Strip steel with excellent performance at low temperature secondary processing and with tensile strength being 390 MPa and production method

Abstract

The invention discloses strip steel with excellent performance at low temperature secondary processing and with tensile strength being 390 MPa. The steel comprises the following components of, by wt%,0.0008%-0.0028% of C, 0.07%-0.1% of Si, 0.5%-0.7% of Mn, 0.060%-0.075% of P, less than or equal to 0.008% of S, 0.02-0.05% of Al, 0.02%-0.06% of Ti, 0.006%-0.022% of Nb, 0.0005%-0.0015% of B, and less than or equal to 0.002% of N. The production steps comprise smelting and casting into a blank, cast blank heating, rough rolling, finish rolling, coiling, cold rolling after acid pickling, continuous annealing treatment, slow cooling, rapid cooling, aging treatment and flattening. According to the steel, under the premise of guaranteeing mechanical property, a plastic strain ratio is 1.6-1.8r<90>, a strain hardening index is 18-0.19n<90>, a brittle transition temperature of the secondary processing is stabilized at minus 60-minus 70 DEG C, the quantities of the elements Ti and the Nb are reduced, the cost is reduced by no less than 5%, the surface of a steel plate is free of carbonization edges and bonding defects, and the steel is used for an outer cover of an automobile in a more severe cold area.

Description

technical field [0001] The invention relates to a steel for automobiles and a production method, in particular to a strip steel with a tensile strength of 390 MPa and a production method with excellent secondary processing performance at low temperature, which is especially suitable for high-strength automobile outer covering parts used in northern severe cold regions steel. Background technique [0002] With the development of automobile lightweight, the proportion of cold-rolled high-strength steel in automobile outer covering materials is getting higher and higher. Studies have shown that about 75% of fuel consumption is related to vehicle quality, and reducing vehicle quality can effectively reduce fuel consumption and emissions. For every 10% reduction in vehicle quality, fuel consumption will drop by 8%, and emissions will drop by 4%. With the use of high-strength steel plates, the body steel plates with an original thickness of 1.0-1.2 mm can be reduced to 0.7-0.8 m...

AI Technical Summary

Problems solved by technology

[0004] Deficiencies in the prior art: some elements are not matched with C elements and Ti and Nb elements, and a large amount of FePTiNb composite precipitates are easily precipitated on the grain boundaries during hot rolling, thereby weakening the secondary processing of the product performance, so that the secondary processing embrittlement temperature can not reach -60 ℃ or lower

However, this steel is a hot-dip coated steel plate, and the ductile-brittle transition temperature is above -50°C, which cannot meet the secondary processing brittleness requirements of the body in a low-temperature environment

Images