Process for manufacturing high-strength hot-rolled steel sheet

A technology of hot-rolled steel sheet and manufacturing method, which is applied in the field of manufacturing high-strength hot-rolled steel sheet, can solve problems such as difficulty in applying the coiling process, achieve excellent stretch flangeability, and suppress the generation of local low-temperature parts

Active Publication Date: 2010-06-23
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, this technology is applied to thick steel plates with a plate thickness greater than 10 mm, and it is difficult to apply to thin steel plates with a plate thickness of less than 10 mm, which have a coiling process, and are generally mainly used for plate thicknesses below 8 mm.

Method used

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  • Process for manufacturing high-strength hot-rolled steel sheet
  • Process for manufacturing high-strength hot-rolled steel sheet

Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0062] The steel slabs with the chemical compositions shown in Table 1 were hot-rolled under the hot rolling and cooling conditions shown in Table 2 to produce hot-rolled sheets with a thickness of 3.2 mm. Here, air cooling is performed during the cooling stop period after the cooling after finish rolling. Then, the above-mentioned hot-rolled sheet is subjected to a usual pickling treatment. In addition, a radiation thermometer (manufactured by NEC Sanei Co., Ltd., model: TH7800) capable of two-dimensionally measuring the surface temperature of the steel plate was installed in front of the coiling device to measure the presence or absence of local temperature deviation of the steel plate. A usual pickling treatment is performed on the above-mentioned hot-rolled sheet.

[0063] In addition, regarding the cooling after air cooling shown in Table 1, an experiment was conducted separately, and it was confirmed that it passed 2000 L / min·m 2 Above the water flux density nucleate b...

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Abstract

The invention provides a process for manufacturing a high -strength steel sheet which has a strength of 490MPa or above and excellent stretch flange formability with a hole enlargement ratio of 80% or above after 10% working and which is reduced in the local property variation in a coil. A process for manufacturing a high-strength hot-rolled steel sheet, characterized by heating a billet which contains by mass C: 0.05 to 0.15%, Si: 0.1 to 1.5%, Mn: 0.5 to 2.0%, P: 0.06% or below, S: 0.005% or below, and Al: 0.10% or below with the balance consisting of Fe and unavoidable impurities to 1150 to 1300 DEG C, subjecting the resulting billet to hot rolling with a finishing temperature of 800 to 1000 DEG C, cooling the obtained sheet at an average cooling rate of 30 DEG C/s or above to a cooling stop temperature of 525 to 625 DEG C, stopping the cooling of the sheet for 3 to 10seconds, cooling the resulting sheet by such a cooling method as to cause nucleate boiling, and then coiling the sheet at 400 to 550 DEG C.

Description

technical field [0001] The present invention relates to a method for manufacturing a high-strength hot-rolled steel sheet having a tensile strength of 490 MPa or more, which is excellent in stretch-flangeability after processing as a raw material for automotive components and has a small local characteristic change in a coil. Background technique [0002] In recent years, interest in environmental issues has increased, and further high-strength and thinner steel sheets for automobiles have been demanded for the purpose of improving mileage through weight reduction. Although the most commonly used high-strength hot-rolled steel sheet is 440 MPa grade, due to the above reasons, recently, the usage of steel sheet of 490 MPa grade or higher, especially 590 MPa grade, is increasing. However, since the elongation rate and stretch-flange characteristics decrease with increasing strength, there arises a big problem of cracks during press working and a decrease in yield. [0003] On...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21D9/46C21D8/02C22C38/06C22C38/14
CPCC21D8/0426C21D8/0463C21D1/20C22C38/02C21D9/48C22C38/04C21D2211/005C21D2211/002
Inventor 横田毅濑户一洋上冈悟史西浦伸夫富永阳一
Owner JFE STEEL CORP
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