Contribution in developing a rapid strategy in assessing hardened steel machining

Abstract

The present work is a contribution to developing a strategy for rapid analysis of the behaviour of surface roughness and tool wear during machining hardened steel with carbide cemented cutting tools on conventional cutting machines. In agreement with dies and mould manufacturers in East Algeria, the strategy is based on the machining potential of the manufacturers, cutting tools manufacturer’s guidelines and recommendations from literature. The agreement suggested to focus on up and down shoulder finish milling of hardened AISI D3 tool steel using GC1030 insert on a conventional vertical milling machine. The strategy has been developed within five successive steps starting from the analyses of the performance of a machine tool to the definition of an experimental plan to respect. As expected, results show that down shoulder milling is the most suitable process rather than up shoulder milling which must be avoided whatever the hardening condition. In addition, the best performance of down shoulder milling is obtained when machining unhardened steel. In the as-received condition (31.6 HRc) when using down milling the cutting speed can be increased up to the maximum value of 113 m/min, however, the tool life obtained for this value is three times lower than that at Vc = 59 m/min. In 49 HRc hardening condition, milling at Vc = 59 m/min resulted in the good surface finish but with a tool life 6.5 times lower than the tool life when milling in the as-received condition. Vibration measurements provide a time referential data on the evolution of surface roughness together with corresponding tool wear. A time referential data on the evolution of displacement together with the corresponding tool life has been proposed as useful information to meet the needs of dies and moulds manufacturers when milling hardened steels.