Research On Cutting Performance Of Turning Compacted Graphite Iron By PCBN Superhard Inserts

Vermicular graphite cast iron owns the advantages of both good casting properties of gray cast iron and high strength and abrasion resistance of nodular cast iron, which will be widely applied in high power engine in vehicle. However, due to the higher strength, higher toughness and the content of hard precipitation of TiC, the wear of cemented carbide cutting tools is severe with lower tool life.In this paper the PCBN inserts were used to turning the Vermicular graphite cast iron in order to investigated the effect of cutting parameters, the tip arc radius, the parameters of the chamfering and tool material on cutting force, cutting temperature and surface roughness. The morphology of tools’wear and the wear mechanism of tool in turning of vermicular cast iron with PCBN super-hard material cutting tool were examined. Finally, the turning chips of vermicular cast iron were observed, and the saw tooth mineralization degree of the chips was also investigated.It is shown that main cutting force is the largest among three cutting force, then axial force and radial force. With the increase of cutting speed, the cutting force is in a increasing trend. With the increase of feed rate, cutting depth and corner radius, the cutting force present a growth trends, especially with increasing of the cutting depth. Higher CBN content and smaller grain size produce a smaller cutting force. Among the three cutting parameters, the cutting depth owns the highest influence on the cutting temperature, the feed rate owns a least influence on the cutting temperature.It is shown that the cutting speed owns the highest influence on the tool life, and the cutting depth owns the least influence. With the cutting speed between 340-500 m/min,f =0.1 mm/min, ap=0.5 mm, the cutting insert has the highest efficiency and longest life without producing larger vibration.In the turning of vermicular cast iron with PCBN inserts, crater wear appear in the rake face and the main wear mechanism is oxidation wear and adhesive wear. Severer oxidation and adhesion wear of BN9000 and BNS800 is because that the binder of AIN may react with Si to form SiAlON. The wear of coated BNC500 insert is mild with the protection of coating. BN7000 owns W element in the binder, which inhibits the oxidation of the cutting insert wear. The abrasive wear is the main mechanism of flank.The main forms of chips are banding chip and serrated chip. The cutting speed has influence on the degree of curling. Cutting depth has great influence on the macroscopic shape. Small cutting depth lead to finer chip, and with the increase of cutting depth, burr increases as well as the chip width, with the more obvious serrated shape. With the increase of cutting speed, degree of segmentation slowly increase first and then increases sharply.