In order to fill the domestic technology gaps and improve the capability of self-maintenance of main equipment in nuclear power plants

the automatic welding technology for replacing in-service heater elements of voltage stabilizer is researched. According to the characteristics of replacing in-service electric heater and the shortcomings of existing technology

the closed welding head is developed

which improves the stability of welding arc and gas shielded effect. Through a large number of automatic welding technology tests

the influence of protective atmosphere

specimen size and the chemical composition of base metal on the appearance of weld are discussed

and the welding parameters are determined. The results show that the use of argon backside protection and helium front protection welding can ensure complete penetration and protective effect on backing pass;the deviation of specimen structure size can affect the appearance of weld due to different heat dissipation;and the higher the content of S in the base metal chemical composition

the easier it is to penetrate.