Research On Rotating Arc Narrow Gap Welding Technology Of Multi-position In Space

A large number of applications of thick-walled pipe and large steel structure requirehigher demand for welding in engineering. Normally in field operations, the large pipeshould be fixed, which is need to be welded by a moving welding torch in all-position.This dissertation is aimed to study how to apply the rotating arc narrow-gap weldingtechnology to the four typical spatial location in the pipe automatic welding.This dissertation had studied the influence that the wire feed speed, torch angle, theCO₂content of the protective gas, the rotation frequency, welding speed, the width ofthe groove when using vertical（3o’clock） welding had on the shape of the bead, theresults show that the change of process parameters does not change the lack of fusiondefect on the right angles region of both sides of I-shaped groove, but the U-shapedgroove can eliminate the lack of fusion defects, which obtains the30mm thickmulti-layer bead that has good forming surface and has not internal defects. Thedissertation had studied arc shape and the welding pool in different conditions ofparameter through high-speed camera system and had analyzed the reasons of the lackof fusion defects in I-shaped groove.The dissertation had studied what effect the wire feed speed, torch angle, the CO₂content of the protective gas, the rotation frequency, welding speed on the welding beadwhen using45°welding of4:30direction position and45°welding of1:30directionsposition, and compare difference of both welding methods in aspect of the welding poolforced and welding craft. The results show that the adaptability of45°welding of1:30direction position’s parameters is better and45°welding of4:30direction position ismore sensitive to changes in the parameters. This dissertation had analyzed the reasonof45°welding of4:30direction position is sensitive to parameter changes and putforward to the solutions, which acquires long good forming straight multi-layer weldingbead.This dissertation had studied the influence that wire feed speed, torch angle, theCO₂content of the protective gas, the rotation frequency, welding speed, wire extensionwhen using the overhead position welding （6o’clock） had on the bead shape. the arcshape and the welding pool and the transition of the droplet was studied by high-speedcamera system in different parameters. The results show that the range of weldingparameter which makes the bead surface less embossing is narrow, arc force underdifferent parameters has two different roles: First, the force of the arc has on the weldpool is small, which can’t impact too much on the forming shape of pool. This bead surface is often raised in a large degree, wire droplet is basically a transition of particle;second, the arc force has a major role that support the welding pool. The bead surfaceraised in a small degree, wire droplet presents in the two forms of particle transition andshort-circuit transition in a week of the arc rotation.The dissertation had studiedmulti-layer welding experiments which acquires long good forming straight multi-layerwelding bead.