Machinability of Nodular Cast Irons : Tool Forces and Flank Adhesion Phenomenon

抄録

Three grades of nodular cast iron (60, 80, and 100) were tested to determine the cutting and feed forces required to machine the materials, to determine the performance of several grades of carbide and ceramic cutting tools, and to investigate the flank adhesion phenomenon. Cutting characteristics for grade 80 and grade 100 were found to be the same as for high-strength gray cast irons with similar Bhn values. Flank adhesion, with accompanying sharp increases in cutting force values, was encountered only when grade 60 was machined with carbide tools. An attempt was made to correlate tool composition and flank adhesion. In order to determine the effects of cutting conditions on flank adhesion in detail, nodular cast iron grade 60 was machined dry and wet with cast iron cutting grade and steel cutting grade carbides. Decreasing the feed rate raised the critical cutting speed at which flank build-up occurred and lowered the resultant tool force. For tools with positive rake angle, the critical cutting speed was generally higher and tool forces were lower than for tools with negative rake angle. Large clearance angle eliminated flank adhesion. The use of cutting fluids prevented flank adhesion, and tool force patterns were smooth and smaller than those for dry cutting. Flank build-up was analyzed chemically and metallurgically. Methods to prevent flank adhesion are recommended.