High-strength steel sheet superior in formability

A steel plate, temperature zone technology, used in manufacturing tools, hot dipping processes, metal material coating processes, etc.

Inactive Publication Date: 2010-02-17
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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  • High-strength steel sheet superior in formability
  • High-strength steel sheet superior in formability
  • High-strength steel sheet superior in formability

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Embodiment Construction

[0011] The present invention relates to a technique for improving the workability of a steel plate with a composite structure of 590 to 780 MPa, which contains ferrite as a parent phase and hard phases such as martensite (M) and bainite (B) as a second phase structure ( low temperature phase transition).

[0012] Specifically, it is possible to obtain such a high-strength steel sheet as follows. For the structure, in particular, the following control is appropriately performed: control of the composition and ratio of the second phase structure; control of the hardness of the parent phase structure (specifically, iron The average hardness of the ferrite is controlled to be more than specified relative to the tensile strength of the steel plate, and the ratio of the average hardness of the ferrite as the parent phase to the average hardness of the bainite and martensite as the second phase structure is presented. Some are small); the refinement of the parent phase structure (ave...

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Abstract

Disclosed is a high-strength steel sheet which has a predetermined component composition, structurally has a ferrite matrix structure and bainitic and martensitic second phase structures, and has a ferrite fraction of from 50 to 86 percent by area, a bainite fraction of from 10 to 30 percent by area, and a martensite fraction of from 4 to 20 percent by area, relative to the entire structure, in which the bainite area fraction is larger than the martensite area fraction, the ferrite has an average grain size of 2.0 to 5.0 [mu]m, and the ratio of the average ferrite hardness (Hv) to the tensilestrength (MPa) of the steel sheet is equal to or more than 0.25. The steel sheet excels both in TS-EL balance and TS-[lambda] balance at high strengths on the order of 590 to 780 MPa.

Description

technical field [0001] The present invention relates to a high-strength steel sheet having high workability such as elongation and stretch-flangeability, and a tensile strength of 590 to 780 MPa. The high-strength steel sheet of the present invention is useful as a high-strength steel sheet constituting a base material (raw material) of a hot-dip galvanized steel sheet and an alloyed hot-dip galvanized steel sheet, and is suitable for, for example, structural members for automobiles requiring high workability (such as pillars, frames, etc.) skeletal components such as body parts and reinforcements, strength components such as bumpers, door anti-collision strips, panel parts, and underbody parts) and components for home appliances. Background technique [0002] From the standpoint of collision safety and global environmental protection (improvement of fuel efficiency), members used in automobiles and the like are required not only to have high strength and high ductility (elo...

Claims

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Application Information

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IPC IPC(8): C22C38/14C22C38/28C22C38/38C21D9/46C23C2/06
CPCC21D8/0426C22C38/04C22C38/14C21D2211/008C21D1/26C21D8/0226C21D8/0447C21D6/005C22C38/12C21D2211/005C21D8/0436C21D2211/002
Inventor 渡边圣子
Owner KOBE STEEL LTD
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