This study was undertaken to analysis the causes and morphology of Keyhole-Plasma Arc Welding
(K-PAW) solidification cracking of Maraging steel (C300) by means of optical microscopy (OM), scanning electron
microscopy (SEM) and Thermal-cale. The results indicated that although C300 has good weldability, it can also produce
solidification cracking. In our experimental condition, the dominant factor which induces solidification cracking
of high purity C300 was the strain-temperature growth rate. Improving the preheating temperature and increasing welding
heat input could reduce solidification cracking tendency. The preheating effect of heat source to the base metal
step-by-step was propitious to the arrest of solidification cracking. The solidification cracking tendency of weld metal
which has convex surface or fine equiaxed grains would be decreased.