High-strength cold-rolled steel sheet and manufacturing method thereof
A technology of cold-rolled steel sheet and manufacturing method, applied in manufacturing tools, chemical instruments and methods, metal material coating process, etc., can solve problems such as low yield ratio
Active Publication Date: 2021-05-28
JFE STEEL CORP
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Problems solved by technology
The steel sheet described in Patent Document 2 also has a steel structure of bainite and martensite as described above, and has high strength and excellent bendability. However, in the disclosed examples, it contains 27% or more of ferrite. Therefore, the yield ratio is as low as less than 0.65
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[0096] The present invention is specifically described with reference to examples.
[0097] 1. Manufacture of steel plates for evaluation
[0098] Steel having the composition shown in Table 1, with the balance consisting of Fe and unavoidable impurities was melted in a vacuum melting furnace, and then billet rolled to obtain a billet rolled material with a thickness of 27 mm. The obtained billet-rolled material was hot-rolled to a plate thickness of 4.0 mm. The conditions for hot rolling were to set the billet heating temperature to 1250° C., and perform hot rolling under the conditions shown in Table 2. Next, the hot-rolled steel sheets were ground, and cold-rolled under the conditions shown in Table 2 to manufacture cold-rolled steel sheets. Next, the cold-rolled steel sheets obtained above were heat-treated (annealed) under the conditions shown in Table 2 to manufacture annealed cold-rolled steel sheets (high-strength cold-rolled steel sheets). It should be noted that, ...
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Abstract
Provided are a high-strength cold-rolled steel sheet having a high yield ratio and excellent bendability, and a method of manufacturing the same. A high-strength cold-rolled steel sheet containing, in mass %, C: 0.12% to 0.25%, Si: less than 0.5%, Mn: 2.0% to 3.0%, P: 0.05%, and S: 0.005% or less, Al: 0.01% or more and 0.10% or less, N: 0.010% or less, and the balance is composed of Fe and unavoidable impurities. In terms of area ratio, martensite and tempered martensite satisfy the total 20% to 90%, ferrite is 10% and bainite is 10% to 80%, and the area ratio of island martensite in bainite is 1% to 10%. The area ratio of cementite having an average grain size of 1 μm or less in bainite is 0.1% to 5.0% inclusive.
Description
technical field [0001] It relates to a high-strength cold-rolled steel sheet used for automobile parts and the like, and a manufacturing method thereof. More specifically, the present invention relates to a high-strength cold-rolled steel sheet having a high yield ratio and excellent bendability, and a method for producing the same. Background technique [0002] In recent years, improving the fuel efficiency of automobiles has become an important issue from the viewpoint of protecting the global environment. Along with this, there has been an active trend to reduce the thickness of the steel plates used for the vehicle body and reduce the weight of the vehicle body itself by increasing the strength of the steel plate used for the vehicle body. In addition, in addition to the high strength of the steel plate used in the vehicle body, safety is also required for the components used in the frame of the vehicle body, and in order to improve the crash performance, it is advantag...
Claims
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IPC IPC(8): C22C38/00C21D9/46C22C38/06C22C38/58
CPCC21D9/46C22C38/06C22C38/001C22C38/02C22C38/04C22C38/08C22C38/12C22C38/14C22C38/16C22C38/18C21D8/0226C21D8/0236C21D8/0263C21D8/0273C21D2211/008C21D2211/005C21D2211/002C21D2211/003C21D6/005C23C2/02C23C2/0224B32B15/013C21D6/008C21D8/0205C21D8/0278C21D2211/001C22C38/002C22C38/005C22C38/28C22C38/32C22C38/38C23C2/06C23C2/40
Inventor 平岛拓弥吉富裕美
Owner JFE STEEL CORP