Flux Strips Production Process And Property Of Welded Joint Of Ultranarrow Gap Welding

Use of flux strips to constrict arc can well solve the easily occurred problems ofultranarrow gap welding,. The flux strips can effectively restrain arc, ptevent the arcgoing up along the sidewall, make the arc heat on the side wall and groove bottomcentralized, and get the full fusion. With a relatively narrow grove in the ultranarrowgap welding, the thickness requirements of flux strips is high. And the flux strips mustbe sufficiently dense. Aiming at the problem of flux strip density, the paper developednew flux strips, welded workpieces by ultranarrow gap welding with constrained arcby flux strips, and analysed organization and performance of the welded joints at last.First, the new production mold of flux strips is designed and developed toimprove the production method, based on the pre-test. The mold mainly have thefollowing characteristics:①The mold is small and portable, so that it’s convenient toremove and storage;②To press the wire mesh，the silicone band is used and gradientsare made on the mold base;③Using elastic deformation ability of foam rubber, theboth sides of black rubber used to control the flux amount can quickly return tooriginal position, which ensure the consistency of strips thickness and density.To weld with the flux strips which meet the requirements and the speciallydeveloped torch, it can obtain the stable welding process and good weld forming. Thetest uses H08Mn2Si wire of diameter of1.6mm,and weldments are14.5mm thick X60pipeline steel plate and6mm thick430stainless steel plate. Welded joints needmulti-layer and single-pass ultra-narrow gap welding experiments to complete. Beforewelding,various factors must be analysised to get the welding parameters of everypass welding. Both of two kinds steel have very low energy input, and are respectivelyabout0.6KJ/mm and0.45KJ/mm. And the widths of heat-affected zones are about1.0mm and0.65mm respectively.To analysis the welded joints microstrure and properties of two kinds of steel, it’sfound that HAZ of X60pipeline steel has microstructure of fine grains, and the grains’growth of coarse grain zone is not serious. Weld hardness is higher than that of thebase metal, and the softening zone is very narrow, which will reduce unfavorablefactors on the weld strength and toughness. And the hardness increases65%or so,compared with that of adopting SAW. The weld has higher tensile strength than basemetal, and excellent low-temperature impact toughness. The grains of430stainless steel coarse grain zone are relatively coarse, but because of its very low HAZ, theadverse effect of which on the joint will not be too much. And when steching, theselected samples fractured all in the base metal. This also can be proved that thestreghth of the joint was notreduced comparede with that of base metal, but had acertain degree of improve.