Martensite tempering stage
Martensite temper stage is the area in the weld where the supersaturated solid solution transforms to glass-hard martensite during rapid cooling. This can lead to crack-sensitive weld zones.
Physico-Chemical Mechanism of Action
The martensitic transformation stage occurs when a supersaturated solid solution (e.g., austenite) cools rapidly in a cool environment. The rapid cooling prevents complete transformation of the material to ferrite and causes incomplete transformation to martensite. This process is characterized by the appearance of a glassy, crack-sensitive structure.
Metallurgical Relevance & Welding Risks
Martensitic transformation stages are particularly dangerous because they lead to hard, crack-sensitive weld zones. These zones can cause hot cracks and distortion, especially under mechanical stress. The risk increases when cooling steps are too fast or irregular.
Workshop Practice & Action Guidelines
To avoid martensitic transformation stages, it is important to carefully control the critical temperature range during cooling. This can be achieved by using cooling water or special cooling media. Cooling steps should be slow and uniform to ensure complete transformation of the solid solution to ferrite. Recommended cooling times vary by steel type, but generally they should be between 10 and 30 seconds.