High-yield-ratio high-strength hot-dip galvanized steel sheet excellent in ductility and hole expandability and manufacturing method thereof
A technology of hot-dip galvanized steel sheet and manufacturing method, which is applied in the direction of chemical instruments and methods, manufacturing tools, hot-dip coating process, etc., can solve the problems of ductility and hole expandability reduction, and achieve fuel efficiency improvement, ductility and expansion Excellent porosity and great utility value
Active Publication Date: 2015-08-19
JFE STEEL CORP
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Problems solved by technology
However, there is concern that the ductility and hole expandability will decrease due to the high strength of the steel plate
Method used
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[0094] A steel having the composition shown in Table 1, the balance consisting of Fe and unavoidable impurities was melted in a converter and cast into billets by continuous casting. After heating the obtained slab to 1200°C, it was hot-rolled at the finish rolling exit side temperature shown in Table 2 until each sheet thickness was 2.3 to 3.2 mm, and coiled at the coiling temperature shown in Table 2. . Then, the obtained hot-rolled sheet is pickled, passed through a continuous hot-dip galvanizing production line, annealed under the conditions shown in Table 2, then hot-dip galvanized, and then carried out the alloying treatment of the conditions shown in Table 2, Thereby, a hot-dip galvanized steel sheet (alloyed hot-dip galvanized steel sheet, coating type in Table 3: GA) was obtained. Some hot-dip galvanized steel sheets (coating types in Table 3: GI) without alloying treatment were obtained. The hot-dip galvanizing bath uses a zinc bath containing Al: 0.14%, and the ba...
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Abstract
An object is to provide a galvanized steel sheet with high yield ratio having not only a tensile strength TS of 590 MPa or more but also excellent ductility and stretch flange formability and a method for manufacturing the steel sheet. A high-strength galvanized steel sheet with high yield ratio having excellent ductility and stretch flange formability, the steel sheet having a chemical composition containing, by mass%, C: 0.04% or more and 0.13% or less, Si: 0.9% or more and 2.3% or less, Mn: 0.8% or more and 2.4% or less, P: 0.1% or less, S: 0.01% or less, Al: 0.01 % or more and 0.1% or less, N:0.008% or less, and the balance being Fe and inevitable impurities and a microstructure including, in terms of area ratio, 94% or more of a ferrite phase and 2% or less of a martensite ferrite phase, wherein the mean grain size of ferrite is 10 µm or less, the Vickers hardness of ferrite is 140 or more, the mean grain size of carbide particles existing at the grain boundaries of ferrite is 0.5 µm or less, and the aspect ratio of carbide particles existing at the grain boundaries of ferrite is 2.0 or less.
Description
technical field [0001] The present invention relates to a high-yield-ratio high-strength hot-dip galvanized steel sheet suitable as a member used in the field of the automobile industry and having excellent ductility and hole expandability, and a method for producing the same. Background technique [0002] In recent years, due to increased awareness of the protection of the global environment, there has been a strong demand for improvements in fuel efficiency to reduce CO emissions from automobiles. 2 emissions. Along with this, there is an active movement towards reducing the weight of the vehicle body by increasing the strength of the vehicle body material to achieve thinner walls. However, there is concern that the ductility and hole expandability will decrease due to the increase in strength of the steel sheet. Therefore, development of a high-strength steel sheet having both high ductility and high hole expandability has been desired. In addition, from the viewpoint ...
Claims
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IPC IPC(8): C22C38/00C21D9/46C22C38/06C22C38/58C23C2/02C23C2/06C23C2/28C23C2/40
CPCC22C1/02Y10T428/12965C21D6/008C22C38/00B05D3/0218B05D3/12C23C2/40C22C38/06C21D2211/005C21D2211/008C21D6/005C21D9/46B32B15/013C22C38/001C22C38/02C22C38/04
Inventor 川崎由康中垣内达也金子真次郎长泷康伸福士惠介
Owner JFE STEEL CORP