Steel sheet and manufacturing method therefor

A steel plate and residual technology, applied in the direction of manufacturing tools, furnaces, heat treatment equipment, etc., can solve the problems of stamping cracks, ductility decrease, stretch flange formability decrease, 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

However, when high-strength steel sheets of the 980-1180 MPa class are used for automotive parts, stamping cracks are likely to occur due to decreased ductility and decreased stretch-flange formability

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

[0234] Cold-rolled steel sheets with a thickness of 1.2 mm having the compositions shown in Table 1 were treated under the annealing conditions shown in Table 2-1 to manufacture steel sheets of the present invention and steel sheets of comparative examples.

[0235]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, the alloying treatment of t...

Embodiment 2

[0250] A cold-rolled steel sheet with a thickness of 1.2 mm having the composition shown in Table 1 was treated under the annealing conditions shown in Table 3-1 to manufacture the steel sheet of the present invention and the steel sheet of the comparative example. The measurement of the steel structure and the evaluation of the mechanical properties of the obtained steel sheets were performed by the same method as above, and the results are shown in Table 3-2. It should be noted that the plate-shaped residual γ formed adjacent to the upper bainite UB The area ratio of S γUB Come and find out.

[0251] In the examples of the present invention of No.1, 2, 3, and 7, the excellent uniform elongation (ductility) of 9% or more is satisfied under the condition of TS: 780-1319MPa level, and (TS×U.El-7000 )×λ≧260000MPa%, pore expandability (λ) of 30% or more, under the condition of TS: 1320MPa level or more, satisfying the excellent uniform elongation (ductility) of 8% or more, sati...

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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, at most 5% of ferrite and 95-100% 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, 5-20% of residual [gamma] is contained; the area ratio S[gamma] UB of residual [gamma]UB having a particle width of 0.25-0.60 [mu]m, a particle length of 1.0-15 [mu]m, and an aspect ratio of 3.1-25 is 0.2-7.0%; the number of distributed particles N[gamma] LB of residual [gamma]LB having a particle width of 0.08-0.24 [mu]m, a particle length of 0.6-15 [mu]m, and an aspect ratio of 4-40 is 10-120 particles per 100 [mu]m2; the total area ratio S[gamma] Fine of fresh martensite having a circle-equivalent particle diameter of 0.5 [mu]m or more and less than 1.3 [mu]m and an aspect ratio of 3 or less and / or residual [gamma] particles having a circle-equivalent particle diameter of 0.5 [mu]m or more and less than 1.3 [mu]m and an aspect ratio of 3 or less is 1-10%; and the total area ratio S[gamma] Block of fresh martensite having a circle-equivalent particle diameter of 1.5-20 [mu]m and an aspect ratio of 3 or less and / or residual [gamma] particles having a circle-equivalent particle diameter of 1.5-20 [mu]m and an aspect ratio of 3 or less is 5% or less (including 0%).

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 980-1180MPa high-strength steel plates in the skeleton parts and sheet parts of automobiles has continued to develop. However, when a high-strength steel sheet of 980 to 1180 MPa class is used for automobile parts, the ductility decreases and the stretch flange formability decreases, so that press cracking tends to occur. 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 developed as a techniqu...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21D9/46C22C38/00C22C38/06C22C38/60
CPCC22C38/06C22C38/60C21D1/19C21D1/25C21D1/28C21D9/48C21D6/001C21D6/002C21D6/005C21D6/008C21D8/0473C21D2211/002C21D2211/008C22C38/02C22C38/04C22C38/22C22C38/26C22C38/28C22C38/32C21D1/20C21D1/22Y02P10/20C22C38/001C22C38/14C22C38/42C22C38/44C22C38/46C22C38/48C22C38/50C21D9/46C21D8/0226C21D8/0236C21D8/0273C21D8/0205C21D8/0263C21D2211/005C22C38/002C22C38/12C22C38/54C22C38/58
Inventor 小野义彦户畑润也秋元浩幸松井洋一郎金子真次郎
Owner JFE STEEL CORP
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