High-strength steel sheet excellent in ductility and low-temperature toughness and method for producing the same
A high-strength steel plate and low-temperature toughness technology, which is applied in the manufacture of tools, coatings, furnace types, etc., can solve the problems of poor low-temperature toughness of steel plates, without consideration of low-temperature toughness, etc., and achieve the effect of excellent ductility and low-temperature toughness
Active Publication Date: 2017-06-23
KOBE STEEL LTD
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Problems solved by technology
[0004] In addition to the above characteristics, it is also required to improve the low-temperature toughness of high-strength steel sheets in order to improve the crash safety at low temperatures, but it is known that the low-temperature toughness of TRIP steel sheets is poor, and in fact, no consideration has been given to low-temperature toughness
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[0217] Below, the present invention is described in more detail by enumerating the examples, but the present invention is not limited by the following examples, and of course it can also be implemented by adding appropriate changes within the scope of the above and the following contents, and these are also included in this document. within the technical scope of the invention.
[0218] Steels with the chemical composition shown in Table 1 below (with the balance being iron and inevitable impurities other than P, S, N, and O) were subjected to vacuum melting to manufacture experimental slabs. In Table 1 below, the REM uses misch metal containing about 50% of La and about 30% of Ce.
[0219] Ac was calculated based on the chemical composition shown in Table 1 below and the above formula (a). 3 The Ms point was calculated based on the chemical components shown in Table 1 below and the above formula (b).
[0220] The obtained slabs for experiments were hot-rolled, then cold-rol...
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Abstract
The high-strength steel sheet of the present invention is a steel sheet satisfying a specified composition, the metal structure of the steel sheet includes polygonal ferrite, bainite, tempered martensite, and retained austenite each having a specified area ratio, and, The distribution represented by each average IQ obtained from the specified crystal grains by the electron backscatter diffraction method satisfies the following formulas (1) and (2). According to the present invention, it is possible to realize a high-strength steel sheet having excellent ductility and low-temperature toughness even in the high-strength region of 780 MPa or more. (IQave-IQmin) / (IQmax-IQmin)≥0.40(1)σIQ / (IQmax-IQmin)≤0.25(2).
Description
technical field [0001] The present invention relates to a high-strength steel sheet having a tensile strength of 780 MPa or more and excellent in ductility and low-temperature toughness, and a method for producing the same. Background technique [0002] In the automotive industry, CO 2 Countermeasures against global environmental problems, such as emission control, are urgently needed. On the other hand, from the viewpoint of ensuring the safety of passengers, collision safety standards for automobiles are being strengthened, and structural designs that can sufficiently ensure safety in the passenger space are being carried out. In order to meet these requirements at the same time, it is effective to use high-strength steel sheets with a tensile strength of 780 MPa or more as structural members of automobiles, and further reduce the thickness of the steel sheets to reduce the weight of the vehicle body. However, in general, if the strength of a steel sheet is increased, th...
Claims
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IPC IPC(8): C22C38/00C21D9/46C22C38/60
CPCC22C38/00C21D8/0205C21D8/0247C21D2211/001C21D2211/002C21D2211/005C21D2211/008C22C38/18C23C2/02C23C2/28C23C2/06C21D9/46C22C38/001C22C38/002C22C38/005C22C38/02C22C38/04C22C38/06C22C38/08C22C38/12C22C38/14C22C38/16C22C38/38C23C2/29C23C2/024C23C2/0224
Inventor 粕谷康二村田忠夫水田纱江二村裕一
Owner KOBE STEEL LTD