大电流MAG焊旋转喷射过渡中的熔滴失稳分析

Instant unstable phenomenon of rotational spray transfer in high-current MAG welding

旋转喷射过渡是大电流MAG焊的主要过渡形式。采用高速摄像法对大电流MAG焊旋转喷射过渡进行了研究,发现了一种瞬态不稳定现象:保护气体中含有CO2组分时,旋转喷射过渡中存在随机产生的熔滴非轴向排斥过渡,这种瞬态非轴向排斥过渡是稳定旋转喷射过渡中的不稳定干扰,是产生焊接飞溅的原因。通过理论计算,对产生该现象的机理进行了分析,指出旋转喷射过渡中发生非轴向排斥过渡的前提是焊丝端头液锥的消失,斑点力和金属蒸汽的反作用力是造成熔滴失稳上翘的主要原因,等离子流力是大电流MAG焊中产生的排斥过渡有别于一般CO2焊排斥过渡的主要原因。

Rotational spray transfer,which is a main model of metal transfer in high-current MAG welding,is researched by a high-speed camera system.An instant unstable transfer phenomenon is found: there is an occasional non-axial repelled transfer in rotational spray transfer.This is a kind of interference in steady rotational spray and will produce spatter.Mechanisms of the phenomenon are discussed through theoretical calculating.As a result,the disappearance of the liquid cylinder at the tip of wire is the prerequisite of this phenomenon.Spot force and reactive force of metal vapor are responsible for the droplet buckling and turning over.The plasma stream force will lead the difference of repelled transfer between high-current MAG welding and conventional CO_2 welding.