High-strength cold-rolled steel sheet, high-strength hot-dip galvanized steel sheet, and high-strength hot-dip galvannealed steel sheet having excellent ductility, stretch-flangeability, and weldability

A technology of hot-dip galvanized steel sheet and cold-rolled steel sheet, applied in the field of high-strength cold-rolled steel sheet, can solve problems such as weldability research, and achieve the effects of excellent stretch flangeability and excellent weldability

Active Publication Date: 2016-11-09
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, similar to the above-mentioned Patent Document 1, no study has been made on weldability.

Method used

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  • High-strength cold-rolled steel sheet, high-strength hot-dip galvanized steel sheet, and high-strength hot-dip galvannealed steel sheet having excellent ductility, stretch-flangeability, and weldability
  • High-strength cold-rolled steel sheet, high-strength hot-dip galvanized steel sheet, and high-strength hot-dip galvannealed steel sheet having excellent ductility, stretch-flangeability, and weldability
  • High-strength cold-rolled steel sheet, high-strength hot-dip galvanized steel sheet, and high-strength hot-dip galvannealed steel sheet having excellent ductility, stretch-flangeability, and weldability

Examples

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Embodiment

[0119] The following examples are listed to illustrate the present invention more specifically, but the present invention is not limited by the following examples, and can also be implemented by appropriately adding changes within the scope of meeting the aforementioned and hereinafter-described gist, and these are also included in this document. within the technical scope of the invention.

[0120] Steel ingots having the compositions shown in Table 1 below were subjected to vacuum melting. Then, it heated to 1250 degreeC, and implemented hot rolling to plate thickness 2.8mm. The finishing temperature was 900°C, the average cooling rate from hot rolling finish rolling to coiling was 20°C / s, and the coiling temperature CT was the temperature shown in Table 2 and Table 3 below. Next, the obtained hot-rolled steel sheet was pickled, and then cold-rolled to a plate thickness of 2.0 mm. Then, in figure 1, Table 2, and Table 3 under the conditions shown in the heat treatment. F...

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Abstract

Provided is a high-strength cold-rolled steel sheet having excellent ductility and stretch-flangeability as well as weldability at a range in which the tensile strength is at least 980 MPa and the 0.2% yield strength is at least 700 MPa. In this high-strength cold-rolled steel sheet, the chemical composition is adjusted as appropriate, and the area ratio of the belowmentioned metal structure at a position of 1/4 sheet thickness in the steel sheet satisfies the following: at least 30 area% of tempered martensite; 15-70 area%, inclusive, of bainite; at least 90 total area% of tempered martensite and bainite; 0-5 area%, inclusive, of ferrite; and 0-4 area%, inclusive, of retained austenite. The high-strength cold-rolled steel sheet has excellent ductility, stretch-flangeability, and weldability, and has a tensile strength of at least 980 MPa and a 0.2% yield strength of at least 700 MPa.

Description

technical field [0001] The present invention relates to a high-strength cold-rolled steel sheet, a high-strength hot-dip galvanized steel sheet, and a high-strength alloyed hot-dipped steel sheet excellent in ductility, stretch-flangeability, and weldability, and having a tensile strength of 980 MPa or more and a 0.2% yield strength of 700 MPa or more Galvanized steel. Hereinafter, these steel sheets may be collectively referred to simply as high-strength steel sheets. Background technique [0002] In recent years, with the increase in the strength of members such as steel sheets for automobiles and steel sheets for conveyance machinery, workability such as ductility and stretch flangeability has decreased, making it difficult to press-form members of complex shapes. Therefore, for high-strength steel sheets, it is also required to provide the above-mentioned technology excellent in workability. In addition, the method of joining the above-mentioned members by spot welding...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C22C38/14C22C38/58C21D9/46
CPCC21D8/0236C21D8/0273C21D8/0278C21D9/46C21D2211/002C21D2211/008C23C2/28B32B15/013C22C38/002C22C38/08C22C38/12C22C38/16C22C38/26C22C38/28C22C38/32C22C38/38Y10T428/12799C22C38/14C21D2211/005C22C38/02C22C38/04C22C38/06C23C2/02C23C2/06C23C2/40C23C2/024C23C2/0224C22C38/58C22C38/00
Inventor 经泽道高中屋道治
Owner KOBE STEEL LTD
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