High-strength cold-rolled steel sheets, high-strength hot-dip galvanized steel sheets, and high-strength alloyed hot-dip galvanized steel sheets excellent in ductility, stretch-flangeability, and weldability
A cold-rolled steel plate, high-strength technology, applied in the direction of hot-dip coating process, heat treatment furnace, heat treatment equipment, etc., can solve problems such as weldability research, and achieve the effect of excellent stretch flangeability and excellent weldability
Active Publication Date: 2017-10-31
KOBE STEEL LTD
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Problems solved by technology
However, similar to the above-mentioned Patent Document 1, no study has been made on weldability.
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[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
The present invention provides a high-strength cold-rolled steel sheet having excellent ductility and stretch-flangeability in a region having a tensile strength of 980 MPa or more and a 0.2% yield strength of 700 MPa or more, and also has excellent weldability. In the high-strength cold-rolled steel sheet of the present invention, its chemical composition is appropriately adjusted, and in the 1 / 4 position of the thickness of the steel sheet, the area ratio of the following metal structure satisfies tempered martensite: 30 area % or more, bainite Tensite: 15 to 70 area%, the total of tempered martensite and bainite: 90 area%, ferrite: 0 to 5 area%, and retained austenite: 0 area % or more and 4 area % or less, and its ductility, stretch flangeability, and weldability are excellent, and it satisfies a tensile strength of 980 MPa or more and a 0.2% proof strength of 700 MPa or more.
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 that are excellent in ductility, stretch-flangeability, and weldability, and have 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...
Claims
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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