57 - Heat Treatments to Develop High Strength Ferritic Ductile Iron

Abstract:

The influence of grain refinement on the strength of ferritic ductile iron was investigated. Alloys containing nominally 2%, 3% and 4% silicon were produced for this study. Various heat treatments were employed to produce both coarse and fine-grained ferritic structures. Hardness, tensile and Charpy impact properties were determined to characterize the effects of grain refinement. Various methods of heat treatment were studied. The three alloys were austempered at 385C (725F).

The austempered materials were then annealed between 540 – 732C (1000 to 1350F) to produce a finegrained, 100% ferrite matrix. Intercritical heat treatments were also performed to produce a fine-grained acicular microstructure.