Torch Optimization And Orbital Welding Procedure Of Narrow Gap Tandem Gmaw

As a high efficient welding technology, narrow gap welding has been widelyimployed in the manufacture of thick plates or pipelines. On the basis ofimproving the efficiency of metal deposition and solving the problem of poorsidewall fusion in narrow gap welding. Narrow gap tandem GMAW-P is able torealize orbital welding. in this paper orbital welding technology has beenanalyzed. Moreover, the model of relationship of weld forming and weldingparameter and mechanism of weld forming has also been successfully analyzed inorder to control it.Firstly, this paper improved the original narrow gap tandem GMAW weldingtorch by simplifying its interior structure, perfecting its air tightness andinsulativity and improving the result of gas shield, the new outer nozzle forshared molten pool and the dual-channel nozzle for unshared molten pool wasdesigned so as to meet the requirements of experiments. The optimization of airsifter structure was made by simulating the volume fraction of argon aroundnozzle sections and monitoring line in root of grooves which indicates the resultof gas shield, and the fact was realized that air sifter is essential to the weldingtorch. The applicability of the welding torch was researched by simulating theresult of gas shield under different distances between the torch and workpiecesurface, different groove types and different welding positions, and it was foundthat the result of gas shield is all fine under frequently-used circumstances.Gas-staining method and welding experiments were used to confirm the result ofgas shield, and it turned out that the result of gas shield is as good as expected.Then, this paper reached the parameter range in orbital welding andconfirmed the relationship between pulse peak voltage and wire feed rate byprocess experiments, which provided the basis for the design of experimentalparameters. The model of quadratic regression equation between depth ofsidewall fusion, depth of base metal fusion, thickness of deposition, contact angleof sidewall and welding parameters was built by conducting process experimentsbased on response surface method (RSM), and the fitting degree was tested good.Analysis of the influence welding parameters cause on depth of sidewall depth of base metal fusion, thickness of deposition and contact angle of sidewall wasmade, and it turned out that the influence welding position cause on weld formingis significant, while the influence welding position cause on depth of sidewallfusion, depth of base metal fusion, thickness of deposition and contact angle ofsidewall is broadly similar. Depth of sidewall fusion, depth of base metal fusion,thickness of deposition and contact angle of sidewall all presented a concavetrend with welding angle changing from0°to180°, and a bulge was observed onthe weld of over-head position which is detrimental to the quality of welding.welding parameters which led to a good quality of weld forming were optimizedand experimentally confirmed, which proved that the built model matches thepractical situations well.At last, this paper researched the characteristics of molten pool in differentwelding positions, pointed out the negative effect gravity cause on molten pool,and analyzed and reached the mechanical condition which is able to steady themolten pool. This paper also analyzed the mechanism of the welding formingcaused by different welding positions and summarized methods that throughchanging the angle of welding torch to control fluid flow in the molten pool andcontrolling the heat input to ensure small pool size and rapid solidificationvelocity of molten pool. By conducting multi-layer welding on positions whereflaws are incidental, this paper is able to reach welded splices with a good fusionquality and without macroscopic flaws.