A dilatometric study of the continuous heating transformations in 18wt.% Ni maraging steel of grade 350

Dilatometric studies in 350 grade maraging steel (M350) were carried out to study the effect of heating rate and cold rolling, on precipitation, and martensite to austenite transformation. Recrystallized and cold rolled materials were subjected to controlled heating–holding–cooling cycles, under vacuum. The martensite to austenite transformation splits into two steps at lower heating rates. The first step enhanced by slow heating rate, occurs through a diffusion process, while the second step, enhanced by a fast heating rate, occurs though a shear process. The extent of the total martensite to austenite transformation is independent of heating rate, whereas the extent of precipitation decreases with increasing heating rate. Cold rolling of maraging steel results in a dilatational anomaly, which decreases with heating rate. At a given heating rate, cold rolling does not affect the extent of precipitation although it marginally lowers the precipitation start temperature and rate.