与典型冷金属过渡(Cold Metal Transfer,CMT)电参数波形相比,改进后CMT电参数波形的短路过渡阶段新增了一个脉冲阶段,从而保证了稳定的镁合金熔敷沉积过程.通过分析镁合金的性能及CMT短路过渡阶段的熔滴受力情况,探究了在典型CMT电参数波形下镁合金熔敷时产生飞溅的原因,同时研究了改进后CMT电参数波形下短路基值阶段电流值Isc2对熔滴过渡稳定性的影响.结果表明,短路峰值阶段可以促使熔滴在短路过渡时形成颈缩,从而有助于实现稳定无飞溅的熔滴过渡过程.当Isc2较小时,会导致形成的颈缩较粗,液桥难以自然断裂;而当Isc2较大时,颈缩处会具有较大的电流密度,从而导致液桥容易在大热量的作用下气化爆断.使用改进后CMT电参数波形进行镁合金熔敷时,在12 m/min的送丝速度下,仍可以保证熔敷过程稳定可控.
Stability analysis of the cold metal transfer deposition process of AZ91 magnesium alloy
Compared with the typical cold metal transfer(CMT)process,there were obvious changes in the short circuit(S/C)phase during the improved CMT process,which had been proved to be more suitable for stable deposition process of magnesium alloy.In this paper,the causes of spatter during the typical CMT deposition process of magnesium alloy and the effect of S/C current Isc2 during the improved CMT deposition process on the stability of droplet transfer were investigated based on the analysis of the magnesium alloy properties and the force on the droplet during S/C phase.The results showed that the addition of S/C pulse phase could promote the formation of the liquid bridge during the S/C phase,thus realizing the stable droplet transfer without spatter.The liquid bridge was thick when the S/C current was small,and thus it was difficult to achieve the natural broken of the liquid bridge.While excessive current density was formed at the liquid bridge when the S/C current was large,leading to the gasification burst on the liquid bridge.A relatively stable and controllable S/C transfer process could be realized even at the wire feeding speed of 12 m/min when the improved CMT process was applied.
magnesium alloyimproved CMT techniquedeposition processstability analysisdroplet transfer
万方数据
维普
