Ultrahigh-toughness cooling section steel and production process thereof

Abstract

The invention relates to the technical field of profile steel, in particular to ultrahigh-toughness cooled profile steel and a production process thereof, and the ultrahigh-toughness cooled profile steel comprises the following chemical components in percentage by weight: 0.42%-0.48% of carbon, 1.1%-1.2% of silicon, 1.6%-1.75% of manganese, 0.7%-0.85% of nickel, 0.55%-0.65% of chromium, 0.32%-0.38% of molybdenum, 0.045%-0.055% of niobium, 0.0035%-0.0045% of boron, 0.06%-0.09% of vanadium, 0.02%-0.04% of aluminum and the balance of iron and inevitable impurities, wherein the content of each of sulfur and phosphorus does not exceed 0.01%; the steel has the beneficial effects that by precisely regulating and controlling chemical components and adopting advanced heat treatment technologies such as ultra-fast cooling, dynamic phase change control and nanoscale precipitate regulation and control, the steel keeps high strength (the tensile strength is larger than or equal to 1400 MPa) and meanwhile has excellent toughness (the percentage elongation after fracture is larger than or equal to 20%). The high-strength and high-toughness combination enables the steel to have higher reliability and longer service life in an extreme environment.

Description

Technical Field

[0001] The present invention relates to the field of profiled steel, and particularly to an ultra-high strength and toughness cooled profiled steel and its production process. Background Art

[0002] With the rapid development of modern industry, especially in the fields of aerospace, deep-sea engineering, high-pressure vessel manufacturing, and high-performance automobile manufacturing, the performance requirements for steel are becoming increasingly stringent. Although traditional steels can meet the basic mechanical requirements to a certain extent, in extreme environments such as high pressure, high temperature, low temperature, or strong corrosive media, their strength, toughness, fatigue resistance, and corrosion resistance often fail to meet the requirements for long-term service. Therefore, the development of new steels with ultra-high strength, high toughness, excellent fatigue resistance, and good corrosion resistance has become a hot topic in current materials science research.

[0003] Traditional steel strengthening methods mainly include alloying, heat treatment, and strain hardening. However, while these methods improve strength, they often sacrifice toughness or other important properties. For example, simply increasing the carbon content to improve strength will significantly reduce the toughness and weldability of the steel. In addition, traditional heat treatment processes often have difficulty precisely controlling the microstructure and precipitates of the steel, resulting in unstable mechanical properties. Summary of the Invention

[0004] The purpose of the present invention is to provide an ultra-high strength and toughness cooled profiled steel and its production process to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solution: An ultra-high strength and toughness cooled profiled steel, the chemical composition of the ultra-high strength and toughness cooled profiled steel includes by weight percentage:

[0006] Carbon: 0.42% to 0.48%, precisely regulated to achieve the best balance between strength and toughness;

[0007] Silicon: 1.1% to 1.2%, enhancing the heat resistance and oxidation resistance of the steel;

[0008] Manganese: 1.6% to 1.75%, improving the hardenability and strength of the steel;

[0009] Nickel: 0.7% to 0.85%, enhancing the low-temperature toughness and corrosion resistance of the steel;

[0010] Chromium: 0.55% to 0.65%, increasing the hardenability and heat resistance of the steel;

[0011] Molybdenum: 0.32% to 0.38%, improving the strength, hardness, and tempering softening resistance of the steel;

[0012] Niobium: 0.045% to 0.055%, refining the grains and improving the strength and toughness of the steel;

[0013] Boron: 0.0035% to 0.0045%, improving the hardenability and hardness of steel;

[0014] Vanadium: 0.06% to 0.09%, forming stable carbides and enhancing the strength and wear resistance of steel;

[0015] Aluminum: 0.02% to 0.04%, deoxidizing and refining grains, improving the purity and toughness of steel;

[0016] The balance is iron and inevitable impurities, and the contents of sulfur and phosphorus do not exceed 0.01% respectively;

[0017] The section steel undergoes a unique heat treatment process, including Ultra-Fast Cooling (UFC) technology, Dynamic Phase Transformation Control (DPC), and Nano-Precipitate Regulation (NPR), enabling its tensile strength to reach 1400 MPa

[0018] or more, while maintaining an elongation after fracture of more than 20%.

[0019] Preferably, it further includes the microalloying element titanium, with its content being 0.035% to 0.045% by weight percentage. Acting together with niobium and vanadium, by forming composite carbides, it further optimizes the microstructure and mechanical properties of the steel.

[0020] A production process for preparing ultra-high strength and toughness cooled section steel, comprising the following steps:

[0021] a) High-precision batching and vacuum melting: Using a high-precision batching system to ensure precise control of chemical components, and melting in a vacuum induction furnace to reduce the content of gases and inclusions;

[0022] b) Electromagnetic stirring and continuous casting forming: Introducing electromagnetic stirring during the melting process to promote uniform distribution of components, and then performing continuous casting. Using advanced liquid core reduction technology to control the cooling rate to obtain an ideal microstructure;

[0023] c) Precision rolling and Ultra-Fast Cooling (UFC): Heating the billet to 1175°C to 1225°C for precision hot rolling, and then immediately cooling it ultra-fast to about 450°C to 550°C. Using Dynamic Phase Transformation Control (DPC) technology to precisely regulate the transformation of austenite to martensite to refine grains;

[0024] d) Secondary heating and warm rolling: Reheating the cooled steel to 875°C to 925°C for warm rolling, adopting a multi-pass small reduction rolling strategy, combined with on-line temperature monitoring, to further refine grains and optimize the structure;

[0025] e) Quenching and nanoscale precipitate regulation of NPR: Water quenching or oil quenching is adopted, followed by the first tempering in the temperature range of 575 °C to 625 °C. The nanoscale precipitate regulation technology is utilized to promote the precipitation of fine carbides, enhancing the strength and toughness of the steel; then the second tempering is carried out at a lower temperature to balance the strength and toughness of the steel;

[0026] f) Surface nanocrystallization and strengthening treatment: After the final heat treatment, the surface of the steel is subjected to nanocrystallization treatment, such as shot peening or ultrasonic shot peening, followed by low-temperature nitriding or carburizing treatment to improve the surface hardness and corrosion resistance;

[0027] g) Stress relief and shape stabilization treatment: The steel is subjected to low-temperature aging treatment to release residual stress and improve shape stability.

[0028] Preferably, in step c), the ultra-fast cooling UFC adopts the cooperative cooling technology of high-pressure water spray and air flow to achieve rapid and uniform cooling of the steel, precisely control the cooling rate, and optimize the phase transformation process of the steel.

[0029] Preferably, in step d), the precision rolling adopts an advanced mill control system to achieve precise control of the rolling force and real-time monitoring of the rolling temperature, ensuring the temperature and microstructure uniformity of the steel during the rolling process.

[0030] Preferably, during the quenching and nanoscale precipitate regulation of NPR in step e), an intelligent temperature control system is adopted, combined with advanced material simulation software, to precisely control the heating, holding, and cooling processes to achieve fine regulation of the microstructure and optimized distribution of nanoscale precipitates.

[0031] Preferably, the surface nanocrystallization and strengthening treatment in step f) also includes subsequent low-temperature nitriding or carburizing treatment, adopting ion implantation or plasma spraying technology to improve the surface hardness and corrosion resistance of the steel while maintaining good matrix toughness.

[0032] Preferably, the prepared ultra-high strength and toughness cooled steel is used to manufacture components. The components are applicable to high-pressure vessels, deep-sea engineering structures, key components of aerospace, heavy-duty mechanical components, and high-performance automotive parts in extreme environments. Their high strength, high toughness, and excellent fatigue resistance significantly improve the reliability and service life of the components.

[0033] Preferably, during the manufacturing process of the components, advanced welding technologies, such as laser welding or electron beam welding, are adopted, combined with local preheating, interpass temperature, and post-weld heat treatment measures, as well as ultrasonic testing and X-ray testing of the welds, to ensure that the weld quality is equivalent to that of the base metal and avoid embrittlement of the heat-affected zone.

[0034] Preferably, it also includes mechanical property evaluation and reliability testing, such as Charpy V-notch impact test, tensile test, fatigue test and stress corrosion cracking test, as well as non-destructive testing NDT, such as ultrasonic testing, magnetic particle testing and penetrant testing, to ensure that the components meet the design requirements and comply with relevant standards and specifications, and at the same time provide prediction and evaluation of long-term service performance.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] The ultra-high strength and toughness cooled steel and its production process proposed by the present invention, through precise regulation of chemical composition and the adoption of advanced heat treatment technologies, such as ultra-rapid cooling, dynamic phase transformation control and nano-scale precipitate regulation, the steel of the present invention has excellent toughness (elongation after fracture ≥ 20%) while maintaining high strength (tensile strength ≥ 1400 MPa). This combination of high strength and toughness makes the steel have higher reliability and service life in extreme environments.

[0037] By precisely controlling the cooling rate and phase transformation process, the steel of the present invention obtains fine grains and a uniform microstructure, which helps to improve the strength and toughness of the steel, and at the same time reduces the possibility of crack initiation and propagation.

[0038] Through microalloying and surface treatment technologies, such as low-temperature nitriding or carburizing, a dense protective layer is formed on the surface of the steel of the present invention, improving its corrosion resistance and fatigue resistance. This is particularly important for applications under strong corrosive media or alternating loads.

[0039] Although the steel of the present invention has high strength and high toughness, through reasonable alloy design and heat treatment process, it still maintains good weldability and workability, facilitating the manufacture of components with complex shapes.

[0040] The ultra-high strength and toughness cooled steel of the present invention is particularly suitable for fields such as high-pressure vessels, deep-sea engineering structures, key components of aerospace and high-performance automotive parts under extreme environments. Its high strength, high toughness and excellent comprehensive performance will significantly improve the reliability and service life of these components, reduce maintenance costs and promote the development of related industries. Brief Description of the Drawings

[0041] Figure 1 It is a flow chart of the method of the present invention. Detailed Embodiments

[0042] In order to clearly and completely describe the objectives, technical solutions of the present invention, and make the advantages more clearly understood, the following further details the embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are some embodiments of the present invention, rather than all embodiments, and are only used to explain the embodiments of the present invention, not to limit the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0043] Embodiment 1, the present invention provides a technical solution: a basic ultra-high strength and toughness cooled steel and its production process.

[0044] Chemical composition:

[0045] Carbon: 0.45%

[0046] Silicon: 1.15%

[0047] Manganese: 1.65%

[0048] Nickel: 0.75%

[0049] Chromium: 0.6%

[0050] Molybdenum: 0.35%

[0051] Niobium: 0.05%

[0052] Boron: 0.004%

[0053] Vanadium: 0.075%

[0054] The balance is iron and inevitable impurities (sulfur ≤ 0.01%, phosphorus ≤ 0.01%)

[0055] Production process:

[0056] Batching and melting: Using a high-precision batching system to ensure precise control of chemical composition, and melting in a vacuum induction furnace to reduce gas and inclusion content.

[0057] Continuous casting: Using electromagnetic stirring to promote uniform distribution of components, and implementing liquid core reduction technology during continuous casting to control the cooling rate.

[0058] Rolling and cooling: The billet is heated to 1200 °C, subjected to precision hot rolling, and then immediately super-rapidly cooled to 500 °C, using dynamic phase transformation control to refine grains.

[0059] Tempering: After quenching, the first tempering is carried out at 600 °C, and then the second tempering is carried out at 450 °C to balance strength and toughness.

[0060] Surface treatment: Shot peening treatment to improve surface hardness.

[0061] Example 2: Based on Example 1, a microalloyed enhanced ultra-high strength and toughness cooled steel is proposed.

[0062] Chemical composition (based on Example 1, adding microalloying elements):

[0063] Based on Example 1, add titanium: 0.04%

[0064] Production process:

[0065] 1 - 4. Same as Example 1.

[0066] Surface treatment: On the basis of the shot peening treatment in Example 1, add low-temperature nitriding treatment to improve surface hardness and corrosion resistance.

[0067] Example 3: Based on Example 1, an ultra-high strength and toughness cooled steel with optimized heat treatment process is proposed.

[0068] Chemical composition: Same as Example 1.

[0069] Production process:

[0070] 1 - 3. Same as Example 1.

[0071] 4. Optimized tempering: After quenching, first conduct the first tempering at 575°C, and use an intelligent temperature control system and material simulation software to precisely control the heating, holding, and cooling processes to promote the precipitation of nanoscale carbides; then conduct the second tempering at 425°C to further balance strength and toughness.

[0072] 5. Surface treatment: Ultrasonic shot peening treatment combined with low-temperature carburizing to improve surface hardness and wear resistance.

[0073] Example 4: Based on Example 3, high-performance component manufacturing and application are proposed.

[0074] Material: Use the ultra-high strength and toughness cooled steel with optimized heat treatment process in Example 3.

[0075] Component manufacturing:

[0076] Cutting and forming: According to the design requirements, precisely cut and form the steel.

[0077] Welding: Use laser welding, preheat locally to 200°C, control the interlayer temperature within 250°C, and conduct post-weld heat treatment at 600°C × 2h after welding to ensure that the weld quality is equivalent to that of the base metal.

[0078] Nondestructive testing: Conduct ultrasonic testing and X-ray testing on the welds to ensure no defects.

[0079] Final inspection: Charpy V-notch impact test, tensile test, fatigue test and stress corrosion cracking test, as well as magnetic particle inspection and penetration inspection are carried out to ensure that the components meet the design requirements and relevant standards and specifications.

[0080] application:

[0081] High-pressure container: used to store high-pressure gas or liquid, such as hydrogen cylinders, liquefied natural gas tanks, etc.

[0082] Deep-sea engineering structures: used in deep-sea drilling platforms, underwater pipelines, etc., to withstand extreme water pressure and environmental corrosion.

[0083] Key aerospace components: such as landing gear, engine brackets, etc., require high strength, high toughness and light weight.

[0084] High-performance automotive parts: such as drive shafts, suspension systems, etc., require long-term service reliability and fatigue resistance.

[0085] Examples 1 to 4 describe in detail the production process of ultra-high strength and toughness cooling steel from basic type to micro-alloyed enhanced type and optimized heat treatment process type, as well as the process and application scenarios of using these steels to manufacture high-performance components. Each example is improved and optimized based on the previous example, aiming to develop steel with excellent mechanical properties and long-term service reliability through scientific alloy design, optimized heat treatment process and advanced manufacturing technology to meet the needs of modern industry for high-performance materials.

[0086] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An ultra-high strength and toughness cooling steel, characterized in that: The chemical composition of the ultra-high strength and toughness cooling steel includes by weight percentage: Carbon: 0.42% to 0.48%, precisely regulated to achieve the best balance of strength and toughness; Silicon: 1.1% to 1.2%, enhances the heat resistance and oxidation resistance of steel; Manganese: 1.6% to 1.75%, improves the hardenability and strength of steel; Nickel: 0.7% to 0.85%, enhances the low-temperature toughness and corrosion resistance of steel; Chromium: 0.55% to 0.65%, increases the hardenability and heat resistance of steel; Molybdenum: 0.32% to 0.38%, improves the strength, hardness and resistance to temper softening of steel; Niobium: 0.045% to 0.055%, refines grains and improves the strength and toughness of steel; Boron: 0.0035% to 0.0045%, improves the hardenability and hardness of steel; Vanadium: 0.06% to 0.09%, forms stable carbides, enhancing the strength and wear resistance of steel; Aluminum: 0.02% to 0.04%, deoxidation and grain refinement, improving the purity and toughness of steel; The balance is iron and unavoidable impurities, of which sulfur and phosphorus do not exceed 0.01% each; The steel section undergoes a unique heat treatment process, including ultra-fast cooling UFC technology, dynamic phase change control DPC and nano-scale precipitate regulation NPR, so that its tensile strength reaches more than 1400MPa while maintaining an elongation of more than 20%.

2. The ultra-high strength and toughness cooling steel according to claim 1, characterized in that: It also includes the microalloying element titanium, whose content is 0.035% to 0.045% by weight, which works together with niobium and vanadium to further optimize the microstructure and mechanical properties of the steel by forming complex carbides.

3. A production process for preparing the ultra-high strength and toughness cooling steel according to any one of claims 1 to 2, characterized in that: The following steps are involved: a) High-precision batching and vacuum melting: A high-precision batching system is used to ensure accurate control of chemical composition, and melting is carried out in a vacuum induction furnace to reduce the content of gas and inclusions; b) Electromagnetic stirring and continuous casting: electromagnetic stirring is introduced during the smelting process to promote uniform distribution of components, followed by continuous casting, using advanced liquid core pressing technology to control the cooling rate to obtain the ideal microstructure; c) Precision rolling and ultra-fast cooling (UFC): The ingot is heated to 1175°C to 1225°C for precision hot rolling, and then immediately ultra-fast cooled to about 450°C to 550°C. The dynamic phase change control (DPC) technology is used to precisely control the transformation of austenite to martensite to refine the grains; d) Secondary heating and warm rolling: The cooled steel is reheated to 875°C to 925°C and warm rolled. A multi-pass small reduction rolling strategy is adopted, combined with online temperature monitoring, to further refine the grains and optimize the structure. e) Quenching and nano-precipitate regulation NPR: Water quenching or oil quenching is used, followed by the first tempering in the temperature range of 575℃ to 625℃, using nano-precipitate regulation technology to promote the precipitation of fine carbides and enhance the strength and toughness of the steel; then the second tempering is performed at a lower temperature to balance the strength and toughness of the steel; f) Surface nano-crystallization and strengthening treatment: After the final heat treatment, the steel surface is nano-crystallized, such as shot peening or ultrasonic shot peening, followed by low-temperature nitriding or carburizing treatment to improve surface hardness and corrosion resistance; g) Stress release and shape stabilization treatment: low temperature aging treatment is performed on the steel to release residual stress and improve shape stability.

4. A production process according to claim 3, characterized in that: The ultra-fast cooling (UFC) in step c) uses high-pressure water spray and air flow synergistic cooling technology to achieve rapid and uniform cooling of the steel and accurately control the cooling rate to optimize the phase change process of the steel.

5. A production process according to claim 3, characterized in that: The precision rolling in step d) adopts an advanced rolling mill control system to achieve precise control of the rolling force and real-time monitoring of the rolling temperature, ensuring the temperature and structural uniformity of the steel during the rolling process.

6. A production process according to claim 3, characterized in that: During the quenching and nanoscale precipitate regulation NPR process in step e), an intelligent temperature control system is used in combination with advanced material simulation software to accurately control the heating, insulation and cooling processes to achieve fine regulation of the microstructure and optimized distribution of nanoscale precipitates.

7. A production process according to claim 3, characterized in that: The surface nano-crystallization and strengthening treatment in step f) also includes subsequent low-temperature nitriding or carburizing treatment, using ion implantation or plasma spraying technology to improve the surface hardness and corrosion resistance of the steel while maintaining good matrix toughness.

8. A production process according to claim 3, characterized in that: The prepared ultra-high strength and toughness cooling steel is used to manufacture components. The components are suitable for high-pressure vessels in extreme environments, deep-sea engineering structures, key aerospace components, heavy-loaded mechanical components and high-performance automotive parts. Their high strength, high toughness and excellent fatigue resistance significantly improve the reliability and service life of the components.

9. A production process according to claim 8, characterized in that: During the manufacturing process of the components, advanced welding technologies such as laser welding or electron beam welding are used, combined with local preheating, interlayer temperature and post-weld heat treatment measures, as well as ultrasonic and X-ray testing of the welds to ensure that the weld quality is equivalent to that of the parent material while avoiding embrittlement of the heat-affected zone.

10. A production process according to claim 9, characterized in that: It also includes mechanical property evaluation and reliability testing, such as Charpy V-notch impact test, tensile test, fatigue test and stress corrosion cracking test, as well as non-destructive testing (NDT), such as ultrasonic testing, magnetic particle testing and penetrant testing, to ensure that the components meet the design requirements and comply with relevant standards and specifications, while providing prediction and evaluation of long-term service performance.

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