Abstract
A simple method is proposed to predict mechanical properties of heattreated large steel forgings. The method is based on the findings. Firstly, the main considerations for the strength and the ductility are the carbon content of the forging and the microstructures induced during quenching. Secondarily, the microstructures can be computed from available CCT diagrams and cooling rates of quenching in the temperature range of 600°C to 300°C. These findings are verified experimentally on carbon steels and lowalloyed steels containing such elements as Ni, Cr and/or Mo. Equations for the rapid estimates of the cooling rates of steel forgings of the maximum diameter of 1000mm are derived experimentally as follows:
log D+0.513 log C=2.37 when quenched in water
log D+0.699 log C=2.02 oil
log D+0.954 log C=1.18 air
where, D is the diameter of a steel forging in mm. and C the looling rate in the temperature range of 600°C to 300°C in °C/sec.
Discussions are given on the validities of the findings and the equations.
