Production method of high-elongation 590MPa-grade galvanized dual-phase steel strip

Abstract

The invention discloses a production method of a high-elongation 590MPa-grade galvanized dual-phase steel strip. The production method comprises the following steps: (1) a smelting-continuous casting production process flow; molten steel for a casting machine comprises the following components in percentage by mass: 0.10-0.15% of C, less than or equal to 0.45% of S i, 1.45-1.70% of Mn, less than or equal to 0.020% of P, less than or equal to 0.010% of S, 0.40-0.60% of Alt, less than or equal to 0.025% of T i, 0.0008-0.0020% of Ca and the balance of Fe and inevitable impurities; the slab continuous casting superheat degree is 15-40 DEG C, and the pulling speed is controlled to be 0.8-1.5 m / min; (2) hot rolling production process flow; (3) pickling and cold rolling process flow; and (4) continuous hot galvanizing and finishing process flow. The galvanized dual-phase steel strip with the characteristics of high strength and high formability produced by the invention meets the characteristic requirements of safety, low energy consumption and complex forming in the automobile industry.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metallurgical plates, and particularly relates to a production method of a 590MPa-grade galvanized dual-phase steel strip with high elongation. BACKGROUND

[0002] With the development of automobile lightweight, higher requirements are put forward for the strength, complex formability and weldability of the steel plate for automobiles. The traditional dual-phase steel has been difficult to meet some specific demand fields, therefore, the development of a steel plate with high strength and high elongation has become a current research hotspot. As a kind of high-strength, low-alloy steel, the dual-phase steel has excellent mechanical properties and forming properties, and is widely used in the field of automobile manufacturing. However, the dual-phase steel strip on the market currently often has the problem of poor formability when the strength reaches the 590MPa level, which limits its application in some complex-shaped parts, in addition, galvanizing treatment is an effective means to improve the corrosion resistance of the steel plate. Therefore, how to produce a galvanized dual-phase steel strip with both high elongation and 590MPa-grade strength requirements has become a technical problem to be solved.

[0003] Currently, the 600MPa-grade galvanized dual-phase steel produced by Hunan Hualing Liansteel Special New Material Co., Ltd. (600MPa-grade galvanized dual-phase steel, preparation process and application, application number 202210989031.9) has a component design of Cr: 0.1-0.2%, and a finishing elongation of 0.5-0.8%, which is different from the component and process design of the present application. The higher finishing elongation affects the yield ratio and forming performance of the product, and the average elongation of 25% is lower than that of the present application. The 590MPa-grade hot-dip galvanized dual-phase steel produced by Pansteel Group Panzhihua Iron and Steel Research Institute Co., Ltd. (a 590MPa-grade hot-dip galvanized dual-phase steel and a preparation method, application number 202311333665.X) has a component design of C: 0.06-0.10%, Al: 0.015-0.070%, and Cr: 0.25-0.45%, which is different from the component design of the present application. The higher Cr content increases the cost of the product and affects the surface quality. The 600MPa-grade galvanized dual-phase steel produced by Wuhan Iron and Steel Co., Ltd. (a 600MPa-grade galvanized dual-phase steel for cars and a production method, application number 201510968690.4) has a component design of C: 0.04-0.09%, Mo: 0.01-0.30%, and Nb: 0.001-0.03%, which is higher and affects the cost of the product. The elongation is 21-25%, and the n value is 0.14-0.17, which is lower than that of the present application. SUMMARY

[0004] The purpose of the present application is to provide a production method of high-elongation 590MPa-grade galvanized dual-phase steel strip, and the produced galvanized dual-phase steel strip with high strength and high formability characteristics meets the characteristic requirements of safety, low energy consumption and complex forming of the automobile industry. p0.2 : 340-440MPa, tensile strength R m : 590-700MPa, elongation A 50 ≥ 27%, and strain hardening index n value ≥ 0.16.

[0005] To solve the above technical problems, the present application adopts the following technical solutions:

[0006] The present application is a production method of high-elongation 590MPa-grade galvanized dual-phase steel strip, comprising:

[0007] (1) Smelting-continuous casting production process: hot metal pretreatment-reverberatory furnace-LF refining-RH refining-continuous slab casting; wherein oxygen blowing decarburization and temperature rising are performed in the top and bottom combined blowing smelting of the reverberatory furnace, aluminum iron, manganese iron, silicon iron, etc. are added during the tapping process of the reverberatory furnace for deoxidization and alloying, P and S components are controlled, and the molten steel is prevented from being over-oxidized, and the tapping temperature is ≥ 1600℃; the LF furnace outer refining adopts LF full-process argon blowing process, the RH refining vacuum degree is ≤ 2.6mbar, the vacuum time is ≥ 10min, the molten steel composition is adjusted to the target composition according to the molten steel composition, and the molten steel composition for the casting machine is C: 0.10-0.15%, Si: ≤ 0.45%, Mn: 1.45-1.70%, P ≤ 0.020%, S ≤ 0.010%, Alt: 0.40-0.60%, Ti ≤ 0.025%, Ca: 0.0008-0.0020%, and the rest is Fe and inevitable impurities; the slab continuous casting superheat is 15-40℃, and the withdrawal speed is controlled at 0.8-1.5m / min;

[0008] (2) Hot rolling production process: casting blank heating-rough rolling-fine rolling-coiling; the casting blank time in the furnace is 170-230min, the out-of-furnace temperature is 1210-1280℃, the rough rolling adopts 3+3 mode 2-rack rolling mill rough rolling, the fine rolling adopts 7-rack rolling mill fine rolling, the fine rolling opening rolling temperature is 970-1050℃, the fine rolling final rolling temperature is 860-910℃, and the hot rolled steel strip thickness is 2.5-5.0mm; the cooling adopts laminar flow cooling equipment, and the coiling temperature is 530-590℃;

[0009] (3) Pickling and cold rolling process: after the hot rolled steel strip is pickled to remove the surface iron oxide scale, it is cold rolled through 5-rack cold rolling mill, the cold rolling reduction rate is 50-70%, and the thickness is 0.7-2.5mm;

[0010] (4) Continuous hot galvanizing, finishing process: after the cold hard steel strip is unwound, it is welded to continuously produce, the furnace area speed is 60-130 m / min, the soaking temperature is 790-840 DEG C, the slow cooling is to 670-710 DEG C, then cooling to 440-470 DEG C, the temperature of entering zinc pot is 440-480 DEG C, the tower top temperature of top roll cooling tower is 200-240 DEG C, the finishing elongation is 0.2 %-0.5 %, the stretch leveler elongation is less than or equal to 0.2 %.

[0011] Further, the percentage chemical composition of the galvanized dual-phase steel strip is C: 0.12-0.14%, Si: 0.31-0.43%, Mn: 1.55-1.64%, P: 0.015-0.018%, S: 0.001-0.005%, Alt: 0.43-0.58%, Ti: 0.016-0.022%, Ca: 0.0011-0.0020%, and the rest is Fe and inevitable impurities.

[0012] Further, the percentage chemical composition of the galvanized dual-phase steel strip is C: 0.14%, Si: 0.35%, Mn: 1.61%, P: 0.015%, S: 0.002%, Alt: 0.45%, Ti: 0.016%, Ca: 0.0011%, and the rest is Fe and inevitable impurities. The hot rolling raw material thickness is 3.5 mm, the furnace time is 198 min, the discharge temperature is 1226 DEG C, the finishing rolling opening rolling temperature is 999 DEG C, the final rolling temperature is 888 DEG C, and the coiling temperature is 585 DEG C; the cold rolling thickness is 1.2 mm, the speed is 95 m / min, the soaking temperature is 826 DEG C, the slow cooling temperature is 705 DEG C, the fast cooling temperature is 455 DEG C, the temperature of entering zinc pot is 464 DEG C, the cooling tower temperature is 205 DEG C, the finishing machine elongation is 0.24%, the stretch leveler elongation is 0.11%, and the product mechanical properties are: yield strength 369 MPa, tensile strength 650 MPa, elongation 34.0%, and n value 0.24.

[0013] Further, the percentage chemical composition of the galvanized dual-phase steel strip is C: 0.14%, Si: 0.31%, Mn: 1.64%, P: 0.017%, S: 0.001%, Alt: 0.43%, Ti: 0.022%, Ca: 0.0020%, and the rest is Fe and inevitable impurities. The hot rolling raw material thickness is 3.8 mm, the furnace time is 193 min, the discharge temperature is 1245 DEG C, the finishing rolling opening rolling temperature is 985 DEG C, the final rolling temperature is 895 DEG C, and the coiling temperature is 581 DEG C; the cold rolling thickness is 1.5 mm, the speed is 86 m / min, the soaking temperature is 819 DEG C, the slow cooling temperature is 699 DEG C, the fast cooling temperature is 449 DEG C, the temperature of entering zinc pot is 466 DEG C, the cooling tower temperature is 211 DEG C, the finishing machine elongation is 0.22%, the stretch leveler elongation is 0.15%, and the product mechanical properties are: yield strength 374 MPa, tensile strength 651 MPa, elongation 33.0%, and n value 0.23.

[0014] Furthermore, the percentage chemical composition of the galvanized duplex steel strip is C: 0.12%, Si: 0.43%, Mn: 1.59%, P: 0.016%, S: 0.005%, Alt: 0.58%, Ti: 0.020%, Ca: 0.0011%, with the remainder being Fe and unavoidable impurities. Hot-rolled raw material thickness 4.3mm, furnace time 202min, furnace exit temperature 1255℃, finishing rolling start temperature 1003℃, finishing rolling temperature 885℃, coiling temperature 563℃; cold-rolled thickness 1.8mm, speed 72m / min, soaking temperature 802℃, slow cooling temperature 685℃, rapid cooling temperature 461℃, zinc pot entry temperature 468℃, cooling tower temperature 220℃, finished elongation 0.40%, tensile elongation 0.19%, product mechanical properties: yield strength 421MPa, tensile strength 635MPa, elongation 29.5%, n-value 0.22.

[0015] Furthermore, the percentage chemical composition of the galvanized duplex steel strip is C: 0.13%, Si: 0.41%, Mn: 1.55%, P: 0.018%, S: 0.004%, Alt: 0.53%, Ti: 0.018%, Ca: 0.0018%, with the remainder being Fe and unavoidable impurities. Hot-rolled raw material thickness 4.5mm, furnace time 226min, furnace exit temperature 1256℃, finishing rolling start temperature 1011℃, finishing rolling temperature 872℃, coiling temperature 552℃; cold-rolled thickness 2.0mm, speed 66m / min, soaking temperature 811℃, slow cooling temperature 680℃, rapid cooling temperature 470℃, zinc pot entry temperature 472℃, cooling tower temperature 236℃, finished elongation 0.31%, tensile elongation 0.13%, product mechanical properties: yield strength 420MPa, tensile strength 644MPa, elongation 28.5%, n-value 0.22.

[0016] Furthermore, the percentage chemical composition of the galvanized duplex steel strip is C: 0.12%, Si: 0.43%, Mn: 1.59%, P: 0.016%, S: 0.005%, Alt: 0.58%, Ti: 0.020%, Ca: 0.0011%, with the remainder being Fe and unavoidable impurities. Hot-rolled raw material thickness 4.5mm, furnace time 228min, furnace exit temperature 1250℃, finishing rolling start temperature 1023℃, finishing rolling temperature 872℃, coiling temperature 557℃; cold-rolled thickness 2.2mm, speed 63m / min, soaking temperature 794℃, slow cooling temperature 680℃, rapid cooling temperature 466℃, zinc pot temperature 478℃, cooling tower temperature 233℃, finished elongation 0.25%, tensile elongation 0.08%, product mechanical properties: yield strength 401MPa, tensile strength 634MPa, elongation 28.0%, n-value 0.21.

[0017] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0018] The high-elongation 590MPa grade galvanized duplex steel strip of this invention possesses high strength and high formability, making it suitable for relatively complex forming structures and meeting the safety, low energy consumption, and complex forming requirements of the automotive industry. Yield strength R p0.2 340~440MPa, tensile strength R m 590~700MPa, elongation A 50 ≥27%, strain hardening index n value ≥0.16. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings.

[0020] Figure 1 This is a microstructure diagram of an embodiment of the present invention. Detailed Implementation

[0021] The present invention will be described in detail below through specific embodiments. These embodiments are only intended to help understand the present invention and do not limit the scope of the present invention.

[0022] Example

[0023] According to the above steelmaking process requirements, the actual chemical composition of the slab is shown in Table 1.

[0024] Table 1 Chemical composition (wt%) of embodiments of the present invention

[0025]

[0026]

[0027] According to the above hot rolling process requirements, the hot rolling thickness is 3.5 to 4.5 mm, and the actual process is shown in Table 2.

[0028] Table 2 Hot rolling process of embodiments of the present invention

[0029]

[0030]

[0031] According to the above requirements for cold rolling, hot-dip galvanizing, and finishing processes, the cold rolling thickness is 1.2 to 2.2 mm, and the actual hot-dip galvanizing and finishing processes are shown in Table 3.

[0032] Table 3 Hot-dip galvanizing and finishing processes of embodiments of the present invention

[0033]

[0034]

[0035] The mechanical properties of the steel strip in this embodiment of the invention were tested, and the test results are shown in Table 4.

[0036] Table 4 Mechanical properties of steel strip in embodiments of the present invention

[0037]

[0038] As shown in Table 4, the mechanical properties of the high elongation 590MPa grade galvanized duplex steel strip of this invention are as follows: Yield strength R p0.2 369~421MPa, tensile strength R m 634~651MPa, elongation A 50 The percentage of the steel strip produced by this process is 28.0%–34.0%, with an n-value of 0.21–0.24. Based on the above analysis, the steel strip products obtained through this process have shown suitable performance after user testing and are suitable for widespread application.

[0039] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for producing a high-elongation 590MPa grade galvanized duplex steel strip, characterized in that: include: (1) Smelting-continuous casting production process: hot metal pretreatment—converter—LF refining—RH refining—slab continuous casting; In the converter top and bottom combined blowing smelting, oxygen blowing is used for decarburization and temperature rise. During the converter tapping process, aluminum ferromanganese, ferrosilicon and other materials are added for deoxidation and alloying. The P and S composition is controlled to prevent the steel liquid from over-oxidizing. The tapping temperature is ≥1600℃. The LF ladle refining adopts the LF full-process argon blowing process. The RH refining vacuum degree is ≤2.6mbar and the vacuum time is ≥10min. The composition is adjusted to the target composition according to the steel composition. The steel composition supplied to the casting machine by mass percentage is C: 0.10~0.15%, Si: ≤0.45%, Mn: 1.45~1.70%, P≤0.020%, S≤0.010%, Alt: 0.40~0.60%, Ti≤0.025%, Ca: 0.0008~0.0020%, and the remainder is Fe and unavoidable impurities. The superheating temperature of the above slab continuous casting is 15-40℃, and the casting speed is controlled at 0.8-1.5m / min; (2) Hot rolling production process: billet heating—rough rolling—finish rolling—coiling; the billet is in the furnace for 170-230 minutes, the furnace exit temperature is 1210-1280℃, the rough rolling adopts a 3+3 mode 2-stand rolling mill, the finish rolling adopts a 7-stand rolling mill, the finish rolling start temperature is 970-1050℃, the finish rolling end temperature is 860-910℃, and the hot rolled steel strip thickness is 2.5-5.0mm; the cooling adopts laminar flow cooling equipment, and the coiling temperature is 530-590℃; (3) Pickling and cold rolling process: After the hot-rolled steel strip is pickled to remove the surface iron oxide scale, it is cold rolled by a 5-stand cold rolling mill with a cold rolling reduction rate of 50-70% and a thickness of 0.7-2.5mm. (4) Continuous hot-dip galvanizing and finishing process: After uncoiling the cold-hardened steel strip, continuous welding is carried out. The furnace speed is 60-130 m / min, the soaking temperature is 790-840℃, the slow cooling is 670-710℃, and then the cooling is 440-470℃. The temperature of entering the zinc pot is 440-480℃, the temperature of the top roller cooling tower is 200-240℃, the finishing elongation is 0.2%-0.5%, and the tension leveling elongation is ≤0.2%.

2. The method for producing high elongation 590MPa grade galvanized duplex steel strip according to claim 1, characterized in that: The percentage chemical composition of the galvanized duplex steel strip is C: 0.12-0.14%, Si: 0.31-0.43%, Mn: 1.55-1.64%, P: 0.015-0.018%, S: 0.001-0.005%, Alt: 0.43-0.58%, Ti: 0.016-0.022%, Ca: 0.0011-0.0020%, with the remainder being Fe and unavoidable impurities.

3. The method for producing high elongation 590MPa grade galvanized duplex steel strip according to claim 1, characterized in that: The chemical composition of the galvanized duplex steel strip is as follows: C: 0.14%, Si: 0.35%, Mn: 1.61%, P: 0.015%, S: 0.002%, Alt: 0.45%, Ti: 0.016%, Ca: 0.0011%, with the remainder being Fe and unavoidable impurities. Hot-rolled raw material thickness 3.5mm, furnace time 198min, furnace exit temperature 1226℃, finishing rolling start temperature 999℃, finishing rolling temperature 888℃, coiling temperature 585℃; cold-rolled thickness 1.2mm, speed 95m / min, soaking temperature 826℃, slow cooling temperature 705℃, rapid cooling temperature 455℃, zinc pot temperature 464℃, cooling tower temperature 205℃, finished elongation 0.24%, tensile elongation 0.11%, product mechanical properties: yield strength 369MPa, tensile strength 650MPa, elongation 34.0%, n-value 0.

24.

4. The method for producing high elongation 590MPa grade galvanized duplex steel strip according to claim 1, characterized in that: The chemical composition of the galvanized duplex steel strip is as follows: C: 0.14%, Si: 0.31%, Mn: 1.64%, P: 0.017%, S: 0.001%, Alt: 0.43%, Ti: 0.022%, Ca: 0.0020%, with the remainder being Fe and unavoidable impurities. Hot-rolled raw material thickness 3.8mm, furnace time 193min, furnace exit temperature 1245℃, finishing rolling start temperature 985℃, finishing rolling temperature 895℃, coiling temperature 581℃; cold-rolled thickness 1.5mm, speed 86m / min, soaking temperature 819℃, slow cooling temperature 699℃, rapid cooling temperature 449℃, zinc pot temperature 466℃, cooling tower temperature 211℃, finished elongation 0.22%, tensile elongation 0.15%, product mechanical properties: yield strength 374MPa, tensile strength 651MPa, elongation 33.0%, n-value 0.

23.

5. The method for producing high elongation 590MPa grade galvanized duplex steel strip according to claim 1, characterized in that: The chemical composition of the galvanized duplex steel strip is as follows: C: 0.12%, Si: 0.43%, Mn: 1.59%, P: 0.016%, S: 0.005%, Alt: 0.58%, Ti: 0.020%, Ca: 0.0011%, with the remainder being Fe and unavoidable impurities. Hot-rolled raw material thickness 4.3mm, furnace time 202min, furnace exit temperature 1255℃, finishing rolling start temperature 1003℃, finishing rolling temperature 885℃, coiling temperature 563℃; cold-rolled thickness 1.8mm, speed 72m / min, soaking temperature 802℃, slow cooling temperature 685℃, rapid cooling temperature 461℃, zinc pot entry temperature 468℃, cooling tower temperature 220℃, finished elongation 0.40%, tensile elongation 0.19%, product mechanical properties: yield strength 421MPa, tensile strength 635MPa, elongation 29.5%, n-value 0.

22.

6. The method for producing high elongation 590MPa grade galvanized duplex steel strip according to claim 1, characterized in that: The chemical composition of the galvanized duplex steel strip is as follows: C: 0.13%, Si: 0.41%, Mn: 1.55%, P: 0.018%, S: 0.004%, Alt: 0.53%, Ti: 0.018%, Ca: 0.0018%, with the remainder being Fe and unavoidable impurities. Hot-rolled raw material thickness 4.5mm, furnace time 226min, furnace exit temperature 1256℃, finishing rolling start temperature 1011℃, finishing rolling temperature 872℃, coiling temperature 552℃; cold-rolled thickness 2.0mm, speed 66m / min, soaking temperature 811℃, slow cooling temperature 680℃, rapid cooling temperature 470℃, zinc pot entry temperature 472℃, cooling tower temperature 236℃, finished elongation 0.31%, tensile elongation 0.13%, product mechanical properties: yield strength 420MPa, tensile strength 644MPa, elongation 28.5%, n-value 0.

22.

7. The method for producing high elongation 590MPa grade galvanized duplex steel strip according to claim 1, characterized in that: The chemical composition of the galvanized duplex steel strip is as follows: C: 0.12%, Si: 0.43%, Mn: 1.59%, P: 0.016%, S: 0.005%, Alt: 0.58%, Ti: 0.020%, Ca: 0.0011%, with the remainder being Fe and unavoidable impurities. Hot-rolled raw material thickness 4.5mm, furnace time 228min, furnace exit temperature 1250℃, finishing rolling start temperature 1023℃, finishing rolling temperature 872℃, coiling temperature 557℃; cold-rolled thickness 2.2mm, speed 63m / min, soaking temperature 794℃, slow cooling temperature 680℃, rapid cooling temperature 466℃, zinc pot temperature 478℃, cooling tower temperature 233℃, finished elongation 0.25%, tensile elongation 0.08%, product mechanical properties: yield strength 401MPa, tensile strength 634MPa, elongation 28.0%, n-value 0.21.

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