High strength hot rolled steel sheet and method for producing same

A technology of hot-rolled steel plate and manufacturing method, which is applied in the direction of manufacturing tools, metal rolling, heat treatment furnace, etc., can solve the problems such as the decrease of toughness, achieve the effects of improving hole expansion processability, reducing the weight of the car body, and ensuring safety

Inactive Publication Date: 2015-11-25
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] However, in general, the toughness decreases with the increase in the strength of the steel plate

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
Comparison scheme
Effect test

Embodiment approach 1

[0058] [Embodiment 1: Regarding resilience]

[0059] Hereinafter, Embodiment 1 will be described in detail.

[0060] First, the reasons for limiting the composition of the hot-rolled steel sheet according to the present invention will be explained. In addition,% which shows the following component composition means mass% unless otherwise stated.

[0061] C: 0.05%~0.18%

[0062] C increases the strength of steel and promotes the formation of bainite. Therefore, in the present invention, the C content needs to be 0.05% or more. On the other hand, if the C content exceeds 0.18%, the formation control of bainite becomes difficult, the formation of hard martensite increases, and the toughness of the hot-rolled steel sheet decreases. Therefore, the C content is set to 0.05% to 0.18%. It is preferably 0.08% to 0.17%, more preferably more than 0.10% and 0.16% or less. In addition, when the amount of Mn is 2.5% to 3.5%, the amount of C is preferably 0.06% to 0.15%.

[0063] Si: 1.0% or les...

Embodiment 1

[0129] The molten steel having the composition shown in Table 1 was smelted in a converter, and a billet (steel raw material) was produced by a continuous casting method. During continuous casting, steel sheets other than the hot-rolled steel sheet No. 1'of steel A1 in Tables 1 to 3 described later were subjected to electromagnetic stirring (EMS) for the treatment of reducing segregation of components. Next, these steel materials were heated under the conditions shown in Table 2, and subjected to hot rolling consisting of rough rolling and finish rolling under the conditions shown in Table 2. After finishing rolling, they were cooled under the conditions shown in Table 2. It was coiled at the coiling temperature shown in Table 2 to produce a hot-rolled steel sheet having a thickness shown in Table 2.

[0130] A test piece was collected from the obtained hot-rolled steel sheet, and the structure observation, tensile test, and Charpy impact test were performed. The tissue observat...

Embodiment approach 2

[0157] [Embodiment 2: Regarding hole reaming workability]

[0158] First, the reason for the composition limitation of the hot rolled steel sheet of the present invention will be explained. In addition, "%" indicating the content of each component element means "% by mass" unless otherwise specified.

[0159] C: more than 0.1% and less than 0.2%

[0160] C is an element that promotes the formation of bainite, increases the strength of steel, and promotes the formation of bainite, and is one of the important elements in the present invention. In order to obtain this effect, the C content needs to be greater than 0.1%. On the other hand, C combines with Fe to form cementite, so containing excessive C increases the number of cementites and shortens the distance between cementites that are the starting point of the voids, thereby reducing local ductility and expanding the hole. Sexual decline. In addition, containing more than 0.2% of excessive C reduces the weldability. Therefore, ...

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Abstract

This high strength hot rolled steel sheet has a composition that contains, in mass%, from 0.05% to 0.18% (inclusive) of C, 1.0% or less of Si, from 1.0% to 3.5% (inclusive) of Mn, 0.04% or less of P, 0.006% or less of S, 0.10% or less of Al, 0.008% or less of N, from 0.05% to 0.20% (inclusive) of Ti and more than 0.1% but 0.3% or less of V with the balance made up of Fe and unavoidable impurities. This high strength hot rolled steel sheet has a structure that contains a bainite phase as the main phase in an area ratio of more than 85%, while containing one or more phases selected from among a ferrite phase, a martensite phase and a residual austenite phase as the second phase in an area ratio of 0% or more but less than 15%. The average lath interval of the laths of the bainite phase is 400 nm or less, and the average length of long axes of the laths is 5.0 μm or less. This high strength hot rolled steel sheet has 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 suitable as a raw material for structural parts of automobiles, frameworks, truck frames, steel pipes, etc., with a tensile strength of 980 MPa or more. Background technique [0002] In recent years, from the viewpoint of protecting the global environment, automobile exhaust gas regulations (automobile exhaust gas regulations) are being strengthened. Under such circumstances, the improvement of the fuel consumption rate of automobiles such as trucks has become an important issue, and further high strength and thinning of the materials used are required. Along with this, in particular, high-strength hot-rolled steel sheets are actively used as raw materials for automotive parts. [0003] In addition, in accordance with the expectation to further reduce the construction cost of pipelines, reductions in steel pipe material costs are being sought. Therefore, as transportation pipes, instead...

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
CPCB21B3/00C21D8/02C21D9/46C22C38/00C22C38/02C22C38/04C22C38/06C22C38/14C22C38/58C21D8/0226C21D8/0263C21D8/0426C21D8/0463C21D2211/002C21D2211/003C21D1/02B21B1/22B21B2001/225C21D6/004C21D6/005C21D6/008C21D7/13C22C38/001C22C38/005C22C38/12C22C38/16C22C38/46C22C38/50C21D1/84C22C38/002
Inventor 山崎和彦中岛胜己上力
Owner JFE STEEL CORP
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