Quenched and tempered high-strength steel and preparation method thereof

Abstract

The invention discloses quenched and tempered high-strength steel and a preparation method thereof, and belongs to the technical field of metal materials, and the quenched and tempered high-strength steel comprises the following element raw materials in percentage by weight: 0.26%-0.30% of carbon, 0.80%-0.90% of silicon, 1.7%-1.8% of manganese, 0.03%-0.05% of niobium, 0.03%-0.04% of aluminum, 0.01%-0.02% of titanium, 0.2%-0.3% of molybdenum, phosphorus, sulfur and the balance of iron. Wherein the total content of phosphorus and sulfur does not exceed 0.02%. The invention also discloses a preparation method of the high-strength steel, which comprises the following steps: a smelting step: proportioning all the element raw materials according to the proportion, heating metal in a smelting furnace to a molten state, putting the proportioned raw materials into the smelting furnace, and fully and uniformly mixing to obtain high-temperature molten steel; a casting step; the molten high-temperature molten steel is cast into a preset shape, and cast steel is obtained; and a heat treatment step: carrying out thermal refining on the cast steel to obtain the high-strength steel. According to the high-strength steel disclosed by the invention, through accurate chemical component design and an optimized hardening and tempering process, the obtained high-strength steel has good toughness while keeping high strength.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal materials, and in particular relates to a quenched and tempered high-strength steel and a preparation method thereof. Background Art

[0002] In the field of metal materials, high-strength steel is widely used in various industries, including automotive, aerospace, bridges, construction, and machinery manufacturing, due to its excellent mechanical properties. However, the pursuit of high strength in traditional high-strength steel often comes with a decrease in electrical conductivity and increased processing difficulty, which to some extent limits its scope of application.

[0003] At present, the preparation of high-strength steel mainly depends on precise chemical composition design and complex heat treatment process. For the high-strength steel involved in the present invention, its composition design (such as the content range of elements such as C, Si, Mn, Nb, P, S, Al, Ti, Mo, etc.) is intended to optimize the microstructure of the steel by utilizing the interaction between the elements through microalloying technology, thereby improving the strength and toughness of the steel. However, in the actual production process, how to ensure that these elements are evenly distributed in the steel to avoid segregation and the formation of harmful phases is a technical problem that needs to be solved urgently. In addition, the heat treatment process has a vital influence on the mechanical properties of high-strength steel. Traditional quenching and tempering processes, such as quenching and tempering, can significantly improve the strength and hardness of steel, but may also lead to a decrease in material toughness and deterioration of processing performance. Therefore, how to formulate a suitable heat treatment system to achieve the best balance between the strength, toughness and processing performance of high-strength steel is the focus of researchers and engineers.

[0004] Prior to the present application, although a variety of high-strength steels have been developed, they often find it difficult to achieve both good electrical conductivity and processing performance while meeting specific strength requirements. Especially in some applications that require high comprehensive material performance, such as power transmission, electronic packaging and other fields, the performance of traditional high-strength steels is still insufficient. In summary, the development of a new type of high-strength steel that has both high strength, high conductivity and good processing performance is of great significance for broadening the application scope of high-strength steel and promoting technological progress in related industries. Therefore, the present invention proposes a high-strength steel with a specific chemical composition and tempering process, which aims to achieve a comprehensive improvement in its mechanical properties and processing performance by optimizing the microstructure and heat treatment process of the steel. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a quenched and tempered high-strength steel and a preparation method thereof.

[0006] The technical solution adopted to solve the above technical problems is: a quenched and tempered high-strength steel, the high-strength steel comprising the following elemental raw materials in percentage by weight:

[0007] Carbon 0.26%-0.30%, silicon 0.80%-0.90%, manganese 1.7%-1.8%, niobium 0.03%-0.05%, aluminum 0.03%-0.04%, titanium 0.01%-0.02%, molybdenum 0.2%-0.3%, phosphorus and sulfur, and the rest is iron, of which the total content of phosphorus and sulfur does not exceed 0.02%.

[0008] Through the above technical solution, the composition and proportion of each element of the raw materials can be precisely controlled to achieve improved strength, toughness and good processing performance of the steel.

[0009] Furthermore, the high-strength steel is subjected to quenching and tempering treatment in the following manner:

[0010] Firstly heat to the temperature range of 1080-1100℃ for rolling;

[0011] Then cool it down to 900-915℃ for quenching, so that the internal structure of the steel is transformed into martensite;

[0012] Then tempering treatment is carried out in the temperature range of 240-245℃ to eliminate quenching stress.

[0013] The above technical solution enables high-strength steel to exhibit exceptional mechanical properties: tensile strength reaching 1440 MPa, yield strength reaching 1160 MPa, elongation exceeding 14%, stable hardness ≥ 460 HB, and impact energy exceeding 45 J at -20°C. These properties make it an ideal material for structural engineering projects such as high-rise buildings and bridges, significantly improving the safety and durability of structures.

[0014] Furthermore, the hardness of the high-strength steel after quenching and tempering is controlled at 460-480 HB.

[0015] Through the above technical solution, the hardness is controlled between 460-480HB, which not only ensures that the steel has sufficient strength, but also facilitates subsequent mechanical processing and forming, and improves the flexibility of material use and production efficiency.

[0016] A method for preparing quenched and tempered high-strength steel comprises the following steps:

[0017] Melting step: The raw materials are mixed in proportion, and the metal is heated in a melting furnace until it is molten. The mixed raw materials are then added to the melting furnace and mixed thoroughly to obtain high-temperature molten steel. The raw materials are as follows in terms of weight percentage:

[0018] Carbon 0.26%-0.30%, silicon 0.80%-0.90%, manganese 1.7%-1.8%, niobium 0.03%-0.05%, aluminum 0.03%-0.04%, titanium 0.01%-0.02%, molybdenum 0.2%-0.3%, phosphorus, sulfur, and the rest is iron, of which the total content of phosphorus and sulfur does not exceed 0.02%;

[0019] Casting step: casting the molten high-temperature steel liquid into a predetermined shape to obtain cast steel;

[0020] Heat treatment steps: The cast steel is subjected to tempering treatment to obtain high-strength steel. The specific treatment contents include rolling, quenching and tempering.

[0021] Through the above technical solution, through precise chemical composition design and optimized tempering process, the high-strength steel obtained not only maintains high strength (tensile strength ≥1400MPa, yield strength ≥1150MPa), but also has good toughness (elongation ≥12%, impact energy ≥40J), meeting the use requirements under various extreme working conditions.

[0022] Furthermore, during the smelting step, the ratio of gases in the smelting furnace is adjusted to form a neutral atmosphere.

[0023] Through the above technical solution, the atmosphere in the furnace is controlled to prevent oxidation of the molten steel and ensure that the raw materials of each element are fully dissolved and evenly distributed.

[0024] Furthermore, in the casting step, the casting temperature is controlled within the range of 1500-1600°C.

[0025] Through the above technical solution, the casting temperature is controlled to obtain steel with the desired microstructure and properties.

[0026] Furthermore, in the casting step, the casting speed is controlled within the range of 0.8-2 m / min.

[0027] By means of the above technical solution, the casting speed is controlled, and steel with desired microstructure and properties is further obtained.

[0028] Through the above technical solution, the high-strength steel produced can meet different usage requirements.

[0029] Furthermore, in the smelting step, when the raw materials are put into the smelting furnace for mixing, a vibration device is used to vibrate the smelting furnace.

[0030] Through the above technical solution, the vibration device generates vibrations on the raw materials of each element in the smelting furnace, thereby improving the degree of fine grain strengthening during the fine grain strengthening of the raw materials of each element.

[0031] Furthermore, in the smelting step, the smelting time is controlled within 30-50 minutes.

[0032] Through the above technical solution, the smelting time is controlled to achieve the purpose of fully dissolving and evenly distributing each element of the raw material.

[0033] The beneficial effects of the present invention are as follows:

[0034] 1. In the present invention, the strength, toughness and processing properties of steel are improved through precise ratio of elemental raw materials;

[0035] 2. In the present invention, through precise chemical composition design and optimized quenching and tempering process, the high-strength steel obtained not only maintains high strength (tensile strength ≥1400MPa, yield strength ≥1150MPa) but also has good toughness (elongation ≥12%, impact energy ≥40J), meeting the requirements of use under various extreme working conditions;

[0036] 3. In the present invention, the hardness of the high-strength steel after quenching and tempering is controlled between 460-480HB, which not only ensures sufficient strength but also facilitates subsequent mechanical processing and forming, thereby improving the flexibility of material use and production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a metallographic structure diagram of the high-strength steel obtained in Example 1 of the present invention;

[0038] Figure 2 3 is the metallographic structure diagram of the high-strength steel obtained in Example 4 of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] Explanation of terms

[0041] 1. Solid solution strengthening is a method of increasing the strength and hardness of materials by adding alloying elements to pure metals. Its basic principles and mechanisms are as follows:

[0042] Lattice distortion: When solute atoms are incorporated into the base metal lattice, the size difference between the solute atoms and the solvent atoms causes lattice distortion. This distortion induces local stress fields that hinder the movement of dislocations.

[0043] Dislocation movement is hindered: Dislocations are defects in crystals whose movement can cause plastic deformation of the material. Solid solution strengthening increases the resistance to dislocation movement through the interaction between solute atoms and dislocations, making slip difficult and thus improving the strength and hardness of the material.

[0044] Stress field interaction: The local stress field induced by solute atoms interacts with dislocations, attracting or repelling them and further hindering their motion. This interaction, called the scale effect, relieves the tensile or compressive strain in the lattice, placing the dislocations in a lower energy state.

[0045] Types: Solid solution strengthening can be categorized as substitutional solid solution and interstitial solid solution. Substitutional solid solution occurs when solute atoms replace solvent atoms, while interstitial solid solution occurs when solute atoms enter the interstitial spaces between solvent atoms. The solid solution strengthening effect of interstitial atoms is generally more significant than that of substitutional atoms, but due to their limited solid solubility, the actual strengthening effect is also limited.

[0046] 2. Grain refinement strengthening is a method of improving the strength and hardness of metal materials by refining their grain size. The following are the basic principles and mechanisms of grain refinement strengthening:

[0047] Grain boundaries hinder dislocation slip: Grain refinement strengthens materials primarily through the retardation effect of grain boundaries. In polycrystalline materials, dislocation movement must overcome the resistance of grain boundaries. Due to the different orientations of the grains on either side of the grain boundary, slipping dislocations cannot directly cross the grain boundary into adjacent grains. Only after a large number of dislocations accumulate at the grain boundary, causing stress concentration, can the movement of existing dislocations in adjacent grains be stimulated to slip.

[0048] Hall-Page relationship: According to the Hall-Page relationship, the smaller the average diameter of the grains, the higher the material strength.

[0049] Grain refinement methods: During the crystallization process, grain refinement can be achieved by increasing the nucleation rate through increasing undercooling, modification, vibration, and stirring. For cold-deformed metals, grain refinement can be achieved by controlling the degree of deformation and annealing temperature. Heat treatments such as normalizing and annealing can also refine grains. Adding alloying elements to steel forms new phases, thereby inhibiting grain growth.

[0050] Advantages of fine-grain strengthening: Fine-grain strengthening not only increases the strength and hardness of materials, but also improves their plasticity and toughness. This is because when fine-grained metals are subjected to stress, plastic deformation can be dispersed across more grains, resulting in more uniform deformation. Furthermore, each grain has fewer dislocations, reducing the chance of cracking due to stress concentration.

[0051] 3. Precipitation strengthening is a method of increasing the strength and hardness of materials by forming second phase particles in the alloy. The following are the basic principles and mechanisms of precipitation strengthening:

[0052] Precipitation Formation: Precipitation strengthening occurs by introducing second-phase particles into the alloy matrix. Interfacial energy exists between these particles and the matrix, resulting in a strengthening effect. In alloys, controlled heat treatment processes cause certain components to precipitate as second phases. These second-phase particles can be carbides, nitrides, or intermetallic compounds.

[0053] Interaction between precipitates and dislocations: Precipitated particles effectively enhance the alloy's strength by pinning dislocations and grain boundaries. Dislocations interact with these particles during motion, increasing resistance to dislocation motion and thereby improving the material's yield strength and hardness.

[0054] Application of precipitation strengthening: Precipitation strengthening plays a very important role in the production of metal materials such as microalloyed steel. For example, microalloyed steel is strengthened by the dissolution-precipitation behavior of carbon and nitrides. The carbon, nitrides, intermetallic compounds and metastable intermediate phases distributed in the matrix act as second-phase particles. The interaction between the boundaries and moving dislocations leads to an increase in the flow stress and yield strength of the steel. In high-temperature alloys, elements such as aluminum and titanium can form intermetallic compounds (such as NiAl, Ni3Ti, etc.) with nickel at high temperatures. These compounds precipitate as second-phase particles and are dispersed in the matrix. By pinning dislocations and grain boundaries, they effectively improve the high-temperature strength of the alloy.

[0055] Advantages of precipitation strengthening: Precipitation strengthening can not only significantly increase the strength and hardness of the material, but also improve the corrosion resistance and wear resistance of the material. The presence of precipitation phase can increase the hardness of the alloy surface and improve its ability to resist wear.

[0056] The present invention provides a quenched and tempered high-strength steel, which includes the following elemental raw materials in percentage by weight:

[0057] Carbon 0.26%-0.30%, silicon 0.80%-0.90%, manganese 1.7%-1.8%, niobium 0.03%-0.05%, aluminum 0.03%-0.04%, titanium 0.01%-0.02%, molybdenum 0.2%-0.3%, phosphorus and sulfur, and the rest is iron, of which the total content of phosphorus and sulfur does not exceed 0.02%.

[0058] Example 1:

[0059] This embodiment provides a method for preparing quenched and tempered high-strength steel, comprising the following steps:

[0060] Melting step: The raw materials are mixed in proportion, and then the raw metals are heated in a melting furnace until they are molten. The mixed raw materials are then added to the melting furnace and mixed thoroughly to obtain high-temperature molten steel. The raw materials are as follows in terms of weight percentage:

[0061] Carbon 0.28%, silicon 0.85%, manganese 1.75%, niobium 0.04%, aluminum 0.035%, titanium 0.01%, molybdenum 0.27%, phosphorus, sulfur, and the remainder is iron, wherein the total content of phosphorus and sulfur does not exceed 0.02%. Of course, some unavoidable impurities may be present. In addition, the smelting furnace in this embodiment can be a blast furnace or a vacuum induction furnace;

[0062] In the smelting step, the ratio of gases in the smelting furnace is adjusted to form a neutral atmosphere. The atmosphere in the furnace is controlled to prevent oxidation of the molten steel and to ensure that the elements are fully dissolved and evenly distributed. During the smelting process, the ratio of gases in the smelting furnace is adjusted to form a neutral atmosphere. The atmosphere in the furnace is controlled to prevent oxidation of the molten steel and to ensure that the elements are fully dissolved and evenly distributed. In addition, when the elemental raw materials are added to the smelting furnace for mixing, a vibration device is used to vibrate the smelting furnace. The vibration device vibrates the elemental raw materials in the smelting furnace, and then when the elemental raw materials are refined, the degree of refinement can be improved. The smelting time is controlled within 30-50 minutes. The smelting time is controlled to achieve the purpose of fully dissolving and evenly distributing the elemental raw materials. After smelting, the elemental raw materials go through the solid solution strengthening stage, the fine grain strengthening stage and the precipitation strengthening stage to improve the strength and toughness of the steel.

[0063] Casting step: The molten high-temperature steel liquid is cast into a predetermined shape to obtain the cast steel. The casting temperature is controlled within the range of 1500-1600°C and the casting speed is controlled within the range of 0.8-2 m / min. By controlling the casting temperature and casting speed, the steel with the desired microstructure and properties can be obtained.

[0064] Heat treatment steps: The cast steel is tempered to obtain high-strength steel. The specific treatment contents include rolling, quenching and tempering, that is, first heating to 1095℃ for rolling; then cooling to 9915℃ for quenching to transform the internal structure of the steel into martensite; then tempering at 245℃ to eliminate quenching stress. This tempering process aims to obtain high-hardness martensitic structure through quenching, and then adjust the structure state through tempering, eliminate internal stress, and improve the toughness and comprehensive mechanical properties of the steel. The hardness is controlled between 460-480HB, which not only ensures that the steel has sufficient strength, but also facilitates subsequent mechanical processing and forming, improving the flexibility of material use and production efficiency.

[0065] This steel exhibits exceptional mechanical properties: a tensile strength of up to 1440 MPa, a yield strength of 1160 MPa, an elongation exceeding 14%, a stable hardness of ≥460 HB, and an impact energy exceeding 45 J at -20°C. These properties make it an ideal material for structural engineering projects such as high-rise buildings and bridges, significantly enhancing the safety and durability of these structures.

[0066] Example 2:

[0067] This embodiment provides a method for preparing quenched and tempered high-strength steel, comprising the following steps:

[0068] Melting step: The raw materials are mixed in proportion, and then the raw metals are heated in a melting furnace until they are molten. The mixed raw materials are then added to the melting furnace and mixed thoroughly to obtain high-temperature molten steel. The raw materials are as follows in terms of weight percentage:

[0069] Carbon 0.28%, silicon 0.85%, manganese 1.75%, niobium 0.04%, aluminum 0.035%, titanium 0.015%, molybdenum 0.27%, phosphorus, sulfur, and the remainder is iron, wherein the total content of phosphorus and sulfur does not exceed 0.02%. Of course, some unavoidable impurities may be present. In addition, the smelting furnace in this embodiment can be a blast furnace or a vacuum induction furnace;

[0070] In the smelting step, the ratio of gases in the smelting furnace is adjusted to form a neutral atmosphere. The atmosphere in the furnace is controlled to prevent oxidation of the molten steel and to ensure that the elements are fully dissolved and evenly distributed. During the smelting process, the ratio of gases in the smelting furnace is adjusted to form a neutral atmosphere. The atmosphere in the furnace is controlled to prevent oxidation of the molten steel and to ensure that the elements are fully dissolved and evenly distributed. In addition, when the elemental raw materials are added to the smelting furnace for mixing, a vibration device is used to vibrate the smelting furnace. The vibration device vibrates the elemental raw materials in the smelting furnace, and then when the elemental raw materials are refined, the degree of refinement can be improved. The smelting time is controlled within 30-50 minutes. The smelting time is controlled to achieve the purpose of fully dissolving and evenly distributing the elemental raw materials. After smelting, the elemental raw materials go through the solid solution strengthening stage, the fine grain strengthening stage and the precipitation strengthening stage to improve the strength and toughness of the steel.

[0071] Casting step: The molten high-temperature steel liquid is cast into a predetermined shape to obtain the cast steel. The casting temperature is controlled within the range of 1500-1600°C and the casting speed is controlled within the range of 0.8-2 m / min. By controlling the casting temperature and casting speed, the steel with the desired microstructure and properties can be obtained.

[0072] Heat treatment steps: The cast steel undergoes quenching and tempering to produce high-strength steel. The specific processes include rolling, quenching, and tempering. The steel is first heated to 1095°C for rolling; then cooled to 910°C for quenching to transform the internal structure of the steel into martensite; and then tempered at 243°C to eliminate quenching stresses. This quenching and tempering process aims to achieve a high-hardness martensite structure through quenching. Tempering then adjusts the structure, eliminates internal stresses, and improves the steel's toughness and overall mechanical properties. This steel not only achieves a tensile strength of 1480 MPa and a yield strength exceeding 1200 MPa, but also maintains an elongation of ≥13% and a hardness of ≥472 HB. Furthermore, its impact energy at -20°C is not less than 42 J. These excellent properties make it an ideal choice for key components such as automotive bodies and chassis, contributing to both lightweighting and improved safety.

[0073] Example 3:

[0074] This embodiment provides a method for preparing quenched and tempered high-strength steel, comprising the following steps:

[0075] Melting step: The raw materials are mixed in proportion, and then the raw metals are heated in a melting furnace until they are molten. The mixed raw materials are then added to the melting furnace and mixed thoroughly to obtain high-temperature molten steel. The raw materials are as follows in terms of weight percentage:

[0076] Carbon 0.26%, silicon 0.9%, manganese 1.72%, niobium 0.03%, aluminum 0.03%, titanium 0.02%, molybdenum 0.20%, phosphorus, sulfur, and the remainder is iron, wherein the total content of phosphorus and sulfur does not exceed 0.02%. Of course, some unavoidable impurities may be present. In addition, the smelting furnace in this embodiment can be a blast furnace or a vacuum induction furnace;

[0077] In the smelting step, the ratio of gases in the smelting furnace is adjusted to form a neutral atmosphere. The atmosphere in the furnace is controlled to prevent oxidation of the molten steel and to ensure that the elements are fully dissolved and evenly distributed. During the smelting process, the ratio of gases in the smelting furnace is adjusted to form a neutral atmosphere. The atmosphere in the furnace is controlled to prevent oxidation of the molten steel and to ensure that the elements are fully dissolved and evenly distributed. In addition, when the elemental raw materials are added to the smelting furnace for mixing, a vibration device is used to vibrate the smelting furnace. The vibration device vibrates the elemental raw materials in the smelting furnace, and then when the elemental raw materials are refined, the degree of refinement can be improved. The smelting time is controlled within 30-50 minutes. The smelting time is controlled to achieve the purpose of fully dissolving and evenly distributing the elemental raw materials. After smelting, the elemental raw materials go through the solid solution strengthening stage, the fine grain strengthening stage and the precipitation strengthening stage to improve the strength and toughness of the steel.

[0078] Casting step: The molten high-temperature steel liquid is cast into a predetermined shape to obtain the cast steel. The casting temperature is controlled within the range of 1500-1600°C and the casting speed is controlled within the range of 0.8-2 m / min. By controlling the casting temperature and casting speed, the steel with the desired microstructure and properties can be obtained.

[0079] Heat treatment steps: The cast steel undergoes quenching and tempering to produce high-strength steel. The specific treatment process includes rolling, quenching, and tempering. The steel is first heated to 1085°C for rolling; then cooled to 910°C for quenching to transform the internal structure of the steel into martensite; and then tempered at 240°C to eliminate quenching stress. This quenching and tempering process aims to achieve a high-hardness martensite structure through quenching, and then tempering to adjust the structure and eliminate internal stress. This steel not only has high strength (tensile strength ≥1460MPa and yield strength ≥1220MPa), but also exhibits good elongation ≥12.0% and hardness ≥475HB. At the same time, its impact energy reaches over 40J at -20°C. Its excellent corrosion resistance enables long-term use in harsh oil and gas transportation environments, reducing maintenance costs and improving pipeline operation safety.

[0080] Example 4:

[0081] This embodiment provides a method for preparing quenched and tempered high-strength steel, comprising the following steps:

[0082] Melting step: The raw materials are mixed in proportion, and then the raw metals are heated in a melting furnace until they are molten. The mixed raw materials are then added to the melting furnace and mixed thoroughly to obtain high-temperature molten steel. The raw materials are as follows in terms of weight percentage:

[0083] Carbon 0.27%, silicon 0.82%, manganese 1.72%, niobium 0.04%, aluminum 0.032%, titanium 0.017%, molybdenum 0.27%, phosphorus, sulfur, and the remainder is iron, wherein the total content of phosphorus and sulfur does not exceed 0.02%. Of course, some unavoidable impurities may be present. In addition, the smelting furnace in this embodiment can be a blast furnace or a vacuum induction furnace;

[0084] In the smelting step, the ratio of gases in the smelting furnace is adjusted to form a neutral atmosphere. The atmosphere in the furnace is controlled to prevent oxidation of the molten steel and to ensure that the elements are fully dissolved and evenly distributed. During the smelting process, the ratio of gases in the smelting furnace is adjusted to form a neutral atmosphere. The atmosphere in the furnace is controlled to prevent oxidation of the molten steel and to ensure that the elements are fully dissolved and evenly distributed. In addition, when the elemental raw materials are added to the smelting furnace for mixing, a vibration device is used to vibrate the smelting furnace. The vibration device vibrates the elemental raw materials in the smelting furnace, and then when the elemental raw materials are refined, the degree of refinement can be improved. The smelting time is controlled within 30-50 minutes. The smelting time is controlled to achieve the purpose of fully dissolving and evenly distributing the elemental raw materials. After smelting, the elemental raw materials go through the solid solution strengthening stage, the fine grain strengthening stage and the precipitation strengthening stage to improve the strength and toughness of the steel.

[0085] Casting step: The molten high-temperature steel liquid is cast into a predetermined shape to obtain the cast steel. The casting temperature is controlled within the range of 1500-1600°C and the casting speed is controlled within the range of 0.8-2 m / min. By controlling the casting temperature and casting speed, the steel with the desired microstructure and properties can be obtained.

[0086] Heat treatment steps: The cast steel is tempered to obtain high-strength steel. The specific treatment contents include rolling, quenching and tempering, that is, first heating to 1080℃ for rolling; then cooling to 905℃ for quenching to transform the internal structure of the steel into martensite; then tempering at 240℃ to eliminate quenching stress. This tempering process aims to obtain high-hardness martensite structure through quenching, and then adjust the structure state through tempering, eliminate internal stress, and improve the toughness and comprehensive mechanical properties of the steel. The hardness is controlled between 460-480HB, which not only ensures that the steel has sufficient strength, but also facilitates subsequent mechanical processing and forming, improving the flexibility of material use and production efficiency. The steel exhibits extremely high mechanical properties: tensile strength exceeds 1490MPa, yield strength is not less than 1260MPa, elongation remains above 12.5%, hardness is not less than 478HB, and impact energy is greater than 40J at -20℃. In addition, its excellent fatigue resistance and processing properties make it an ideal material for aerospace components such as landing gear and structural frames, helping to improve the overall performance and safety of aircraft.

[0087] Example 5

[0088] This embodiment provides a method for preparing quenched and tempered high-strength steel, comprising the following steps:

[0089] Melting step: The raw materials are mixed in proportion, and then the raw metals are heated in a melting furnace until they are molten. The mixed raw materials are then added to the melting furnace and mixed thoroughly to obtain high-temperature molten steel. The raw materials are as follows in terms of weight percentage:

[0090] Carbon 0.30%, silicon 0.90%, manganese 1.8%, niobium 0.05%, aluminum 0.04%, titanium 0.01%, molybdenum 0.3%, phosphorus, sulfur, and the remainder is iron, wherein the total content of phosphorus and sulfur does not exceed 0.02%. Of course, some unavoidable impurities may be present. In addition, the smelting furnace in this embodiment can be a blast furnace or a vacuum induction furnace;

[0091] In the smelting step, the ratio of gases in the smelting furnace is adjusted to form a neutral atmosphere. The atmosphere in the furnace is controlled to prevent oxidation of the molten steel and to ensure that the elements are fully dissolved and evenly distributed. During the smelting process, the ratio of gases in the smelting furnace is adjusted to form a neutral atmosphere. The atmosphere in the furnace is controlled to prevent oxidation of the molten steel and to ensure that the elements are fully dissolved and evenly distributed. In addition, when the elemental raw materials are added to the smelting furnace for mixing, a vibration device is used to vibrate the smelting furnace. The vibration device vibrates the elemental raw materials in the smelting furnace, and then when the elemental raw materials are refined, the degree of refinement can be improved. The smelting time is controlled within 30-50 minutes. The smelting time is controlled to achieve the purpose of fully dissolving and evenly distributing the elemental raw materials. After smelting, the elemental raw materials go through the solid solution strengthening stage, the fine grain strengthening stage and the precipitation strengthening stage to improve the strength and toughness of the steel.

[0092] Casting step: The molten high-temperature steel liquid is cast into a predetermined shape to obtain the cast steel. The casting temperature is controlled within the range of 1500-1600°C and the casting speed is controlled within the range of 0.8-2 m / min. By controlling the casting temperature and casting speed, the steel with the desired microstructure and properties can be obtained.

[0093] Heat treatment steps: The cast steel is subjected to tempering treatment to obtain high-strength steel. The specific treatment contents include rolling, quenching and tempering, that is, first heating to 1100℃ for rolling; then cooling to 900℃ for quenching to transform the internal structure of the steel into martensite; then tempering at 240℃ to eliminate quenching stress. This tempering process aims to obtain high-hardness martensite structure through quenching, and then adjust the structure state through tempering, eliminate internal stress, and improve the toughness and comprehensive mechanical properties of the steel. The hardness is controlled between 460-480HB, which not only ensures that the steel has sufficient strength, but also facilitates subsequent mechanical processing and forming, and improves the flexibility of material use and production efficiency.

[0094] The steel exhibits excellent mechanical properties: tensile strength up to 1440MPa, yield strength reaches 1160MPa, elongation exceeds 14%, hardness greater than 475HB and less than or equal to 480HB, and impact energy exceeds 45J at -20℃.

[0095] Comparative Example: A method for producing non-quenched and tempered high-strength wear-resistant steel for HB450 grade track shoes disclosed in Chinese invention patent publication number CN110541055A. The high-strength wear-resistant steel contains the following chemical components in percentage by mass:

[0096] Carbon: 0.22-0.27%; Silicon: ≤0.30%; Manganese: 3.0-5.0%; Phosphorus: ≤0.012%; Sulfur: ≤0.002%; Molybdenum: 0.10-0.50%; Titanium: 0.10-0.15%; Boron: 0.0010-0.0040%; Nitrogen ≤0.0040%, and the rest are iron and unavoidable impurities; Taking the above-mentioned high-strength wear-resistant steel as the implementation object, the steel plate is produced through the BOF converter smelting + LF refining outside the furnace + RH treatment + slab continuous casting + controlled rolling process.

[0097] Figure 1 This is the metallographic structure diagram of the high-strength steel obtained in Example 1 of the present invention. Figure 2 This is the metallographic structure diagram of the high-strength steel obtained in Example 4 of the present invention. Figure 1 and Figure 2 It is easy to see in the metallographic structure diagram that the needle-shaped martensite is neatly arranged with a small amount of bainite and pearlite in the middle, which corresponds to the high strength and excellent plasticity and toughness of the material of the present invention.

[0098] Table 1 Raw material composition and weight percentage in Examples 1-5 and Comparative Examples

[0099] category carbon silicon manganese Phosphorus and sulfur molybdenum niobium aluminum titanium boron Example 1 0.28％ 0.85％ 1.75％ ≤0.02％ 0.27％ 0.04％ 0.035％ 0.01％ - Example 2 0.28％ 0.85％ 1.75％ ≤0.02％ 0.27％ 0.04％ 0.035％ 0.015％ - Example 3 0.26％ 0.9％ 1.72％ ≤0.02％ 0.20％ 0.03％ 0.03％ 0.02％ - Example 4 0.27％ 0.82％ 1.72％ ≤0.02％ 0.27％ 0.04％ 0.032％ 0.017％ - Example 5 0.30％ 0.80％ 1.8％ ≤0.02％ 0.3％ 0.05％ 0.04％ 0.01％ - Comparative Example 0.22-0.27 ≤0.30 3.0-5.0 ≤0.02 0.1-0.5 - - 0.1-0.15 ≤0.004

[0100] Table 2 Performance parameters of high strength steel of Examples 1-5 and Comparative Example

[0101] Yield strength MPa Tensile strength MPa -20℃ horizontal Kv / J Elongation % Hardness HB Example 1 ≥1160 ≥1440 ≥45 ≥14.0 ≥460 Example 2 ≥1200 ≥1480 ≥42 ≥13.0 ≥472 Example 3 ≥1220 ≥1460 ≥40 ≥12.0 ≥475 Example 4 ≥1260 ≥1490 ≥40 ≥12.5 ≥478 Example 5 ≥1260 ≥1460 ≥40 ≥14.0 ≥478 Comparative Example ≥1140 ≥1460 ≥26 - 420-465

Claims

1. A quenched and tempered high-strength steel, characterized in that: The high-strength steel comprises the following elemental raw materials in weight percentage: Carbon 0.26%-0.30%, silicon 0.80%-0.90%, manganese 1.7%-1.8%, niobium 0.03%-0.05%, aluminum 0.03%-0.04%, titanium 0.01%-0.02%, molybdenum 0.2%-0.3%, phosphorus and sulfur, and the rest is iron, of which the total content of phosphorus and sulfur does not exceed 0.02%.

2. The quenched and tempered high-strength steel according to claim 1, characterized in that: The high-strength steel is quenched and tempered in the following manner: Firstly heat to the temperature range of 1080-1100℃ for rolling; Then cool it down to 900-915℃ for quenching, so that the internal structure of the steel is transformed into martensite; Then the steel is tempered at 240-245°C to eliminate quenching stress.

3. The quenched and tempered high-strength steel according to claim 2, characterized in that: The hardness of the high-strength steel after quenching and tempering is controlled at 460-480HB.

4. A method for preparing quenched and tempered high-strength steel, characterized in that: The steps include: Melting step: The elemental raw materials are mixed in proportion, and then the metal is heated in a melting furnace until it is molten. The mixed elemental raw materials are then added to the melting furnace and mixed thoroughly to obtain high-temperature molten steel. The elemental raw materials include the following in weight percentage: Carbon 0.26%-0.30%, silicon 0.80%-0.90%, manganese 1.7%-1.8%, niobium 0.03%-0.05%, aluminum 0.03%-0.04%, titanium 0.01%-0.02%, molybdenum 0.2%-0.3%, phosphorus, sulfur, and the rest is iron, of which the total content of phosphorus and sulfur does not exceed 0.02%; Casting step: casting the molten high-temperature steel liquid into a predetermined shape to obtain cast steel; Heat treatment steps: The cast steel is subjected to tempering treatment to obtain high-strength steel. The specific treatment contents include rolling, quenching and tempering.

5. The method for preparing quenched and tempered high-strength steel according to claim 4, characterized in that: During the smelting step, the ratio of gases in the smelting furnace is adjusted to form a neutral atmosphere.

6. The method for preparing quenched and tempered high-strength steel according to claim 4, characterized in that: In the casting step, the casting temperature is controlled within the range of 1500-1600°C.

7. The method for preparing quenched and tempered high-strength steel according to claim 4, characterized in that: In the casting step, the casting speed is controlled within the range of 0.8-2 m / min.

8. The method for preparing quenched and tempered high-strength steel according to claim 4, characterized in that: In the smelting step, the raw materials are put into the smelting furnace, and the smelting furnace is vibrated using a vibration device.

9. The method for preparing quenched and tempered high-strength steel according to claim 4, characterized in that: In the smelting step, the smelting time is controlled within 30-50 minutes.

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