Clean iron production and machining technology. Year 1 summary report, January 1--December 31, 1995

The first phase of this project was conducted to develop a technique for evaluating the machinability of gray and ductile iron. That technique was then used to measure the machinability of a variety of irons and determine the processing factors that influenced and controlled machinability. The procedure developed to evaluate machinability involved drilling holes with a feed rate of 0.009 in/rev at various surface speeds. High speed steel drills were used so wear was observed more quickly. Microcarbides present in the irons were found to dominate the machinability. Pearlitic irons considered to have ``acceptable`` machinability (indicated either by tool life measured in the laboratory using high speed steel (HSS) drills or reports from commercial machine shops using other cutters) were found to contain from 8.9 to 10.5% by weight microscopic carbides. The tool wear rate increased when machining at higher surface speeds or machining irons containing higher weight percentage of microcarbides. All irons containing above 11.5% microcarbides consistently exhibited poor machinability. Tool wear results obtained using cubic boron nitride (CBN) cutters paralleled those obtained with HSS. Higher iron microcarbide concentrations produced faster tool wear. Experiments are now being formulated to explore methods of improving iron machinability. Future work will extend the study to ductile irons