Lath martensite
Lath martensite is a submicroscopic structure that forms when steels cool rapidly. It consists of parallel blocks with high dislocation density and leads to high stress buildup and toughness.
Physico-Chemical Mechanism of Action
With rapid cooling of steels, lath martensite forms via a diffusionless lattice transformation. The atoms shift in a specific pattern, leading to submicroscopic parallel blocks.
Metallurgical Relevance & Welding Risks
Lath martensite is very tough and has a high build-up of stress. This can lead to cracks and hot cracks, especially if cooling is too fast. The hardness of the steel increases, which reduces its formability.
Workshop Practice & Action Guidelines
To avoid lath martensite, the cooling rate should be controlled. When welding steels with high carbon content, slow and uniform cooling is required. Use a suitable cooling medium such as water or air to regulate the cooling speed.