| 摘要 |
PURPOSE:To prevent a local corrosion at welding heat affected part by quenching and tempering a welding base metal to obtain a homogeneous intermediate step structure, and to obtain temper treated said structure also in the welding heat affected part. CONSTITUTION:At welding time of a quenched and temper treated steel plate having the basic components of, by weight 0.05-0.13% C, 0.0005-0.003% B, 0.01-0.1% Sol, Al, 0.0005-0.01% Ca and 0.3-0.70% quenchability parameter P at welding time indicated by a formula (1), all of the structure of the welding heat affected part is made to the intermediate structure in processes from hand welding of low heat input due to rapid cooling rate to submerged arc welding of high heat input due to slow cooling rate. Simultaneously, only the surface layer part near the welding part where corrosion may be caused is temper treated locally at 500-700 deg.C in 5mm. depth or below, and the welding heat affected part is prevented from the corrosion by sea water, etc. in contact therewith. |
