Evaluation of different cutting tool materials for the interrupted machining of compacted graphite cast iron

摘要

It is clear from the current milling test results as well as a review of the literature on continuous cutting that one should distinguish between milling and turning operations in terms of optimum machining parameters and tool materials. In continuous cutting of CGI there is currently no tool material that can provide a high speed machining solution. Multiple insert tooling at low speeds allow automotive manufacturers to achieve the necessary cycle times. This machining solution can also be applied to grey iron machining, which means that both CGI and grey iron can be machined on the same transfer-lines. Certain PCD grades are the only material capable of offering a moderate cutting speed solution for CGI. PCD is able to machine at double the speed of carbide and can achieve a 10-20 fold increase in tool life. From the CGI milling results it is evident that certain PCBN grades are capable of offering a high speed machining solutions while still achieving an acceptable tool life. The PCBN wear scar images at 300 m/min and 800 m/min suggest that the PCBN tools fail by fracture and not by abrasive wear as in turning applications. At moderate speeds (<400 m/min), PCD 2 achieves double the life of PCBN 3 and around 20 times that of coated carbide and Si_3N_4-based ceramics. PCD 2 would therefore be the preferred material at the lower speeds and PCBN 3 at higher speeds. Coated carbide and Si_3N_4-based ceramics were not suitable for milling CGI at cutting speeds above 300 m/min. The optimum conditions for these two materials will be somewhere below 300 m/min.