Cellular Solidification Structure
Cellular solidification structure forms at high temperature gradients and low alloy content as parallel, cell-like crystallites. It is softer and less crack-sensitive than martensite.
Physical-Chemical Mechanism of Action
The cellular solidification structure forms when high-temperature weld areas cool rapidly. Crystallites grow into a cell-like structure with parallel columns. This is driven by the high temperature difference between the weld pool and the surroundings.
Metallurgical Relevance & Welding Risks
The cellular solidification structure is softer than martensite and has lower hardness and toughness. This can increase susceptibility to cracking and deformation, especially under mechanical stress. It can also impair weld fusion and lead to poor mechanical properties.
Workshop Practice & Action Guidelines
To avoid a cellular solidification structure, it's important to control the weld's cooling rate. This can be done with cooling water or special cooling dies. Set the cooling rate so the microstructure stays martensitic, which gives higher hardness and toughness. Recommended cooling times vary by steel type, but generally should be between 10 and 20 seconds.