High-strength steel sheet and production method for same, and production method for high-strength galvanized steel sheet

A technology of high-strength steel sheet and manufacturing method, applied in manufacturing tools, hot-dip plating process, coating and other directions, can solve problems such as poor shape, reduced mass production efficiency, increased deviation, etc., and achieves high utilization value and improved fuel efficiency. , the effect of excellent ductility

Active Publication Date: 2017-04-19
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0006] However, the amount of shape change is estimated based on TS. Therefore, when the TS of the steel sheet fluctuates, the deviation between the predicted value of shape change and the actual amount of shape change increases, causing shape defects.
In addition, steel sheets with such poor shapes need to be corrected one by one by sheet metal processing after stamping, which significantly reduces mass production efficiency.

Method used

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  • High-strength steel sheet and production method for same, and production method for high-strength galvanized steel sheet
  • High-strength steel sheet and production method for same, and production method for high-strength galvanized steel sheet
  • High-strength steel sheet and production method for same, and production method for high-strength galvanized steel sheet

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Embodiment

[0171] The steel having the composition shown in Table 1 and the balance consisting of Fe and unavoidable impurities was smelted in a converter, and a billet was produced by a continuous casting method. The obtained steel slab was heated under the conditions shown in Table 2, and hot rolled to obtain a steel sheet. Then, the steel sheet is subjected to pickling treatment. Then, for Nos. 1-22, 24, 25, 28, 30, 31, 33, 35-40, 42, 44-56 shown in Table 2, the steel sheets were hot-rolled under the conditions shown in Table 2. Heat treatment. For Nos. 31, 33, 35-40, 42, 44, the hot-rolled sheet was subjected to pickling treatment after heat treatment.

[0172] Next, after cold rolling the steel sheet under the conditions shown in Table 2, the steel sheet was subjected to two or three annealing treatments under the conditions shown in Table 2 to obtain a high-strength cold rolled steel sheet (CR).

[0173] Furthermore, a part of the high-strength cold-rolled steel sheet (CR) is galvani...

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Abstract

The present invention provides a high-strength steel sheet having a tensile strength (TS) of at least 780 MPa, excellent ductility and stretch flangeability, and excellent material-quality stability, achieved by: having a specific component composition; the steel structure having, in terms of area ratio, a total of ferrite and bainitic ferrite of 25-80%, and 3-20% martensite, and having, in terms of volume fraction, at least 10% retained austenite; the average crystalline particle diameter of the retained austenite being not more than 2[mu]m; the average Mn volume (mass%) in the retained austenite being at least 1.2 times the Mn volume (mass%) in the steel; and the area ratio of retained austenite that has an average C volume (mass%) of at least 2.1 times the C volume (mass%) of the steel being at least 60% of the area ratio of the total retained austenite.

Description

Technical field [0001] The present invention relates to a high-strength steel sheet with excellent formability, mainly suitable for structural members of automobiles, and a method for manufacturing the same. In particular, it is necessary to obtain a tensile strength (TS) of 780 MPa or more, excellent ductility, and excellent stretch flangeability. , And high-strength steel plate with excellent material stability. Background technique [0002] In recent years, in order to ensure the safety of the crew in the event of a collision and improve the fuel efficiency brought about by the weight reduction of the car body, the application of high-strength steel plates with a tensile strength (TS) of 780MPa or more and a thinner plate is being actively promoted. For the dynamics of automotive structural components. [0003] Furthermore, recently, the application of extremely high-strength steel sheets with 980 MPa class and 1180 MPa class TS has been studied. [0004] However, in general, in...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D9/46C22C38/04C22C38/60C22C18/04
CPCC22C18/04C22C38/00C22C38/04C22C38/60C21D8/0205C21D8/0226C21D8/0236C21D8/0263C21D8/0273C22C38/001C22C38/02C22C38/06C21D2211/001C21D2211/002C21D2211/005C21D2211/008C23C2/02C21D9/46C21D6/005C21D6/008C21D8/0278C22C38/002C22C38/005C22C38/008C22C38/12C22C38/14C22C38/16C22C38/38C23C2/06C23C2/024C23C2/0224C23F17/00
Inventor 川崎由康松田广志小幡美绘金子真次郎横田毅濑户一洋
Owner JFE STEEL CORP
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