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High-strength hot-dip galvanized steel sheet having excellent moldability and shape fixability, and method for manufacturing same

A technology of hot-dip galvanized steel sheet and manufacturing method, which is applied in the direction of hot-dip galvanizing process, manufacturing tools, chemical instruments and methods, etc., which can solve the problems of reduced formability, not necessarily high absolute value of tensile flanging performance, and variable springback. Achieve the effect of excellent formability and shapeability

Active Publication Date: 2015-04-08
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, there is a problem that in general, as the strength of the steel plate increases, the springback after processing increases and the formability decreases.
However, the stretch flangeability has not been evaluated, and it cannot be said that it has sufficient processability
In Patent Document 3, both high strength and high ductility are achieved by utilizing tempered martensite, bainite, and retained austenite, but no mention is made of formability
In addition, the stretch flanging performance may not be very high as an absolute value, and there is room for improvement

Method used

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  • High-strength hot-dip galvanized steel sheet having excellent moldability and shape fixability, and method for manufacturing same
  • High-strength hot-dip galvanized steel sheet having excellent moldability and shape fixability, and method for manufacturing same
  • High-strength hot-dip galvanized steel sheet having excellent moldability and shape fixability, and method for manufacturing same

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Embodiment

[0087] Steels having the composition shown in Table 1 were smelted in a converter and continuously cast to produce steel slabs (in Table 1, N is an unavoidable impurity). These steel slabs were heated to 1200° C., rough-rolled and finish-rolled, and coiled at a coiling temperature of 400 to 650° C. to obtain hot-rolled sheets with a thickness of 2.3 mm. Next, a portion was softened at a temperature of 600° C. and a heat treatment time of 5 hours by batch processing, and after pickling, it was cold-rolled to a thickness of 1.4 mm to produce a cold-rolled steel sheet for annealing. Another part of the steel plate which was hot-rolled to a plate thickness of 2.3 mm was pickled and then directly used for annealing. Annealing is carried out through the continuous hot-dip galvanizing production line under the conditions shown in Table 2 and 3, immersed in a 460°C plating bath, and the adhesion amount is 35-45g / m 2 The coated layer was cooled at a cooling rate of 10°C / s to make hot-...

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Abstract

Provided is a high-strength hot-dip galvanized steel sheet having: a tensile strength (TS) no less than 1180 MPa; a total elongation (EL) no less than 14%; a hole expansion ratio (lambda) no less than 30%; and a yield ratio (YR) no greater than 70%, and having excellent moldability and shape fixability. Also provided is a method for manufacturing the high-strength hot-dip galvanized steel sheet. A high-strength hot-dip galvanized steel sheet having excellent moldability and shape fixability, characterized in having a component composition comprising, by mass, 0.10 to 0.35% of C, 0.5 to 3.0% of Si, 1.5 to 4.0% of Mn, 0.100% or less of P, 0.02% or less of S, and 0.010 to 0.5% of Al, with the remainder made up by Fe and unavoidable impurities; the microstructure containing, by area ratio, 0 to 5% of polygonal ferrite, 5% or more of bainitic ferrite, 5 to 20% of martensite, 30 to 60% of tempered martensite, and 5 to 20% of residual austenite; and the average particle diameter of prior austenite being no greater than 15 mum.

Description

technical field [0001] The present invention relates to a high-strength hot-dip galvanized steel sheet suitable for use as a steel sheet for automobiles and excellent in formability and shape fixability, and to 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 standpoint of protecting the global environment. For this reason, studies have been actively conducted to reduce the wall thickness by increasing the strength of vehicle body materials, and to improve fuel efficiency by reducing the weight of the vehicle body itself. Steel sheets that are formed into products by pressing and bending such as automobile parts require formability that can withstand processing while maintaining high strength. In Patent Document 1, both high strength and high workability are achieved by using tempered martensite and retained austenite. However, there is a problem that in gener...

Claims

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Application Information

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IPC IPC(8): C22C38/00C21D9/46C22C38/06C22C38/58C23C2/02C23C2/06C23C2/28
CPCC21D9/46C22C38/14C21D8/0205C22C38/002C23C2/02C23C2/28C23C2/06C23C2/285C22C38/12C21D1/20C22C38/04C21D2211/005C23C2/26C21D1/22C21D2211/008C22C38/06C22C38/02B32B15/013C21D8/0247C22C38/58C22C38/001C22C38/00Y10T428/12799C21D6/001C21D6/002C21D6/005C21D6/008C21D8/0226C21D8/0236C21D8/0263C22C38/005C22C38/08C22C38/16C22C38/38C23C2/29C23C2/024C23C2/0224C22C38/40C23C2/04
Inventor 长谷川宽金子真次郎长泷康伸
Owner JFE STEEL CORP
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