Method for postweld heat treatment
US4475963A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 5, 1981 |
| Grant date | Oct 9, 1984 |
| Priority date | — |
| Expiry date | Feb 5, 2001 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC21D9/50
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
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…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.