Research On GMAW Surfacing Technology Of Stainless Steel Stranded Wire

Manhole flange and the sealing surface of convex plate of the hydrogenation reactor usually served in high temperature,high pressure and corrosive environment for the long time.To guarantee the long-term service performance of the above-mentioned components,the inner wall of these components must be surfaced with the stainless steel corrosion resistant layer by the way of flat-position surfacing and horizontal-position surfacing.The current surfacing process uses stainless steel flux-cored wire for double-layer surfacing,but it has the disadvantage of slag inclusion in the surfacing layer.Stranded wire has natural advantages in surfacing applications because of its high deposition efficiency and low dilution rate.To solve the problem of slag inclusion in the surfacing layer of stainless steel flux-cored wire,this paper choose the stainless steel stranded wire to carry out experimental research.The research is composed of four parts which are droplet transition characteristics of stainless steel twisted wire,flat-position surfacing process study,horizontal-position surfacing process study and micro structure and properties analysis of surfacing layer.The details are as follows:The droplet transition parameter interval,welding parameter matching and droplet transition characteristics of stainless steel stranded wire were studied by high speed camera and welding arc analysis meter.With the increase of welding parameters,short circuit transition,mixing transition,droplet transition and jet transition appear in turn.The droplet transfer is of the best stability,and the droplet transfer frequency is about 100 times per second.When the arc voltage is lower than 25V,the droplet will transferred to the molten pool by short circuit.When the welding current is greater than 195 A and the arc voltage is greater than 27 V,the droplet transition mode will change from short circuit to droplet transition mode.The empirical formula U=0.09 I+7.4 for welding parameters matching of stainless steel stranded wire was obtained by linear fitting.By comparing the weld width and residual height of the flux-cored wire flat-positon welding beads and combining with the engineering metrics,the process parameters range of flat-position surfacing of stainless steel stranded wire was determined.The influences of welding speed,welding heat input and lap amount on the forming of stainless steel stranded wire welding beads were studied,obtaining the optimized flat-position surfacing parameters.The parameters are as follows that welding current I=195 A?23 5 A,welding voltage U=26 V?30 V,welding speed v=0.3 m·min-1?0.36 m·min-1,lap amount between weld passes a=0 mm?1mm.The micro structure of the flat-position surfacing layer is composed of austenite and a small amount of ?-ferrite.The ferrite number,inter-granular corrosion resistance,chemical composition,hardness and side bending properties of the surfacing layer all meet the corresponding standard requirements and the needs of engineering application.The influences of welding torch angle,welding speed and heat input on the forming of the horizontal-position surfacing layer of the stainless steel stranded wire were studied.And the forming mechanism of stainless steel twisted wire in the horizontal-position was analyzed.The optimized surfacing process parameters of stainless steel stranded wire in the horizontal-position were obtained through the process experiment with that the welding current I=195 A?215 A,welding voltage U=26 V?28 V,welding torch inclined downward-8°,welding speed v=0.36 m·min-1?0.42 m·min-1,lap amount a=0 mm?1 mm.The analysis of micro structure and properties of horizontal-position surfacing layer show that the ferrite content,chemical composition,inter-granular corrosion resistance,hardness and measured performance of the surfacing layer are all meeting the corresponding standard requirements and satisfying the needs of engineering application.