CN-121988614-A - Control method for tiny skin warping defect on surface of galvanized DP steel automobile plate

Abstract

The application relates to the technical field of DP steel production and discloses a control method for micro-skin-tilting defects on the surface of a galvanized DP steel automobile plate, which comprises the steps of S1, raw material selection, S2, heating, S3, descaling, hot plate blank descaling by high-pressure water, rough rolling, S5, finish rolling, S6, cooling, S7, pickling, S8, cold rolling, S9, annealing and galvanization. The application improves the tiny skin-warping defect of the surface of the galvanized DP steel automobile plate in the prior art.

Inventors

• ZHOU GUANGCHAO
• DUAN HAOJIE
• ZHANG SONG
• TANG HAO
• LIU XUHUI
• LIANG LIANG
• YANG XIUZHI
• CHEN QIANG
• ZHAO RU
• LIU WENHUA
• WANG ZHAOMING
• RAN TAO

Assignees

• 湖南华菱涟源钢铁有限公司
• 湖南华菱涟钢特种新材料有限公司

Dates

Publication Date

20260508

Application Date

20260210

Claims (10)

1. 1. A control method for the tiny skin-lifting defect on the surface of a galvanized DP steel automobile plate is characterized by comprising the steps of S1, raw material selection, S2, heating, S3, descaling, hot plate blank descaling by high-pressure water, S4, rough rolling, S5, finish rolling, S6, cooling, S7, pickling, S8, cold rolling, S9, annealing and galvanization.
2. 2. The method for controlling the micro-scale defects on the surface of the galvanized DP steel automobile plate according to claim 1 is characterized in that in S1, a continuous casting plate blank is selected, the continuous casting plate blank is from steelmaking, the thickness of the plate blank is 200-250 mm, the width of the plate blank is 900-1950 mm, and the mass percentage of each chemical component of the DP steel product is ：C：0.05～0.09;Si：0～0.3;Mn：2.1～2.6;P≤0.02;S≤0.005;Cr：0.3～0.5;Alt：0.7～0.9;N≤0.004;Nb：0.02～0.03;B：0.001～0.002;Ti：0.02～0.03;, and the balance is Fe and unavoidable trace elements.
3. 3. The method for controlling the tiny skin warping defect on the surface of the galvanized DP steel automobile plate, which is characterized in that in S2, a continuous casting plate blank is heated according to preset heating time and heating temperature after being fed into a furnace to obtain a hot plate blank, wherein the heating mode is to heat the plate blank through flame radiation by nozzle injection, the fuel is coal gas, the oxidizing property of a heating atmosphere is controlled by adjusting the air excess coefficient, and the heating mode requires the air excess coefficient to be 1.0-1.05 and the heating temperature to be 1200-1340 ℃.
4. 4. The method for controlling the micro-skin-tilting defect on the surface of the galvanized DP steel automobile sheet according to claim 1, wherein in the step S4, 7-pass rolling is adopted in the rough rolling stage, the continuous casting sheet billet is rolled to an intermediate billet with the thickness of 28-50mm, and the temperature of the sheet billet at the end of rough rolling is 1050-1100 ℃.
5. 5. The method for controlling the micro skin warping defect on the surface of the galvanized DP steel automobile sheet according to claim 1, wherein in S5, a finish rolling unit obtains a DP steel hot rolled coil with the thickness of 2-6mm, the finish rolling outlet temperature is 900-950 ℃, and the fine descaling is carried out by putting two groups of headers and the descaling pressure is 18-25MPa.
6. 6. The method for controlling the micro-scale defects on the surface of the galvanized DP steel automobile sheet according to claim 1, wherein in S6, the finish rolling strip steel is cooled to about 500 ℃ through laminar cooling, the cooling rate is more than or equal to 60 ℃ per second, and the strip steel is conveyed to a coiling unit through a laminar cooling roller way to finish coiling.
7. 7. The method for controlling micro skin warping defect on a galvanized DP steel automobile sheet according to claim 6, wherein in S7, the hot rolled steel coil after laminar cooling is cooled to room temperature and sent to cold rolling and pickling, and the pickling speed is set to 200-240 m/min.
8. 8. The method for controlling the micro-skin-tilting defect on the surface of the galvanized DP steel automobile sheet according to claim 7, wherein in S8, the pickled strip steel is rolled into cold-rolled strip steel with the thickness of 0.9-2.5mm by a cold rolling unit, and the roughness of the cold-rolled roll is controlled to be less than or equal to 1.2 mu m by using a low-roughness roller, less than or equal to 0.8 mu m by using four racks and less than or equal to 0.5 mu m by using five racks.
9. 9. The method for controlling micro skin warping defect on a galvanized DP steel automobile sheet according to claim 8, wherein in S9, the cold rolled strip is annealed at a temperature of 830-860 ℃ for 360-420 seconds.
10. 10. The method for controlling micro skin warping defect on the surface of a galvanized DP steel automobile sheet according to claim 9, wherein in S10, the annealed substrate enters a zinc pot to finish galvanization, and the temperature of the zinc liquid is controlled to be 452-459 ℃.

Description

Control method for tiny skin warping defect on surface of galvanized DP steel automobile plate Technical Field The application relates to the technical field of DP steel production, in particular to a control method for micro skin warping defects on the surface of a galvanized DP steel automobile plate. Background Cold rolled DP car steel (dual phase steel) is an advanced high strength car steel sheet whose microstructure mainly consists of ferrite and martensite, the martensite structure being dispersed and distributed in islands on the ferrite matrix. The ferrite is softer, so that the steel has better formability, and the martensite is harder, so that the steel has higher strength. The composite material has excellent mechanical property, good forming property, excellent welding property, excellent collision energy absorption property and remarkable automobile light weight effect. DP steel is one of the first choice steel grades of the existing automobile structure parts, is widely applied to structural members, reinforcing members and anti-collision members, and has large application amount and good application effect. However, in the production process of galvanized DP steel automobile plates, the pit defect caused by tiny skin tilting on the surface of a galvanized plate finished product often occurs, the size of the skin tilting is extremely tiny and is about 50-70 mu m, and the defect is difficult to find before galvanization. A large number of tiny black pits appear on the surface after galvanization, which affects the appearance quality of the automobile parts manufactured by the galvanized steel sheet, and the appearance parts have very bad influence. Meanwhile, the defects can weaken the uniformity and compactness of the plating layer, so that the local corrosion resistance is reduced, the steel plate is easy to rust from the pitting position in the subsequent use process, and the service life of the product is shortened. Less researches are directed to the problem, and the temperature and humidity process of an industrial furnace inlet cleaning section is mainly adjusted from the annealing process after cold rolling to reduce the depth of pits on the surface of DP steel. Or polishing strip steel before galvanization to remove surface oxide skin and tiny impurities, and limiting the total content of impurities such as lead, tin and the like in zinc liquid to be less than or equal to 0.005wt percent, so as to reduce plating pockmarks caused by the impurities, but the problem of skin tilting of a steel plate substrate caused by the source cannot be well solved. Therefore, aiming at the defects of the prior art, the full-flow process improvement is optimized from the root, so that the problem of tiny skin tilting on the surface of DP steel is effectively solved, and the problem of pitting on the surface of galvanized steel sheets caused by the problem is improved. The method has important significance for improving the market competitiveness of the product and promoting the high-quality development of related industries. Disclosure of Invention The application aims to provide a control method for the tiny skin-tilting defect of the surface of a galvanized DP steel automobile plate, so as to solve the technical problem of tiny skin-tilting of the surface of the DP steel in the prior art. The application provides a method for controlling micro skin tilting defects on the surface of a galvanized DP steel automobile plate, which comprises the following steps of S1, raw material selection, S2, heating, S3, descaling, hot plate blank descaling by high-pressure water to remove surface oxidized iron scales, S4, rough rolling, S5, finish rolling, S6, cooling, S7, pickling, S8, cold rolling, S9, annealing and galvanization. Preferably, in S1, a continuous casting slab is selected, wherein the continuous casting slab is from steelmaking, the thickness of the slab is 200-250 mm, the width of the slab is 900-1950 mm, and the mass percentage of each chemical component of the DP steel product is ：C：0.05～0.09;Si：0～0.3;Mn：2.1～2.6;P≤0.02;S≤0.005;Cr：0.3～0.5;Alt：0.7～0.9;N≤0.004;Nb：0.02～0.03;B：0.001～0.002;Ti：0.02～0.03;, and the balance is Fe and unavoidable trace elements. In the S2, the continuous casting slab is heated according to preset heating time and heating temperature after being charged into a furnace, wherein the heating mode is to spray flame radiation through a burner to heat the slab, the fuel is coal gas, the oxidizing property of a heating atmosphere is controlled by adjusting the air excess coefficient, and the air excess coefficient is required to be 1.0-1.05. The heating temperature is 1200-1340 ℃. Preferably, in S4, 7-pass rolling is adopted in the rough rolling stage, the continuous casting slab is rolled to an intermediate slab with the thickness of 28-50mm, and the temperature of the slab after rough rolling is 1050-1100 ℃. Preferably, in S5, a finish rolling unit obtains DP steel hot rolled coil