Phase Transformation Kinetics

Phase transformation kinetics simply means: how fast the structure rebuilds during cooling. In welding, this is crucial because the cooling rate determines whether you get hard, brittle or tough, soft material. If you cool too fast, the structure becomes hard and crack-prone. If you cool too slowly, it becomes soft and loses strength. You have to control the cooling so that the structure is right – you do this via heat input and preheating. Watch the cooling time between the critical temperatures. You have to keep that under control, then the result will be right. When in doubt, better ask than weld blindly.