VANADIUM STEEL. The desirability of adding vanadium to certain steels has been known since 1896, but it was too rare to be used until 1905 when a rich deposit was discovered in Peru. Since then many minor localities have been worked, so that while ferrovanadium is still expensive, owing to the difficulty with which it is reduced and refined, there is ample raw material for present use. Vanadium has a great chemical affinity for oxygen and nitro gen dissolved in steel; to avoid waste it is only added to dead melted steel after all other quieting additions have been made. Even so, some of it slags off, the residual analysis in engineering alloy steels being usually 0.15 to 0.25%. Vanadium forms very stable carbides in steel, reluctant to go into solution when heated above the critical temperature for quenching, and reluctant to accumulate into discrete particles on tempering. The first-men tioned property contributes to the maintenance of fine grain (toughness) over a considerable range of quenching temperatures ; the second contributes to strength and toughness at high operating temperatures. These actions supplement the characteristic effects of other alloys present.
Chromium-vanadium steels are now widely used for axle f org ings, clash gears and springs, where strength, hardness, impact and fatigue resistance are a requisite. The Society of Automotive Engineers' standards include several alloys with carbon from 0.15
to 0.55%, manganese from 0.50 to 0.80% (even higher with higher carbon), chromium from 0.80 to Pro% and vanadium from 0.15 to 0.25%. These low alloys will give about the same properties after heat treatment as the nickel-chromium steels (q.v.). Case hardened articles made of the lower carbon contents have intense surface hardness and wear resistance; to intensify the skin hard ness such steels are frequently quenched from a cyanide bath, and the vanadium is said to prevent the usual embrittlement caused by nitrogen.
Carbon-vanadium steels are mostly used in the annealed state for locomotive castings or forgings and are preferred over other alloys which must be heat treated, because subsequent heating at shops unequipped for precise work will not seriously reduce their strength. Locomotive frames of cast steel containing 0.20% vanadium have an elastic limit 25% above that of a similarly annealed plain carbon casting, without any loss in ductility. Loco motive side rods, driving axles and large shafting for electrical machinery or reciproCating engines are frequently forged of carbon-vanadium steels, made in the acid open-hearth furnace. Before machining they are usually air cooled from just above the critical range to refine the grain, and then annealed at just below the critical range to relieve all internal strains. (See IRON AND