Abstract
By adding carbon to chromium-molybdenum steel containing 1.14%Cr,0.21%Mo, 0.17%C, eight specimens with different carbon contents were prepared. The normal transformation points of these specimens were determined by measuring the therma expansion with differentia dilatometer.
The A3 points of these steels gradually decrease as the carbon content increase, though A1 point is nearly constant.
The effect of carbon on the transformation points due to the maximum heating temperature and the cooling rate was studied by magnetic analysis. As the maximum heating temperature or the cooling rate increases the transformation points are markedly lowered, resulting in self-hardening. The self-hardening ability increases as the cabon content increases up to 0.75%.
The hardeness of the chromium-molybdenum steel increases as the cabon content increases up to 0.75%. The hardness of oil-quenehed or air cooled specimens from different high temperatures was studied. The change of hardness due to the tempering of oil-quenched specimens were also measured. It was found that considering hardness only, the most suitable oil quenching temperature may be 850°C.
The microstructures of these specimens cooled under different conditions were examined and the relations between the structure and the experimental results were studied.
