Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Reexamination Certificate
2005-01-25
2005-01-25
Yee, Deborah (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
Reexamination Certificate
active
06846371
ABSTRACT:
A method of producing a high-strength high-toughness martensitic stainless steel seamless pipe which includes heating a martensitic stainless steel raw material to an austenitic range and subjecting the raw material to piercing and elongating to form an original pipe. The original pipe is cooled to form a structure substantially composed of martensite in the original pipe. The original pipe is reheated to a temperature in the dual-phase range between the Ac1transformation point and the Ac3transformation point, and is subjected to finishing rolling at an initial rolling temperature T (° C.) between the Ac1transformation point and the Ac3transformation point. The original pipe is then cooled to form a processed pipe. The processed pipe is tempered at a temperature below the Ac1transformation point. The reduction in area R in the finishing rolling step may be in the range of 10% to 90%, and the initial rolling temperature T and the reduction in area R may satisfy the relationship 800≦T−0.625R≦850.
REFERENCES:
patent: 6136109 (2000-10-01), Miyata et al.
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Kimura Mitsuo
Miyata Yukio
Toyooka Takaaki
JFE Steel Corporation
Yee Deborah
LandOfFree
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