Plate martensite
Plate martensite is a brittle microstructure consisting of lenticular plates with twin structures. It forms in high-carbon steels through rapid cooling.
Physical-Chemical Mechanism of Action
Plate martensite forms by a diffusionless shear reaction in high-carbon steels. On rapid cooling, the iron crystallizes into a martensitic structure, leading to brittle plate formation. These plates often have fine twin structures.
Metallurgical Relevance & Welding Risks
Plate martensite makes the weld metal very brittle and prone to cracking, especially in hot welding processes. The brittle structure can lead to hot cracks if cooling is not controlled. It also reduces toughness and mechanical strength of the weld.
Shop Practice & Action Instructions
To avoid plate martensite, ensure controlled cooling for high-carbon steels. This can be achieved by using cooling water or special cooling media. The cooling time should be between 5 and 25 seconds to develop a sufficiently tough structure.