Production method of steel for hot-dip galvanized automobile door inner plate

Abstract

The invention discloses a production method of hot-dip galvanized steel for an inner plate of an automobile door. The production method comprises a smelting-continuous casting production process flow, the hot rolling production process comprises the steps of casting blank heating, rough rolling, finish rolling and coiling; pickling and rolling; a galvanization process; wherein the molten steel for the casting machine comprises the following chemical components in percentage by mass: less than or equal to 0.0020% of C; s is less than or equal to 0.01%; 0.20% or less of Mn; less than or equal to 0.010% of P; s is less than or equal to 0.012%; 0.055 < = T < = 0.075%; n is less than or equal to 0.0030%; 0 < = 0.0030%, with the balance being iron and impurities. Products produced through the method are suitable in performance after being used by users, and the stamping effect of stamping the automobile door inner plate is good. The mechanical properties of the strip steel meet the following conditions: the yield strength Rp0.2 is more than or equal to 120 and less than or equal to 180 MPa, the tensile strength Rm is more than or equal to 260 and less than or equal to 350 MPa, the yield ratio is less than or equal to 0.60, the ductility A80 is more than or equal to 41%, the r90 is more than or equal to 2.6, and the n90 is more than or equal to 0.21.

Description

Technical Field

[0001] The invention belongs to the technical field of hot-dip galvanized ultra-deep drawing steel, and in particular relates to a production method of hot-dip galvanized steel for automobile door inner panels. 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] As a key covering part, the inner door panel has the characteristics of large size, complex structure, and deep forming depth, which will increase the difficulty of its forming. The draft angle of the side wall of the door inner panel is generally small, and the secondary step structure around it increases the resistance of the sheet inflow during the drawing process, resulting in defects such as cracking and wrinkling. The part forming depth is also large. Generally speaking, the difficulty of forming the door inner panel is relatively large. The present invention discloses a manufacturing method of a hot-dip galvanized stamping product with high elongation and r-value. The product is suitable for stamping the inner door panel of a certain car factory. The product produced by this method has been used by users and has suitable performance and good stamping effect for stamping the inner door panel. Summary of the invention

[0004] The purpose of the present invention is to provide a method for producing hot-dip galvanized steel for automobile door inner panels. The product is suitable for stamping door inner panels in a certain car factory. The product produced by this method has been used by users and has suitable performance and good stamping effect for stamping door inner panels. The mechanical properties of the strip steel meet the following requirements: yield strength 120≤R p0.2 ≤180MPa, tensile strength 260≤R m ≤350MPa, yield strength ratio ≤0.60, elongation A 80 ≥41%, r 90 ≥2.6, 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 producing hot-dip galvanized steel for automobile door inner panels, 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 cleaning 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 to RH by the converter. After decarburization, aluminum particles are added for deoxidation and alloying according to the oxygen determination conditions. After circulating for more than 4 minutes, ferromanganese and ferrotitanium alloy are added to adjust the composition. After the composition is adjusted, ensure that the vacuum cycle is ≥8 minutes. The chemical composition of the molten steel supplied to the casting machine is C≤0.0020% by mass; Si≤0.01%; Mn≤0.20%; P≤0.010%; S≤0.012%; 0.055≤Ti≤0.075%; N≤0.0030%; O≤0.0030%, and the rest is iron and impurities; the overheat of slab continuous casting is 25-40℃, and the pulling speed is controlled at 1.0-1.8m / min;

[0008] Hot rolling production process: heating of ingot - rough rolling - finishing rolling - coiling; the heating temperature of the ingot is 1170-1210℃, the furnace temperature is 1170-1210℃, the rough rolling adopts 3+3 mode 2-stand rolling mill, the finishing rolling adopts 7-stand rolling mill, the finishing rolling temperature is 900-940℃, the thickness of the hot rolled steel strip is 3.5mm; the cooling adopts laminar cooling equipment, and the coiling temperature is 690-740℃;

[0009] 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;

[0010] 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 780-830℃, and the elongation of the skin pass machine is 0.7-0.8%;

[0011] The annealing heating temperature is 780-830°C, and the annealing soaking temperature is 780-830°C.

[0012] Furthermore, the heating system of the ingot is as follows: heating temperature 1170-1210°C, heating time 180-300min, soaking temperature 1170-1210°C, soaking time 30-60min, and furnace discharge temperature 1170-1210°C.

[0013] Furthermore, the ingot thickness is 230 mm and the hot-rolled thickness is 3.5 mm.

[0014] Furthermore, the finishing rolling temperature is 900-940°C.

[0015] Furthermore, the chemical composition of the hot-dip galvanized steel for automobile door inner panels is as follows by mass percentage: C 0.0020%; Si 0.005%; Mn 0.13%; P 0.006%; S 0.004%; Ti 0.066%; N 0.0025%; O 0.0017%, and the rest is iron and impurities.

[0016] Furthermore, its mechanical properties meet the following requirements: yield strength 120 ≤ R p0.2 ≤180MPa, tensile strength 260≤R m ≤350MPa, yield strength ratio ≤0.60, elongation A 80 ≥41%, r 90 ≥2.6, n 90 ≥0.21.

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

[0018] This product is suitable for stamping car door inner panels in a certain car factory. The products produced by this method have been used by users and have suitable performance and good stamping effect for stamping car door inner panels. The mechanical properties of the strip steel meet the following requirements: yield strength 120≤R p0.2 ≤180MPa, tensile strength 260≤R m ≤350MPa, yield strength ratio ≤0.60, elongation A 80 ≥41%, r 90 ≥2.6, n 90 ≥0.21. DETAILED DESCRIPTION

[0019] 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.

[0020] Example

[0021] According to the above steelmaking process requirements, the actual slab chemical composition (mass percentage) is shown in Table 1 below.

[0022] Table 1: Chemical composition (%)

[0023]

[0024] 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.

[0025] Table 2: Rolling process

[0026] Hot rolled thickness(mm) Finish rolling temperature (℃) Coiling temperature(℃) 3.5 900-930 700-725

[0027] 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.

[0028] Table 3: Galvanizing process

[0029]

[0030] The mechanical properties of the steel strip products obtained through the above process are shown in Table 4. The test method refers to GB / T 228.1.

[0031] Table 4: Mechanical properties

[0032]

[0033] From the data in Table 7, it can be seen that the present invention discloses a method for manufacturing a hot-dip galvanized stamping product with high elongation and r value. The product is suitable for stamping door inner panels in a certain car factory. The mechanical properties of the strip steel meet the following requirements: yield strength 120≤R p0.2 ≤180MPa, tensile strength 260≤R m ≤350MPa, yield strength ratio ≤0.60, elongation A 80 ≥41%, r 90 ≥2.6, n 90 ≥0.21.

[0034] In summary, the process has obtained a manufacturing method for hot-dip galvanized stamping products with high elongation and r-value. This product is suitable for stamping door inner panels in a certain car factory. The products produced by this method have been used by users and have suitable performance and good stamping effect on stamping door inner panels. It can be extended to other parts of new models and referenced for the use of other deep-drawn automotive steels.

[0035] 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 producing hot-dip galvanized steel for automobile door inner panels, 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 determination conditions. After circulating for more than 4 minutes, ferromanganese and ferrotitanium alloy are added to adjust the composition. After the composition adjustment is completed, the vacuum cycle is ensured to be ≥8 minutes. The chemical composition of the molten steel supplied to the casting machine is C≤0.0020%; Si≤0.01%; Mn≤0.20%; P≤0.010% by mass. S≤0.012%;0.055≤Ti≤0.075%; N≤0.0030%; O≤0.0030%, the rest is iron and impurities; slab continuous casting superheat 25-40℃, casting speed controlled at 1.0-1.8m / min; Hot rolling production process: heating of ingot - rough rolling - finishing rolling - coiling; the heating temperature of the ingot is 1170-1210℃, the furnace temperature is 1170-1210℃, the rough rolling adopts 3+3 mode 2-stand rolling mill, the finishing rolling adopts 7-stand rolling mill, the finishing rolling temperature is 900-940℃, the thickness of the hot rolled steel strip is 3.5mm; the cooling adopts laminar cooling equipment, and the coiling temperature is 690-740℃; 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 780-830℃, and the elongation of the skin pass machine is 0.7-0.8%; The annealing heating temperature is 780-830°C, and the annealing soaking temperature is 780-830°C.

2. The method for producing hot-dip galvanized steel for automobile door inner panels according to claim 1, characterized in that: Ingot heating system: heating temperature 1170-1210℃, heating time 180-300min, soaking temperature 1170-1210℃, soaking time 30-60min, furnace discharge temperature 1170-1210℃.

3. The method for producing hot-dip galvanized steel for automobile door inner panels according to claim 1 or 2, characterized in that: The ingot thickness is 230mm and the hot rolled thickness is 3.5mm.

4. The method for producing hot-dip galvanized steel for automobile door inner panels according to claim 1, characterized in that: The final rolling temperature is 900-940℃.

5. The method for producing hot-dip galvanized steel for automobile door inner panels according to claim 1, characterized in that: The chemical composition of the hot-dip galvanized steel for automobile door inner panels is as follows: C 0.0020%, Si 0.005%, Mn 0.13%, P 0.006%, S 0.004%, Ti 0.066%, N 0.0025%, O 0.0017%, and the rest is iron and impurities.

6. The method for producing hot-dip galvanized steel for automobile door inner panels according to claim 1, characterized in that: Its mechanical properties meet the following requirements: yield strength 120≤R p0.2 ≤180MPa, tensile strength 260≤R m ≤350MPa, yield strength ratio ≤0.60, elongation A 80 ≥41%, r 90 ≥2.6, n 90 ≥0.21.

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