Solidification crack
A solidification crack forms when the weld metal solidifies too quickly during cooling, and the dendrites (crystal structure) come under stress. This leads to cracking in the direction of the weld.
Physical-Chemical Mechanism
During welding, the weld metal initially forms as liquid metal. If cooled too quickly, the dendrites cannot adjust in time and become stressed, leading to cracking.
Metallurgical Relevance & Welding Risks
A solidification crack can cause significant material loss and low toughness. It can also significantly impair the mechanical properties of the weld, which can be dangerous in high-stress applications.
Workshop Practice & Instructions
To avoid solidification cracks, the weld metal should be cooled slowly and controlled. This can be achieved by using cooling water or gas. An optimal cooling time of 30 to 60 seconds is often recommended to ensure uniform cooling.