Improvement of Low Carbon Steel Properties through V-N Microalloying
To improve the strength properties of vanadium bearing low carbon steel, nitrogen is often added to the liquid steel. The source of the nitrogen addition can be in many different forms. The recovery of nitrogen from the addition is variable due to the low solubility of nitrogen in steel. In this work, nitrogen-enriched alloy (Nitrovan) was added under open atmosphere. To deduce the nitrogen role, two alloys were chosen that having the same vanadium content. One of them was Ferro-Vanadium as a source of vanadium, whereas Nitro-Vanadium used as a source of vanadium and nitrogen. Ferro-vanadium as well as Nitro-vanadium was added separately in the ladle after completely melting of carbon steel and proper superheat using 100 Kg induction furnace. The effect of adding nitrogen-enriched alloy on mechanical properties of the steel was investigated. For this purpose, four heats were produced and cast into sand moulds. The general trend of results shows higher mechanical properties through increasing nitrogen content. The experimental work indicates that enhanced nitrogen content promotes the precipitation of V(C,N) and decreases the particles size of V(C,N) precipitates. Also, under the same level of vanadium content, the tensile strength and yield strength of the nitrogen-enhanced steels increases consistently compared to the steels added 80% Ferro-Vanadium. An empirical formula, correlating the mechanical properties of the steel and its composition, was obtained.
J.M. Rodriguez-Ibabe, I. Gutiérrez, B. López and A. Iza-Mendia
I. H. M. Ali et al., "Improvement of Low Carbon Steel Properties through V-N Microalloying", Materials Science Forum, Vols. 500-501, pp. 503-510, 2005