Determination of Ms temperature: methods, meaning and influence of ‘slow start’ phenomenon

Knowledge of the martensite start temperature in low and medium alloy steels is of critical importance for steel makers, or any industry involved in the transformation of hardenable steels. Its determination is often carried out by length change measurements in quenching dilatometers. The present paper focuses on the meaning of the information obtained in these experiments and discusses two alternative methods and their respective benefits, particularly with respect to the phenomenon sometimes referred to as ‘slow start’ for the martensite transformation.