Highly strong, thick electric resistance-welded steel pipe excellent in quenching property, hot forming processability and fatigue strength, and method for manufacture thereof

A hot workability, fatigue strength technology, applied in the interconnection system, transportation and packaging, suspension, etc., can solve the problems of easy cracks, stabilizer fatigue strength reduction, lack of hot workability, etc., to achieve high durability, Excellent fatigue strength and excellent hardenability

Inactive Publication Date: 2008-08-20
NIPPON STEEL CORP
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

B-containing steel lacks hot workability, and cracks and defects are prone to occur during hot forming, which has become a big

Method used

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  • Highly strong, thick electric resistance-welded steel pipe excellent in quenching property, hot forming processability and fatigue strength, and method for manufacture thereof
  • Highly strong, thick electric resistance-welded steel pipe excellent in quenching property, hot forming processability and fatigue strength, and method for manufacture thereof
  • Highly strong, thick electric resistance-welded steel pipe excellent in quenching property, hot forming processability and fatigue strength, and method for manufacture thereof

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Experimental program
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Effect test

Embodiment

[0084] Various steels having the compositions shown in Table 2 were melted and cast into slabs. This cast slab was heated to 1150°C, and hot rolled at a rolling temperature of 890°C and a coiling temperature of 630°C to produce a steel plate with a thickness of 6 mm. This hot-rolled steel sheet was slit into a predetermined width, and high-frequency electric welding was used to produce an electric-welded steel pipe (main pipe) with an outer diameter of 90 mm. Next, the steel pipe was heated to 980° C. by high-frequency induction heating, and then reduced in diameter and rolled to produce a thick-walled electric-welded steel pipe with a wall thickness of 7 mm and an outer diameter of 35 mm.

[0085] In addition, for electric welded steel pipes manufactured using No. 1 steel in Table 2, thick wall electric welded steel pipes with a wall thickness of 5 to 7.5 mm and an outer diameter of 30 to 35 mm were produced by changing the area reduction rate during reducing rolling.

[008...

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Abstract

The present invention provides high strength thick-gauge electric-resistance welded steel pipe excellent in hardenability, hot workability, and fatigue strength and a method of production of the same, that is, thick-gauge electric-resistance welded steel pipe containing, by mass%, C: 0.25 to 0.4%, Si: 0.01 to 0.50%, Mn: 0.8 to 1.5%, P: 0.05% or less, S: 0.05% or less, Al: 0.05% or less, Ti: 0.005 to 0.05%, B: 0.0005 to 0.01%, N: 0.001 to 0.05%, and a balance of Fe and unavoidable impurities, having a critical cooling rate Vc expressed by equation <1> of less than 30 DEG C/s, and having a ratio of thickness t and outside diameter D, t/D, of over 0.15 to 0.30 in range: logVc = 2.94 - 0.75 where, P=2.7C+0.4Si+Mn.

Description

technical field [0001] The present invention relates to a high-strength thick-walled electric-welded steel pipe suitable for use in a hollow stabilizer for ensuring driving stability of an automobile and excellent in hardenability, hot workability, and fatigue strength, and a manufacturing method thereof. Background technique [0002] As one of measures to improve the fuel efficiency of automobiles, weight reduction of automobile bodies is being promoted. Stabilizers are also listed as objects of weight reduction, which ease the roll of the car body when turning and ensure the stability of the car body when driving at high speed. In the past, stabilizers were manufactured by processing solid materials such as bar steel into desired shapes, but in order to reduce weight, hollow steel pipes such as seamless steel pipes and electric resistance-welded steel pipes (electric resistance-welded steel pipes) were used. Material manufacturing is on the rise. [0003] An electric wel...

Claims

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Application Information

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IPC IPC(8): C22C38/00C22C38/14C22C38/54C21D8/10B60G21/055
Inventor 石冢哲夫三村裕幸小弓场基文高杉直树市山贵博
Owner NIPPON STEEL CORP
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