Ultra high strength steel sheet generating no hydrogen embrittlement and its manufacturing method

An ultra-high-strength, manufacturing method technology, applied in the field of ultra-high-strength thin steel plates, can solve problems such as strength reduction, poor processability, and failure to take into account, and achieve significant effects and significant lightweight effects

Active Publication Date: 2014-02-12
KOBE STEEL LTD
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  • Abstract
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  • Claims
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Problems solved by technology

However, such steels have poor formability compared to ultra-high-strength thin steel sheets that are processed by press forming or the like.
In addition, in ultra-high-strength thin steel sheets, it is considered that hydrogen embrittlement is likely to occur due to the increase in strength due to cold working, but this characteristic has not been considered
[0006] In general, ultra-high-strength steel sheets manufactured by continuous annealing have low amounts of C and Mn in order to ensure cold workability such as press forming. When tempering is performed at 400°C or higher, the strength decreases and the desired properties cannot be obtained.

Method used

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  • Ultra high strength steel sheet generating no hydrogen embrittlement and its manufacturing method
  • Ultra high strength steel sheet generating no hydrogen embrittlement and its manufacturing method
  • Ultra high strength steel sheet generating no hydrogen embrittlement and its manufacturing method

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Embodiment Construction

[0022] The present invention will be described in further detail below. First, the reason for the limitation of the carbide of the present invention will be explained.

[0023] The present inventors have conducted intensive research on the hydrogen embrittlement of ultra-high-strength steel sheets subjected to cold processing such as press forming and bending processing under corrosive environments such as the atmosphere and salt water spray.

[0024] As a result, the damage caused by hydrogen embrittlement is generated from the cold-worked part. In the steel plate that is damaged in a short time, the grain boundary damage is the main damage surface, and the ratio of Fe-C precipitates of 0.1μm or more per 1mm 2 3×10 5 Also more precipitated. On the other hand, it was found that in steel plates with a long failure time, intragranular failure is the main failure surface. Like steel plates without hydrogen embrittlement, Fe-C precipitates of 0.1 μm or more are present per 1 mm 2 3×10 ...

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Abstract

The invention provides an ultra high strength steel sheet that has tensile strength of over 980MPa, generates no hydrogen embrittlement and is used for processing. The ultra high strength steel sheet generating no hydrogen embrittlement is composed of, by mass percent: 0.05-0.25% of C, 1.0-3.0% of Mn, 0.025-0.100% of Al, less than 0.01% of S, less than 0.008% of N, and the balance iron and unavoidable impurities. With tensile strength of more than 980MPa and a martensite content of over 70% by volume, the ultra high strength steel sheet is characterized in that the content of Fe-C system precipitates greater than 0.1 micrometer is less than 3*10<5> per 1mm<2>.

Description

Technical field [0001] The present invention relates to an ultra-high-strength thin steel sheet suitable for applications requiring light weight and strength resistance, such as automobile bumpers and door reinforcement parts, and a method for manufacturing the same. Background technique [0002] The US’s CAFE (Corporate Average Fuel Economy) restriction and enhancement proposal promotes the reduction of the weight of automobiles, and the bumpers and door reinforcements are made of ultra-high-strength thin steel plates of 980MPa or more. [0003] The occurrence of hydrogen embrittlement in ultra-high-strength steel of 980 MPa or more has been known, for example, through the training text "Design and Practice of Screw Tightening" issued by the Japan Screw Industry Association (October 18, 1990). Therefore, in the ultra-high-strength thin steel sheet, it is considered that hydrogen generated by the corrosion reaction in the atmospheric environment also enters the steel sheet and is s...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/38C22C38/12C22C38/14C21D8/02
Inventor 内海幸博村上俊夫田中福辉三村和弘大宫良信
Owner KOBE STEEL LTD
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