High-strength steel sheet and method for manufacturing same

A technology of high-strength steel plate and manufacturing method, which is applied in the direction of manufacturing tools, coatings, furnace types, etc., and can solve problems such as reduced toughness

Active Publication Date: 2021-05-18
JFE STEEL CORP
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] In addition, when high-strength steel sheets of 1180 MPa or higher are used, there

Method used

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  • High-strength steel sheet and method for manufacturing same
  • High-strength steel sheet and method for manufacturing same
  • High-strength steel sheet and method for manufacturing same

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Embodiment

[0160] Steels having the composition shown in Table 1 with the balance being Fe and unavoidable impurities were melted in a converter, and steel slabs were produced by continuous casting. The obtained slab was heated, pickled after hot rolling, and then cold rolled.

[0161] Next, an annealing treatment was performed under the conditions shown in Table 2 to obtain a high-strength cold-rolled steel sheet (CR). In addition, a part of the high-strength cold-rolled steel sheet was subjected to a plating treatment to obtain a hot-dip galvanized steel sheet (GI), an alloyed hot-dip galvanized steel sheet (GA), an electrogalvanized steel sheet (EG), and the like. For the hot-dip galvanizing bath, in the case of GI, a zinc bath containing Al: 0.14 to 0.19% by mass is used, and in the case of GA, a zinc bath containing Al: 0.14% by mass is used, and the bath temperature is 470°C. Regarding the amount of plating, in the case of GI, it is 45 to 72 g / m equivalent to one side 2 (Double-...

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Abstract

The purpose of the present invention is to provide: a steel sheet having a high-strength of 1180 MPa or more, excellent component dimension accuracy, stretch-flange characteristics, bendability, and toughness; and a method for manufacturing the same. This high-strength steel sheet has a predetermined compositional makeup and a tensile strength is 1180 MPa or more, and has a steel structure, wherein: the area percentage of martensite having a carbon concentration of more than 0.7x[%C] but less than 1.5x[%C] is 55% or more; the area percentage of tempered martensite having a carbon concentration of not more than 0.7x[%C] is 5-40%; the ratio of the carbon concentration of retained austenite with respect to the volume percentage of the retained austenite is 0.05-0.40; the respective average crystal particle sizes of the martensite and the tempered martensite are not more than 5.3 [mu]m. Note that [%C] represents the contained amount (mass%) of componental element C in steel.

Description

technical field [0001] The present invention relates to a high-strength steel plate of 1180 MPa or more excellent in dimensional accuracy of parts, stretch flangeability, bendability, and toughness, and a method for producing the same. The high-strength steel sheet of the present invention can be suitably used as structural members such as automotive parts. Background technique [0002] In order to reduce CO by reducing the weight of vehicles 2 New laws and regulations have been promulgated one after another due to the reduction in emissions and the improvement of crash resistance by reducing the weight of car bodies, and the enhancement of the strength of thin steel sheets for automobiles. Therefore, in order to increase the strength of the vehicle body, there are more and more cases where high-strength steel sheets having a tensile strength (TS) of 1180 MPa or higher are used in main structural members forming the frame of the vehicle body. [0003] High-strength steel s...

Claims

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Application Information

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IPC IPC(8): C22C38/00C21D9/46C22C38/06C22C38/60C22C18/00C22C18/04
CPCC22C18/04C22C18/00C21D9/46C22C38/06C22C38/60C21D2211/008C21D2211/001C22C38/38C22C38/04C22C38/02C22C38/001C22C38/14C22C38/12C22C38/002C22C38/18C22C38/16C22C38/08C22C38/008C22C38/005C21D8/0273C23C2/28C23C2/06C21D1/76C23C2/02C23C2/024C23C2/0224C22C38/58C21D8/0473C21D8/0226C21D8/0236C23C2/12C23G1/00C25D3/22C25D3/44
Inventor 南秀和田中裕二户畑润也横田毅
Owner JFE STEEL CORP
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