Vanadium - Transforming Possibilities

High Strength Cast Irons Containing Vanadium Annealed Ductile Irons and High Carbon Grey Irons

Abstract:

The inclusion of up to 0.5 per cent vanadium in annealed ferritic ductile iron produces a marked increase in tensile strength while further increases can be obtained by adding up to 2 per cent nickel to the vanadium iron. The increases occur with very little reduction in elongation and only a small increase in the notched impact ductile/brittle transformation temperature. The improvement in tensile properties is greater than can be obtained with most other alloy additions while the effects on elongation and impact properties are significantly less than produced by other alloy additions.

It is suggested that the combined addition of vanadium and nickel to annealed ferritic ductile iron should facilitate the production of irons of considerably higher strength which retain a high level of ductility well below ambient temperatures.

The tensile strength of grey iron is increased considerably by the addition of up to 0.5 per cent vanadium and irons of much higher carbon contents than normal can be produced with strengths similar to those of the current lower carbon engineering irons. The chilling tendency of the high carbon vanadium iron is low and can be reduced to a very low level by the addition of up to 1 per cent copper. Furthermore, the coarse, graphite structure associated with high carbon grey irons is refined by the vanadium.

Using a thermal cycling test rig it is shown that the high carbon irons have considerably better resistance to thermal fatigure cracking than normal engineering iron. It is suggested that the ability to produce engineering irons of adequate strength but with improved resistance to thermal fatigue might constitute a significant advantage when producing castings subjected to mechanical stress and thermal fatigue such as brake rotor castings.

Keywords:

vanadium, cast iron.

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