| Compared with other welding methods,ultra-narrow gap welding with flux band constraint arc has its unique welding advantages: high welding efficiency,excellent welding joint performance,small welding deformation and small welding heat input,which is suitable for welding heat sensitive materials.This method has done a lot of technological experiments in horizontal welding,and made a breakthrough in rail welding.The cast steel nozzle needs to be welded in transverse position,and the transverse welding of this welding method has only been studied preliminarily.In this paper,a method of ultra-narrow gap transverse welding with flux band constraint arc is proposed.Firstly,a set of ultra-narrow gap transverse welding device is designed independently Secondly,in order to improve the production efficiency of welding,the continuous production of flux sheet and the automatic laying device of flux sheet are designed Thirdly,the problem of air hole and sidewall root fusion in ultra-narrow gap welding is studied,and it is found that the composition of flux sheet has certain influence on air hole and sidewall fusion Finally,the ultra-narrow gap transverse welding device is applied to the cast steel nozzle for process test,and the influence of welding specification on the fundamental fusion of groove sidewall is studied.The experimental results are summarized as follows:(1)A set of ultra-narrow gap transverse automatic welding device with flux band constraint arc is designed,which is composed of welding gun mechanism,welding traveling trolley mechanism and rotating mechanism,and realizes the welding of ultra-narrow gap transverse girth weld.(2)The structure of flux strip used in ultra-narrow gap transverse welding is designed,and the automatic laying device of flux strip is designed on this basis,which realizes continuous and automatic feeding of flux strip.(3)The welding test was carried out in square steel by using the designed welding device with ultra-narrow arc gap.The influence of the composition of flux sheet on the fusion of pores and side walls was studied.It was found that the fusion of pores and side walls was improved by adding burn-resistant substances in flux sheet,especially the fusion depth of side walls showed an increasing trend with the increase of the percentage of burn-resistant substances.(4)The welding device with ultra-narrow gap confined by flux band was tested in cast steel nozzle,with welding voltage of 22 V,welding current of 174A?245A and welding speed of 8.25 ? 9 mm/s;The influence of welding code on the fusion of weld side wall root is studied.In a certain range of welding code,increasing welding voltage and welding current and decreasing welding speed will increase the fusion depth of weld side wall root.(5)The micro-structure and micro-hardness of cast steel nozzle joint are analyzed,and the welding heat affected zone is only about 2mm;The micro-structure of base metal is martensite+ferrite in normalized state,the micro-structure of weld is acicular and flaky martensite,and the heat affected zone is the mixed structure of tempered martensite,bainite and retained austenite.By testing the micro-hardness of the joint,the hardness of the weld zone is the highest,the heat affected zone is the second,and the base metal is the smallest.No softening phenomenon is found in the ultra-narrow gap transverse welded joint. |
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