No surface streak defect 590mpa grade cold-rolled dual-phase steel and production method

Abstract

The invention provides a 590MPa grade cold-rolled dual-phase steel without surface stripe defect and a production method thereof. The steel comprises the following components by weight percentage: 0.050% to 0.100% of C, less than or equal to 0.25% of Si, 1.20% to 2.00% of Mn, less than or equal to 0.012% of P, less than or equal to 0.008% of S, 0.05% to 0.10% of Al, 0.015 to 0.050% of Sb, and thebalance being Fe and other unavoidable impurities; The production method comprises the steps of smelting, continuous casting, hot charging heating, high pressure water descaling and rough rolling, finishing rolling, laminar cooling, reeling, hot rolling sheet pickling cold rolling, continuous annealing, air cooling, and leveling reeling, the 590MPa grade cold-rolled dual-phase steel produced by the invention has bright surface, no streaky defects, good corrosion resistance and coating adhesion, and excellent mechanical properties.

Description

technical field [0001] The invention belongs to the field of cold-rolled high-strength steel production, in particular to a 590MPa grade cold-rolled dual-phase steel without surface streak defects and a production method thereof. Background technique [0002] The environment, energy and personal safety requirements of drivers and passengers require that modern cars should be lightweight, safe and environmentally friendly, and low-cost manufacturing. The main measure to achieve this requirement is to use a large number of advanced high-strength steels in the manufacture of car bodies. Advanced high-strength steel-duplex steel (DP steel) has been widely used in automobile lightweight body-in-white due to its low yield ratio, good strength and toughness. At present, cold-rolled dual-phase steel covers the range of strength levels from 450MPa to 1180MPa, and commercial mass production is mainly of strength levels of 980MPa and below. Among them, 590MPa-grade cold-rolled dual-pha...

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Problems solved by technology

In the annealing production line with CAL (air-cooled line) cooling method, a certain amount of Si alloy elements need to be added to the composition of the 590MPa grade cold-rolled dual-phase steel to ensure the solid solution strengthening effect and elongation after fracture of the steel plate. However, in the steel When the Si content is high, FeSi2O4 is easily formed between the iron oxide scale and the substrate during the heating process of the slab, which will firmly stick the iron sheet to the substrate, increasing the difficulty of descaling before rough rolling and finish rolling, and easily descaling in the subsequent hot rolling process. Pressed into the steel plate matrix, resulting in linear stripe defects on the surface of the steel plate after pickling and cold rolling, affecting the phosphating effect of the steel plate, weakening the durability and corrosion resistance of the coating of parts, and reducing the service life of the car

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