Invention Grant
US08480819B2 High-strength cold-rolled steel sheet excellent in workability and method for manufacturing the same 有权
加工性优异的高强度冷轧钢板及其制造方法

High-strength cold-rolled steel sheet excellent in workability and method for manufacturing the same
Abstract:
In a cold-rolled steel sheet in relation with the present invention, metallurgical structure of the steel sheet is made a mixture structure including bainite, residual austenite and tempered martensite, particularly, when the metallurgical structure is observed with a scanning electron microscope, bainite is constituted of composite structure of high temperature range forming bainite with 1 μm or above average distance between neighboring residual austenite and/or carbide and low temperature range forming bainite with below 1 μm average distance between neighboring residual austenite and/or carbide, and when the area ratio of the high temperature range forming bainite with respect to total metallurgical structure is made a and the total area ratio of the low temperature range forming bainite and the tempered martensite with respect to the total metallurgical structure is made b, a: 20-80%, b: 20-80%, and a+b: 70% or above are satisfied. The cold-rolled steel sheet in relation with the present invention is improved in all of the elongation (EL), stretch flange formability (A), and bending properties (R) with a good balance, is excellent in the overall workability, and has 980 MPa or above tensile strength.
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