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Steel sheet and manufacturing method therefor

A manufacturing method and steel plate technology, applied in the direction of manufacturing tools, chemical instruments and methods, metal material coating technology, etc., can solve problems such as weld cracking, cracking, Zn intrusion, etc.

Active Publication Date: 2021-06-04
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0009] On the other hand, since a large amount of C and Si are added to this TRIP steel from the viewpoint of improving ductility, there is a problem that cracks tend to occur at welded parts
In the case of spot welding between Zn-plated steel sheets or between Zn-plated steel sheets and unplated cold-rolled steel sheets, Zn intrudes into the grain boundaries of the base metal to cause torsion near the weld nugget. cracked problem

Method used

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  • Steel sheet and manufacturing method therefor
  • Steel sheet and manufacturing method therefor
  • Steel sheet and manufacturing method therefor

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0190] Steels having the composition shown in Table 1 were processed under the conditions shown in Table 2-1 to manufacture steel sheets of the present invention and steel sheets of Comparative Examples. The plate thickness of the steel plate was 1.4 mm. It should be noted that the conditions shown in Table 2-1 do not include zinc plating treatment.

[0191] The steel structure was measured by the above-mentioned method. The measurement results are shown in Table 2-2.

[0192] JIS No. 5 tensile test pieces were collected from the produced steel sheets so that the direction perpendicular to the rolling direction became the tensile axis, and a tensile test was performed (based on JIS Z2241). TS and U.El are shown in Table 2-2.

[0193] In addition, the stretch flange formability was evaluated by a hole expansion test based on the Japan Iron and Steel Federation standard JFST1001. That is, after using a punching tool with a punch diameter of 10 mm and a die diameter of 10.3 m...

Embodiment 2

[0205] Cold-rolled steel sheets having the composition shown in Table 3 were treated under the annealing conditions shown in Table 4-1 to manufacture steel sheets of the present invention and steel sheets of comparative examples. The plate thickness of the steel plate was 1.4 mm.

[0206] In addition, some steel sheets (cold-rolled steel sheets) were further subjected to a hot-dip galvanizing treatment to obtain hot-dip galvanized steel sheets (GI). Here, the steel sheet is immersed in a zinc coating bath of 440° C. to 500° C. to perform hot-dip galvanizing treatment, and then, the amount of plating deposition is adjusted by gas wiping or the like. For the molten zinc plating, a zinc plating bath having an Al content of 0.10% or more and 0.22% or less is used. In addition, after the hot-dip galvanizing treatment, a part of the hot-dip galvanized steel sheet is subjected to an alloying treatment of galvanizing to obtain an alloyed hot-dip galvanized steel sheet (GA). Here, th...

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Abstract

Provided are a steel sheet and a manufacturing method therefor. The present invention provides a steel sheet having a specific component composition and a steel structure wherein: in terms of area ratio, 6-90% of ferrite and 10-94% of a structure comprising one or two or more of upper bainite, fresh martensite, tempered martensite, lower bainite, and residual gamma are contained; in terms of volume ratio, 3-15% of residual gamma is contained; the total area ratio SC-concentrated of a region serving as the upper bainite that has a C concentration of 0.6-1.3% and an adjacent region of which has a minor axis width of 0.7-10 mum, an aspect ratio of >2.0, and a C concentration of 0.07% or less is 0.1-5%; the total area ratio Sgamma Block of fresh martensite having a circle-equivalent particle diameter of 1.5-15 mum and an aspect ratio of 3 or less and / or residual gamma particles having a circle-equivalent particle diameter of 1.5-15 mum and an aspect ratio of 3 or less is 5% or less (including 0%); and the prior gamma grain size in a surface layer is 2-12 mum.

Description

technical field [0001] The present invention relates to a steel sheet that can be suitably applied to press forming applications used in automobiles, home appliances, etc. through a press forming process, and to a method for producing the same. Background technique [0002] In recent years, due to the further increase in the demand for lightweight automobile bodies, the application of high-strength steel plates in the skeleton parts and sheet parts of automobiles has continued to develop. However, when a high-strength steel sheet having a tensile strength (TS) of 980 to 1180 MPa class is used for automobile parts, it is easy to generate press cracks due to a decrease in ductility and a decrease in stretch flange formability. Therefore, the formability of the above-mentioned high-strength steel sheets is expected to be better than conventional ones. [0003] From such a background, TRIP steel in which residual γ is dispersed in the microstructure of the steel sheet has been ...

Claims

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Application Information

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IPC IPC(8): C22C38/00C21D9/46C22C38/06C22C38/60
CPCC22C38/06C22C38/60C21D2211/005C21D2211/002C21D2211/008C21D2211/001C21D9/48C21D8/0426C21D8/0463C21D8/0436C21D8/0473C21D1/19C21D1/25C23C2/06C21D1/20C22C38/02C22C38/04C22C38/12C22C38/14C22C38/16C23C2/02C23C2/28C23C2/40Y02P10/20C23C2/0224C22C38/001C22C38/42C22C38/44C22C38/46C22C38/50C21D8/0226B21C47/02C21D8/0236C21D8/0273B32B15/013C21D6/005C21D6/008C21D8/0205C21D8/0263C21D9/46C22C38/002C22C38/08
Inventor 小野义彦高岛克利户畑润也松井洋一郎
Owner JFE STEEL CORP
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