Tertiary Cementite Precipitation
Tertiary cementite precipitation is the process where iron carbide precipitates from the ferritic lattice at very low temperatures. This can lead to a coarsened structure and reduced toughness.
Physicochemical Mechanism of Action
At very low temperatures (near room temperature), iron carbide can precipitate out of the ferritic lattice. This process is called tertiary cementite precipitation and leads to coarsening of the metal.
Metallurgical Relevance & Welding Risks
Tertiary cementite precipitation can reduce the toughness of the steel, since it creates a coarsened structure. This raises the susceptibility to cracks and slows the mechanical performance of the material. This precipitation is especially dangerous in cool environments or with slow cooling processes.
Workshop Practice & Instructions
To avoid tertiary cementite precipitation, take these measures:
• Use a sufficiently high cooling rate after welding to prevent iron carbide from precipitating.
• Make sure the weld cools in a protected environment and is not left in cool or damp areas.
• Monitor the cooling processes carefully and correct the cooling strategies if needed.