Casting of thrown away tool steel bits in the centrifugal casting route

Abstract

Cutting tools get worn out due to wear and are ground in order to use them again. This wear may be due to abrasive wear, diffusion wear, fatigue wear, adhesive wear. Wear of tool steels leads to shortening of the length, so small that the tool bits are no more usable. These waste and thrown away tool bits were collected which may include steel waste, pig iron, molybdenum iron, chromium iron, vanadium iron, tungsten iron and other waste material. This mixture was melted in induction furnace at temperature about 1600 o C to 1700 o C. After that the casting of the melt was done through the centrifugal route at speeds of 200 rpm and 250 rpm. The cast obtained is in the shape of tool steel cylinder. Then the samples were prepared for the hardness test, machinability test and SEM analysis. The hardness was measured across the radius of the cast cylinder by using Rockwell hardness test machine in C-scale. The machinability test specimens were taken from the outer zone of the cast cylinder and the test was carried out in Lathe by keeping the variables such as rotation speed (420 rpm), feed rate (0.15 KM), rack angle (10 0 ) material to be machined (mild steel) and time of machining (5 minutes 40 seconds) constant. The machinability of the centrifugally cast samples were compared with the as-cast samples. SEM micrographs were taken for the outer region of the cast cylinder and a comparative study was made with the as-cast samples. We found that there is an increase in hardness values with the distance from the centre to the outer periphery of the cast samples also the hardness values are higher for speed 250 rpm than 200 rpm. The Machinability of the centrifugally cast samples was better than generally used tool steels.