CN115537661B - 600 MPa-level hot dip galvanized dual-phase steel for automobile structure and production method thereof - Google Patents

600 MPa-level hot dip galvanized dual-phase steel for automobile structure and production method thereof Download PDF

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CN115537661B
CN115537661B CN202211222061.3A CN202211222061A CN115537661B CN 115537661 B CN115537661 B CN 115537661B CN 202211222061 A CN202211222061 A CN 202211222061A CN 115537661 B CN115537661 B CN 115537661B
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rolling
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cooling
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CN115537661A (en
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李鹏
王少炳
杨雄
惠鑫
卢晓禹
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Baotou Iron and Steel Group Co Ltd
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Baotou Iron and Steel Group Co Ltd
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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
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

The invention discloses 600 MPa-level hot dip galvanized dual-phase steel for an automobile structure and a production method thereof, wherein the 600 MPa-level hot dip galvanized dual-phase steel for the automobile structure comprises the following chemical components in percentage by mass: c:0.10 to 0.12 percent, si:0.28 to 0.35 percent, mn:1.50 to 1.65 percent, P: less than or equal to 0.020%, S: less than or equal to 0.003 percent, alt:0.020 to 0.050 percent, cr:0.30 to 0.40 percent, ca:0.0008 to 0.0020 percent, and the balance of Fe and unavoidable impurities. The 600 MPa-level hot dip galvanized dual phase steel for the automobile structure provided by the invention has the comprehensive properties of continuous yield, high strength, low yield ratio, high work hardening rate, good uniform deformation, excellent bake hardening capacity, corrosion resistance and the like.

Description

600 MPa-level hot dip galvanized dual-phase steel for automobile structure and production method thereof
Technical Field
The invention belongs to the technical field of metallurgical plate production, and particularly relates to 600 MPa-level hot dip galvanized dual-phase steel for an automobile structure and a production method thereof.
Background
Along with the increasing serious problems of energy sources, resources and environment, the weight reduction, energy saving and consumption reduction of automobiles become the necessary trend of development of various countries. The China is taken as the first automobile market place of the world, the world is being advanced to the automobile in the strong world, with the fire explosion of new energy automobiles, the automobile industry in China rapidly develops in recent years, and only 2608.2 ten thousand and 2627.5 ten thousand of automobile sales in 2021 are respectively completed, and the first global automobile sales are kept for 13 years continuously. In the light-weight automobile structural design, the adoption of high-strength and ultra-high-strength steel plates in a large amount has become the direction of the common efforts of modern automobile manufacturing industry and steel production enterprises. The 600 MPa-level hot dip galvanized dual phase steel for the automobile structure is high strength steel with excellent performance, and has the microstructure that hard island martensite with a certain volume fraction is dispersed and distributed on a ferrite matrix, the microstructure has the characteristics of continuous yield, high strength, low yield ratio, high work hardening rate, good uniform deformation, excellent bake hardening capacity, corrosion resistance and the like, becomes the first-choice high strength steel for the automobile, is mainly applied to structural members and reinforcing members of medium-high-grade automobiles, can be also applied to automobile covering members, the consumption of the high-surface-quality galvanized dual phase steel exceeds 70 percent in the advanced high-strength steel for the automobile, the application proportion is continuously improved, and the application prospect of the galvanized dual phase steel is wider and wider along with the higher and higher requirements of the automobile outer covering members on the corrosion resistance.
Patent document CN 109852900A discloses 600 MPa-level hot dip galvanized dual phase steel with different yield ratios and a production method thereof, wherein the chemical composition ratio is C:0.07 to 0.12 percent; mn:1.50 to 1.90 percent; si is less than or equal to 0.05%; alt:0.03 to 0.07 percent; cr:0.15 to 0.35 percent; mo:0.13 to 0.24 percent. The Mo element is added in the component design of the patent document, the content is higher (Mo: 0.13-0.24%), the Mo alloy cost is high, and the production cost of ton steel can be obviously increased; secondly, products with different yield ratios in the patent document are feasible in theory, are difficult to control in industrial mass production, and are only suitable for laboratory researches.
Patent document CN 113584375A discloses 600 MPa-level low-manganese nickel-containing alloyed hot dip galvanized dual phase steel with enhanced reaming performance and a production method thereof, wherein the chemical composition ratio is C:0.05 to 0.09 percent; mn:0.90 to 1.50 percent; si:0.05 to 0.20 percent; als:0.01 to 0.08 percent; cr:0.15 to 0.45 percent; mo:0.10 to 0.50 percent; ti:0.01 to 0.05 percent; b:0.0005 to 0.0065 percent; nb:0.01 to 0.05 percent; cu:0.05 to 0.80 percent; ni:0.05 to 0.90 percent. According to the component design of the patent document, a plurality of noble metal elements such as Mo, ti, B, nb, cu, ni and the like are added, the content is high, and the production cost of ton steel is obviously increased.
Patent document CN 102644021A discloses 600 MPa-level cold-rolled dual-phase steel with low process sensitivity and a production method thereof, wherein the chemical composition ratio is C: 0.06-0.12%; mn:1.0 to 3.0 percent; si is less than or equal to 0.1 percent; al:0.8 to 1.5 percent; mo:0.1 to 0.3 percent; p is less than or equal to 0.01%; s is less than or equal to 0.005 percent. In the component design of the patent document, the content of Mn and Al is higher, the Mn is high, center segregation is easy to form, the stamping performance is influenced, the Al is high, the smelting continuous casting performance is not beneficial to continuous production, and in addition, the patent document adopts Mo with higher price, so that the production cost of ton steel is obviously increased; secondly, the patent document is a cold-rolled product, and the corrosion resistance effect of the cold-rolled product is far less than that of a galvanized product.
Disclosure of Invention
Aiming at one or more problems in the prior art, one aspect of the invention provides 600 MPa-level hot dip galvanized dual phase steel for an automobile structure, which comprises the following chemical components in percentage by mass: c:0.10 to 0.12 percent, si:0.28 to 0.35 percent, mn:1.50 to 1.65 percent, P: less than or equal to 0.020%, S: less than or equal to 0.003 percent, alt:0.020 to 0.050 percent, cr:0.30 to 0.40 percent, ca:0.0008 to 0.0020 percent, and the balance of Fe and unavoidable impurities;
the production method of 600 MPa-level hot dip galvanized dual-phase steel for the automobile structure comprises a hot dip galvanizing process, wherein in the hot dip galvanizing process, uncoiled chilled coiled steel is heated to perform continuous annealing and hot dip galvanizing, wherein the heating temperature and the soaking temperature are 800+/-20 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; the slow cooling temperature is 700+/-20 ℃, and the slow cooling speed is 4-6 ℃/s; the rapid cooling temperature is 465+/-10 ℃, and the rapid cooling speed is 25-30 ℃/s; cooling to below 240 ℃ at the temperature of 460+/-10 ℃ in a zinc pot, taking out of the zinc pot, cooling to room temperature at the speed of 14-16 ℃/s, and then carrying out water quenching and drying; the finishing elongation is 0.2-0.4%, and the withdrawal elongation is 0.2-0.3%.
In some embodiments, the microstructure of the 600 MPa-level hot dip galvanized dual phase steel for the automobile structure is mainly ferrite and island martensite, and the mechanical properties meet the following conditions: yield strength 378-400 MPa, tensile strength 637-662 MPa, elongation not less than 22%, yield ratio not more than 0.60, strain hardening index n not less than 0.15, and bake hardening value not less than 52MPa.
The invention also provides a production method of 600 MPa-level hot dip galvanized dual-phase steel for an automobile structure, which comprises the following process steps: smelting, continuous casting, hot rolling, acid rolling and hot galvanizing; in the hot galvanizing process, the uncoiled chilled coil steel is heated to carry out continuous annealing and hot dip galvanizing, wherein the heating temperature and the soaking temperature are 800+/-20 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; the slow cooling temperature is 700+/-20 ℃, and the slow cooling speed is 4-6 ℃/s; the rapid cooling temperature is 465+/-10 ℃, and the rapid cooling speed is 25-30 ℃/s; cooling to below 240 ℃ at the temperature of 460+/-10 ℃ in a zinc pot, taking out of the zinc pot, cooling to room temperature at the speed of 14-16 ℃/s, and then carrying out water quenching and drying; the finishing elongation is 0.2-0.4%, and the withdrawal elongation is 0.2-0.3%.
In some embodiments, the smelting-continuous casting process includes the steps of: KR desulfurization, converter, LF refining, RH vacuum treatment, slab continuous casting and slow cooling; wherein the molten steel of the casting machine comprises the following components: 0.10 to 0.12 percent, si:0.28 to 0.35 percent, mn:1.50 to 1.65 percent, P: less than or equal to 0.020%, S: less than or equal to 0.003 percent, alt:0.020 to 0.050 percent, cr:0.30 to 0.40 percent, ca:0.0008 to 0.0020 percent, and the balance of Fe and unavoidable impurities.
In some embodiments, the hot rolling process comprises the steps of: heating a casting blank, rough rolling, finish rolling, cooling and coiling; wherein the tapping temperature of the casting blank is 1230+/-20 ℃, the rough rolling is performed by adopting a 3+3 mode 2-frame rolling mill, the finish rolling is performed by adopting a 7-frame continuous variable convexity rolling mill, and the thickness of the intermediate blank is 40-45 mm; the initial rolling temperature of the finish rolling is 1030+/-30 ℃, the final rolling temperature of the finish rolling is 880+/-20 ℃, and the thickness of the hot rolled steel strip is 2.0-6.0 mm; the cooling adopts laminar cooling equipment and a front dispersion cooling mode, the cooling speed is 20+/-5 ℃/s, and the coiling temperature is 560+/-20 ℃.
In some embodiments, the acid rolling process is specifically: and (3) pickling the hot-rolled steel strip, removing the surface iron scales, and then cold-rolling the hot-rolled steel strip by a 5-frame cold-rolling mill until the cold-rolling reduction is 53-72%, wherein the cold-rolling reduction is 0.7-2.0 mm, thereby obtaining the chilled coil steel.
In some embodiments, the hot dip galvanizing process is specifically: uncoiling the chilled coil steel, heating to perform continuous annealing and hot dip galvanizing, wherein the heating temperature and the soaking temperature are 800+/-20 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; the slow cooling temperature is 700+/-20 ℃ and the slow cooling speed is 5 ℃/s; the rapid cooling temperature is 465+/-10 ℃, and the rapid cooling speed is 25-30 ℃/s; the temperature of the zinc is 460+/-10 ℃ in a zinc pot, the zinc is cooled to below 240 ℃ at 15 ℃/s after being taken out of the zinc pot, and then the zinc is dried to room temperature through water quenching; the finishing elongation is 0.2-0.4%, and the withdrawal elongation is 0.2-0.3%.
The production method of the 600 MPa-level hot dip galvanized dual phase steel for the automobile structure provided by the technical scheme adopts the C-Si-Mn-Cr microalloying component design, and is matched with reasonable hot rolling control rolling and acid rolling galvanization processes to provide the 600 MPa-level hot dip galvanized dual phase steel for the automobile structure, and the steel microstructure mainly comprises ferrite and island-shaped martensite, and the mechanical properties of the steel are as follows: yield strength 378-400 MPa, tensile strength 637-662 MPa, elongation not less than 22%, yield ratio not more than 0.60, strain hardening index n not less than 0.15, and bake hardening value not less than 52MPa. The steel has the comprehensive properties of continuous yield, high strength, low yield ratio, high work hardening rate, good uniform deformation, excellent bake hardening capacity, corrosion resistance and the like, meets the good matching of strength and formability, and simultaneously, the surface quality of the hot dip galvanized dual-phase steel product produced by the invention is good, and meets the requirements of EN 10346:2009 standard requirements and user usage requirements. On the other hand, the 600 MPa-level hot dip galvanized dual-phase steel for the automobile structure provided by the invention does not contain Mo element with higher cost, so that the cost is lower, and the market competitiveness of the steel can be improved. The steel of the invention can well meet the requirements of the automobile industry on energy conservation, safety, weight reduction, environmental protection, corrosion resistance and the like.
Drawings
FIG. 1 is a microstructure of 600MPa grade hot dip galvanized dual phase steel for automobile construction, which is produced in example 1.
Detailed Description
The invention aims to provide 600 MPa-level hot dip galvanized dual-phase steel for an automobile structure and a production method thereof. The method is realized by the following technical scheme.
The 600MPa hot dip galvanized dual phase steel for the automobile structure comprises the following chemical components in percentage by mass: c:0.10 to 0.12 percent, si:0.28 to 0.35 percent, mn:1.50 to 1.65 percent, P: less than or equal to 0.020%, S: less than or equal to 0.003 percent, alt:0.020 to 0.050 percent, cr:0.30 to 0.40 percent, ca:0.0008 to 0.0020 percent, and the balance of Fe and unavoidable impurities;
the production method of 600 MPa-level hot dip galvanized dual-phase steel for the automobile structure comprises a hot dip galvanizing process, wherein in the hot dip galvanizing process, uncoiled chilled coiled steel is heated to perform continuous annealing and hot dip galvanizing, wherein the heating temperature and the soaking temperature are 800+/-20 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; the slow cooling temperature is 700+/-20 ℃, and the slow cooling speed is 4-6 ℃/s; the rapid cooling temperature is 465+/-10 ℃, and the rapid cooling speed is 25-30 ℃/s; cooling to below 240 ℃ at the temperature of 460+/-10 ℃ in a zinc pot, taking out of the zinc pot, cooling to room temperature at the speed of 14-16 ℃/s, and then carrying out water quenching and drying; the finishing elongation is 0.2-0.4%, and the withdrawal elongation is 0.2-0.3%.
In some embodiments, the microstructure of the 600 MPa-level hot dip galvanized dual phase steel for the automobile structure is mainly ferrite and island martensite, and the mechanical properties meet the following conditions: yield strength 378-400 MPa, tensile strength 637-662 MPa, elongation not less than 22%, yield ratio not more than 0.60, strain hardening index n not less than 0.15, and bake hardening value not less than 52MPa.
The production method of 600 MPa-level hot dip galvanized dual phase steel for automobile structure provided by the invention comprises the following process steps: smelting, continuous casting, hot rolling, acid rolling and hot galvanizing; in the hot galvanizing process, the uncoiled chilled coil steel is heated to carry out continuous annealing and hot dip galvanizing, wherein the heating temperature and the soaking temperature are 800+/-20 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; the slow cooling temperature is 700+/-20 ℃, and the slow cooling speed is 4-6 ℃/s; the rapid cooling temperature is 465+/-10 ℃, and the rapid cooling speed is 25-30 ℃/s; cooling to below 240 ℃ at the temperature of 460+/-10 ℃ in a zinc pot, taking out of the zinc pot, cooling to room temperature at the speed of 14-16 ℃/s, and then carrying out water quenching and drying; the finishing elongation is 0.2-0.4%, and the withdrawal elongation is 0.2-0.3%.
In some embodiments, the smelting-continuous casting process includes the steps of: KR desulfurization, converter, LF refining, RH vacuum treatment, slab continuous casting and slow cooling; wherein the molten steel of the casting machine comprises the following components: 0.10 to 0.12 percent, si:0.28 to 0.35 percent, mn:1.50 to 1.65 percent, P: less than or equal to 0.020%, S: less than or equal to 0.003 percent, alt:0.020 to 0.050 percent, cr:0.30 to 0.40 percent, ca:0.0008 to 0.0020 percent, and the balance of Fe and unavoidable impurities.
In some embodiments, the hot rolling process includes the steps of: heating a casting blank, rough rolling, finish rolling, cooling and coiling; wherein the tapping temperature of the casting blank is 1230+/-20 ℃, the rough rolling is performed by adopting a 3+3 mode 2-frame rolling mill, the finish rolling is performed by adopting a 7-frame continuous variable convexity rolling mill, and the thickness of the intermediate blank is 40-45 mm; the initial rolling temperature of the finish rolling is 1030+/-30 ℃, the final rolling temperature of the finish rolling is 880+/-20 ℃, and the thickness of the hot rolled steel strip is 2.0-6.0 mm; the cooling adopts laminar cooling equipment and a front dispersion cooling mode, the cooling speed is 20+/-5 ℃/s, and the coiling temperature is 560+/-20 ℃.
In some embodiments, the acid rolling process is specifically: and (3) pickling the hot-rolled steel strip, removing the surface iron scales, and then cold-rolling the hot-rolled steel strip by a 5-frame cold-rolling mill until the cold-rolling reduction is 53-72%, wherein the cold-rolling reduction is 0.7-2.0 mm, thereby obtaining the chilled coil steel.
In some embodiments, the hot dip galvanizing process is specifically: uncoiling the chilled coil steel, heating to perform continuous annealing and hot dip galvanizing, wherein the heating temperature and the soaking temperature are 800+/-20 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; the slow cooling temperature is 700+/-20 ℃ and the slow cooling speed is 5 ℃/s; the rapid cooling temperature is 465+/-10 ℃, and the rapid cooling speed is 25-30 ℃/s; the temperature of the zinc is 460+/-10 ℃ in a zinc pot, the zinc is cooled to below 240 ℃ at 15 ℃/s after being taken out of the zinc pot, and then the zinc is dried to room temperature through water quenching; the finishing elongation is 0.2-0.4%, and the withdrawal elongation is 0.2-0.3%.
The following describes the invention in detail by way of specific examples, which are intended to aid in understanding the invention and are not intended to limit the invention.
Example 1
Carrying out desulfurization pretreatment on molten iron, decarburizing and dephosphorizing the molten iron by adopting top-bottom combined blown converter smelting to obtain molten steel, blowing argon in the whole process of converter smelting, adding the scrap steel into a converter, and tapping the converter at a temperature of 1653 ℃. And then carrying out LF external refining on the molten steel smelted by the converter, wherein the refining in-situ temperature is more than or equal to 1566 ℃, and carrying out temperature measurement and component fine adjustment on the LF external refining, wherein the chemical components of the LF external refining for a casting machine are shown in the table 1. And (3) the continuous slab casting superheat degree is 26 ℃, and then the quality inspection of the continuous casting slab is carried out after the slab is cleaned and slowly cooled. The heating temperature of the plate blank is 1226 ℃ and the heating time is 230min, and the heated plate blank is dephosphorized by high-pressure water. And (3) fixing the width by a width fixing press, adopting 2 frames for rough rolling and 7 frames for CVC finish rolling. The initial rolling temperature of the finish rolling is 1037 ℃, the final rolling temperature of the finish rolling is 885 ℃, and the thickness of the finished product is 2.5mm. The laminar cooling adopts pre-dispersion cooling, the cooling speed is 20 ℃/s, and the temperature of the steel strip is reduced to 578 ℃ for coiling. The hot-rolled strip steel is pickled by a hydrochloric acid tank, the acid tank adopts the i-BOX technology newly developed by MH, the operation and maintenance are greatly simplified, the energy and labor are saved, after the surface iron scale of the hot-rolled strip steel is removed, the hot-rolled strip steel is cold-rolled by a 5-frame UCM rolling mill, the cold rolling reduction rate is 72%, and the rolling is carried out until the target thickness is 0.7mm. The cold hard coil galvanization process is carried out in a hot galvanizing production process by adopting a American steel joint method and a vertical annealing furnace, the running speed of the steel belt in a furnace area is 85m/min, the heating temperature and the soaking temperature are 800 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; the slow cooling temperature is 690 ℃, the slow cooling speed is 5 ℃/s, and the time is 12-14 s; the rapid cooling temperature is 470 ℃, the rapid cooling speed is 26 ℃/s, and the time is 8-12 s; the zinc is put into a zinc pot at the temperature of 465 ℃ for 20 to 30s, cooled to below 240 ℃ at 15 ℃/s after being taken out of the zinc pot, and then dried to room temperature through water quenching; the finishing elongation was 0.2% and the withdrawal elongation was 0.2%, and finally the product properties were examined as shown in Table 2 below. As shown in fig. 1, a microstructure of the hot dip galvanized dual phase steel having a tensile strength of 600MPa grade obtained in this example is shown, and it can be seen that the microstructure is ferrite and island-like martensite.
Example 2
Carrying out desulfurization pretreatment on molten iron, decarburizing and dephosphorizing the molten iron by adopting top-bottom combined blown converter smelting to obtain molten steel, blowing argon in the whole process of converter smelting, adding the scrap steel into a converter, and tapping the converter at the temperature of 1645 ℃. And then carrying out LF external refining on the molten steel smelted by the converter, wherein the refining in-situ temperature is more than or equal to 1564 ℃, and carrying out temperature measurement and component fine adjustment on the LF external refining, wherein the chemical components of the LF external refining for a casting machine are shown in the table 1. And (3) the continuous slab casting superheat degree is 28 ℃, and then the quality inspection of the continuous casting slab is carried out after the slab is cleaned and slowly cooled. The heating temperature of the plate blank is 1233 ℃, the heating time is 228min, and the heated plate blank is subjected to high-pressure water dephosphorization. And (3) fixing the width by a width fixing press, adopting 2 frames for rough rolling and 7 frames for CVC finish rolling. The finish rolling temperature is 1030 ℃, the finish rolling finishing temperature is 878 ℃, and the thickness of the finished product is 3.2mm. The laminar cooling adopts pre-dispersion cooling, the cooling speed is 20 ℃/s, and the temperature of the steel belt is reduced to 570 ℃ for coiling. The hot-rolled strip steel is pickled by a hydrochloric acid tank, the acid tank adopts the i-BOX technology newly developed by MH, the operation and maintenance are greatly simplified, the energy and labor are saved, after the surface iron scale of the hot-rolled strip steel is removed, the hot-rolled strip steel is cold-rolled by a 5-frame UCM rolling mill, the cold rolling reduction rate is 69%, and the rolling reduction rate is 1.0mm. The cold hard coil galvanization process is carried out in a hot galvanizing production process by adopting a American steel joint method and a vertical annealing furnace, the running speed of the steel belt in a furnace area is 80m/min, the heating temperature and the soaking temperature are 795 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; the slow cooling temperature is 700 ℃, the slow cooling speed is 5 ℃/s, and the time is 12-14 s; the rapid cooling temperature is 465 ℃, the rapid cooling speed is 27 ℃/s, and the time is 8-12 s; feeding the zinc into a zinc pot at 462 ℃ for 20-30 s, cooling to below 240 ℃ at 15 ℃/s after the zinc is discharged from the zinc pot, and then carrying out water quenching and drying to room temperature; the finishing elongation was 0.2% and the withdrawal elongation was 0.2%, and finally the product properties were examined as shown in Table 2 below.
Example 3
Carrying out desulfurization pretreatment on molten iron, decarburizing and dephosphorizing the molten iron by adopting top-bottom combined blown converter smelting to obtain molten steel, blowing argon in the whole process of converter smelting, adding the scrap steel into a converter, and tapping the converter at the temperature of 1643 ℃. And then carrying out LF external refining on the molten steel smelted by the converter, wherein the refining in-situ temperature is more than or equal to 1560 ℃, and carrying out temperature measurement and component fine adjustment on the LF external refining, wherein the chemical components of the LF external refining for a casting machine are shown in the table 1. And (3) the continuous slab casting superheat degree is 27 ℃, and then the quality inspection of the continuous casting slab is carried out after the slab is cleaned and slowly cooled. The heating temperature of the plate blank is 1225 ℃, the heating time is 235min, and the heated plate blank is subjected to high-pressure water dephosphorization. And (3) fixing the width by a width fixing press, adopting 2 frames for rough rolling and 7 frames for CVC finish rolling. The finish rolling temperature is 1021 ℃, the finish rolling temperature is 892 ℃, and the thickness of the finished product is 3.5mm. The laminar cooling adopts pre-dispersion cooling, the cooling speed is 20 ℃/s, and the temperature of the steel belt is reduced to 565 ℃ for coiling. The hot-rolled strip steel is pickled by a hydrochloric acid tank, the acid tank adopts the i-BOX technology newly developed by MH, the operation and maintenance are greatly simplified, the energy and labor are saved, after the surface iron scale of the hot-rolled strip steel is removed, the hot-rolled strip steel is cold-rolled by a 5-frame UCM rolling mill, the cold rolling reduction rate is 66%, and the rolling reduction rate is 1.2mm. The cold hard coil galvanization process is carried out in a hot galvanizing production process by adopting a American steel joint method and a vertical annealing furnace, the running speed of the steel belt in a furnace area is 86m/min, the heating temperature and the soaking temperature are 812 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; the slow cooling temperature is 696 ℃, the slow cooling speed is 5 ℃/s, and the time is 12-14 s; the rapid cooling temperature is 465 ℃, the rapid cooling speed is 25 ℃/s, and the time is 8-12 s; the zinc is put into a zinc pot at 460 ℃ for 20 to 30 seconds, cooled to below 240 ℃ at 15 ℃/s after being taken out of the zinc pot, and then dried to room temperature through water quenching; the finishing elongation was 0.2% and the withdrawal elongation was 0.2%, and finally the product properties were examined as shown in Table 2 below.
Example 4
Carrying out desulfurization pretreatment on molten iron, decarburizing and dephosphorizing the molten iron by adopting top-bottom combined blown converter smelting to obtain molten steel, blowing argon in the whole process of converter smelting, adding the scrap steel into a converter, and tapping the converter at the temperature of 1646 ℃. And then carrying out LF external refining on the molten steel smelted by the converter, wherein the refining in-situ temperature is more than or equal to 1562 ℃, and carrying out temperature measurement and component fine adjustment on the LF external refining, wherein the chemical components of the LF external refining for a casting machine are shown in the table 1. And (3) the continuous slab casting superheat degree is 32 ℃, and then the quality inspection of the continuous casting slab is carried out after the slab is cleaned and slowly cooled. The heating temperature of the plate blank is 1235 ℃, the heating time is 232min, and the heated plate blank is subjected to high-pressure water dephosphorization. And (3) fixing the width by a width fixing press, adopting 2 frames for rough rolling and 7 frames for CVC finish rolling. The finish rolling temperature is 1026 ℃, the finish rolling finishing temperature is 882 ℃, and the thickness of the finished product is 3.8mm. The laminar cooling adopts pre-dispersion cooling, the cooling speed is 20 ℃/s, and the temperature of the steel strip is reduced to 576 ℃ for coiling. The hot-rolled strip steel is pickled by a hydrochloric acid tank, the acid tank adopts the i-BOX technology newly developed by MH, the operation and maintenance are greatly simplified, the energy and labor are saved, after the surface iron scale of the hot-rolled strip steel is removed, the hot-rolled strip steel is cold-rolled by a 5-frame UCM rolling mill, the cold rolling reduction rate is 61%, and the rolling reduction rate is 1.5mm. The cold hard coil galvanization process is carried out in a hot galvanizing production process by adopting a American steel joint method and a vertical annealing furnace, the running speed of the steel belt in a furnace area is 82m/min, the heating temperature and the soaking temperature are 808 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; slowly cooling at 707 deg.c and 5 deg.c/s for 12-14 s; the rapid cooling temperature is 466 ℃, the rapid cooling speed is 28 ℃/s, and the time is 8-12 s; feeding the zinc into a zinc pot at 462 ℃ for 20-30 s, cooling to below 240 ℃ at 15 ℃/s after the zinc is discharged from the zinc pot, and then carrying out water quenching and drying to room temperature; the finishing elongation was 0.2% and the withdrawal elongation was 0.2%, and finally the product properties were examined as shown in Table 2 below.
Example 5
Carrying out desulfurization pretreatment on molten iron, decarburizing and dephosphorizing the molten iron by adopting top-bottom combined blown converter smelting to obtain molten steel, blowing argon in the whole process of converter smelting, adding the scrap steel into a converter, and tapping the converter at a temperature of 1652 ℃. And then carrying out LF external refining on the molten steel smelted by the converter, wherein the refining in-situ temperature is more than or equal to 1563 ℃, and carrying out temperature measurement and component fine adjustment on the LF external refining, wherein the chemical components of the LF external refining for a casting machine are shown in the table 1. And (3) the continuous slab casting superheat degree is 30 ℃, and then the quality inspection of the continuous casting slab is carried out after the slab is cleaned and slowly cooled. The heating temperature of the plate blank is 1218 ℃ and the heating time is 226min, and the heated plate blank is subjected to high-pressure water dephosphorization. And (3) fixing the width by a width fixing press, adopting 2 frames for rough rolling and 7 frames for CVC finish rolling. The initial rolling temperature of the finish rolling is 1033 ℃, the final rolling temperature of the finish rolling is 880 ℃, and the thickness of the finished product is 4.0mm. The laminar cooling adopts pre-dispersion cooling, the cooling speed is 20 ℃/s, and the temperature of the steel strip is reduced to 568 ℃ for coiling. The hot-rolled strip steel is pickled by a hydrochloric acid tank, the acid tank adopts the i-BOX technology newly developed by MH, the operation and maintenance are greatly simplified, the energy and labor are saved, after the surface iron scale of the hot-rolled strip steel is removed, the hot-rolled strip steel is cold-rolled by a 5-frame UCM rolling mill, the cold rolling reduction rate is 60%, and the rolling reduction rate is 1.6mm. The cold hard coil galvanization process is carried out in a hot galvanizing production process by adopting a American steel joint method and a vertical annealing furnace, the running speed of the steel belt in a furnace area is 85m/min, the heating temperature and the soaking temperature are 792 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; the slow cooling temperature is 690 ℃, the slow cooling speed is 5 ℃/s, and the time is 12-14 s; the rapid cooling temperature is 472 ℃, the rapid cooling speed is 30 ℃/s, and the time is 8-12 s; the zinc is put into a zinc pot at 460 ℃ for 20 to 30 seconds, cooled to below 240 ℃ at 15 ℃/s after being taken out of the zinc pot, and then dried to room temperature through water quenching; the finishing elongation was 0.3% and the withdrawal elongation was 0.3%, and finally the product performance was measured as shown in table 2 below.
Example 6
Carrying out desulfurization pretreatment on molten iron, decarburizing and dephosphorizing the molten iron by adopting top-bottom combined blown converter smelting to obtain molten steel, blowing argon in the whole process of converter smelting, adding the scrap steel into a converter, and tapping the converter at the temperature of 1641 ℃. And then carrying out LF external refining on the molten steel smelted by the converter, wherein the refining in-situ temperature is more than or equal to 1560 ℃, and carrying out temperature measurement and component fine adjustment on the LF external refining, wherein the chemical components of the LF external refining for a casting machine are shown in the table 1. And (3) the continuous slab casting superheat degree is 25 ℃, and then the slab cleaning, slow cooling and continuous casting quality inspection are carried out. The heating temperature of the plate blank is 1237 ℃, the heating time is 233min, and the heated plate blank is subjected to high-pressure water dephosphorization. And (3) fixing the width by a width fixing press, adopting 2 frames for rough rolling and 7 frames for CVC finish rolling. The finish rolling temperature is 1025 ℃, the finish rolling temperature is 890 ℃, and the thickness of the finished product is 4.3mm. The laminar cooling adopts pre-dispersion cooling, the cooling speed is 20 ℃/s, and the temperature of the steel belt is reduced to 573 ℃ for coiling. The hot-rolled strip steel is pickled by a hydrochloric acid tank, the acid tank adopts the i-BOX technology newly developed by MH, the operation and maintenance are greatly simplified, the energy and labor are saved, after the surface iron scale of the hot-rolled strip steel is removed, the hot-rolled strip steel is cold-rolled by a 5-frame UCM rolling mill, the cold rolling reduction rate is 53%, and the rolling reduction rate is 2.0mm. The cold hard coil galvanization process is carried out in a hot galvanizing production process by adopting a American steel joint method and a vertical annealing furnace, the running speed of the steel belt in a furnace area is 87m/min, the heating temperature and the soaking temperature are both 806 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; the slow cooling temperature is 705 ℃, the slow cooling speed is 5 ℃/s, and the time is 12-14 s; the rapid cooling temperature is 463 ℃, the rapid cooling speed is 26 ℃/s, and the time is 8-12 s; the zinc is put into a zinc pot at 460 ℃ for 20 to 30 seconds, cooled to below 240 ℃ at 15 ℃/s after being taken out of the zinc pot, and then dried to room temperature through water quenching; the finishing elongation was 0.4% and the withdrawal elongation was 0.3%, and finally the product properties were examined as shown in Table 2 below.
Comparative example 1
The production process was as described in example 1, except that the chemical composition for the casting machine for the external refining of LF furnace was different from that used in example 1, as shown in Table 1 below. Finally, product performance was tested as shown in table 2 below.
Comparative example 2
The production process was as described in example 5, except that the LF external refining was used for the caster chemistry different from that used in example 5, as shown in Table 1 below. Finally, product performance was tested as shown in table 2 below.
Comparative examples 3 to 4
The production methods of comparative examples 3 to 4 were the same as those shown in example 1 except that the heating temperature and the soaking temperature in the hot galvanizing process, and the slow cooling temperature were different from example 1, specifically, the heating temperature and the soaking temperature of comparative example 3 were 780 ℃ and the slow cooling temperature was 640 ℃; the heating temperature and soaking temperature of comparative example 4 were both 830℃and the slow cooling temperature 690 ℃. Finally, product performance was tested as shown in table 2 below.
TABLE 1 chemical Components (wt%) of comparative examples 1 to 4 of inventive examples 1 to 6
Examples C Si Mn P S Alt Cr Ca
1 0.105 0.30 1.55 0.017 0.003 0.030 0.305 0.0018
2 0.110 0.28 1.50 0.016 0.002 0.028 0.350 0.0020
3 0.108 0.29 1.60 0.017 0.002 0.038 0.380 0.0016
4 0.120 0.32 1.65 0.014 0.003 0.032 0.326 0.0014
5 0.116 0.35 1.52 0.015 0.002 0.035 0.346 0.0018
6 0.115 0.30 1.62 0.016 0.003 0.036 0.362 0.0015
Comparative example 1 0.106 0.33 1.40 0.015 0.003 0.040 0.300 0.0016
Comparative example 2 0.118 0.32 1.35 0.016 0.002 0.036 0.263 0.0018
Comparative example 3 0.105 0.30 1.55 0.017 0.003 0.030 0.305 0.0018
Comparative example 4 0.105 0.30 1.55 0.017 0.003 0.030 0.305 0.0018
The steel coils of examples 1 to 6 and comparative examples 1 to 4 of the present invention were subjected to mechanical property test, and the test results are shown in Table 2.
TABLE 2 mechanical Properties of the Steel rolls of examples 1 to 6 and comparative examples 1 to 4 according to the present invention
From the contents recorded in the table 1 and the table 2, the mechanical properties of the hot dip galvanized dual phase steel with the tensile strength of 600MPa provided by the invention can be satisfied: the yield strength is 340-420 MPa, the tensile strength is 590-680 MPa, the elongation is more than or equal to 20%, the yield ratio is less than or equal to 0.60, the strain hardening index n is more than or equal to 0.15, the bake hardening value is more than or equal to 30MPa, and the method preferably can meet the following conditions: the yield strength is 378-400 MPa, the tensile strength is 637-662 MPa, the elongation is more than or equal to 22%, the yield ratio is less than or equal to 0.60, the strain hardening index n is more than or equal to 0.15, the bake hardening value is more than or equal to 52MPa, the steel has the comprehensive properties of continuous yield, high strength, low yield ratio, high work hardening rate, good uniform deformation, excellent bake hardening capacity, corrosion resistance and the like, the good matching of strength and formability is satisfied, and meanwhile, the surface quality of the hot dip galvanized dual-phase steel product produced by the method is good, and EN 10346 is satisfied: 2009 standard requirements and user usage requirements. According to the results of comparative examples 1-2, when the chemical component content of the hot dip galvanized dual phase steel cannot meet the requirements of the invention, particularly the content of Mn, the obtained dual phase steel cannot meet the preset mechanical properties, for example, the yield strength allowance of the dual phase steel obtained in comparative example 1 is smaller, and the steel is easy to fail in the use process; the dual phase steel obtained in comparative example 2 did not meet the predetermined strength requirement and the bake hardening value was less abundant. According to the results of comparative examples 3 to 4, when the chemical component content of the hot dip galvanized dual phase steel meets the requirements of the present invention, but the production method cannot meet the requirements of the present invention, the annealing temperature (slow cooling temperature) is mainly used, the obtained dual phase steel may not reach the predetermined strength, the bake hardening value is smaller, the molding property of the product is poor, and the product is easy to crack in the subsequent processing and use.
Finally, it should be noted that: the foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the technical solutions described in the foregoing embodiments, or that equivalents may be substituted for part of the technical features thereof. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (3)

1. The 600 MPa-level hot dip galvanized dual phase steel for the automobile structure comprises the following chemical components in percentage by mass: c:0.10 to 0.12 percent, si:0.28 to 0.35 percent, mn:1.50 to 1.65 percent, P: less than or equal to 0.020%, S: less than or equal to 0.003 percent, alt:0.020 to 0.050 percent, cr:0.30 to 0.40 percent, ca:0.0008 to 0.0020 percent, and the balance of Fe and unavoidable impurities;
the production method of 600 MPa-level hot dip galvanized dual-phase steel for the automobile structure comprises the following process steps: smelting, continuous casting, hot rolling, acid rolling and hot galvanizing;
the hot rolling process comprises the following steps: heating a casting blank, rough rolling, finish rolling, cooling and coiling; wherein the tapping temperature of the casting blank is 1230+/-20 ℃, the rough rolling is performed by adopting a 3+3 mode 2-frame rolling mill, the finish rolling is performed by adopting a 7-frame continuous variable convexity rolling mill, and the thickness of the intermediate blank is 40-45 mm; the initial rolling temperature of the finish rolling is 1030+/-30 ℃, the final rolling temperature of the finish rolling is 880+/-20 ℃, and the thickness of the hot rolled steel strip is 2.0-6.0 mm; the cooling adopts laminar flow cooling equipment and a front dispersion cooling mode, the cooling speed is 20+/-5 ℃/s, and the coiling temperature is 560+/-20 ℃;
the acid rolling process comprises the following steps: pickling the hot rolled steel strip, removing surface iron scales, and then cold-rolling the hot rolled steel strip by a 5-frame cold rolling mill until the cold rolling reduction is 53-72%, wherein the cold rolling reduction is 0.7-2.0 mm, thereby obtaining cold-rolled hard coil steel;
in the hot galvanizing process, the uncoiled chilled coil steel is heated to carry out continuous annealing and hot dip galvanizing, wherein the heating temperature and the soaking temperature are 800+/-20 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; the slow cooling temperature is 700+/-20 ℃, and the slow cooling speed is 4-6 ℃/s; the rapid cooling temperature is 465+/-10 ℃, and the rapid cooling speed is 25-30 ℃/s; cooling to below 240 ℃ at the temperature of 460+/-10 ℃ in a zinc pot, taking out of the zinc pot, cooling to room temperature at the speed of 14-16 ℃/s, and then carrying out water quenching and drying; the finishing elongation is 0.2-0.4%, and the withdrawal elongation is 0.2-0.3%;
the mechanical properties of the 600 MPa-level hot dip galvanized dual-phase steel for the automobile structure meet the following conditions: yield strength 378-400 MPa, tensile strength 637-662 MPa, elongation not less than 22%, yield ratio not more than 0.60, strain hardening index n not less than 0.15, and bake hardening value not less than 52MPa.
2. The 600 MPa-grade hot-dip galvanized dual phase steel for automobile construction according to claim 1, wherein the microstructure is mainly ferrite and island-like martensite.
3. The production method of 600 MPa-grade hot-dip galvanized dual-phase steel for automobile structures as claimed in claim 1 or 2, comprising the following process steps: smelting, continuous casting, hot rolling, acid rolling and hot galvanizing; wherein:
the smelting-continuous casting process comprises the following steps: KR desulfurization, converter, LF refining, RH vacuum treatment, slab continuous casting and slow cooling; wherein the molten steel of the casting machine comprises the following components: 0.10 to 0.12 percent, si:0.28 to 0.35 percent, mn:1.50 to 1.65 percent, P: less than or equal to 0.020%, S: less than or equal to 0.003 percent, alt:0.020 to 0.050 percent, cr:0.30 to 0.40 percent, ca:0.0008 to 0.0020 percent, and the balance of Fe and unavoidable impurities;
the hot rolling process comprises the following steps: heating a casting blank, rough rolling, finish rolling, cooling and coiling; wherein the tapping temperature of the casting blank is 1230+/-20 ℃, the rough rolling is performed by adopting a 3+3 mode 2-frame rolling mill, the finish rolling is performed by adopting a 7-frame continuous variable convexity rolling mill, and the thickness of the intermediate blank is 40-45 mm; the initial rolling temperature of the finish rolling is 1030+/-30 ℃, the final rolling temperature of the finish rolling is 880+/-20 ℃, and the thickness of the hot rolled steel strip is 2.0-6.0 mm; the cooling adopts laminar flow cooling equipment and a front dispersion cooling mode, the cooling speed is 20+/-5 ℃/s, and the coiling temperature is 560+/-20 ℃;
the acid rolling process specifically comprises the following steps: pickling the hot rolled steel strip, removing surface iron scales, and then cold-rolling the hot rolled steel strip by a 5-frame cold rolling mill until the cold rolling reduction is 53-72%, wherein the cold rolling reduction is 0.7-2.0 mm, thereby obtaining cold-rolled hard coil steel;
the hot galvanizing process specifically comprises the following steps: uncoiling the chilled coil steel, heating to perform continuous annealing and hot dip galvanizing, wherein the heating temperature and the soaking temperature are 800+/-20 ℃, the heating time is 80-120 s, and the soaking time is 80-120 s; the slow cooling temperature is 700+/-20 ℃ and the slow cooling speed is 5 ℃/s; the rapid cooling temperature is 465+/-10 ℃, and the rapid cooling speed is 25-30 ℃/s; the temperature of the zinc is 460+/-10 ℃ in a zinc pot, the zinc is cooled to below 240 ℃ at 15 ℃/s after being taken out of the zinc pot, and then the zinc is dried to room temperature through water quenching; the finishing elongation is 0.2-0.4%, and the withdrawal elongation is 0.2-0.3%.
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