Stability of keyhole in plasma arc welding

Stability of the keyhole plays a fundamental role in producing quality weld s in keyhole plasma are welding. Some studies have assumed that keyhole dia meter is a stability measurement. However, recent experimental observation by the authors revealed that width is not correlated with stability. To mea sure stability, this study uses the keyhole width as the lower limit of the weld pool width required to prevent keyhole collapse. Because the maximal width of the weld pool before burn-through is approximately fixed for parti cular applications, it can be used as the upper limit of the weld pool widt h for preventing burn-through. Hence, the margins of the keyhole process fr om collapse and burn-through can be measured based on how close the pool wi dth is to its upper and lower limits. The stability distance and stability factor are then defined based on the margins to quantify the state of the s tability of the keyhole process.