WO2023087833A1 - 一种具有优良耐候性能的高强度钢材及其制造方法 - Google Patents

一种具有优良耐候性能的高强度钢材及其制造方法 Download PDF

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WO2023087833A1
WO2023087833A1 PCT/CN2022/115498 CN2022115498W WO2023087833A1 WO 2023087833 A1 WO2023087833 A1 WO 2023087833A1 CN 2022115498 W CN2022115498 W CN 2022115498W WO 2023087833 A1 WO2023087833 A1 WO 2023087833A1
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steel
temperature
slab
tempering
present
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PCT/CN2022/115498
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French (fr)
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赵四新
王成全
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宝山钢铁股份有限公司
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium

Definitions

  • the invention relates to a steel material and a manufacturing method thereof, in particular to a high-strength weather-resistant steel and a manufacturing method thereof.
  • Weathering steel is a kind of low-alloy high-strength steel with good corrosion resistance in the atmosphere. Generally speaking, the weather resistance of weathering steel is more than twice that of ordinary carbon steel. Weathering steel has excellent performance and wide application prospects. It is often used to manufacture various high-strength structural parts exposed to the atmosphere, which can prolong the service life of high-strength structural parts.
  • the weather-resistant steel grade with the highest strength in the national standard "GB/T4171-2008" weather-resistant structural steel is Q550NH, and its chemical composition is C ⁇ 0.16%; Si ⁇ 0.65%; Mn ⁇ 2.0%; P ⁇ 0.025%; S ⁇ 0.030%; Cu: 0.20-0.55%; Cr: 0.30-1.25%; Ni: 0.12-0.65%.
  • the yield strength of the steel is ⁇ 550MPa, the tensile strength is 620-780MPa, and the elongation after fracture is ⁇ 16%.
  • the technical scheme can obtain steel with a yield strength of >700MPa and a tensile strength of >1000MPa through the technological process of smelting, heating and heat preservation, hot rolling, coiling, pickling, cold rolling, continuous annealing and levelling.
  • Ci Chinese patent document CN111378896A (published on July 7, 2020, titled "a high-strength weather-resistant steel plate for building bridges and its manufacturing method") discloses a high-strength weather-resistant steel plate for building bridges, the chemical composition of which is For: C: 0.03-0.09%, Si: 0.05%-0.55%, Mn: 1.10%-2.00%, P ⁇ 0.012%, S ⁇ 0.003%, Cr: 0.50%-1.00%, Cu: 0.30%-0.50% , Ni: 0.20%-1.20%, Als: 0.015%-0.050, Ti: 0.002%-0.030%, V: 0.002%-0.08%, Mo: 0.01%-0.80%, B: 0.0001%-0.0025%, CEV ⁇ 0.65%, Pcm ⁇ 0.28, atmospheric corrosion resistance index I ⁇ 6.5, and the balance is Fe.
  • C 0.03-0.09%
  • Si 0.05%-0.55%
  • Mn 1.10%-2.00%
  • P ⁇ 0.012% S ⁇ 0.003%
  • Cr 0.50%-1.00%
  • the yield strength of the steel produced by using this patent document is ⁇ 620MPa
  • the tensile strength is between 730MPa-850MPa
  • the elongation after breaking is A ⁇ 16%
  • the impact energy KV2 at -40°C is ⁇ 120J.
  • this patent document greatly reduces the Cr content in the weathering steel by adding various microalloying elements such as Sn, Sb, Nb, and RE, and the yield strength of the steel produced by it is ⁇ 650MPa and the resistance Tensile strength ⁇ 750MPa, 30 °C half-scale impact energy up to 65J.
  • the yield strength of existing high-strength weathering steel products is mostly 600-800 MPa, and there are few high-strength weathering steel products with yield strength exceeding 1000 MPa.
  • This new type of weather-resistant steel can be used to prepare high-performance industrial chains, which can well solve the problem of existing steel materials that affect their service life due to mismatches in strength, ductility and plasticity, and weather resistance.
  • One of the objectives of the present invention is to provide a high-strength steel with excellent weather resistance.
  • the steel has a high strength of more than 1000 MPa, and also has good toughness and plasticity matching and excellent weather resistance. It is especially suitable for manufacturing high-strength weather-resistant steel.
  • Industrial chain products for permanent structural parts, mining, mooring, etc. can be widely used in construction machinery, mining, marine engineering and other occasions with more corrosive media.
  • the present invention proposes a steel, wherein in addition to more than 90% by mass of Fe and unavoidable impurities, the steel also contains the following chemical elements in mass percent:
  • the steel of the present invention consists of the following chemical elements in mass percent:
  • C is an element necessary for securing the strength of the steel material. Increasing the C content in the steel will increase the non-equilibrium microstructure transformation ability of the steel, thereby significantly improving the strength of the steel. In addition, in the present invention, the quenching and tempering heat treatment process can suppress the diffusion of C element in the steel to form a shear martensitic transformation, thereby significantly improving the strength of the steel.
  • the content of C element in the steel of the present invention should not be too high. Excessive C content will adversely affect the plasticity and toughness of the steel, and will significantly increase the carbon equivalent of the material and deteriorate the welding performance of the steel. Based on this, in the steel of the present invention, the C element content is controlled between 0.22-0.33%.
  • Si element can be solid-dissolved in the steel material to play the role of solid-solution strengthening.
  • Si element can significantly improve the yield strength, fatigue strength and hardness of steel.
  • solubility of Si in cementite is very low, and the content of Si element in steel should not be too high.
  • the Si element content is controlled between 0.1-1.0%.
  • the Mn element can improve the stability of the austenite in the steel and at the same time improve the hardenability of the steel.
  • Mn can also increase the strength of martensite in the steel through solid solution strengthening, thereby increasing the strength of the steel.
  • the content of Mn element in steel should not be too high.
  • the austenite grains are easy to grow during quenching and heating, which promotes the segregation of harmful elements at the grain boundaries. Based on this, in the steel of the present invention, the content of Mn element is controlled between 0.3-1.5%.
  • adding an appropriate amount of Cr element can improve the hardenability of the steel, and has the effect of secondary hardening, which can form a hardened martensite structure, which is beneficial to improve the strength of the steel.
  • Cr carbides can slow down the grain growth in the heat-affected zone at the welded joint, which is very beneficial to the welding of steel.
  • Adding an appropriate amount of Cr and Ni elements to the steel is beneficial to improve the weather resistance of the steel.
  • the content of Cr element in the steel should not be too high.
  • the content of Cr in the steel is controlled between 0.2-1.6%.
  • Ni In the steel material of the present invention, Ni is an austenite-forming element. As one of the main strengthening elements, Ni can exist in steel in the form of solid solution, and can have unlimited solid solution with iron. In addition, when the Ni element is used in conjunction with the Cr element, the hardenability of the steel can be significantly improved.
  • Ni element can improve the fatigue resistance of the steel, reduce the sensitivity of the steel to notches, reduce the low-temperature embrittlement transition temperature of the steel, and improve the impact toughness of the steel.
  • the Ni element can increase the strength of the steel, and at the same time, the damage to the toughness, plasticity and other properties of the steel is less than that of other alloying elements.
  • the content of the Ni element in the steel of the present invention is controlled between 2.2-3.8%.
  • the Mo element mainly exists in the steel material in a solid solution form. Mo can play a solid solution strengthening effect, which is beneficial to improve the hardenability of the steel, so that the steel can form martensite during the quenching process.
  • the content of Mo element in the steel should not be too high. When the Mo element in the steel is too high, the carbon equivalent of the material will be significantly increased, which is not conducive to the weldability of the steel.
  • Mo is a precious alloy element, adding excessive Mo element will lead to an increase in alloy cost. Based on this, in the steel of the present invention, the Mo element content is controlled between 0.1-0.7%.
  • Cu In the steel of the present invention, adding an appropriate amount of Cu element can significantly improve the weather resistance of the steel and reduce the hydrogen-induced crack sensitivity of the steel. However, it should be noted that too high Cu content is not conducive to the weldability of steel, and it is also prone to copper embrittlement, which deteriorates the surface properties of steel. Therefore, in the steel of the present invention, the content of Cu element is controlled between 0.02-0.3%.
  • Al In the steel of the present invention, the main functions of Al are deoxidation and nitrogen fixation, and the AlN formed by the combination of Al and N can effectively refine the grains.
  • the content of Al element in the steel should not be too high. When the Al element content in the steel is too high, it will affect the castability of the steel and damage the toughness of the steel. Based on this, in the steel of the present invention, the content of Al element is controlled between 0.01-0.045%.
  • V in the steel of the present invention, V, as a strong carbide forming element, can remarkably improve the strength of the steel in the form of dispersed precipitation. But it should be noted that when the addition of V element in the steel is too high, the toughness and welding performance of the steel will be reduced. Based on this, in the steel of the present invention, the V element content is controlled between 0.01-0.25%.
  • N In the steel material of the present invention, N is an austenite-forming element and also an MX-type precipitate-forming element. In order to avoid the enrichment of N element in the steel, it is not appropriate to add too much N to the steel. Therefore, the content of N element must be strictly controlled, and in the steel of the present invention, the content of N element is controlled to be no more than 0.013%.
  • the inventor precisely controls the composition of the steel and the content of each chemical element in the steel, and uses the influence of each alloy element itself and the interaction between them on the microstructure and final performance.
  • the steel material of the invention can obtain high strength and good ductility-plastic matching, and simultaneously have good weather resistance, wear resistance and fatigue resistance.
  • the steel of the present invention also contains Nb and/or Ti, wherein 0 ⁇ Nb ⁇ 0.04%, 0 ⁇ Ti ⁇ 0.03%.
  • Nb is a strong carbide forming element. Adding an appropriate amount of Nb to the steel can not only inhibit the recrystallization of the steel, but also effectively refine the grains. However, it should be noted that when the content of Nb in the steel is too high, coarse NbC particles will be formed under high-temperature tempering conditions, which will deteriorate the low-temperature impact energy of the steel. Therefore, in the present invention, it is preferable to control the added Nb element content to satisfy: 0 ⁇ Nb ⁇ 0.04%.
  • Ti Adding an appropriate amount of Ti element to steel can form fine Ti(C,N) precipitates.
  • Ti(C,N) can effectively prevent the microstructure from coarsening during the welding process of steel and improve the welding quality of the weld.
  • the content of Ti element in the steel should not be too high.
  • coarse TiN particles with corners will be formed during the smelting process, which will reduce the impact toughness and fatigue performance of the steel. Therefore, in the present invention, it is preferable to control the added Ti element content to satisfy: 0 ⁇ Ti ⁇ 0.03%.
  • the content of elements C, Mn, Ni, Cr, Mo and Si in terms of mass percentage also satisfies the following formula: 2.5 ⁇ (12 ⁇ C+0.3 ⁇ Mn+Ni)/(Cr+ 2Mo+2Si) ⁇ 3.2, where the element symbol represents the value before the percent sign of the mass percent content of the corresponding element.
  • the present inventor found through a lot of research that when the content of the main strengthening elements C, Mn, Ni, Cr, Mo and Si in the steel is controlled to satisfy 2.5 ⁇ (12 ⁇ C+0.3 ⁇ Mn+Ni)/(Cr+2Mo +2Si) ⁇ 3.2, the best matching of strength and ductility can be further obtained.
  • the austenite zone of the steel is relatively reduced, the stability of the austenite is reduced, and it is easy to form in the quenching process.
  • the content of bainite is relatively high, and the content of martensite is relatively low.
  • the carbide particles precipitated between the lamellar layers are large and the number is small, so it is difficult to obtain the best matching of strength and ductility.
  • the austenite zone of the steel is relatively expanded, the stability of the austenite is improved, and the diffusibility during quenching and tempering heat treatment
  • the phase change is suppressed, the interlamellar spacing of the martensite structure obtained during the quenching process is relatively large, and the number of dispersed carbides precipitated between the lamellar layers during the tempering process is large, the strength of the steel is high, and the ductility and plasticity are relatively low. It is difficult to obtain the best match of strength and toughness and plasticity.
  • element P, element S and element O are all impurity elements in steel, and if technical conditions permit, in order to obtain steel with better performance and better quality, the content of impurity elements in the material should be reduced as much as possible.
  • the content of the unavoidable impurities in terms of mass percentage satisfies: P ⁇ 0.015%, S ⁇ 0.01%, O ⁇ 0.002%.
  • P element and S element are unavoidable harmful impurity elements in the steel, and both will deteriorate the performance of the steel.
  • P can improve the weather resistance of steel, its side effects are generally greater. Therefore, in the present invention, the P element is controlled to satisfy: P ⁇ 0.015%, and the S element is controlled to satisfy: S ⁇ 0.01%.
  • the impurity element O can form oxides and compound inclusions with deoxidizing elements such as Al in the steel, which is not conducive to the performance of the steel. Therefore, in the present invention, the O element is controlled to satisfy: O ⁇ 0.0015%.
  • More elements of Ni, Mn and Cu are added to the steel of the present invention, which can effectively improve the weather resistance index I of the steel, thereby ensuring that the steel has good weather resistance on the basis of high strength and toughness.
  • the weather resistance index I of the steel of the present invention is I ⁇ 10.0, it is possible to ensure that the steel obtains good environmental corrosion resistance, thereby further ensuring that the steel of the present invention is not prone to corrosion and fracture during use, and the service life is improved.
  • the microstructure of the steel of the present invention is tempered martensite + tempered bainite + carbides dispersedly distributed between lamellar layers.
  • the performance of the steel of the present invention satisfies: yield strength R p0.2 ⁇ 1100MPa, tensile strength R m ⁇ 1250MPa, elongation A ⁇ 14%, reduction of area Z ⁇ 50%, Charpy impact energy at room temperature A kv ⁇ 80J, Charpy impact energy A kv ⁇ 70J at -20°C.
  • Another object of the present invention is to provide a method for manufacturing the aforementioned steel material.
  • the manufacturing method of the present invention is simple in process, and the obtained steel has excellent high-strength toughness and good weather resistance, its yield strength R p0.2 ⁇ 1100MPa, tensile strength R m ⁇ 1250MPa, elongation A ⁇ 14%.
  • the present invention provides a method for manufacturing the above-mentioned steel, said method comprising the following steps in sequence:
  • the present inventor has deeply studied the role of main strengthening elements such as C, Si, Mn, Ni, Cr, Mo in the composition of steel in quenching and tempering heat treatment.
  • the present inventor rationally designs the proportion of alloying elements and cooperates with the quenching and tempering heat treatment process of optimal design, and utilizes the influence of each alloying element itself and the interaction between them on the microstructure of steel after quenching and tempering heat treatment.
  • the microstructure of the steel of the invention is precisely controlled. After quenching and tempering heat treatment, a mixed multiphase structure of tempered martensite, tempered bainite and interlamellar dispersed carbides is formed, thereby ensuring the performance of the steel product of the invention.
  • the inventors optimized the heat treatment of quenching and tempering in step (3).
  • the steel is kept at a heating temperature of 860-1000°C for 2-6 hours to make the steel fully austenitized.
  • the carbide or nitride particles of Cr, Mo, Nb, V, Ti, Al and other elements in the steel are partially dissolved into the austenite, and the undissolved carbide and carbide particles continue to pin the austenite grain boundary, inhibiting the Austenite grain growth.
  • finer non-equilibrium structures such as martensite and bainite can be formed in the steel, thereby ensuring that the steel of the invention has higher strength.
  • the tempering process keep it warm for 1-4h at the tempering temperature of 400-600°C.
  • the high-density dislocations formed during the quenching process of the steel are partially annihilated, and the supersaturated C, Cr, and Mo elements in the solid solution in the non-equilibrium structure of the steel can be redistributed in the form of carbides in martensite or bainite.
  • Precipitation in the middle of the lamellae of the body At this time, due to the low temperature during precipitation, the precipitated particles are not easy to grow, so that the precipitated particles are finer and dispersed.
  • the annihilation of dislocations and the precipitation of carbides and nitrides will lead to a reduction in the internal stress of the steel, and improved plasticity and toughness, thereby ensuring that the steel has higher strength and better Matching plasticity and toughness.
  • the smelted molten steel is cast into a slab by die casting or continuous casting.
  • the ingot mold baking temperature is ⁇ 200°C; in the case of continuous casting, the tundish baking temperature is ⁇ 1100°C, and the baking time is ⁇ 3.5h.
  • the molten steel can be smelted with an electric furnace or a converter, and subjected to LF and VD or RH vacuum refining treatment, and can be tapped after the chemical composition meets the design requirements of the present invention. casting.
  • the refined molten steel can be cast into billets by die casting or continuous casting; in the case of die casting, the baking temperature of the ingot mold can be controlled to be ⁇ 200°C; in the case of continuous casting, The tundish baking temperature can be controlled to be ⁇ 1100°C, and the baking time can be ⁇ 3.5h; preferably, the hot delivery of the slab or the slow cooling time of the off-line can be controlled to be ⁇ 24h.
  • step (2) in the case of adopting a pyrotechnic process, the cast slab is directly rolled or forged into a finished product size, wherein the cast slab is heated at a temperature of 1150- 1250°C, the holding time is 3-12h, the starting rolling temperature or starting forging temperature is ⁇ 1050°C, and the final rolling temperature or final forging temperature is ⁇ 900°C.
  • step (2) in the case of adopting the second firing process, the cast slab is first forged or rolled into an intermediate slab, and then the intermediate slab is forged or rolled is the finished product size, in which the billet heating temperature is 1150-1250°C, the holding time is 3-12h, the starting rolling temperature or starting forging temperature is ⁇ 1050°C, the final rolling temperature or final forging temperature is ⁇ 950°C; the heating temperature of the intermediate billet is 1120-1200°C, the holding time is 3-10h, the starting rolling temperature of the intermediate billet is ⁇ 1050°C, and the final rolling temperature of the intermediate billet is ⁇ 860°C.
  • the billet heating temperature is 1150-1250°C
  • the holding time is 3-12h
  • the starting rolling temperature or starting forging temperature is ⁇ 1050°C
  • the final rolling temperature or final forging temperature is ⁇ 950°C
  • the heating temperature of the intermediate billet is 1120-1200°C
  • the holding time is 3-10h
  • the starting rolling temperature of the intermediate billet is ⁇ 1050°
  • the cast slab in step (2), in the forging or rolling process, can be processed into a finished product size by using the primary firing process or the secondary firing process, and the finished product size specification range is Can be ⁇ 26-150mm.
  • the primary firing process refers to directly forging or rolling the casting billet into the final product size during the forging or rolling process of the billet;
  • the secondary firing process refers to forging or rolling the billet into a predetermined intermediate billet size, and then the intermediate billet is forged or rolled to the final finished product size.
  • step (2) of the present invention whether the first-fire or second-fire lumber process is adopted, the slab needs to be heated at 1150-1250°C, and the slab will be heated during the heating process. Dissolution of precipitated phases and growth of austenite grains.
  • the precipitates of Cr, Mo, Nb, V, Ti, Al, etc. formed in the slab will be partially or completely dissolved in the austenite during high temperature heating, and the undissolved precipitates will pin the austenite grain boundary, And inhibit the excessive growth of austenite grains.
  • holding the heat for a certain period of time at the higher heating temperature is beneficial to the diffusion of segregated elements in the steel and makes the distribution of elements in the slab more uniform.
  • elements such as Ti, Nb, and Al in the steel will be precipitated from the steel again, forming fine and dispersed particles, and inhibiting the growth of recrystallized grains. Refine the organization. Alloying elements such as Cr and Mo solid-dissolved in the steel will inhibit the diffusion-type phase transformation during the cooling process and form medium-low temperature transformation structures such as bainite and martensite to increase the strength of the steel.
  • the cast slab before the forging or rolling starts, the cast slab can be controlled out of the heating furnace and descaled by high-pressure water; after forging or rolling, air cooling or slow cooling can be used. Cool to cool.
  • the steel of the present invention and its manufacturing method have the following advantages and beneficial effects:
  • the present invention optimizes the main strengthening elements such as C, Si, Mn, Ni, Cr, and Mo in the steel.
  • the quenching and tempering process of the steel of the present invention can be controlled.
  • the value of the weather resistance index I of the steel can be further increased, so that the steel can obtain better weather resistance, thereby greatly increasing the service life of the steel in harsh environments .
  • the steel of the present invention has excellent high strength toughness and good weather resistance, and it can be made into high-strength weather-resistant structural parts and high-performance industrial chains such as mining chains and mooring chains, and is widely used in construction machinery, mines and ocean engineering And other occasions that require high strength and toughness steel.
  • Fig. 1 is the microstructure photograph of the steel material of embodiment 1 under the microscope of 5000 times.
  • the steel of embodiment 1-10 adopts following steps to make:
  • the molten steel was smelted and continuously cast to obtain a slab.
  • the smelting adopts electric furnace or converter smelting, and after LF refining and VD or RH vacuum treatment, the steel is tapped after the composition meets the requirements.
  • use die casting or continuous casting to cast the smelted molten steel into a slab, and control the hot delivery of the slab or the slow cooling time of the off-line ⁇ 24h: in the case of die casting, control the baking temperature of the ingot mold ⁇ 200 °C; In the case of continuous casting, control the tundish baking temperature to ⁇ 1100°C and control the baking time to ⁇ 3.5h.
  • the cast slab is processed into the finished product size by using the first-fire forming process or the second-fire forming process, and the finished product size specification range is ⁇ 26-150mm.
  • the heating temperature of the billet is controlled to be 1150-1250°C
  • the holding time is 3-12h
  • the starting rolling temperature or starting forging temperature is ⁇ 1050°C
  • the final rolling temperature or final forging temperature is ⁇ 900 °C.
  • the heating temperature of the billet is controlled to be 1150-1250°C, the holding time is 3-12h, the starting rolling temperature or starting forging temperature is ⁇ 1050°C, and the final rolling temperature or final forging temperature is ⁇ 950°C;
  • the heating temperature of the intermediate billet is 1120-1200°C, the holding time is 3-10h, the starting rolling temperature of the intermediate billet is ⁇ 1050°C, and the final rolling temperature of the intermediate billet is ⁇ 860°C.
  • Comparative Examples 1-3 are finished steel products from different manufacturers, and their chemical compositions are shown in Table 1-1 and Table 1-2 below. Although the steel products of Comparative Examples 1-3 are also produced by the above process steps, at least one of the chemical composition and manufacturing process parameters of Comparative Examples 1-3 does not meet the requirements of the present invention.
  • Table 1-1 and Table 1-2 list the chemical element compositions of the steel materials of Examples 1-10 and Comparative Examples 1-3.
  • Table 1-1 (wt%, the balance is Fe and other unavoidable impurities except P, S and O)
  • Example 1 0.24 0.24 1.21 0.011 0.006 0.41 3.78 0.67 0.18 0.021 0.021 0.05 0.007 0.0071 0.0011
  • Example 2 0.225 0.47 0.76 0.005 0.004 0.67 2.57 0.23 0.11 0.011 0.038 0.21 0.026 0.0117 0.0013
  • Example 3 0.25 0.12 1.42 0.009 0.003 0.85 2.98 0.58 0.02 0.044 - 0.08 0.004 0.0098 0.0009
  • Example 4 0.3 0.78 0.58 0.008 0.005 0.33 3.35 0.41 0.22 0.015 0.013 0.18 0.011 0.0055 0.0008
  • Example 5 0.31 0.55 0.32 0.012 0.002 0.55 2.25 0.34 0.28 0.032 0.031 0.25 0.019 0.0039 0.0012
  • Example 6 0.27 0.96 1.05 0.01 0.002 0.21 3.52 0.12 0.08 0.025 0.028 0.12 0.015 0.0106 0.0015
  • Example 7 0.27 0.96 1.05 0.01
  • Electric furnace smelting is carried out according to the chemical composition shown in Table 1-1 and Table 1-2, and cast into continuous casting slabs after LF refining and RH vacuum treatment.
  • the baking temperature of the tundish is controlled at 1150°C, and the baking time is 5 hours; the slow cooling time of the slab is controlled at 35 hours.
  • the casting slab is processed into a finished product size by using the second-fire process: firstly, the continuous casting slab is heated to 1150°C and kept for 12 hours, and the slab is taken out of the heating furnace and descaled by high-pressure water before rolling, and the opening is controlled.
  • the rolling temperature is 1090°C
  • the final rolling temperature is 950°C
  • the intermediate billet with a size of 280 ⁇ 280mm is obtained; then the obtained intermediate billet is heated to 1120°C, kept for 10 hours, and rolled out after being descaled by high-pressure water , control the starting rolling temperature to 1050°C, and control the final rolling temperature to 880°C to produce a steel product with a specification of ⁇ 75mm, which is air-cooled after rolling.
  • perform quenching and tempering heat treatment control the quenching heating temperature to 940°C, the holding time is 4h, the tempering temperature is 450°C, the holding time is 3h, and then water-cooled to room temperature.
  • Electric furnace smelting is carried out according to the chemical composition shown in Table 1-1 and Table 1-2, and cast into continuous casting slabs after LF refining and RH vacuum treatment.
  • the baking temperature of the tundish is controlled at 1100°C, and the baking time is 6 hours; the slow cooling time of the slab is controlled at 30 hours.
  • the casting slab is processed into a finished product size by using the second-fire process: firstly, the continuous casting slab is heated to 1220°C and kept for 4 hours, and the continuous casting slab is taken out of the heating furnace and descaled by high-pressure water before rolling.
  • the starting rolling temperature is 1120°C
  • the final rolling temperature is 980°C
  • the intermediate billet with a size of 260 ⁇ 260mm is obtained; then the obtained intermediate billet is heated to 1130°C, kept for 6 hours, and rolled out after being descaled by high-pressure water.
  • perform quenching and tempering heat treatment control the quenching heating temperature to 990 ° C, the holding time is 3 hours, the tempering temperature is 420 ° C, the holding time is 2 hours, and then air-cool to room temperature.
  • Electric furnace smelting is carried out according to the chemical composition shown in Table 1-1 and Table 1-2, and cast into continuous casting slabs after LF refining and RH vacuum treatment.
  • the tundish baking temperature is controlled at 1250°C
  • the baking time is 4.5 hours
  • the slab slow cooling time is 28 hours.
  • the continuous casting slab is processed into the finished product size by using the second-fire process: firstly, the continuous casting slab is heated to 1240°C, kept for 3 hours, and the continuous casting slab is taken out of the heating furnace and descaled by high-pressure water before rolling.
  • the starting rolling temperature is 1110°C
  • the final rolling temperature is 970°C
  • the intermediate billet with a size of 220 ⁇ 220mm is obtained; then the obtained intermediate billet is heated to 1150°C, kept for 8 hours, and rolled out after being descaled by high-pressure water , control the starting rolling temperature to 1075°C, and the final rolling temperature to 910°C to produce a steel product with a specification of ⁇ 42mm, which is air-cooled after rolling.
  • perform quenching and tempering heat treatment control the quenching heating temperature to 910°C, the holding time is 2.5h, the tempering temperature is 530°C, the holding time is 1.5h, and then water-cooled to room temperature.
  • the chemical composition shown in Table 1-1 and Table 1-2 it is smelted in an electric furnace, and cast into a continuous casting slab after LF refining and VD vacuum treatment.
  • the tundish baking temperature is controlled at 1200°C
  • the baking time is 3.5 hours
  • the casting slab slow cooling time is 24 hours.
  • the casting slab is processed into the finished product size by using the one-fired process: the continuous casting slab is heated to 1200°C, kept for 6 hours, and the continuous casting slab is taken out of the heating furnace and descaled by high-pressure water before rolling, and the rolling is controlled.
  • the temperature is 1100°C
  • the final rolling temperature is 960°C to produce a steel product with a specification of ⁇ 150mm, which is stacked and cooled after rolling.
  • perform quenching and tempering heat treatment control the quenching heating temperature to 880 ° C, the holding time is 6 hours, the tempering temperature is 570 ° C, the holding time is 4 hours, and then air cool to room temperature.
  • the chemical composition shown in Table 1-1 and Table 1-2 it is smelted in an electric furnace, and cast into a continuous casting slab after LF refining and VD vacuum treatment.
  • the tundish baking temperature is controlled at 1300°C
  • the baking time is 4 hours
  • the slab slow cooling time is 26 hours.
  • the casting slab is processed into the finished product size by the one-fired process: the continuous casting slab is heated to 1170°C, kept for 8 hours, and the continuous casting slab is taken out of the heating furnace and descaled by high-pressure water before rolling, and the rolling is controlled.
  • the temperature is 1070°C
  • the final rolling temperature is 930°C to produce a steel product with a specification of ⁇ 130mm, which is stacked and cooled after rolling. Then perform quenching and tempering heat treatment, control the quenching heating temperature to 960°C, hold time for 5h, tempering temperature to 600°C, hold time for 3h, and then air cool to room temperature.
  • Converter smelting is carried out according to the chemical composition shown in Table 1-1 and Table 1-2.
  • the baking temperature of the ingot mold is controlled to be 200°C, and the slow cooling time of the billet is 48h.
  • the casting slab is processed into the finished product size by using the one-fired process: heat the slab to 1180°C, keep it warm for 10 hours, and take the slab out of the heating furnace and descale it with high-pressure water before rolling.
  • the rolling start temperature is controlled to 1050°C
  • the final rolling temperature is 900°C
  • the steel product with a specification of ⁇ 100mm is produced, and air-cooled after rolling.
  • perform quenching and tempering heat treatment control the quenching heating temperature to 900°C, hold time for 6h, tempering temperature to 580°C, hold time for 3h, and then air cool to room temperature.
  • Converter smelting is carried out according to the chemical composition shown in Table 1-1 and Table 1-2.
  • the baking temperature of the ingot mold is controlled to be 240°C, and the slow cooling time of the slab is 40h.
  • the casting slab is processed into the finished product size by using the one-fired process: heat the slab to 1220°C, keep it warm for 5 hours, take the slab out of the heating furnace, descale it with high-pressure water, and start rolling.
  • the starting rolling temperature is controlled to 1100°C
  • the final rolling temperature is 950°C
  • the steel product with a specification of ⁇ 75mm is produced, and it is air-cooled after rolling.
  • perform quenching and tempering heat treatment control the quenching heating temperature to 950°C, the holding time is 5h, the tempering temperature is 480°C, the holding time is 2.5h, and then water-cooled to room temperature.
  • Converter smelting is carried out according to the chemical composition shown in Table 1-1 and Table 1-2.
  • the baking temperature of the ingot mold is controlled to be 220°C, and the slow cooling time of the billet is 44h.
  • the casting slab is processed into the finished product size by using the one-fired process: the slab is heated to 1160°C, kept for 11 hours, and the slab is taken out of the heating furnace and descaled by high-pressure water before rolling, and the starting rolling temperature is controlled at 1060°C, the final rolling temperature is 920°C, and the steel product with a specification of ⁇ 110mm is produced, and air-cooled after rolling.
  • perform quenching and tempering heat treatment control the quenching heating temperature to 980°C, the holding time is 3h, the tempering temperature is 550°C, the holding time is 3.5h, and then water-cooled to room temperature.
  • Converter smelting is carried out according to the chemical composition shown in Table 1-1 and Table 1-2.
  • the baking temperature of the ingot mold is controlled to be 270°C, and the slow cooling time of the slab is 42h.
  • the casting slab is processed into the finished product size by the second-fire process; firstly, the slab is heated to 1190°C, kept for 9 hours, and the slab is taken out of the heating furnace and descaled by high-pressure water before rolling, and the rolling temperature is controlled.
  • the final rolling temperature is 1080°C
  • the final rolling temperature is 960°C
  • the intermediate billet with a size of 220 ⁇ 220mm is obtained; the obtained intermediate billet is heated to 1190°C, kept for 4 hours, and rolled out after being descaled by high-pressure water, and the rolling is controlled.
  • the temperature is 1080°C
  • the final rolling temperature is 860°C to produce a steel product with a specification of ⁇ 26mm, which is air-cooled after rolling.
  • perform quenching and tempering heat treatment control the quenching heating temperature to 860 ° C, the holding time is 2 h, the tempering temperature is 500 ° C, the holding time is 1 h, and then air cool to room temperature.
  • Converter smelting is carried out according to the chemical composition shown in Table 1-1 and Table 1-2. After LF refining and RH vacuum treatment, it is cast into billets by die casting. During die casting, the baking temperature of the ingot mold is controlled to be 300°C, and the slow cooling time of the billet is 38h.
  • the casting slab is processed into a finished product size by using the second-firing process: heat the slab to 1210°C and keep it warm for 7 hours, and then take the slab out of the heating furnace and descale it with high-pressure water before rolling, and control the rolling temperature
  • the final rolling temperature is 1120°C
  • the final rolling temperature is 990°C
  • the intermediate billet with a size of 250 ⁇ 250mm is obtained; then the obtained intermediate billet is heated to 1200°C, kept for 3 hours, and rolled out after being descaled by high-pressure water, and the rolling is controlled.
  • the rolling temperature is 1100°C
  • the final rolling temperature is 900°C to produce a steel product with a specification of ⁇ 48mm, which is air-cooled after rolling.
  • perform quenching and tempering heat treatment control the quenching heating temperature to 930°C, the holding time is 3h, the tempering temperature is 460°C, the holding time is 2.5h, and then water-cooled to room temperature.
  • the steel products of Comparative Examples 1-3 belong to finished steel products from different manufacturers, and its processing technology is different from the manufacturing process adopted in Examples 1-10, and the steel products used in Comparative Examples 1-3 See Table 2-1 and Table 2-2 for specific process parameters.
  • Table 2-1 and Table 2-2 list the specific process parameters of the steel products of Examples 1-10 and Comparative Examples 1-3 in the above process steps.
  • Impact test According to the national standard GB/T 2975-2018, the steel materials of each embodiment and comparative example were sampled to make impact samples. According to the national standard GB/T 229-2020, the impact performance of the impact samples was tested, and the Charpy impact energy A kv at room temperature and the Charpy impact energy A kv at -20°C were measured for the steel materials of Examples 1-10 and Comparative Examples 1-3. Xia's impact energy A kv .
  • Table 3 lists the performance parameters of the steel materials of Examples 1-10 and Comparative Examples 1-3.
  • the steel products of Examples 1-10 of the present invention have excellent comprehensive properties: the yield strength R p0.2 of the steel products of Examples 1-10 is between 1125-1300MPa, and the tensile strength R m is between 1277 Between -1440MPa, the elongation A is between 14-18.5%, the reduction of area Z is between 52-68%, the Charpy impact energy A kv at room temperature is between 85-125J, and the Charpy impact energy at -20°C is between 85-125J. His impact energy A kv is between 76-112J.
  • the element content ratio (12 ⁇ C+0.3 ⁇ Mn+Ni)/(Cr+2Mo+2Si) in the steel of Comparative Example 1 is also lower than that of Examples 1-10 of the present invention, and the mechanical properties and impact energy are also lower than those of the embodiment. Example 1-10.
  • the strength of the steel of Comparative Example 3 is far lower than that of Examples 1-10 of the present invention, and the weather resistance index is also lower than that of the steels of Examples 1-10 of the present invention. This shows that compared with Comparative Example 3, the steel materials of Examples 1-10 of the present invention have significantly improved strength and weather resistance.
  • the present invention obtains steel with excellent performance through reasonable chemical composition design and combined with optimized technology.
  • the steel of the invention has excellent comprehensive properties, and has high strength, excellent ductility-plastic matching, excellent welding performance and weather resistance.
  • the steel of the present invention can be made into high-strength weather-resistant structural parts and high-performance industrial chains such as mining chains and mooring chains.
  • the problems existing in the existing steel materials affect the service life due to the mismatch of strength, toughness, plasticity, welding performance and weather resistance.
  • Fig. 1 is the microstructure photograph of the steel material of embodiment 1 under the microscope of 5000 times.
  • the microstructure of the steel of Example 1 that has completed the heat treatment process of quenching and tempering is: tempered martensite+tempered bainite+carbides dispersedly distributed between lamellar layers . It can be seen that after the present invention optimizes the composition ratio of the steel, combined with appropriate quenching and tempering heat treatment processes, it can obtain carbides dispersedly distributed in the thin martensitic tissue sheets, which can improve the steel's Toughness and plasticity, so that the steel in Example 1 has excellent comprehensive mechanical properties.

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Abstract

本发明公开了一种钢材，除90质量％以上的Fe和不可避免的杂质之外，所述钢材还含有以质量百分比计的如下化学元素：C：0.22-0.33％，Si：0.1-1.0％，Mn：0.3-1.5％，Cr：0.2-1.6％，Ni：2.2-3.8％，Mo：0.1-0.7％，Cu：0.02-0.3％，Al：0.01-0.045％，V：0.01-0.25％，N≤0.013％。本发明还公开了制造上述钢材的方法，包括：(1)冶炼和铸造；(2)锻造或轧制：采用一火成材工艺或二火成材工艺将铸坯加工为成品尺寸；(3)淬火和回火：淬火加热温度为860-1000℃，保温时间为2-6h，淬火后水冷；回火温度为400-600℃，保温时间为1-4h，回火后空冷至室温。本发明的钢材具备高强度，同时还具有良好的韧塑性匹配和优异的耐候性能，应用前景良好。

Description

一种具有优良耐候性能的高强度钢材及其制造方法 技术领域
本发明涉及一种钢材及其制造方法，尤其涉及一种高强度耐候钢及其制造方法。
背景技术
耐候钢是一类在大气中具有良好耐蚀性的低合金高强度钢。一般而言，耐候钢的耐候性是普通碳素钢的2倍以上。耐候钢性能优异，应用前景广泛，常用于制造各种暴露于大气中使用的高强度结构件，可以延长高强度结构件的使用寿命。
当前，国家标准“GB/T4171-2008”耐候结构钢中强度最高的耐候钢牌号为Q550NH，其化学成分为C≤0.16％；Si≤0.65％；Mn≤2.0％；P≤0.025％；S≤0.030％；Cu：0.20-0.55％；Cr：0.30-1.25％；Ni：0.12-0.65％，钢材的屈服强度≥550MPa，抗拉强度为620-780MPa，断后伸长率≥16％。
然而，随着近年来国内节能环保及相关行业轻量化要求，市场对于耐候钢的强度和耐候性能提出了新的需求，此种钢材已经渐渐难以满足当前市场需求。因此，目前亟需开发出一种更高强度的耐候钢新产品。
中国专利文献CN103266274B(公告日为2015年12月2日，名称为“一种超高强度冷轧耐候钢板及其制造方法”)公开了一种高强度冷轧耐候钢板，其化学元素质量百分配比为：C：0.05-0.16％；Mn：1.00-2.20％；Al：0.02-0.06％；Cu：0.20-0.40％；Cr：0.40-0.60％；Ti：0.015-0.035wt％；P≤0.03％；且满足0.19％＜C+Mn/16＜0.23％；余量为Fe和其他不可避免的杂质。该技术方案通过冶炼、加热保温、热轧、卷取、酸洗、冷轧、连续退火及平整的工艺流程，可以获得屈服强度＞700MPa且抗拉强度＞1000MPa的钢材。
中国专利文献CN111378896A(公开日为2020年7月7日，名称为“一种高强度耐候型建筑桥梁用钢板及其制造方法”)公开了一种高强度耐候型建筑桥梁用钢板，其化学成分为：C：0.03-0.09％，Si：0.05％-0.55％，Mn：1.10％-2.00％， P≤0.012％，S≤0.003％，Cr：0.50％-1.00％，Cu：0.30％-0.50％，Ni：0.20％-1.20％，Als：0.015％-0.050，Ti：0.002％-0.030％，V：0.002％-0.08％，Mo：0.01％-0.80％，B：0.0001％-0.0025％，CEV≤0.65％，Pcm≤0.28，耐大气腐蚀性指数I≥6.5，余量为Fe。采用该专利文献制得的钢材的屈服强度≥620MPa，抗拉强度在730MPa-850MPa之间，断后伸长率A≥16％，-40℃冲击功KV2≥120J。
中国专利文献CN106756476A(公开日为2017年5月31日，名称为“高强度耐高湿热海洋大气环境用耐候钢及制备方法”)公开了一种高强度耐高湿热海洋大气环境用耐候钢，其化学成分(wt％)为C：0.01-0.03、Si：0.30-0.50、Mn：0.60-0.80、Cu：0.90-1.10、Ni：2.80-3.20、Mo：0.20-0.40、Sn：0.25-0.35、Sb：0.05-0.10、Cr≤0.03、Nb≤0.02、P≤0.01、S≤0.01、RE：0.03-0.05，其余为Fe。该专利文献在Cu-Ni-Mo合金体系基础上，通过添加Sn、Sb、Nb、RE等多种微合金元素，大幅降低了耐候钢中Cr含量，其制备的钢材的屈服强度≥650MPa且抗拉强度≥750MPa，30℃半尺寸冲击功达到65J。
根据上述专利文献可以看出，现有的高强度耐候钢产品的屈服强度大多为600-800MPa，很少有屈服强度超过1000MPa的高强度耐候钢产品。
基于此，有必要开发一种新型耐候钢材，该耐候钢材具备1000MPa以上的高强度，同时还具有良好的韧塑性匹配以及优异的耐候性能。此种新型耐候钢能够用于制备高性能工业链条，可以很好地解决现有钢材存在的因强度、韧塑性、耐候性不匹配而影响使用寿命的问题。
发明内容
本发明的目的之一在于提供一种具有优良耐候性能的高强度钢材，该钢材具备1000MPa以上的高强度，同时还具有良好的韧塑性匹配以及优异的耐候性能，其特别适用于制造高强度耐候性结构件、矿用、系泊等用途的工业链条产品，可以广泛应用于工程机械、矿山、海洋工程等具有较多腐蚀介质的场合。
为了实现上述目的，本发明提出了一种钢材，其中除90质量％以上的Fe和不可避免的杂质之外，所述钢材还含有以质量百分比计的如下化学元素：
C：0.22-0.33％，Si：0.1-1.0％，Mn：0.3-1.5％，Cr：0.2-1.6％，Ni：2.2-3.8％，Mo：0.1-0.7％，Cu：0.02-0.3％，Al：0.01-0.045％，V：0.01-0.25％，N≤0.013％。
优选地，本发明的钢材由以质量百分比计的如下化学元素组成：
C：0.22-0.33％，Si：0.1-1.0％，Mn：0.3-1.5％，Cr：0.2-1.6％，Ni：2.2-3.8％，Mo：0.1-0.7％，Cu：0.02-0.3％，Al：0.01-0.045％，V：0.01-0.25％，N≤0.013％；余量为Fe和不可避免的杂质。
在本发明的钢材中，各化学元素的设计原理如下所述：
C：在本发明的钢材中，C是确保钢材强度所必须的元素。提高钢材中的C含量将增加钢材的非平衡组织转变能力，从而显著提高钢材的强度。此外，在本发明中，可以通过淬火和回火热处理工艺抑制钢材中C元素的扩散形成切变型的马氏体相变，从而显著提高钢材的强度。
然而，本发明的钢材中C元素含量不宜过高，过高的C含量会对钢材的塑性和韧性产生不利影响，而且会显著增加材料的碳当量，恶化钢材的焊接性能。基于此，本发明的钢材中，C元素含量被控制在0.22-0.33％之间。
Si：在本发明的钢材中，Si元素可以固溶在钢材中以起到固溶强化的作用。Si元素能够显著提高钢材的屈服强度、疲劳强度和硬度。但需要注意的是，Si在渗碳体中的溶解度很低，钢材中Si元素含量不宜过高。当钢材中Si元素含量过高时，不仅会形成无碳化物的贝氏体组织，同时还会增加钢材的脆性。基于此，本发明的钢材中，Si元素含量被控制在0.1-1.0％之间。
Mn：在本发明的钢材中，Mn元素可以提高钢材中奥氏体的稳定性，同时还能提高钢材的淬透性。此外，Mn还可以通过固溶强化来提高钢材中马氏体的强度，进而提高钢材的强度。但需要注意的是，钢材中Mn元素含量不宜过高。当钢材中Mn元素含量过高时，在淬火加热时会使得奥氏体晶粒容易长大，促进有害元素在晶界偏聚。基于此，本发明的钢材中，Mn元素含量被控制在0.3-1.5％之间。
Cr：在本发明的钢材中，添加适量的Cr元素可以提高钢材的淬透性，并具有二次硬化的作用，其可以形成硬化的马氏体组织，有利于提高钢材的强度。此外，Cr的碳化物可以起到减慢焊接接头处热影响区晶粒长大的作用，对于钢材的焊接非常有利。钢材中添加适量的Cr和Ni元素，有利于提高钢材的耐候性能。但是，钢材中Cr元素含量不宜过高。当钢材中Cr元素含量过高时，会生成大量碳化物，并在晶界聚集，进而降低材料的韧性、显著增加碳当量和恶化钢材的焊接性能。基于此，本发明的钢材中，Cr元素含量被控制在0.2-1.6％之间。
Ni：在本发明的钢材中，Ni是奥氏体形成元素。作为主要强化元素之一，Ni能够以固溶形式存在于钢材中，并能够与铁无限固溶。此外，当Ni元素与Cr元素配合使用时，还可以显著提高钢材的淬透性。
钢材中添加适量的Ni元素可以有效降低共析点的含C量、强化铁素体并细化和增多珠光体，其能够提高钢材的强度而不显著影响钢材的塑性。另外，Ni元素能够提高钢材的疲劳抗力，减小钢材对缺口的敏感性，降低钢材的低温脆化转变温度，改善钢材的冲击韧性。Ni元素可以提高钢材强度，同时对钢材的韧性、塑性和其他性能的损害较其他合金元素的影响小。
基于此，为了发挥Ni元素的有益效果、同时尽量降低钢材成本，本发明的钢材中，Ni元素含量被控制在2.2-3.8％之间。
Mo：在本发明的钢材中，Mo元素主要以固溶形式存在于钢材中。Mo能够起到固溶强化效果，有利于提高钢材的淬透性，使钢材在淬火过程中形成马氏体。但是，钢材中Mo元素含量不宜过高。当钢材中Mo元素过高时，会显著提高材料的碳当量，从而不利于钢材的焊接性能。此外，Mo是贵重合金元素，加入过量的Mo元素会导致合金成本上升。基于此，本发明的钢材中，Mo元素含量被控制在0.1-0.7％之间。
Cu：在本发明的钢材中，添加适量的Cu元素可以显著提高钢材的耐候性能，降低钢材的氢致裂纹敏感性。但需要注意的是，过高的Cu含量不利于钢材的焊接性能，而且也易于产生铜脆现象，恶化钢材的表面性能。因此，本发明的钢材中，Cu元素的含量被控制在0.02-0.3％之间。
Al：在本发明的钢材中，Al的主要作用是脱氧和固氮，A1与N结合形成的A1N可以有效地细化晶粒。但需要注意的是，钢材中Al元素含量不宜过高。当钢材中Al元素含量过高时，会影响钢材的浇注性能，而且会损害钢材的韧性。基于此，本发明的钢材中，Al元素含量被控制在0.01-0.045％之间。
V：在本发明的钢材中，V作为强碳化物形成元素，能以弥散析出的形式显著提高钢材的强度。但需要注意的是，当钢材中V元素的添加量过高时，将降低钢材的韧性和焊接性能。基于此，本发明的钢材中，V元素含量被控制在0.01-0.25％之间。
N：在本发明的钢材中，N为奥氏体形成元素，同时也是MX型析出物形成元素。为了避免N元素在钢材中富集，钢材中不宜添加过多的N。因此，必 须严格控制N元素的含量，本发明的钢材中，N元素含量被控制为不超过0.013％。
在本发明中，发明人通过对钢材的组成以及钢材中各化学元素含量进行合理设计，并利用各合金元素本身及它们之间的相互作用对微观组织和最终性能的影响，来精确地控制本发明钢材的显微组织，进而确保本发明的钢材中形成回火马氏体+回火贝氏体+片层间弥散分布的碳化物的混合多相组织。利用这一微观组织，可以使本发明的钢材获得高强度和良好的韧塑性匹配，同时具有良好的耐候性、耐磨性及抗疲劳性能。
优选地，本发明的钢材还含有Nb和/或Ti，其中0＜Nb≤0.04％，0＜Ti≤0.03％。
Nb：Nb为强碳化物形成元素。添加适量的Nb到钢材中，不仅可以起到对钢材再结晶的抑制作用，还可以有效细化晶粒。但需要注意的是，当钢材中Nb元素含量过高时，在高温回火条件下会形成粗大的NbC颗粒，恶化钢材的低温冲击功。因此，在本发明中，优选地控制添加的Nb元素含量满足：0＜Nb≤0.04％。
Ti：钢材中添加适量的Ti元素可以形成细小的Ti(C,N)析出相。Ti(C,N)在钢材进行焊接过程中可以有效防止组织粗化，提高焊缝焊接质量。但是，钢材中Ti元素含量不宜过高。当钢材中Ti元素含量过高时，在冶炼过程中会形成粗大的带棱角的TiN颗粒，降低钢材的冲击韧性和疲劳性能。因此，在本发明中，优选地控制添加的Ti元素含量满足：0＜Ti≤0.03％。
优选地，在本发明的钢材中，元素C、Mn、Ni、Cr、Mo和Si以质量百分比计的含量还满足下式：2.5≤(12×C+0.3×Mn+Ni)/(Cr+2Mo+2Si)≤3.2，式中元素符号代表对应元素的质量百分比含量的百分号之前的数值。
本发明人通过大量研究发现，当钢材中的主要强化元素C、Mn、Ni、Cr、Mo和Si的含量被控制为满足2.5≤(12×C+0.3×Mn+Ni)/(Cr+2Mo+2Si)≤3.2时，可以进一步获得最佳的强度和韧塑性匹配。
当钢材中(12×C+0.3×Mn+Ni)/(Cr+2Mo+2Si)比值小于2.5时，钢材的奥氏体区相对减小，奥氏体稳定性降低，易于在淬火过程中形成的贝氏体的含量相对较高，马氏体含量相对较低，在回火过程中片层间析出的碳化物颗粒较大且数量较少，从而难以获得最佳的强度和韧塑性匹配。
当钢材中(12×C+0.3×Mn+Ni)/(Cr+2Mo+2Si)比值大于3.2时，钢材的 奥氏体区相对扩大，奥氏体稳定性提高，淬火回火热处理时扩散性相变得到抑制，淬火过程中得到的马氏体组织片层间距较大，在回火过程中片层间析出的弥散碳化物数量较多，钢材的强度较高，韧塑性相对较低，从而难以获得最佳的强度和韧塑性匹配。
本发明中，P元素、S元素和O元素均为钢材中的杂质元素，在技术条件允许情况下，为了获得性能更好、质量更优的钢材，应尽可能降低材料中杂质元素的含量。
优选地，在本发明的钢材中，不可避免的杂质以质量百分比计的含量满足：P≤0.015％，S≤0.01％，O≤0.002％。
在本发明的钢材中，P元素和S元素均是钢材中不可避免的有害杂质元素，且均会恶化钢材的性能。虽然P可以提高钢材的耐候性能，但总体而言其副作用更大。因此，在本发明中控制P元素满足：P≤0.015％，控制S元素满足：S≤0.01％。
在本发明中，杂质元素O可以与钢材中的Al等脱氧元素形成氧化物以及复合物夹杂，不利于钢材的性能。因此，在本发明中控制O元素满足：O≤0.0015％。
在一些其他的实施方式中，钢材中可能存在其它有害元素，例如As、Pb、Sn、Sb、Bi等。在国家法律法规和标准的要求下，应尽可能降低这些有害元素的含量。
优选地，本发明的钢材的耐候指数I≥10.0，其中，I＝26.01×Cu+3.88×Ni+1.20×Cr+1.49×Si+17.28×P-7.29×Cu×Ni-9.10×Ni×P-33.39×Cu 2，式中元素符号代表对应元素质量百分比含量的百分号之前的数值。
本发明的钢材中添加了较多的Ni、Mn、Cu元素，可以有效提高钢材的耐候指数I，从而确保钢材在具有较高的强韧性基础上，还具有良好的耐候性能。通过将本发明钢材的耐候指数I控制为I≥10.0，可确保钢材获得良好的耐环境腐蚀能力，从而进一步确保本发明的钢材在使用过程中不容易发生腐蚀断裂，提高使用寿命。
优选地，本发明的钢材的微观组织为回火马氏体+回火贝氏体+片层间弥散分布的碳化物。
优选地，本发明的钢材的性能满足：屈服强度R p0.2≥1100MPa，抗拉强度 R m≥1250MPa，延伸率A≥14％，断面收缩率Z≥50％，室温下的夏氏冲击功A kv≥80J，-20℃下的夏氏冲击功A kv≥70J。
本发明的另一目的在于提供上述钢材的制造方法。本发明的制造方法工艺简单，并且所获得的钢材具备优良的高强韧性以及良好的耐候能力，其屈服强度R p0.2≥1100MPa，抗拉强度R m≥1250MPa，延伸率A≥14％，断面收缩率Z≥50％，室温下的夏氏冲击功A kv≥80J，-20℃下的夏氏冲击功A kv≥70J。
为了实现上述目的，本发明提供了制造上述钢材的方法，所述方法依次包括如下步骤：
(1)对钢水进行冶炼和铸造，制得铸坯；
(2)对铸坯进行锻造或轧制：采用一火成材工艺或二火成材工艺将铸坯加工为成品尺寸；
(3)进行淬火和回火，制得成品钢材：在淬火过程中，加热温度为860-1000℃，保温时间为2-6h，在淬火后进行水冷；然后进行回火，在回火过程中，回火温度为400-600℃，保温时间为1-4h，在回火后空冷至室温，制得成品钢材。
本发明人深入研究了钢材的组成中C、Si、Mn、Ni、Cr、Mo等主要强化元素在淬火和回火热处理中的作用。
本发明人通过对合金元素配比进行合理设计并配合优化设计的淬火和回火热处理工艺，利用各合金元素本身及它们之间的相互作用对淬火和回火热处理后钢材微观组织的影响，可以精确地控制本发明钢材的显微组织。经淬火和回火热处理后，形成了回火马氏体、回火贝氏体及片层间弥散碳化物的混合多相组织，从而确保本发明的钢材的性能。
本发明人对步骤(3)的淬火和回火的热处理进行了优化设计。在淬火过程中，钢材在860-1000℃的加热温度下保温2-6h，使钢材全奥氏体化。钢材中的Cr、Mo、Nb、V、Ti、Al等元素的碳化物或氮化物颗粒部分溶解到奥氏体中，未溶解的碳化物和碳化物粒子继续钉扎奥氏体晶界，抑制奥氏体晶粒长大。通过对淬火过程中的工艺参数进行优化设计，可以使钢材中形成更细小的马氏体、贝氏体等非平衡组织，由此确保本发明的钢材具有较高的强度。
在回火过程中，在400-600℃的回火温度下保温1-4h。在此过程中，钢材在淬火过程中形成的高密度位错部分湮灭，钢材中非平衡组织中固溶的过饱和 C、Cr、Mo元素能够再次以碳化物的形式在马氏体或贝氏体的片层中间析出。此时，由于析出时的温度较低，析出粒子不易长大，从而使析出粒子更加细小弥散。
由此，在本发明的淬火和回火热处理中，位错湮灭以及碳化物和氮化物的析出会导致钢材的内应力减小，塑性和韧性得到改善，从而确保钢材具有较高强度和较好塑性、韧性匹配。
优选地，在本发明所述的制造方法中，在步骤(1)中，采用模铸或连铸将经冶炼的钢水浇铸成铸坯。在采用模铸的情况下，锭模烘烤温度≥200℃；在采用连铸的情况下，中间包烘烤温度≥1100℃，烘烤时间≥3.5h。
优选地，在本发明上述制造方法的步骤(1)中，可以用电炉或转炉对钢水进行冶炼，并经过LF及VD或RH真空精炼处理，在化学成分满足本发明设计要求后可以出钢进行铸造。在铸造过程中，可以采用模铸或连铸工艺将精炼后的钢水浇铸成铸坯；在采用模铸的情况下，可以控制锭模烘烤温度≥200℃；在采用连铸的情况下，可以控制中间包烘烤温度≥1100℃，烘烤时间≥3.5h；优选地控制铸坯热送或下线缓冷时间≥24h。
优选地，在本发明所述的制造方法中，在步骤(2)中，在采用一火成材工艺的情况下，将铸坯直接轧制或锻造为成品尺寸，其中铸坯加热温度为1150-1250℃，保温时间为3-12h，开轧温度或开锻温度≥1050℃，终轧温度或终锻温度≥900℃。
优选地，在本发明所述的制造方法中，在步骤(2)中，在采用二火成材工艺的情况下，先将铸坯锻造或轧制成中间坯，再将中间坯锻造或轧制为成品尺寸，其中铸坯加热温度为1150-1250℃，保温时间为3-12h，开轧温度或开锻温度≥1050℃，终轧温度或终锻温度≥950℃；中间坯的加热温度为1120-1200℃，保温时间为3-10h，中间坯的开轧温度≥1050℃，中间坯的终轧温度≥860℃。
优选地，在本发明所述制造方法中，在步骤(2)中，在锻造或轧制过程中，可以采用一火成材工艺或二火成材工艺将铸坯加工为成品尺寸，成品尺寸规格范围可以为Φ26-150mm。
在本文中，一火成材工艺指在铸坯的锻造或轧制过程中，直接将铸坯锻造或轧制为最终成品尺寸；二火成材工艺指先将铸坯锻造或轧制为预定的中间坯尺寸，再将中间坯锻造或轧制为最终成品尺寸。
需要说明的是，在本发明的步骤(2)中，无论是采用一火成材工艺还是二火成材工艺，均需要在1150-1250℃下对铸坯进行加热，铸坯在加热过程中会发生析出相溶解和奥氏体晶粒长大的现象。
铸坯中形成的Cr、Mo、Nb、V、Ti、Al等的析出物会在高温加热过程中部分或者全部溶解在奥氏体中，未溶解的析出物会钉扎奥氏体晶界，并抑制奥氏体晶粒的过度长大。此时，在该较高加热温度(即1150-1250℃)下保温一定时间，有利于钢材中偏析元素的扩散，使铸坯中的元素分布更加均匀。
相应地，在轧制及冷却过程中，随着温度的降低，钢材中的Ti、Nb、Al等元素会再次从钢材中析出，形成细小弥散分布的颗粒，抑制再结晶晶粒的长大，细化组织。固溶在钢材中的Cr、Mo等合金元素，在冷却过程中会抑制扩散型相变，形成中低温转变组织例如贝氏体和马氏体等，提高钢材的强度。
此外，需要注意的是，在上述步骤(2)中，在锻造或轧制开始前，可以先控制铸坯出加热炉并进行高压水除鳞；在锻造或轧制后，可以采用空冷或缓冷进行冷却。
相较于现有技术，本发明的钢材及其制造方法具有如下所述的优点以及有益效果：
本发明对钢材中的C、Si、Mn、Ni、Cr、Mo等主要强化元素进行了优化设计，通过采用合理的元素配比并结合淬火和回火的热处理工艺，可以控制本发明钢材在淬火冷却过程中的马氏体、贝氏体组织转变，以及回火过程中的碳化物析出，进而控制钢材的微观组织为回火马氏体+回火贝氏体+片层间弥散分布的碳化物，以确保本发明的钢材获得最佳的强度和韧塑性匹配。
此外，需要说明的是，在本发明的一些优选实施方式中，可以进一步地提高钢材的耐候指数I的数值，以使钢材获得更优的耐候性能，进而大幅提高钢材在恶劣环境下的使用寿命。
本发明的钢材的化学成分以及工艺设计合理，工艺窗口宽松，可以实现批量商业化生产。
本发明的钢材具备优良的高强韧性以及良好的耐候能力，其可以制成高强度耐候性结构件以及矿用链、系泊链等高性能工业链条，并广泛应用于工程机械、矿山及海洋工程等需要高强韧钢材的场合。
附图说明
图1为实施例1的钢材在5000倍显微镜下的微观组织照片。
具体实施方式
下面将结合具体的实施例对本发明的钢材及其制造方法做进一步的解释和说明，然而该解释和说明并不对本发明的技术方案构成不当限定。
实施例1-10和比较例1-3
实施例1-10的钢材采用如下步骤制得：
(1)按照下表1-1和表1-2所示的化学成分，对钢水进行冶炼和连铸，制得铸坯。冶炼采用电炉或转炉冶炼，并经过LF精炼及VD或RH真空处理，成分满足要求后出钢。而后采用模铸或连铸将经冶炼的钢水浇铸成铸坯，控制铸坯热送或下线缓冷时间≥24h：在采用模铸的情况下，控制锭模烘烤温度≥200℃；在采用连铸的情况下，控制中间包烘烤温度≥1100℃，控制烘烤时间≥3.5h。
(2)对铸坯进行锻造或轧制：采用一火成材工艺或二火成材工艺将铸坯加工为成品尺寸，成品尺寸规格范围为Φ26-150mm。
其中，在采用一火成材工艺的情况下，控制铸坯加热温度为1150-1250℃，保温时间为3-12h，开轧温度或开锻温度≥1050℃，终轧温度或终锻温度≥900℃。在采用二火成材工艺的情况下，控制铸坯加热温度为1150-1250℃，保温时间为3-12h，开轧温度或开锻温度≥1050℃，终轧温度或终锻温度≥950℃；中间坯加热温度为1120-1200℃，保温时间为3-10h，中间坯开轧温度≥1050℃，中间坯终轧温度≥860℃。
(3)进行淬火和回火，制得成品钢材：其中在淬火过程中，加热温度为860-1000℃，保温时间为2-6h，在淬火后进行水冷；然后进行回火，在回火过程中，回火温度为400-600℃，保温时间为1-4h，在回火后将钢材空冷至室温，由此制得成品钢材。
在本发明中，实施例1-10的钢材的化学成分设计以及相关工艺均满足本发明设计规范要求。
相比之下，比较例1-3的钢材属于来自不同厂家的成品钢材，其化学成分参见下表1-1和表1-2。比较例1-3的钢材虽然也采用上述工艺流程步骤制得， 但比较例1-3的化学成分和制造工艺参数中的至少一种不满足本发明的要求。
表1-1和表1-2列出了实施例1-10和比较例1-3的钢材的化学元素组成。
表1-1(wt％，余量为Fe和除P、S和O之外的其他不可避免的杂质)
编号 C Si Mn P S Cr Ni Mo Cu Al Nb V Ti N O
实施例1 0.24 0.24 1.21 0.011 0.006 0.41 3.78 0.67 0.18 0.021 0.021 0.05 0.007 0.0071 0.0011
实施例2 0.225 0.47 0.76 0.005 0.004 0.67 2.57 0.23 0.11 0.011 0.038 0.21 0.026 0.0117 0.0013
实施例3 0.25 0.12 1.42 0.009 0.003 0.85 2.98 0.58 0.02 0.044 - 0.08 0.004 0.0098 0.0009
实施例4 0.3 0.78 0.58 0.008 0.005 0.33 3.35 0.41 0.22 0.015 0.013 0.18 0.011 0.0055 0.0008
实施例5 0.31 0.55 0.32 0.012 0.002 0.55 2.25 0.34 0.28 0.032 0.031 0.25 0.019 0.0039 0.0012
实施例6 0.27 0.96 1.05 0.01 0.002 0.21 3.52 0.12 0.08 0.025 0.028 0.12 0.015 0.0106 0.0015
实施例7 0.33 0.3 0.47 0.013 0.009 0.95 3.03 0.61 0.06 0.018 0.035 0.01 - 0.0129 0.0005
实施例8 0.3 0.4 0.88 0.006 0.01 1.31 3.47 0.18 0.29 0.028 0.009 0.02 0.013 0.0123 0.0007
实施例9 0.24 0.18 1.47 0.015 0.008 1.15 3.12 0.29 0.25 0.039 0.017 0.15 0.029 0.0085 0.0016
实施例10 0.29 0.21 0.65 0.007 0.007 1.57 3.69 0.47 0.15 0.035 0.024 0.09 0.023 0.0064 0.0019
比较例1 0.25 0.15 1.3 0.008 0.006 0.55 0.98 0.56 0.11 0.027 0.003 0.005 0.007 0.0086 0.0012
比较例2 0.245 0.8 2 0.015 0.002 0.2 3.4 0.9 0.2 0.03 0.08 0.008 0.005 0.01 0.0015
比较例3 0.054 0.35 0.63 0.004 0.003 1.94 0.96 - 0.32 0.04 - 0.026 - - -
表1-2
编号 (12×C+0.3×Mn+Ni)/(Cr+2Mo+2Si) I
实施例1 3.15 13.97
实施例2 2.66 11.85
实施例3 2.85 12.75
实施例4 2.63 13.18
实施例5 2.60 10.23
实施例6 2.99 15.01
实施例7 2.57 13.33
实施例8 2.97 12.93
实施例9 3.08 12.31
实施例10 2.51 15.52
比较例1 2.22 6.43
比较例2 1.93 13.33
比较例3 0.68 9.25
注：I＝26.01×Cu+3.88×Ni+1.20×Cr+1.49×Si+17.28×P-7.29×Cu×Ni-9.10×Ni×P-33.39×Cu 2；上表1-2中，式中化学元素符号各自代入对应元素的质量百分比含量的百分号之前的数值。
实施例1-10的钢材的具体生产工艺操作如下所述：
实施例1
按表1-1和表1-2所示的化学成分进行电炉冶炼，经LF精炼和RH真空处理后浇铸成连铸坯。在连铸时，控制中间包烘烤温度为1150℃，烘烤时间为5h；控制铸坯缓冷时间为35h。本实施例中采用二火成材工艺将铸坯加工为成品尺寸：首先将连铸坯加热至1150℃，并保温12h，并将铸坯出加热炉经高压水除鳞后开始轧制，控制开轧温度为1090℃，终轧温度为950℃，制得尺寸为280×280mm的中间坯；然后将所得的中间坯加热至1120℃，并保温10h，并出炉经高压水除鳞后开始轧制，控制开轧温度为1050℃，控制终轧温度为880℃，制得规格为Φ75mm的钢材，轧制后空冷。而后进行淬火和回火热处理，控制淬火加热温度为940℃，保温时间为4h，回火温度为450℃，保温时间为3h，然后水冷至室温。
实施例2
按表1-1和表1-2所示的化学成分进行电炉冶炼，经LF精炼和RH真空处理后浇铸成连铸坯。在连铸时，控制中间包烘烤温度为1100℃，烘烤时间为6h；控制铸坯缓冷时间为30h。本实施例中采用二火成材工艺将铸坯加工为成品尺寸：首先将连铸坯加热至1220℃，并保温4h，并将连铸坯出加热炉经高压水除鳞后开始轧制，控制开轧温度为1120℃，终轧温度为980℃，制得尺寸为260×260mm的中间坯；然后将所得的中间坯加热至1130℃，并保温6h，并出炉经高压水除鳞后开始轧制，控制开轧温度为1060℃，终轧温度为890℃，制得规格为Φ60mm的钢材，轧制后空冷。而后进行淬火和回火热处理，控制淬火加热温度为990℃，保温时间为3h，回火温度为420℃，保温时间为2h，然后空冷至室温。
实施例3
按表1-1和表1-2所示的化学成分进行电炉冶炼，经LF精炼和RH真空处理后浇铸成连铸坯。在连铸时，控制中间包烘烤温度为1250℃，烘烤时间为4.5h，铸坯缓冷时间为28h。本实施例中采用二火成材工艺将连铸坯加工为成品尺寸：首先将连铸坯加热至1240℃，保温3h，并将连铸坯出加热炉经高压水除鳞后开始轧制，控制开轧温度为1110℃，终轧温度为970℃，制得尺寸为220×220mm的中间坯；然后将所得的中间坯加热至1150℃，保温8h，并出炉经高压水除鳞 后开始轧制，控制开轧温度为1075℃，终轧温度为910℃，制得规格为Φ42mm的钢材，轧制后空冷。而后进行淬火和回火热处理，控制淬火加热温度为910℃，保温时间为2.5h，回火温度为530℃，保温时间为1.5h，然后水冷至室温。
实施例4
按表1-1和表1-2所示的化学成分进行电炉冶炼，经LF精炼和VD真空处理后浇铸成连铸坯。在连铸时，控制中间包烘烤温度为1200℃，烘烤时间为3.5h，铸坯缓冷时间为24h。本实施例中采用一火成材工艺将铸坯加工为成品尺寸：将连铸坯加热至1200℃，保温6h，并将连铸坯出加热炉经高压水除鳞后开始轧制，控制开轧温度为1100℃，终轧温度为960℃，制得规格为Φ150mm的钢材，轧制后堆冷。而后进行淬火和回火热处理，控制淬火加热温度为880℃，保温时间为6h，回火温度为570℃，保温时间为4h，然后空冷至室温。
实施例5
按表1-1和表1-2所示的化学成分进行电炉冶炼，经LF精炼和VD真空处理后浇铸成连铸坯。在连铸时，控制中间包烘烤温度为1300℃，烘烤时间为4h，铸坯缓冷时间为26h。本实施例中采用一火成材工艺将铸坯加工为成品尺寸：将连铸坯加热至1170℃，保温8h，并将连铸坯出加热炉经高压水除鳞后开始轧制，控制开轧温度为1070℃，终轧温度为930℃，制得规格为Φ130mm的钢材，轧制后堆冷。而后进行淬火和回火热处理，控制淬火加热温度为960℃，保温时间为5h，回火温度为600℃，保温时间为3h，然后空冷至室温。
实施例6
按表1-1和表1-2所示的化学成分进行转炉冶炼，经LF精炼和RH真空处理后采用模铸浇注成铸坯。在模铸时，控制锭模烘烤温度为200℃，铸坯缓冷时间为48h。本实施例中采用一火成材工艺将铸坯加工为成品尺寸：将铸坯加热至1180℃，保温10h，并将铸坯出加热炉经高压水除鳞后开始轧制，控制开轧温度为1050℃，终轧温度为900℃，制得规格为Φ100mm的钢材，轧后空冷。而后进行淬火和回火热处理，控制淬火加热温度为900℃，保温时间为6h，回火温度为580℃，保温时间为3h，然后空冷至室温。
实施例7
按表1-1和表1-2所示的化学成分进行转炉冶炼，经LF精炼和RH真空处理后采用模铸浇注成铸坯。在模铸时，控制锭模烘烤温度为240℃，铸坯缓冷 时间为40h。本实施例中采用一火成材工艺将铸坯加工为成品尺寸：将铸坯加热至1220℃，保温5h，并将铸坯出加热炉经高压水除鳞后开始轧制，控制开轧温度为1100℃，终轧温度为950℃，制得规格为Φ75mm的钢材，轧后空冷。而后进行淬火和回火热处理，控制淬火加热温度为950℃，保温时间为5h，回火温度为480℃，保温时间为2.5h，然后水冷至室温。
实施例8
按表1-1和表1-2所示的化学成分进行转炉冶炼，经LF精炼和RH真空处理后采用模铸浇注成铸坯。在模铸时，控制锭模烘烤温度为220℃，铸坯缓冷时间为44h。本实施例中采用一火成材工艺将铸坯加工为成品尺寸：将铸坯加热至1160℃，保温11h，并将铸坯出加热炉经高压水除鳞后开始轧制，控制开轧温度为1060℃，终轧温度为920℃，制得规格为Φ110mm的钢材，轧后空冷。而后进行淬火和回火热处理，控制淬火加热温度为980℃，保温时间为3h，回火温度为550℃，保温时间为3.5h，然后水冷至室温。
实施例9
按表1-1和表1-2所示的化学成分进行转炉冶炼，经LF精炼和RH真空处理后采用模铸浇注成铸坯。在模铸时，控制锭模烘烤温度为270℃，铸坯缓冷时间为42h。本实施例中采用二火成材工艺将铸坯加工为成品尺寸；首先将铸坯加热至1190℃，保温9h，并将铸坯出加热炉经高压水除鳞后开始轧制，控制开轧温度为1080℃，终轧温度为960℃，制得尺寸为220×220mm的中间坯；将所得的中间坯加热至1190℃，保温4h，并出炉经高压水除鳞后开始轧制，控制开轧温度为1080℃，终轧温度为860℃，制得规格为Φ26mm的钢材，轧制后空冷。而后进行淬火和回火热处理，控制淬火加热温度为860℃，保温时间为2h，回火温度为500℃，保温时间为1h，然后空冷至室温。
实施例10
按表1-1和表1-2所示的化学成分进行转炉冶炼，经LF精炼和RH真空处理后采用模铸浇注成铸坯。在模铸时，控制锭模烘烤温度为300℃，铸坯缓冷时间为38h。本实施例中采用二火成材工艺将铸坯加工为成品尺寸：将铸坯加热至1210℃，并保温7h，并将铸坯出加热炉经高压水除鳞后开始轧制，控制开轧温度为1120℃，终轧温度为990℃，制得尺寸为250×250mm的中间坯；然后将所得的中间坯加热至1200℃，保温3h，并出炉经高压水除鳞后开始轧制，控制 开轧温度为1100℃，终轧温度为900℃，制得规格为Φ48mm的钢材，轧制后空冷。而后进行淬火和回火热处理，控制淬火加热温度为930℃，保温时间为3h，回火温度为460℃，保温时间为2.5h，然后水冷至室温。
不同于上述实施例1-10的钢材，比较例1-3的钢材属于来自不同厂家的成品钢材，其加工工艺不同于实施例1-10所采用的制造工艺，比较例1-3所采用的具体工艺参数参见下表2-1和表2-2。
表2-1和表2-2列出了实施例1-10和比较例1-3的钢材在上述工艺步骤中的具体工艺参数。
表2-1
Figure PCTCN2022115498-appb-000001
表2-2
Figure PCTCN2022115498-appb-000002
对实施例1-10和比较例1-3的成品钢材的性能进行检测，得到各实施例和比较例的成品钢材的性能参数。
对实施例1-10和比较例1-3的钢材分别进行拉伸试验和冲击性能测试。各实施例和比较例的钢材的测试结果列于表3中。
相关拉伸试验、冲击试验的具体检测手段如下所述：
拉伸试验：按照国家标准GB/T 2975-2018对各实施例和比较例的钢材进行取样以制成拉伸试样。按照GB/T 228.1-2010国家标准对试样进行拉伸性能测试，测得实施例1-10和比较例1-3的钢材的屈服强度R p0.2、抗拉强度R m、延伸率A和断面收缩率Z。
冲击试验：按照国家标准GB/T 2975-2018对各实施例和比较例的钢材进行取样以制成冲击试样。按照国家标准GB/T 229-2020对冲击试样进行冲击性能测试，测得实施例1-10和比较例1-3的钢材在室温下的夏氏冲击功A kv和在-20℃下的夏氏冲击功A kv。
表3列出了实施例1-10和比较例1-3的钢材的性能参数。
表3
Figure PCTCN2022115498-appb-000003
由表3可以看出，本发明实施例1-10的钢材具有优异的综合性能：实施例1-10的钢材的屈服强度R p0.2在1125-1300MPa之间，抗拉强度R m在1277-1440MPa之间，延伸率A在14-18.5％之间，断面收缩率Z在52-68％之间，室温下的夏氏冲击功A kv在85-125J之间，-20℃下的夏氏冲击功A kv在76-112J之间。
相应地，由表3可以看出，本发明所述的实施例1-10的钢材的综合性能明显优于比较例1-3的钢材。
由表1至表3可以看出，比较例1为23MnNiMoCr54钢，耐候指数I＝6.43，明显低于本发明所述实施例1-10的钢材，这说明比较例1的耐候性能劣于本发明实施例。此外，比较例1的钢材中元素含量比值(12×C+0.3×Mn+Ni)/(Cr+2Mo+2Si)也低于本发明实施例1-10，力学性能和冲击功也低于实施例1-10。
比较例2的钢材中添加了较多的Ni、Mn、Mo合金元素，耐候指数I＝13.33，其耐候性能与实施例1-10相当。但是，比较例2的钢材中元素含量比值(12×C+0.3×Mn+Ni)/(Cr+2Mo+2Si)不在本发明的范围内，使得比较例2的钢材尽管具有较高强度，但延伸率和冲击功均低于本发明实施例1-10。这说明与比较例2相比，本发明实施例1-10的钢材具有平衡改进的强度和韧塑性。
比较例3的钢材的强度远低于本发明实施例1-10，同时耐候指数也低于本 发明实施例1-10的钢材。这表明与比较例3相比，本发明实施例1-10的钢材具有显著改进的强度和耐候性能。
综上所述可以看出，本发明通过合理的化学成分设计并结合优化工艺，获得了性能优异的钢材。本发明钢材的综合性能优异，其具有高强度、优良的韧塑性匹配、优异的焊接性能和耐候性能。本发明的钢材可以制成高强度耐候性结构件以及矿用链、系泊链等高性能工业链条，广泛应用于工程机械、矿山及海洋工程等需要高强韧钢材的场合，能够很好地解决现有钢材所存在的因强度、韧塑性、焊接性能及耐候性不匹配而影响使用寿命的问题。
图1为实施例1的钢材在5000倍显微镜下的微观组织照片。
如图1所示，在本发明中，完成淬火和回火的热处理工艺的实施例1的钢材的微观组织为：回火马氏体+回火贝氏体+片层间弥散分布的碳化物。由此可见，本发明在对钢材的成分配比进行优化后，结合适当的淬火和回火热处理工艺，可以在细条状马氏体组织片层中得到弥散分布的碳化物，其可以改善钢材的韧塑性，从而使实施例1的钢材具有优异的综合力学性能。
需要说明的是，本案中各技术特征的组合方式并不限本案权利要求中所记载的组合方式或是具体实施方式所记载的组合方式，本案记载的所有技术特征可以以任何方式进行自由组合或结合，除非相互之间产生矛盾。
还需要注意的是，以上所列举的实施方式仅为本发明的具体实施方式。显然本发明不局限于以上实施例，随之做出的类似变化或变形是本领域技术人员能从本发明公开的内容直接得出或者很容易便联想到的，均应属于本发明的保护范围。

Claims (12)

  1. 一种钢材，其特征在于，除90质量％以上的Fe和不可避免的杂质之外，所述钢材还含有以质量百分比计的如下化学元素：
    C：0.22-0.33％，Si：0.1-1.0％，Mn：0.3-1.5％，Cr：0.2-1.6％，Ni：2.2-3.8％，Mo：0.1-0.7％，Cu：0.02-0.3％，Al：0.01-0.045％，V：0.01-0.25％，N≤0.013％。
  2. 根据权利要求1所述的钢材，其特征在于，所述钢材由以质量百分比计的如下化学元素组成：
    C：0.22-0.33％，Si：0.1-1.0％，Mn：0.3-1.5％，Cr：0.2-1.6％，Ni：2.2-3.8％，Mo：0.1-0.7％，Cu：0.02-0.3％，Al：0.01-0.045％，V：0.01-0.25％，N≤0.013％；余量为Fe和不可避免的杂质。
  3. 根据权利要求1或2所述的钢材，其特征在于，所述钢材还含有Nb和/或Ti，其中0＜Nb≤0.04％，0＜Ti≤0.03％。
  4. 根据权利要求1或2所述的钢材，其特征在于，所述钢材中的元素C、Mn、Ni、Cr、Mo和Si以质量百分比计的含量满足：2.5≤(12×C+0.3×Mn+Ni)/(Cr+2Mo+2Si)≤3.2，式中化学元素符号代表对应元素的质量百分比含量中百分号之前的数值。
  5. 根据权利要求1或2所述的钢材，其特征在于，不可避免的杂质以质量百分比计的含量满足：P≤0.015％，S≤0.01％，O≤0.002％。
  6. 根据权利要求1或2所述的钢材，其特征在于，所述钢材的耐候指数I≥10.0，其中I＝26.01×Cu+3.88×Ni+1.20×Cr+1.49×Si+17.28×P-7.29×Cu×Ni-9.10×Ni×P-33.39×Cu 2，式中化学元素符号代表对应元素的质量百分比含量中百分号之前的数值。
  7. 根据权利要求1或2所述的钢材，其特征在于，所述钢材的微观组织为回火马氏体+回火贝氏体+片层间弥散分布的碳化物。
  8. 根据权利要求1或2所述的钢材，其特征在于，所述钢材的性能满足：屈服强度R p0.2≥1100MPa，抗拉强度R m≥1250MPa，延伸率A≥14％，断面收缩率Z≥50％，室温下的夏氏冲击功A kv≥80J，-20℃下的夏氏冲击功A kv≥70J。
  9. 用于制造权利要求1-8中任一项所述的钢材的方法，其特征在于，所述方 法包括如下步骤：
    (1)对钢水进行冶炼和铸造，制得铸坯；
    (2)对铸坯进行锻造或轧制：采用一火成材工艺或二火成材工艺对铸坯进行锻造或轧制；
    (3)进行淬火和回火，制得成品钢材：在淬火过程中，加热温度为860-1000℃，保温时间为2-6h，在淬火后进行水冷；然后进行回火，在回火过程中，回火温度为400-600℃，保温时间为1-4h，回火后空冷至室温。
  10. 根据权利要求9所述的方法，其特征在于，在步骤(1)中，采用模铸或连铸将经冶炼的钢水浇铸成铸坯，优选对铸坯进行缓冷≥24h；其中在采用模铸的情况下，锭模烘烤温度≥200℃；在采用连铸的情况下，中间包烘烤温度≥1100℃，烘烤时间≥3.5h。
  11. 根据权利要求9所述的方法，其特征在于，在步骤(2)中，采用一火成材工艺将铸坯直接加工为成品尺寸，其中铸坯加热温度为1150-1250℃，保温时间为3-12h；开轧温度或开锻温度≥1050℃，终轧温度或终锻温度≥900℃。
  12. 根据权利要求9所述的方法，其特征在于，在步骤(2)中，采用二火成材工艺，先将铸坯加工成中间坯，然后将中间坯加工为成品尺寸，其中铸坯加热温度为1150-1250℃，保温时间为3-12h，开轧温度或开锻温度≥1050℃，终轧温度或终锻温度≥950℃；中间坯加热温度为1120-1200℃，保温时间为3-10h，中间坯开轧温度≥1050℃，中间坯终轧温度≥860℃。
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