Effect of Ultrasonic Melt Treatment on Microstructure and Mechanical Properties of 35CrMo Steel Casting

Abstract

Effects of different power ultrasonic on microstructure and mechanical properties of 35CrMo steel casting were investigated using optical microscopy (OM), scanning electron microscopy (SEM) and hardness testing. A self-developed experiment apparatus was used for the propagation of ultrasonic vibration into the 35CrMo steel melt to carry out ultrasonic treatment. The experimental results showed that compared to the traditional casting, ultrasonic treatment can obviously change the solidification microstructure of 35CrMo steel, which is changed from coarse dendrites to fined dendrites or equiaxed grains. With the increase of ultrasonic power, equiaxed crystal is remarkably refined and its area is broadened. The micro porosity percentage of ingot casting decreases significantly and the porosity defects can be suppressed under ultrasonic treatment. The mechanical properties of 35CrMo steel ingot after heat treatment were enhanced by ultrasonic treatment: the maximum tensile strength is improved by 8.4% and the maximum elongation increased by 1.5 times.