Process for production of cold-rolled steel sheet having excellent press moldability, and cold-rolled steel sheet

Abstract

Disclosed are: a cold-rolled steel sheet which undergoes less load during cold rolling and has excellent press moldability and high strength; and a process for producing the cold-rolled steel sheet. A hot-rolled steel sheet comprising 0.10 to 0.30 mass% of C, 0.2 mass% or more of Mn, 0.01 mass% or more of Ni (wherein the sum total of Mn and Ni is 0.5 to 2.5 mass%), and 1.2 to 9.0 mass% of Cr, with the remainder being iron and unavoidable impurities, and having a tensile strength of 1000 MPa or less is washed with an acid, and is subjected to cold rolling at a total rolling ratio of 60% or more, thereby producing a cold-rolled steel sheet. The cold-rolled steel sheet is subjected to the final continuous annealing treatment at a homogenizing temperature of 750 DEG C or higher and a cooling rate of 3 to 100 DEG C / s. In this manner, a cold-rolled steel sheet having a tensile strength of 1280 MPa or more, a breaking elongation of 3% or more, and a thickness of 0.05 to 0.60 mm.

Description

technical field [0001] The present invention relates to a method for producing a cold-rolled steel sheet excellent in press formability, and a cold-rolled steel sheet produced by the production method. Background technique [0002] Liquid crystal frame parts used in mobile phones, notebook computers, etc., and automotive engine gasket parts are often cold-formed. Therefore, the cold-rolled steel sheets used require press-formability. [0003] In addition, electronic components represented by notebook computers, mobile phones, and digital cameras, and automobile engine gaskets are also required to reduce weight and size. In order to reduce the weight and size of these components, it is necessary to reduce the thickness of the steel plate , In addition, since the same strength cannot be ensured as a pressed part, it is necessary to provide a high-strength steel sheet having a thin size and high strength. [0004] Proceeding from this technical background, aiming at the use as...

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Problems solved by technology

[0003] In addition, electronic components represented by notebook computers, mobile phones, and digital cameras, and automotive engine gaskets are also required to reduce weight and size. In order to reduce the weight and size of these components, it is necessary to reduce the thickness of the steel plate , In addition, since the same strength cannot be ensured as a pressed part, it is necessary to provide a high-strength steel sheet with a thin size and high strength

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