Production method for improving yield-strength ratio and stretch-flange-formability of cold-rolled DP980 steel

Abstract

The invention discloses a production method for improving the yield-strength ratio and stretch-flange-formability of cold-rolled DP980 steel. On the basis of the chemical composition design of existing cold-rolled DP980 steel, through control over the process parameters of a slab heating procedure, a hot rolling procedure and a cooling and coiling procedure, hot-rolled initial structures comprisepearlite, medium temperature bainite mixed structures and equiaxial ferrite structures, wherein all the grain sizes are no more than 5.0 [mu]m, and the average grain size is no more than 3.2 [mu]m. The volume fraction of martensite in the microstructure of the cold-rolled DP980 steel prepared with the production method provided by the invention is larger than 30.0%, and the yield-strength ratio islarger than 0.70; the hole expanding rate is no less than 55%, and meanwhile the elongation reaches 12.9% and above; and the production method is especially applicable for automobile structural members and stiffeners with the requirements for 980 MPa high tensile strength and excellent drawing characteristic as well as reaming and flanging requirements.

Description

technical field [0001] The invention belongs to the technical field of cold-rolled high-strength steel for automobiles, and in particular relates to a production method for improving the yield ratio and hole-expanding performance of cold-rolled DP980 steel. Background technique [0002] In recent years, the rapid development of the automobile industry has strongly promoted the medium-to-high speed development of my country's national economy, but the resulting high energy consumption and high emissions are seriously polluting the environment and having many negative impacts on people's daily life. It can be seen that in order to realize the sustainable development of the automobile industry, the problems of energy saving, emission reduction and low-carbon environmental protection must be solved. This is also the primary problem that the automobile industry of various countries must solve. The new demand for integration, comfort and energy saving requires not only to achieve ...

AI Technical Summary

Problems solved by technology

[0003] The technical problem to be solved by the present invention is to produce high yield ratio and hole expansion rate by regulating the key process parameters of each process section on the basis of the chemical composition design of the existing 980MPa grade cold-rolled DP steel, and at the same time have good drawing Featured cold-rolled DP980 steel to solve the problem that the traditional low-yield-ratio cold-rolled DP980 steel cannot meet the requirements of hole expansion and flanging during the cold forming process, which inevitably leads to defects such as cracking

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