Manufacturing method of hot-dip galvanizing ultra-deep drawing automobile steel DX56D + Z suitable for new automobile types

Abstract

The invention discloses a manufacturing method of hot-dip galvanizing ultra-deep drawing automobile steel DX56D + Z suitable for a new automobile model. The manufacturing method comprises the following steps: a smelting-continuous casting production process; a hot rolling production process: pickling and rolling; a galvanization process; the mass percentage content of the chemical components is as follows: C is less than or equal to 0.0025%; s is less than or equal to 0.01%; 0.20% or less of Mn; less than or equal to 0.015% of P; s is less than or equal to 0.010%; 0.040 < = T < = 0.070%; n is less than or equal to 0.0030%; and O < = 0.0030%. Stamped car door inner plates, side walls and other car parts prepared from the hot-galvanized ultra-deep-drawing car steel DX56D + Z are free of cracking and wrinkling problems, the stamping effect is good, and the mechanical properties of strip steel meet the conditions that the yield strength Rp0.2 is larger than or equal to 140 and smaller than or equal to 180 MPa, the tensile strength Rm is larger than or equal to 270 MPa, the yield ratio is smaller than or equal to 0.60, the ductility A80 is larger than or equal to 39%, r90 is larger than or equal to 2.5, and n90 is larger than or equal to 0.21.

Description

Technical Field

[0001] The invention belongs to the technical field of steel metallurgy and steelmaking technology, and in particular relates to a method for manufacturing hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z suitable for new models. Background Art

[0002] Steel plates are needed in automobile technology. Ultra-low carbon steel plates with high stamping performance are favored by automobile companies. In order to meet people's requirements for lightweight, safe and environmentally friendly automobiles, it is particularly important to choose thin steel plates with good performance. Among them, hot-dip galvanized thin steel plates are widely used in the automotive field because of their low cost and high corrosion resistance. They can reduce body defects, improve automobile performance, and beautify surface appearance.

[0003] A certain car factory directly supplied the new model with hot-dip galvanized ultra-deep-drawing automobile steel DX56D+Z, which had cracking and wrinkling problems. According to production experience, the main problem was that the material was too soft and unsuitable. Through process optimization, without increasing production costs, the present invention provides a manufacturing method for hot-dip galvanized ultra-deep-drawing automobile steel DX56D+Z suitable for new models, and obtains an ultra-deep-drawing automobile steel plate with high strength and excellent comprehensive performance. The products produced by this method have suitable performance after being used by users, and there are no cracking and wrinkling problems on stamped door inner panels, side panels and other automobile parts, and the stamping effect is good. Summary of the invention

[0004] The purpose of the present invention is to provide a method for manufacturing hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z suitable for new models, which can stamp automobile parts such as door inner panels and side panels without cracking and wrinkling, and achieve good stamping effect. The mechanical properties of the strip steel meet the following requirements: yield strength 140≤R p0.2 ≤180MPa, tensile strength R m ≥270MPa, yield strength ratio ≤0.60, elongation A 80 ≥39%, r 90 ≥2.5, n 90 ≥0.21.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The present invention discloses a method for manufacturing hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z suitable for new vehicle models, comprising:

[0007] Smelting-continuous casting production process: KR desulfurization-converter-RH furnace-slab continuous casting; the sulfur content of the molten iron entering the converter is required to be less than 0.005%, and the slag removal area of ​​the molten iron is required to be greater than 95%; deep decarburization treatment is carried out according to the composition and temperature of the molten steel supplied by the converter to RH; after decarburization, aluminum particles are added for deoxidation and alloying according to the oxygen fixation situation, and ferromanganese and ferrotitanium are added after circulating for more than 4 minutes to adjust the composition; after the composition adjustment is completed, ensure that the vacuum cycle is ≥6 minutes; the slab continuous casting superheat is 25-40℃, and the pulling speed is controlled at 1.0-1.8m / min;

[0008] (2) Hot rolling production process: billet heating - rough rolling - finishing rolling - coiling; billet heating temperature is 1170-1220℃, furnace temperature is 1170-1220℃, rough rolling adopts 3+3 mode 2-stand rolling mill, finishing rolling adopts 7-stand rolling mill, finishing rolling temperature is 880-930℃, hot rolled steel strip thickness is 3.5mm; cooling adopts laminar cooling equipment, coiling temperature is 670-730℃; key hot rolling process technologies are shown in the following table:

[0009]

[0010] The pickling process includes: pickling uncoiling - welding - straightening - pickling - rinsing - drying - trimming - cold rolling on a continuous rolling mill - slitting - coiling; the process flow is: the hot-rolled steel strip is pickled to remove the surface iron oxide scale, and then cold-rolled on a 5-stand cold rolling mill, with a cold rolling reduction rate of 70-85% and a thickness of 0.7mm;

[0011] The galvanizing process includes: hot-dip galvanizing uncoiling → welding → entrance looper → cleaning → annealing furnace → zinc pot → cooling after plating → water quenching → intermediate looper → skin pass machine → straightening machine → roller coater → dryer → air cooling device → exit looper → trimming → surface inspection → oiling → sampling → coiling → bundling and weighing → packaging → storage; the process flow is: uncoiling the cold hardened steel strip and welding it for continuous production, the furnace speed is 90-120m / min, the soaking temperature is 750-810℃, and the elongation of the skin pass machine is 0.8-0.9%;

[0012] The specific process system of the galvanizing process is shown in the following table:

[0013]

[0014] The chemical composition of the hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z has the following mass percentages: C≤0.0025%; Si≤0.01%; Mn≤0.20%; P≤0.015%; S≤0.010%; 0.040≤Ti≤0.070%; N≤0.0030%; O≤0.0030%, and the rest is Fe and unavoidable impurities.

[0015] Furthermore, the chemical composition of the hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z has the following mass percentages: C 0.0020%, Si 0.005%, Mn 0.15%, P 0.010%, S 0.007%, Ti 0.060%, N 0.0018%, O 0.0015%, and the rest is Fe and unavoidable impurities.

[0016] Furthermore, the mechanical properties of the hot-dip galvanized ultra-deep drawing automotive steel DX56D+Z meet the following requirements: yield strength 140≤R p0.2 ≤180MPa, tensile strength R m ≥270MPa, yield strength ratio ≤0.60.

[0017] Furthermore, the mechanical properties of the hot-dip galvanized ultra-deep drawing automotive steel DX56D+Z meet the following requirements: elongation A 80 ≥39%.

[0018] Furthermore, the mechanical properties of the hot-dip galvanized ultra-deep drawing automotive steel DX56D+Z meet the following requirements: 90 ≥2.5, n 90 ≥0.21.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are:

[0020] The present invention provides a method for manufacturing hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z suitable for new models. There is no cracking or wrinkling problem when stamping automobile parts such as door inner panels and side panels, and the stamping effect is good. The mechanical properties of the strip steel meet the following requirements: yield strength 140≤R p0.2 ≤180MPa, tensile strength R m ≥270MPa, yield strength ratio ≤0.60, elongation A 80 ≥39%, r 90 ≥2.5, n 90 ≥0.21. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below in conjunction with the accompanying drawings.

[0022] Figure 1 A microstructure diagram of an embodiment of the present invention;

[0023] Figure 2 This is a diagram of an application example of an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The present invention is described in detail below through specific examples. The examples are only intended to help understand the present invention but are not intended to limit the present invention.

[0025] Example

[0026] According to the above steelmaking process requirements, the actual slab chemical composition (mass percentage) is shown in Table 1 below.

[0027] Table 1: Chemical composition (%)

[0028]

[0029] According to the above hot rolling process requirements, the hot rolling thickness is 3.5 mm, and the actual process is shown in Table 2.

[0030] Table 2: Rolling process

[0031] Hot rolled thickness(mm) Finish rolling temperature (℃) Coiling temperature(℃) 3.5 890～920 685～715

[0032] According to the above galvanizing process requirements, the strip thickness is 0.7mm, and the actual processes of annealing, galvanizing and flattening are shown in Table 3.

[0033] Table 3: Galvanizing process

[0034]

[0035] The mechanical properties of the steel strip products obtained through the above process are shown in Table 4, and the test method refers to GB / T228.1.

[0036] Table 4: Mechanical properties

[0037]

[0038] From the data in Table 4, it can be seen that the mechanical properties of the hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z suitable for new models of vehicles of the present invention meet the following requirements: yield strength 140≤R p0.2 ≤180MPa, tensile strength R m ≥270MPa, yield strength ratio ≤0.60, elongation A 80 ≥39%, r 90 ≥2.5, n 90 ≥0.21. In summary, the process has obtained an ultra-deep drawn automobile steel plate with high strength and excellent comprehensive performance. The products produced by this method have been used by users and have suitable performance. There is no cracking or wrinkling problem in stamping automobile parts such as door inner panels and side panels, and the stamping effect is good. It can be extended to other parts of new models and other deep drawn automobile steels for reference.

[0039] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for manufacturing hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z suitable for new models, characterized in that: include: Smelting-continuous casting production process: KR desulfurization-converter-RH furnace-slab continuous casting; The sulfur content of the molten iron entering the converter is required to be less than 0.005%, and the slag removal area of ​​the molten iron is required to be greater than 95%; deep decarburization treatment is carried out according to the composition and temperature of the RH molten steel supplied by the converter; after decarburization, aluminum particles are added for deoxidation and alloying according to the oxygen fixation situation, and ferromanganese and ferrotitanium are added after the cycle for more than 4 minutes to adjust the composition; after the composition adjustment is completed, ensure that the vacuum cycle is ≥6 minutes; the slab continuous casting superheat is 25-40℃, and the pulling speed is controlled at 1.0-1.8m / min; (2) Hot rolling production process: billet heating - rough rolling - finishing rolling - coiling; billet heating temperature is 1170-1220℃, furnace temperature is 1170-1220℃, rough rolling adopts 3+3 mode 2-stand rolling mill, finishing rolling adopts 7-stand rolling mill, finishing rolling temperature is 880-930℃, hot rolled steel strip thickness is 3.5mm; cooling adopts laminar cooling equipment, coiling temperature is 670-730℃; key hot rolling process technologies are shown in the following table: The pickling process includes: pickling uncoiling - welding - straightening - pickling - rinsing - drying - trimming - cold rolling on a continuous rolling mill - slitting - coiling; the process flow is: the hot-rolled steel strip is pickled to remove the surface iron oxide scale, and then cold-rolled on a 5-stand cold rolling mill, with a cold rolling reduction rate of 70-85% and a thickness of 0.7mm; The galvanizing process includes: hot-dip galvanizing uncoiling → welding → entrance looper → cleaning → annealing furnace → zinc pot → cooling after plating → water quenching → intermediate looper → skin pass machine → straightening machine → roller coater → dryer → air cooling device → exit looper → trimming → surface inspection → oiling → sampling → coiling → bundling and weighing → packaging → storage; the process flow is: uncoiling the cold hardened steel strip and welding it for continuous production, the furnace speed is 90-120m / min, the soaking temperature is 750-810℃, and the elongation of the skin pass machine is 0.8-0.9%; The specific process system of the galvanizing process is shown in the following table: The chemical composition of the hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z has the following mass percentages: C≤0.0025%; Si≤0.01%; Mn≤0.20%; P≤0.015%; S≤0.010%; 0.040≤Ti≤0.070%; N≤0.0030%; O≤0.0030%, and the rest is Fe and unavoidable impurities.

2. The method for manufacturing the hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z for new vehicle models according to claim 1, characterized in that: The chemical composition of the hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z is as follows: C 0.0020%, Si 0.005%, Mn 0.15%, P 0.010%, S 0.007%, Ti 0.060%, N 0.0018%, O 0.0015%, and the rest is Fe and unavoidable impurities.

3. The method for manufacturing the hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z for new vehicle models according to claim 1, characterized in that: The mechanical properties of the hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z meet the following requirements: yield strength 140≤R p0.2 ≤180MPa, tensile strength R m ≥270MPa, yield strength ratio ≤0.

60.

4. The method for manufacturing the hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z for new vehicle models according to claim 1, characterized in that: The mechanical properties of the hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z meet the following requirements: elongation A 80 ≥39%.

5. The method for manufacturing the hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z for new vehicle models according to claim 1, characterized in that: The mechanical properties of the hot-dip galvanized ultra-deep drawing automobile steel DX56D+Z meet the following requirements: 90 ≥2.5, n 90 ≥0.21.

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