Influence of Carbide Volume and Size on Machinability of Cold Working Die Steels

The influence of carbide volume and size on endmilling machinability of cold working die steels have been investigated. The volume of large primary carbide (M7C3) and small spheroidal carbide (M23C6,M7C3 and M6C) is controlled by carbon and chromium content. The results are as follows. (1)Tool life of endmilling is prolonged by decreasing carbide volume. It is affected by carbide size ; large primary carbide is more effective than small spheroidal carbide. (2)Cutting force FR and frictional force F are not affected by carbide volume and size at early stage of cutting (cutting length=0.2 m). On the other hand, FR and F increase with increasing carbide volume at finally stage (maximum width of flank wear is 500 μm). Large primary carbide is drastically increased both FR and F more than small spheroidal carbide. (3)The types of wear are the abrasive wear at tool edge and th e adhesive wear at clearance face. Volume of abrasive wear increases with increasing carbide volume. Large primary carbide remarkably increases the volume of abrasive wear more than small spheroidal carbide. (4)The changes in FR and F are due to volume of abrasive wear at tool edge. Volume of adhesive wear at clearance face can be estimated by frictional force F and cutting length.