Method of increasing strength of cold worked part by ultrasonic shock treatment, and metal product with high fracture toughness and fatigue strength

A technology for impact treatment and metal products, which is applied in the field of metal products with high strength of cold-worked parts and high fracture toughness and fatigue strength by ultrasonic impact treatment, which can solve the problem of low site selectivity, difficult to handle large objects, and difficult to handle only Steel surface and other issues

Active Publication Date: 2005-12-28
NIPPON STEEL CORP
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Problems solved by technology

However, the range of residual stress that can be improved by shot peening treatment is at best to a depth of about 300 μm, and the effect of shot peening treatment to inhibit crack progression has a limit.
[0016] Therefore, shot peening treatment is not necessarily a perfect method in terms of the effect of suppressing the progress of cracks. In addition, it is difficult to handle large objects because of the need to incorporate large machines a

Method used

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  • Method of increasing strength of cold worked part by ultrasonic shock treatment, and metal product with high fracture toughness and fatigue strength
  • Method of increasing strength of cold worked part by ultrasonic shock treatment, and metal product with high fracture toughness and fatigue strength
  • Method of increasing strength of cold worked part by ultrasonic shock treatment, and metal product with high fracture toughness and fatigue strength

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Embodiment

[0059] Hereinafter, the present invention will be specifically described through examples.

[0060] Steel materials are bent to produce BR pipes, which are then subjected to ultrasonic shock treatment. Then, after the ultrasonic treatment, a part of the steel pipe was cut out, and a fatigue test piece and a microscopic test piece were produced.

[0061] Since it is difficult to directly measure the fracture toughness, the particle size is measured by a microscopic test, and the particle size is used as a parameter of toughness (for example, in Iron and Steel Research No. 327 "Improvement of Toughness of HSLA Steel HAZ by Finely Dispersed Ti Oxide" In Fig. 7, toughness (migration temperature) and particle size, with y=-1059(x 0.5 )+40 [y is the migration temperature, z is the relationship between the particle size]). The hardness was also measured by a microscopic test.

[0062] Table 1 shows the steel materials used, and Table 2 shows the specifications of the bending proce...

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Abstract

The invention provides a method for improving the strength of a cold-worked part by ultrasonic impact treatment. By implementing ultrasonic impact treatment on the surface of the stretched side of the metal cold-bending process, the surface hardness can be made higher than that of the surface without ultrasonic impact treatment. The surface hardness is increased by more than 10%, and the tensile residual stress can be reduced, and the fracture toughness and fatigue strength can be improved.

Description

technical field [0001] The invention relates to a method for improving the strength of a cold-worked part by ultrasonic impact treatment, and a metal product with high fracture toughness and fatigue strength manufactured by the method Background technique [0002] In recent years, in order to promote high performance, high functionality, and cost reduction, the strengthening of steel used for structural members has been progressing. However, for example, in ships, offshore structures, bridges, etc., which are subjected to repeated loads during service, generally, as the strength increases, the stress generated in the structural members increases, and the problem of significant metal fatigue often occurs. [0003] Therefore, due to the problem of metal fatigue, there may be restrictions on increasing the strength of steel. [0004] In general, in structures, fatigue cracks are a problem mainly in stress concentration parts or welded parts, but other than that, fatigue cracks...

Claims

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Application Information

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IPC IPC(8): B21D5/01C21D7/04
CPCC21D7/04B21D5/01
Inventor 富永知德松冈和巳本间宏二
Owner NIPPON STEEL CORP
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