WO2026002017A1 - 具有高烘烤硬化值的1180MPa级钢板及其制造方法 - Google Patents

具有高烘烤硬化值的1180MPa级钢板及其制造方法

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Publication number
WO2026002017A1
WO2026002017A1 PCT/CN2025/103369 CN2025103369W WO2026002017A1 WO 2026002017 A1 WO2026002017 A1 WO 2026002017A1 CN 2025103369 W CN2025103369 W CN 2025103369W WO 2026002017 A1 WO2026002017 A1 WO 2026002017A1
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WO
WIPO (PCT)
Prior art keywords
steel plate
martensite
grade steel
temperature
1180mpa
Prior art date
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Pending
Application number
PCT/CN2025/103369
Other languages
English (en)
French (fr)
Inventor
陈孟
钟勇
李旭飞
王利
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Baoshan Iron and Steel Co Ltd
Original Assignee
Baoshan Iron and Steel Co Ltd
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Filing date
Publication date
Application filed by Baoshan Iron and Steel Co Ltd filed Critical Baoshan Iron and Steel Co Ltd
Publication of WO2026002017A1 publication Critical patent/WO2026002017A1/zh
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • 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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese

Definitions

  • This invention relates to a steel plate and a method for manufacturing the same, and more particularly to a bake-hardening steel plate and a method for manufacturing the same.
  • Baking and painting after parts are formed is a crucial step in automobile manufacturing.
  • baking increases strength, giving the parts a higher strength than the steel sheet itself—this is known as bake hardening.
  • the presence of dislocations and solid solution atoms in the steel sheet is necessary to achieve bake hardening, typically requiring the addition of carbide-forming elements such as Nb, Ti, and Mo.
  • Automotive outer panel steel has relatively low strength, and to achieve deep-drawing performance, a low carbon content needs to be controlled.
  • the presence of bake hardening characteristics improves the strength of the outer panel to a certain extent, creating a good foundation for lightweighting.
  • high-strength steel and ultra-high-strength steel are the main types of steel used in automotive body structures. Due to their more complex composition and microstructure, research and utilization of their bake-hardening properties are limited. Developing products with even higher bake-hardening properties by leveraging the composition and phase transformation characteristics of high-strength steel, without adding precious alloying elements such as Nb, Ti, and Mo, would help further expand the possibilities for high-strength and lightweight automotive body materials.
  • the manufacturing method is as follows: after hot rolling, the steel billet is coiled at 450-750°C, cold rolled with a reduction rate of 75-85% and a final roll reduction ratio of 5-15%, and then the cold-rolled sheet is heated to 830-880°C at a speed of 0-7°C/s and held for 30-80s, and then cooled to 650°C at a speed of 2-10°C/s.
  • This high-strength steel sheet can be used for the manufacture of automotive outer panels, with a strength of around 200MPa.
  • One of the objectives of this invention is to provide a 1180MPa grade steel plate with a high bake hardening value.
  • This steel plate has excellent cold forming ability, bake hardening characteristics and bending performance. It can make full use of the painting and baking process in the manufacturing process of parts to further improve the strength level of parts and improve impact energy absorption performance.
  • the present invention provides a 1180 MPa grade steel plate with a high bake hardening value, which contains Fe and unavoidable impurities, and further contains the following chemical elements in the following mass percentages:
  • the microstructure of the 1180MPa grade steel plate has at least one of martensite, tempered martensite and partitioned martensite, with an area ratio of not less than 50%, and the dislocation density in the martensite, tempered martensite and partitioned martensite is not less than 0.8 ⁇ 10 15 /m 2 .
  • the total area ratio of martensite, tempered martensite, and partitioned martensite in the microstructure of the 1180MPa grade steel plate is 50-80%, such as 54-74%.
  • the dislocation density in the martensite, tempered martensite, and partitioned martensite is 0.80 ⁇ 1015 / m2 - 1.00 ⁇ 1015 / m2 .
  • the martensite generated by the TRIP effect can ensure that the steel plate has high strength while ensuring that the hardness difference between the soft and hard phases decreases after baking and improving the microstructure uniformity, thereby enhancing the bending performance of the steel plate.
  • the martensitic transformation during the quenching process generates a large number of mobile dislocations in the ferrite, while the transformation of the retained austenite during the pre-deformation stage increases the dislocation density in the martensite. Furthermore, the dislocation density increases with the amount of pre-deformation, resulting in a dislocation density in the martensite, tempered martensite, and partitioned martensite of not less than 0.8 ⁇ 1015 / m2 , which improves bake-hardening performance. During the subsequent baking process, these carbon-supersaturated martensites undergo carbon redistribution, carbon atom clusters or Cotillard gas formation, and carbide precipitation, providing ample material for the pinning of density dislocations.
  • the mass percentage of each chemical element is as follows:
  • the balance is Fe and unavoidable impurities.
  • carbon (C) is an austenite forming and stabilizing element, and can extend the incubation temperature before austenite transformation.
  • C is an austenite forming and stabilizing element, and can extend the incubation temperature before austenite transformation.
  • the stability of retained austenite can be improved, helping the retained austenite to exert the TRIP effect and improve the material's strength and elongation.
  • sufficient C is more likely to precipitate and form carbides during the painting and baking process after steel plate deformation, which can pin the movable dislocations generated by pre-deformation and increase the bake hardening value.
  • the mass percentage content of C can be controlled between 0.17-0.27%, such as between 0.17-0.2% or between 0.25-0.27%.
  • Si In the 1180MPa grade steel plate with high bake hardening value described in this invention, the solubility of Si in carbides is extremely low, which can inhibit the formation of cementite. Si can also promote the enrichment of carbon into retained austenite, improve the stability of retained austenite, and increase the elongation of the steel. When the mass percentage content of Si is too high, carbides are difficult to form, which is not conducive to pinning dislocations and improving the bake hardening value; when the mass percentage content of Si is too low, more carbides precipitate, which is not conducive to the formation and stabilization of retained austenite. Therefore, in the 1180MPa grade steel plate with high bake hardening value described in this invention, the mass percentage content of Si can be controlled between 0.5-1.7%, such as between 0.5-1% or between 1.4-1.7%.
  • Mn In the 1180MPa grade steel plate with high bake hardening value described in this invention, Mn can improve the hardenability and austenite stability of the steel, reduce the critical cooling rate, and simultaneously exert a solid solution strengthening effect, thereby increasing the strength of the steel.
  • the mass percentage content of Mn When the mass percentage content of Mn is too high, it will coarsen the grains and reduce the plasticity of the steel; when the mass percentage content of Mn is too low, it is easy to cause the precipitation of banded ferrite and pearlite at low cooling rates, which is not conducive to improving the elongation of the steel. Therefore, in the 1180MPa grade steel plate with high bake hardening value described in this invention, the mass percentage content of Mn can be controlled between 2.3% and 3.0%.
  • Al In the 1180MPa grade steel plate with high bake hardening value described in this invention, when Al exists in a solid solution state, it can increase stacking faults, inhibit cementite precipitation and martensite transformation, and improve austenite stability, thereby increasing the elongation of the steel. Al can also form fine, dispersed, insoluble particles with C and N, which can refine the grains and prevent dislocation movement, thus improving the strength and bake hardening value of the steel. However, when the mass percentage content of Mn is too high, it is easy to form a large number of oxide inclusions, leading to difficulties in continuous casting. Therefore, in the 1180MPa grade steel plate with high bake hardening value described in this invention, the mass percentage content of Al can be controlled between 0.02-0.90%, such as between 0.05-0.90% or between 0.30-0.90%.
  • element B can improve the hardenability of the steel, delay the transformation of austenite to ferrite, and increase the strength of the steel.
  • the mass percentage content of element B can be controlled between 0 ⁇ B ⁇ 0.003%, such as 0.0005 ⁇ B ⁇ 0.003% or 0.0015 ⁇ B ⁇ 0.003%.
  • the mass percentage content of each element also satisfies Al+Si ⁇ 2.00%.
  • the mass percentages of Al and Si elements can also be controlled to meet the condition that Al+Si ⁇ 2.00%.
  • the mass percentages of Al and Si elements meet the condition that 1.3 ⁇ Al+Si ⁇ 1.8% or 1.4 ⁇ Al+Si ⁇ 1.75%.
  • the 1180MPa grade steel plate of the present invention also contains at least one of the following chemical elements:
  • the 1180MPa grade steel plate may also contain small amounts of Nb, V, Ti, and N, thereby improving the steel's properties.
  • Nb, V, and Ti In the 1180MPa grade steel plate with high bake hardening value described in this invention, Nb, V, and Ti elements can refine the microstructure and increase the occurrence ratio of solute C element at grain boundaries. Simultaneously, after hot rolling, the steel can precipitate (Nb, V, Ti)C type carbides. These carbides can pin dislocations during heat treatment, thereby increasing the bake hardening value.
  • the mass percentage content of Nb can be controlled between 0 ⁇ Nb ⁇ 0.1 wt%
  • the mass percentage content of V can be controlled between 0 ⁇ V ⁇ 0.1 wt%
  • the mass percentage content of Ti can be controlled between 0 ⁇ Ti ⁇ 0.1 wt%.
  • the mass percentage is 0.01 ⁇ Nb ⁇ 0.1 wt% or 0.02 ⁇ Nb ⁇ 0.1 wt%.
  • the mass percentage of V element is 0.01 ⁇ V ⁇ 0.1wt%. In some embodiments, in the 1180MPa grade steel plate with high bake hardening value described in this invention, when present, the mass percentage of Ti element is 0.01 ⁇ Ti ⁇ 0.1wt% or 0.03 ⁇ Ti ⁇ 0.1wt%.
  • N In the 1180MPa grade steel plate with high bake hardening value described in this invention, nitrogen (N) readily combines with titanium (Ti) to form TiN, which precipitates during hot rolling and provides a certain precipitation strengthening effect. However, when the mass percentage of N in the steel is too high, it affects the material's elongation and cold forming capability (r-value), and can easily cause cracks in continuously cast billets. Therefore, in the 1180MPa grade steel plate with high bake hardening value described in this invention, the mass percentage of N can be controlled between 0 ⁇ N ⁇ 0.01 wt%.
  • the mass percentage is 0.001 ⁇ N ⁇ 0.010 wt% or 0.004 ⁇ N ⁇ 0.010 wt%.
  • P In the 1180MPa grade steel plate with high bake hardening value described in this invention, although phosphorus (P) can play a solid solution strengthening role, inhibit carbide formation, and improve the stability of retained austenite, if the mass percentage content of P in the steel is too high, P will inhibit carbide precipitation, affect the bake hardening effect, and its segregation at grain boundaries will increase the brittleness of the steel. Therefore, in the 1180MPa grade steel plate with high bake hardening value described in this invention, the mass percentage content of P can be controlled to P ⁇ 0.01%, such as 0.007 ⁇ P ⁇ 0.01%.
  • S sulfur (S) will combine with manganese (Mn) to form MnS inclusions, which is detrimental to improving the cold formability of the steel. Therefore, in the 1180MPa grade steel plate with high bake hardening value described in this invention, the mass percentage content of sulfur can be controlled to S ⁇ 0.005%, such as S ⁇ 0.004%, S ⁇ 0.003%, 0.002 ⁇ S ⁇ 0.003%, or 0.002 ⁇ S ⁇ 0.005%.
  • its microstructure also contains 10-35% ferrite in area proportion, such as 10-31% or 33-35%.
  • a ferrite content of 10-35% can enhance the coordinated deformation ability of steel plates during processing and improve the formability of steel.
  • 10-17% of the area of retained austenite plays a TRIP effect during deformation, thereby strengthening and plasticizing the steel plate and further improving the elongation level.
  • its microstructure consists of 10-35% ferrite in area, 10-17% retained austenite in area, and the balance of at least one of martensite, tempered martensite, and partitioned martensite.
  • the bake hardening value within the strain range of 2-15% is not less than 120 MPa;
  • the maximum bending angle of the steel plate after baking and hardening is not less than 114°.
  • the 1180MPa grade steel plate of the present invention has a bake hardening value ⁇ 125MPa in the strain range of 2-15%, such as 120-300MPa or 125-291MPa.
  • the pre-stress variable can be 5-15%.
  • the maximum VDA bending angle of the 1180MPa grade steel plate of the present invention after baking hardening is 114°-132°.
  • the tensile strength of the 1180MPa grade steel plate of the present invention is 1180-1280MPa or 1195-1273MPa.
  • the uniform elongation of the 1180MPa grade steel plate of the present invention is 12%-20% or 12%-18%.
  • the elongation at break of the 1180MPa grade steel plate of the present invention is 18%-26% or 18%-25.3%.
  • Another objective of this invention is to provide a method for manufacturing 1180MPa grade steel plates with high bake hardening value, which can yield 1180MPa grade steel plates with excellent performance and high bake hardening value.
  • the present invention provides a method for manufacturing a 1180MPa grade steel plate with a high bake hardening value, comprising the following steps:
  • a fully austenitic or austenitic + ferrite two-phase microstructure with controllable microstructure ratio can be obtained. This is a prerequisite for obtaining carbon-supersaturated martensite and retained austenite during the rapid cooling stage. This is because the holding time is short during annealing in the austenitic single-phase region and long during annealing in the austenitic + ferrite two-phase region. Slow cooling to (Ac1 ⁇ 50)°C at a cooling rate not exceeding 10°C/s is used to further adjust the ferrite content and improve the material's ability to coordinate deformation.
  • Cooling at a rate not less than 50°C/s can obtain sufficient martensite and a high dislocation density.
  • the martensite transformation amount and retained austenite content can be controlled by adjusting the rapid cooling endpoint temperature between (Ms-10) and Mf.
  • the annealing temperature is 800–850°C or 855–890°C.
  • the annealing holding time is 30-50s or 55-185s.
  • the slow cooling rate is 3-10°C/s, such as 4-10°C/s.
  • the Ac1 temperature is 700-720°C, such as 700-716°C.
  • the slow cooling temperature is (Ac1 ⁇ 36)°C, such as 680-720°C.
  • the rapid cooling rate is 50-1000°C/s, such as 100-1000°C/s.
  • the Ms temperature is 315-348°C, such as 315-322°C or 338-348°C.
  • the Mf temperature is 197-233°C, such as 222-233°C or 197-204°C.
  • the rapid cooling temperature ((Ms-10) ⁇ Mf) is 200-310°C, such as 200-290°C.
  • the reheating temperature is 370-430°C.
  • the reheating holding time is 30-550s.
  • step (2) of the manufacturing method of the present invention the slab is heated to 1180-1280°C, held at that temperature for 60-240 minutes, and then rolled.
  • the slab is heated to 1260-1280°C.
  • the temperature is held for 120-160 minutes or 200-240 minutes.
  • controlling the slab heating temperature between 1180-1280°C can reduce dendrite coarsening and surface decarburization caused by excessively high heating temperatures, and avoid increased hot rolling deformation resistance caused by excessively low heating temperatures, thereby ensuring smooth hot rolling production.
  • Controlling the holding time between 60-240 minutes can ensure uniform internal temperature and microstructure of the slab, avoiding microstructure coarsening caused by excessively long holding times.
  • step (2) of the manufacturing method described in this invention the final rolling temperature is controlled to be 880-950°C.
  • the winding temperature is controlled at 400-650°C, and after winding, the temperature is maintained for 2-720 minutes within a range not lower than the winding temperature and not higher than 100°C above the winding temperature.
  • the winding temperature is 400-600°C or 400-580°C.
  • the temperature is maintained within a range 20-50°C higher than the winding temperature, such as 450-670°C.
  • the steel coil can be guaranteed to have suitable strength and good surface quality.
  • the hot-rolled coil strength is too high, and a low-temperature, long-duration annealing treatment can be performed to reduce the strength of the hot-rolled coil.
  • the coiling temperature is high, Si and Mn elements in the steel are prone to form an internal oxide layer that accumulates between the iron oxide scale and the steel plate substrate, making it difficult to remove completely by pickling.
  • a high-temperature, short-duration continuous annealing treatment can be performed, and shot blasting can be used to improve the removal effect of the oxide scale and internal oxide layer on the steel plate surface.
  • the coiling temperature can be controlled at 400-650°C, and the post-coiling temperature can be held for 2-720 minutes within a range not lower than the coiling temperature and not higher than 100°C above the coiling temperature.
  • step (4) of the manufacturing method described in this invention after reheating to 350-460°C and holding for 20-600 seconds, a hot-dip galvanizing process is performed to obtain the corresponding hot-dip galvanized product.
  • an electroplating zinc process can be performed after the cooling to room temperature process to obtain the corresponding electroplated zinc product.
  • the 1180MPa grade steel plate with high bake hardening value and its manufacturing method described in this invention have the following advantages and beneficial effects compared with the prior art:
  • the 1180MPa grade steel plate with high bake hardening value described in this invention has a microstructure with a high retained austenite content through composition and process design. It has a tensile strength of ⁇ 1180MPa by utilizing the TRIP effect of retained austenite, and has a uniform elongation of ⁇ 12% and a fracture elongation of ⁇ 17%.
  • the steel plate has excellent cold forming performance.
  • the 1180MPa grade steel plate with high bake hardening value described in this invention has a high carbon content and high dislocation density of martensite, tempered martensite and/or partitioned martensite, which can make full use of the steel plate in parts manufacturing, painting and baking; at the same time, the 1180MPa grade steel plate described in this invention can obtain a bake hardening value of 120-300MPa in a large strain range, further improving the strength of parts and impact energy absorption effect.
  • the 1180MPa grade steel plate with high bake hardening value described in this invention contains no less than 50% martensite of various types. After part forming, painting, and baking, it can reduce the hardness difference between phases in the microstructure, thereby improving the microstructure uniformity and obtaining excellent bending performance.
  • the maximum VDA bending angle based on a plate thickness of 1.2mm is no less than 114°. Maintaining excellent bending performance after baking can improve the part's ability to resist local deformation.
  • Figure 1 shows the SEM microstructure of the 1180MPa grade steel plate of Embodiment 2 of the present invention.
  • Figure 2 schematically shows the variation of bake hardening value in the strain range of 2-15% in Embodiment 2 of the present invention.
  • Table 1 lists the mass percentage of each chemical element in the 1180 MPa grade steel plates with high bake hardening values of Examples 1-25 and the comparative steel plates of Comparative Examples 1-2.
  • Hot rolling Heat the slab to 1180-1280°C, hold for 60-240 min, control the final rolling temperature to 880-950°C, control the coiling temperature to 400-550°C, and hold for 2-300 min at a temperature not lower than the coiling temperature and not higher than the coiling temperature +100°C.
  • a hot-dip galvanizing process can be performed to obtain a hot-dip galvanized product.
  • an electroplating zinc process may be performed after the cooling to room temperature process in step (4).
  • Tables 2-1, 2-2, and 2-3 list the specific process parameters for the 1180 MPa grade steel plates with high bake hardening values in Examples 1-25 and the comparative steel plates in Comparative Examples 1-2.
  • Table 3 lists the microstructure observation results of the 1180MPa grade steel plates with high bake hardening values in Examples 1-25 of the present invention and the comparative steel plates of Comparative Examples 1-2.
  • the area ratio of ferrite is between 10-35%
  • the area ratio of retained austenite is between 10-17%
  • the total area ratio of at least one of martensite, tempered martensite, and partitioned martensite is not less than 50%
  • the dislocation density in martensite, tempered martensite, and partitioned martensite is not less than 0.8 ⁇ 10 15 /m 2 .
  • Figure 1 shows the SEM microstructure of the 1180MPa grade steel plate of Embodiment 2 of the present invention.
  • the microstructure of Embodiment 2 of the present invention is ferrite + retained austenite + martensite + partitioned martensite, wherein the proportion of ferrite is 28%, the proportion of retained austenite is 14%, the proportion of martensite is 18%, and the proportion of partitioned martensite is 40%.
  • Baking hardening value in the strain range of 2-15% Referring to GB/T 24174-2022 standard, the specimens that have been pre-stretched with different strains of 2%-20% are baked at 170°C for 20 minutes, and then stretched until fracture. The increase in the yield strength of the specimen after baking relative to the yield strength of the specimen in its original state is the baking hardening value.
  • the maximum bending angle of the baked hardened steel plate with a thickness of 1.2 mm According to the VDA238-100 standard, a 60*60 mm sample was taken from the steel plate, and the maximum bending angle of the sample was measured using a punch with a radius of 0.4 mm.
  • Table 4 lists the test results of various properties of the 1180MPa grade steel plates with high bake hardening values in Examples 1-25 of the present invention and the comparative steels in Comparative Examples 1-2.
  • the bake hardening values of the 1180MPa grade steel plates in Examples 1-25 of the present invention within the range of 2-15% pre-deformation are all higher than 120MPa.
  • the maximum bending angle of VDA of the bake hardened steel plates with a plate thickness of 1.2mm is all higher than 114°, the tensile strength is all greater than 1180MPa, the uniform elongation is all greater than or equal to 12%, and the elongation at break is all greater than or equal to 18%.
  • Figure 2 schematically shows the variation of bake hardening value in the strain range of 2-15% in Embodiment 2 of the present invention.

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Abstract

本发明公开了一种具有高烘烤硬化值的1180MPa级钢板，其含有Fe和不可避免的杂质，其还含有质量百分比如下的下述化学元素：C：0.17～0.27％；Si：0.5～1.7％；Mn：2.3～3.0％；Al：0.02～0.90％；0<B≤0.003％；并且Al+Si≤2.00％；所述1180MPa级钢板的微观组织具有面积占比不低于50％的马氏体、回火马氏体和配分马氏体中的至少一种，所述马氏体、回火马氏体和配分马氏体中的位错密度不低于0.8×1015/m2。本发明还公开了上述钢板的制造方法，包括步骤：冶炼和连铸；热轧；酸洗和冷轧；连续退火。

Description

具有高烘烤硬化值的1180MPa级钢板及其制造方法 技术领域
本发明涉及一种钢板及其制造方法，尤其涉及一种烘烤硬化钢板及其制造方法。
背景技术
零件成形后的涂漆烘烤是汽车制造过程中的重要环节，对汽车用钢来说，涂漆烘烤后强度会增加，并使零件具有比钢板本身更高的强度，这就是所谓的烘烤硬化特性。钢板中具有一定的位错和固溶原子是获得烘烤硬化特性的必要条件，一般需要加入Nb、Ti、Mo的碳化物形成元素。汽车外板用钢的强度较低，为了获得深冲性能需要控制较低的碳含量，烘烤硬化特性的存在一定程度上提高了外板的强度，为轻量化创造了良好的基础。
目前汽车车身结构用钢以高强钢、超高强钢为主，由于其成分与组织更加复杂，对其烘烤硬化特性的研究和利用较少。如能利用高强钢的成分与相变特点，开发具有更高烘烤硬化特性的产品，同时不添加Nb、Ti、Mo贵重合金元素，有助于进一步拓展汽车车身用材的高强轻量化空间。
例如：公开号为CN107995931A，公开日为2018年5月4日，名称为“拉拔性及烘烤硬化性优异的高强度薄钢板及其制造方法”的中国专利文献公开了一种烘烤硬化性优异的高强度钢板，其成分按重量百分比计为：C：0.0005-0.003％，Si：0-0.5％(0％除外)，Mn：0-1.2％(0％除外)，P：0.005-0.12％，S<0.008％，N<0.005％，酸溶Al：0-0.1％(0％除外)，Ti：0.01-0.04％，余量为Fe及其他不可避免杂质。钢板具有4MPa以上的烘烤硬化值。制造方法为：钢坯热轧后在450-750℃卷取，以75-85％的压下率、5-15％的最终轧辊压下比进行冷轧，以0-7℃/s的速度将冷轧板加热至830-880℃保温30-80s，然后以2-10℃/s的速度冷却至650℃。该高强度钢板可以用于汽车外板件制造，其强度在200MPa左右。
发明内容
本发明的目的之一在于提供一种具有高烘烤硬化值的1180MPa级钢板，该钢板具有优异的冷成形能力、烘烤硬化特性和弯曲性能，可充分利用零件制造过程中涂漆烘烤过程，进一步提高零件的强度水平，提高碰撞吸能表现。
为了实现上述目的，本发明提供了一种具有高烘烤硬化值的1180MPa级钢板，其含有Fe和不可避免的杂质，此外其还含有质量百分比如下的下述化学元素：
C：0.17～0.27％；
Si：0.5～1.7％；
Mn：2.3～3.0％；
Al：0.02～0.90％；
0<B≤0.003％；
所述1180MPa级钢板的微观组织具有面积占比不低于50％的马氏体、回火马氏体和配分马氏体中的至少一种，所述马氏体、回火马氏体和配分马氏体中的位错密度不低于0.8×1015/m2。
在一些实施方案中，所述1180MPa级钢板的微观组织中，马氏体、回火马氏体和配分马氏体的总面积占比为50-80％，如54-74％。
在一些实施方案中，所述马氏体、回火马氏体和配分马氏体中的位错密度为0.80×1015/m2-1.00×1015/m2。
在本发明中，利用TRIP效应生成的马氏体以及组织中存在的马氏体、回火马氏体或配分马氏体可以在保证钢板具有较高强度的同时，确保经烘烤后的软硬相之间的硬度极差下降，并提高组织均匀性，进而增强钢板的弯曲性能。
在本发明中，由于淬火过程的马氏体转变使铁素体中产生大量可移动位错，而预变形阶段残余奥氏体的转变则提高了马氏体中的位错密度，并且位错密度随着预变形量的增加而增大，使得马氏体、回火马氏体、配分马氏体中的位错密度不低于0.8×1015/m2，可以提高烘烤硬化性能。这些碳过饱和的马氏体在随后的烘烤处理中发生碳的重新分配、碳原子团簇或柯氏气团形成、碳化物的析出，为密度位错的钉扎提供了充分的质点。
进一步地，在本发明所述的1180MPa级钢板中，其各化学元素质量百分比为：
C：0.17～0.27％；
Si：0.5～1.7％；
Mn：2.3～3.0％；
Al：0.02～0.90％；
0<B≤0.003％；
余量为Fe和不可避免的杂质。
在本发明所述的技术方案中，各化学元素的设计原理如下所述：
C：在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，C元素是奥氏体形成和稳定化元素，并能够延长奥氏体转变前的孕育温度。在淬火-配分工艺中，通过利用C元素从马氏体向残余奥氏体中的转移，能够提高残余奥氏体的稳定性，有助于残奥发挥TRIP效应提高材料的强度和延伸率。同时，足量的C元素在钢板变形后的涂漆烘烤过程中更容易析出并形成碳化物，能够钉扎预变形产生的可移动位错，提高烘烤硬化值。但当C元素含量过高时，钢的焊接性能会变差，并使淬火后的裂纹敏感性增加。因此，在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，可以将C元素的质量百分比含量控制在0.17-0.27％之间，如0.17-0.2％之间或0.25-0.27％之间。
Si：在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，Si元素在碳化物中的溶解度极小，能抑制渗碳体的形成。Si元素还能促进碳向残余奥氏体中富集，提高残余奥氏体的稳定性，提高钢的延伸率。当Si元素的质量百分比含量过高时，碳化物较难形成，不利于钉扎位错提高烘烤硬化值；当Si元素的质量百分比含量过低时，碳化物析出较多，不利于残余奥氏体的形成和稳定化。因此，在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，可以将Si元素的质量百分比含量控制在0.5-1.7％之间，如0.5-1％之间或1.4-1.7％之间。
Mn：在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，Mn能提高钢的淬透性和奥氏体稳定性，降低临界冷速，同时起到固溶强化的效果，提高钢的强度；当Mn元素的质量百分比含量过高时，会粗化晶粒，降低钢的塑性；当Mn元素的质量百分比含量过低时，易造成低冷速下铁素体、珠光体的带状组织析出，不利于提高钢的延伸率。因此，在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，可以将Mn元素的质量百分比含量控制在2.3-3.0％之间。
Al：在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，Al元素以固溶态存在时，能增加层错，抑制渗碳体析出和马氏体转变，提高奥氏体稳定性，从而提高钢的延伸率；Al元素还可以与C、N形成细小弥散分布的难溶质点，起到细化晶粒和阻止位错移动的作用，提高钢的强度和烘烤硬化值。但当Mn元素的质量百分比含量过高时，易形成大量氧化物夹杂，导致连铸浇注困难。因此，在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，可以将Al元素的质量百分比含量控制在0.02-0.90％之间，如0.05-0.90％之间或0.30-0.90％之间。
B：在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，B元素能够提高钢的淬透性，延缓奥氏体向铁素体转变，提高钢的强度。但当B元素的质量百分比含量过高时，会导致强度上升过快，造成延伸率下降。因此，在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，可以将B元素的质量百分比含量控制在0<B≤0.003％之间，如0.0005≤B≤0.003％或0.0015≤B≤0.003％。
进一步地，在本发明所述的1180MPa级钢板中，各元素质量百分含量还满足Al+Si≤2.00％。
在本发明的化学成分设计中，在控制单一元素含量的同时，还可以控制Al和Si元素的质量百分比满足Al+Si≤2.00％。当Al+Si含量过高时，易造成内氧化，恶化钢板表面质量。在一些实施方案中，Al和Si元素的质量百分比满足1.3≤Al+Si≤1.8％或1.4≤Al+Si≤1.75％。
进一步地，在本发明所述的1180MPa级钢板中，其还含有下述各化学元素的至少其中之一：
0<Nb≤0.1wt％；
0<V≤0.1wt％；
0<Ti≤0.1wt％；
0<N≤0.01wt％。
在本发明中，本发明所述的1180MPa级钢板中还可以含有少量的Nb、V、Ti和N，从而提高钢的性能。其中：
Nb、V、Ti：在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，Nb、V、Ti元素能够细化组织，提高溶质C元素在晶界上的赋存比例。同时，钢材经过热轧后能够析出(Nb，V，Ti)C类型的碳化物，这些碳化物在热处理过程中能够起到钉扎位错的作用，从而提高烘烤硬化值。因此，在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，可以将Nb元素的质量百分比含量控制在0<Nb≤0.1wt％之间，可以将V元素的质量百分比含量控制在0<V≤0.1wt％之间，可以将Ti元素的质量百分比含量控制在0<Ti≤0.1wt％之间。在一些实施方案中，在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，当含有时，Nb元素的质量百分比为0.01≤Nb≤0.1wt％或0.02≤Nb≤0.1wt％。在一些实施方案中，在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，当含有时，V元素的质量百分比为0.01≤V≤0.1wt％。在一些实施方案中，在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，当含有时，Ti元素的质量百分比为0.01≤Ti≤0.1wt％或0.03≤Ti≤0.1wt％。
N：在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，N元素在钢中易与Ti结合形成TiN，在热轧阶段析出可起到一定析出强化效果。但当钢中N的质量百分比含量过高时，会影响材料延伸率和r值的冷成形能力，也容易造成连铸坯裂纹。因此，在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，可以将N元素的质量百分比含量控制在0<N≤0.01wt％之间。在一些实施方案中，在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，当含有时，N元素的质量百分比为0.001≤N≤0.010wt％或0.004≤N≤0.010wt％。
进一步地，在本发明所述的1180MPa级钢板的不可避免的杂质中：P≤0.01％，S≤0.005％。
需要说明的是，在本发明所述的技术方案中，P、S和N均是钢中不可避免的杂质元素。其中：
P：在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，P元素虽然能起到固溶强化作用，抑制碳化物形成，有利于提高残余奥氏体的稳定性，但是若钢中P的质量百分比含量过高时，P元素会抑制碳化物析出，影响烘烤硬化效果，其在晶界偏聚还会增大钢的脆性。因此，在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，可以将P元素的质量百分比含量控制为P≤0.01％，如0.007≤P≤0.01％。
S：在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，S元素会与Mn元素结合形成MnS夹杂，不利于提高钢的冷成形能力。因此，在本发明所述的具有高烘烤硬化值的1180MPa级钢板中，可以将S元素的质量百分比含量控制为S≤0.005％，如S≤0.004％、S≤0.003％、0.002≤S≤0.003％或0.002≤S≤0.005％。
进一步地，在本发明所述的1180MPa级钢板中，其微观组织中还含有面积比例10-35％的铁素体，如10-31％或33-35％。
在本发明中，10-35％的铁素体含量可以增强钢板加工过程中的协调变形能力，提高钢的成形性能。
进一步地，在本发明所述的1180MPa级钢板中，其微观组织中还含有面积比例10-17％的残余奥氏体。
在本发明中，面积比例10-17％的残余奥氏体以在变形过程中发挥TRIP效应，实现钢板的增强、增塑，进一步提高延伸率水平。
进一步地，在本发明所述的1180MPa级钢板中，其微观组织为面积比例10-35％的铁素体+面积比例10-17％的残余奥氏体+余量的马氏体、回火马氏体和配分马氏体中的至少一种。
进一步地，在本发明所述的1180MPa级钢板中，其性能满足下述各项的至少其中之一：
在2-15％应变范围内的烘烤硬化值不低于120MPa；
烘烤硬化后钢板的VDA最大弯曲角度不低于114°；
抗拉强度≥1180MPa，均匀延伸率≥12％，断裂延伸率≥18％。
在一些实施方案中，本发明所述的1180MPa级钢板在2-15％应变范围内的烘烤硬化值≥125MPa，如120-300MPa或125-291MPa。
在一些实施方案中，预应变量可为5-15％。
在一些实施方案中，本发明所述的1180MPa级钢板中，烘烤硬化后钢板的VDA最大弯曲角度为114°-132°。
在一些实施方案中，本发明所述的1180MPa级钢板的抗拉强度为1180-1280MPa或1195-1273MPa。
在一些实施方案中，本发明所述的1180MPa级钢板的均匀延伸率为12％-20％或12％-18％。
在一些实施方案中，本发明所述的1180MPa级钢板的断裂延伸率18％-26％或18％-25.3％。
本发明的另一目的在于提供一种具有高烘烤硬化值的1180MPa级钢板制造方法，采用该方法可以获得性能优异高烘烤硬化值的1180MPa级钢板。
为了实现上述目的，本发明提供了一种具有高烘烤硬化值的1180MPa级钢板的制造方法，其包括步骤：
(1)冶炼和连铸；
(2)热轧；
(3)酸洗和冷轧；
(4)连续退火：控制退火温度为800-920℃，保温时间为30-200s，然后以不高于10℃/s的冷速缓冷至(Ac1±50)℃，再以不低于50℃/s的速度冷却至(Ms-10)～Mf温度区间，然后再加热至350-460℃，保温20-600s，最后冷却至室温。其中，Ac1代表钢在加热时开始转变成奥氏体的温度，Ms代表马氏体转变的起始温度，Mf代表马氏体转变的终了温度。
在本发明中，通过控制退火温度在800～930℃并保温30-200s，可以获得完全奥氏体或者组织比例可控的奥氏体+铁素体两相组织，这是快冷阶段获得碳过饱和马氏体及残余奥氏体的首要条件。这是因为：奥氏体单相区退火时保温时间短，在奥氏体+铁素体两相区退火时保温时间长。以不高于10℃/s的冷速缓冷至(Ac1±50)℃用于进一步调整铁素体含量，提高材料协调变形能力。以不低于50℃/s的速度冷却可以获得足够多的马氏体并获得高位错密度。通过在(Ms-10)～Mf之间调节快冷终点温度可以控制马氏体转变量和残余奥氏体含量。优选地，退火温度为800-850℃或855-890℃。优选地，退火保温时间为30-50s或55-185s。优选地，缓冷速度为3-10℃/s，如4-10℃/s。优选地，Ac1温度为700-720℃，如700-716℃。优选地，缓冷温度为(Ac1±36)℃，如680-720℃。优选地，快冷速度为50-1000℃/s，如100-1000℃/s。优选地，Ms温度为315-348℃，如315-322℃或338-348℃。优选地，Mf温度为197-233℃，如222-233℃或197-204℃。优选地，快冷温度((Ms-10)～Mf)为200-310℃，如200-290℃。优选地，再加热温度为370-430℃。优选地，再加热保温时间为30-550s。在本发明中，在随后的再加热过程中，发生碳从过饱和马氏体向残余奥氏体中的配分和残余奥氏体的稳定化，从而在最终冷却至室温后能够在组织中保留较高含量的残余奥氏体，保证钢板的强度和延伸率。同时，由于高碳含量残余奥氏体以及高位错密度马氏体的存在，保证了在钢板预变形、烘烤过程中位错密度的进一步提高和足够多钉扎质点的形成，提高烘烤硬化值。
进一步地，在本发明所述的制造方法的步骤(2)中，将板坯加热到1180-1280℃，保温60-240min，然后进行轧制。优选地，将板坯加热到1260-1280℃。优选地，保温120-160min或200-240min。
在本发明中，将板坯加热温度控制在1180-1280℃之间，可以减少因加热温度过高而造成的板坯枝晶粗大和表面脱碳，避免因加热温度过低而造成的热轧变形抗力升高，从而保证热轧生产的顺利。将保温时间控制在60-240min之间，可以保证板坯内部温度与组织均匀，避免时间过长造成的组织粗化。
进一步地，在本发明所述的制造方法的步骤(2)中，控制终轧温度为880-950℃。
在本发明中，通过将终轧温度控制为880-950℃，可以在奥氏体单相区轧制，从而提高可轧制性；同时避免了因温度过低而造成轧制力过大，确保生产稳定。
进一步地，在本发明所述的制造方法的步骤(2)中，控制卷取温度为400-650℃，卷取后在不低于卷取温度且不高于卷取温度以上100℃的范围内保温2-720min。优选地，卷取温度为400-600℃或400-580℃。优选地，卷取后在高于卷取温度20-50℃的范围内保温，如450-670℃。
在本发明中，通过控制卷取温度和卷取后保温温度、时间可以保证钢卷具有适宜的强度和较好的表面质量。当卷取温度过低时，热卷强度偏高，可以进行低温长时间的罩退处理以降低热轧卷强度。当卷取温度高时，钢中的Si、Mn元素容易发生内氧化层富集在氧化铁皮与钢板基体之间，造成酸洗较难去除干净，可以进行高温短时间的连退处理，利用抛丸提高钢板表面氧化皮和内氧化层的去处效果。基于此，在本发明所述的制造方法中，可以将控制卷取温度为400-650℃，卷取后在不低于卷取温度且不高于卷取温度以上100℃的范围内保温2-720min。
进一步地，在本发明所述的制造方法的步骤(4)中，在再加热至350-460℃，保温20-600s工序后还进行热镀锌工序，以获得相应的热镀锌产品。
进一步地，在本发明所述的制造方法的步骤(4)中，在冷却至室温工序后还可以进行电镀锌工序，以获得相应的电镀锌产品。
本发明所述的具有高烘烤硬化值的1180MPa级钢板及其制造方法相较于现有技术具有如下所述的优点以及有益效果：
本发明所述的具有高烘烤硬化值的1180MPa级钢板通过成分与工艺设计获得了具有较高残余奥氏体含量的微观组织，利用残余奥氏体的TRIP效应获得了≥1180MPa的抗拉强度，同时具有≥12％的均匀延伸率、≥17％的断裂延伸率，钢板的冷成形性能优异。
本发明所述的具有高烘烤硬化值的1180MPa级钢板具有较高的碳含量和高位错密度的马氏体、回火马氏体和/或配分马氏体，可充分利用钢板在零件制作、涂漆烘烤；同时，本发明所述的1180MPa级钢板可以获得在较大应变范围内获得120-300MPa的烘烤硬化值，进一步提高零件强度和碰撞吸能效果。
本发明所述的具有高烘烤硬化值的1180MPa级钢板中各类马氏体的含量占比不低于50％，在零件成形、涂漆烘烤后能减小组织中各相硬度差，从而提高组织均匀性，获得优异的弯曲性能以1.2mm板厚计的VDA最大弯角不低于114°。烘烤后保持出色的弯曲性能可提高零件抵抗局部变形的能力。
附图说明
图1显示了本发明实施例2的1180MPa级钢板的SEM微观组织图。
图2示意性地显示本发明实施例2在2-15％应变范围内的烘烤硬化值变化情况。
具体实施方式
下面将结合具体的实施例和说明书附图对本发明所述的具有高烘烤硬化值的1180MPa级钢板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1-25和对比例1-2
表1列出了实施例1-25的具有高烘烤硬化值的1180MPa级钢板和对比例1-2的对比例钢板中各化学元素质量百分比。
表1.(wt％，余量为Fe和除了P、S、N以外的其他不可避免杂质)
在本发明所述的实施例1-25的具有高烘烤硬化值的1180MPa级钢板和对比例1-2的对比例钢板均采用以下步骤制得：
(1)冶炼和连铸；
(2)热轧；将板坯加热到1180-1280℃，保温60-240min，控制终轧温度为880-950℃，控制卷取温度为400-550℃，卷取后在不低于卷取温度、不高于卷取温度+100℃的范围内保温2-300min；
(3)酸洗和冷轧；热轧卷开卷后进行酸洗及冷轧；
(4)连续退火：控制退火温度为800-920℃，保温时间为30-200s，然后以不高于10℃/s的冷速缓冷至(Ac1±50)℃，再以不低于50℃/s的速度冷却至(Ms-10)～Mf温度区间，然后再加热至350-460℃，保温20-600s，最后冷却至室温。
其中在一些实施方式中，在步骤(4)的再加热至350-460℃，保温20-600s工序后，还可以进行热镀锌工序，以获得热镀锌产品。
在另一些实施方式中，在步骤(4)的冷却至室温工序后还可以进行电镀锌工序。
需要说明的是，本发明实施例1-25的成分和工艺均符合本发明要求，而对比例1-2的成分和工艺参数均有不符合本发明之处。
表2-1、表2-2和表2-3列出了实施例1-25的具有高烘烤硬化值的1180MPa级钢板和对比例1-2的对比例钢板的具体工艺参数。
表2-1.

表2-2.

表2-3.


注：表中的“CR”表示表面无镀层；“GI”表示热镀锌镀层；“EG”表示电镀锌镀层；“GA”表
示热镀锌铁合金化镀层。
为了验证本发明的实施效果，对实施例1-25的具有高烘烤硬化值的1180MPa级钢板和对比例1-2的对比例钢板进行采样，并采用扫描电镜和X射线衍射等方法进行微观组织观察和位错密度测量，并将观察结果列于表3中。
表3列出了本发明实施例1-25的具有高烘烤硬化值的1180MPa级钢板和对比例1-2的对比例钢板的对比钢的微观组织观察结果。
表3.

从上述表3中可以看出，实施例1-25的1180MPa级钢板的微观组织中，铁素体的面积比例均在10-35％之间，残余奥氏体的面积比例均在10-17％之间，马氏体、回火马氏体、配分马氏体中的至少一种的总面积比例均不低于50％，马氏体、回火马氏体、配分马氏体中的位错密度均不低于0.8×1015/m2。
图1显示了本发明实施例2的1180MPa级钢板的SEM微观组织图。
从图1可以看出，本发明所述实施例2的微观组织为铁素体+残余奥氏体+马氏体+配分马氏体，其中，铁素体比例为28％，残余奥氏体比例为14％，马氏体比例为18％，配分马氏体比例为40％。
对实施例1-25的具有高烘烤硬化值的1180MPa级钢板和对比例1-2的对比钢进行再次取样，并对其进行各项性能测试，并将测试结果列于表4中。其中，各项性能测试包括：
在2-15％应变范围内的烘烤硬化值：参照GB/T 24174-2022标准，将经过2％-20％不同应变量的预拉伸之后的试样，在170℃烘烤20min，然后将试样拉伸直至断裂，烘烤后试样的屈服强度相对于试样原始状态屈服强度的增加值即为烘烤硬化值。
以板厚1.2mm计的烘烤硬化后钢板的VDA最大弯曲角度：参照VDA238-100标准，从钢板上取60*60mm的试样，用半径为0.4mm的冲头，测量试样的最大弯曲角度。
力学性能：参照GB/T 228-2010标准，从钢板上垂直轧制方向取拉伸试样，在室温下进行拉伸直至断裂，获得抗拉强度、均匀延伸率和断裂延伸率。
表4列出了本发明实施例1-25的具有高烘烤硬化值的1180MPa级钢板和对比例1-2的对比钢的各项性能测试结果。
表4.

从上述表4可以看出，本发明实施例1-25的1180MPa级钢板2-15％预变形量范围内的烘烤硬化值均高于120MPa，以板厚1.2mm计的烘烤硬化后钢板的VDA最大弯曲角度均高于114°，抗拉强度均大于1180MPa，均匀延伸率均大于等于12％，断裂延伸率均大于等于18％。
图2示意性地显示本发明实施例2在2-15％应变范围内的烘烤硬化值变化情况。
如图2所示的，本发明实施例2在2％、5％、8％、10％、15％预变形条件下的烘烤硬化值分别为122MPa、170MPa、212MPa、245MPa、287MPa，随着预变形量的增大烘烤硬化值也逐渐提高，但均在120-300MPa范围内。
需要说明的是，本发明的保护范围中现有技术部分并不局限于本申请文件所给出的实施例，所有不与本发明的方案相矛盾的现有技术，包括但不局限于在先专利文献、在先公开出版物，在先公开使用等等，都可纳入本发明的保护范围。此外，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例所记载的组合方式，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，以上所列举的实施例仅为本发明的具体实施例。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 (15)

  1. 一种具有高烘烤硬化值的1180MPa级钢板，其含有Fe和不可避免的杂质，其特征在于，其还含有质量百分比如下的下述化学元素：
    C：0.17～0.27％；
    Si：0.5～1.7％；
    Mn：2.3～3.0％；
    Al：0.02～0.90％；
    0＜B≤0.003％；
    所述1180MPa级钢板的微观组织具有面积占比不低于50％的马氏体、回火马氏体和配分马氏体中的至少一种，所述马氏体、回火马氏体和配分马氏体中的位错密度不低于0.8×1015/m2；
    优选地，马氏体、回火马氏体和配分马氏体的总面积占比为50-80％；
    优选地，所述马氏体、回火马氏体和配分马氏体中的位错密度为0.80×1015/m2-1.00×1015/m2。
  2. 如权利要求1所述的1180MPa级钢板，其特征在于，其各化学元素质量百分比为：
    C：0.17～0.27％；
    Si：0.5～1.7％；
    Mn：2.3～3.0％；
    Al：0.02～0.90％；
    0＜B≤0.003％；
    余量为Fe和不可避免的杂质。
  3. 如权利要求1或2所述的1180MPa级钢板，其特征在于，各元素质量百分含量还满足Al+Si≤2.00％，优选为1.3≤Al+Si≤1.8％或1.4≤Al+Si≤1.75％。
  4. 如权利要求1或2所述的1180MPa级钢板，其特征在于，其还含有下述各化学元素的至少其中之一：
    0＜Nb≤0.1wt％；
    0＜V≤0.1wt％；
    0＜Ti≤0.1wt％；
    0＜N≤0.01wt％。
  5. 如权利要求1或2所述的1180MPa级钢板，其特征在于，在不可避免的杂质中：P≤0.01％，S≤0.005％。
  6. 如权利要求1或2所述的1180MPa级钢板，其特征在于，其微观组织中还含有面积比例10-35％的铁素体，优选为10-31％或33-35％。
  7. 如权利要求1或2所述的1180MPa级钢板，其特征在于，其微观组织中还含有面积比例10-17％的残余奥氏体。
  8. 如权利要求1或2所述的1180MPa级钢板，其特征在于，其微观组织为面积比例10-35％的铁素体+面积比例10-17％的残余奥氏体+余量的马氏体、回火马氏体、配分马氏体中的至少一种。
  9. 如权利要求1或2所述的1180MPa级钢板，其特征在于，其性能满足下述各项的至少其中之一：
    在2-15％应变范围内的烘烤硬化值不低于120MPa，优选为120-300MPa；
    烘烤硬化后钢板的VDA最大弯曲角度不低于114°，优选为114°-132°；
    抗拉强度≥1180MPa，优选为1180-1280MPa；
    均匀延伸率≥12％，优选为12％-20％；
    断裂延伸率≥18％，优选为18％-26％。
  10. 如权利要求1-9中任意一项所述的1180MPa级钢板的制造方法，其特征在于，包括步骤：
    (1)冶炼和连铸；
    (2)热轧；
    (3)酸洗和冷轧；
    (4)连续退火：控制退火温度为800-920℃，保温时间为30-200s，然后以不高于10℃/s的冷速缓冷至(Ac1±50)℃，再以不低于50℃/s的速度冷却至(Ms-10)～Mf温度区间，然后再加热至350-460℃，保温20-600s，最后冷却至室温。
  11. 如权利要求10所述的制造方法，其特征在于，在步骤(2)中，将板坯加热到1180-1280℃，保温60-240min，然后进行轧制。
  12. 如权利要求10所述的制造方法，其特征在于，在步骤(2)中，控制终轧温度为880-950℃。
  13. 如权利要求10所述的制造方法，其特征在于，在步骤(2)中，控制卷取温度为400-650℃，卷取后在不低于卷取温度且不高于卷取温度以上100℃的范围内保温2-720min。
  14. 如权利要求10所述的制造方法，其特征在于，在步骤(4)中，在再加热至350-460℃，保温20-600s工序后还进行热镀锌工序；和/或，在步骤(4)中，在冷却至室温工序后还进行电镀锌工序。
  15. 权利要求10所述的制造方法，其特征在于，步骤(4)具有以下一项或多项特征：
    缓冷速度为3-10℃/s；
    Ac1温度为700-720℃；
    缓冷温度为680-720℃；
    快冷速度为50-1000℃/s；
    Ms温度为315-348℃；
    Mf温度为197-233℃；
    快冷温度((Ms-10)～Mf)为200-310℃。
PCT/CN2025/103369 2024-06-26 2025-06-25 具有高烘烤硬化值的1180MPa级钢板及其制造方法 Pending WO2026002017A1 (zh)

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