Research On Arc Characteristics And Welding Process Of Underwater Wet Flux-cored Arc Welding Of Duplex Stainless Steel

Underwater welding is a special welding method carried out in an underwaterenvironment.As an important process for the installation and maintenance of underwaterengineering,underwater welding is one of the key technologies of nuclear powerdevelopment and increasing the degree of resource development. With duplex stainless steelused in nuclear power plants and marine facilities, the need for underwater welding ofduplex stainless steel is more urgent. In a variety of underwater welding method, due to thelow cost,simple equipment,flexible operation and adaptability characteristics of underwaterwet welding, underwater wet welding techniques has Extensive application in nuclearpower plants and marine facilities installation and maintenance.Arc stability is a foundation to get a good welding quality. In duplex stainless steelunderwater welding, research for mechanism of influence on underwater welding arc canprovide a theoretical basis for improving the arm stability of underwater welding. Moreover,weld quality of duplex stainless steel underwater wet welding is the most critical issuethroughout the welding process. Improvement of the weld quality is of great significance topromoting underwater welding technology. In this paper, underwater wet flux-coredwelding test of duplex stainless steel is conducted in hyperbaric chamber, and collectwelding electrical signal to analysis and process To independent variables of arc voltage,welding current, depth and welding speed of four welding parameters, CCD design inresponse surface method are used as a prototype test design, a five-level four-factor testprogram is designed, and based on test data, response model of arc complexity, porosity,weld size and weld fusion impact ratio with the welding parameters areestablished.Influence of a single welding parameters and interactions between them on arccomplexity, porosity, weld size and weld fusion impact ratio is analyzed. Finally, analyzethe influence of the welding parameters on microstructure. The results show that:(1) With the increase of the welding current, arc complexity is improving. With theincrease of the arc voltage, depth and welding speed, first, the arc complexity is a reduced,then it is increasing. The descending of welding parameters affected the stability is: arcvoltage,depth, the welding speed, weld current. (2) With the increase of welding current, first, the porosity is an reduced, then it isincreasing. With the increase of depth, the porosity also increases. With the increasing ofwelding speed, the porosity increases after the first decrease, while the welding current onweld porosity is not significant. The descending of welding parameters affected weldporosity is: depth, arc voltage, the welding speed, weld current.(3) With the increase of arc voltage and welding current, weld width increases.With theincrease of water depth and welding speed, weld width reduces. The descending of weldingparameters affect weld width is: arc voltage, weld current, weld speed, water depth. Withthe increase of arc voltage, weld penetration increases.With the increase of welding current,water depth and welding speed, weld penetration reduces. The descending of weldingparameters affected weld penetration is: water depth, weld speed, weld current, arc voltage.With the increase of arc voltage and welding current, reinforcement height increases afterthe first decrease With the increase of welding current, water depth and welding speed,reinforcement height reduce The descending of welding parameters affect reinforcementheight is: arc voltage, weld speed,water depth, weld current(4) With the increase of voltage and current, fusion ratio increase. With the increaseof depth and weld speed, fusion ratio increase after the first decrease,the descending ofwelding parameters affected weld fusion ratiois:depth,weld speed, current, voltage.（5）With the increase of water depth, the HAZ is narrowing, the grains become smalland the grains in seam become small. With the increase of voltage, the HAZ is widening,the grains become coarse, and the grains in seam become coarse. With the increase ofcurrent, the HAZ is widening, the grains become coarse, and the grains in seam becomecoarse. With the increase of weld speed, the HAZ is narrowing, the grains become coarse,and the grains in seam become small. In the shallow water, the grains in seam become thickwith the increase of welding speed; in the deep water, the grains in seam become small withthe increase of welding speed, the reduce of cooling rate is more significantly, the grains inHAZ and seam becomes small with the increase of welding speed.