High-strength hot-dip galvanized steel sheet and method for producing the same
A technology of hot-dip galvanized steel sheet and manufacturing method, applied in hot-dip galvanizing process, manufacturing tools, chemical instruments and methods, etc., can solve problems such as ignorance, and achieve high value, excellent elongation, and excellent V-bendability. Effect
Active Publication Date: 2016-01-20
NIPPON STEEL CORP
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Problems solved by technology
[0007] However, at present, even higher strength and workability are required for high-strength steel sheets, but no technology is known that satisfies these requirements and balances elongation and V-bendability at a sufficiently high level.
Method used
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Comparison scheme
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Embodiment
[0098] Hereinafter, the present invention will be described in detail based on examples.
[0099] Manufacture steel with the composition shown in Table 1, heat it to 1200°C after cooling and solidification, carry out finish rolling at 880°C, and cool to 550°C at an average cooling rate of 60°C / second after cooling, and then in Table 2 Coiling is performed at the coiling temperature. Then, 50% cold rolling was performed on this hot-rolled sheet. Then, annealing treatment was performed under the conditions shown in Table 2 by continuous annealing.
[0100] Assuming the effects of roll diameter, tension, and number of passes in repeated bending during overaging (OA) treatment in an actual production line, multiple different curvatures, tensions, and passes were given during OA of annealing treatment, and the effect on residual stress was evaluated. influences.
[0101] Table 1
[0102] Steel No.
C
Si
mn
0
P
S
N
AI
AI+Si
other ...
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Abstract
The invention provides a high-strength hot-dip galvanized steel sheet, which contains main components, and furthermore, in terms of mass %, the steel plate is defined as the main phase of ferrite at 40% or more in terms of volume fraction, and contains 8% to 60% of Retained austenite, the remaining structure is formed by one or more of bainite, martensite, and pearlite. In this high-strength hot-dip galvanized steel sheet, the austenite grains located in the range where the average residual stress σR of the austenite grains satisfies the formula (1) is specified to be 50% or more, and the surface of the steel sheet has a hot-dip galvanized A galvanized layer, the hot-dip galvanized layer contains less than 7% by mass of Fe, and the remainder is composed of Zn, Al, and unavoidable impurities. -400MPa≤σR≤200MPa (1).
Description
technical field [0001] The present invention relates to a hot-dip galvanized steel sheet having excellent bendability and high strength (for example, a tensile strength of 980 MPa or more) used in structural parts for automobiles and a method for producing the same. Background technique [0002] For the purpose of improving fuel efficiency and crash safety of automobiles, the application of high-strength tempering to car body skeleton structures is promoted. On the other hand, since the strength of materials increases, the formability of materials decreases. Steel sheets are required to achieve both high press workability and strength. [0003] Among high-strength steel sheets, it is known that retained austenitic steel having retained austenite in the steel structure utilizes the TRIP effect and has very high elongation despite high strength. In this retained austenite steel, in order to further increase the elongation, for example, Patent Document 1 discloses that while e...
Claims
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IPC IPC(8): C22C38/00B21B3/00C21D9/46C22C18/04C22C38/06C22C38/58C23C2/02C23C2/06C23C2/28
CPCC23C2/02C23C2/28C21D9/46C22C18/04B32B15/013C22C38/001C22C38/002C22C38/02C22C38/04C23C2/26C23C2/40C21D8/0205C21D8/0284C21D2211/001C21D2211/005C22C18/00C22C38/005C22C38/12C22C38/14C22C38/38Y10T428/12799C21D8/0226C23C2/06C22C38/06C23C2/29C23C2/0224C22C38/58C21D8/0426C21D8/0436C23C2/024
Inventor 佐藤浩一山中晋太郎藤田宗士
Owner NIPPON STEEL CORP