Peritectic Reaction
Peritectic reaction: An isothermal transformation where liquid and solid phases react to form a new solid phase. Important for phase equilibrium in carbon steels.
Physical-Chemical Mechanism of Action
In a peritectic reaction, a liquid metal phase reacts with an already existing solid phase under isothermal conditions. This leads to the formation of a new, different solid phase. The process is continuous and uniform across the entire weld.
Metallurgical Relevance & Risks in Welding
The peritectic reaction affects the microstructure and mechanical properties of the weld. Non-uniform or too fast peritectic transformation can lead to imbalances in the phase equilibrium, which can cause cracks or loss of toughness. This is especially important in carbon steels, as it affects the formation of martensite and austenite.
Workshop Practice & Instructions
To ensure a successful peritectic reaction, the weld must be held at the correct temperature. This is particularly relevant for cooling after welding. For carbon steels, the critical temperature window (t8/5) should be between 5 and 25 seconds to achieve a balanced phase. Monitor the cooling rate carefully and pay attention to correct welding parameter settings.