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High-tensile-strength hot-rolled steel sheet and method for producing same

A hot-rolled steel plate and high-tension technology, which is applied in the direction of manufacturing tools, metal rolling, chemical instruments and methods, etc., can solve problems such as component distortion, and achieve good processability and excellent material stability

Active Publication Date: 2014-07-16
JFE STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

In addition, if steel plates with different local strengths are press-formed, the amount of springback will change in proportion to the strength, and the parts will be distorted.

Method used

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

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Effect test

Embodiment

[0094] Molten steel having the composition shown in Table 1 was smelted and continuously cast by a generally known method to produce a billet (steel material) with a wall thickness of 250 mm. These billets were heated to 1250° C., rough rolling and finish rolling were performed, and after finish rolling, they were cooled and coiled to produce hot-rolled steel sheets with a thickness of 2.3 mm and a width of 1400 mm. Table 2 shows the finish rolling temperature, the average cooling rate of cooling (the average cooling rate from the finish rolling temperature to the coiling temperature) and the coiling temperature of the above-mentioned finish rolling.

[0095] Next, a part of the hot-rolled steel sheets (hot-rolled numbers in Table 2: 3, 9, and 11) obtained as above were pickled to remove surface scale, and then annealed (annealing temperature: 680° C., Holding time: 120 seconds), dipped in a hot-dip galvanizing bath (bath composition: 0.1% Al-Zn, bath temperature: 480°C), form...

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Abstract

Provided are: a high-tensile-strength hot-rolled steel sheet provided with both high strength and favorable workability (stretch flangeability), and moreover has superior material uniformity; and a method for producing same. The hot-rolled steel sheet has a tensile strength of at least 780 MPa, and has: a composition containing, by mass%, at least 0.03% and less than 0.07% of C, no greater than 0.3% of Si, 0.5-2.0% inclusive of Mn, no greater than 0.025% of P, no greater than 0.005% of S, no greater than 0.0060% of N, no greater than 0.1% of Al, 0.07-0.11% inclusive of Ti, and at least 0.08% and less than 0.15% of V in a manner such that Ti and V satisfy 0.18 <= Ti + V <= 0.24 (Ti and V being the amount contained (mass%) of the respective elements), the remainder comprising Fe and unavoidable impurities; a matrix such that the area ratio of ferrite phase with respect to the total structure is at least 95%; and a structure such that minute carbides containing Ti and V and having an average grain size of less than 10 nm are dispersed / precipitated, and the volume ratio of the minute carbides with respect to the total structure is at least 0.0020.

Description

technical field [0001] The present invention relates to a tensile material suitable for raw materials such as transportation equipment parts such as automobile parts and structural parts, which has excellent processability, especially excellent stretch flangeability, and is also excellent in material stability and material uniformity. Strength (TS): High-tensile hot-rolled steel sheet above 780MPa and its manufacturing method. Background technique [0002] From the viewpoint of global environmental protection, in order to reduce CO 2 In terms of emissions, it is necessary to reduce the weight of the car body while maintaining the strength of the car body, thereby improving the fuel efficiency of the car, which has become a very important issue in the automotive industry. In order to reduce the weight of an automobile body while maintaining its strength, it is effective to increase the strength of a steel sheet used as a raw material for automobile parts to reduce the thickn...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00B21B1/26C21D9/46C22C38/14C22C38/60
CPCC21D9/46C22C38/14B32B15/013C22C18/04C22C38/001C22C38/02C22C38/04C22C38/06C22C38/12C21D8/0426C21D8/0463C21D8/0478C21D2211/004C21D2211/005Y10T428/12799C22C38/00C23C2/024C23C2/02C23C2/0224C22C38/60C21D8/0263C22C38/002C22C38/008C22C38/08C22C38/10C22C38/16C22C38/24C22C38/26C22C38/28
Inventor 有贺珠子船川义正森安永明
Owner JFE STEEL CORP
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