Method for producing ultra-high-strength cold-rolled steel sheet superior in hydrogen embrittlement resistance

Abstract

Provided are an ultra-high-strength thin steel sheet for processing with a tensile strength of 980-1670 MPa, which is ultra-high-strength and excellent in hydrogen embrittlement resistance, and a manufacturing method thereof. The ultra-high-strength cold-rolled steel sheet excellent in hydrogen embrittlement resistance has a tensile strength of 980-1670 MPa, and contains C: 0.05-0.17%, Si: 0.2-1.5%, and Mn: 1.7-3.5% in mass % , P≤0.030%, S≤0.010%, Al: 0.025-0.120%, N≤0.0100%, Ti: 3.43×N-0.150%, and the balance is composed of iron and unavoidable impurities.

Description

technical field [0001] The present invention relates to an ultra-high-strength cold-rolled steel plate with excellent hydrogen embrittlement resistance and a tensile strength of 980-1670 MPa and a manufacturing method thereof, in particular to a hydrogen embrittlement resistance after being processed by stamping or roll forming. An excellent method for producing ultra-high-strength cold-rolled steel sheets is, specifically, suitable for the production of ultra-high-strength steel sheets that are suitable for light-weight applications that require strength, such as automotive bumpers and door reinforcements. Background technique [0002] With the weight reduction of automobiles, ultra-high-strength thin steel sheets of 980 MPa or more are often used in tube shapes by press forming or roll forming for strength parts such as bumpers and door impact beams. [0003] Hydrogen embrittlement has been known to occur in ultra-high-strength steels of 980 MPa or higher, for example, by ...

AI Technical Summary

Problems solved by technology

[0007] However, such steel is inferior in workability, unlike thin steel sheets subjected to processing such as press forming and roll forming.

In addition, as mentioned above, there is no consideration of the fact that hydrogen embrittlement is likely to occur due to the existence of residual stress or the generation of cavities or cracks in the steel plate structure due to strong working.

In addition, the ultra-high-strength steel plate usually produced by continuous annealing method is to cool the steel with low content of C and Mn to below the martensitic transformation point at a faster cooling rate after soaking, and then cool it below 400°C. Manufactured by tempering, but this manufacturing method is a manufacturing method completely different from the known method for bar steel, so a countermeasure different from the field of bar steel is required

Images