Steel sheet

a technology of steel sheets and spherical sheets, applied in the field of steel sheets, can solve the problems of mechanical properties and failure to obtain a sufficient reaction force characteristic, and achieve the effect of stable yield strength

Inactive Publication Date: 2018-08-23
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0060]According to the present invention, it is possible to obtain a stable yield strength even after paint baking because the average dislocation density in ferrite, the average dislocation density in bainite, and the like are appropriate.

Problems solved by technology

However, the DP steel sheet and the TRIP steel sheet have a problem that their mechanical properties after paint baking sometimes vary in a member.
In this case, the portion with less strain applied thereto is soft and a break occurs in this portion, to thus fail to obtain a sufficient reaction force characteristic and crashworthiness.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example

[0121]Next, there will be explained examples of the present invention. Conditions of the examples are condition examples employed for confirming the applicability and effects of the present invention, and the present invention is not limited to these condition examples. The present invention can employ various conditions as long as the object of the present invention is achieved without departing from the spirit of the invention.

[0122](First test)

[0123]In the first test, steels having chemical compositions illustrated in Table 1 were melted to manufacture steel billets, and these steel billets were heated to 1200° C. to 1250° C. to be subjected to hot rolling. In the hot rolling, rough rolling and finish rolling were performed. Each blank space in Table 1 indicates that the content of a corresponding element was less than a detection limit, and the balance is Fe and impurities. Each underline in Table 1 indicates that a corresponding numerical value is outside the range of the prese...

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Abstract

A steel sheet includes: a predetermined chemical composition; and a steel structure containing, in are a fraction, 2% or more of ferrite and bainite, in which an average dislocation density in the ferrite and an average dislocation density in the bainite are both h3×1012 m/m3 to 1×1014 m/m3, and an average grain diameter of the ferrite and the bainite is 5 μm or less.

Description

TECHNICAL FIELD[0001]The present invention relates to a steel sheet capable of obtaining an excellent crashworthiness suitable for an automobile member.BACKGROUND ART[0002]In the case of manufacturing an automotive vehicle body using a steel sheet, molding, welding, and paint baking of the steel sheet are performed generally. Thus, the steel sheet for automobile is required to have excellent formability, a high strength after paint baking, and an excellent crashworthiness. As a steel sheet used for an automobile, conventionally, a dual phase (DP) steel sheet having a dual phase structure of ferrite and martensite and a transformation induced plasticity (TRIP) steel sheet have been cited.[0003]However, the DP steel sheet and the TRIP steel sheet have a problem that their mechanical properties after paint baking sometimes vary in a member. That is, in molding of the steel sheet, strain is applied according to the shape of a member to be obtained, and thus the molded steel sheet includ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C21D9/46C22C38/32C22C38/28C22C38/16C22C38/14C22C38/12C22C38/08C22C38/06C22C38/04C22C38/02C22C38/00C21D8/02C23C2/02C23C2/40C23F17/00C25D5/36
CPCC21D9/46C22C38/32C22C38/28C22C38/16C22C38/14C22C38/12C22C38/08C22C38/06C22C38/04C22C38/02C22C38/008C22C38/005C22C38/002C22C38/001C21D8/0226C21D8/0236C21D8/0263C21D8/0278C23C2/02C23C2/40C23F17/00C25D5/36C21D2211/005C21D2211/002C21D2211/008C22C38/00C22C38/58C23C2/024C23C2/0224
Inventor OKAMOTO, RIKIKAWATA, HIROYUKIAZUMA, MASAFUMIUENISHI, AKIHIROMARUYAMA, NAOKI
Owner NIPPON STEEL CORP
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