Strip steel with excellent low-temperature secondary machining performance and tensile strength being 370 MPa level and production method

Abstract

The invention provides strip steel with excellent low-temperature secondary machining performance and the tensile strength being 370 MPa level. Components of the strip steel with the excellent low-temperature secondary machining performance and the tensile strength being 370 MPa level comprise, by weight, 0.0008-0.0028% of carbon, 0.07-0.10% of silicon, 0.30-0.50% of manganese, 0.04-0.055% of phosphorous, smaller than or equal to 0.008% of sulphur, 0.02-0.045% of aluminum, 0.02-0.06% of titanium, 0.006-0.022% of niobium, 0.0005-0.0013% of boron and smaller than or equal to 0.002% of nitrogen.Production of the strip steel comprises the steps of smelting and casting into billets, heating the cast billets, rough rolling, finish rolling, coiling, cold rolling after acid pickling, continuous annealing treatment, slow cooling, rapid cooling, aging treatment and levelling. According to the strip steel with the excellent low-temperature secondary machining performance and the tensile strengthbeing 370 MPa level, under the premise that the mechanical property is guaranteed, the plastic strain ratio ranges between 1.8 and 2.0 r90, and the strain hardening exponent ranges between 0.2 and 0.21 n90; the secondary machining brittle transition temperature is stabilized between minus 60 DEG C and minus 70 DEG C; the quantity of the titanium element and the niobium element is reduced so thatthe cost is lowered by 5% or more; no carbonized edges or bonding defects exist on the steel plate surface; and the strip steel is used for automobile outer covering parts used in more severe cold areas.

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 370 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 original thickness of 1.0-1.2 mm body steel plates can be reduced to 0.7-0.8 mm. [0...

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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

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