Vanadium - Transforming Possibilities

Vanadium in cast iron

Abstract:

The effects of vanadium in several types of cast iron have been investigated and the results are as in grey cast irons the marked strengthening of up to 0·5 per cent vanadium and its strong tendency to promote the formation of eutectic carbide have been confirmed. However, the carbide-forming tendency can be confined to thin sections by efficient inoculation or by modification of the base composition. The marked improvement in strength is still present in grey irons that have been annealed to a ferritic structure to facilitate machining.

Vanadium promotes the formation of eutectic carbide by: causing a significant increase in the metastable (carbidic) equilibrium eutectic temperature; causing a marked depression of the stable (graph/tic) equilibrium eutectic temperature. The addition of up to 0·5 per cent vanadium to nodular (SG) iron can produce significant increases in proof stress values and tensile strength. The most significant increases occur in irons which have been annealed to give a full ferritic matrix and the increases are accompanied by only a marginal decrease in elongation and notched impact values. It is concluded that ferrltic nodular (SG) irons with vanadium could have better combinations of tensile properties, elongation and impact resistance than previously accepted.

A very fine particulate precipitate occurs in ferritic irons when vanadium is added. This is believed to be a form of vanadium carbide, and it is suggested that it contributes to the increases in strength conferred by vanadium. In abrasion-resistant, 15 per cent chromium irons, 5 per cent vanadium content produces as-cast structures and hardness values similar to those normally obtained by high-temperature heat treatment of equivalent irons with no vanadium content. It is suggested that this effect of vanadium might be of use in complex castings that are subject to cracking during heat treatment.

Keywords:

vanadium, cast iron.

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