WO2021078111A1 - High-strength steel having good ductility and manufacturing method therefor - Google Patents

High-strength steel having good ductility and manufacturing method therefor Download PDF

Info

Publication number
WO2021078111A1
WO2021078111A1 PCT/CN2020/122085 CN2020122085W WO2021078111A1 WO 2021078111 A1 WO2021078111 A1 WO 2021078111A1 CN 2020122085 W CN2020122085 W CN 2020122085W WO 2021078111 A1 WO2021078111 A1 WO 2021078111A1
Authority
WO
WIPO (PCT)
Prior art keywords
strength steel
steel
excellent ductility
manufacturing
strength
Prior art date
Application number
PCT/CN2020/122085
Other languages
French (fr)
Chinese (zh)
Inventor
陈孟
钟勇
汪水泽
李旭飞
王利
毛新平
Original Assignee
宝山钢铁股份有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 宝山钢铁股份有限公司 filed Critical 宝山钢铁股份有限公司
Publication of WO2021078111A1 publication Critical patent/WO2021078111A1/en

Links

Images

Classifications

    • 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
    • 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 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
    • 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
    • C21D8/0226—Hot rolling
    • 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
    • C21D8/0236—Cold rolling
    • 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
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • 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
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • 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
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • 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
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • 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
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
    • C22C38/18—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
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

Definitions

  • the invention relates to a kind of steel and a manufacturing method thereof, in particular to a high-strength steel and a manufacturing method thereof.
  • Advanced high-strength steel is the most comprehensively competitive body lightweight material at present by increasing the strength of the steel plate to reduce the thickness of the steel plate while maintaining excellent formability. It is also the focus of steel mills and OEMs.
  • TRIP steel is composed of ferrite, bainite and retained austenite. This phase structure limits the further improvement of its strength. Using martensite instead of bainite as the main strengthening phase can continue to increase Strength of TRIP steel.
  • the main factors that determine its ductility are the shape, volume fraction and stability of retained austenite in the steel. The stability of retained austenite is closely related to its size and carbon content.
  • the existing advanced high-strength steels are mostly based on the composition of carbon-manganese steel, adding more alloy elements such as Cr, Mo, Nb, Ti, B, etc., which not only increases the material cost, but also improves the steelmaking
  • the manufacturability of hot rolling and cold rolling brings difficulties.
  • the publication number is CN106574342A
  • the publication date is April 19, 2017,
  • the Chinese patent document entitled "High-strength steel sheet and its manufacturing method, and high-strength galvanized steel sheet manufacturing method" discloses a high-strength steel sheet.
  • the manufacturing method is as follows: heating a slab satisfying the composition conditions to 1100-1300°C, finishing rolling outlet temperature 800-1000°C, average coiling temperature 450-700°C, after pickling
  • the steel plate is kept at 450°C ⁇ Ac1 temperature for 900 ⁇ 36000s, cold rolling is performed at a reduction rate of 30% or more, the steel plate is heated to 820 ⁇ 950°C for the first annealing, and then the average cooling rate up to 500°C is 15°C/
  • cool to below Ms temperature and then heat to 740 ⁇ 840°C for the second annealing, cool to 150 ⁇ 350°C at a cooling rate of 1 ⁇ 15°C/s, and then heat to 350 ⁇ 550°C for more than 10s .
  • heating and rolling are required, and two annealing treatments are adopted, the production process is cumbersome, and the manufacturing cost increases. Therefore, its application in the automotive field is greatly restricted.
  • the publication number is CN104245971A
  • the publication date is December 24, 2014
  • the Chinese patent document titled "High-strength cold-rolled steel sheet and method for producing the same” discloses a high-strength cold-rolled steel sheet.
  • its composition is: C: 0.1% to 0.3%, Si: 0.4% to 1.0%, Mn: 2.0% to 3.0%, Cr ⁇ 0.6%, Si+0.8Al+Cr :1.0% ⁇ 1.8%, Al:0.2% ⁇ 0.8%, Nb ⁇ 0.1%, Mo ⁇ 0.3%, Ti ⁇ 0.2%, V ⁇ 0.1%, Cu ⁇ 0.5%, Ni ⁇ 0.5%, S ⁇ 0.01%, P ⁇ 0.02%, N ⁇ 0.02%, B ⁇ 0.005%, Ca ⁇ 0.005%, Mg ⁇ 0.005%, REM ⁇ 0.005%, and the balance is Fe and unavoidable impurities.
  • the microstructure (vol%) is: retained austenite 5%-20%, bainite + bainite ferrite + tempered martensite ⁇ 80%, polygonal ferrite ⁇ 10%, martensite -Austenite composition ⁇ 20%. It should be pointed out that because the steel components involved in the technical solution need to add a certain amount of Cr and Mo, although its tensile strength is ⁇ 980MPa, the elongation is only about 14%, which is very important for the cost and forming of steel for automotive parts. The sexual advantage is not obvious.
  • One of the objectives of the present invention is to provide a high-strength steel with excellent ductility.
  • the high-strength steel adopts a simple composition design and makes full use of the influence law of C, Si and Mn on the phase transformation of the material to ensure the Strength and ductility.
  • the present invention proposes a high-strength steel with excellent ductility, the mass percentage of chemical elements is:
  • the balance is Fe and other unavoidable impurities.
  • C In the high-strength steel with excellent ductility of the present invention, the solubility of C in austenite is much higher than its solubility in ferrite, which can prolong the incubation period before austenite transformation and reduce Ms temperature.
  • C is also the most basic solid solution strengthening element in steel. However, an excessively high mass percentage of C will reduce the weldability of the steel.
  • the mass percentage of C in the steel exceeds 0.25%, more twins are prone to appear after quenching, which increases crack sensitivity. Based on this, in the high-strength steel with excellent ductility according to the present invention, the mass percentage of C is controlled at 0.15-0.25 wt%.
  • Si In the high-strength steel with excellent ductility described in the present invention, the solubility of Si in carbides is extremely small, and the formation of cementite is strongly inhibited during the partitioning process, and carbon is concentrated in retained austenite. Improve the stability of retained austenite. However, if the mass percentage of Si is too high, it will reduce the high-temperature plasticity of the steel and increase the incidence of hot rolling defects. At the same time, when the mass percentage of Si is high, stable oxides will be formed on the surface of the steel sheet, reducing the wettability of the steel sheet. Based on this, the mass percentage of Si in the high-strength steel with excellent ductility according to the present invention is controlled at 1.00 to 2.00 wt%.
  • Mn In the high-strength steel with excellent ductility described in the present invention, Mn can expand the austenite phase region, reduce Ac3, Ms and Mf points, improve the stability of austenite and the hardenability of steel, and reduce critical transformation The speed is beneficial to the preservation of retained austenite to room temperature. At the same time, Mn can also play a solid solution strengthening effect in steel. However, if the mass percentage of Mn is too high, it will aggravate the tendency of grain coarsening, reduce the plasticity and toughness of steel, and deteriorate corrosion resistance and welding performance. However, if the mass percentage of Mn is too low, the segregation will cause ferrite and pearlite banded structures to be produced at low cooling rates. Based on this, the mass percentage of Mn in the high-strength steel with excellent ductility according to the present invention is controlled to be 1.50 to 3.00 wt%.
  • Al In the high-strength steel with excellent ductility of the present invention, when Al exists in a solid solution state, it can increase the stacking fault energy, inhibit the precipitation of cementite and the transformation of ⁇ to martensite, and improve the stability of austenite .
  • Al, C and N form fine and dispersed insoluble points, which can refine grains, but the strengthening effect of Al is weaker than that of Si, and the ability to stabilize austenite is also weaker than that of Si.
  • the mass percentage of Al is too high to easily form a large number of oxide inclusions, which is not conducive to steelmaking and continuous casting. Therefore, the mass percentage of Al in the high-strength steel with excellent ductility according to the present invention is controlled to be 0.03 to 0.06 wt%.
  • the mass percentage of each chemical element satisfies at least one of the following items:
  • the high-strength steel with excellent ductility according to the present invention also contains at least one of the following elements:
  • the aforementioned Cr, Mo, Nb, Ti, V, and B can further improve the performance of the high-strength steel according to the present invention.
  • Cr and Mo can improve the hardenability of steel and adjust the strength of steel, but Cr will be enriched on the surface of the steel plate, which affects the welding performance, and the higher mass percentage of Mo leads to the increase of the cold-rolled deformation resistance of the steel.
  • Nb, Ti, V elements can form fine carbides with C to promote structure refinement, but the formation of such fine carbides is not conducive to the enrichment of C into retained austenite and the stabilization of retained austenite .
  • the main function of B is to improve the hardenability of steel.
  • B is easy to segregate at the austenite grain boundary and delay the transformation of austenite to ferrite. Adding a small amount to the steel can play a significant role. The quality of B Too high a percentage will increase the strength of the steel, which is not conducive to good shaping. Therefore, the mass percentage of B can be controlled at B ⁇ 0.001%.
  • the addition of the above-mentioned elements will increase the cost of the material. Considering the performance and cost control comprehensively, in the technical solution of the present invention, at least one of the above-mentioned elements can be preferably added.
  • each chemical element satisfies at least one of the following items:
  • Mo ⁇ 0.25wt% preferably, Mo ⁇ 0.20wt%
  • V ⁇ 0.02wt% preferably, V ⁇ 0.01wt%.
  • P, S, and N are impurities.
  • P can play a solid solution strengthening effect and inhibit the formation of carbides, it is beneficial to improve the stability of retained austenite.
  • the mass percentage of P is too high, it will weaken The grain boundary increases the brittleness of the material and deteriorates the welding performance, that is, the positive effect of P is weaker than its negative effect. Therefore, it is preferable to control the mass percentage of P to P ⁇ 0.015wt%.
  • N too high mass percentage of N will bring difficulties to steelmaking and continuous casting, and is not conducive to the control of inclusions. Therefore, it is preferable to control the mass percentage of N to N ⁇ 0.008wt%.
  • the microstructure is 30% to 50% ferrite + 40% to 60% martensite + retained austenite.
  • grains of 10 ⁇ m or less account for 80% or more, and grains of 5 ⁇ m or less account for 50% or more of ferrite.
  • the average grain size of the retained austenite is less than or equal to 2 ⁇ m; and/or the average C content in the retained austenite is more than or equal to 1.1 wt%. In some embodiments, the average grain size of retained austenite is in the range of 0.3-2 ⁇ m. In some embodiments, the average C content in the retained austenite is 1.1 wt% to 1.5 wt%, such as 1.1 wt% to 1.3 wt%.
  • the yield strength is 550-850MPa
  • the tensile strength is 900-1100MPa
  • the uniform elongation (UEL) is ⁇ 13%
  • the elongation at break (TEL) It is 18%-28%.
  • the uniform elongation is 13-19%.
  • another object of the present invention is to provide the above-mentioned manufacturing method of high-strength steel with excellent ductility.
  • the manufacturing method adopts a thin slab continuous casting process combined with a pickling or pickling process to obtain excellent ductility after continuous annealing.
  • the manufacturing method is simple to produce, and the obtained high-strength steel has a significantly improved elongation under the same strength condition.
  • the present invention proposes the above-mentioned manufacturing method of high-strength steel with excellent ductility, which includes the following steps:
  • the thickness of the slab at the exit end of the continuous casting is controlled to be 52-60mm, preferably 55-60mm;
  • Continuous annealing annealing at 800 ⁇ 920°C, slowly cooling to 680 ⁇ 750°C at a cooling rate of 3 ⁇ 10°C/s to obtain a certain proportion of ferrite; then quickly cooling to 220 ⁇ 320°C, cooling The speed is 50-1000°C/s to partially transform austenite into martensite; then it is heated to 360-460°C for 100-500s, and finally cooled to room temperature.
  • step (1) adopts thin slab continuous casting, the rough rolling process can be omitted, and the deformation of hot rolling can be reduced, thereby ensuring that the subsequent steps (4) and step ( 5) The performance of the steel plate.
  • step (1) adopts thin slab continuous casting, it can make full use of the heat of the slab and reduce the energy consumption required for heating, thereby obtaining a more uniform ferrite or ferrite + pearlite structure, which is beneficial to the step 5) Maintain a certain amount of fine-grained ferrite in the microstructure of the finished product to improve the uniformity of the structure.
  • step (3) controlling the thickness of the scale on the surface of the steel strip after hot rolling to be ⁇ 5 ⁇ m, and the (FeO+Fe 3 O 4 ) in the scale on the surface of the steel strip after the hot rolling is ⁇ 40wt%, which can be beneficial to the subsequent steps
  • the progress of (4) has an important influence on the performance of the steel sheet obtained after continuous annealing.
  • a uniform austenite structure or austenite + ferrite structure can be formed by controlling the annealing temperature; then slowly cool to 660-750°C at a cooling rate of 3-10°C/s, Preferably 680-750°C to further adjust the content of ferrite in the structure and improve the shaping of the material; then cool to 220-320 at a rate of 50-1000°C/s, preferably 50-600°C, more preferably 50-100°C °C (that is, between Ms and Mf temperature), at this time, austenite is partially transformed into martensite to ensure that the steel has higher strength; then heat to 360 ⁇ 460°C and keep for 100 ⁇ 500s, such as 100- 300s, the carbon is partitioned between martensite and austenite to form a certain amount of carbon-rich retained austenite, which is kept stable to room temperature. Due to the TRIP effect, the work hardening ability and formability of the steel can be significantly improved, and the ductility can be obtained. High-stre
  • the high-strength steel in this case adopts high-carbon, high-manganese design and ferrite grain refinement
  • the nucleation point of the reverse phase transformation of austenite increases while the size is further refined.
  • the average grain size of the retained austenite that is stably maintained to room temperature can be ⁇ 2 ⁇ m; the average C content in the retained austenite is ⁇ 1.1wt%.
  • the martensite formed by rapid cooling basically does not decompose during the partitioning process to ensure the content of martensite in the structure, thereby ensuring the strength of the steel.
  • step (1) the continuous casting drawing speed is controlled to be 2-5 m/min.
  • step (2) the slab is heated to 1200-1250°C.
  • step (3) the finishing rolling temperature is controlled to be 860 to 930°C, and the coiling temperature is to be 450 to 600°C.
  • step (4) when the pickling + cold rolling step is adopted, the deformation is controlled to be 30% to 70%.
  • step (5) the volume content of hydrogen in the reducing atmosphere in the continuous annealing furnace is controlled to 10-15%.
  • step (5) the continuous annealing process is controlled to satisfy at least one of the following items:
  • Annealing temperature is 820 ⁇ 870°C
  • the volume content of hydrogen in the reducing atmosphere in the continuous annealing furnace is controlled to 10-15%.
  • the high-strength steel with excellent ductility and its manufacturing method according to the present invention have the following advantages and beneficial effects:
  • the high-strength steel of the present invention is based on carbon-silicon-manganese steel without adding any expensive alloy elements, and by optimizing the ratio of carbon-silicon-manganese, a high-strength cold-rolled steel sheet with excellent ductility is obtained.
  • the manufacturing method of the present invention has a simple production process, and the obtained high-strength steel can significantly increase its elongation under the same strength conditions. It will have a good application prospect in automobile safety structural parts, and is particularly suitable for manufacturing complex shapes, Vehicle structural parts and safety parts that require high formability, such as A/B pillars, longitudinal beams, door anti-collision bars, bumpers, etc.
  • Fig. 1 is a microstructure photograph of the high-strength steel of Example 12.
  • Fig. 2 is an EBSD photograph of the phase composition of the high-strength steel of Example 12.
  • the high-strength steel with excellent ductility of Examples 1-36 was prepared by the following steps:
  • Hot rolling The thickness of the oxide scale on the surface of the steel strip after hot rolling is ⁇ 5 ⁇ m, and the (FeO+Fe 3 O 4 ) in the oxide scale on the surface of the strip after hot rolling is ⁇ 40wt%, and the final rolling temperature is controlled at 860 ⁇ 930°C , The coiling temperature is 450 ⁇ 600°C.
  • Continuous annealing annealing at 800 ⁇ 920°C, slowly cooling to 660 ⁇ 750°C at a cooling rate of 3 ⁇ 10°C/s to obtain a certain proportion of ferrite; then quickly cooling to 220 ⁇ 320°C, cooling The speed is 50-1000°C/s to partially transform austenite into martensite; then it is heated to 360-460°C for 100-500s, and finally cooled to room temperature.
  • the volume content of hydrogen in the reducing atmosphere in the continuous annealing furnace is controlled to 10-15%.
  • control parameters can be further controlled to satisfy at least one of the following items:
  • Annealing temperature is 820 ⁇ 870°C
  • the volume content of hydrogen in the reducing atmosphere in the continuous annealing furnace is controlled to 10-15%.
  • the comparative examples 1-3 were manufactured using conventional processes.
  • Table 1 lists the mass percentage ratios of the chemical elements of the high-strength steel with excellent ductility of Examples 1-36 and the comparative steel of Comparative Examples 1-3.
  • Table 2-1 and Table 2-2 list the specific process parameters of the high-strength steel with excellent ductility in Examples 1-36 and the comparative steel in Comparative Examples 1-3.
  • Table 3 lists the mechanical performance test results of the high-strength steel with excellent ductility in Examples 1-36 and the comparative steel in Comparative Examples 1-3.
  • the high-strength steel with excellent ductility in Examples 1-36 of this case guarantees its strength and has excellent ductility surface. Its yield strength is 550-850 MPa, and its tensile strength is 900-1100 MPa. The rate is ⁇ 13%, and the elongation at break is 18%-28%.
  • the microstructure of the high-strength steel with excellent ductility in Examples 1-36 of this case is 30% to 50% ferrite + 40% to 60% martensite + retained austenite
  • the grains below 10 ⁇ m account for more than 80%
  • the grains below 5 ⁇ m account for more than 50%
  • the average grain size of retained austenite is ⁇ 2 ⁇ m
  • retained austenite The average C content in the body is ⁇ 1.1wt%.
  • the high-strength steel with excellent ductility in each embodiment of this case has a certain amount of fine-grained ferrite and good microstructure uniformity, so that the high-strength steel of each embodiment can be used in high-strength steels. At the same time, it has excellent ductility.
  • Fig. 1 is a photo of the microstructure of the high-strength steel of Example 12.
  • Fig. 2 is an EBSD photograph of the phase composition of the high-strength steel of Example 12.
  • the microstructure of the high-strength steel of Example 12 is 30% to 50% ferrite + 40% to 60% martensite + retained austenite.
  • the grains below 10 ⁇ m account for more than 80%
  • the grains below 5 ⁇ m account for more than 50%
  • the average grain size of retained austenite is ⁇ 2 ⁇ m
  • the average C content in retained austenite is ⁇ 1.1 wt%.
  • the high-strength steel of the present invention is based on carbon-silicon-manganese steel without adding any expensive alloying elements. By optimizing the ratio of carbon-silicon-manganese, high-strength cold-rolled steel with excellent ductility is obtained. Steel plate.
  • the manufacturing method of the present invention has a simple production process, and the obtained high-strength steel can significantly increase its elongation under the same strength conditions. It will have a good application prospect in automobile safety structural parts, and is particularly suitable for manufacturing complex shapes, Vehicle structural parts and safety parts that require high formability, such as A/B pillars, longitudinal beams, door anti-collision bars, bumpers, etc.

Abstract

Disclosed is a high-strength steel having a good ductility, with the chemical elements thereof, in mass percentages, being: 0.15-0.25 wt% of C, 1.00-2.00 wt% of Si, 1.50-3.00 wt% of Mn, and 0.03-0.06 wt% of Al, with the balance being Fe and other unavoidable impurities. In addition, disclosed is a method for manufacturing the steel, the method comprising the following steps: (1) smelting and thin plate blank continuous casting, wherein the thickness of a plate blank at a continuous casting exit end is controlled to be 55-60 mm; (2) heating; (3) hot rolling, wherein an oxidized scale on the surface of a hot-rolled steel band has a thickness of ≤5 μm, and (FeO+Fe3O4) in the oxidized scale on the surface of the hot-rolled band steel is ≤40 wt%; (4) acid pickling or acid pickling and cold rolling; and (5) continuous annealing.

Description

一种延展性优异的高强度钢及其制造方法High-strength steel with excellent ductility and manufacturing method thereof 技术领域Technical field
本发明涉及一种钢种及其制造方法，尤其涉及一种高强度钢及其制造方法。The invention relates to a kind of steel and a manufacturing method thereof, in particular to a high-strength steel and a manufacturing method thereof.
背景技术Background technique
近年来，以车身轻量化为代表的汽车轻量化技术为汽车实现“节能、减排、安全、经济”的发展提供了有力的支撑。而先进高强钢通过提高钢板强度以减薄钢板厚度，同时保持优秀的成形性能，是目前最具综合竞争力的车身轻量化用材，也是钢厂与主机厂重点关注的方向。In recent years, automobile lightweight technology represented by body lightweight has provided strong support for the development of "energy saving, emission reduction, safety, and economy" for automobiles. Advanced high-strength steel is the most comprehensively competitive body lightweight material at present by increasing the strength of the steel plate to reduce the thickness of the steel plate while maintaining excellent formability. It is also the focus of steel mills and OEMs.
基于相变诱导塑性(TRIP)效应的先进高强钢在保持高强度的同时，还具有较好的延展性。从微观组织看，TRIP钢由铁素体，贝氏体和残余奥氏体组成，这种相结构限制了其强度的进一步提高，以马氏体代替贝氏体作为主要的强化相可以继续提高TRIP钢的强度。对基于TRIP效应的先进高强钢而言，决定其延展性的主要因素是钢中残余奥氏体的形态、体积分数及稳定性，残余奥氏体的稳定性又与其尺寸、碳含量密切相关。Advanced high-strength steel based on TRIP effect maintains high strength while also having good ductility. From the microstructure point of view, TRIP steel is composed of ferrite, bainite and retained austenite. This phase structure limits the further improvement of its strength. Using martensite instead of bainite as the main strengthening phase can continue to increase Strength of TRIP steel. For advanced high-strength steel based on the TRIP effect, the main factors that determine its ductility are the shape, volume fraction and stability of retained austenite in the steel. The stability of retained austenite is closely related to its size and carbon content.
为保证钢板的强度和延展性能，现有先进高强钢多以碳锰钢成分为基础，添加较多的Cr、Mo、Nb、Ti、B等合金元素，不仅提高了材料成本，而且对炼钢、热轧、冷轧的可制造性带来难度。In order to ensure the strength and ductility of the steel plate, the existing advanced high-strength steels are mostly based on the composition of carbon-manganese steel, adding more alloy elements such as Cr, Mo, Nb, Ti, B, etc., which not only increases the material cost, but also improves the steelmaking The manufacturability of hot rolling and cold rolling brings difficulties.
例如：公开号为CN106574342A，公开日为2017年4月19日，名称为“高强度钢板及其制造方法、以及高强度镀锌钢板的制造方法”的中国专利文献公开了一种高强度钢板。在该专利文献所公开的技术方案中，其制造方法为：满足成分条件的钢坯加热至1100～1300℃，精轧出口侧温度800～1000℃，平均卷取温度450～700℃，酸洗后将钢板在450℃～Ac1温度保持900～36000s，以30％以上压下率进行冷轧，钢板加热至820～950℃进行第一次退火，然后在至500℃为止的平均冷却速度15℃/s以上条件下冷却至Ms温度以下，再加热至740～840℃进行第二次退火，以1～15℃/s的冷却速度冷至150～350℃，再加热至350～550℃保温10s以上。需要指出的是，在该专利文献所公开的技术方案中需要加热轧制，而且采用了两次退火处理，生产工 序繁琐，制造成本增加，因此，使得其在汽车领域的应用受到较大限制。For example, the publication number is CN106574342A, the publication date is April 19, 2017, and the Chinese patent document entitled "High-strength steel sheet and its manufacturing method, and high-strength galvanized steel sheet manufacturing method" discloses a high-strength steel sheet. In the technical solution disclosed in this patent document, the manufacturing method is as follows: heating a slab satisfying the composition conditions to 1100-1300°C, finishing rolling outlet temperature 800-1000°C, average coiling temperature 450-700°C, after pickling The steel plate is kept at 450℃～Ac1 temperature for 900～36000s, cold rolling is performed at a reduction rate of 30% or more, the steel plate is heated to 820～950℃ for the first annealing, and then the average cooling rate up to 500℃ is 15℃/ Under the above conditions, cool to below Ms temperature, and then heat to 740～840℃ for the second annealing, cool to 150～350℃ at a cooling rate of 1～15℃/s, and then heat to 350～550℃ for more than 10s . It should be pointed out that in the technical solution disclosed in the patent document, heating and rolling are required, and two annealing treatments are adopted, the production process is cumbersome, and the manufacturing cost increases. Therefore, its application in the automotive field is greatly restricted.
又例如：公开号为CN104245971A，公开日为2014年12月24日，名称为“高强度冷轧钢板和生产该钢板的方法”的中国专利文献公开了一种高强度冷轧钢板。在该专利文献所公开的技术方案中，其成分为：C:0.1％～0.3％、Si:0.4％～1.0％、Mn:2.0％～3.0％、Cr≤0.6％、Si+0.8Al+Cr:1.0％～1.8％、Al:0.2％～0.8％、Nb＜0.1％、Mo＜0.3％、Ti＜0.2％、V＜0.1％、Cu＜0.5％、Ni＜0.5％、S≤0.01％、P≤0.02％、N≤0.02％、B＜0.005％、Ca＜0.005％、Mg＜0.005％、REM＜0.005％，余量为Fe和不可避免的杂质。显微组织(体积％)为：残余奥氏体5％～20％、贝氏体+贝氏体铁素体+回火马氏体≥80％、多边形铁素体≤10％、马氏体-奥氏体组分≤20％。需要指出的是，由于该技术方案所涉及的钢种成分需要加入一定量的Cr、Mo，虽然其抗拉强度≥980MPa但是时延伸率仅14％左右，对汽车零部件用钢的成本和成形性优势不明显。For another example, the publication number is CN104245971A, the publication date is December 24, 2014, and the Chinese patent document titled "High-strength cold-rolled steel sheet and method for producing the same" discloses a high-strength cold-rolled steel sheet. In the technical solution disclosed in this patent document, its composition is: C: 0.1% to 0.3%, Si: 0.4% to 1.0%, Mn: 2.0% to 3.0%, Cr≤0.6%, Si+0.8Al+Cr :1.0%～1.8%, Al:0.2%～0.8%, Nb＜0.1%, Mo＜0.3%, Ti＜0.2%, V＜0.1%, Cu＜0.5%, Ni＜0.5%, S≤0.01%, P≤0.02%, N≤0.02%, B<0.005%, Ca<0.005%, Mg<0.005%, REM<0.005%, and the balance is Fe and unavoidable impurities. The microstructure (vol%) is: retained austenite 5%-20%, bainite + bainite ferrite + tempered martensite ≥ 80%, polygonal ferrite ≤ 10%, martensite -Austenite composition ≤ 20%. It should be pointed out that because the steel components involved in the technical solution need to add a certain amount of Cr and Mo, although its tensile strength is ≥980MPa, the elongation is only about 14%, which is very important for the cost and forming of steel for automotive parts. The sexual advantage is not obvious.
再例如：公开号为WO2018/116155，公开日为2018年6月28日，名称为“HIGH-STRENGTH COLD ROLLED STEEL SHEET HAVING HIGH FORMABILITY AND A METHOD OF MANUFACTURING THEREOF”的国际专利文献公开了一种具有高成形性的高强度冷轧钢板。在该专利文献所公开的技术方案中，其成分为：C:0.19％～0.24％、Mn:1.9％～2.2％、Si:1.4％～1.6％、Al:0.01％～0.06％、Cr:0.2％～0.5％、P≤0.02％、S≤0.003％，任选的一种或几种：Nb:0.0010％～0.06％、Ti:0.001％～0.08％、V:0.001％～0.1％、Ca:0.001％～0.005％，余量为Fe和不可避免杂质。需要指出的是，该技术方案所涉及的钢种的抗拉强度≥1150MPa，延伸率≥13％、扩孔率≥30％，虽然其抗拉强度较高，但是加入了较多的Cr及Nb、Ti元素，因而，不适合作为成本控制要求非常严格的汽车用钢。Another example: the publication number is WO2018/116155, the publication date is June 28, 2018, and the international patent document titled "HIGH-STRENGTH COLD ROLLED STEEL SHEET HAVING HIGH FORMABILITY AND A METHOD OF MANUFACTURING THEREOF" Formable high-strength cold-rolled steel sheet. In the technical solution disclosed in the patent document, its composition is: C: 0.19% to 0.24%, Mn: 1.9% to 2.2%, Si: 1.4% to 1.6%, Al: 0.01% to 0.06%, Cr: 0.2 %～0.5%, P≤0.02%, S≤0.003%, optional one or more: Nb: 0.0010%～0.06%, Ti: 0.001%～0.08%, V: 0.001%～0.1%, Ca: 0.001%～0.005%, the balance is Fe and unavoidable impurities. It should be pointed out that the tensile strength of the steel involved in this technical solution is ≥1150MPa, the elongation is ≥13%, and the hole expansion rate is ≥30%. Although its tensile strength is relatively high, more Cr and Nb are added. , Ti element, therefore, is not suitable as steel for automobiles with very strict cost control requirements.
发明内容Summary of the invention
本发明的目的之一在于提供一种延展性优异的高强度钢，该高强度钢采用了简单的成分设计，其充分利用C、Si以及Mn元素对材料相变的影响规律，以保证钢板的强度以及延展性能。One of the objectives of the present invention is to provide a high-strength steel with excellent ductility. The high-strength steel adopts a simple composition design and makes full use of the influence law of C, Si and Mn on the phase transformation of the material to ensure the Strength and ductility.
为了实现上述目的，本发明提出了一种延展性优异的高强度钢，其化学元素质量百分比为：In order to achieve the above objective, the present invention proposes a high-strength steel with excellent ductility, the mass percentage of chemical elements is:
C：0.15～0.25wt％；C: 0.15～0.25wt%;
Si：1.00～2.00wt％；Si: 1.00～2.00wt%;
Mn：1.50～3.00wt％；Mn: 1.50～3.00wt%;
Al：0.03～0.06wt％；Al: 0.03～0.06wt%;
余量为Fe和其他不可避免的杂质。The balance is Fe and other unavoidable impurities.
在本发明所述的技术方案中，其采用了普通碳硅锰钢成分设计，充分利用了C、Si、Mn元素对材料相变的影响规律，从而在实现了本发明所述的高强度钢在高强度与高延展性的统一，从而最终得到性能优异的钢板产品。各化学元素的设计原理具体如下所述：In the technical scheme of the present invention, it adopts the composition design of ordinary carbon-silicon-manganese steel and makes full use of the influence law of C, Si, Mn on the phase transformation of the material, thereby realizing the high-strength steel of the present invention. In the unification of high strength and high ductility, a steel plate product with excellent performance is finally obtained. The design principles of each chemical element are as follows:
C：在本发明所述的延展性优异的高强度钢中，C在奥氏体中的溶解度远高于其在铁素体中的溶解度，可延长奥氏体转变前的孕育期，降低Ms温度。C的质量百分比越高，残余奥氏体的分数越多，配分时C在残余奥氏体中的富集程度越高，有利于增强残余奥氏体稳定性，产生TRIP效应，提高材料延展性。此外，C也是钢中最基本的固溶强化元素。但质量百分比过高的C会降低钢的焊接性。此外，当钢中的C的质量百分比超过0.25％时，淬火后容易出现较多孪晶，增加裂纹敏感性。基于此，在本发明所述的延展性优异的高强度钢中，将C的质量百分比控制在0.15～0.25wt％。C: In the high-strength steel with excellent ductility of the present invention, the solubility of C in austenite is much higher than its solubility in ferrite, which can prolong the incubation period before austenite transformation and reduce Ms temperature. The higher the mass percentage of C, the more the fraction of retained austenite, and the higher the concentration of C in retained austenite during partitioning, which is beneficial to enhance the stability of retained austenite, produce TRIP effect, and improve the ductility of the material. . In addition, C is also the most basic solid solution strengthening element in steel. However, an excessively high mass percentage of C will reduce the weldability of the steel. In addition, when the mass percentage of C in the steel exceeds 0.25%, more twins are prone to appear after quenching, which increases crack sensitivity. Based on this, in the high-strength steel with excellent ductility according to the present invention, the mass percentage of C is controlled at 0.15-0.25 wt%.
Si：在本发明所述的延展性优异的高强度钢中，Si在碳化物中的溶解度极小，在配分处理过程中强烈抑制渗碳体形成，促进碳向残余奥氏体中富集，提高残余奥氏体的稳定性。但是Si的质量百分比过高会降低钢的高温塑性，增大热轧缺陷发生率，同时，Si的质量百分比较高时会在钢板表面形成稳定氧化物，降低钢板的润湿性。基于此，在本发明所述的延展性优异的高强度钢中将Si的质量百分比控制在1.00～2.00wt％。Si: In the high-strength steel with excellent ductility described in the present invention, the solubility of Si in carbides is extremely small, and the formation of cementite is strongly inhibited during the partitioning process, and carbon is concentrated in retained austenite. Improve the stability of retained austenite. However, if the mass percentage of Si is too high, it will reduce the high-temperature plasticity of the steel and increase the incidence of hot rolling defects. At the same time, when the mass percentage of Si is high, stable oxides will be formed on the surface of the steel sheet, reducing the wettability of the steel sheet. Based on this, the mass percentage of Si in the high-strength steel with excellent ductility according to the present invention is controlled at 1.00 to 2.00 wt%.
Mn：在本发明所述的延展性优异的高强度钢中，Mn能扩大奥氏体相区，降低Ac3、Ms和Mf点，提高奥氏体稳定性和钢的淬透性，降低临界转变速率，有利于残余奥氏体保存至室温，同时，Mn在钢中也能起到固溶强化效果。但是Mn的质量百分比过高，会加剧晶粒粗化趋势，降低钢的塑性和韧性，恶化耐腐蚀性能和焊接性能。但是若Mn的质量百分比过低，由于偏析会导致低冷速下产生铁素体、珠光体带状组织。基于此，在本发明所述的延展性优异的高强度钢中将Mn的质量百分比控制在1.50～3.00wt％。Mn: In the high-strength steel with excellent ductility described in the present invention, Mn can expand the austenite phase region, reduce Ac3, Ms and Mf points, improve the stability of austenite and the hardenability of steel, and reduce critical transformation The speed is beneficial to the preservation of retained austenite to room temperature. At the same time, Mn can also play a solid solution strengthening effect in steel. However, if the mass percentage of Mn is too high, it will aggravate the tendency of grain coarsening, reduce the plasticity and toughness of steel, and deteriorate corrosion resistance and welding performance. However, if the mass percentage of Mn is too low, the segregation will cause ferrite and pearlite banded structures to be produced at low cooling rates. Based on this, the mass percentage of Mn in the high-strength steel with excellent ductility according to the present invention is controlled to be 1.50 to 3.00 wt%.
Al：在本发明所述的延展性优异的高强度钢中，Al以固溶态存在时，能增加层错能，抑制渗碳体析出和γ到马氏体转变，提高奥氏体稳定性。并且Al与C、N形 成细小弥散分布的难溶质点，可以细化晶粒，但是Al的强化效果弱于Si，稳定奥氏体的能力也较Si弱。此外，Al的质量百分比过高，容易形成大量氧化物夹杂，不利于炼钢连铸。因此，在本发明所述的延展性优异的高强度钢中控制Al的质量百分比在0.03～0.06wt％。Al: In the high-strength steel with excellent ductility of the present invention, when Al exists in a solid solution state, it can increase the stacking fault energy, inhibit the precipitation of cementite and the transformation of γ to martensite, and improve the stability of austenite . In addition, Al, C and N form fine and dispersed insoluble points, which can refine grains, but the strengthening effect of Al is weaker than that of Si, and the ability to stabilize austenite is also weaker than that of Si. In addition, the mass percentage of Al is too high to easily form a large number of oxide inclusions, which is not conducive to steelmaking and continuous casting. Therefore, the mass percentage of Al in the high-strength steel with excellent ductility according to the present invention is controlled to be 0.03 to 0.06 wt%.
进一步地，在本发明所述的延展性优异的高强度钢中，其各化学元素的质量百分比满足下列各项的至少其中之一：Further, in the high-strength steel with excellent ductility according to the present invention, the mass percentage of each chemical element satisfies at least one of the following items:
C：0.17～0.23wt％；C: 0.17～0.23wt%;
Si：1.4～1.8wt％；Si: 1.4～1.8wt%;
Mn：1.8～2.3wt％。Mn: 1.8 to 2.3 wt%.
进一步地，在本发明所述的延展性优异的高强度钢中，还含有下列各元素的至少其中之一：Furthermore, the high-strength steel with excellent ductility according to the present invention also contains at least one of the following elements:
Cr≤0.5wt％；Cr≤0.5wt%;
Mo≤0.5wt％；Mo≤0.5wt%;
Nb≤0.05wt％；Nb≤0.05wt%;
Ti≤0.05wt％；Ti≤0.05wt%;
V≤0.05wt％；V≤0.05wt%;
B≤0.001wt％。B≤0.001wt%.
上述的Cr、Mo、Nb、Ti、V以及B可以进一步提高本发明所述的高强度钢的性能。例如：Cr、Mo可以提高钢的淬透性，调节钢的强度，但是Cr会在钢板表面发生富集，影响焊接性能，而Mo的质量百分比较高导致钢的冷轧变形抗力增大。又例如：Nb、Ti、V元素可以与C形成细小的碳化物，促进组织细化，但是此类细小碳化物的形成不利于C向残余奥氏体中富集与残余奥氏体的稳定化。再例如：B的主要作用是提高钢的淬透性，B容易在奥氏体晶界偏聚，延缓奥氏体向铁素体转变，钢中加入少量即可起到明显作用，B的质量百分比过高会引起钢强度升高，不利于得到良好塑形。因此，可以将B的质量百分比控制在B≤0.001％。The aforementioned Cr, Mo, Nb, Ti, V, and B can further improve the performance of the high-strength steel according to the present invention. For example: Cr and Mo can improve the hardenability of steel and adjust the strength of steel, but Cr will be enriched on the surface of the steel plate, which affects the welding performance, and the higher mass percentage of Mo leads to the increase of the cold-rolled deformation resistance of the steel. Another example: Nb, Ti, V elements can form fine carbides with C to promote structure refinement, but the formation of such fine carbides is not conducive to the enrichment of C into retained austenite and the stabilization of retained austenite . Another example: The main function of B is to improve the hardenability of steel. B is easy to segregate at the austenite grain boundary and delay the transformation of austenite to ferrite. Adding a small amount to the steel can play a significant role. The quality of B Too high a percentage will increase the strength of the steel, which is not conducive to good shaping. Therefore, the mass percentage of B can be controlled at B≤0.001%.
此外，上述元素的加入会增加材料的成本，综合考虑到性能与成本控制，在本发明所述的技术方案中，可以优选地添加上述元素的至少其中之一。In addition, the addition of the above-mentioned elements will increase the cost of the material. Considering the performance and cost control comprehensively, in the technical solution of the present invention, at least one of the above-mentioned elements can be preferably added.
更进一步地，在本发明所述的延展性优异的高强度钢中，其中各化学元素满足下列各项的至少其中之一：Furthermore, in the high-strength steel with excellent ductility according to the present invention, each chemical element satisfies at least one of the following items:
Cr≤0.25wt％；优选地，Cr≤0.05wt％；Cr≤0.25wt%; preferably, Cr≤0.05wt%;
Mo≤0.25wt％；优选地，Mo≤0.20wt％；Mo≤0.25wt%; preferably, Mo≤0.20wt%;
Nb≤0.025wt％；优选地，Nb≤0.015wt％；Nb≤0.025wt%; preferably, Nb≤0.015wt%;
Ti≤0.02wt％；Ti≤0.02wt%;
V≤0.02wt％；优选地，V≤0.01wt％。V≤0.02wt%; preferably, V≤0.01wt%.
进一步地，在本发明所述的延展性优异的高强度钢中，在其他不可避免的杂质中：P≤0.015wt％，S≤0.012wt％，N≤0.008wt％。Further, in the high-strength steel with excellent ductility according to the present invention, among other unavoidable impurities: P≤0.015wt%, S≤0.012wt%, and N≤0.008wt%.
上述方案中，P、S、N为杂质，其中，P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P含的质量百分比过高会弱化晶界，增大材料脆性，恶化焊接性能，也就是说P的正面作用弱于其负面作用，因此，优选地将P的质量百分比控制在P≤0.015wt％。而至于N，由于N的质量百分比过高会给炼钢、连铸带来困难，不利于夹杂物控制，因此，优选地将N的质量百分比控制在N≤0.008wt％。In the above scheme, P, S, and N are impurities. Although P can play a solid solution strengthening effect and inhibit the formation of carbides, it is beneficial to improve the stability of retained austenite. However, if the mass percentage of P is too high, it will weaken The grain boundary increases the brittleness of the material and deteriorates the welding performance, that is, the positive effect of P is weaker than its negative effect. Therefore, it is preferable to control the mass percentage of P to P≤0.015wt%. As for N, too high mass percentage of N will bring difficulties to steelmaking and continuous casting, and is not conducive to the control of inclusions. Therefore, it is preferable to control the mass percentage of N to N≤0.008wt%.
进一步地，在本发明所述的延展性优异的高强度钢中，其微观组织为30％～50％的铁素体+40％～60％的马氏体+残余奥氏体。Furthermore, in the high-strength steel with excellent ductility according to the present invention, the microstructure is 30% to 50% ferrite + 40% to 60% martensite + retained austenite.
进一步地，在本发明所述的延展性优异的高强度钢中，其中在铁素体中，10μm以下的晶粒占比80％以上，5μm以下的晶粒占比50％以上。Furthermore, in the high-strength steel with excellent ductility according to the present invention, in ferrite, grains of 10 μm or less account for 80% or more, and grains of 5 μm or less account for 50% or more of ferrite.
进一步地，在本发明所述的延展性优异的高强度钢中，其中残余奥氏体的平均晶粒尺寸≤2μm；并且/或者残余奥氏体中平均C含量≥1.1wt％。在一些实施方案中，残余奥氏体的平均晶粒尺寸在0.3-2μm的范围内。在一些实施方案中，残余奥氏体中平均C含量为1.1wt％到1.5wt％，如1.1wt％到1.3wt％。Further, in the high-strength steel with excellent ductility according to the present invention, the average grain size of the retained austenite is less than or equal to 2 μm; and/or the average C content in the retained austenite is more than or equal to 1.1 wt%. In some embodiments, the average grain size of retained austenite is in the range of 0.3-2 μm. In some embodiments, the average C content in the retained austenite is 1.1 wt% to 1.5 wt%, such as 1.1 wt% to 1.3 wt%.
进一步地，在本发明所述的延展性优异的高强度钢中，其屈服强度为550～850MPa，抗拉强度为900～1100MPa，均匀延伸率(UEL)≥13％，断裂延伸率(TEL)为18％～28％。在一些实施方案中，均匀延伸率为13-19％。Furthermore, in the high-strength steel with excellent ductility of the present invention, the yield strength is 550-850MPa, the tensile strength is 900-1100MPa, the uniform elongation (UEL) is ≥13%, and the elongation at break (TEL) It is 18%-28%. In some embodiments, the uniform elongation is 13-19%.
相应地，本发明的另一目的在于提供上述的延展性优异的高强度钢的制造方法，该制造方法通过采用薄板坯连铸工艺配合酸洗或酸轧工艺，在连续退火后获得延展性优异的高强度钢。该制造方法生产简单，所得到的高强度钢在同等强度条件下，延伸率得到显著提高。Correspondingly, another object of the present invention is to provide the above-mentioned manufacturing method of high-strength steel with excellent ductility. The manufacturing method adopts a thin slab continuous casting process combined with a pickling or pickling process to obtain excellent ductility after continuous annealing. Of high-strength steel. The manufacturing method is simple to produce, and the obtained high-strength steel has a significantly improved elongation under the same strength condition.
为了实现上述目的，本发明提出了上述的延展性优异的高强度钢的制造方法，其包括步骤：In order to achieve the above-mentioned object, the present invention proposes the above-mentioned manufacturing method of high-strength steel with excellent ductility, which includes the following steps:
(1)冶炼和薄板坯连铸：其中连铸出口端的板坯厚度控制为52～60mm，优选 55～60mm；(1) Smelting and thin slab continuous casting: The thickness of the slab at the exit end of the continuous casting is controlled to be 52-60mm, preferably 55-60mm;
(2)加热；(2) Heating;
(3)热轧：热轧后钢带表面氧化皮厚度≤5μm，并且热轧后带钢表面氧化皮中的(FeO+Fe 3O 4)≤40wt％； (3) Hot rolling: The thickness of the oxide scale on the surface of the steel strip after hot rolling is ≤5μm, and the (FeO+Fe 3 O 4 ) in the oxide scale on the surface of the strip after hot rolling is ≤40wt%;
(4)酸洗或者酸洗+冷轧；(4) Pickling or pickling + cold rolling;
(5)连续退火：在800～920℃退火，以3～10℃/s的冷速缓冷至680～750℃，以获得一定比例的铁素体；再快冷至220～320℃，冷却速度为50～1000℃/s，使奥氏体部分转变为马氏体；然后再加热至360～460℃，保温100～500s，最后冷却至室温。(5) Continuous annealing: annealing at 800～920℃, slowly cooling to 680～750℃ at a cooling rate of 3～10℃/s to obtain a certain proportion of ferrite; then quickly cooling to 220～320℃, cooling The speed is 50-1000°C/s to partially transform austenite into martensite; then it is heated to 360-460°C for 100-500s, and finally cooled to room temperature.
在本发明所述的技术方案中，由于步骤(1)采用的是薄板坯连铸，因此，可以省却粗轧工序，减小热轧变形量，从而保证在后续的步骤(4)以及步骤(5)的钢板性能。此外，由于步骤(1)采用的是薄板坯连铸，其可以充分利用板坯热量，降低加热所需能耗，从而获得更加均匀的铁素体或铁素体+珠光体组织，有利于步骤5)中的成品微观组织中保持一定量的细晶粒铁素体，提高组织均匀性。In the technical solution of the present invention, since step (1) adopts thin slab continuous casting, the rough rolling process can be omitted, and the deformation of hot rolling can be reduced, thereby ensuring that the subsequent steps (4) and step ( 5) The performance of the steel plate. In addition, since step (1) adopts thin slab continuous casting, it can make full use of the heat of the slab and reduce the energy consumption required for heating, thereby obtaining a more uniform ferrite or ferrite + pearlite structure, which is beneficial to the step 5) Maintain a certain amount of fine-grained ferrite in the microstructure of the finished product to improve the uniformity of the structure.
而在步骤(3)中，控制热轧后钢带表面氧化皮厚度≤5μm，并且热轧后带钢表面氧化皮中的(FeO+Fe 3O 4)≤40wt％，可以有利于后续在步骤(4)的进行，并对连续退火后所获得的钢板性能有着重要影响，这是因为：在本发明所述的技术方案中，FeO、Fe 3O 4比Fe 2O 3更加难酸洗，而当控制本案的热轧后钢带表面氧化皮厚度以及热轧后带钢表面氧化皮中的(FeO+Fe 3O 4)≤40wt％可以使得提高酸洗效果，获得可用于直接连续托获得酸洗板表面，而由于酸洗板可以直接进行连续退火，使得热轧组织变形量小，钢板组织以珠光体与铁素体为主，因而，在相同连续退火条件下可以降低材料强度，使得组织更加均匀，从而获得优异的延展性。 In step (3), controlling the thickness of the scale on the surface of the steel strip after hot rolling to be ≤5μm, and the (FeO+Fe 3 O 4 ) in the scale on the surface of the steel strip after the hot rolling is ≤ 40wt%, which can be beneficial to the subsequent steps The progress of (4) has an important influence on the performance of the steel sheet obtained after continuous annealing. This is because: in the technical scheme of the present invention, FeO and Fe 3 O 4 are more difficult to pickle than Fe 2 O 3, However, when controlling the thickness of the oxide scale on the surface of the steel strip after hot rolling in this case and the (FeO+Fe 3 O 4 )≤40wt% in the oxide scale on the surface of the strip after hot rolling, the pickling effect can be improved, and the result can be used for direct continuous support. The surface of the pickled plate, and because the pickled plate can be directly annealed continuously, the deformation of the hot-rolled structure is small. The structure of the steel plate is mainly pearlite and ferrite. Therefore, the material strength can be reduced under the same continuous annealing conditions, so that The structure is more uniform, so as to obtain excellent ductility.
而在步骤(5)中，通过控制退火温度可以形成均匀化的奥氏体组织或奥氏体+铁素体组织；然后以3～10℃/s的冷速缓冷至660～750℃，优选680-750℃，以进一步调整组织中铁素体的含量，提高材料的塑形；之后以50～1000℃/s、优选50-600℃、更优选50-100℃的速度冷却至220～320℃(即介于Ms与Mf温度之间)，此时，奥氏体部分转变为马氏体，保证钢具有较高的强度；再加热至360～460℃并保温100～500s，如100-300s，使碳在马氏体和奥氏体中发生配分，形成一定量富碳的残余奥氏体，稳定保持到室温，由于TRIP效应，可以显著提高钢的加工硬化能力和成形性，得到延展性优异的高强度钢板。In step (5), a uniform austenite structure or austenite + ferrite structure can be formed by controlling the annealing temperature; then slowly cool to 660-750°C at a cooling rate of 3-10°C/s, Preferably 680-750°C to further adjust the content of ferrite in the structure and improve the shaping of the material; then cool to 220-320 at a rate of 50-1000°C/s, preferably 50-600°C, more preferably 50-100°C ℃ (that is, between Ms and Mf temperature), at this time, austenite is partially transformed into martensite to ensure that the steel has higher strength; then heat to 360～460℃ and keep for 100～500s, such as 100- 300s, the carbon is partitioned between martensite and austenite to form a certain amount of carbon-rich retained austenite, which is kept stable to room temperature. Due to the TRIP effect, the work hardening ability and formability of the steel can be significantly improved, and the ductility can be obtained. High-strength steel sheet with excellent performance.
由于本案的高强度钢采用的是采用高碳、高锰设计及铁素体晶粒细化，因而， 在连续退火过程中，奥氏体逆相变的形核点增多的同时，尺寸进一步细化，稳定保持到室温的残余奥氏体的平均晶粒尺寸可以≤2μm；残余奥氏体中平均C含量≥1.1wt％。另外，由于采用高Si设计，因而，快速冷却形成的马氏体在配分过程中基本不发生分解，以保证组织中马氏体的含量，从而保证钢的强度。Because the high-strength steel in this case adopts high-carbon, high-manganese design and ferrite grain refinement, during the continuous annealing process, the nucleation point of the reverse phase transformation of austenite increases while the size is further refined. The average grain size of the retained austenite that is stably maintained to room temperature can be ≤2μm; the average C content in the retained austenite is ≥1.1wt%. In addition, due to the high Si design, the martensite formed by rapid cooling basically does not decompose during the partitioning process to ensure the content of martensite in the structure, thereby ensuring the strength of the steel.
进一步地，在本发明所述的制造方法中，在步骤(1)中，控制连铸拉速为2～5m/min。Further, in the manufacturing method of the present invention, in step (1), the continuous casting drawing speed is controlled to be 2-5 m/min.
进一步地，在本发明所述的制造方法中，在步骤(2)中，将板坯加热到1200～1250℃。Further, in the manufacturing method of the present invention, in step (2), the slab is heated to 1200-1250°C.
进一步地，在本发明所述的制造方法中，在步骤(3)中，控制终轧温度为860～930℃，卷取温度为450～600℃。Further, in the manufacturing method of the present invention, in step (3), the finishing rolling temperature is controlled to be 860 to 930°C, and the coiling temperature is to be 450 to 600°C.
进一步地，在本发明所述的制造方法中，在步骤(4)中，当采用酸洗+冷轧步骤时，控制其变形量为30％～70％。Further, in the manufacturing method of the present invention, in step (4), when the pickling + cold rolling step is adopted, the deformation is controlled to be 30% to 70%.
进一步地，在本发明所述的制造方法中，在步骤(5)中，控制连续退火炉内还原性气氛中氢气的体积含量10～15％。Further, in the manufacturing method of the present invention, in step (5), the volume content of hydrogen in the reducing atmosphere in the continuous annealing furnace is controlled to 10-15%.
进一步地，在本发明所述的制造方法，在步骤(5)中，控制连续退火工艺满足下述各项的至少其中之一：Further, in the manufacturing method of the present invention, in step (5), the continuous annealing process is controlled to satisfy at least one of the following items:
退火温度820～870℃；Annealing temperature is 820～870℃;
以3～10℃/s的冷速缓冷至700～730℃；Slowly cool to 700～730℃ at a cooling rate of 3～10℃/s;
快冷至280～320℃；Fast cooling to 280～320℃;
快冷后再加热至400～430℃，保温180～300s；After rapid cooling, heat to 400～430℃ and keep for 180～300s;
控制连续退火炉内还原性气氛中氢气的体积含量10～15％。The volume content of hydrogen in the reducing atmosphere in the continuous annealing furnace is controlled to 10-15%.
本发明所述的延展性优异的高强度钢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：Compared with the prior art, the high-strength steel with excellent ductility and its manufacturing method according to the present invention have the following advantages and beneficial effects:
本发明所述的高强度钢以碳硅锰钢为基础，不添加任何昂贵的合金元素，通过优化碳硅锰配比，获得具有优异延展性的高强度冷轧钢板。The high-strength steel of the present invention is based on carbon-silicon-manganese steel without adding any expensive alloy elements, and by optimizing the ratio of carbon-silicon-manganese, a high-strength cold-rolled steel sheet with excellent ductility is obtained.
本发明所述的制造方法生产工艺简单，所获得的高强度钢在同等强度条件下，延伸率可显著提高，在汽车安全结构件中将具有较好的应用前景，特别适合于制造形状复杂、对成形性能要求高的车辆结构件和安全件，如A/B柱、纵梁、车门防撞杆、保险杠等。The manufacturing method of the present invention has a simple production process, and the obtained high-strength steel can significantly increase its elongation under the same strength conditions. It will have a good application prospect in automobile safety structural parts, and is particularly suitable for manufacturing complex shapes, Vehicle structural parts and safety parts that require high formability, such as A/B pillars, longitudinal beams, door anti-collision bars, bumpers, etc.
附图说明Description of the drawings
图1为实施例12的高强度钢的微观组织照片。Fig. 1 is a microstructure photograph of the high-strength steel of Example 12.
图2为实施例12的高强度钢的相组成EBSD照片。Fig. 2 is an EBSD photograph of the phase composition of the high-strength steel of Example 12.
具体实施方式Detailed ways
下面将结合说明书附图以及具体的实施例对本发明所述的延展性优异的高强度钢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。Hereinafter, the high-strength steel with excellent ductility and the manufacturing method thereof will be further explained and described in conjunction with the drawings and specific embodiments of the specification. However, the explanation and description do not improperly limit the technical solution of the present invention.
实施例1-36以及对比例1-3Examples 1-36 and Comparative Examples 1-3
实施例1-36的延展性优异的高强度钢采用以下步骤制得：The high-strength steel with excellent ductility of Examples 1-36 was prepared by the following steps:
(1)按照表1所示的化学成分进行冶炼和薄板坯连铸：其中连铸出口端的板坯厚度控制为52～60mm，并且控制连铸坯拉速为2～5m/min。(1) Smelting and thin slab continuous casting are carried out in accordance with the chemical composition shown in Table 1: The thickness of the slab at the exit end of the continuous casting is controlled to be 52-60mm, and the drawing speed of the continuous casting slab is controlled to be 2-5m/min.
(2)加热：将板坯加热到1200～1250℃。(2) Heating: The slab is heated to 1200-1250°C.
(3)热轧：热轧后钢带表面氧化皮厚度≤5μm，并且热轧后带钢表面氧化皮中的(FeO+Fe 3O 4)≤40wt％，控制终轧温度为860～930℃，卷取温度为450～600℃。 (3) Hot rolling: The thickness of the oxide scale on the surface of the steel strip after hot rolling is ≤5μm, and the (FeO+Fe 3 O 4 ) in the oxide scale on the surface of the strip after hot rolling is ≤40wt%, and the final rolling temperature is controlled at 860～930℃ , The coiling temperature is 450～600℃.
(4)酸洗或者酸洗+冷轧：当采用酸洗+冷轧步骤时，控制其变形量为30％～70％。(4) Pickling or pickling + cold rolling: When pickling + cold rolling is used, the deformation is controlled to be 30% to 70%.
(5)连续退火：在800～920℃退火，以3～10℃/s的冷速缓冷至660～750℃，以获得一定比例的铁素体；再快冷至220～320℃，冷却速度为50～1000℃/s，使奥氏体部分转变为马氏体；然后再加热至360～460℃，保温100～500s，最后冷却至室温。控制连续退火炉内还原性气氛中氢气的体积含量10～15％。(5) Continuous annealing: annealing at 800～920℃, slowly cooling to 660～750℃ at a cooling rate of 3～10℃/s to obtain a certain proportion of ferrite; then quickly cooling to 220～320℃, cooling The speed is 50-1000°C/s to partially transform austenite into martensite; then it is heated to 360-460°C for 100-500s, and finally cooled to room temperature. The volume content of hydrogen in the reducing atmosphere in the continuous annealing furnace is controlled to 10-15%.
需要说明的是，在一些优选的实施方式中，在步骤(5)中，可以进一步控制参数满足下述各项的至少其中之一：It should be noted that, in some preferred embodiments, in step (5), the control parameters can be further controlled to satisfy at least one of the following items:
退火温度820～870℃；Annealing temperature is 820～870℃;
以3～10℃/s的冷速缓冷至700～730℃；Slowly cool to 700～730℃ at a cooling rate of 3～10℃/s;
快冷至280～320℃；Fast cooling to 280～320℃;
快冷后再加热至400～430℃，保温180～300s；After rapid cooling, heat to 400～430℃ and keep for 180～300s;
控制连续退火炉内还原性气氛中氢气的体积含量10～15％。The volume content of hydrogen in the reducing atmosphere in the continuous annealing furnace is controlled to 10-15%.
而对比例1-3则采用常规工艺制造获得。The comparative examples 1-3 were manufactured using conventional processes.
表1列出了实施例1-36的延展性优异的高强度钢以及对比例1-3的对比钢的各 化学元素的质量百分配比。Table 1 lists the mass percentage ratios of the chemical elements of the high-strength steel with excellent ductility of Examples 1-36 and the comparative steel of Comparative Examples 1-3.
表1.(wt％，余量为Fe和除了P、S以及N以外的其他不可避免的杂质)Table 1. (wt%, the balance is Fe and other unavoidable impurities except P, S and N)
Figure PCTCN2020122085-appb-000001
Figure PCTCN2020122085-appb-000001
表2-1以及表2-2列出了实施例1-36的延展性优异的高强度钢以及对比例1-3的对比钢的具体工艺参数。Table 2-1 and Table 2-2 list the specific process parameters of the high-strength steel with excellent ductility in Examples 1-36 and the comparative steel in Comparative Examples 1-3.
表2-1.table 2-1.
Figure PCTCN2020122085-appb-000002
Figure PCTCN2020122085-appb-000002
Figure PCTCN2020122085-appb-000003
Figure PCTCN2020122085-appb-000003
表2-2.Table 2-2.
Figure PCTCN2020122085-appb-000004
Figure PCTCN2020122085-appb-000004
Figure PCTCN2020122085-appb-000005
Figure PCTCN2020122085-appb-000005
表3列出了实施例1-36的延展性优异的高强度钢以及对比例1-3的对比钢的力学性能测试结果。Table 3 lists the mechanical performance test results of the high-strength steel with excellent ductility in Examples 1-36 and the comparative steel in Comparative Examples 1-3.
表3.table 3.
Figure PCTCN2020122085-appb-000006
Figure PCTCN2020122085-appb-000006
Figure PCTCN2020122085-appb-000007
Figure PCTCN2020122085-appb-000007
由表3可以看出，本案实施例1-36的延展性优异的高强度钢在保证强度的同时，延展性能表面优异，其屈服强度为550～850MPa，抗拉强度为900～1100MPa，均匀延伸率≥13％，断裂延伸率为18％～28％。It can be seen from Table 3 that the high-strength steel with excellent ductility in Examples 1-36 of this case guarantees its strength and has excellent ductility surface. Its yield strength is 550-850 MPa, and its tensile strength is 900-1100 MPa. The rate is ≥13%, and the elongation at break is 18%-28%.
表4实施例1-36的延展性优异的高强度钢的微观组织观察结果。Table 4 Observation results of the microstructure of the high-strength steel with excellent ductility in Examples 1-36.
表4.Table 4.
Figure PCTCN2020122085-appb-000008
Figure PCTCN2020122085-appb-000008
Figure PCTCN2020122085-appb-000009
Figure PCTCN2020122085-appb-000009
结合表3和表4可以看出，本案实施例1-36的延展性优异的高强度钢的微观组织为30％～50％的铁素体+40％～60％的马氏体+残余奥氏体，其中在铁素体中，10μm以下的晶粒占比80％以上，5μm以下的晶粒占比50％以上，残余奥氏体的平均晶粒尺寸≤2μm；并且/或者残余奥氏体中平均C含量≥1.1wt％。由此，说明了本案各实施例的延展性优异的高强度钢由于具有一定量的细晶粒铁素体，并组织均匀性好，因而，使得各个实施例的高强度钢可以在强度高的同时具有极好的延展性。Combining Table 3 and Table 4, it can be seen that the microstructure of the high-strength steel with excellent ductility in Examples 1-36 of this case is 30% to 50% ferrite + 40% to 60% martensite + retained austenite In the ferrite, the grains below 10μm account for more than 80%, the grains below 5μm account for more than 50%, and the average grain size of retained austenite is ≤2μm; and/or retained austenite The average C content in the body is ≥1.1wt%. Thus, it is explained that the high-strength steel with excellent ductility in each embodiment of this case has a certain amount of fine-grained ferrite and good microstructure uniformity, so that the high-strength steel of each embodiment can be used in high-strength steels. At the same time, it has excellent ductility.
图1为实施例12的高强度钢的微观组织照片。图2为实施例12的高强度钢的 相组成EBSD照片。Fig. 1 is a photo of the microstructure of the high-strength steel of Example 12. Fig. 2 is an EBSD photograph of the phase composition of the high-strength steel of Example 12.
结合图1和图2可以看出，实施例12的高强度钢的微观组织为30％～50％的铁素体+40％～60％的马氏体+残余奥氏体，其中在铁素体中，10μm以下的晶粒占比80％以上，5μm以下的晶粒占比50％以上，残余奥氏体的平均晶粒尺寸≤2μm；并且/或者残余奥氏体中平均C含量≥1.1wt％。Combining Figure 1 and Figure 2, it can be seen that the microstructure of the high-strength steel of Example 12 is 30% to 50% ferrite + 40% to 60% martensite + retained austenite. In the body, the grains below 10μm account for more than 80%, the grains below 5μm account for more than 50%, the average grain size of retained austenite is ≤2μm; and/or the average C content in retained austenite is ≥1.1 wt%.
综上所述可以看出，本发明所述的高强度钢以碳硅锰钢为基础，不添加任何昂贵的合金元素，通过优化碳硅锰配比，获得具有优异延展性的高强度冷轧钢板。In summary, it can be seen that the high-strength steel of the present invention is based on carbon-silicon-manganese steel without adding any expensive alloying elements. By optimizing the ratio of carbon-silicon-manganese, high-strength cold-rolled steel with excellent ductility is obtained. Steel plate.
本发明所述的制造方法生产工艺简单，所获得的高强度钢在同等强度条件下，延伸率可显著提高，在汽车安全结构件中将具有较好的应用前景，特别适合于制造形状复杂、对成形性能要求高的车辆结构件和安全件，如A/B柱、纵梁、车门防撞杆、保险杠等。The manufacturing method of the present invention has a simple production process, and the obtained high-strength steel can significantly increase its elongation under the same strength conditions. It will have a good application prospect in automobile safety structural parts, and is particularly suitable for manufacturing complex shapes, Vehicle structural parts and safety parts that require high formability, such as A/B pillars, longitudinal beams, door anti-collision bars, bumpers, etc.
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。It should be noted that the prior art part of the protection scope of the present invention is not limited to the embodiments given in this application document, and all prior art that does not contradict the solution of the present invention includes but is not limited to the previous Patent documents, prior publications, prior publications, etc., can all be included in the protection scope of the present invention.
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。In addition, the combination of various technical features in this case is not limited to the combination described in the claims of this case or the combination described in the specific embodiments. All technical features described in this case can be freely combined or combined in any way, unless Contradictions arise between each other.
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。It should also be noted that the embodiments listed above are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and the subsequent similar changes or modifications are those skilled in the art can directly derive or easily associate from the disclosure of the present invention, and they should all fall within the protection scope of the present invention. .

Claims (15)

  1. 一种延展性优异的高强度钢，其特征在于，其化学元素质量百分比为：A high-strength steel with excellent ductility, characterized in that its chemical element mass percentage is:
    C：0.15～0.25wt％；C: 0.15～0.25wt%;
    Si：1.00～2.00wt％；Si: 1.00～2.00wt%;
    Mn：1.50～3.00wt％；Mn: 1.50～3.00wt%;
    Al：0.03～0.06wt％；Al: 0.03～0.06wt%;
    余量为Fe和其他不可避免的杂质。The balance is Fe and other unavoidable impurities.
  2. 如权利要求1所述的延展性优异的高强度钢，其特征在于，其各化学元素的质量百分比满足下列各项的至少其中之一：The high-strength steel with excellent ductility according to claim 1, wherein the mass percentage of each chemical element satisfies at least one of the following items:
    C：0.17～0.23wt％；C: 0.17～0.23wt%;
    Si：1.4～1.8wt％；Si: 1.4～1.8wt%;
    Mn：1.8～2.3wt％。Mn: 1.8 to 2.3 wt%.
  3. 如权利要求1或2所述的延展性优异的高强度钢，其特征在于，还含有下列各元素的至少其中之一：The high-strength steel with excellent ductility according to claim 1 or 2, characterized in that it further contains at least one of the following elements:
    Cr≤0.5wt％；Cr≤0.5wt%;
    Mo≤0.5wt％；Mo≤0.5wt%;
    Nb≤0.05wt％；Nb≤0.05wt%;
    Ti≤0.05wt％；Ti≤0.05wt%;
    V≤0.05wt％；V≤0.05wt%;
    B≤0.001wt％。B≤0.001wt%.
  4. 如权利要求3所述的延展性优异的高强度钢，其特征在于，其中各化学元素满足下列各项的至少其中之一：The high-strength steel with excellent ductility according to claim 3, wherein each chemical element satisfies at least one of the following items:
    Cr≤0.25wt％；Cr≤0.25wt%;
    Mo≤0.25wt％；Mo≤0.25wt%;
    Nb≤0.025wt％；Nb≤0.025wt%;
    Ti≤0.02wt％；Ti≤0.02wt%;
    V≤0.02wt％。V≤0.02wt%.
  5. 如权利要求1所述的延展性优异的高强度钢，其特征在于，在其他不可避免的杂质中：P≤0.015wt％，S≤0.012wt％，N≤0.008wt％。The high-strength steel with excellent ductility according to claim 1, wherein among other unavoidable impurities: P≤0.015wt%, S≤0.012wt%, and N≤0.008wt%.
  6. 如权利要求1所述的延展性优异的高强度钢，其特征在于，其微观组织为30％～50％的铁素体+40％～60％的马氏体+残余奥氏体。The high-strength steel with excellent ductility according to claim 1, wherein the microstructure is 30% to 50% ferrite + 40% to 60% martensite + retained austenite.
  7. 如权利要求6所述的延展性优异的高强度钢，其特征在于，其中在铁素体中，10μm以下的晶粒占比80％以上，5μm以下的晶粒占比50％以上。The high-strength steel with excellent ductility according to claim 6, wherein in the ferrite, grains of 10 μm or less account for 80% or more, and grains of 5 μm or less account for 50% or more.
  8. 如权利要求6所述的延展性优异的高强度钢，其特征在于，其中残余奥氏体的平均晶粒尺寸≤2μm；并且/或者残余奥氏体中平均C含量≥1.1wt％。The high-strength steel with excellent ductility according to claim 6, wherein the average grain size of the retained austenite is ≤ 2 μm; and/or the average C content in the retained austenite is ≥ 1.1 wt%.
  9. 如权利要求1所述的延展性优异的高强度钢，其特征在于，其屈服强度为550～850MPa，抗拉强度为900～1100MPa，均匀延伸率≥13％，断裂延伸率为18％～28％。The high-strength steel with excellent ductility according to claim 1, wherein the yield strength is 550-850MPa, the tensile strength is 900-1100MPa, the uniform elongation is ≥13%, and the elongation at break is 18%-28. %.
  10. 如权利要求1-9中任意一项所述的延展性优异的高强度钢的制造方法，其特征在于，其包括步骤：The method for manufacturing high-strength steel with excellent ductility according to any one of claims 1-9, characterized in that it comprises the steps of:
    (1)冶炼和薄板坯连铸：其中连铸出口端的板坯厚度控制为52～60mm；(1) Smelting and thin slab continuous casting: the thickness of the slab at the exit end of the continuous casting is controlled to be 52-60mm;
    (2)加热；(2) Heating;
    (3)热轧：热轧后钢带表面氧化皮厚度≤5μm，并且热轧后带钢表面氧化皮中的(FeO+Fe 3O 4)≤40wt％； (3) Hot rolling: The thickness of the oxide scale on the surface of the steel strip after hot rolling is ≤5μm, and the (FeO+Fe 3 O 4 ) in the oxide scale on the surface of the strip after hot rolling is ≤40wt%;
    (4)酸洗或者酸洗+冷轧；(4) Pickling or pickling + cold rolling;
    (5)连续退火：在800～920℃退火，以3～10℃/s的冷速缓冷至660～750℃，以获得一定比例的铁素体；再快冷至220～320℃，冷却速度为50～1000℃/s，使奥氏体部分转变为马氏体；然后再加热至360～460℃，保温100～500s，最后冷却至室温。(5) Continuous annealing: annealing at 800～920℃, slowly cooling to 660～750℃ at a cooling rate of 3～10℃/s to obtain a certain proportion of ferrite; then quickly cooling to 220～320℃, cooling The speed is 50-1000°C/s to partially transform austenite into martensite; then it is heated to 360-460°C for 100-500s, and finally cooled to room temperature.
  11. 如权利要求10所述的制造方法，其特征在于，在步骤(1)中，控制连铸拉速为2～5m/min。The manufacturing method according to claim 10, characterized in that, in step (1), the continuous casting drawing speed is controlled to be 2-5 m/min.
  12. 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1200～1250℃。The manufacturing method according to claim 10, wherein in step (2), the slab is heated to 1200-1250°C.
  13. 如权利要求10所述的制造方法，其特征在于，在步骤(3)中，控制终轧温度为860～930℃，卷取温度为450～600℃。The manufacturing method according to claim 10, wherein in step (3), the finishing temperature is controlled to be 860 to 930°C, and the coiling temperature is to be 450 to 600°C.
  14. 如权利要求10所述的制造方法，其特征在于，在步骤(4)中，当采用酸洗+冷轧步骤时，控制其变形量为30％～70％。The manufacturing method according to claim 10, characterized in that, in step (4), when pickling + cold rolling is adopted, the deformation is controlled to be 30% to 70%.
  15. 如权利要求10所述的制造方法，其特征在于，在步骤(5)中，控制连续退火工艺满足下述各项的至少其中之一：The manufacturing method according to claim 10, wherein in step (5), the continuous annealing process is controlled to satisfy at least one of the following items:
    退火温度820～870℃；Annealing temperature is 820～870℃;
    以3～10℃/s的冷速缓冷至700～730℃；Slowly cool to 700～730℃ at a cooling rate of 3～10℃/s;
    快冷至280～320℃；Fast cooling to 280～320℃;
    快冷后再加热至400～430℃，保温180～300s；After rapid cooling, heat to 400～430℃ and keep for 180～300s;
    控制连续退火炉内还原性气氛中氢气的体积含量10～15％。The volume content of hydrogen in the reducing atmosphere in the continuous annealing furnace is controlled to 10-15%.
PCT/CN2020/122085 2019-10-21 2020-10-20 High-strength steel having good ductility and manufacturing method therefor WO2021078111A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN201910998434.8A CN112760554A (en) 2019-10-21 2019-10-21 High-strength steel with excellent ductility and manufacturing method thereof
CN201910998434.8 2019-10-21

Publications (1)

Publication Number Publication Date
WO2021078111A1 true WO2021078111A1 (en) 2021-04-29

Family

ID=75619625

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2020/122085 WO2021078111A1 (en) 2019-10-21 2020-10-20 High-strength steel having good ductility and manufacturing method therefor

Country Status (2)

Country Link
CN (1) CN112760554A (en)
WO (1) WO2021078111A1 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113403549B (en) * 2021-05-21 2022-08-16 鞍钢股份有限公司 1.2 GPa-grade fatigue-resistant high-formability ultrahigh-strength automobile steel and preparation method thereof
CN113403551B (en) * 2021-05-21 2022-08-16 鞍钢股份有限公司 High-yield-ratio hydrogen embrittlement-resistant cold-rolled DH980 steel plate and preparation method thereof
CN115537645A (en) * 2021-06-29 2022-12-30 宝山钢铁股份有限公司 TRIP steel, preparation method thereof, cold-rolled steel plate and hot-dip galvanized steel plate
CN115652207B (en) * 2022-11-07 2023-05-12 鞍钢股份有限公司 780 MPa-grade short-process economic cold-rolled DH steel plate and production method thereof

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1749895A1 (en) * 2005-08-04 2007-02-07 ARCELOR France Manufacture of steel sheets having high resistance and excellent ductility, products thereof
CN103805840A (en) * 2012-11-15 2014-05-21 宝山钢铁股份有限公司 Hot galvanizing super-strength steel plate with high formability and manufacturing method thereof
CN103805838A (en) * 2012-11-15 2014-05-21 宝山钢铁股份有限公司 High formability super strength cold-roll steel sheet and manufacture method thereof
WO2015151427A1 (en) * 2014-03-31 2015-10-08 Ｊｆｅスチール株式会社 High-yield-ratio high-strength cold rolled steel sheet and production method therefor
WO2015151419A1 (en) * 2014-03-31 2015-10-08 Ｊｆｅスチール株式会社 High-strength cold rolled steel sheet having high yield ratio, and production method therefor
CN106244923A (en) * 2016-08-30 2016-12-21 宝山钢铁股份有限公司 A kind of phosphorus characteristic and the excellent cold rolling high strength steel plate of forming property and manufacture method thereof
CN106244924A (en) * 2016-08-31 2016-12-21 东北大学 A kind of cold rolling quenching ductile steel and preparation method
CN106350731A (en) * 2016-08-30 2017-01-25 宝山钢铁股份有限公司 Cold-rolled high-strength steel plate with excellent phosphorization and formability and manufacturing method thereof
CN110093552A (en) * 2019-05-30 2019-08-06 安徽工业大学 A kind of high strength and ductility Q&P steel plate and preparation method thereof that welding performance is excellent

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2801061B1 (en) * 1999-11-12 2001-12-14 Lorraine Laminage PROCESS FOR PRODUCING A VERY HIGH STRENGTH HOT LAMINATED SHEET METAL FOR USE IN FORMING AND IN PARTICULAR FOR STAMPING
JP5438302B2 (en) * 2008-10-30 2014-03-12 株式会社神戸製鋼所 High yield ratio high strength hot dip galvanized steel sheet or alloyed hot dip galvanized steel sheet with excellent workability and manufacturing method thereof
JP5493986B2 (en) * 2009-04-27 2014-05-14 Ｊｆｅスチール株式会社 High-strength steel sheet and high-strength hot-dip galvanized steel sheet excellent in workability and methods for producing them
US20130133792A1 (en) * 2010-08-12 2013-05-30 Jfe Steel Corporation High-strength cold rolled sheet having excellent formability and crashworthiness and method for manufacturing the same
CN102925791B (en) * 2012-11-05 2015-01-07 武汉钢铁(集团)公司 Steel easy to pickle and production method of steel
CN106222555B (en) * 2016-08-24 2018-03-20 武汉钢铁有限公司 With the thin hot forming steel of tensile strength >=1300MPa of sheet billet Direct Rolling and production method
CN106086632B (en) * 2016-08-24 2018-01-12 武汉钢铁有限公司 With the thin hot forming steel of tensile strength >=1100MPa of sheet billet Direct Rolling and production method
CN106544485B (en) * 2016-11-08 2018-07-03 武汉钢铁有限公司 The manufacturing method of thin slab continuous casting and rolling great surface quality medium and high carbon steel
CN107475627B (en) * 2017-08-23 2018-12-21 武汉钢铁有限公司 600MPa grade analysis of producing hot rolled TRIP and manufacturing method based on CSP process
CN107557692B (en) * 2017-08-23 2019-01-25 武汉钢铁有限公司 1000MPa grade analysis of producing hot rolled TRIP and manufacturing method based on CSP process
CN107488814B (en) * 2017-08-23 2018-12-28 武汉钢铁有限公司 800MPa grade analysis of producing hot rolled TRIP and manufacturing method based on CSP process

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1749895A1 (en) * 2005-08-04 2007-02-07 ARCELOR France Manufacture of steel sheets having high resistance and excellent ductility, products thereof
CN103805840A (en) * 2012-11-15 2014-05-21 宝山钢铁股份有限公司 Hot galvanizing super-strength steel plate with high formability and manufacturing method thereof
CN103805838A (en) * 2012-11-15 2014-05-21 宝山钢铁股份有限公司 High formability super strength cold-roll steel sheet and manufacture method thereof
WO2015151427A1 (en) * 2014-03-31 2015-10-08 Ｊｆｅスチール株式会社 High-yield-ratio high-strength cold rolled steel sheet and production method therefor
WO2015151419A1 (en) * 2014-03-31 2015-10-08 Ｊｆｅスチール株式会社 High-strength cold rolled steel sheet having high yield ratio, and production method therefor
CN106244923A (en) * 2016-08-30 2016-12-21 宝山钢铁股份有限公司 A kind of phosphorus characteristic and the excellent cold rolling high strength steel plate of forming property and manufacture method thereof
CN106350731A (en) * 2016-08-30 2017-01-25 宝山钢铁股份有限公司 Cold-rolled high-strength steel plate with excellent phosphorization and formability and manufacturing method thereof
CN106244924A (en) * 2016-08-31 2016-12-21 东北大学 A kind of cold rolling quenching ductile steel and preparation method
CN110093552A (en) * 2019-05-30 2019-08-06 安徽工业大学 A kind of high strength and ductility Q&P steel plate and preparation method thereof that welding performance is excellent

Also Published As

Publication number Publication date
CN112760554A (en) 2021-05-07

Similar Documents

Publication Publication Date Title
US11279986B2 (en) Cold-rolled high-strength steel having tensile strength of not less than 1500 MPA and excellent formability, and manufacturing method therefor
WO2021078111A1 (en) High-strength steel having good ductility and manufacturing method therefor
JP6207621B2 (en) High-formability ultra-high-strength cold-rolled steel sheet and manufacturing method thereof
JP6285462B2 (en) 780 MPa class cold rolled duplex steel and method for producing the same
CN106011644B (en) High elongation rate cold rolling high strength steel plate and preparation method thereof
CN110306111A (en) A kind of thick steel plates and its manufacturing method
WO2021249446A1 (en) Ultra-high-strength steel having excellent plasticity and method for manufacturing same
CN111172466B (en) Plasticity-enhanced cold-rolled dual-phase steel with tensile strength of 590MPa and production method thereof
CN105937011B (en) Low yield strength cold rolling high strength steel plate and preparation method thereof
WO2022042733A1 (en) 780 mpa grade high-surface ultra-high reaming steel and manufacturing method therefor
JP4644075B2 (en) High-strength steel sheet with excellent hole expansibility and manufacturing method thereof
JP2019505668A (en) High yield ratio type high strength cold-rolled steel sheet and manufacturing method thereof
JP2011149066A (en) Cold rolled steel sheet, hot rolled steel sheet, and method for producing them
CN113403529A (en) 1470 MPa-level alloyed galvanized steel plate for cold stamping and preparation method thereof
US20200239976A1 (en) Cold-rolled steel sheet having excellent bendability and hole expandability and method for manufacturing same
CN114150227B (en) High-toughness hot stamping steel rolled by medium and thin slabs with Rm more than or equal to 1500MPa and production method
CN111575592A (en) Low-alloy high-strength steel with yield strength of 460MPa and production method thereof
CN112981272A (en) 980 MPa-grade cold-rolled light high-strength steel and preparation method thereof
CN107109601B (en) Composite structure steel sheet having excellent formability and method for producing same
CN109136761B (en) 980 MPa-grade high-ductility low-density austenitic steel for automobiles and preparation method thereof
CN113046644B (en) 980 MPa-grade light high-strength steel and preparation method thereof
CN113061806B (en) 1180 MPa-grade light high-strength steel and preparation method thereof
CN113061808B (en) 780 MPa-grade cold-rolled light high-strength steel and preparation method thereof
CN111647818B (en) Ultra-fine grain size thin-specification high-manganese high-aluminum steel and production method thereof
CN113584391A (en) 1700 MPa-grade hydrogen-induced delayed cracking resistant hot forming steel and preparation method thereof

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 20879095

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 20879095

Country of ref document: EP

Kind code of ref document: A1