Production method for improving yield ratio and bore expansion of 1000MPa-level high-strength steel

A production method and technology of high-strength steel, applied in furnaces, heat treatment equipment, heat treatment furnaces, etc., can solve problems such as difficulty in achieving complete austenitization of strip steel, difficulty in achieving yield strength, and low yield ratio
CN103290202AActive Publication Date: 2013-09-11SHOUGANG CORPORATION
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Patent Information

Authority / Receiving Office
CN · China
Current Assignee / Owner
SHOUGANG CORPORATION
Publication Date
2013-09-11

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Abstract

The invention provides a method for improving a yield ratio and bore expansion of 1000MPa-level high-strength steel. The production method, which utilizes the existing 1000 MPa-level double-phase steel cold-rolled base material, comprises the following steps of: adopting a two-phase region heating mode and a three-stage cooling mode to obtain polygonal ferrite with the area fraction of 35-45%, lath upper bainite with the area fraction of 30-40% and martensite tissue with the area fraction of 10-25% in a metallographic figure; and using the lath upper bainite with the tissue type as a middle buffer phase of the ferrite and the martensite to buffer phase interface early-stage cracking caused by hardness difference of the ferrite and the martensite during a local flanging process. According to the production method for improving the yield ratio and bore expansion of the 1000MPa-level high-strength steel provided by the invention, the mechanical performances of the obtained 1000MPa-level high-strength steel are as follows: the tensile strength is bigger than 1000MPa, the yield ratio is 0.7-0.9, elongation at 80 scale distance is bigger than 10%, and the bore expansion rate is bigger than 50%.
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Description

technical field

[0001] The invention belongs to the technical field of iron and steel smelting and processing, in particular to a production method for improving the yield ratio and hole expandability of 1000MPa high-strength steel. Background technique

[0002] To obtain 1000MPa cold-rolled continuous annealed ultra-high-strength steel with high yield strength, it is difficult to meet the strength requirements if only considering the mixed structure of ferrite and rigid pearlite, represented by low-alloy high-strength steel with Nb addition, the yield strength is greater than 500MPa, When the tensile strength level reaches above 600 MPa, the elongation rate deteriorates significantly. The introduction of martensite for phase strengthening has a significant effect on improving the tensile strength, so the dual-phase steel mainly composed of ferrite and martensite has been widely studied and applied, but this type of steel has an extremely low yield ratio, which is important ...

Claims

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