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Ultrahigh-strength thin steel sheet

An ultra-high-strength, thin-steel technology, applied in the direction of furnace types, furnaces, heat treatment furnaces, etc., can solve the problems that active countermeasures for hydrogen embrittlement have not been considered

Active Publication Date: 2009-01-21
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In addition, from the standpoint of workability and weldability, since steel sheets above 780MPa are not used so much, active countermeasures against so-called hydrogen embrittlement have not been considered

Method used

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  • Ultrahigh-strength thin steel sheet
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  • Ultrahigh-strength thin steel sheet

Examples

Experimental program
Comparison scheme
Effect test

Embodiment

[0237] Next, first and second examples according to the first embodiment of the present invention will be described.

no. 1 example

[0239] After the steels (steel types A to V) whose component compositions are shown in Table 1 were vacuum-melted to form thick plates, according to the following procedure (hot rolling→cold rolling→continuous annealing), hot plates with a plate thickness of 3.2 mm were obtained The steel sheets were rolled, followed by acid washing to remove surface scale, followed by further cold rolling to 1.2 mm, and further continuous annealing as shown below, thereby preparing various steel sheets (Experiment Nos. 1 to 23).

[0240]

[0241] Start temperature: 30 minutes at 1150 to 1250°C

[0242] Final temperature: 850℃

[0243] Cooling rate: 40℃ / s

[0244] Coiling temperature: 550℃

[0245]

[0246] Cold rolling rate: 50%

[0247]

[0248] After cold rolling, the steel sheets of Experiment Nos. 1 to 15, 17 to 19 and 21 to 23 were 3 point (see Table 1) to Ac 3 The temperature in the range of point +30°C was held for 120 seconds, followed by quenching (air cooling) at an avera...

no. 2 example

[0283] After the steels (steel types 1 to 22) whose component compositions are shown in Table 5 were vacuum-melted to form thick plates, according to the following procedure (hot rolling→cold rolling→continuous annealing), hot plates with a plate thickness of 3.2 mm were obtained The steel sheets were rolled, followed by acid washing to remove surface scale, followed by further cold rolling to 1.2 mm, and further continuous annealing as shown below, thereby preparing various steel sheets (Experiment Nos. 24 to 46).

[0284]

[0285] Start temperature: 30 minutes at 1150 to 1250°C

[0286] Final temperature: 850℃

[0287] Cooling rate: 40℃ / s

[0288] Coiling temperature: 550℃

[0289]

[0290] Cold rolling rate: 50%

[0291]

[0292] The steel sheets of Experiment Nos. 24 to 42, 44 and 45 were treated in such a way that the cold rolled steel sheets were 3 The temperature at point +30°C was held for 120 seconds, followed by quenching (air cooling) at an average cooling...

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Abstract

The present invention relates to an ultrahigh-strength steel sheet, which comprises, in terms of wt.%, 0.10-0.60% C, 1.0-3.0% Si, 1.0-3.5% Mn, up to 0.15% P, up to 0.02% S, up to 1.5% Al, and 0.003-2.0% Cr, with the remainder being iron and unavoidable impurities, and in which the crystal grains of residual austenite have an average aspect ratio (major axis / minor axis) of 5 or higher, an average minor-axis length of 1 [mu]m or shorter, and a minimum grain-to-grain distance of 1 [mu]m or shorter. It has excellent unsusceptibility to hydrogen embrittlement.

Description

technical field [0001] The present invention relates to an ultra-high-strength steel sheet used as a steel sheet for automobiles and a steel sheet for transportation machinery, and particularly, to an ultra-high-strength steel sheet in which fractures caused by hydrogen embrittlement such as seasonal cracking and delayed fracture are suppressed from occurring , the fracture caused by hydrogen embrittlement is particularly a problem in steel sheets with a tensile strength of 980 MPa or more. Background technique [0002] Hitherto, high-strength steel sheets have been widely used in applications such as bolts, PC steel wires, and line pipes, and it is known that, when the tensile strength becomes 980 MPa or more, hydrogen embrittlement ( such as pickling embrittlement, plating embrittlement and delayed fracture). On the other hand, since the thickness of the steel sheet is thin, when hydrogen penetrates, hydrogen is released in a short time. In addition, from the viewpoints ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C22C38/38C22C38/58C21D9/46
CPCC21D1/20C22C38/14C22C38/34C22C38/005C21D9/48C22C38/12C21D2211/005C22C38/22C21D2211/001C22C38/44C21D2211/002C22C38/50C22C38/46C22C38/42C21D2211/008C22C38/26C22C38/06C22C38/08C22C38/16C22C38/32C22C38/38C22C38/24C22C38/002
Inventor 衣笠润一郎汤濑文雄向井阳一上妻伸二赤水宏粕谷康二池田宗朗杉本公一
Owner KOBE STEEL LTD
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