Research on Laser Welding for Seal Weld of AP/CAP Unit Control Rod Drive Mechanism

For the requirement of serval replacement of AP/CAP unit control rod drive mechanism, laser technology was introduced into the seal weld welding of the control rod drive mechanism to reduce the welding deformation and residual stress, and seven cut-welding cycles were carried out on the mockups. The results show that the laser welding method is practicable, the structure design of the filled ring is reasonable, the weld bead forming is good, the reinforcement is uniform and no incomplete penetration, no fusion, no undercut occur. The penetration test of the weld shows no defects. For each cut-welding cycle, the outer diameter of the down lip remains constant state, especially in the first four cycles, the diameter is only 0.02mm different from the design value. The residual stress is tensile stress and decreases with the increase of cycle time.