Ultrahigh strength cold rolled steel sheet with superior hydrogen embrittlement resistance and manufacturing method thereof

Abstract

The invention provides an ultrahigh strength steel sheet used for processing and a manufacturing method thereof. The ultrahigh strength steel sheet has tensile strength of 980-1670MPa and superior hydrogen embrittlement resistance, and comprises, by mass%: 0.05-0.17% of C, 0.2-1.5% of Si, 1.7-3.5% of Mn, less than or equal to 0.030% of P, less than or equal to 0.010% of S, 0.025-0.120% of Al, less than or equal to 0.0100% of N, 3.43*N-0.150% of Ti, and the balance 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 ...

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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

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