The Effect of Machining Variables on the Machinability of Turning/Boring Compacted Graphite Iron

摘要

Compacted graphite iron (CGI) has been found to be the optimum material for diesel blocks and heads. CGI offers superior strength characteristics but lower machinability compared to gray iron. The reduced sulfur content of CGI prevents the beneficial formation of a protective manganese sulfide layer on the cutting insert in grey iron machining. The longest tool life penalty of about 90% has been documented with continuous cuts such as cylinder boring. It is necessary to identify solutions for machining CGI at similar speeds as gray cast iron. This paper describes machining investigations using several new coated carbide grades and polycrystalline tools, insert geometries, and cutting conditions. The wear mechanisms, tool wear and tool life were investigated. The cutting forces were measured, while the tool temperature was modeled using 2D FEM to estimate the temperature in the cutting zone to be related to tool wear mechanisms. A better understanding of tool wear mechanisms will help the advancements in tool material, coatings and designs. The limitations of the current technologies will be discussed.