The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 09, 1984
Filed:
Feb. 05, 1981
Eiji Takahashi, Akashi, JP;
Kenji Iwai, Kobe, JP;
Kabushiki Kaisha Kobe Seiko Sho, Kobe, JP;
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.