Study On TIG Welding With Flux-cored Wire For Underwater Welding

In local dry underwater welding,the problem that is sensitive to water and rust,leads to the defects such as inclusion and blowhole.TIG welding with flux-cored wire(FCTIG)for underwater welding is proposed.In this paper,a special wire feeding device is designed,making FCTIG suitable for local dry underwater welding.The influence of different welding materials and process parameters on diffusible hydrogen in weld bead are analyzed by using high-speed camera and gas chromatography.Butt welding of DH36 steel is carried out in high cooling rate and high humidity environment,and the welding procedure is evaluated according to AWS D3.6M: 2010 standard.The acidic and alkaline flux-cored wires are used respectively to study weld microstructure,forming,macrostructure and the diffusible hydrogen content welding materials in different process parameters.Under the condition of small current(<140A),the weld formation is poor.When the current is greater than 140 A,the weld is well formed;With the increase of the current,the weld width increases with the current,the penetration depth of is not obvious change;With the increase of current,the content of acicular ferrite gradually decreases and the content of pro-eutectoid ferrite increases.The butt welding of DH36 steel is carried out in the water tank simulating high humidity and high cooling rate of the underwater environment.The welding procedure is evaluated and the test results are analyzed.The results of the process evaluation show that the welded joints meet the requirements of Class A welds in AWS D3.6 2010,whether using GFL-71 Ni or YCJ507.The metallurgical effect of acidic flux-cored wire is better than that of alkaline flux-cored wire.The welding seam microstructure with acidic flux-cored wire mainly consists of acicular ferrite.The weld seam welded with alkaline flux-cored wire consists of pro-eutectoid ferrite and acicular ferrite.The tensile strength and the yield strength of the welded joint of two kinds of flux-cored wire is in the range of 550~590MPa,430~440MPa,respectively.The difference between the two is small.The hydrogen content of welded joint welded by alkaline flux-cored wire is 50% lower than that of acid wire.The mean value of the impact toughness of weld and HAZ with alkaline flux-cored wire is 3.4 times,2.1 times as high as that of the welded joint of the acid wire,respectively.