Heat Treatment of Cast Iron:
Castings in iron are frequently heat treated for enhancing mechanical properties and microstructure. The treatments known to cast iron are explained briefly now.
Internal stress in cast material is very universal since every casting undergoes cooling that is non-uniform. After specific time period has passed, these internal stresses tend to be relieved approximately spontaneously. That self-relieving of stresses might causes modify in dimensions that may not be allowed for working of machine parts. Hence, it is imperative that cast material as parts must be stress relieved prior to bringing those parts in service. Cast iron is stress relieved through heating it to a temperature in the range of 400-500oC and maintained at this temperature for a few hours. The cooling is completed slowly or as for every rate for an exacting structure. Stress relieving of cast iron is submitted to as seasoning of casting.
Annealing of cast iron is heating this to a temperature between 800 and 900oC and cooling gradually. This procedure decomposes iron carbide in ferrite and machinability and graphite is enhanced. This may be essential for those parts such require machining.