Weld Formation Control And Microstructure Refinement About P-MPAW Of Ultra-thin Stainless Steel

Stainless steel sheet has many characteristics such as smooth surface, corrosionresistance, non-magnetic and good high temperature strength and so on. Stainless steelsheet which thickness less than0.2mm is widely used in medical devices, microelectronics,precision instrument manufacturing, the nuclear industry, aerospace and other fields, andthe study on precision welding of ultra-thin stainless steel has become increasinglyimportant.At present, stainless steel sheet which thickness more than0.2mm is mostly selectedin the research on micro-plasma arc welding of stainless steel sheet, and the weldingcurrent usually is DC current. There is little research on micro-plasma arc welding of0.1mm thick stainless steel sheet. This is the background study on weld formation controland microstructure refinement about P-MPAW of ultra-thin stainless steel.Based on the ease deformation and burn characteristics of0.1mm thick ultra-thinstainless steel sheet and control theory of linear energy of pulsed micro-plasma arc welding,matching of welding parameters was established. One-side welding with back formationweld of0.1mm thick ultra-thin stainless steel sheet was achieved using pulsedmicro-plasma arc welding. Pulsed current signals in welding process are collected byLabVIEW-based software and hardware platform.Graphical program written in LabVIEW was used to the measurement and analysis ofunder rising/falling edge of pulse current signal. According to the characteristics of thesignal distortion, the method, measuring pulse current signal distortion by total distortion,was designed. Weighted sum for amplitude distortion, phase distortion andinter-modulation distortion is used to measure the pulse current signal distortion. Pulserising/falling edge become more obvious with the increase of frequency.Single factor experiments method is used to study the influence of pulse currentparameters on weld shape and weld Refinement. Analysis showed that；0.1mm thin plateweld width and weld Coefficient gradually increased with the increase of pulse-based ratio of base current and peak current, when the pulse duty cycle and pulse frequency is fixed,while the thickness of the weld decreases. Welding joint molding efficiency decreases withthe increase of pulse frequency but keep constant when pulse frequency fixed.By metallographic analysis on structure of knowledge, Phase composition of weld isaustenitic phase composition, usually is equiaxed grain and columnar grain, which grainsize is very small. Pulse-based ratio and pulse frequency have significant impact onmicrostructure refinement, but pulse duty cycle’s influence is not obvious. When the dutycycle and pulse-based ratio fixed, the grain size decreases and becomes more and moreuniform with the pulse current frequency increases. When the frequency and duty cycle isfixed, the grain size increases as the Pulse-based ratio increasing.Weld formation is affected by pulse current signal distortion and pulse rising/fallingedge. When the pulse current signal distortion increases the weld width is graduallydecreased, the weld thickness remained unchanged and welding joint molding efficiencydecreased. When the pulse current signal rising percentage increases, the weld width isgradually decreased while the weld thickness remained constant and welding joint moldingefficiency decreased.