Effect of alloying on the features of crystallization and on the structure of cast vanadium-containing steels

Conclusions

• 1. On account of considerable dendritic liquation the crystallization of vanadium-containing steels even with low vanadium content (approximately 0.12%) may be accompanied by the formation of eutectic vanadium carbonitrides with variegated morphology: coarse boundary segregations and point-type "carbide rust spots."

• 2. When steel contains 0.25% C, the lower concentration limit of formation of carbide eutectic in regard to vanadium in castings with section 50 mm amounts to 0.33%. When the carbon content increases to 0.85%, this threshold drops to 0.12%.

• 3. The amount of carbide eutectic depends largely on the speed of crystallization which is determined chiefly by the section of the casting. By its effect on the amount of eutectic carbides, an increase of the diameter of the casting by 50 mm is equivalent to an increase of the vanadium content of the steel on an average by 0.20%.

• 4. In the complexly alloyed steels 150KhNMF and 150KhNMFT the process of crystallization may be accompanied by the segregation of carbides with eutectic morphology, with complex composition, type (V, M)C. In dependence on the alloying, complex carbides contain, in addition to vanadium, also chromium, molybdenum, and titanium.