Vanadium Steel:
Page 18
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When the process is observed to be completed, according to experience, the crucible is allowed to cool, and a ferrovanadium is obtained of varying percentages. The results of either method of reduction are not essentially different, and alloys of iron containing up to 82 per cent, of vanadium, and other constituents of minor importance, have been obtained.
Pure vanadium is a silvery-white metal of very high meltingpoirit-abeut 2,000deg. C Its specific gravity is somewhat low -i.e., 5.5. The preparation of the pure metal is attended with great difficulty, and can only be attempted in the laboratory. Moissan, even with an electric furnaoe, was unable to obtain pure vanadium ; only its alloys were possible. Among the earlier recorded experiments in directly alloying iron with vanadium are those of M. Helouisalwho from the admitted abnormal ductility of Swedish iron, and also from the fact that Staffordshire slags often contained much vanadium, while the iron made from Staffordshire pigs also had high ductility, thought if vanadium were added to steel, it ought to toughen it. Other experiments were necessary, but those made by al. Helouis showed that vanadium increased the tensile strength and reduced the elongation of steel. Further, that when i per cent, of vanadium was present, the steel, though extremely soft, was capable of attaining a great hardness on chilling. In order to test the effect upon steel, a mild steel free from phosphorus, with a tensile strength of 30 tons per square inch and 17 per cent, of elongation, was melted in a graphite crucible. It thereupon became carbonised, and showed 61 tons tensile and 23 per cent. elongation. On adding x per cent, of vanadium the tensile was raised to 69 tons, with an elastic, limit of 5o tons, and 7.3 per cent. elongation. The same steel, when melted in a non. graphitic crucible, in order to avoid the absorption of carbon, gave the following results 011 adding the percentages of vanadium shown :
Tensile Strength. Elongation Tons per per cent, square inch,
.5 p.c. vanadium, unan nealed 42.0 16
en p.c. vanadium, unannealed ...... 61.5 14 1.0 P.C. vanadium, annealed 45.0 20 The latter metal, although very soft when annealed, became extraordinarily hard by tempering. Ordinary malleable iron of about 24 tons tensile and 19 per cent. elongation, was changed by the addition of 0.5 per cent, of vanadium to 39 tons tensile and 12 per cent, elongation in the forged bar, and 3,3.7 and 32 per cent, elongation when annealed. These results, therefore, attracted considerable attention on account of the remarkable malleability and ductility shown. Tests were also carried out at the Firminy Steel Works, famous for its experiments on chrome steels. Many of the earlier results obtained at Firminy were negative. One alloy showed a very high resistance to shock, and the tensile strength was also high. Another specimen gave the following results:
Original steel 30 17.0 Ditto, with x p.c. vanadium 6x 14.0 Ditto, with x p.c. vanadium, annealed 45 20.0
Professor Arnold found that on quenching the steels obtained, the metal showed a remarkable strength for cutting tools. A tool was made of the following composition : Carbon, 1.02 j vanadium, 0.29; and compared with a special steel containing 1.2 per cent, of carbon and 3 per cent, of tungsten. It was found that the vanadium steel kept its hardness at a visible red heat. Tools were then made with 3 per cent, of vanadium' and compared with a 3 per cent. tungsten tool. Both were tested on a chilled -white iron plate, and the cuttings obtained during a ten minutes' cut were collected and weighed. The vanadium steel had surpassed the tungsten tool in the proportion of 75 per cent.
The results of these experiments being so remarkable in the history of steel manufacture, further investigations were pursued with vigour, and in 1902 Professor Arnold continued his researches and obtained results which are the property of the New Vanadium Alloys Company, who have now for some years been associated with Messrs. Willans and Robinson, of Queens Ferry, Flintshire, to whom, together with Mr. Kent-Smith, I am indebted for many particulars, and for the fine collection of samples which I am privileged to show you this evening. The investigations and immense labour which have eventuated in these triumphs of steel making are partly indicated in a paper read before the Institution of Mechanical Engineers in December, 1904, by Captain H. Sankey and Mr. J. Kent-Smith.
These steels are alloyed with a small percentage of chromium, and some reference must be made to the effect of this element. Chromium is largely used for armour-plate and projectile work, and as an illustration of its hardening effect I may quote from a paper by Mr. Hadfield, read before the Iron and Steel Institute in 1892. Speaking of chromium steel shells, Mr. Hadfield says: " Although principally makers of small calibres as regards armour piercers, one of these experimental shells, 13.5in.5 weighing 1,1201h., fired from a 63-ton breech-loading gun at a velocity of 1,95oft. per second, penetrated an i8in. compound armour plate, a 6in. wrought iron plate, 2oft. of oak backing, a further iolin. wrought iron plate, and was then found broken beyond a zin. wrought iron plate--that is, a total penetration of 36fin. of armour plating." In another instance, quoted in the same paper, a 6in. projectile was fired through a 9in. compound plate. Being uninjured, it was ground up true, and fired again through another 9in. compound plate. It was again ground up, and fired a third time through a 9in. plate, when it broko up. This last plate, however, had been specially hardened by special means, and probably the shell would have passed through the third plate if it had been of the ordinary compound type. I give these illustrations to show some properties of chrome steel, and while for other classes of work such metal as was used would be quite useless, it is clear that, judiciously harnessed, the properties of chromium may be advantageously applied to mild steel. This has already been done, and much chromium steel is in use for tyres, axles, and constructional purposes, and it is an important ingredient in Messrs. Willans and Robinson's steels. As to the respective properties of chromium and vanawdieulml in the compound steel, the following table illustrates this