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High strength hot rolled steel sheet and manufacturing method for same

A technology for hot-rolled steel sheets and a manufacturing method, which can be applied to manufacturing tools, heat treatment furnaces, heat treatment equipment, etc., and can solve problems such as reduction in punching properties and hole expandability.

Inactive Publication Date: 2018-03-27
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, in general, as the strength of the steel sheet increases, punchability and hole expandability decrease

Method used

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

Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0142] Molten steel having the composition shown in Table 1 was melted in a converter, and a slab (steel raw material) was produced by a continuous casting method. During continuous casting, electromagnetic stirring (EMS) was performed for reducing segregation of components in hot-rolled steel sheets other than hot-rolled steel sheet Nos. 22 and 23 (steel K) in Tables 2 and 3 described later. Next, these steel raw materials were heated under the conditions shown in Table 2, and hot rolling including rough rolling and finish rolling under the conditions shown in Table 2 was performed. After finish rolling, the cooling start time (time from finish rolling to start cooling (forced cooling)) and average cooling rate (average cooling rate from finish rolling end temperature to coiling temperature) under the conditions shown in Table 2 ) cooling, and coiled at the coiling temperature of the conditions shown in Table 2 to make hot-rolled steel sheets with the thickness shown in Table...

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Abstract

Provided is a high strength hot rolled steel sheet having superior punchability and hole expandability and a tensile strength TS of at least 980 MPa and a manufacturing method for same. The high strength hot rolled steel sheet has a structure with specified amounts of C, Si, Mn, P, S, Al, N, Ti, Cr and B as a component composition and that comprises a main phase that is a bainite phase with an area ratio of at least 85%, a second phase that is a martensite phase or a martensite-austenite mixed phase with an area ratio of at most 15% and a ferrite phase that is the remainder, wherein the average grain size in the second phase is at most 3.0 [mu]m and furthermore, the average aspect ratio of the prior austenite grains is 1.3-5.0 and the area ratio of recrystallized prior austenite grains tounrecrystallized prior austenite grains is at most 15%, and wherein deposits under 20 nm in diameter are at most 0.10 mass%.

Description

technical field [0001] The present invention relates to a high-strength hot-rolled steel plate with a tensile strength TS of 980 MPa or more suitable for automobile structural parts, frame parts, running parts such as suspensions, and truck frame parts, and a manufacturing method thereof. Background technique [0002] In recent years, from the viewpoint of protecting the global environment, automobile exhaust regulations have been strengthened. Therefore, improving the fuel efficiency of automobiles has become an important issue. In addition, the materials used are required to be further strengthened and thinned. Along with this, high-strength hot-rolled steel sheets have been actively used as raw materials for automobile parts. Such high-strength hot-rolled steel sheets are used not only in structural parts and skeleton parts of automobiles, but also in running parts, truck frame parts, and the like. [0003] As such, the demand for high-strength hot-rolled steel sheets ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C21D9/46C22C38/38C22C38/60
CPCC22C38/02C22C38/04C22C38/06C22C38/001C22C38/28C22C38/32C22C38/34C22C38/38C22C38/60C22C38/26C22C38/24C22C38/22C22C38/20C22C38/42C22C38/44C22C38/46C22C38/48C22C38/50C22C38/54C22C38/58C22C38/002C22C38/005C21D8/0205C21D8/0226C21D6/002C21D6/004C21D6/005C21D6/008C21D2211/002C21D2211/008C21D2211/001C21D2211/005C21D9/46C22C38/00C21D8/0263C22C38/40C21D2211/004
Inventor 山崎和彦丰田俊介森安永明入佐健太郎
Owner JFE STEEL CORP
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