Wear characteristics of vitrified bonded CBN wheels in grinding mild steel

This paper investigates the wear mechanism of a vitrified bonded CBN wheel in grinding mild steel (SS400). Wheel wear after grinding mild steel is extremely large compared to cast iron (FC200), hardened steel (S45C) or high-speed steel (SKH57), even though the grinding force is small. It became clear that the wheel wear increases under the condition of longer arc contact. Furthermore, a single grain cutting test reveals that the actual chip length of SS400 almost doubles compared to the SKH57 or FC200 chip, and that the chips are very brittle. Therefore it seems that the chips do not erode the bond material directly. Through SEM observations of the wheel and workpiece surfaces before and after grinding, it was found that SS400 chips are easily loaded into the chip pockets on the wheel surface, and there are many deposited chips and embedded CBN grits on the ground surface. These phenomena, therefore, indicate the possibility of the consecutive fracture of CBN grits, and lead to the severe wear of CBN wheel.