Optimum condition of thermal cycle for temper bead weld repair of SQV2A pressure vessel steel. Fundamental investigation in Gleeble simulation test

Temper bead welding technique is one of the most important repair welding methods for large structures for which post weld heat treatment (PWHT) is difficult to perform. In this study the optimum condition of weld thermal cycles to carry out temper bead weld repair for pressure vessel steel SQV2A are investigated taking interest in the improvement of the characteristics of coarse grained heat affected zone (CGHAZ) re-heated to the temperature between 670degC (Acl temperature) and 837degC (Ac3 temperature). Thermal/mechanical simulator Gleeble 1500 is employed to give specimens repeated thermal cycles. Improvability of the Charpy absorbed energy and the hardness for the thermal cycles is discussed. The temper bead thermal cycles were suggested that the peak temperature in the second thermal cycle should be selected as lower than Acl but near Acl. In this case triple thermal cycles temper bead process are enough to improve the characteristics of CGHAZ. When the other peak temperatures (that is, higher than Acl) in the succeeding thermal cycle are applied to CGHAZ, quadruple or more thermal cycle temper bead process should be applied. (author)