METHOD AND APPARATUS FOR IMPROVING RESIDUAL STRESS AT WELDED PART FOR PENETRATED PIPING IN VESSEL

摘要

PURPOSE:To improve residual stress in outer face in piping wall near the welded part by bringing cooling water into contact with the surface of the welded part fitting a penetrated pipe to a vessel and developing the stress exceeding the yield point with temp. difference given with heating and cooling from inner part of the penetrate pipe. CONSTITUTION:An induction heating coil 7 and a nozzle 8 for shower supported with a supporting pipe 6 are inserted into the inner position of the welded part 5 in the penetrated pipe 3 penetrating the hole 2 for penetrating the piping of lower end plate part 1 in the vessel. The vessel is made to the condition storing cooling water W therein. The piping wall is induction-heated from the inside by conducting electric current to the induction heating coil 7 and also the cooling water is fed into strand of the coil 7 from cooling water supplying system 10. The cooling water fed into the supporting pipe 6 is spouted into annular gap between the supporting pipe 6 and the penetrated pipe inner wall 3a from the spout holes 8b of the nozzle 8. The temp. difference exceeding the yield point is developed with the temp. difference between the induction heating position and the cooling position.