Automotive alloying hot-dip galvanized steel with tensile strength of 440 MPa and production method

Abstract

Automotive alloying hot-dip galvanized steel with tensile strength of 440 MPa comprises, by weight, 0.08%-0.11% of C, smaller than or equal to 0.03% of Si, 1.10%-1.40% of Mn, 0.015 wt%-0.030% of P, smaller than or equal to 0.010% of S and 0.020%-0.070 of Als. A production method comprises the production steps of hot metal pretreatment, converter refining and RH furnace treatment, continuous casting, casting blank heating, hot rolling, the first time of rapid cooling, reeling, acid pickling, cold rolling, continuous annealing, hot galvanizing, the second time of rapid cooling, alloying, the third time of rapid cooling and finishing. The yield strength of the automotive alloying hot-dip galvanized steel is 330-360 MPa, the tensile strength of the automotive alloying hot-dip galvanized steel is not lower than 440 MPa, the ductility of the automotive alloying hot-dip galvanized steel is larger than or equal to 32%, the roughness of the alloying hot-dip galvanized steel is 0.6-1.5 [u]m, and the PC value of the automotive alloying hot-dip galvanized steel is not smaller than 90 / cm; a galvannealed coating of the automotive alloying hot-dip galvanized steel is small, even and compact in tissue, the pulverization degree is not larger than 2, and the pulverization resisting capability is excellent. Meanwhile, ingredients and technology of the automotive alloying hot-dip galvanized steel are simple, cost is low, and production efficiency is high.

Description

Technical field [0001] The invention relates to a galvanized steel for automobiles and a production method thereof, in particular to a hot-dip galvanized steel for automobiles with a tensile strength of 440MPa and a production method thereof. Background technique [0002] Alloyed hot-dip galvanized steel sheet (GA sheet) has excellent performance in terms of stamping formability, corrosion resistance, paintability and weldability. It meets the development requirements of automobile lightweight and strong safety, which has increasingly caused the automobile industry Attention. This is because to meet the anti-corrosion requirements of the car body, the quality of the coating must be controlled at 40g / m 2 As mentioned above, the production cost of electro-galvanized sheets increases sharply as the thickness of the coating increases. Therefore, how to ensure the corrosion resistance of the steel surface without excessively increasing production costs has become an important issue. ...

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Problems solved by technology

[0005] Although the tensile strengths of the above-mentioned documents are all at 440 MPa, in order to achieve high strength, a large amount of alloying elements are added, resulting in high production costs; After fast cooling and alloying, the cooling rate is slow, so it is difficult to obtain a high-strength alloyed hot-dip galvanized steel sheet with fine grains, dense and uniform coating surface structure, less micro-cracks, and excellent powdering resistance

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