Tool life tests were conducted and established that a number of factors affect the machinability of ductile iron.
1. Analyzing the advantages of ductile iron – It shows higher strength characteristics to grey iron – proven by its resistance to cracking even when hit with a heavy sledgehammer all day.
2. It has tremendous wear resistance on account of the presence of the graphite in the iron, which wears much slower compared to any other metals when you rub any object against it.
3. Ductile iron can also dispel heat very well and is easy to machine.
4. Another characteristic is that it can dampen vibration and gives out a sound that sounds better than steel.
Ductile iron has the following machining advantages as seen in SG iron foundries as compared to steel:
1. Greater depth to diameter drilling ratios
2. Faster feed rates
3. Higher spindle speeds
4. Extended tool life
When comparing intermediary-strength grades, ductile iron has better machinability than steel because:
1. The high amount of silicon in ductile iron decreases the toughness of the ferrite (the metal matrix component).
2. The graphite spheres give ductile iron its free-machining properties due to lubrication by the graphite.
These two properties are why ductile iron has greater depth diameter drilling ratios, faster feed rates, higher spindle speeds and extended tool life.
CNC machining of ductile cast iron