High strength hot rolled steel sheet and method for producing same

A hot-rolled steel sheet, high-strength technology, used in manufacturing tools, metal rolling, heat treatment furnaces, etc., can solve problems such as decreased bending workability, and achieve the effect of improving bending workability, excellent bending workability, and reducing vehicle body weight

Active Publication Date: 2015-12-09
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] However, with the increase in strength of steel sheets, bending workability generally decreases

Method used

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  • High strength hot rolled steel sheet and method for producing same
  • High strength hot rolled steel sheet and method for producing same
  • High strength hot rolled steel sheet and method for producing same

Examples

Experimental program
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Embodiment

[0098] A molten steel having a composition shown in Table 1 was melted using a converter, and a slab (raw material steel) was produced by a continuous casting method. For hot-rolled steel sheets other than hot-rolled steel sheet No. 1' of steel A in Tables 1 to 3 described later, electromagnetic stirring (EMS) was performed during continuous casting to perform a component segregation reduction treatment. Next, these raw material steels were heated / maintained under the conditions shown in Table 2, hot rolling including rough rolling and finish rolling under the conditions shown in Table 2 were implemented, and after the finish rolling was completed, they were cooled under the conditions shown in Table 2. , was coiled at the coiling temperature shown in Table 2 to produce a hot-rolled steel sheet with the thickness shown in Table 2.

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Abstract

Provided are: a high strength hot rolled steel sheet having a tensile strength of 980 MPa or more and excellent bending workability; and a method for producing the high strength hot rolled steel sheet. This high strength hot rolled steel sheet has a composition that contains more than 0.1% but 0.2% or less of C, from 0.5% to 3.0% (inclusive) of Si, from 1.0% to 3.5% (inclusive) of Mn, 0.05% or less of P, 0.004% or less of S, 0.10% or less of Al, 0.008% or less of N, from 0.05% to 0.15% (inclusive) of Ti and more than 0.10% but 0.30% or less of V with the balance made up of Fe and unavoidable impurities. This high strength hot rolled steel sheet is composed of surface layer regions having a structure wherein a ferrite phase forms the main phase and an inner region having a structure wherein a bainite phase forms the main phase. By setting the ratios of the surface layer regions in the thickness direction of the steel sheet to 1.0-5.0% (inclusive) of the total sheet thickness respectively from the front and back surfaces of the steel sheet, this high strength hot rolled steel sheet achieves a tensile strength (TS) of 980 MPa or more.

Description

technical field [0001] The present invention relates to a high-strength hot-rolled steel sheet having a tensile strength of 980 MPa or higher, which is suitable for use as a raw material for structural parts and frames of automobiles, and frames of trucks, and particularly relates to improvement of bending workability . Background technique [0002] In recent years, automobile exhaust regulations (automobile exhaust gas regulations) have been strengthened from the viewpoint of protecting the global environment. Under such circumstances, improvement of fuel efficiency of automobiles such as trucks has become an important issue, and further strengthening and thinning of materials used have been demanded. As a result, high-strength hot-rolled steel sheets have been actively used as raw materials for automobile parts, and their demand has been increasing year by year. In particular, a high-strength hot-rolled steel sheet having a tensile strength of 980 MPa or more is expected...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00B21B3/00C21D8/02C21D9/46C22C38/14C22C38/58
CPCB21B3/00C21D8/02C21D8/0226C21D8/0263C21D9/46C21D2211/002C21D2211/005C22C38/00C22C38/04C22C38/12C22C38/14C22C38/58C21D6/004C21D6/005C21D6/008C21D8/0205C22C38/001C22C38/002C22C38/005C22C38/02C22C38/06C22C38/16C22C38/46C22C38/50
Inventor 山崎和彦中岛胜己上力
Owner JFE STEEL CORP
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