Microstructural Change and Hardness Profile of Roll Materials after Laser Irradiation and Tempering Process

抄録

Laser irradiation, using a continuous wave CO₂ crosscurrent laser with generated beam power of 1 kW, was performed on an adamite steel and an indefinite chilled cast iron roll materials which were used in the industries. Optical microscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) were applied to reveal the microstructural details. In addition, microvickers hardness test was conducted on the laser beam irradiated samples to measure hardness profiles of the laser treated area. The results indicate that, laser irradiated areas of two roll samples sequentially consist of melting zone, phase transformation zone and non-transformed heat affected zone on sections. The hardnesses at the melting zone on both samples are relatively low when the samples were irradiated by the laser, but increase dramatically after tempering at 540°C for 1 hr. On the other hand, the hardnesses at the phase transformation zones sharply decrease from high values when they were subjected to the tempering process for the irradiated samples. There are many small and well distributed FeS and MnS inclusions in the melting zone at the both roll samples. It also was observed that, there are occasional hot tears occurred in the indefinite chilled cast iron sample, but not in the adamite steel.