Heat treatment can be used to modify the properties of iron castings and/or to increase the consistency of the microstructure. Dexter Foundry can provide castings heat treated with the following cycles:

Stress Relief – A low temperature cycle which removes residual stresses which sometimes occur during solidification and cooling. The iron is heated to allow the material to “relax”, and then slow cooled. Stress relieving does not materially affect the strength or hardness of the casting.

Anneal – The iron is heated to allow carbon diffusion between the matrix and precipitated graphite particles. Slow cooling allows the carbon to migrate to the graphite resulting in a low carbon (soft) matrix. Generally used for 60-40-18 ductile iron. Also used on thin ferritic castings that may solidify and cool too quickly.

Normalize & Temper – The iron is heated to allow carbon diffusion between the matrix and precipitated graphite nodules. Rapid cooling in air results in a high carbon (hard) matrix. Castings are then reheated (tempered) to control the final hardness and remove stresses incurred during the cooling. Often used for 100-70-03 ductile iron. Frequently used when the casting will undergo localized hardening.

Quench & Temper – The iron is heated to allow carbon diffusion between the matrix and precipitated graphite nodules. The castings are quenched in a liquid medium (water or oil) to provide a very high carbon (very hard) matrix. Castings are then reheated (tempered) to control the final hardness and remove stresses incurred during the cooling. Usually used for 120-90-02 ductile iron.