Low-alloy high-toughness 500-hardness-level martensite wear-resistant steel and preparation method thereof

Abstract

The invention discloses low-alloy high-toughness 500-hardness-level martensite wear-resistant steel and a preparation method thereof. The method comprises the following steps: carrying out KR desulfurization, converter smelting and refining on molten iron, wherein the temperature of an argon station is required to be more than or equal to 1500 DEG C in converter smelting; the refining time is required to be longer than or equal to 45 min in the refining process, rare earth alloy is added into molten steel according to the dosage of 0.1 kg to 1 kg per ton of molten steel, and the refined molten steel is prepared from the following chemical components in percentage by mass: 0.1 percent to 0.5 percent of C, 0 to 0.7 percent of Si, 0.8 percent to 1.6 percent of Mn, 0 to 0.04 percent of P, 0 to 0.02 percent of S, 0.10 percent to 0.70 percent of Cr, 0.01 percent to 0.03 percent of Ni, 0.002 percent to 0.004 percent of Mo, 0.005 percent to 0.05 percent of La, 0.005 percent to 0.05 percent of Ce, greater than or equal to 3.0 percent of Ti / N and the balance of iron; performing continuous casting and hot rolling treatment on the refined molten steel to obtain hot-rolled steel; the superheat degree of the refined molten steel in the tundish is 10-45 DEG C; carrying out slow cooling treatment on the hot-rolled steel to obtain slowly-cooled steel; and the slowly cooled steel is subjected to heat treatment, and the low-alloy high-toughness 500-hardness-level martensite wear-resistant steel is prepared.

Description

Technical Field

[0001] The present application belongs to the technical field of wear-resistant steel production, and in particular relates to a low-alloy high-toughness 500 hardness level martensitic wear-resistant steel and a preparation method thereof. Background Art

[0002] Wear is one of the main forms of material failure. More than one million tons of steel are consumed each year due to abrasive wear. The role of wear-resistant steel is to reduce the wear and tear of mechanical parts, increase the life of the product, and extend the time before mechanical products fail due to wear. It is required to have a higher hardness value to ensure friction and wear resistance under harsh working conditions. Therefore, wear-resistant steel is a type of steel material widely used in various wear conditions, such as excavators, bulldozers, and dump trucks used in mining machinery and roadbed equipment.

[0003] The high-toughness wear-resistant materials currently used in China mainly include high manganese steel, low alloy cast iron, and low alloy steel. Among them, after high manganese steel is treated with water toughening, the surface hardness is greatly improved under high impact conditions; under low impact conditions, due to the insignificant work hardening effect, it is impossible to achieve a good wear resistance. Low alloy cast iron enhances hardness through carbides, that is, wear resistance is enhanced through high hardness, but the large difference in hardness between carbides and the matrix will cause cracks in the steel and reduce the plastic toughness of the steel. Low alloy wear-resistant steel is usually alloyed with elements such as Mn, Cr, Ni, and Mo, and then a high-hardness martensitic structure is obtained through quenching and low-temperature tempering heat treatment processes. However, the prices of alloys such as Ni and Mo are relatively high, which significantly increases the production cost of wear-resistant steel. Low alloy steel produces a wear-resistant hard phase by adding a small amount of alloying elements, and the resulting steel has good wear resistance, but the large difference in hardness between the hard phase and the matrix of low alloy steel will also cause the generation and expansion of cracks in the steel and reduce the plastic toughness of the steel.

[0004] With the progress of industrial development, various types of mechanical equipment are increasingly developing in the direction of complexity, large-scale and lightweight, which puts forward higher requirements on the toughness, wear resistance and weldability of engineering machinery components, especially in the field of mining equipment. Existing wear-resistant steel is difficult to balance hardness, cost and strong plasticity and toughness. Summary of the invention

[0005] The embodiment of the present application provides a low-alloy high-toughness 500 hardness level martensitic wear-resistant steel plate and a preparation method thereof, which can take into account the hardness, strength, plasticity, toughness and cost of the wear-resistant steel.

[0006] In a first aspect, the present application provides a method for preparing a low-alloy, high-toughness, 500-hardness martensitic wear-resistant steel, comprising:

[0007] The molten iron is subjected to KR desulfurization, converter smelting and refining, wherein the argon station temperature is required to be ≥1500°C during the converter smelting process; the refining time is required to be ≥45min during the refining process, and a rare earth alloy is added to the molten steel in an amount of 0.1kg to 1kg per ton of molten steel to obtain refined molten steel; the refined molten steel includes the following chemical components in terms of mass percentage: C: 0.1% to 0.5%, Si: 0 to 0.7%, Mn: 0.8% to 1.6%, P: 0 to 0.04%, S: 0 to 0.02%, Cr: 0.10% to 0.70%, Ni: 0.01% to 0.50%, Mo: 0 to 0.50%, La: 0.005% to 0.05%, Ce: 0.005% to 0.05%, Ti / N ≥3.0, and the rest is iron and other inevitable impurities;

[0008] The refined molten steel is continuously cast and hot-rolled to obtain hot-rolled steel; wherein the superheat of the refined molten steel in the tundish for continuous casting is 10° C. to 45° C.;

[0009] Performing slow cooling treatment on the hot-rolled steel to obtain slow-cooled steel;

[0010] The slowly cooled steel is heat treated to obtain low alloy high toughness 500 hardness grade martensitic wear-resistant steel.

[0011] According to an embodiment of the first aspect of the present application, refining includes LF refining and RH refining.

[0012] According to the embodiment of the first aspect of the present application, the pulling speed during the slab continuous casting process is 0.8m / min to 1.5m / min, and the slab thickness is 230mm to 240mm.

[0013] According to the embodiment of the first aspect of the present application, the rare earth alloy needs to meet the following chemical composition: La, 30% to 40%; Ce, 60% to 70%.

[0014] According to an embodiment of the first aspect of the present application, the hot rolling process includes: heating the continuously cast slab to obtain a continuously cast slab in a heated state; performing rough rolling on the continuously cast slab in a heated state to obtain a rough-rolled slab; performing finish rolling on the rough-rolled slab to obtain a finish-rolled steel; and coiling the finish-rolled steel to obtain a finish-rolled steel coil as a hot-rolled steel.

[0015] According to an embodiment of the first aspect of the present application, the heating temperature of the continuous casting slab for heating treatment is 1150° C. to 1280° C., and the heating time of the continuous casting slab is 120 min to 300 min.

[0016] According to the embodiment of the first aspect of the present application, the continuous casting slab is rough rolled in 5 to 7 passes of a rough rolling mill after heat treatment, and the surface temperature of the rough rolled slab after rough rolling treatment is 1050°C to 1150°C; the surface temperature of the finished steel after finish rolling treatment is 850°C to 950°C, and the coiling temperature for coiling the finished steel is set to 550°C to 700°C.

[0017] According to an embodiment of the first aspect of the present application, the hot-rolled steel is subjected to a slow cooling treatment so that the slow cooling temperature of the hot-rolled steel reaches ≤60°C.

[0018] According to an embodiment of the first aspect of the present application, heat treatment is performed on the slowly cooled steel, comprising:

[0019] The slowly cooled steel is heated to 850°C to 950°C and kept at this temperature for a first period of time, and quenched in water to obtain quenched steel;

[0020] Performing a second tempering treatment at 160° C. to 260° C. on the quenched steel to obtain a tempered steel;

[0021] The tempered steel is air-cooled to obtain low-alloy, high-toughness, 500-hardness martensitic wear-resistant steel.

[0022] According to an embodiment of the first aspect of the present application, the first duration is 20 minutes to 60 minutes.

[0023] According to an embodiment of the first aspect of the present application, the temperature of water used to quench the slowly cooled steel is 10°C to 50°C, and the slowly cooled steel is quenched to the same temperature as the water used for quenching.

[0024] According to an embodiment of the first aspect of the present application, the second duration is 20 minutes to 80 minutes.

[0025] In the second aspect, the present application provides a low-alloy, high-toughness, 500-hardness level martensitic wear-resistant steel, which includes the following chemical components, in mass percentage: C: 0.1%~0.5%, Si: 0~0.7%, Mn: 0.8%~1.6%, P: 0~0.04%, S: 0~0.02%, Cr: 0.10%~0.70%, Ni: 0.01%~0.03%, Mo: 0.002~0.004%, La: 0.005%~0.05%, Ce: 0.005%~0.05%, and the rest are iron and other inevitable impurities, among which Ti / N≥3.0.

[0026] According to the embodiment of the second aspect of the present application, the matrix structure of the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel is a nano-scale martensitic structure, and nano-scale precipitates and high-density dislocation clusters are distributed in the nano-scale martensitic structure. The types of nano-scale precipitates include (Nb x Tiy )C(x+y=1), VC, NbC, TiC, M 2.5 C and M3C (M represents Fe, Mn and Cr elements), the equivalent diameter of the nanoscale precipitated phase is less than 60nm.

[0027] According to the embodiment of the second aspect of the present application, the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel has a low-temperature impact energy of ≥80J at -20°C and a low-temperature impact energy of ≥40J at -60°C.

[0028] According to the embodiment of the second aspect of the present application, the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel has a yield strength of 1100MPa~1500MPa, a tensile strength of 1400MPa~1800MPa, a steel plate hardness HBW≥470, an elongation of 10%~25%, and an impact energy of 100J~120J at -20℃.

[0029] The low-alloy high-toughness 500 hardness level martensitic wear-resistant steel and its preparation method in the embodiment of the present application are as follows: the molten iron is subjected to KR desulfurization, converter smelting and refining, and rare earth alloys are added during the refining process to obtain refined molten steel with the above alloy composition. Rare earth elements can effectively remove harmful impurities such as sulfur and oxygen in the steel, and the content of inclusions in the steel is reduced by forming stable sulfides and oxides. This process not only improves the purity of the steel, but also promotes the formation of crystal nuclei in the steel through rare earth elements, slows down the growth rate of grains, achieves the purpose of refining grains, and optimizes the internal structure of the steel; and directly performs slow cooling and heat treatment on the hot-rolled steel after hot rolling treatment, so as to form a nano-scale martensitic structure in the steel matrix by quenching treatment in heat treatment, and promote (Nb x Ti y )C(x+y=1), VC, NbC, TiC, M 2.5 The precipitation of C and M3C (M represents Fe, Mn and Cr elements) nano-scale carbides produces a precipitation strengthening effect, distributing nano-scale precipitated phases and high-density dislocation clusters in the steel matrix structure, thereby jointly enhancing the strength and toughness of the steel, improving the overall performance of the steel, and producing a low-alloy, high-toughness 500 hardness level martensitic wear-resistant steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0031] Figure 1 It is a flow chart of a method for preparing a low-alloy, high-toughness, 500-hardness grade martensitic wear-resistant steel provided in an embodiment of the present application. DETAILED DESCRIPTION

[0032] The features and exemplary embodiments of various aspects of the present application will be described in detail below. In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, rather than to limit the present application. For those skilled in the art, the present application can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present application by illustrating the examples of the present application.

[0033] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "include..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0034] In order to solve the problems of the prior art, the present invention provides a low alloy high toughness 500 hardness level martensitic wear-resistant steel and a preparation method thereof. The preparation method of the low alloy high toughness 500 hardness level martensitic wear-resistant steel provided in the present invention is first introduced below.

[0035] Figure 1 A schematic flow chart of a method for preparing a low-alloy, high-toughness, 500-hardness martensitic wear-resistant steel provided in one embodiment of the present application is shown.

[0036] like Figure 1 As shown, the preparation method of low alloy high toughness 500 hardness level martensitic wear-resistant steel comprises:

[0037] S1. The molten iron is subjected to KR desulfurization, converter smelting and refining, wherein the argon station temperature is required to be ≥1500°C during the converter smelting process; the refining time is required to be ≥45min during the refining process, and a rare earth alloy is added to the molten steel in an amount of 0.1kg to 1kg per ton of molten steel, and Ti / N is ≥3.0; refined molten steel is obtained; the refined molten steel includes the following chemical components in terms of mass percentage: C: 0.1% to 0.5%, Si: 0 to 0.7%, Mn: 0.8% to 1.6%, P: 0 to 0.04%, S: 0 to 0.02%, Cr: 0.10% to 0.70%, Ni: 0.01% to 0.03%, Mo: 0.002 to 0.004%, La: 0.005% to 0.05%, Ce: 0.005% to 0.05%, and the rest is iron and other inevitable impurities;

[0038] S2, continuously casting and hot rolling the refined molten steel to obtain hot-rolled steel; wherein the superheat of the refined molten steel in the tundish for continuous casting is 10° C. to 45° C.;

[0039] S3, performing slow cooling treatment on the hot-rolled steel to obtain slow cooling steel;

[0040] S4. Heat-treat the slowly cooled steel to obtain low alloy, high toughness, 500 hardness level martensitic wear-resistant steel.

[0041] The preparation method of low-alloy high-toughness 500 hardness level martensitic wear-resistant steel in the embodiment of the present application comprises the following steps: subjecting molten iron to KR desulfurization, converter smelting and refining, and adding rare earth alloys during the refining process to obtain refined molten steel with the above alloy composition. Rare earth elements can effectively remove harmful impurities such as sulfur and oxygen in steel, and reduce the number of inclusions in steel by forming stable sulfides and oxides. This process not only improves the purity of steel, but also promotes the formation of crystal nuclei in steel through rare earth elements, slows down the growth rate of grains, achieves the purpose of grain refinement, and optimizes the internal structure of steel; and by directly performing slow cooling treatment, quenching treatment, and tempering treatment on the steel coil after hot rolling or the steel plate, a nano-scale martensitic structure is formed in the matrix by quenching treatment, and (Nb x Ti y )C(x+y=1), VC, NbC, TiC, M 2.5 The precipitation of C and M3C (M represents Fe, Mn and Cr elements) nano-scale carbides produces a precipitation strengthening effect, distributing nano-scale precipitated phases and high-density dislocation clusters in the steel matrix structure, thereby jointly enhancing the strength and toughness of the steel, improving the overall performance of the steel, and producing a low-alloy, high-toughness 500 hardness level martensitic wear-resistant steel.

[0042] The preparation method of the low alloy high toughness 500 hardness level martensitic wear-resistant steel in the embodiment of the present application makes the production of steel simple, and can use existing production equipment to achieve the production of low alloy high toughness 500 hardness level martensitic wear-resistant steel. Among them, Ti / N ≥ 3.0 can be obtained by measuring the Ti content and N content of the molten steel respectively, and then using Ti / N to calculate.

[0043] It should be noted that in the present application, no additional Ni and Mo are added, and the Ni and Mo in the molten steel are the residual Ni and Mo in the molten steel.

[0044] In the embodiments of the present application, KR desulfurization refers to desulfurization of molten iron using the KR method.

[0045] In some embodiments of the present application, refining includes LF refining and RH refining. RH refining refers to the step of performing RH vacuum refining on the molten steel after LF refining treatment. The superheat range of the tundish is 10°C to 45°C, which means that the temperature of the refined molten steel in the tundish for continuous casting is 10°C to 45°C higher than the temperature of the molten steel obtained by smelting.

[0046] In some embodiments of the present application, the rare earth alloy needs to meet the following chemical composition: La, 30% to 40%; Ce, 60% to 70%.

[0047] In some embodiments of the present application, rare earth alloys are added during RH refining, and the temperature for RH refining with the rare earth alloy added in an argon station needs to be ≥1500°C.

[0048] In the embodiments of the present application, adding rare earth alloys to the molten steel in the refining process can reduce harmful substances such as sulfur and oxygen in the molten steel, and reduce the content of inclusions in the steel by forming stable sulfides and oxides, thereby improving the cleanliness of the molten steel. In addition, adding rare earth alloys in the refining process and utilizing rare earth elements can promote the formation of crystal nuclei in steel and slow down the growth rate of grains, thereby achieving the purpose of grain refinement, optimizing the internal structure of steel, enhancing the strength and toughness of steel, and improving the overall performance of steel. Adding rare earth alloys at a temperature above 1500°C can quickly and fully disperse the rare earth alloys in the molten steel, thereby improving the mechanical properties of low-alloy high-toughness 500 hardness level martensitic wear-resistant steel, and can take into account the hardness, strong plasticity and toughness and cost of wear-resistant steel.

[0049] In some embodiments of the present application, the pulling speed during the slab continuous casting process is 0.8 m / min to 1.5 m / min, and the slab thickness is 230 mm to 240 mm.

[0050] In some embodiments of the present application, the method for preparing low-alloy high-toughness 500 hardness grade martensitic wear-resistant steel further includes: surface cleaning of the continuous casting slab to remove iron oxide scale or other impurities on the surface of the continuous casting slab.

[0051] In some embodiments of the present application, the hot rolling process includes:

[0052] S201, heating the continuous casting slab to obtain a heated continuous casting slab;

[0053] S202, performing rough rolling on the heated continuous casting slab to obtain a rough rolled slab;

[0054] S203, performing finish rolling on the rough-rolled slab to obtain a finish-rolled steel product;

[0055] S204, coiling the finish-rolled steel to obtain a finish-rolled steel coil as a hot-rolled steel.

[0056] In some embodiments of the present application, the heating temperature for the heating treatment of the continuous casting slab is 1150° C. to 1280° C., and the heating time of the continuous casting slab is 120 min to 300 min.

[0057] In some embodiments of the present application, the continuous casting slab is subjected to rough rolling treatment by a 5-7 pass rough rolling mill after the heating treatment, and the surface temperature of the rough rolled slab after the rough rolling treatment is 1050°C to 1150°C; the surface temperature of the finished steel after the finishing rolling treatment is 850°C to 950°C, and the coiling temperature of the finished steel is set to 550°C to 700°C. In the embodiments of the present application, the finished steel coil obtained by coiling can be placed in a storage to cool to room temperature before subsequent processing.

[0058] In some embodiments of the present application, the hot-rolled steel is subjected to a slow cooling treatment so that the slow cooling temperature of the hot-rolled steel reaches ≤60° C., thereby obtaining the slow-cooled steel.

[0059] In the embodiments of the present application, the hot-rolled steel after hot rolling needs to be subjected to slow cooling treatment so that the slow-cooled steel that is slowly cooled to room temperature (≤60°C) can be quenched and tempered. The quenching treatment can be carried out in a heating furnace, and the tempering treatment can be carried out in a tempering furnace.

[0060] In some embodiments of the present application, the slowly cooled steel is subjected to heat treatment, including:

[0061] S401, heating the slowly cooled steel to 850° C. to 950° C. and keeping the temperature for a first period of time, and quenching the steel in water to obtain a quenched steel;

[0062] S402, performing a second tempering treatment at 160° C. to 260° C. on the quenched steel to obtain a tempered steel;

[0063] S403, air-cooling the tempered steel to obtain low-alloy high-toughness 500 hardness grade martensitic wear-resistant steel.

[0064] In the embodiment of the present application, the slowly cooled steel is subjected to a second quenching treatment in a heating furnace. When the furnace temperature of the heating furnace is stable, the slowly cooled steel is sent to the heating furnace and heated to 850°C to 950°C. The slowly cooled steel is taken out of the heating furnace and immediately quenched in water at a water temperature of 10°C to 50°C. The quenching treatment is performed until the temperature of the steel coil or steel plate is the same as the water temperature to obtain quenched steel. The slowly cooled steel is flattened by cross-cutting to form a single steel plate, so that each single steel plate is further quenched and tempered.

[0065] In some embodiments, the first time duration for heating the slowly cooled steel is 20 minutes to 60 minutes.

[0066] In some embodiments of the present application, the temperature of water used to quench the slowly cooled steel is 10° C. to 50° C., and the slowly cooled steel is quenched to the same temperature as the water used for quenching.

[0067] In some embodiments of the present application, the second duration is 20 minutes to 80 minutes.

[0068] In the embodiment of the present application, the quenched steel material that has completed the quenching treatment is sent to the tempering furnace, and the tempering furnace is heated to 160°C to 260°C. After the furnace temperature of the tempering furnace is stabilized, the quenched steel material is immediately placed in the tempering furnace. The tempering treatment time in the tempering furnace is 20 minutes to 80 minutes. After the tempering time is reached, the steel coil or steel plate is immediately taken out of the furnace for air cooling. The steel material treated by the tempering process is cooled by air, and the cooling speed is relatively slow, which can stably control the internal stress of the steel plate.

[0069] In the second aspect, the present application provides a low-alloy, high-toughness, 500-hardness level martensitic wear-resistant steel, which includes the following chemical components, in mass percentage: C: 0.1%~0.5%, Si: 0~0.7%, Mn: 0.8%~1.6%, P: 0~0.04%, S: 0~0.02%, Cr: 0.10%~0.70%, Ni: 0.01%~0.03%, Mo: 0.002~0.004%, La: 0.005%~0.05%, Ce: 0.005%~0.05%, Ti / N≥3.0, and the rest is iron and other inevitable impurities.

[0070] In some embodiments, the matrix structure of the low alloy high toughness 500 hardness level martensitic wear-resistant steel is nano-martensite, and nano-martensite structure is distributed with nano-precipitated phases and high-density dislocation clusters, and the types of nano-precipitated phases include (Nb xTi y )C(x+y=1), VC, NbC, TiC, M 2.5 C and M3C (M represents Fe, Mn and Cr elements), the equivalent diameter of the nanoscale precipitated phase is less than 60nm.

[0071] In some embodiments of the present application, the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel has a low-temperature impact energy of ≥80J at -20°C and a low-temperature impact energy of ≥40J at -60°C.

[0072] In some embodiments of the present application, the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel has a yield strength of 1100MPa~1500MPa, a tensile strength of 1400MPa~1800MPa, a steel plate hardness HBW≥470, an elongation of 10%~25%, and an impact energy of 100J~120J at -20℃.

[0073] The technical solution of the present application is further illustrated below through specific embodiments and comparative examples.

[0074] Example 1

[0075] This embodiment produces a low-alloy, high-toughness, 500-hardness level martensitic wear-resistant steel product NM500P through the Liangang 210 converter smelter-2250 hot rolling plate plant-heat treatment plant production line, with required yield strength of 1100MPa~1500MPa, tensile strength of 1400MPa~1800MPa, steel plate hardness HBW≥470, elongation of 10%~25%, and impact energy of 100J~120J at -20℃.

[0076] First, a batch of NM500P was trial-produced in the 210 converter smelter, producing 200 tons of molten steel and 8 continuous casting slabs. The preparation method of NM500P includes:

[0077] S1. The molten iron of NM500P is subjected to KR desulfurization, converter smelting and refining, wherein the argon station temperature is 1537°C during the converter smelting process; during the refining process, the refining time is 50 minutes, and 50 kg of rare earth alloy is added to the molten steel in an amount of 0.24 kg per ton of molten steel to obtain refined molten steel; in terms of mass percentage, the refined molten steel includes the following chemical components: C: 0.26%, Si: 0.16%, Mn: 1.1%, P: 0.008%, S: 0.001%, Cr: 0.28%, Ni: 0.02%, Mo: 0.002%, La: 0.01%, Ce: 0.015%, Ti / N ≥ 3.0, and the rest is iron and other inevitable impurities;

[0078] S2. The refined molten steel is continuously cast and hot rolled to obtain hot rolled steel; wherein the superheat of the refined molten steel in the tundish for continuous casting is 15° C.; the casting speed of the continuous casting is 1.1 m / min, the thickness of the continuous casting slab is 230 mm, and the width is 2000 mm. The composition of the steel slab obtained by continuous casting is shown in Table 1 below:

[0079] Table 1 NM500P product composition (wt.%)

[0080]

[0081] Among them, after receiving the continuous casting slab, the 2250 hot rolling mill slowly cools the continuous casting slab in the finished product warehouse for 16 hours to 600℃, and then hot rolls the continuous casting slab, including:

[0082] S201, performing a heating treatment on the continuous casting slab, including loading the slowly cooled continuous casting slab into a heating furnace, setting the soaking section of the heating furnace to a temperature of 1240° C., and heating the continuous casting slab in the heating furnace for a total time of 210 min, to obtain a heated continuous casting slab;

[0083] S202, performing rough rolling treatment on the heated continuous casting slab, including performing rough rolling treatment on the heated continuous casting slab through a 7-stand rough rolling mill for 7 passes to obtain a rough rolled slab, wherein the surface temperature of the rough rolled slab is 1100° C.;

[0084] S203, performing finish rolling on the rough-rolled slab to obtain a finish-rolled steel product, wherein the surface temperature of the finish-rolled steel product is 900° C.;

[0085] S204, cooling the finished rolled steel by a laminar cooling process, and coiling the cooled finished rolled steel with an average coiling temperature of 650° C. to obtain a finished rolled steel coil as a hot rolled steel.

[0086] S3. Send the finished rolled steel coils to the finished product warehouse for packaging and printing, and then put them into the warehouse for slow cooling to room temperature 30℃.

[0087] S4. After the heat treatment plant's cross-cutting line receives the finished rolled steel coils that have been cooled to room temperature, the finished rolled steel coils that have been cooled to room temperature are unrolled as required, and the unrolled NM500P product is heated to 900°C for 30 minutes, and then quenched to obtain quenched steel; the quenched steel is tempered at 220°C, and the tempering and insulation time is 40 minutes. After tempering, the steel plate is slowly cooled on a cooling bed, and packaged and printed after cooling to room temperature.

[0088] The mechanical properties of the NM500P product produced in the embodiment are tested, as shown in Table 2 below. It can be seen that the sample produced in this embodiment fully meets the product requirements.

[0089] Table 2 Mechanical properties of NM500P products

[0090]

[0091] According to the mechanical property test data in Table 2, the NM500P product prepared in the embodiment can still maintain high impact toughness in a low temperature environment, and has high impact resistance and wear resistance.

[0092] Example 2

[0093] The preparation process of the low alloy high toughness 500 hardness level martensitic wear-resistant steel product of this embodiment is the same as that of embodiment 1, except that the refined molten steel includes the following chemical components: C: 0.26%, Si: 0.16%, Mn: 1.1%, P: 0.008%, S: 0.001%, Cr: 0.28%, Ni: 0.03%, Mo: 0.002%, La: 0.005%, Ce: 0.0075%, Ti / N ≥ 3.0, and the rest is iron and other inevitable impurities. In this embodiment, the addition amount of rare earth alloy in the refining process is 25kg. The properties of the low alloy high toughness 500 hardness level martensitic wear-resistant steel product obtained are shown in Table 3 below:

[0094] Table 3 Mechanical properties of NM500P products

[0095]

[0096] Example 3

[0097] The preparation process of the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel product in this embodiment is the same as that in Example 1, except that the refined molten steel includes the following chemical components: C: 0.26%, Si: 0.16%, Mn: 1.1%, P: 0.008%, S: 0.001%, Cr: 0.28%, Ni: 0.02%, Mo: 0.003%, La: 0.02%, Ce: 0.03%, Ti / N ≥ 3.0, and the rest are iron and other inevitable impurities. In this embodiment, the addition amount of rare earth alloy in the refining process is 100kg, and the properties of the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel product obtained are shown in Table 4 below.

[0098] Table 4 Mechanical properties of NM500P products

[0099]

[0100] Comparative Example 1

[0101] This comparative example provides a 500 hardness level martensitic wear-resistant steel product, and its preparation method is the same as that of Example 1, except that the rare earth alloy in the same amount as that of Example 1 of the present application is not added in the refining process. The properties of the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel product prepared are shown in Table 5 below:

[0102] Table 5 Mechanical properties of NM500P products

[0103]

[0104] Comparative Example 2

[0105] This comparative example provides a 500 hardness level martensitic wear-resistant steel product, and its preparation method is the same as that of Example 1, and the difference from Example 1 is that in the refining process of Comparative Example 2, an alloy containing manganese, chromium, nickel, and molybdenum is added, C: 0.26%, Si: 0.16%, Mn: 1.1%, P: 0.008%, S: 0.001%, Cr: 0.28%, Ni: 0.45%, Mo: 0.50%, Ti / N ≥ 3.0. The properties of the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel product obtained are shown in Table 6 below:

[0106] Table 6 Mechanical properties of NM500P products

[0107]

[0108] Comparative Example 3

[0109] The preparation process of the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel product in this comparative example is the same as that in Example 1, except that the refined molten steel includes the following chemical components: C: 0.26%, Si: 0.16%, Mn: 1.1%, P: 0.008%, S: 0.001%, Cr: 0.28%, Ni: 0.02%, Mo: 0.003%, La: 0.002%, Ce: 0.003%, Ti / N ≥ 3.0, and the rest are iron and other inevitable impurities. The addition amount of rare earth alloy in this embodiment is 10 kg. The properties of the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel product obtained are shown in Table 7 below.

[0110] Table 7 Mechanical properties of NM500P products

[0111]

[0112] Comparison of Examples 1-3 and Comparative Examples 1-3 shows that:

[0113] Examples 1-3 of the present application contain low-alloy, high-toughness, 500-hardness grade martensitic wear-resistant steel that meets the specified La and Ce contents of the present application. The hardness, strength, plasticity, toughness and low cost of the wear-resistant steel are relatively good and can be taken into account.

[0114] Comparative Example 1 does not add the same amount of rare earth alloy as in Example 1 of the present application, and the 500 hardness level martensitic wear-resistant steel is made. Its impact energy at -20°C and -60°C is significantly lower than that of the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel in Examples 1-3 of the present application, indicating that the addition of La and Ce elements is necessary to make the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel take into account the hardness, strong plasticity and toughness, and cost of the wear-resistant steel.

[0115] In the 500 hardness level martensitic wear-resistant steel of Comparative Example 2, an alloy containing manganese, chromium, nickel and molybdenum is added during the refining process, but its cost is relatively high. The comprehensive cost of 0.5% Mo and 0.5% Ni per ton of steel is about 2,700 yuan, while the cost of 0.01% rare earth elements in this application is about 800 yuan. The cost of low-alloy high-toughness 500 hardness level martensitic wear-resistant steel has been significantly reduced by more than 3 times through technical improvements.

[0116] The 500 hardness level martensitic wear-resistant steel of Comparative Example 3 is added with 500 hardness level martensitic wear-resistant steel containing rare earth alloy in the refining process, but the added La and Ce contents do not meet the requirements of the present application, and its impact energy resistance at -20°C and -60°C is significantly lower than that of the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel of Examples 1-3 of the present application, indicating that adding corresponding contents of La and Ce elements is necessary to make the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel take into account the hardness, strong plasticity toughness and cost of the wear-resistant steel.

[0117] The above is only a specific implementation method of the present application. Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working process described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here. It should be understood that the protection scope of the present application is not limited to this. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application.

Claims

1. A method for preparing low-alloy high-toughness 500-hardness martensitic wear-resistant steel, characterized in that: include: The molten iron is subjected to KR desulfurization, converter smelting and refining, wherein the argon station temperature is required to be ≥1500°C during the converter smelting process; the refining time is required to be ≥45min during the refining process, and a rare earth alloy is added to the molten steel in an amount of 0.1kg to 1kg per ton of molten steel to obtain refined molten steel; the refined molten steel includes the following chemical components in terms of mass percentage: C: 0.1% to 0.5%, Si: 0 to 0.7%, Mn: 0.8% to 1.6%, P: 0 to 0.04%, S: 0 to 0.02%, Cr: 0.10% to 0.70%, Ni: 0.01% to 0.03%, Mo: 0.002 to 0.004%, La: 0.005% to 0.05%, Ce: 0.005% to 0.05%, Ti / N ≥3.0, and the rest is iron and other inevitable impurities; The refined molten steel is continuously cast and hot rolled to obtain hot-rolled steel; wherein the superheat of the refined molten steel in the tundish for continuous casting is 10° C. to 45° C.; Performing a slow cooling treatment on the hot-rolled steel to obtain a slow-cooled steel; The slowly cooled steel is heat treated to obtain low alloy high toughness 500 hardness grade martensitic wear-resistant steel.

2. The preparation method according to claim 1, characterized in that: The rare earth alloy needs to meet the following chemical composition: La, 30% to 40%; Ce, 60% to 70%.

3. The preparation method according to claim 1, characterized in that: The hot rolling process comprises: Heating the continuously cast slab obtained by continuous casting to obtain a continuously cast slab in a heated state; Performing rough rolling on the heated continuous casting slab to obtain a rough rolled slab; Performing finish rolling on the rough-rolled slab to obtain a finished steel product; The finished rolled steel is coiled to obtain a finished rolled steel coil as a hot rolled steel.

4. The preparation method according to claim 3, characterized in that: After the continuous casting slab is heated, it is rough rolled in a rough rolling mill for 5 to 7 passes, and the surface temperature of the rough rolled slab after the rough rolling treatment is 1050°C to 1150°C; the temperature of the finished steel after the finish rolling treatment is 850°C to 950°C, and the coiling temperature of the finished steel is set to 550°C to 700°C.

5. The preparation method according to claim 1, characterized in that: The heating temperature of the continuous casting slab for heating treatment is 1150° C. to 1280° C., and the heating time for obtaining the continuous casting slab is 120 min to 300 min.

6. The preparation method according to claim 1, characterized in that: Meet at least one of the following requirements: Performing a slow cooling treatment on the hot-rolled steel material so that the slow cooling temperature of the hot-rolled steel material reaches ≤60°C; The temperature of the water used to quench the slowly cooled steel material is 10° C. to 50° C., and the slowly cooled steel material is quenched to the same temperature as the water used for quenching.

7. The preparation method according to claim 1, characterized in that: The step of heat treating the slowly cooled steel comprises: The slowly cooled steel is heated to 850° C. to 950° C. and kept warm for a first time, and quenched in water to obtain a quenched steel, wherein the first time is 20 min to 60 min; Performing a tempering treatment on the quenched steel at 160° C. to 260° C. for a second time to obtain a tempered steel, wherein the second time is 20 min to 80 min; The tempered steel is air-cooled to obtain low-alloy high-toughness 500-hardness martensitic wear-resistant steel.

8. A low alloy high toughness 500 hardness level martensitic wear-resistant steel, characterized in that: The low alloy high toughness 500 hardness martensitic wear-resistant steel is prepared according to the preparation method of any one of claims 1 to 7; the low alloy high toughness 500 hardness martensitic wear-resistant steel comprises the following chemical components in terms of mass percentage: C: 0.1%~0.5%, Si: 0~0.7%, Mn: 0.8%~1.6%, P: 0~0.04%, S: 0~0.02%, Cr: 0.10%~0.70%, Ni: 0.01%~0.03%, Mo: 0.002~0.004%, La: 0.005%~0.05%, Ce: 0.005%~0.05%, the rest are iron and other inevitable impurities, among which Ti / N ≥ 3.

0.

9. The wear-resistant steel according to claim 8, characterized in that: The matrix structure of the low-alloy high-toughness 500 hardness level martensitic wear-resistant steel is a nano-scale martensitic structure, and nano-scale precipitates and high-density dislocation clusters are distributed in the nano-scale martensitic structure; the types of the nano-scale precipitates include (Nb x Ti y )C(x+y=1), VC, NbC, TiC, M 2.5 C and M3C, M represents Fe, Mn and Cr elements, and the equivalent diameter of the nanoscale precipitated phase is less than 60nm.

10. The wear-resistant steel according to claim 8, characterized in that: The low-alloy high-toughness 500-hardness martensitic wear-resistant steel has a yield strength of 1100MPa-1500MPa, a tensile strength of 1400MPa-1800MPa, a steel plate hardness HBW≥470, an elongation of 10%-25%, and an impact energy of 100J-120J at -20°C.

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