Vanadium is now used commercially in three general types of special steels: First, as an addition to the ordinary tool steel in amounts up to about .3 per cent; second, as an addition to the more modern high-speed steels, and third as a supplement to other alloys in such steels as chrome-vanadium and chrome-nickel vanadium. Vanadium imparts to steel an in creased tensile strength and elastic limit and when annealed improves the ductility greatly.
Silicon has proved itself to be an advanta geous addition to steel for a variety of purposes, Casper and Oertel have patented in Germany a chrome-silicon steel, the silicon being greater, less or equal in quantity to the chromium. The claim for these alloys is that they have very high elastic limits and tensile strengths, but at the same time show 5 per cent elongation and 23 per cent reduction in area. When hard ened and tempered they are said to be excep tionally good for machine parts, weapons, wire rope and springs. In general, silicon up to 0.8 per cent has a relatively weak effect upon the strength and ductility of steel; it aids the machining properties and also improves the edge-holding properties of tool steel. When high in amount it becomes injurious to annealed steel because it tends to cause a separation of graphite, as may be noticed from the dark ap pearance of the fracture. Recently as high as 3 per cent silicon has been observed in certain high-speed steels, and Jacob Holzer and Com pany (Unieux) patented many years ago a spring steel of the following composition: Si,• 1.8 to 2.2 per cent ; C, 0.35 to 0.45 per cent; Mn, 0.45 to 0.55 per cent This steel is hardened at the unusually high temperatures of between and 1000° C.
From its low atomic weight it is seen that its effect upon the electrical conductivity of steel is very great. It raises the resistivity of mild steels about 100 microhms per cubic centi meter for each per cent added so that a silicon steel containing 4.5 per cent silicon has a re sistivity. of 59 microhms per cubic centimeter. From the work of Gumlich, Yensen and Ruder, it has been found that the first effect of silicon is to act as a deoxidizer, its presence in small quantities indicating its excess over the amount of removable oxygen originally present and, therefore, explains the first peek in the per meability curve and depression in hysteresis value. From this point on to about 2 per cent the silicon merely acts as a diluent causing a steady drop i in saturation value and permeabil ity and an increase in coercive force. At about
2 per cent, however, its influence as a grain growth stimulator becomes evident and there is a consequent rise in permeability and decfease in coercive force. This effect reaches a maxi mum and from this point onward any added silicon again acts as a mere diluent. This ef fect of silicon upon the permeability is of vast commercial importance and many of the most magnetically permeable steels are silicon alloys. Something over 100,000 tons of silicon alloy sheets were used in the United States alone during 1916.
Nickel steels melt at a lower heat than the corresponding carbon steels; there is less segre gation in them and there seems also to be less tendency to form blowholes. Nickel-steel forg ings though tough are not difficult to machine. From 3 to 3.5 per cent Ni in a 0.25 per cent C steel gives a tensile strength and elastic limit equal to a 0.5 per cent C steel but still retains 25 per cent elongation. Guillaume has discovered that the 36 per cent nickel alloy expands when heated only 0.000001 millimeter per 1° C, or only one-twelfth as much as pure iron. This property has suggested its use in pendulums, measuring rods, chronometers, etc., and its non-corrosive nature makes it still more value for such uses. Theodolites, leveling instruments and other ap paratus of the United States Coast and Geodetic Survey are to be made of this alloy. Another very important application of nickel steels is suggested by- the anomalous expansibility of this alloy. By adding either iron or nickel to it, alloys of almost any degree of expansibility result. Charpy and Grenet have shown that an alloy containing 36.1 per cent Ni, 0.39 per cent C, and 0.39 per cent Mn, not only has an ex tremely low coefficient of expansion, but that it is practically constant between 15° and C.
Manganese steel is in some respects analo gous to nickel steel. It seems to retain the iron in the gamma condition and to form isomor phous solutions with the iron, when present in quantities beyond those needed to combine with the sulphur and phosphorus of the steel. Nickel (25 per cent) gives an alloy which is practi cally non-magnetic; but when cooled strongly becomes powerfully magnetic and remains so when warmed up to the normal temperature. Hadfield's manganese steel containing 13 per cent manganese and 1 per cent carbon is but slightly magnetic and the amount is nearly con stant for strong or weak magnetic fields. There is no appreciable residual magnetism.