This allows the steel plate to maintain its austenitic state even at higher cooling rates, providing sufficient time for martensitic transformation and thus improving the hardenability of NM450 grade wear-resistant steel. Simultaneously, manganese atoms are uniformly dissolved in the austenite lattice, inducing slight distortion of the austenite lattice, thereby increasing the strength of NM450 grade wear-resistant steel. However, manganese is prone to segregation. If the manganese content exceeds 1.40%, the hardenability in the high-manganese region is too strong, easily forming a hard and brittle martensitic structure after cooling, resulting in decreased toughness. In regions with low manganese content, insufficient hardenability leads to the formation of soft structures such as ferrite and pearlite, resulting in insufficient hardness and strength. This ultimately causes problems in NM450 grade wear-resistant steel, including excessive hardness fluctuations, insufficient local wear resistance, and susceptibility to cracking during processing, making it unable to meet the requirement of stable performance across all specifications. If the Mn content is below 1.25%, the solid solution and hardenability-enhancing effects of manganese are not fully realized, especially in the core of the cast billet, which is difficult to fully harden, failing to achieve the hardness target of NM450 grade.

[0035] Cr: 0.30%-0.75%. Chromium is a key element for achieving consistent hardness across all thicknesses. Chromium combines with carbon to form alloy carbides, which are dissolved in austenite, increasing the stability of cold austenite and thus improving the hardenability of NM450 wear-resistant steel. Reducing the amount of chromium added in NM450 wear-resistant steel with a thickness ≤20mm solves the problem of over-quenching leading to brittleness. Increasing the amount of chromium added in NM450 wear-resistant steel with a thickness >20mm utilizes chromium's high hardenability to penetrate thicker steel plates, achieving uniform hardenability from the surface to the core. Furthermore, the high hardness of alloy carbides further enhances the wear resistance of NM450 wear-resistant steel.

[0036] Nb: 0.010%-0.020%. Ti: 0.012%-0.022%. Niobium and titanium are grain refiners. Niobium and titanium combine with carbon and nitrogen to form extremely fine carbonitrides. These carbonitrides are distributed within austenite, hindering dislocation movement in NM450 wear-resistant steel under stress, thus improving its strength. The toughness of NM450 wear-resistant steel is related to the austenite grain size. During rolling, these carbonitrides prevent austenite grains from growing at high temperatures. The fine austenite grains transform into fine, uniform martensite during quenching. Compared to coarse martensite, fine martensite has lower internal stress and more interfaces between martensite laths, which alleviates quenching stress, thereby improving the toughness, impact resistance, and machinability of NM450 wear-resistant steel.

[0037] B: 0.0012%-0.0023%. Boron is a trace element with high hardenability. Boron possesses extremely strong hardenability; during the austenitization stage, boron atoms dissolved in the austenite grain boundaries spontaneously migrate and aggregate towards the higher-energy austenite grain boundary regions through atomic diffusion, hindering the phase transformation of austenite to non-martensite. This allows the steel plate to obtain a fully martensitic structure at a lower cooling rate, thereby improving the hardenability of NM450 grade wear-resistant steel. Controlling the amount of boron added within the trace range allows it to exert its hardenability effect. Excessive addition of boron leads to excessive segregation of boron atoms at the austenite grain boundaries, causing austenite grain boundary embrittlement and reducing the toughness of NM450 grade wear-resistant steel. When boron is added in combination with niobium, it can form a complex carbonitridium compound, stabilizing and strengthening the austenite grain boundaries.

[0038] Als: 0.025%-0.050%. Acid-soluble aluminum is a deoxidizer that reacts with oxygen in molten steel to form aluminum oxide, thereby removing dissolved oxygen. Simultaneously, acid-soluble aluminum combines with trace amounts of nitrogen in the billet to form fine aluminum nitride particles, which precipitate at austenite grain boundaries and intragranular defects, hindering the slippage and migration of austenite grain boundaries. This controls the austenite grain size within a small range, thus improving the toughness of NM450 grade wear-resistant steel.

[0039] N: ≤0.0050%. Nitrogen readily forms carbonitrides with niobium and titanium. If the nitrogen content exceeds 0.0050%, it will form coarse carbonitrides with niobium and titanium. These coarse carbonitrides lack toughness, and the interface between them and austenite exhibits lattice distortion and stress concentration. These distortions and stress concentrations become mechanically weak points in NM450 wear-resistant steel, negatively impacting its toughness, plasticity, and machinability. Simultaneously, nitrogen atoms compete with boron atoms for sites in the austenite grain boundary regions, thus reducing the hardenability of boron atoms. Furthermore, the amount of nitrogen added can synergistically with the amount of acid-soluble aluminum added; a reasonable weight percentage of acid-soluble aluminum can consume free nitrogen.

[0040] P: ≤0.012%. Phosphorus dissolved in ferrite causes lattice distortion, which hinders the slippage of dislocations in NM450 wear-resistant steel under stress, causing it to lose its plastic deformation ability at low temperatures. When NM450 wear-resistant steel is subjected to impact loads, it cannot disperse stress through plastic deformation and is prone to brittle fracture.

[0041] S: ≤0.003%. Sulfur readily combines with manganese to form manganese sulfide inclusions. Manganese sulfide inclusions are solid, brittle inclusions that disrupt the continuity of the martensitic structure. When NM450 wear-resistant steel is subjected to wear and impact, microcracks easily form at the interface between the inclusions and the martensitic structure, reducing the service life of NM450 wear-resistant steel.

[0042] As content: ≤0.007%. Arsenic dissolved in ferrite causes lattice distortion, thus reducing the plasticity and toughness of NM450 grade wear-resistant steel. Furthermore, arsenic has a tendency to agglomerate at grain boundaries, spontaneously migrating and accumulating there through atomic diffusion. This results in a much higher arsenic content at the grain boundaries compared to within the ferrite grains, significantly weakening the bonding force between iron atoms at the grain boundaries. When NM450 grade wear-resistant steel is subjected to external forces, the bonding points between iron and arsenic atoms at the grain boundaries are prone to separation, leading to intergranular microcracks. These microcracks can then propagate through the grain boundaries into the surrounding grains, eventually forming penetrating macroscopic cracks.

[0043] Thus, this application, based on carbon (C), controls the weight percentages of Mn and Si to improve the hardness of NM450 grade wear-resistant steel, controls the weight percentages of Cr and B to improve its hardenability, and controls the weight percentages of Nb, Ti, and Als to improve its toughness. Simultaneously, by controlling the weight percentages of impurities P, S, N, and As, it achieves a Brinell hardness of 420 HBW-480 HBW for NM450 grade wear-resistant steel, with a hardness fluctuation ≤25 HBW, thus solving the problems of large hardness fluctuations and unstable wear resistance in NM450 grade wear-resistant steel. While achieving stable hardness and wear resistance, NM450 grade wear-resistant steel also possesses good toughness and impact resistance, meeting the requirements of high-end engineering machinery. Furthermore, by avoiding excessive addition of precious alloys such as molybdenum and nickel, the synergistic effect of each component improves the hardness of NM450 grade wear-resistant steel while reducing production costs by 15%-20%.

[0044] In some embodiments, the thickness of NM450 grade wear-resistant steel is L1, where L1 satisfies the condition: 10mm ≤ L1 ≤ 20mm. In this case, the weight percentages of some components in the NM450 grade wear-resistant steel are adjusted: Si: 0.35%-0.45%, Mn: 1.30%-1.40%, Cr: 0.30%-0.40%, B: 0.0012%-0.0022%. The hardenability requirement of NM450 grade wear-resistant steel in this thickness range is relatively low. Therefore, reducing the weight percentages of hardenability elements Cr, B, and Si controls the production cost of NM450 grade wear-resistant steel while addressing the problem of excessive hardenability elements causing the NM450 grade wear-resistant steel to become hard and brittle. Simultaneously, maintaining the weight percentage of Mn in the medium-high range and the weight percentage of Si in the medium-low range adapts to the hardness requirements of NM450 grade wear-resistant steel in this thickness range. In this way, by narrowing the weight percentage range of key elements, standardized control of NM450 grade wear-resistant steel with a thickness of 10mm-20mm can be achieved, reducing composition fluctuations during the production process.

[0045] In some embodiments, the thickness of NM450 grade wear-resistant steel is L2, where L2 satisfies the condition: 20mm < L2 ≤ 50mm. In this case, the weight percentages of some components in the NM450 grade wear-resistant steel are adjusted: Si: 0.45%-0.55%, Mn: 1.25%-1.35%, Cr: 0.60%-0.75%, B: 0.0013%-0.0023%. NM450 grade wear-resistant steel in this thickness range has relatively high hardenability requirements. Therefore, by increasing the weight percentages of hardenability elements Cr, B, and Si, uniform hardenability is achieved from the surface to the core of the billet. This addresses the hardness stratification problem of NM450 grade wear-resistant steel in the 20mm-50mm thickness range from a compositional perspective, thereby resolving the issue of large hardness fluctuations in NM450 grade wear-resistant steel across the entire thickness range of 10mm-50mm. Mn is a segregating element, and during high-temperature rolling and cooling, Mn tends to accumulate at austenite grain boundaries. To achieve hardenability, boron (B) also segregates at austenite grain boundaries. This simultaneous enrichment of both elements at austenite grain boundaries exacerbates the compositional difference between the austenite grain boundaries and the austenite grain interior, resulting in a segregation state characterized by excessive element concentration at the austenite grain boundaries and low element content within the austenite grain interior. This segregation leads to the formation of hard and brittle martensite at the austenite grain boundaries upon cooling, reducing toughness. Soft phases such as ferrite and pearlite easily precipitate within the austenite grain interior, thus reducing hardness and wear resistance. This results in large hardness fluctuations in NM450 grade wear-resistant steel across the entire thickness range of 10mm-50mm, making it prone to cracking during processing. Therefore, when producing NM450 grade wear-resistant steel with a thickness of 20mm-50mm, the upper limit of the weight percentage of manganese (Mn) needs to be reduced.

[0046] Secondly, such as Figure 1 As shown, this application provides a method for producing NM450 grade wear-resistant steel. This method is used to produce the NM450 grade wear-resistant steel provided in the first aspect of this application, and includes the following steps:

[0047] S100: The components of NM450 grade wear-resistant steel of the target thickness are mixed and smelted to obtain a billet.

[0048] According to production needs, molten iron is smelted from the blast furnace at a temperature ≥1300℃. The molten iron is then desulfurized in a mechanical mixing station to ensure sulfur content ≤0.003%, reducing the risk of cracking in NM450 grade wear-resistant steel due to excessive sulfur. The desulfurized molten iron is then transferred to a converter and smelted with either L1 or L2 thickness NM450 grade wear-resistant steel containing all components except iron. Lime is added during the smelting process so that the resulting slag absorbs phosphorus from the molten steel. After dephosphorization, the molten steel undergoes vacuum circulation degassing in a ladle refining furnace to remove hydrogen, nitrogen, and oxygen, yielding the first molten steel. This reduces the risk of porosity and white spots in NM450 grade wear-resistant steel caused by hydrogen, nitrogen, and oxygen. The first molten steel obtained from the vacuum circulation degassing process is then continuously cast to form a billet.

[0049] S200: The billet is subjected to slow cooling, heating treatment and descaling treatment in sequence;

[0050] Slow cooling of the billet obtained by continuous casting can allow residual inclusions in the billet to float to the surface, improve the density of the billet, and reduce defects such as porosity and gas holes inside the billet, thereby reducing the risk of cracking caused by internal defects in the billet during subsequent rolling.

[0051] In some embodiments, the continuously cast billets have different thicknesses, such as 200 mm, 250 mm, and 300 mm. The slow cooling time for a 200 mm billet is ≥48 h, for a 250 mm billet it is ≥60 h, and for a 300 mm billet it is ≥72 h. The greater the thickness, the longer the slow cooling time, which reduces the risk of cracking during subsequent rolling and provides high-quality billets for subsequent rolling processes.

[0052] After the billet is slowly cooled, it is then heated to raise its temperature uniformly to a range suitable for rolling, thereby reducing the deformation resistance during subsequent billet rolling.

[0053] In some embodiments, after slow cooling, the billet is continuously heated to different preset temperatures at a heating rate of 9-11 min / cm, then homogenized and held at 1190℃-1230℃. The final furnace exit temperature after holding is 1180℃-1220℃. Specifically, the holding time for a 200mm billet is ≥30 min, for a 250mm billet ≥40 min, and for a 300mm billet ≥50 min. The different preset temperatures are: a first preset temperature of 600℃-1100℃, a second preset temperature of 1120℃-1220℃, and a third preset temperature of 1220℃-1260℃. This ensures uniform heating of the billet, sufficient austenitization, reduced thermal stress, lowered risk of cracking during subsequent rolling, and provides high-quality billet for subsequent rolling processes.

[0054] After the billet is heated, descaling is performed to remove impurities such as iron oxide scale from the billet surface. This reduces the risk of iron oxide scale being pressed into the billet surface during rolling, causing defects such as pitting and inclusions. Simultaneously, it reduces the probability that iron oxide scale will affect the surface quality and subsequent processing performance of the billet. Descaling can be performed 1 to 3 times.

[0055] S300: The dephosphorized billet is rolled in two stages to obtain a steel plate with the target thickness. The preset rolling temperature of the first rolling stage is higher than the preset rolling temperature of the second rolling stage.

[0056] The descaled billet undergoes a two-stage rolling process. The first stage employs high-temperature rolling to maintain a uniform austenitic structure while simultaneously breaking down coarse austenitic grains through plastic deformation, thus thinning the billet. The second stage uses low-temperature rolling to further break down the austenitic grains, resulting in a fine and uniform austenitic structure. The temperature gradient design of these two stages is adapted to the heat dissipation characteristics of steel plates with different target thicknesses, ensuring uniform billet deformation during rolling. This lays a high-quality microstructure foundation for subsequent martensitic transformation and simultaneously improves the strength, toughness, and wear resistance of NM450 grade wear-resistant steel, ensuring stable performance across all thickness specifications.

[0057] S400: The rolled steel plate is cooled and heat-treated to obtain NM450 grade wear-resistant steel.

[0058] After the final rolling in the second rolling stage, a cooling treatment is performed to quickly fix the fine-grained austenitic structure obtained during the rolling process. Following cooling, the steel plate undergoes heat treatment. Heat treatment transforms the fine-grained austenitic structure into a uniform tempered martensite structure. The synergistic effect of cooling and heat treatment ultimately achieves a balance between hardness, toughness, and wear resistance in NM450 grade wear-resistant steel, meeting the hardness requirements of 435HBW-460HBW and the hardness fluctuation index of ≤25HBW for NM450 grade wear-resistant steel.

[0059] In some embodiments, when cooling the rolled steel plate, if the target thickness is 10mm≤L1≤20mm, the rolled steel plate is air-cooled and naturally cooled to room temperature. If the target thickness is 20mm<L1≤50mm, the rolled steel plate is heated to 600℃-660℃ and held at that temperature.

[0060] In some embodiments, the steel plate is pre-straightened after rolling to correct its shape, and then hot-straightened after cooling, thereby eliminating the internal stress of the steel plate and ensuring that the flatness and mechanical properties of NM450 grade wear-resistant steel meet the standards.

[0061] In some embodiments, such as Figure 2 As shown, the components of NM450 grade wear-resistant steel, which is produced to the target thickness, are mixed and smelted, including:

[0062] S1001: Prepare the components of NM450 grade wear-resistant steel according to the target thickness.

[0063] Preparing the components of NM450 grade wear-resistant steel with thickness L1 or L2 according to actual production needs can improve the production adaptability of NM450 grade wear-resistant steel and the utilization rate of each component.

[0064] S1002: Vacuum circulation degassing treatment is performed on each component of the mixed NM450 grade wear-resistant steel to obtain the first molten steel. The vacuum holding time of the vacuum circulation degassing treatment is T1, and T1 satisfies: T1≥15min.

[0065] Vacuum holding time T1≥15min during vacuum circulation degassing can remove gaseous impurities such as hydrogen, oxygen and nitrogen from molten steel, reduce internal defects such as porosity and looseness in NM450 grade wear-resistant steel, thereby reducing the risk of cracking of NM450 grade wear-resistant steel in subsequent processing and improving the processing and welding performance of NM450 grade wear-resistant steel.

[0066] S1003: The first molten steel is continuously cast to obtain a billet. The continuous casting superheat temperature is 10℃-25℃.

[0067] In continuous casting, molten steel needs to cool from a liquid state to a solid state to form a billet. The superheat determines the fluidity, solidification rate, and solidification microstructure of the molten steel. Higher superheat results in better fluidity but slower solidification, which can easily lead to grain growth and compositional segregation. Lower superheat results in poorer fluidity and faster solidification, which can easily lead to poor billet formation and difficulty in billet pulling. Controlling the superheat in continuous casting between 10℃ and 25℃ promotes rapid austenite nucleation and slow growth, laying the foundation for grain refinement and the strengthening effects of elements such as Nb and Ti during subsequent rolling. Simultaneously, it controls the diffusion rate of elements, ensuring uniform billet composition and reducing the risk of cracking during subsequent rolling.

[0068] In some embodiments, such as Figure 3 As shown, the descaled billet undergoes a two-stage rolling process, including:

[0069] S3001: In the first rolling stage, the descaled billet is rolled at a preset rolling temperature, and the reduction rate of the last pass is controlled to be ≥20% to obtain a billet of the target thickness.

[0070] The purpose of the first rolling stage is to roll the descaled billet into a preheated billet of the target thickness. In this stage, the billet thickness is gradually reduced using multiple passes. The reduction amount in each pass is rationally allocated based on the initial billet thickness and the target preheated billet thickness, with the final pass reducing the thickness by ≥20%. For example, if the initial billet thickness is 200mm and the target preheated billet thickness is 50mm, and the previous passes cumulatively reduce the thickness by 130mm, the final pass reduces it by 20mm, resulting in a reduction rate of 20%. By controlling the reduction rate of ≥20% in the final pass of the first rolling stage, the billet undergoes plastic deformation, breaking down coarse austenite grains and providing a foundation for subsequent fine rolling to refine the austenite grains. After the first rolling stage, the resulting preheated billet has no surface defects such as cracks, peeling, or inclusions, providing a good raw material for the precise rolling in the second rolling stage.

[0071] S3002: In the second rolling stage, the second preset initial rolling temperature and the second preset final rolling temperature are controlled according to the target thickness of NM450 grade wear-resistant steel, and the cumulative reduction rate of the last three passes is controlled to be ≥25%.

[0072] The purpose of the second rolling stage is to refine austenite grains through precise temperature control and reduction rate management, resulting in a uniform and dense austenite microstructure in the steel plate. This stage employs finishing passes to gradually thin the billet to the target thickness. Based on the billet thickness and the target steel plate thickness, the reduction amounts in the final three passes are allocated, ensuring a cumulative reduction rate of ≥25%. For example, if the billet thickness is 50mm and the target steel plate thickness is 20mm, the final three passes reduce the billet by 8mm, 7mm, and 5mm respectively, resulting in a cumulative reduction of 20mm and a cumulative reduction rate of 40%. Simultaneously, the reduction amount in each pass is controlled to be uniform, reducing the risk of surface defects or uneven microstructure caused by excessive reduction in a single pass.

[0073] The second rolling stage's initial and final rolling temperatures, set according to thickness, are adapted to the heat dissipation characteristics of billets of different thicknesses. This reduces defects such as cracking in thinner billets and coarsening of austenite grains in thicker billets. At the same time, precise reduction rate control ensures uniform deformation of billets of different specifications and locations. Ultimately, this achieves uniform microstructure of M450 grade wear-resistant steel with a hardness fluctuation of ≤25HBW across all specifications from 10mm to 50mm, meeting the requirement of stable performance across all specifications of NM450 grade wear-resistant steel.

[0074] In some embodiments, the preset rolling temperature is ≥1080°C. This temperature range falls within the austenite formation temperature range, allowing the billet to completely transform into a uniform austenitic structure, thereby reducing rolling resistance. During the rolling process, the billet temperature can be monitored in real time using an online temperature measuring device to maintain the temperature of the first rolling stage at ≥1080°C, reducing the risk of excessive fluctuations in the preset rolling temperature affecting rolling quality.

[0075] For NM450 grade wear-resistant steel with a target thickness of L1, the second preset initial rolling temperature is ≤920℃, and the second preset final rolling temperature is 840℃-880℃. For NM450 grade wear-resistant steel with a target thickness of L2, the second preset initial rolling temperature is ≤900℃, and the second preset final rolling temperature is 820℃-860℃. NM450 grade wear-resistant steel with thicknesses of L1 or L2 adopts a high-temperature initial rolling and low-temperature final rolling design to refine the austenite grains in the billet, thereby improving the strength and toughness of the NM450 grade wear-resistant steel. Simultaneously, low-temperature final rolling promotes the formation of uniformly dispersed fine carbides of elements such as Nb and Ti, which enhance the hardness and toughness of the NM450 grade wear-resistant steel.

[0076] NM450 wear-resistant steel with a target thickness of L2 dissipates heat slowly. Therefore, lower initial and final rolling temperatures are set compared to the target thickness of L1. This ensures sufficient core deformation during rolling of the billet while addressing the issue of austenite grain coarsening due to temperature accumulation caused by slow heat dissipation, thereby increasing the hardness of NM450 wear-resistant steel. NM450 wear-resistant steel with a target thickness of L1 dissipates heat quickly. Higher initial and final rolling temperatures are set compared to the target thickness of L2 to refine the austenite grains and reduce rolling resistance.

[0077] Thus, by producing NM450 grade wear-resistant steel of varying thicknesses and employing different rolling temperatures, the austenite grain size of the billet can be controlled. This results in rolled steel plates of different thicknesses possessing fine and uniform austenite grains, thereby improving the stability of the heat treatment process. It also ensures that the quenched steel plate forms a uniform martensitic structure, reducing the probability of deformation or cracking during tempering. Ultimately, this lowers the risk of cracking during subsequent cutting and welding. Furthermore, through differentiated rolling temperature control, combined with the hardenability-enhancing effects of Cr and B, and the grain-refining strengthening effects of Nb and Ti, the goal of achieving stable hardness temperature and wear resistance while maintaining toughness in NM450 grade wear-resistant steel can be achieved while controlling production costs.

[0078] In some embodiments, such as Figure 4 As shown, the rolled steel plate undergoes heat treatment, including:

[0079] S4001: Heat the rolled steel plate to the preset quenching temperature and maintain it for the preset quenching time. The preset quenching time is controlled according to the target thickness of NM450 grade wear-resistant steel.

[0080] Heating the rolled steel sheet to a preset quenching temperature and maintaining it for a preset quenching time allows for thorough quenching, resulting in a uniform martensitic structure and thus increasing the hardness of NM450 grade wear-resistant steel. By presetting the quenching time according to thickness differences, steel sheets of varying thicknesses can be fully quenched, addressing the issue of poor hardness uniformity in NM450 grade wear-resistant steel from a process perspective. The preset quenching temperature can be 900℃-920℃.

[0081] S4002: Heat the quenched steel plate to the preset tempering temperature and maintain it for the preset tempering time.

[0082] During quenching, the austenite in the steel plate transforms into martensite, generating significant internal stress. This stress can easily lead to embrittlement of the produced NM450 grade wear-resistant steel, causing cracking and even deformation defects during subsequent processing. Heating the quenched steel plate to a preset tempering temperature and maintaining it for a preset tempering time can release quenching stress, improve the toughness and impact resistance of the NM450 grade wear-resistant steel, and solve the problem of cracking during processing due to the hardness and brittleness of the NM450 grade wear-resistant steel after quenching. The preset tempering temperature can be 280℃. The tempering time for NM450 grade wear-resistant steel with a thickness of 10mm≤L1≤20mm is 3×L1min. The tempering time for NM450 grade wear-resistant steel with a thickness of 20mm<L2≤50mm is 3×L2min. Thus, through quenching and tempering treatments, the NM450 grade wear-resistant steel can achieve the target hardness while eliminating quenching stress, thereby achieving a balance between hardness and toughness.

[0083] In some embodiments, the preset quenching time is controlled according to the target thickness of NM450 grade wear-resistant steel, including:

[0084] S40011: When the target thickness of NM450 grade wear-resistant steel is L1, the preset quenching time of the steel plate is L1+T2, where T2 satisfies: 20min≤T2≤30min;

[0085] For example, the quenching time for 10mm thick NM450 grade wear-resistant steel is 30-40 minutes, and the quenching time for 20mm thick NM450 grade wear-resistant steel is 40-50 minutes.

[0086] S40012: When the target thickness of the NM450 grade wear-resistant steel is L2, the preset quenching time of the billet is 1.5×L2+T3, where T3 satisfies: 25min≤T3≤35min.

[0087] For example, the quenching time for 25mm thick NM450 grade wear-resistant steel is 62.5min-72.5min, and the quenching time for 50mm thick NM450 grade wear-resistant steel is 100min-110min.

[0088] Steel plates of different thicknesses exhibit varying thermal conductivity; the greater the thickness, the slower the heat transfer. Using a uniform quenching time can easily lead to problems such as incomplete austenitization and insufficient hardenability in thick steel plates, or overheating in thin steel plates resulting in coarsening of austenite grains. By controlling the quenching time, it is possible to ensure full hardenability of all NM450 grade wear-resistant steel plates ranging from 10mm to 50mm, thus resolving the issue of poor hardness uniformity in NM450 grade wear-resistant steel.

[0089] Exemplary embodiments according to this application will now be described in more detail with reference to the accompanying drawings. It should be understood that these exemplary embodiments may be implemented in various forms and should not be construed as being limited to the embodiments set forth herein.

[0090] The embodiments and comparative examples of this application were produced according to the following steps:

[0091] (1) According to production needs, the components of the wear-resistant steel with a thickness of 10mm≤L1≤20mm or 20mm<L2≤50mm or the comparative steel are mixed and smelted. The weight percentage of each component of the wear-resistant steel in the examples and comparative examples is shown in Table 1. Among them, the vacuum holding time of the vacuum circulation degassing treatment is ≥15min, and the continuous casting superheating temperature is 10℃-25℃.

[0092] (2) Slow cooling of 200mm billet obtained by continuous casting for ≥48h, slow cooling of 250mm billet obtained by continuous casting for ≥60h, and slow cooling of 300mm billet obtained by continuous casting for ≥72h.

[0093] (3) After slow cooling, the billet is first heated to 600℃-1100℃ at a heating rate of 9min / cm-11min / cm, then to 1120℃-1220℃ at a heating rate of 9min / cm-11min / cm, then to 1220℃-1260℃ at a heating rate of 9min / cm-11min / cm, and finally to 1190℃-1230℃ at a heating rate of 9min / cm-11min / cm for homogenization and holding. The furnace exit temperature after holding is 1180℃-1220℃. The holding time for 200mm billets is ≥30min, for 250mm billets it is ≥40min, and for 300mm billets it is ≥50min.

[0094] (4) After heating, the billet is descaled 1-3 times and then rolled in two stages. The rolling temperature of the first stage is ≥1080℃ to obtain a billet of 50mm-90mm. The reduction rate of the last pass is ≥20%. In the second stage, the initial rolling temperature for producing NM450 grade wear-resistant steel with a thickness of 10mm≤L1≤20mm is ≤920℃, the final rolling temperature is 840℃-880℃, and the cumulative reduction rate of the last three passes is ≥25%. The initial rolling temperature for producing NM450 grade wear-resistant steel with a thickness of 20mm<L2≤50mm is ≤900℃, the final rolling temperature is 820℃-860℃, and the cumulative reduction rate of the last three passes is ≥25%.

[0095] (5) The 10mm-20mm steel plates obtained after rolling are air-cooled and naturally cooled to room temperature. The 20mm-50mm steel plates obtained after rolling are heated to 600℃-660℃ and kept at that temperature.

[0096] (6) The cooled steel plate is quenched at 900℃-920℃. The quenching time for NM450 grade wear-resistant steel with a thickness of 10mm≤L1≤20mm is L1+(20min-30min), and the quenching time for NM450 grade wear-resistant steel with a thickness of 20mm<L2≤50mm is 1.5×L2+(25min-35min).

[0097] (7) The quenched billet shall be tempered within 48 hours at a tempering temperature of 280℃. The tempering time for NM450 grade wear-resistant steel with a thickness of 10mm≤L1≤20mm shall be 3×L1min. The tempering time for NM450 grade wear-resistant steel with a thickness of 20mm<L2≤50mm shall be 3×L2min. After tempering, the wear-resistant steel shall be finished and stacked for 7 days. After inspection for cracks, it shall be put into storage.

[0098] The process parameters for the wear-resistant steels of the embodiments and comparative examples of this application are shown in Tables 2 and 3.

[0099] The wear-resistant steel formed above was subjected to mechanical property tests and metallographic tests. The results of the mechanical property tests are shown in Table 3, and the results of the metallographic tests are shown in Table 4. Figure 5 .

[0100] Metallographic testing: Tests were conducted according to B / T 13298-2015, the method for examining the microstructure of metals.

[0101] Brinell hardness test: The test shall be conducted in accordance with GB / T 231.1-2018 Brinell hardness test method for metallic materials.

[0102] Cold bending performance test: The test shall be conducted in accordance with GB / T 232-2024 Test Method for Bending of Metallic Materials.

[0103] Surface quality test: The test shall be conducted in accordance with the general requirements for surface quality of hot-rolled steel plates in GB / T 14977-2025.

[0104] Table 1. Weight percentage of each component in the embodiments and comparative examples of this application.

[0105]

[0106] Table 2. Process parameters for embodiments and comparative examples of this application.

[0107]

[0108] Table 3. Heat treatment process parameters and test results of the embodiments and comparative examples of this application.

[0109]

[0110] As shown in Table 3 above, the wear-resistant steels prepared in Comparative Examples 1, 2, and 3 have problems with unsatisfactory cold bending performance and surface quality. As shown in Table 1 above, the weight percentages of each component in the wear-resistant steels prepared in Comparative Examples 1, 2, and 3 do not conform to the weight percentages of each component used in the preparation of NM450 wear-resistant steel.

[0111] The weight percentages of impurity elements P, S, As, and N in Comparative Example 1 were all higher than the specifications for preparing NM450 grade wear-resistant steel with a thickness of 10mm ≤ L1 ≤ 20mm, resulting in localized excessive inclusions on the surface of the wear-resistant steel prepared in Comparative Example 1. The weight percentages of C, hardening elements Mn and Cr, and fine-grain strengthening elements Nb and Ti in Comparative Example 1 were all lower than the specifications for preparing NM450 grade wear-resistant steel with a thickness of 10mm ≤ L1 ≤ 20mm. In addition, the second-stage rolling temperature was relatively high, resulting in coarse austenite structure. Therefore, the wear-resistant steel prepared in Comparative Example 1 had a low hardness, as low as 431 HBW, with hardness fluctuations reaching 34 HBW.

[0112] The weight percentages of impurity elements P, S, As, and N in Comparative Example 2 were all higher than those required for preparing NM450 grade wear-resistant steel with a diameter of 20mm < L2 ≤ 50mm. This resulted in lower toughness and unsatisfactory cold bending performance in the wear-resistant steel prepared in Comparative Example 1. Furthermore, the weight percentages of C, hardening elements Cr and B, grain refinement elements Nb and Ti, and hardness enhancement element Si in Comparative Example 2 were all higher than those required for preparing NM450 grade wear-resistant steel with a diameter of 20mm < L2 ≤ 50mm. Additionally, the tempering temperature was lower than the preset tempering temperature for NM450 grade wear-resistant steel. This resulted in incomplete release of quenching stress within the quenched steel plate, leading to high brittleness and poor toughness. Consequently, the hardness and toughness of the wear-resistant steel prepared in Comparative Example 2 were not balanced, resulting in unsatisfactory cold bending performance and a hardness fluctuation of 35 HBW.

[0113] The weight percentages of impurity elements P, S, and N in Comparative Example 3 were all higher than those for preparing NM450 grade wear-resistant steel with a diameter of 20mm < L2 ≤ 50mm. The weight percentages of C, hardenability elements Cr and B, and fine-grain strengthening elements Nb, Ti, Si, and Als in Comparative Example 3 were all lower than those for preparing NM450 grade wear-resistant steel with a diameter of 20mm < L2 ≤ 50mm. Furthermore, the tempering temperature was lower than the preset tempering temperature for NM450 grade wear-resistant steel, and the tempering time was shorter. As a result, the quenching stress in the steel plate after quenching was not completely released, leading to lower toughness of the wear-resistant steel prepared in Comparative Example 2 and cracking in the cold bending test.

[0114] As shown in Tables 1, 2, and 3 above, by differentiating the weight percentages of the components in the 10mm-50mm NM450 grade wear-resistant steel, and combining this with a two-stage differentiated rolling process and a differentiated heat treatment process, the NM450 grade wear-resistant steel prepared in Examples 1 to 5 achieved a stable hardness of 435HBW-460HBW, with a hardness fluctuation of ≤25HBW. This solved the problems of poor hardness uniformity and large performance fluctuations in the 10mm-50mm NM450 grade wear-resistant steel. By strictly controlling the low impurity standards of P≤0.012% and S≤0.003%, and with optimized rolling and heat treatment parameters, the cold bending performance of the NM450 grade wear-resistant steel was fully qualified. Preheating to ≥150℃ before welding was sufficient to meet processing requirements, overcoming the defect of easy cracking during welding of NM450 grade wear-resistant steel. At the same time, there is no need to add precious alloys such as Mo and Ni. High hardness is achieved through the synergistic effect of Si, Cr and B. The production cost is reduced by 12%-15% compared with existing high-end wear-resistant steel. It is also compatible with existing 4300mm wide and thick plate mill equipment for large-scale production, meeting the stringent usage requirements of key components of engineering machinery.

[0115] pass Figure 5 and Figure 6 It can be seen that, Figure 5 The results show that a quarter-thickness of the NM450 grade wear-resistant steel prepared in Example 3 is a uniform and fine tempered martensite structure, free of inclusions and segregation. Figure 6 The half-thickness section of the NM450 grade wear-resistant steel prepared in Example 3 shows a uniform and fine tempered martensite structure without inclusions or segregation. The metallographic data from the quarter-thickness and half-thickness sections demonstrate that the NM450 grade wear-resistant steel prepared in Example 3 possesses good hardness uniformity and wear resistance.

[0116] It should also be noted that the terms "some embodiments" or "embodiments" used in this application refer to specific features, structures, or characteristics described in connection with those embodiments, which are included in at least one embodiment described in the general description of this application. The appearance of the same expression in multiple places in the specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in connection with any embodiment, the intention is to suggest that implementing such a feature, structure, or characteristic in conjunction with other embodiments also falls within the scope of this application.

[0117] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An NM450 grade wear-resistant steel, characterized in that, The NM450 grade wear-resistant steel has a Brinell hardness of 435HBW-460HBW. The thickness of the NM450 grade wear-resistant steel is L1 or L2, where L1 satisfies: 10mm ≤ L1 ≤ 20mm, and L2 satisfies: 20mm < L2 ≤ 50mm. When the thickness of the NM450 grade wear-resistant steel is L1, the NM450 grade wear-resistant steel comprises the following components by weight percentage: C: 0.19%-0.22%, Si: 0.35%. %-0.45%, Mn: 1.30%-1.40%, P≤0.012%, S≤0.003%, Cr: 0.30%-0.40%, Nb: 0.010%-0.020%, Ti: 0.012%-0.022%, B: 0.0012%-0.0022%, As≤0.007%, Als: 0.025%-0.050%, N≤0.0050%, the remainder being Fe and impurities; When the thickness of the NM450 grade wear-resistant steel is L2, the NM450 grade wear-resistant steel comprises the following components by weight percentage: C: 0.19%-0.22%, Si: 0.45%-0.55%, Mn: 1.25%-1.35%, P≤0.012%, S≤0.003%, Cr: 0.60%-0.75%, Nb: 0.010%-0.020%, Ti: 0.012%-0.022%, B: 0.0013%-0.0023%, As≤0.007%, Als: 0.025%-0.050%, N≤0.0050%, with the remainder being Fe and impurities; The production method of the NM450 grade wear-resistant steel includes: mixing and smelting the components of the NM450 grade wear-resistant steel to obtain a billet; subjecting the billet to slow cooling, heat treatment, and descaling treatment in sequence; subjecting the descaled billet to two-stage rolling to obtain a steel plate that meets the target thickness, wherein the preset rolling temperature of the first rolling stage is higher than the preset rolling temperature of the second rolling stage; and subjecting the rolled steel plate to cooling and heat treatment to obtain the NM450 grade wear-resistant steel. The two-stage rolling process of the descaled billet includes: in the first rolling stage, the descaled billet is rolled at a preset rolling temperature, and the reduction rate of the last pass is controlled to be ≥20% to obtain a billet of the target thickness; in the second rolling stage, the second preset starting rolling temperature and the second preset finishing rolling temperature are controlled according to the target thickness of the NM450 grade wear-resistant steel, and the cumulative reduction rate of the last three passes is controlled to be ≥25%. The heat treatment of the rolled steel plate includes: heating the rolled steel plate to a preset quenching temperature and maintaining it for a preset quenching time, wherein the preset quenching time is controlled according to the target thickness of the NM450 grade wear-resistant steel; and heating the quenched steel plate to a preset tempering temperature and maintaining it for a preset tempering time. When the thickness of the NM450 grade wear-resistant steel is L1, the production method of the NM450 grade wear-resistant steel includes: the second preset initial rolling temperature is ≤920℃, the second preset final rolling temperature is 840℃-880℃, the preset quenching time is L1+T2min, T2 satisfies: 20min≤T2≤30min, the preset tempering temperature is 280℃, and the preset tempering time is 3×L1min; When the thickness of the NM450 grade wear-resistant steel is L2, the production method of the NM450 grade wear-resistant steel includes: the second preset initial rolling temperature is ≤900℃, the second preset final rolling temperature is 820℃-860℃, the preset quenching time is 1.5×L2+T3min, T3 satisfies: 25min≤T3≤35min, the preset tempering temperature is 280℃, and the preset tempering time is 3×L2min.

2. The NM450 grade wear-resistant steel according to claim 1, characterized in that, The Brinell hardness fluctuation of the NM450 grade wear-resistant steel is ≤25HBW.

3. A method for producing NM450 grade wear-resistant steel, characterized in that, The method for producing NM450 grade wear-resistant steel is used to produce NM450 grade wear-resistant steel as described in any one of claims 1 to 2, the method comprising: The components of NM450 grade wear-resistant steel with the target thickness are mixed and smelted to obtain a billet. The cast billet is subjected to slow cooling, heating treatment and descaling treatment in sequence; The descaled billet is subjected to two-stage rolling to obtain a steel plate that meets the target thickness. The preset rolling temperature of the first rolling stage is higher than the preset rolling temperature of the second rolling stage. The rolled steel plate is cooled and heat-treated to obtain the NM450 grade wear-resistant steel.

4. The method for producing NM450 grade wear-resistant steel according to claim 3, characterized in that, The process of mixing and smelting the components of NM450 grade wear-resistant steel to produce the target thickness includes: Prepare the components of the NM450 grade wear-resistant steel according to the target thickness; The components of the mixed NM450 grade wear-resistant steel are subjected to vacuum circulation degassing treatment to obtain the first molten steel. The vacuum holding time of the vacuum circulation degassing treatment is T1, and T1 satisfies: T1≥15min; The first molten steel is subjected to continuous casting to obtain the billet, wherein the continuous casting superheat temperature is 10℃-25℃.

5. The method for producing NM450 grade wear-resistant steel according to claim 3, characterized in that, The two-stage rolling of the descaled billet includes: In the first rolling stage, the descaled billet is rolled at a preset rolling temperature, and the reduction rate of the last pass is controlled to be ≥20% to obtain a billet of the target thickness. In the second rolling stage, the second preset initial rolling temperature and the second preset final rolling temperature are controlled according to the target thickness of the NM450 grade wear-resistant steel, and the cumulative reduction rate of the last three passes is controlled to be ≥25%.

6. The method for producing NM450 grade wear-resistant steel according to claim 5, characterized in that, The preset rolling temperature is ≥1080℃; When the target thickness of the NM450 grade wear-resistant steel is L1, the second preset initial rolling temperature is ≤920℃, and the second preset final rolling temperature is 840℃-880℃. When the target thickness of the NM450 grade wear-resistant steel is L2, the second preset initial rolling temperature is ≤900℃, and the second preset final rolling temperature is 820℃-860℃.

7. The method for producing NM450 grade wear-resistant steel according to claim 3, characterized in that, The heat treatment of the rolled steel plate includes: The rolled steel plate is heated to a preset quenching temperature and held for a preset quenching time, the preset quenching time being controlled according to the target thickness of the NM450 grade wear-resistant steel. The quenched steel plate is heated to a preset tempering temperature and maintained for a preset tempering time.

8. The method for producing NM450 grade wear-resistant steel according to claim 7, characterized in that, The preset quenching time is controlled according to the thickness of the NM450 grade wear-resistant steel, including: When the target thickness of the NM450 grade wear-resistant steel is L1, the preset quenching time of the steel plate is L1+T2min, where T2 satisfies: 20min≤T2≤30min; When the target thickness of the NM450 grade wear-resistant steel is L2, the preset quenching time of the steel plate is 1.5×L2+T3min, where T3 satisfies: 25min≤T3≤35min.

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