Mo鋼の恒温変態組織と機械的性質の関係

抄録

In molybdenum steels a structure called divorced pearlite, consisting of blocky carbide and ferrite, is induced with higher Mo/C ratios and elevated transformation temperatures, while a lamellar pearlite structure develops with lower Mo/C ratios and/or lower transformation temperatures.
Experiments have been carried out to clarify the effect of pearlite morphology on the mechanical properties using steels with different Mo/C ratios (0.02, 0.47 and 1.17) transformed at various temperatures ranging from 675°C to 500°C.
It has been shown that in steels having the lamellar pearlite structures, the Charpy transition temperature is lowered and the shelf energy is increased with decrease in interlamellar spacing. The finer interlamellar spacing gives rise to the increased tensile and yield strength.
Divorced pearlite structures, however, are found to deteriorate the impact and tensile properties.
M₂₃C₆ carbide, besides M₃C, is observed to form at higher transformation temperatures in steel with the highest Mo/C ratio, but carbide pcr se has no significant effect on the mechanical properties.