Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1981-02-05
1984-10-09
Skiff, Peter K.
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
C21D 1100
Patent
active
044759630
ABSTRACT:
A method for postweld heat treatment (hereinafter referred to as PWHT) for multilayer welding, in which the terminating point of the PWHT is correctly judged to preclude cracking due to insufficient treatment or uneconomical excessive treatment, the method including the steps of determining the residual hydrogen concentration directly beneath the final welded layer immediately after completion of welding determining a crack-preventing critical hydrogen concentration to obtain a ratio of the critical hydrogen concentration to the residual hydrogen concentration determining the value of a product of a hydrogen diffusivity coefficient during the heat treatment and a holding time where a hydrogen concentration currently occurring in the heat treatment reaches the critical hydrogen concentration, on the basis of the relation of a ratio of the current hydrogen concentration to the residual hydrogen concentration and a sum of a parameter of hydrogen diffusion to be determined depending upon the welding conditions and the above-mentioned product measuring the temperature of the heat treatment at a suitable point of the weld, and terminating the heat treatment at a point in time when a time-integrated value of a hydrogen diffusivity coefficient at the measured temperature exceeds the value of the above-mentioned product.
REFERENCES:
Welding Journal, vol. 58, No. 52, Feb. 1979, Miami, US, W. S. Kyte: "Postweld Heat Treatment for Hydrogen Removal", pp. 54s-58s, Whole document.
Metals Technology, vol. 2, Feb. 1975, London, GB, B. Chew: "Diffusion of Hydrogen in Fillet Welds", pp. 66-72, p. 70.
Stahl und Eisen, vol. 98, No. 22, Nov. 2, 1978, Dusseldorf, DE V. Pilous: "Temperaturfuhrung beim Schweissen eines warmfesten Cr--Mo--Ni--V--Stahles mit 0,18%C und 0,92% Cr in grossen Wanddicken", pp. 1167-1170.
Metals Technology; Feb. 1975; "Diffusion of Hydrogen in Fillet Welds", B. Chew, W. S. Kyte; pp. 66-72.
Welding Journal; Feb. 1979; "Postweld Heat Treatment for Hydrogen Removal", W. S. Kyte, B. Chew; pp. 54-58.
Stahl und Eisen, vol. 100, No. 1, Jan. 1, 1980, Dusseldorf, DE V. Pilous: "Beitrag zum Schweissen eines warmfesten Cr--Mo--Ni--V--Stahles mit 0,18%C und 1% Cr fur Schmiedestucke im Kraftwerksbau", pp. 9-12.
Ohmae et al., Study on the Rationalization of Intermediate Postweld Heat Treatment, Mar. 1975, Mitsubishi Jukogyo Technical Bulletin, vol. 12, No. 2, pp. 46-51.
Eiji Takahashi et al., Prevention of the Transverse Cracks in Heavy Section Butt Weldments of 2.sub.4.sup.1 Cr--1Mo Steel Through Low Temperature Postweld Treatment (Reports 1-3), Apr. 1979, Oct. 1979, Transaction Japan Welding Society, vol. 10, 1979.
Iwai Kenji
Takahashi Eiji
Kabushiki Kaisha Kobe Seiko Sho
Skiff Peter K.
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