The computer simulation for vacuum casting and solidification process of 39 t ingot of steel 42CrMo4 (/% : 0. 38 ~0. 45C

0. 90 ~ 1.20Cr

0. 025Mo) has been carried out by using Any casting software to get that with cast liquid temperature 1 527 °C and superheat extent 40°C the casting time for 39 t ingot is 18.78 min including ingot body for 10 min and casting head for 8.78 min and the predicted shrinkage cavity location only occurs at center of casting head. The results of production practice in situ show that the forged die block is qualified by grade Ⅱ ultrasonic detection

and the yield of products increases to 71.35% from 65% before process improvement.