Lath martensite
Lath martensite forms in low-carbon steels during quenching as parallel strips and is harder than high-carbon martensite.
Physical-Chemical Mechanism of Action
Cooling low-carbon steels produces lath martensite, a form of martensite made of parallel strips. These structures form through rapid cooling and are typical in steels with a carbon content below 0.2 %.
Metallurgical Relevance & Welding Risks
Lath martensite is harder than high-carbon martensite and offers better toughness. However, it can also increase stress buildup, which may cause cracks under repeated loading. Additionally, rapid cooling can lead to distortion or stress buildup, especially if the steel is under stress.
Workshop Practice & Action Guidelines
To avoid lath martensite while ensuring good toughness, control the cooling process. When welding low-carbon steels, monitor the cooling time after quenching. A cooling time of at least 10 seconds can help achieve a balanced grain structure and good toughness. Avoid rapid cooling under stress, as this can cause stress buildup.