CN115181894B - 590 MPa-level high-formability hot dip galvanized dual phase steel and rapid heat treatment hot dip galvanizing manufacturing method - Google Patents

590 MPa-level high-formability hot dip galvanized dual phase steel and rapid heat treatment hot dip galvanizing manufacturing method Download PDF

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CN115181894B
CN115181894B CN202110360526.0A CN202110360526A CN115181894B CN 115181894 B CN115181894 B CN 115181894B CN 202110360526 A CN202110360526 A CN 202110360526A CN 115181894 B CN115181894 B CN 115181894B
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steel
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dip galvanized
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CN115181894A (en
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李俊
王健
刘华飞
刘益民
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Baoshan Iron and Steel Co Ltd
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Baoshan Iron and Steel Co Ltd
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Priority to KR1020237037254A priority patent/KR20230164707A/en
Priority to EP22779095.3A priority patent/EP4317512A1/en
Priority to PCT/CN2022/084537 priority patent/WO2022206915A1/en
Priority to JP2023560361A priority patent/JP2024511848A/en
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
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    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
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    • C21D6/00—Heat treatment of ferrous alloys
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    • 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
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    • 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
    • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
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    • 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
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • 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
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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    • 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
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
    • C23C2/06—Zinc or cadmium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; 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
    • 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

Abstract

The 590 MPa-level high-formability hot dip galvanized dual phase steel and the rapid heat treatment hot dip galvanizing manufacturing method comprise the following components in percentage by mass: 0.045 to 0.105 percent of C, 0.1 to 0.4 percent of Si, 1.0 to 1.5 percent of Mn, and less than or equal to 0.0 percent of P2 percent or less of S is 0.006 percent or less, 0.02 to 0.055 percent of Al, one or two of Cr, mo, ti, nb, V percent or less of Cr+Mo+Ti+Nb+V and the balance of Fe and other unavoidable impurities. The hot galvanizing step comprises the following steps: quick heating, short-time heat preservation, quick cooling, hot galvanizing and quick cooling (hot galvanizing pure zinc GI products); quick heating, short-time heat preservation, quick cooling, hot galvanizing, reheating, alloying treatment and quick cooling (alloying hot galvanizing GA products). The invention changes the recovery of deformed structure, ferrite recrystallization and austenite transformation process in the annealing process through rapid heat treatment, increases the nucleation point of the crystal grain, shortens the growth time of the crystal grain, refines the crystal grain, improves the heat treatment efficiency and the strength and the forming performance (n) 90 Value), extending the material property interval range.

Description

590 MPa-level high-formability hot dip galvanized dual phase steel and rapid heat treatment hot dip galvanizing manufacturing method
Technical Field
The invention belongs to the technical field of rapid heat treatment of materials, and particularly relates to 590 MPa-level low-carbon low-alloy high-formability hot dip galvanized dual-phase steel (comprising a hot dip pure zinc GI product and an alloyed hot dip galvanizing GA product) and a rapid heat treatment galvanization manufacturing method.
Background
Along with the gradual improvement of energy conservation and material service safety consciousness, a plurality of automobile manufacturers select high-strength steel as automobile materials, and the automobile industry adopts hot dip galvanized high-strength steel plates to reduce the thickness of the steel plates and can improve the corrosion resistance, dent resistance, durability, large deformation impact strength, safety and the like of automobiles, so that the automobile steel plates are inevitably developed towards the directions of high strength, high toughness, corrosion resistance, easy forming and processing.
Among hot dip galvanized high strength steels for automobiles, hot dip galvanized dual phase steels are most widely used and have the best application prospect. The low-carbon low-alloy hot dip galvanized dual phase steel has the characteristics of low yield ratio, high initial work hardening rate, good strength and plasticity matching property and the like, and becomes the automobile structure stamping steel with high strength and good formability which is widely used at present.
The hot dip galvanized dual phase steel is obtained by the critical zone annealing treatment or hot rolling and cooling control of low carbon steel or low alloy high strength steel, and the microstructure mainly comprises ferrite and martensite. The hot dip galvanized dual phase steel uses the principle of "composite materials" to give full play to the advantages of each phase (ferrite and martensite) in the steel as much as possible, while the disadvantages or shortcomings of one phase are alleviated or eliminated due to the presence of other phases.
The mechanical properties of hot dip galvanized dual phase steel are mainly dependent on the following three aspects:
1. grain size of the matrix phase and alloy element distribution;
2. the size, shape, distribution, and volume fraction of the second phase;
3. the combination of the matrix and the second phase.
Therefore, how to obtain a hot dip galvanized dual phase steel product with low cost, high performance and good strong plastic matching becomes a target pursued by various large steel enterprises, and the hot dip galvanized dual phase steel product is widely focused by wide steel enterprises and automobile users.
The hot dip galvanized dual phase steel is obtained by hot dip galvanizing after a critical zone treatment process, and the process comprises the following steps: and heating the strip steel to the temperature of a two-phase critical region for heat preservation, cooling the sample to the hot plating temperature of 450-460 ℃ at a cooling speed higher than the cooling speed required by martensitic transformation, performing hot galvanizing treatment, and rapidly cooling to room temperature after hot galvanizing to obtain a certain amount of martensite and ferrite two-phase structure on the substrate.
At present, the main means for the development of hot dip galvanized dual phase steel is to change the structure property of the hot dip galvanized dual phase steel by adding alloy elements, adjusting soaking temperature, time and cooling speed in a critical annealing process.
Chinese patent CN102719751B discloses a "high strength cold rolled hot dip galvanized dual phase steel sheet and method for manufacturing the same", the dual phase steel comprises the following chemical components in weight percentage: c:0.03 to 0.15 percent of Si less than or equal to 0.15 percent, mn:1.0 to 1.75 percent, P is less than or equal to 0.015 percent, S is less than or equal to 0.012 percent, al:0.02 to 0.15 percent of Cr:0.35 to 0.75 percent of Cu:0.02 to 0.15 percent of Ti:0.01 to 0.035 percent, N is less than or equal to 0.005 percent, mn+1.20Cr+0.47Cu is less than or equal to 2.5 percent and the balance is Fe and other unavoidable impurities. The manufacturing method comprises converter smelting, external refining, continuous casting, hot continuous rolling, cold acid continuous rolling, annealing galvanization and hot dip plating, wherein a galvanized substrate with reasonable structure composition and excellent plate shape is obtained through controlled rolling and controlled cooling during rolling, and a cold-rolled hot galvanizing dual-phase steel plate with the tensile strength of 490-700 MPa is finally obtained through adopting modes of slightly slow cooling from a heating end section to a soaking section, twice fast cooling in a fast cooling section and the like during continuous annealing galvanization. The invention adopts a continuous annealing hot galvanizing mode of the traditional manufacturing process, the rapid cooling rate before plating is required to be 10-25 ℃/s, cr, cu and Ti alloy elements are added in the components to obtain good toughness matching, the alloy cost and the manufacturing difficulty are increased, and the n value of the obtained material is only about 0.16.
Chinese patent CN104831177B discloses a cold-rolled hot dip galvanized dual phase steel and a preparation method thereof, the dual phase steel comprises the following chemical components in percentage by weight: c:0.11 to 0.14 percent of Si:0.1 to 0.3 percent of Mn:1.2 to 1.5 percent, P is less than or equal to 0.01 percent, S is less than or equal to 0.01 percent, al:0.03 to 0.07 percent of Cr:0.50 to 0.7 percent of Ti:0.01 to 0.03 percent, B is less than or equal to 0.005 percent, and the balance is Fe and other unavoidable impurities. The continuous hot dip galvanizing annealing method is characterized by comprising Cr, ti and B elements, wherein the continuous hot dip galvanizing annealing method is a traditional method, the requirement of the rapid cooling rate after plating is not clearly shown, the actual performance yield strength is about 360MPa, the tensile strength is about 630MPa, and the elongation is about 22%.
Chinese patent CN105603325B discloses a "600 MPa-level vanadium-containing hot dip galvanized dual phase steel and preparation method thereof", the chemical components of the dual phase steel are as follows by weight percent: c:0.04 to 0.10 percent of Si:0.1 to 0.6 percent of Mn:1.3 to 1.9 percent of Cr:0.10 to 0.5 percent of Mo:0.05 to 0.25 percent of Al:0.01 to 0.06 percent, V:0.01 to 0.05 percent, P is less than or equal to 0.02 percent, S is less than or equal to 0.015 percent, N is less than or equal to 0.006 percent, and the balance is Fe and other unavoidable impurities. The invention reduces Cr and Mo elements by adding a small amount of V and Si elements, thereby improving the strength and the hardenability. Although V and Si elements are added in the patent, a certain amount of Cr and Mo alloy elements are still required to be added, so that the alloy cost and the manufacturing difficulty of each procedure are increased. The continuous hot galvanizing annealing is carried out in a traditional mode, the rapid cooling rate before the hot galvanizing is required to be 10-50 ℃/s, the actual yield strength is about 360-380MPa, the tensile strength is about 600-630MPa, the elongation is 23-25%, and the n value is only about 0.16-0.18.
Chinese patent CN110093491a discloses a cold-rolled hot dip galvanized dual phase steel and a method for manufacturing the same, the method comprising the steps of: 1) Heating the cold strip steel to 780-840 ℃; 2) The heated strip steel is insulated for 50 to 120 seconds at 780 to 840 ℃; 3) Cooling the heat-preserving strip steel to 650-730 ℃; 4) Rapidly cooling the strip cooled to 650-730 ℃ to the martensitic transformation temperature (M) s Point) and preserving heat for more than 3s, wherein the rapid cooling speed is not lower than 30 ℃/s; 5) Will be cooled to M s The strip steel which is below the point and is insulated is heated to the galvanization temperature of 450-470 ℃.
The invention sets the martensite quenching stage in the continuous annealing rapid cooling stage, and the strength, plasticity and stamping performance of the cold-rolled hot-dip galvanized dual-phase steel product meet the requirements; the production cost is reduced, the welding performance of the product is improved, the universality of the continuous hot galvanizing and continuous annealing dual-phase steel raw materials is realized, and the production management is simplified. The maximum technical characteristic of the patent is that the quenching is performed to M during quick cooling s Below the point temperature, enough martensitic structure is obtained, and then the martensitic structure is heated to the temperature of a zinc pot for hot galvanizing treatment; meanwhile, in order to obtain stable tissue performance, alloy elements such as Cr, ti and the like are added, continuous hot dip galvanizing annealing is performed in a traditional mode, the rapid cooling rate before the hot dip galvanizing annealing is required to be 10-50 ℃/s, the actual physical yield strength is about 360-380MPa, the tensile strength is about 600-630MPa, and the elongation is about 23-25%. The method is unfavorable for saving energy, and simultaneously, the cost and the manufacturing difficulty are increased by adding alloy elements.
Chinese patent CN101942603a discloses a "600 MPa grade cold-rolled hot-dip galvanized dual-phase steel and its preparation process", and the patent introduces a Cr-containing hot-dip galvanized dual-phase steel sheet, whose yield strength is above 350-380 MPa and tensile strength is 610-650 MPa. The components of the composition in percentage by weight are: c:0.03 to 0.16 percent of Mn:1.2 to 2.2 percent, cr:0.2 to 0.6 percent, als:0.01 to 0.08 percent, si <0.02 percent, P <0.020 percent, S <0.015 percent and the balance being iron. The sample is kept at 720-820 ℃ for 25-100 s, and then galvanized at 460 ℃ for 10-30 s. According to the invention, the hardenability and stability of the hot dip galvanized dual-phase steel are improved mainly by replacing high-cost Mo with Mn, so that the dual-phase steel with excellent comprehensive mechanical properties is obtained, however, the Mn content in the hot dip galvanized dual-phase steel is increased, and the surface of the strip steel is easy to be selectively oxidized in the high-temperature annealing process, so that the steel plate is not plated. The quality and welding performance of the galvanized surface are inevitably reduced, so that the subsequent application performance of users such as coating and welding of products is affected.
Chinese patent CN105274301B discloses a "method for producing iron-zinc alloy coated steel sheet with yield strength not less than 220 MPa", which comprises desulfurizing molten iron, smelting in a converter, and continuously casting into billets; hot rolling: rough rolling temperature is 1045 ℃, and finish rolling temperature is 880 ℃; coiling temperature is 675 ℃; cold rolling to a required thickness; continuously hot galvanizing, wherein the unit speed is 100-130m/min, and the temperature of zinc liquid is 460 ℃; rapidly cooling at a cooling speed of 43 ℃/s; and cooling by adopting aerosol after zinc-iron alloying, wherein the cooling speed is 38 ℃/s. The zinc-iron alloy coating has the advantages that on the premise of ensuring that the yield strength is 220-260MPa, the tensile strength is 300-380MPa, and the elongation is more than or equal to 43%, the surface grains of the zinc-iron alloy coating are fine, the size distribution is uniform, the occupied area ratio of voids on the surface of the coating is less than or equal to 5%, the surface is free from microcracks, and the coating is not easy to be chalked and fall off during stamping forming, namely, the 90-degree V bending test rating reaches level 2.
The invention is mainly characterized in that the zinc-iron alloy coating is rapidly cooled under the premise of ensuring the mechanical property, so as to obtain the coating performance of small surface grains, uniform size distribution, few surface hollows of the coating, no microcrack and difficult pulverization and falling-off of the coating during stamping forming. The method is just to obtain better zinc-iron alloy plating performance through rapid cooling after plating or alloying; but the structure and performance of the substrate cannot be adjusted by the process adjustment of the hot-dip plating process, so that the strength of the obtained substrate is not high.
Chinese patent 201711385129.9 discloses 780 MPa-level low-carbon low-alloy hot dip galvanized TRIP steel and a rapid heat treatment method thereof, wherein the steel comprises the following chemical components in percentage by mass: c:0.16-0.22%, si:1.2-1.6%, mn:1.6-2.2%, the balance being Fe and other unavoidable impurity elements, obtained by a rapid thermal treatment process comprising: the strip steel is rapidly heated to an austenite and ferrite two-phase region at the temperature of 790 ℃ to 830 ℃ from room temperature, and the heating rate is 40 ℃ to 300 ℃/s; heating the target temperature interval in the two-phase region for 60-100s; the strip steel is rapidly cooled to 410-430 ℃ from the temperature of the two-phase region, the cooling speed is 40-100 ℃/s, and the strip steel stays for 200-300s in the temperature region; the strip steel is reheated from 410 to 430 ℃ to 460 to 470 ℃ and immersed into a zinc pot for heat preservation. After the strip steel is galvanized, rapidly cooling the strip steel from 460-470 ℃ to room temperature (the cooling rate is 50-150 ℃/s) to obtain a hot-dip pure zinc (GI) product; after hot galvanizing, the strip steel can be reheated (the reheating rate is 10-300 ℃/s) to 480-550 ℃ for 5-20 s alloying treatment, and the strip steel is rapidly cooled (the cooling rate is 10-250 ℃/s) to room temperature after the alloying treatment to obtain an alloyed hot Galvanizing (GA) product. The method is characterized in that: the TRIP steel metallographic structure is a bainitic, ferritic and austenitic three-phase structure; the average grain size of the TRIP steel is obviously refined; tensile strength is 950-1050 MPa; the elongation rate is 21-24%; the maximum product of strong plastic can reach 24GPa percent.
The deficiencies of this patent are mainly the following:
firstly, the patent discloses a 780 MPa-level low-carbon low-alloy hot dip galvanized TRIP steel product and a process technology thereof, but the tensile strength of the TRIP steel product is 950-1050 MPa, the tensile strength of the TRIP steel product is 780 MPa-level, the use effect of a user cannot be good, the tensile strength of the TRIP steel product is 980 MPa-level, and the strength requirement of the user cannot be well met;
secondly, the patent adopts one-section rapid heating, the same rapid heating rate is adopted in the whole heating temperature interval, and the rapid heating is carried out at a speed of 40-300 ℃/s without distinguishing treatment according to the material tissue structure change of different temperature sections, so that the production cost of the rapid heating process is necessarily increased;
thirdly, the soaking time of the patent is set to be 60-100s, which is similar to that of the traditional continuous annealing, and the increase of the soaking time necessarily partially weakens the grain refining effect generated by rapid heating, which is very unfavorable for improving the strength and toughness of the material;
fourth, the patent must be subjected to a bainite isothermal treatment time of 200-300 seconds, which is practically too long for a rapid thermal treatment product to function as intended, and is unnecessary. And the increase of soaking time and isothermal treatment time is unfavorable for saving energy, reducing the investment of unit equipment and the occupied area of the unit, and is unfavorable for the high-speed stable operation of the strip steel in the furnace.
Chinese patent CN105543674B discloses a method for manufacturing cold-rolled ultra-high strength dual-phase steel with high local formability, and the high strength dual-phase steel of the invention comprises the following components in percentage by weight: c:0.08 to 0.12 percent of Si:0.1 to 0.5 percent of Mn:1.5 to 2.5 percent of Al:0.015 to 0.05 percent, and the balance of Fe and other unavoidable impurities. Selecting raw materials for the chemical components, and smelting the raw materials into casting blanks; heating the casting blank at 1150-1250 ℃ for 1.5-2 hours, and then carrying out hot rolling, wherein the hot rolling start temperature is 1080-1150 ℃, and the final rolling temperature is 880-930 ℃; cooling to 450-620 ℃ at a cooling rate of 50-200 ℃/s after rolling, and coiling to obtain a hot rolled steel plate taking bainite as a main structure type; and (3) cold rolling the hot-rolled steel plate, heating to 740-820 ℃ at a speed of 50-300 ℃/s for annealing, keeping the temperature for 30s-3min, cooling to 620-680 ℃ at a cooling speed of 2-6 ℃/s, and then performing overaging treatment for 3-5min at a cooling speed of 30-100 ℃/s to 250-350 ℃ to obtain the ferrite-martensite dual-phase structure ultra-high strength dual-phase steel. The yield strength of the ultra-high strength dual-phase steel is 650-680MPa, the tensile strength is 1023-1100MPa, the elongation is 12.3-13%, and the steel is not cracked when being bent at 180 degrees along the rolling direction.
The main characteristic of the patent is that the control of cooling condition after hot rolling is combined with the rapid heating in the continuous annealing process, namely, the strip-shaped structure is eliminated by controlling the cooling process after hot rolling, so as to realize the homogenization of the structure; and rapid heating is adopted in the subsequent continuous annealing process, so that the tissue refinement is realized on the basis of ensuring the tissue uniformity. The patent technology can be seen to adopt rapid heating annealing, and the premise is that hot rolling is carried out to obtain a hot rolling raw material taking bainite as a main structure, so that the aim is to ensure the uniformity of the structure and avoid the defect of local deformation caused by the occurrence of a strip structure.
The disadvantages of this patent are mainly:
firstly, to obtain a hot rolled raw material with a bainite structure, the hot rolled raw material has high strength and large deformation resistance, and great difficulty is brought to subsequent pickling and cold rolling production;
secondly, the understanding of the rapid heating is limited to shortening the heating time and refining the grain level, the heating rate is not divided according to the material organization structure change of different temperature sections, and the rapid heating is carried out at the speed of 50-300 ℃/s, so that the rapid heating production cost is increased;
thirdly, the soaking time is 30s-3min, and the increase of the soaking time necessarily partially weakens the grain refining effect generated by rapid heating, which is unfavorable for improving the strength and toughness of the material;
Fourth, the patent must be over-aged for 3-5 minutes, which is in fact too long for rapid heat treatment of DP steel, and is not necessary. The increase of soaking time and overaging time is not beneficial to saving energy, reducing the investment of unit equipment and the occupied area of the unit, and is not beneficial to the high-speed stable operation of strip steel in a furnace, and obviously, the method is not a rapid heat treatment process in a strict sense.
Chinese patent CN108774681a discloses a "rapid heat treatment method for high-strength steel", which adopts a ceramic plate electric heating device, and can obtain a heating rate up to 400 ℃/s, and after heating to 1000-1200 ℃, cool to room temperature at a cooling rate of approximately 3000 ℃/s. The carbon content of the steel of the invention is 0.16 to 0.55 percent, and simultaneously contains: si, mn, cr, mo and other alloying elements; the method is mainly suitable for steel wires, wire rods or steel belts with the diameter below 5 mm. The patent describes a rapid heat treatment method by electric heating of a ceramic plate, and the main purpose of the invention is to solve the problems of low heat treatment efficiency, energy waste and environmental pollution of products such as high-strength steel wires, wire rods and the like; the effect and effect of rapid heating on the material tissue properties are not mentioned; the invention does not combine the components and the tissue characteristics of the grade of steel, adopts a blower blowing cooling mode, and the fastest cooling speed is close to 3000 ℃/s, namely the instantaneous cooling speed of a high-temperature section, and the average cooling speed is less than 3000 ℃/s; meanwhile, the high-temperature section adopts too high cooling speed to produce the wide and thin strip steel, so that the problems of too high internal stress, poor plate shape of the steel plate and the like are caused, and the method is not suitable for large-scale industrialized continuous heat treatment production of the wide and thin steel plate.
Chinese patent CN107794357B and US patent US2019/0153558A1 disclose "a method for producing an ultra-high strength martensitic cold-rolled steel sheet by an ultra-rapid heating process", wherein the high strength dual-phase steel composition comprises, in weight percent: c:0.10 to 0.30 percent of Mn:0.5 to 2.5 percent of Si:0.05 to 0.3 percent of Mo:0.05 to 0.3 percent of Ti:0.01 to 0.04 percent of Cr:0.10 to 0.3 percent, B: 0.001-0.004%, P is less than or equal to 0.02%, S is less than or equal to 0.02%, and the balance is Fe and other unavoidable impurities. Mechanical properties of the dual-phase steel: yield strength Rp 0.2 More than 1100MPa, tensile strength R m =1800-2300 MPa, elongation is maximum 12.3%, uniform elongation is 5.5-6%. The invention provides an ultra-fast heating production process of an ultra-high strength martensitic cold-rolled steel plate, which is characterized in that firstly, the cold-rolled steel plate is heated to 300-500 ℃ at a speed of 1-10 ℃/s, and then is reheated to a single-phase austenite region of 850-950 ℃ at a heating speed of 100-500 ℃/s; and then, immediately cooling the steel plate to room temperature after heat preservation is not more than 5 seconds, and obtaining the ultra-high strength cold-rolled steel plate.
The disadvantages of the process described in this patent include:
firstly, the inventive steel contains more alloy elements, which brings a certain degree of difficulty to the prior process manufacture and the subsequent use by users;
Secondly, the ultra-rapid heating annealing method adopts a heat preservation time of not more than 5 seconds, which can lead to uneven distribution of alloy elements in a final product and low plasticity of the product;
thirdly, the final quick cooling adopts water quenching to cool to room temperature, and necessary tempering treatment is not carried out, so that the obtained final product has the structure property and the alloy element distribution condition in the final structure, the product cannot obtain the optimal toughness, the final product has excessive strength and insufficient plasticity and toughness;
fourth, the method of the invention causes problems of poor plate shape and surface oxidation of the steel plate due to the excessively high water quenching speed, so that the patent technology has no great practical application value or has little practical application value.
The prior researches on cold-rolled dual-phase steel products and annealing technology are based on the heating rate (5-20 ℃/s) of the prior industrial equipment to slowly heat the strip steel, so that the strip steel sequentially completes reversion, recrystallization and austenitizing phase transformation, thus the heating time is relatively long, meanwhile, the general soaking time of the conventional continuous hot galvanizing production line is required to be 1-3 min, the soaking time of the existing strip steel in a high-temperature furnace section is long, and the number of rollers in the high-temperature section is more (the number of rollers in the high-temperature furnace section is 20-40 for the conventional production line with the unit speed of about 180 meters/minute). The method is unfavorable for the investment, energy consumption and production cost of the unit equipment, and the operation and maintenance requirements of the equipment are high.
Disclosure of Invention
The invention aims to provide 590 MPa-level high-formability hot dip galvanized dual phase steel and a rapid heat treatment galvanization manufacturing method, which control the recovery, recrystallization, austenite transformation and other processes of a deformed structure through rapid heat treatment, increase nucleation rate (comprising recrystallization nucleation rate and austenite transformation nucleation rate), shorten grain growth time, refine grains, obtain the dual phase steel with yield strength of 347-405 MPa, tensile strength of 624-709 MPa, elongation of 22.2-30.3%, strong plastic product of 15.7-19.6 GPa and strain hardening index n 90 A value greater than 0.21; good plasticity and toughness are obtained while the strength of the material is improved; meanwhile, the rapid heat treatment process improves the production efficiency, reduces the production cost and energy consumption, obviously reduces the number of furnace rollers and improves the surface quality of the steel plate.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
the 590 MPa-level high-formability hot dip galvanized dual phase steel comprises the following chemical components in percentage by mass: c: 0.045-0.105%, si:0.1 to 0.4 percent, mn:1.0 to 1.5 percent, P is less than or equal to 0.02 percent, S is less than or equal to 0.006 percent, al:0.02 to 0.055 percent, and can also contain one or two of Cr, mo, ti, nb, V, wherein Cr+Mo+Ti+Nb+V is less than or equal to 0.3 percent, and the balance is Fe and other unavoidable impurities, and the alloy is obtained by the following process:
1) Smelting and casting
Smelting and casting the steel into a slab according to the chemical components;
2) Hot rolling and coiling
The coiling temperature is 550-680 ℃;
3) Cold rolling
The cold rolling reduction rate is 40-85%;
4) Quick heat treatment and hot galvanizing
The cold rolled steel plate is quickly heated to 750-845 ℃, and the quick heating adopts one-section or two-section;
when the one-stage rapid heating is adopted, the heating rate is 50-500 ℃/s;
when two-section rapid heating is adopted, the first section is heated to 550-650 ℃ from room temperature at a heating rate of 15-500 ℃/s, and the second section is heated to 750-845 ℃ from 550-650 ℃ at a heating rate of 50-500 ℃/s; soaking, soaking temperature: soaking at 750-845 ℃ for a period of time: 10-60 s;
slowly cooling to 670-770 ℃ at a cooling rate of 5-15 ℃/s after soaking, then rapidly cooling to 460-470 ℃ at a cooling rate of 50-200 ℃/s, and immersing into a zinc pot for hot galvanizing;
after hot galvanizing, rapidly cooling to room temperature at a cooling rate of 30-150 ℃/s to obtain a hot-dip pure zinc GI product;
or after hot galvanizing, heating to 480-550 ℃ at a heating rate of 30-200 ℃/s for alloying treatment, wherein the alloying treatment time is 10-20 s; and after alloying treatment, rapidly cooling to room temperature at a cooling rate of 30-250 ℃/s to obtain an alloyed hot dip galvanizing GA product.
Preferably, the content of C is 0.065-0.085%.
Preferably, the Si content is 0.15 to 0.25%.
Preferably, the Mn content is 1.2% -1.35%.
Preferably, the hot dip galvanized dual phase steel contains one or two of Cr, mo, ti, nb, V, and Cr+Mo+Ti+Nb+V is less than or equal to 0.2%.
Preferably, the whole process of rapid heat treatment and hot galvanizing is carried out for 30-142 s.
Preferably, in step 2), the hot rolling temperature is not less than A r3 。
Preferably, in the step 2), the winding temperature is 580 to 650 ℃.
Preferably, in step 3), the cold rolling reduction is 60 to 80%.
Preferably, in the step 4), the heating rate is 50-300 ℃/s when the rapid heating is performed by adopting one-stage heating.
Preferably, in step 4), the rapid heating is performed by two-stage heating: the first section is heated from room temperature to 550-650 ℃ at a heating rate of 15-300 ℃/s; the second section is heated from 550 to 650 ℃ to 750 to 845 ℃ at a heating rate of 50 to 300 ℃/s.
Preferably, in step 4), the rapid heating is performed by two-stage heating: the first section is heated from room temperature to 550-650 ℃ at a heating rate of 30-300 ℃/s; the second section is heated from 550 to 650 ℃ to 750 to 845 ℃ at a heating rate of 80 to 300 ℃/s.
The metallographic structure of the hot dip galvanized dual phase steel is a ferrite and martensite dual phase structure which is uniformly distributed, and the average grain size is 1-3 mu m.
The yield strength of the hot dip galvanized dual phase steel is 347-405 MPa, the tensile strength is 624-709 MPa, the elongation is 22.2-30.3%, the plastic product is 15.7-19.6 GPa%, and the strain hardening index n 90 The value is greater than 0.21.
In the composition and process design of the steel of the invention:
c: carbon is the most common strengthening element in steel, and carbon increases the strength and decreases the plasticity of steel, but for steel for forming, low yield strength, high uniform elongation and total elongation are required, so that the carbon content is not excessively high. The carbon content has great influence on the mechanical properties of the steel, the quantity of pearlite is increased along with the increase of the carbon content, the strength and the hardness of the steel are greatly improved, but the plasticity and the toughness of the steel are obviously reduced, if the carbon content is too high, obvious netlike carbide appears in the steel, the existence of the netlike carbide obviously reduces the strength, the plasticity and the toughness of the steel, the strengthening effect generated by the increase of the carbon content in the steel is also obviously weakened, and the technological properties of the steel are deteriorated, so that the carbon content is reduced as much as possible on the premise of ensuring the strength.
For dual phase steels, the carbon element mainly affects the volume fraction of austenite formed during annealing, and during the formation of austenite, the diffusion process of the carbon element in the austenite or ferrite actually plays a role in controlling the growth of austenite grains. As the carbon content or the heating temperature of a critical region is increased, the volume fraction of austenite is increased, and then the martensite phase structure formed after cooling is increased, and the strength of the material is increased, so that the combination of the strength and toughness matching of the material and the improvement of the strength in the rapid annealing process are considered. The invention limits the carbon content to the range of 0.045-0.105%.
Mn: manganese can form solid solution with iron, so that the strength and hardness of ferrite and austenite in carbon steel are improved, finer pearlite with higher strength is obtained in the cooling process of steel after hot rolling, and the content of pearlite is increased along with the increase of the content of Mn. Manganese is also a carbide forming element, and the carbide of manganese can be dissolved into the cementite, thereby indirectly enhancing the strength of pearlite. Manganese can also strongly enhance the hardenability of the steel, further increasing its strength.
For dual phase steels, manganese is one of the elements that significantly affects the kinetics of austenite formation upon intercritical annealing, and manganese primarily affects the process of austenite to ferrite transformation and growth after austenite formation and the final equilibrium process of austenite and ferrite. Since the diffusion speed of manganese element in austenite is far smaller than that in ferrite, the growth time of austenite grains controlled by manganese diffusion is longer, and the time for manganese element to reach even distribution in austenite is longer. When heating in critical areas, if the heat preservation time is short, manganese elements cannot be uniformly distributed in austenite, and then the cooling rate is insufficient, a uniform martensitic island structure cannot be obtained. In dual-phase steel produced by a rapid heat treatment process (such as a water quenching continuous annealing production line), the manganese content is generally higher, so that the austenite has higher manganese content after being generated, Ensures the hardenability of the austenite island, and obtains uniform martensite island structure and uniform performance after cooling. In addition, manganese enlarges the gamma-phase region and reduces A c1 And A c3 Temperature, and therefore manganese-containing steels will give a higher martensitic volume fraction than low carbon steels under the same heat treatment conditions. However, when the manganese content is high, the crystal grains in the steel tend to coarsen, and the overheat sensitivity of the steel is increased; when cooling is improper after the smelting pouring and hot forging, white spots are easily generated in the carbon steel. In consideration of the above factors, the manganese content is designed to be within the range of 1.0-1.5%.
Si: silicon forms a solid solution in ferrite or austenite, thereby enhancing the yield strength and tensile strength of the steel, and silicon can increase the cold work deformation hardening rate of the steel, which is a beneficial element in alloy steel. In addition, silicon has obvious enrichment phenomenon on the surface of the crystal boundary of the silicon-manganese steel, and the segregation of silicon at the crystal boundary position can slow down the distribution of carbon and phosphorus along the crystal boundary, thereby improving the embrittlement state of the crystal boundary. Silicon can improve the strength, hardness and wear resistance of steel, and the plasticity of the steel is not obviously reduced. The silicon deoxidizer has strong capability, is a deoxidizer commonly used in steelmaking, and can increase the fluidity of molten steel, so that the common steel contains silicon, but when the silicon content in the steel is too high, the plasticity and toughness of the steel can be obviously reduced.
For dual phase steels, the main effect of silicon is to reduce the annealing time, affecting the austenite volume fraction at the final equilibrium. Silicon has no significant effect on the rate of austenite growth, but has significant effect on the morphology and distribution of austenite formation. Therefore, the silicon content is determined to be within the range of 0.1 to 0.4%.
Cr: chromium has the main function of improving hardenability in steel, so that the steel has better comprehensive mechanical property after quenching and tempering. Chromium forms a continuous solid solution with iron, reduces the austenite phase region, forms various carbides with carbon, and has a greater affinity with carbon than iron and manganese elements. Chromium and iron can form intermetallic compound sigma phase (FeCr), chromium reduces the concentration of carbon in pearlite and the limiting solubility of carbon in austenite; chromium slows down the decomposition speed of austenite and obviously improves the hardenability of steel. But also increases the temper embrittlement tendency of the steel. The chromium element can improve the strength and hardness of the steel, and can be used together with other alloy elements, so that the effect is obvious. Cr improves the quenching ability of steel in air cooling, and thus has an adverse effect on the welding performance of steel. However, at a chromium content of less than 0.3%, the adverse effect on weldability is negligible; when the content is more than this, defects such as cracks and slag inclusion are likely to occur during welding. When Cr is present with other alloying elements (e.g., coexisting with V), the adverse effect of Cr on weldability is greatly reduced. If elements such as Cr, mo, V and the like are simultaneously present in the steel, even if the Cr content reaches 1.7%, the welding performance of the steel is not significantly adversely affected. The chromium element is beneficial and unnecessary, and the addition amount is not excessive in consideration of factors such as cost increase and the like.
Mo: the molybdenum element can inhibit self-diffusion of iron and diffusion rate of other elements. Mo atoms have larger radius than alpha-Fe atoms, so that when Mo is dissolved in alpha solid solution, the solid solution is subjected to strong lattice distortion, and meanwhile, mo can increase the bond attraction of lattice atoms and improve the recrystallization temperature of alpha ferrite. Mo has remarkable strengthening effect in pearlite, ferrite and martensite steels, and even in high alloy austenitic steels. The good effect of Mo in steel is also dependent on the interactions with other alloying elements in the steel. When the strong carbide forming elements V, nb and Ti are added into the steel, the solid solution strengthening effect of Mo is more remarkable. This is because when a strong carbide-forming element is combined with C to form a stable carbide, mo is promoted to be more effectively dissolved into solid solution, thereby more contributing to the improvement of the heat resistance of steel. The addition of Mo also increases the hardenability of the steel, and Mo suppresses the transformation of the pearlite area and accelerates the transformation in the medium temperature area, so that Mo-containing steel forms a certain amount of bainite even at a high cooling rate and eliminates the formation of ferrite and pearlite, which is one of the reasons why Mo has a favorable effect on the heat resistance of low alloy heat resistant steel. Mo also significantly reduces the hot embrittlement tendency of the steel and reduces the pearlite spheroidization speed. When the Mo content is 0.15% or less, there is no adverse effect on the weldability of the steel. The molybdenum element is beneficial and unnecessary, and the addition amount is not excessive in consideration of factors such as cost increase and the like.
Microalloying elements Ti, nb, V: the addition of trace amounts of microalloy elements Nb, V and Ti in the steel can ensure that the steel has good weldability and other service performances under the condition of lower carbon equivalent by the dispersion and precipitation of carbon and nitride particles (the size is smaller than 5 nm) and the solid solution of Nb, V and Ti, thereby refining grains, greatly improving the strength and toughness of the steel, particularly the low-temperature toughness. Nb, V, ti are carbide-and nitride-forming elements that meet this requirement at relatively low concentrations, and are strong carbide-forming elements that exist in the steel in the form of carbide, nitride, carbonitride in a majority and are solid-solved in a minority in ferrite at ordinary temperatures. The addition of Nb, V and Ti can prevent austenite grains from growing up and increase the coarsening temperature of steel grains. This is because small particles of carbon and nitride dispersed in them can fix austenite grain boundaries, block the migration of austenite grain boundaries, raise austenite recrystallization temperature, and enlarge unrecrystallized regions, i.e., prevent austenite grains from growing. On one hand, the strength and the welding performance of the steel can be improved while the carbon equivalent content is reduced by adding a trace amount of Nb, V and Ti into the steel; on the other hand, impurities such as oxygen, nitrogen, sulfur, etc. are fixed, thereby improving the weldability of the steel; due to the action of microscopic particles, such as the undissolved property of TiN at high temperature, the coarsening of grains in a heat affected zone can be prevented, and the toughness of the heat affected zone can be improved, so that the welding performance of steel can be improved. The microalloy elements are beneficial and unnecessary, and the addition amount is not excessive due to factors such as cost increase and the like.
The invention controls the processes of recovery, recrystallization, austenite phase transformation, grain growth and the like of the deformed structure in the continuous heat treatment process through the rapid heat treatment process of rapid heating, short-time heat preservation and rapid cooling, not only forms ferrite matrix phase in the cooling process, but also generates various strengthening phases and component gradient distribution in the phases, and finally obtains fine ferrite structure and multi-form strengthening phase structure, so that the material obtains better toughness matching, reduces the alloy cost and manufacturing difficulty of each process, and improves the service performance such as the welding performance of steel grade with the same strength level.
The concrete principle is as follows: different heating rates are adopted at different temperature stages in the heating process, recovery of deformed tissues mainly occurs at a low-temperature stage, and relatively low heating rate can be adopted to reduce energy consumption; the high temperature section mainly generates recrystallization and grain growth of different phase structures, and the residence time of the material in the high temperature section is shortened by adopting relatively high heating rate and short soaking time so as to ensure that the grain growth is smaller or cannot grow. The recovery of the deformed structure and the ferrite recrystallization process in the heating process are restrained by controlling the heating rate in the heating process, so that the recrystallization process is overlapped with the austenite transformation process, nucleation points of recrystallized grains and austenite grains are increased, and the grains are refined finally. The time for grain growth in the soaking process is shortened by short-time heat preservation and rapid cooling, and fine and uniform grain structure distribution is ensured.
The invention relates to a rapid heat treatment galvanization manufacturing method of 590 MPa-level low-carbon low-alloy high-formability hot dip galvanized dual phase steel, which comprises the following steps:
1) Smelting and casting
Smelting and casting the steel into a slab according to the chemical components;
2) Hot rolling and coiling
The coiling temperature is 550-680 ℃;
3) Cold rolling
The cold rolling reduction rate is 40-85%, and the rolled hard strip steel or steel plate is obtained after cold rolling;
4) Quick heat treatment and hot galvanizing
a) Rapid heating
Rapidly heating cold-rolled strip steel or a steel plate from room temperature to a target temperature of an austenite and ferrite two-phase region at 750-845 ℃, wherein the rapid heating adopts a one-section type or a two-section type;
when the one-stage rapid heating is adopted, the heating rate is 50-500 ℃/s;
when two-section rapid heating is adopted, the first section is heated to 550-650 ℃ from room temperature at a heating rate of 15-500 ℃/s, and the second section is heated to 750-845 ℃ from 550-650 ℃ at a heating rate of 50-500 ℃/s;
b) Soaking heat
Soaking at the target temperature of 750-845 ℃ in the austenite and ferrite two-phase region for 10-60 s;
c) Cooling and hot galvanizing
Slowly cooling the steel strip or the steel plate to 670-770 ℃ at a cooling rate of 5-15 ℃/s after soaking; then cooling to 460-470 ℃ at a cooling rate of 50-150 ℃/s, immersing the strip steel or the steel plate into a zinc pot for hot galvanizing;
d) After hot galvanizing the strip steel or the steel plate, rapidly cooling to room temperature at a cooling rate of 50-150 ℃/s to obtain a hot-dip pure zinc GI product;
or alternatively, the process may be performed,
after hot galvanizing the strip steel or the steel plate, heating to 480-550 ℃ at a heating rate of 30-200 ℃/s for alloying treatment, wherein the alloying treatment time is 10-20 s; and after alloying treatment, rapidly cooling to room temperature at a cooling rate of 30-250 ℃/s to obtain an alloyed hot dip galvanizing GA product.
Preferably, the whole process of rapid heat treatment and hot galvanizing is carried out for 30-142 s.
Preferably, in step 2), the hot rolling temperature is not less than A r3 。
Preferably, in the step 2), the winding temperature is 580 to 650 ℃.
Preferably, in step 3), the cold rolling reduction is 60 to 80%.
Preferably, in the step 4), the heating rate is 50-300 ℃/s when the rapid heating is performed by adopting one-stage heating.
Preferably, in the step 4), the rapid heating adopts two-stage heating, wherein the first stage is heated from room temperature to 550-650 ℃ at a heating rate of 15-300 ℃/s, and the second stage is heated from 550-650 ℃ to 750-845 ℃ at a heating rate of 50-300 ℃/s.
Preferably, in the step 4), the rapid heating adopts two-stage heating, wherein the first stage is heated from room temperature to 550-650 ℃ at a heating rate of 30-300 ℃/s, and the second stage is heated from 550-650 ℃ to 750-845 ℃ at a heating rate of 80-300 ℃/s.
Preferably, in step 4), the rapid heating final temperature is 770 to 830 ℃.
Preferably, in the soaking process of step 4), after the steel strip or the steel plate is heated to the target temperature of the austenite and ferrite two-phase region, the soaking is performed while keeping the temperature unchanged.
Preferably, in the soaking process of the step 4), the strip steel or the steel plate is subjected to small-amplitude heating or small-amplitude cooling in the soaking time period, the temperature after heating is not more than 845 ℃, and the temperature after cooling is not less than 750 ℃.
Preferably, the soaking time is 10 to 40 seconds.
Preferably, in the step 4), after the strip steel or the steel plate is alloyed, the strip steel or the steel plate is rapidly cooled to room temperature at a cooling rate of 30-200 ℃/s, and an alloyed hot dip galvanizing GA product is obtained.
The rapid heat treatment hot dip galvanizing manufacturing method of 590MPa grade low-carbon low-alloy high-formability hot dip galvanized dual phase steel comprises the following steps:
1. heating rate control
The recrystallization kinetics of a continuous heating process can be quantitatively described by a relationship affected by the heating rate, where the ferrite recrystallization volume fraction as a function of temperature T:
wherein X (t) is ferrite recrystallization volume fraction; n is Avrami index, is related to a phase change mechanism, and generally takes a value in a range of 1-4 depending on the decay period of the recrystallization nucleation rate; t is the heat treatment temperature; t (T) star Is the recrystallization onset temperature; beta is the heating rate; b (T) is obtained by the formula:
b＝b 0 exp(-Q/RT)
from the above formula and the related experimental data, it can be seen that the recrystallization onset temperature (T star ) End temperature (T) fin ) Are all raised; when the heating rate is above 50 ℃/s, the austenite transformation and recrystallization processes are overlapped, the recrystallization temperature is increased to the temperature of the two-phase region, and the faster the heating rate is, the higher the ferrite recrystallization temperature is.
Under the traditional slow heating condition, the deformed matrix is sequentially recovered, recrystallized and grown up, ferrite is transformed into austenite after the deformed matrix is subjected to phase transformation, phase transformation nucleation points are mainly concentrated at the grown up ferrite grain boundaries, the nucleation rate is low, and finally the obtained grain structure is coarse.
Under the condition of rapid heating, the deformed matrix starts to generate ferrite-to-austenite phase transformation without finishing recovery, or the austenite phase transformation is generated without growing crystal grains immediately after recrystallization, and the nucleation rate is obviously improved and the austenite crystal grains are obviously refined due to the fine crystal grains and large grain boundary area when the recrystallization is immediately finished. Particularly, after ferrite recrystallization and austenite transformation process are overlapped, a large number of crystal defects such as dislocation and the like are reserved in ferrite crystals, a large number of nucleation points are provided for austenite, so that the austenite presents explosive nucleation, and austenite grains are further refined. Meanwhile, the retained high-density dislocation line defects also become channels for high-speed diffusion of carbon atoms, so that each austenite grain can be quickly generated and grown, and the volume fraction of austenite is increased.
The structure evolution, alloy element and each phase component distribution are finely controlled in the rapid heating process, so that a good foundation is laid for the austenite structure growth in the subsequent soaking process, the distribution of each alloy component and the transformation from austenite to martensite phase in the rapid cooling process. The final product structure with refined grains, reasonable elements and distribution of each phase can be finally obtained. The invention sets the heating rate of one-section type rapid heating to 50-500 ℃/s and adopts two-section type rapid heating to 15-500 ℃/s by comprehensively considering the effects of rapid heating and refining crystal grains, manufacturing cost, manufacturability and other factors.
Because the influence of rapid heating on the material recovery, recrystallization, grain growth and other tissue evolution processes is different in different temperature ranges, the optimal tissue control is obtained, so that the optimal heating rate is also different in different heating temperature ranges: the influence of the heating rate on the recovery process is maximum from 20 ℃ to 550-650 ℃, and the heating rate is controlled to be 15-300 ℃/s, and more preferably 30-300 ℃/s; the heating temperature is from 550 to 650 ℃ to 750 to 845 ℃ of austenitizing temperature, the heating rate has the greatest influence on the growth process of the crystal grains, and the heating rate is controlled to be 50 to 300 ℃/s; further preferably 80 to 300 ℃/s.
2. Soaking temperature control
The soaking temperature is selected by combining the material tissue evolution process control of each temperature stage in the heating process, and simultaneously considering the tissue evolution and control of the subsequent rapid cooling process, so that the optimal tissue structure and distribution can be finally obtained.
The soaking temperature generally depends on the C content, which is 0.045-0.105% in the dual phase steel of the present invention, A in the steel of the present invention C1 And A C3 At about 730 ℃ and 870 ℃, respectively. The rapid heat treatment process heats the strip steel to A C1 To A C3 Soaking is carried out in between, a large amount of dislocation is reserved in ferrite which is not fully recrystallized by utilizing a rapid heating technology, and a larger nucleation driving force is provided for austenite transformation, so that more and finer austenite tissues can be obtained by the rapid heat treatment method compared with the traditional continuous annealing process.
The invention firstly proposes that the soaking temperature is increased and reduced within a certain range for the control of the soaking temperature: i.e., the soaking zone Wen Qingxie rises and falls obliquely, the soaking temperature must be kept within a certain range. The advantage of this is that: the rapid temperature rise and fall process in the temperature range of the two-phase region actually further increases the superheat degree and the supercooling degree, is convenient for the rapid phase transformation process, and can further refine grains through repeated ferrite-to-austenite phase transformation and austenite-to-ferrite phase transformation when the temperature rise and fall range is large enough and the temperature rise and fall rate is also large enough, and meanwhile has a certain influence on carbide formation and even distribution of alloy elements, and finally forms finer tissues and alloy elements with even distribution.
The cold-rolled dual-phase steel has a large amount of undissolved tiny evenly-distributed carbide, can play a role in mechanically obstructing the growth of austenite grains in the heating process, and is beneficial to refining the grain size of the high-strength steel. However, if the soaking temperature is too high, the number of undissolved carbides is greatly reduced, the impeding effect is weakened, the growth tendency of grains is enhanced, and the strength of the steel is further reduced. When the amount of undissolved carbide is too large, aggregation may be caused, resulting in uneven distribution of local chemical components, and when the carbon content at the aggregation site is too high, local overheating may be caused. Therefore, in ideal conditions, a small amount of fine granular undissolved carbide should be uniformly distributed in the steel, so that abnormal growth of austenite grains can be prevented, the content of each alloy element in the matrix can be correspondingly increased, and the aim of improving the mechanical properties of the alloy steel such as strength, toughness and the like is fulfilled.
The soaking temperature should also be selected to obtain fine and uniform austenite grains, and to avoid coarse austenite grains, so as to achieve the purpose of obtaining a fine martensitic structure after cooling. Too high soaking temperature can cause austenite grains to be coarse, and a martensitic structure obtained after quick cooling can be coarse, so that the mechanical property of the steel is poor; the amount of retained austenite is increased, the amount of martensite is reduced, and the hardness and wear resistance of the steel are reduced. The excessively low soaking temperature not only reduces the quantity of austenite, but also causes insufficient content of alloy elements in the austenite, causes uneven concentration distribution of the alloy elements in the austenite, greatly reduces the hardenability of the steel, and has adverse effects on the mechanical properties of the steel. Soaking temperature of hypoeutectoid steel should be Ac 3 +30 to 50 ℃. In the case of ultra-high strength steel, the presence of carbide forming elements affects the transformation of carbides, so that the soaking temperature can be suitably increased. By combining the factors, 770-845 ℃ is selected as soaking temperature, so that more ideal and reasonable final organization is obtained.
3. Soaking time control
The influence factor of soaking time also depends on the content of carbon and alloy elements in steel, when the content of carbon and alloy elements in steel is increased, not only the thermal conductivity of steel is reduced, but also the alloy elements obviously delay the structural transformation of steel because the diffusion speed of the alloy elements is slower than that of the carbon elements, and the heat preservation time is properly prolonged. Because the invention adopts rapid heating, and the material contains a large amount of dislocation at the temperature of the two-phase region, a large amount of nucleation sites are provided for the formation of austenite, and a rapid diffusion channel is provided for carbon atoms, the austenite can be formed extremely rapidly; the shorter the soaking and heat preserving time is, the shorter the diffusion distance of carbon atoms is, the larger the carbon concentration gradient in the austenite is, and finally, the more the carbon content of the retained austenite is; however, if the heat preservation time is too short, the alloy elements in the steel are unevenly distributed, so that austenitization is insufficient; the austenite grains are easily coarse due to the long heat preservation time. In conclusion, the soaking and heat preserving time is set to be 10-60 s.
4. Fast cooling rate control
The rapid cooling process is controlled by combining comprehensive factors such as the evolution result of each structure, the diffusion distribution result of alloy and the like in the early heating and soaking processes, so that the ideal material structure with reasonable distribution of each phase structure and elements is finally obtained.
In order to obtain a martensite reinforced phase, the cooling speed of the material during rapid cooling is required to be larger than the critical cooling speed to obtain a martensite structure, and the critical cooling speed mainly depends on the material composition, and the content of Si is 0.1-0.4%, the content of Mn is 1.0-1.5% and the content is relatively high, so that the hardenability of the dual-phase steel is enhanced to a great extent by Si and Mn, and the critical cooling speed is reduced.
The cooling rate also needs to comprehensively consider the structure evolution and alloy diffusion distribution results of the heating process and the soaking process so as to finally obtain reasonable structure distribution of each phase and alloy element distribution. The cooling rate is too low to obtain a martensitic structure, so that the strength is reduced, and the mechanical properties cannot meet the requirements; and a too large cooling rate can generate larger quenching stress (namely tissue stress and thermal stress) to cause serious plate shape defects, especially serious plate shape defects when the cooling is uneven, and even serious deformation and cracking of the sample are easily caused. The present invention sets the rapid cooling rate to 50-150 deg.c/s.
5. Hot galvanizing and alloying control
According to the invention, the traditional continuous annealing hot dip galvanizing unit is subjected to rapid heating and rapid cooling process transformation, so that the rapid heat treatment hot dip galvanizing process is realized, the length of the heating and soaking section of the annealing furnace can be greatly shortened (at least one third shorter than that of the traditional continuous annealing furnace), the production efficiency of the traditional continuous annealing hot dip galvanizing unit is improved, the production cost and energy consumption are reduced, the number of furnace rollers of the continuous annealing hot dip galvanizing furnace, particularly the number of furnace rollers of the high-temperature furnace section are obviously reduced, the surface quality control capability of strip steel is improved, and the strip steel product with high surface quality is obtained.
For high-strength hot dip galvanized products, the rapid heat treatment process reduces the residence time of the strip steel in a high-temperature furnace, so that the enrichment of alloy elements on the surface of the high-strength strip steel in the heat treatment process is obviously reduced, the platability of the high-strength hot dip galvanized products is improved, the surface plating omission defect is reduced, the corrosion resistance is improved, and the yield is improved. In addition, due to the refinement of product grains and the reduction of the alloy content of the material, the reaming performance, bending performance and other processing forming performance, welding performance and other user use performance of the dual-phase steel product obtained by adopting the technology are also improved.
Meanwhile, the purposes of short and precise unit, flexible material transition, strong regulation and control capability and the like can be realized by establishing a novel continuous annealing hot galvanizing unit of a rapid heat treatment hot galvanizing process technology; the product material can refine the grain of the strip steel, further improve the material strength, reduce the alloy cost and the manufacturing difficulty of the working procedure before hot galvanizing, and improve the use performance of users such as material molding, welding and the like.
Compared with the traditional heat treatment technology, the invention has the advantages that:
(1) According to the invention, the recovery of a deformation structure and a ferrite recrystallization process in the heat treatment process are restrained through rapid heat treatment, so that the recrystallization process is overlapped with an austenite transformation process, nucleation points of recrystallized grains and austenite grains are increased, the grain growth time is shortened, the obtained metallographic structure of the dual-phase steel is a ferrite and martensite dual-phase structure which is uniformly distributed, and the average grain size is 1-3 mu m, so that the dual-phase steel product can obtain good strong plastic matching.
(2) Compared with the hot dip galvanized dual phase steel obtained by the traditional continuous annealing hot dip galvanizing method, the method provided by the invention is fast under the premise of unchanged manufacturing conditions in the previous working procedureThe average grain size of the dual-phase steel obtained after the rapid heat treatment is 1-3 mu m, and a good fine grain strengthening effect can be obtained. The yield strength is 347-405 MPa, the tensile strength is 624-709 MPa, the elongation is 22.2-30.3%, the product of strength and elongation is 15.7-19.6 GPa, and the strain hardening index n 90 The value is greater than 0.21.
(3) According to the rapid heat treatment process for the low-carbon low-alloy high-formability 590 MPa-level hot dip galvanized dual-phase steel, the time for the whole heat treatment process can be shortened to 30-142 s, the time of the whole heat treatment process (the time of the traditional continuous annealing process is usually 5-8 min) is greatly reduced, the production efficiency is remarkably improved, the energy consumption is reduced, and the production cost is reduced.
(4) Compared with the traditional dual-phase steel and the heat treatment process thereof, the rapid heat treatment method shortens the length and time of the heating section and the soaking section of the continuous hot dip galvanizing annealing furnace (compared with the traditional continuous hot dip galvanizing annealing furnace, the length of the heating section and the soaking section can be shortened by 60-80 percent) and the whole heat treatment process time, can save energy, reduce emission and consumption, obviously reduce the one-time investment of furnace equipment and obviously reduce the production running cost and the equipment maintenance cost; the product with the same strength grade is produced, the alloy content in the product produced by the process is lower, the production cost of heat treatment and previous working procedures can be reduced, and the manufacturing difficulty of each working procedure before heat treatment is reduced.
(5) Compared with the dual-phase steel obtained by the traditional continuous annealing treatment, the rapid heat treatment process technology is adopted, so that the heating process and soaking process time can be reduced, the furnace length is shortened, the number of furnace rollers is obviously reduced, the probability of generating surface defects in the furnace of the strip steel is reduced, and the surface quality of the product is obviously improved.
The low-carbon low-alloy high-formability 590 MPa-level hot dip galvanized dual phase steel obtained by the method has important value for the development of new-generation light-weight vehicles such as automobiles, trains, ships, airplanes and the like, and the healthy development of corresponding industries and advanced manufacturing industries.
Drawings
FIG. 1 is a photograph of the microstructure of hot-dip galvanized dual phase steel (GI) produced as in example 1 for test steel A according to the invention.
FIG. 2 is a photograph of the microstructure of hot-dip pure zinc dual phase steel (GI) produced at the heating rate of the conventional process 1 for the test steel A according to the present invention.
FIG. 3 is a photograph of the microstructure of galvannealed dual phase steel (GA) produced in example 17 for test steel I according to the present invention.
FIG. 4 is a photograph of the microstructure of hot-dip galvanized dual phase steel (GI) as produced in example 22 for test steel D according to the invention.
FIG. 5 is a photograph of the microstructure of galvannealed dual phase steel (GA) produced in example 34 for test steel I according to the present invention.
Detailed Description
The present invention is further described below with reference to examples and drawings, and the examples are provided on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are given, but the scope of protection of the present invention is not limited to the examples described below.
The composition of the test steel according to the invention is shown in Table 1, the specific parameters of the examples according to the invention and of the conventional process are shown in Table 2 (one-stage heating) and Table 3 (two-stage heating); tables 4 and 5 show the main properties of the GI and GA hot dip galvanized dual phase steels prepared according to the examples and conventional techniques of tables 2 and 3, which are the components of the test steels according to the present invention.
As can be seen from tables 1 to 5, the alloy content in the same grade steel can be reduced by the method of the present invention, and the matching of the material structure and the strength and toughness can be obtained. The yield strength of the dual-phase steel obtained by the method is 347-405 MPa, the tensile strength is 624-709 MPa, the elongation is 22.2-30.3%, the strength-plastic product is 15.7-19.6 GPa%, and the strain hardening index n 90 The value is greater than 0.21.
Fig. 1 and 2 are structural diagrams of typical composition a steel through example 1 and comparative conventional process example 1. From the two figures, there is a very large difference in the tissue after hot dip galvanization. The structure (figure 1) of the steel A after the rapid heat treatment of the invention is composed of fine and uniform martensitic structure and carbide dispersed on a fine ferrite matrix. Tissue treated by the process of the invention: ferrite, martensite grain structure and carbide are all very fine and uniformly dispersed, which is very advantageous for improving the strength and plasticity of the material. Whereas the a steel structure (fig. 2) treated by the conventional process is a typical dual phase steel structure diagram. That is, a small amount of black martensite structure exists on the grain boundaries of the large white ferrite structure. The tissue treated by the traditional heat treatment process is characterized in that: the grains are coarse, martensite and carbide are distributed in a net shape along the ferrite grain boundary, and the content of martensite is not high.
Fig. 3 is a structure diagram of a typical composition I steel obtained through example 17 (GA), and fig. 4 is a structure diagram of a typical composition D steel obtained through example 22 (GI). FIG. 5 is a structure chart obtained by passing a typical composition I steel through example 34 (GA). Examples 17, 22, 34 are all short-term processes for the entire heat treatment cycle. As can be seen from the figure, the rapid thermal treatment hot galvanizing method of the invention can obtain very uniform, fine and dispersed phase structures (figures 3 and 5) after alloying treatment. The preparation method of the hot dip galvanized dual phase steel can refine grains, so that each phase structure of the material is uniformly distributed in a matrix, thereby improving the material structure and the material performance.
According to the invention, the traditional continuous annealing hot dip galvanizing unit is subjected to process transformation by adopting a rapid heating and rapid cooling process, so that the rapid heat treatment hot dip galvanizing process is realized, the lengths of a heating section and a soaking section of the traditional continuous annealing hot dip galvanizing furnace can be greatly shortened, the production efficiency of the traditional continuous annealing hot dip galvanizing unit is improved, the production cost and the energy consumption are reduced, the number of furnace rollers of the continuous annealing hot dip galvanizing furnace is reduced, the surface quality control capability of strip steel is improved, and a strip steel product with high surface quality is obtained; meanwhile, the purposes of short and precise unit, flexible product specification and variety transition, strong regulation and control capability and the like can be realized by establishing a novel continuous annealing hot galvanizing unit adopting a rapid heat treatment hot galvanizing process technology; the material can refine the grain of the strip steel, further improve the strength of the material, reduce the alloy cost and the manufacturing difficulty of the working procedure before heat treatment, and improve the use performance of users such as forming, welding and the like of the material.
In summary, the rapid heat treatment hot galvanizing process is adopted to greatly promote the technical progress of the continuous annealing hot galvanizing process of the cold-rolled strip steel, the cold-rolled strip steel is expected to finish the austenitizing process from room temperature to finish in tens of seconds or even a few seconds, the length of a heating section of a continuous annealing hot galvanizing furnace is greatly shortened, the speed and the production efficiency of a continuous annealing hot galvanizing unit are conveniently improved, the number of rollers in the furnace of the continuous annealing hot galvanizing unit is obviously reduced, the number of rollers in a high-temperature furnace section of the rapid heat treatment hot galvanizing production line with the unit speed of about 180 meters/minute is not more than 10, and the surface quality of the strip steel can be obviously improved. Meanwhile, the rapid heat treatment hot galvanizing process method of the recrystallization and austenitizing process completed in a very short time also provides a more flexible and flexible high-strength steel structure design method, so that the material structure is improved and the material performance is improved on the premise of not changing the alloy components, the rolling process and other pre-process conditions.
The advanced high-strength steel represented by the dual-phase steel has wide application prospect, and the rapid heat treatment hot galvanizing technology has huge development value, and the combination of the two can provide a larger space for the development and production of the hot galvanizing dual-phase steel.
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Claims (22)

  1. The high-formability hot dip galvanized dual phase steel at the level of 1.590MPa comprises the following chemical components in percentage by mass: c: 0.045-0.105%, si:0.1 to 0.4%, mn: 1.0-1.5%, P is less than or equal to 0.02%, S is less than or equal to 0.006%, al: 0.02-0.055%, one or two of Cr, mo, ti, nb, V, cr+Mo+Ti+Nb+V less than or equal to 0.3%, and the balance Fe and other unavoidable impurities, wherein the metallographic structure of the hot dip galvanized dual phase steel is a uniformly distributed ferrite and martensite dual phase structure, and the average grain size is 1-3 mu m; and is obtained by the following process:
    1) Smelting and casting
    Smelting and casting the steel into a slab according to the chemical components;
    2) Hot rolling and coiling
    The coiling temperature is 550-680 ℃;
    3) Cold rolling
    The cold rolling reduction rate is 40-85%;
    4) Quick heat treatment and hot galvanizing
    The steel plate after cold rolling is rapidly heated to 750-845 ℃, the rapid heating is performed in two sections, the first section is heated to 550-650 ℃ from room temperature at a heating rate of 15-500 ℃/s, and the second section is heated to 750-845 ℃ from 550-650 ℃ at a heating rate of 50-500 ℃/s; soaking, soaking temperature: soaking at 750-845 ℃ for a period of time: 10-60 s;
    slowly cooling to 670-770 ℃ at a cooling rate of 5-15 ℃/s after soaking, then rapidly cooling to 460-470 ℃ at a cooling rate of 50-200 ℃/s, and immersing into a zinc pot for hot galvanizing;
    After hot galvanizing, rapidly cooling to room temperature at a cooling rate of 30-150 ℃/s to obtain a hot-dip pure zinc GI product;
    or after hot galvanizing, heating to 480-550 ℃ at a heating rate of 30-200 ℃/s for alloying treatment, wherein the alloying treatment time is 10-20 s; after alloying treatment, rapidly cooling to room temperature at a cooling rate of 30-250 ℃/s to obtain an alloyed hot dip galvanizing GA product;
    the time for the whole process of rapid heat treatment and hot galvanizing is 30-142 s.
  2. 2. The 590 MPa-level high-formability hot-dip galvanized dual phase steel according to claim 1, wherein the C content is 0.065 to 0.085%.
  3. 3. The 590 MPa-level high-formability hot-dip galvanized dual phase steel according to claim 1, wherein the Si content is 0.15 to 0.25%.
  4. 4. The 590 MPa-level high-formability hot-dip galvanized dual phase steel according to claim 1, wherein the Mn content is 1.2 to 1.35%.
  5. 5. The 590 MPa-level high-formability hot-dip galvanized dual phase steel according to claim 1, wherein one or two of Cr, mo, ti, nb, V are contained in the components of the hot-dip galvanized dual phase steel, and cr+mo+ti+nb+v is less than or equal to 0.2%.
  6. 6. The 590 MPa-grade high formability hot dip galvanized dual phase steel according to claim 1, wherein in step 2), the hot rolling temperature is equal to or higher than a r3 。
  7. 7. The 590 MPa-level high formability hot dip galvanized dual phase steel according to claim 1, wherein in the step 2), the coiling temperature is 580 to 650 ℃.
  8. 8. The 590 MPa-level high-formability hot-dip galvanized dual phase steel according to claim 1, wherein in the step 3), the cold rolling reduction is 60 to 80%.
  9. 9. The 590 MPa-grade high formability hot dip galvanized dual phase steel according to claim 1, wherein in step 4), the rapid heating is two-stage heating: the first section is heated to 550-650 ℃ from room temperature at a heating rate of 15-300 ℃/s; the second section is heated from 550 ℃ to 650 ℃ to 750 ℃ to 845 ℃ at a heating rate of 50 ℃ to 300 ℃/s.
  10. 10. The 590 MPa-grade high formability hot dip galvanized dual phase steel according to claim 1, wherein in step 4), the rapid heating is two-stage heating: the first section is heated to 550-650 ℃ from room temperature at a heating rate of 30-300 ℃/s; the second section is heated from 550 ℃ to 650 ℃ to 750 ℃ to 845 ℃ at a heating rate of 80 ℃ to 300 ℃/s.
  11. 11. The 590 MPa-level high-formability hot-dip galvanized dual phase steel according to any one of claims 1 to 10, characterized in that the yield strength of the hot-dip galvanized dual phase steel is 347 to 405MPa, the tensile strength is 624 to 709MPa, the elongation is 25.8 to 30.3%, the yield strength is 16.9764 to 19.6gpa%, the strain hardening index n 90 The value is greater than 0.21.
  12. 12. The rapid thermal processing and hot dip galvanizing manufacturing method for 590 MPa-level high formability hot dip galvanized dual phase steel according to any one of claims 1 to 11, characterized by comprising the steps of:
    1) Smelting and casting
    Smelting and casting into a plate blank according to the chemical components;
    2) Hot rolling and coiling
    The coiling temperature is 550-680 ℃;
    3) Cold rolling
    The cold rolling reduction rate is 40-85%, and the rolled hard strip steel or steel plate is obtained after cold rolling;
    4) Quick heat treatment and hot galvanizing
    a) Rapid heating
    Rapidly heating cold-rolled strip steel or a steel plate from room temperature to target temperature of an austenite and ferrite two-phase region of 750-845 ℃, wherein the rapid heating adopts two sections, the first section is heated to 550-650 ℃ from room temperature at a heating rate of 15-500 ℃/s, and the second section is heated to 750-845 ℃ from 550-650 ℃ at a heating rate of 50-500 ℃/s;
    b) Soaking heat
    Soaking at the target temperature of 750-845 ℃ in the austenite and ferrite two-phase region for 10-60 s;
    c) Cooling and hot galvanizing
    Slowly cooling the steel strip or the steel plate to 670-770 ℃ at a cooling rate of 5-15 ℃/s after soaking; then rapidly cooling to 460-470 ℃ at a cooling rate of 50-150 ℃/s, and immersing the strip steel or the steel plate into a zinc pot for hot galvanizing;
    d) Cooling the strip steel or the steel plate to room temperature at a cooling rate of 30-150 ℃/s after hot galvanizing, and obtaining a hot-dip pure zinc GI product;
    Or alternatively, the process may be performed,
    after hot galvanizing the strip steel or the steel plate, heating to 480-550 ℃ at a heating rate of 30-200 ℃/s for alloying treatment, wherein the alloying treatment time is 10-20 s; after alloying treatment, rapidly cooling to room temperature at a cooling rate of 30-250 ℃/s to obtain an alloyed hot dip galvanizing GA product;
    the time for the whole process of rapid heat treatment and hot galvanizing is 30-142 s.
  13. 13. The method for producing 590 MPa-grade high-formability hot-dip galvanized dual phase steel according to claim 12, wherein in step 2), the hot rolling temperature is equal to or higher than a r3 。
  14. 14. The method for manufacturing a 590 MPa-level high-formability hot-dip galvanized dual phase steel according to claim 12 or 13, characterized in that in the step 2), the coiling temperature is 580 to 650 ℃.
  15. 15. The method for producing a hot dip galvanized dual phase steel with 590MPa level and high formability according to claim 12, characterized in that in step 3), the cold rolling reduction is 60 to 80%.
  16. 16. The rapid thermal processing hot dip galvanizing manufacturing method for 590 MPa-level high formability hot dip galvanized dual phase steel according to claim 12, characterized in that in step 4), the rapid heating adopts two-stage heating, the first stage is heated from room temperature to 550 to 650 ℃ at a heating rate of 15 to 300 ℃/s, and the second stage is heated from 550 to 650 ℃ to 750 to 845 ℃ at a heating rate of 50 to 300 ℃/s.
  17. 17. The rapid thermal processing hot dip galvanizing manufacturing method for 590 MPa-level high formability hot dip galvanized dual phase steel according to claim 12, characterized in that in step 4), the rapid heating adopts two-stage heating, the first stage is heated from room temperature to 550 to 650 ℃ at a heating rate of 30 to 300 ℃/s, and the second stage is heated from 550 to 650 ℃ to 750 to 845 ℃ at a heating rate of 80 to 300 ℃/s.
  18. 18. The method for manufacturing 590 MPa-level low-carbon low-alloy high-formability hot-dip galvanized dual-phase steel according to claim 12, wherein in the step 4), the final rapid heating temperature is 770-830 ℃.
  19. 19. The method for rapid heat treatment hot dip galvanizing of 590 MPa-level low carbon low alloy high formability hot dip galvanized dual phase steel according to claim 12, wherein in the soaking process of step 4), the steel strip or sheet is heated to the target temperature of the austenite and ferrite two phase region, and then the soaking is performed while maintaining the temperature unchanged.
  20. 20. The rapid heat treatment hot galvanizing manufacturing method of 590 MPa-level low-carbon low-alloy high-formability hot galvanizing dual-phase steel according to claim 12, wherein in the soaking process of step 4), the temperature of the strip steel or the steel plate is raised or lowered to a small extent in the soaking time period, the temperature after the temperature is raised is no more than 845 ℃, and the temperature after the temperature is lowered is no less than 750 ℃.
  21. 21. The method for manufacturing 590 MPa-level low-carbon low-alloy high-formability hot-dip galvanized dual-phase steel according to claim 12, 19 or 20, wherein the soaking time is 10 to 40s.
  22. 22. The method for manufacturing 590 MPa-level low-carbon low-alloy high-formability hot-dip galvanized dual-phase steel according to claim 12, characterized in that in step 4), after the alloying treatment of the steel strip or the steel plate, the steel strip or the steel plate is rapidly cooled to room temperature at a cooling rate of 30-200 ℃/s, and an alloyed hot-dip galvanized GA product is obtained.
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