Study On Flux Cored Wire TIG Welding Process Characteristics

TIG welding technology has the advantages of stable welding arc,high welding quality and so on.In order to make the TIG welding be applied to underwater local dry welding,this paper put forward a new method of flux cored wire TIG welding,aiming at reduce the influence of wet environment and fast cooling condition of underwater welding.In the traditional TIG welding process,the welding wire and wire feeding device occupy a large space and is hardly used in narrow spaces such as the chambers for local dry underwater welding.A simple compact welding wire feeding device is designed to realize the flux cored wire TIG welding process.This study uses high-speed photography and spectral analysis methods in order to clarify the characteristic of droplet transfer behavior,optimizes welding parameters and welds DH36 steel material.The welding procedure qualification has been also done.This thesis reports a comprehensive research about the processing property of flux cored wire TIG welding.The droplet transfer forms and welding arc temperature field have been analyzed by using high-speed photography and spectral analysis methods.With the decrease of the wire-electrode gap,the droplet transfer form of flux cored wire TIG welding will gradually present bridging transfer,slag column guided transfer and non-contacting transfer.The important role of surface tension in the process of droplet transfer has been proposed by using the static force balance theory and the pinch instability theory.The liquid bridge will become instability rupture in the non-contacting transfer process,while the liquid bridge is stable in the bridging transfer and slag column guided transfer process.This study optimizes the welding process parameters and uses the slag column guided transfer process to fill the weld groove.No defect such as porosity and crack has been found in the welded seam.And welding procedure qualification was conducted on the welded specimens subsequently according to AWS D3.6 2010.The results show that all welding specimens can meet the requirements of AWS D3.6:2010 in A level.By analyzing the microstructure and hardness of the welded joint,it was found that the heat treatment effect of the latter bead on the former bead can increase the acicular ferrite structure and reduce the pro-eutectoid ferrite structure in the former bead and improve the mechanical properties...