Cracks were found at the curvature transient zone of high pressure cylinder during the maintenance of the No.3unit in Qinshan No.2Nuclear Power Station

which may cause safety accident during operation.The welding repair technology for ZG15Cr2Mo1cylinder was developed through the welding experiment

microstructure analysis and mechanical test.The difficulties in welding repair were presented and the detail operation steps were given.The results showed that

tensile strength of the weld joint by nickel based weld material was 505MPa;cracks were not observed after bending test;the impact absorbing energy was 105J.The mechanical properties indicated that the austenitic weld satisfied the operational requirement of the cylinder.The developed welding repair technology was adopted during in-field repair of the high pressure cylinder.After one year in-site operation

the repaired zone exhibited a good effect.