Production method of 260MPa-grade galvanized low-alloy high-strength steel strip with high formability, aging resistance and low cost

Abstract

The invention discloses a production method of a galvanized low-alloy high-strength steel strip with high formability, aging resistance, low alloy cost and yield strength of 260 MPa for an automobile. The production method comprises the following steps: (1) smelting-continuous casting production process flow; (2) hot rolling production process flow; (3) pickling and cold rolling process flow; and (4) continuous hot galvanizing and finishing process flow. The aluminum alloy material comprises the following chemical components in percentage by mass: 0.05 to 0.09 percent of C, less than or equal to 0.08 percent of S , 0.10 to 0.40 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S, 0.015 to 0.050 percent of Alt, 0.0005 to 0.0030 percent of Ca and less than or equal to 0.0070 percent of N. The galvanized low-alloy high-strength steel with the yield strength of 260 MPa has high formability, good aging resistance and low alloy cost, and is suitable for automobile structural parts with high formability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steel, and particularly relates to a production method of a 260MPa-grade galvanized low-alloy high-strength steel strip with high formability, aging resistance and low cost. BACKGROUND

[0002] With the popularization of automobile lightening, the development of high-strength steel is increasingly valued. The galvanized low-alloy high-strength steel is widely used in the manufacture of automobile structural parts due to its outstanding mechanical property matching, good welding performance and cold forming performance. The application of the galvanized low-alloy high-strength steel can realize automobile weight reduction and energy saving and emission reduction, conform to the policy guidance of the country, and has a good market promotion and application prospect. The 260MPa-grade galvanized low-alloy high-strength steel is the lowest strength grade product in the series of products, but is still one of the main selection products of automobile structural materials with a larger market demand. For the structural parts with relatively complex formability and relatively low strength requirement, the 260MPa-grade galvanized low-alloy high-strength steel is a better material selection in terms of machinability, applicability and economy.

[0003] The 260-330MPa-grade low-alloy high-strength steel developed by Tangsteel (patent name: production method of 260-330MPa-grade low-alloy high-strength steel, application publication number CN 104928576) and the product of the present application are both 260MPa-grade low-alloy high-strength steel, the main production process of the product of Tangsteel is covering and annealing + skin passing, and the present application is continuous hot galvanizing annealing + skin passing; the main strengthening elements of the product of Tangsteel are C+Mn (0.60%) / C+Mn+Nb / C+Mn+Ti / C+Mn+Nb+Ti, and the main strengthening elements of the product of the present application are C+Mn (0.10-0.40%), the present application has certain alloy cost advantage, and in addition, the hot rolling final rolling temperature, cold rolling reduction, annealing temperature and skin passing machine elongation are also different.

[0004] The low-cost 260MPa-grade automobile steel developed by Tangsteel (patent name: low-cost 260MPa-grade automobile steel and production method thereof, application publication number CN 104726766 A) and the product of the present application are both 260MPa-grade low-alloy high-strength steel, the main production process of the product of Tangsteel is covering and annealing + skin passing, and the present application is continuous hot galvanizing annealing + skin passing; the main strengthening elements of the product of Tangsteel are C+Mn (0.30-0.60%), and the main strengthening elements of the product of the present application are C+Mn (0.10-0.40%), the Mn content in the product of Tangsteel is 0.30-0.60% in the product examples, the Mn content in the product examples of the present application is 0.25-0.29%, the present application has certain alloy cost advantage. In addition, the hot rolling final rolling temperature, cold rolling reduction, annealing temperature and skin passing machine elongation are also different.

[0005] The low-cost 260MPa grade low-alloy high-strength steel developed by Shougang Jingtang (patent name: a low-cost 260MPa grade low-alloy high-strength steel and a preparation method, application publication number CN 119776723 A) and the product of the present application are both 260MPa grade low-alloy high-strength steel, and the main strengthening elements of the Tanggang product are C (0.07-0.11%) + Mn (0.30-0.50%), and the main strengthening elements of the product of the present application are C (0.05-0.09) + Mn (0.10-0.40%), the C content in the product of Tanggang is 0.74-0.11%, and the Mn content is 0.33-0.47%, the C content in the product of the present application is 0.70%, and the Mn content is 0.25-0.29%, the product of the present application has certain alloy cost advantage and relatively low C and Mn content, so that the stamping performance of the product can be improved. In addition, the hot rolling coiling temperature and the elongation of the temper mill also have obvious differences. SUMMARY

[0006] The purpose of the present application is to provide a production method of a high-formability, aging-resistant, low-cost 260MPa grade galvanized low-alloy high-strength steel strip, the 260MPa grade galvanized low-alloy high-strength steel of the present application has high formability, good aging resistance and low alloy cost, and is suitable for automobile structural parts with high formability. The mechanical properties meet: yield strength R eL : 260-330MPa, tensile strength R m : 350-430MPa, elongation A 80mm ≥ 26%.

[0007] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0008] The present application is a production method of a high-formability, aging-resistant, low-cost 260MPa grade galvanized low-alloy high-strength steel strip, which comprises:

[0009] (1) Smelting-continuous casting production process: hot metal pretreatment-converter-LF refining-slab continuous casting; hot metal needs to be treated by KR desulphurization, and the requirement is that the sulfur content of the hot metal entering the converter is less than or equal to 0.010%, and the desulphurization slag cleaning area is greater than 90%; oxygen blowing decarburization and temperature rising are carried out in the converter top and bottom combined blowing smelting, aluminum iron, manganese iron and other alloys are added during the converter tapping process 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 greater than or equal to 1620℃; LF furnace slagging desulphurization is carried out, and aluminum iron, manganese iron and other alloys are added to adjust to the target component range; the percentage of the components of the molten steel for the caster is C: 0.05-0.09%, Si: less than or equal to 0.08%, Mn: 0.10-0.40%, P: less than or equal to 0.020%, S: less than or equal to 0.010%, Alt: 0.015-0.050%, Ca: 0.0005-0.0030%, and the rest is Fe and impurities; the slab continuous casting superheat is 25-40℃, and the withdrawal speed is controlled at 1.0-1.8m / min;

[0010] (2) Hot rolling production process: casting blank heating-rough rolling-finish rolling-coiling; the casting blank tapping temperature is 1180-1240℃, the rough rolling adopts a 3+3 mode 2 rack rolling mill for rough rolling, the finish rolling adopts a 7 rack rolling mill for finish rolling, the finish rolling final rolling temperature is 860-920℃, and the hot rolled steel strip thickness is 2.50-3.90mm; the cooling adopts laminar flow cooling equipment, and the coiling temperature is 600-670℃;

[0011] (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 a 5 rack cold rolling mill, the cold rolling reduction rate is 72-80%, and the finished product thickness is 0.50-1.00mm;

[0012] (4) Continuous hot galvanizing and finishing process: the cold hard steel strip is unwound and welded for continuous production, the furnace area speed is 70-120m / min, the soaking temperature is 750-830℃, the slow cooling is to 630-690℃, then the cooling is to 430-490℃, the zinc pot temperature is 440-480℃, and the finishing elongation is 0.90-1.20%.

[0013] Further, the chemical component content of the galvanized low alloy high strength steel strip is: C: 0.05-0.09%, Si less than or equal to 0.08%, Mn: 0.10-0.40%, P less than or equal to 0.020%, S less than or equal to 0.010%, Alt: 0.015-0.050%, Ca: 0.0005-0.0030%, N less than or equal to 0.0070%, and the rest is Fe and impurities.

[0014] Further, the galvanized low-alloy high-strength steel strip has the following chemical composition in percentage by mass: C: 0.07%, Si 0.02%, Mn: 0.25%, P 0.012%, S 0.002%, Alt: 0.032%, Ca: 0.0023%, N 0.0040%, and the rest is Fe and impurities.

[0015] Further, the galvanized low-alloy high-strength steel strip has the following chemical composition in percentage by mass: C: 0.07%, Si 0.02%, Mn: 0.29%, P 0.012%, S 0.003%, Alt: 0.028%, Ca: 0.0008%, N 0.0041%, and the rest is Fe and impurities.

[0016] Further, the galvanized low-alloy high-strength steel strip has the following mechanical properties: yield strength R el : 289-295 MPa, tensile strength R m : 375-387 MPa, and elongation A 80mm : 35.0-37.5%.

[0017] Further, the galvanized low-alloy high-strength steel strip has good stamping performance and relatively low alloy cost.

[0018] Compared with the prior art, the present application has the following beneficial technical effects:

[0019] The present application provides a high-formability, aging-resistant, low-alloy-cost, 260 MPa-grade galvanized low-alloy high-strength steel strip for automobiles and a production method thereof. The present application adopts low-carbon, low-manganese component design, slightly high coiling temperature and annealing temperature design to make the product have slightly high strength, good stamping performance and relatively low alloy cost. The slightly high elongation design of the finishing machine makes the product have certain aging resistance, and the surface quality of the stamped parts is good, which meets the material selection requirements of automobile enterprises for slightly high strength and slightly high deformation structure parts. The mechanical properties meet the following requirements: yield strength R eL : 260-330 MPa, tensile strength R m : 350-430 MPa, and elongation A 80mm : ≥26%. BRIEF DESCRIPTION OF DRAWINGS

[0020] The present application will be further described below in combination with the drawings.

[0021] Figure 1 is a microstructure diagram of Example 2.2;

[0022] Figure 2 is an automobile structure produced by Example 2.2. DETAILED DESCRIPTION

[0023] 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.

[0024] According to the above steelmaking process requirements, the actual chemical composition of the slab is shown in Table 1.

[0025] Table 1 Chemical composition (wt%) of embodiments of the present invention

[0026]

[0027] According to the above hot rolling process requirements, the actual process is shown in Table 2.

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

[0029] Serial number Discharge temperature / °C Finish rolling temperature / °C Coiling temperature / °C Requirement 1180-1240 860-920 600-670 Example 1.1 1223 891 614 Example 1.2 1222 892 617 Example 2.1 1191 891 611 Example 2.2 1204 890 611 Example 2.3 1203 890 608 Example 2.4 1198 894 614

[0030] Based on the above requirements for cold rolling, hot-dip galvanizing, and finishing processes, the actual hot-dip galvanizing and finishing processes are shown in Table 3.

[0031] Table 3 Hot-dip galvanizing and finishing processes of embodiments of the present invention

[0032]

[0033]

[0034] The mechanical properties of the steel strip in this embodiment of the invention were tested, and the test results are shown in Table 4.

[0035] Table 4 Mechanical properties of steel strip in embodiments of the present invention

[0036] Example yield strength R eL / MPa Tensile strength R m / MPa Elongation A 80 / %]] Requirement ≥390 ≥460 ≥16 Example 1.1 292 375 35.5 Example 1.2 295 382 35.0 Example 2.1 290 385 37.0 Example 2.2 295 387 37.5 Example 2.3 289 381 37.5 Example 2.4 291 383 37.5

[0037] As shown in Table 4, the mechanical properties of the galvanized low-alloy high-strength steel strip for automobiles, characterized by high formability, aging resistance, low alloy cost, and a yield strength of 260 MPa, are as follows: Yield strength R... el 289-295MPa, tensile strength R m 375-387MPa, elongation A 80mm The steel strip product obtained by the above process has been tested by users and found to have suitable performance, and can be promoted for use.

[0038] 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 formability, age-tolerant, low cost 260 MPa grade zinc-coated low alloy high strength steel strip, characterized in that, It comprises: (1) smelting-continuous casting production process: hot metal pretreatment-converter-LF refining-slab continuous casting; The hot metal needs to be treated by KR desulfurization, and the sulfur content of the hot metal entering the converter is required to be ≤0.010%, and the desulfurization slag cleaning area is greater than 90%; oxygen blowing decarburization and temperature rising are carried out in the top and bottom combined blowing smelting of the converter, aluminum iron, manganese iron and the like are added during the tapping process of the converter for deoxidization and alloying, the P and S components are controlled, and the steel liquid is prevented from being over-oxidized, and the tapping temperature is ≥1620℃; the LF furnace is slagging and desulfurizing, and aluminum iron, manganese iron and the like are added to adjust to the target component range; the steel liquid quality percentage components for the casting machine are C: 0.05-0.09%, Si: ≤0.08%, Mn: 0.10-0.40%, P: ≤0.020%, S: ≤0.010%, Alt: 0.015-0.050%, Ca: 0.0005-0.0030%, and the rest is Fe and impurities; the slab continuous casting superheat is 25-40℃, and the drawing speed is controlled at 1.0-1.8m / min; (2) hot rolling production process: casting blank heating-rough rolling-finish rolling-coiling; the casting blank out-of-furnace temperature is 1180-1240℃, the rough rolling adopts a 3+3 mode 2-rack rolling mill for rough rolling, the finish rolling adopts a 7-rack rolling mill for finish rolling, the finish rolling final rolling temperature is 860-920℃, and the hot rolled steel strip thickness is 2.50-3.90mm; the cooling adopts laminar flow cooling equipment, and the coiling temperature is 600-670℃; (3) pickling and cold rolling process: after the hot rolled steel strip is subjected to pickling to remove the surface iron oxide scale, the hot rolled steel strip is subjected to cold rolling through a 5-rack cold rolling mill, the cold rolling reduction rate is 72-80%, and the finished product thickness is 0.50-1.00mm; (4) continuous hot galvanizing and finishing process: after the cold hard steel strip is unwound and welded for continuous production, the furnace area speed is 70-120m / min, the soaking temperature is 750-830℃, the slow cooling is to 630-690℃, then the cooling is to 430-490℃, the zinc pot temperature is 440-480℃, and the finishing elongation is 0.90-1.20%.

2. The method of producing a high-formability, age-tolerant, low-cost 260 MPa grade galvannealed low alloy high strength steel strip according to claim 1, characterized in that, The mass percentage content of the chemical components of the galvanized low-alloy high-strength steel strip is: C: 0.05-0.09%, Si ≤0.08%, Mn: 0.10-0.40%, P ≤0.020%, S ≤0.010%, Alt: 0.015-0.050%, Ca: 0.0005-0.0030%, N ≤0.0070%, and the rest is Fe and impurities.

3. The method of producing a high-formability, age-tolerant, low-cost 260 MPa grade galvannealed low alloy high strength steel strip according to claim 2, characterized in that, The mass percentage content of the chemical components of the galvanized low-alloy high-strength steel strip is: C: 0.07%, Si 0.02%, Mn: 0.25%, P 0.012%, S 0.002%, Alt: 0.032%, Ca: 0.0023%, N 0.0040%, and the rest is Fe and impurities.

4. The method of producing a high-formability, age-tolerant, low-cost 260 MPa grade galvannealed high-strength low-alloy steel strip according to claim 2, characterized in that, The mass percentage content of the chemical components of the galvanized low-alloy high-strength steel strip is: C: 0.07%, Si 0.02%, Mn: 0.29%, P 0.012%, S 0.003%, Alt: 0.028%, Ca: 0.0008%, N 0.0041%, and the rest is Fe and impurities.

5. The method of producing a high-formability, age-tolerant, low-cost 260 MPa grade galvannealed low alloy high strength steel strip according to claim 4, characterized in that, The mechanical properties of the galvanized low-alloy high-strength steel strip satisfy: yield strength R el : 289-295 MPa, tensile strength R m : 375-387 MPa.

6. The method of producing a high-formability, age-tolerant, low-cost 260 MPa grade galvannealed low alloy high strength steel strip according to claim 4, characterized in that, The mechanical properties of the galvanized low-alloy high-strength steel strip satisfy: elongation A 80mm : 35.0-37.5%.

7. The method of producing a high-formability, age-tolerant, low-cost 260 MPa grade zinc- galvanized low alloy high strength steel strip according to claim 1, characterized in that, The galvanized low-alloy high-strength steel strip has good stamping performance and relatively low alloy cost.

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