TH177008B - High strength cold rolled steel sheet And methods for the production of steel sheets - Google Patents

Abstract

It provides a high-strength cold-rolled steel sheet with a tensile strength (TS) of 1,300 MPa or higher, good chemical conversion properties. And good formability And how to Production of high strength cold rolled steel sheets High strength cold rolled steel sheet contains C 0.15% or more and 0.22% or less, Si: 1.0% or more and 2.0% or less, Mn: 1.7% or more and 2.5% or less, P: 0.05% or less. S: 0.02% or less, Al: 0.01% or more, and 0.05% or less, N: 0.005% or less, O: 0.01% or less, and iron balancing impurities and Unavoidable The composition corresponds to [Si] / [Mn] (formula) 0.5 ([Si] represents the quantity Si and [Mn] represents the Mn content (% by mass)). Steel plates have a structure that is fractions by area including. Martensites are 60% or more tempered and less than 100%, 5% or less phase-shifted austenite (including 0%), and ferrite-based balancing agents. And ferrites have an average crystalline grain size of less than 3.5 μm, Si-Mn compound oxide particles with a circle diameter of 5 μm or less, less than 10 particles / 100 μm2 are present on the surface of Steel plate And the surface of the steel plate is covered with Si-based oxides of 1% or less:

Claims (1)

1. High-strength cold-rolled steel sheet with composition% by mass, consisting of C 0.15% or more and 0.22% or less, Si: 1.0% or more and 2.0% or less, Mn: 1.7% or Greater than and 2.5% or less P: 0.05% or less S: 0.02% or less Al: 0.01% or more and 0.05% or less N: 0.005% or less Additives that are inevitable Where the composition corresponds to formula (1) below, where the steel plate is structured to: