356 STEEL Among the elements other than carbon met with in steel are phosphorus, silicon, sulphur, and oxygen among the non-metals, and man- ganese, copper, tungsten, titanium, and chromi- um among the metals. Some of these are in- variably present in the materials used for steel making, and are usually regarded as impurities in the steel, while others are added to produce certain specific effects. The modifications of the properties of steel by the above named elements have been already treated partially under IRON. Steel is more susceptible to the action of impurities than is wrought iron. This is especially true with regard to phosphorus and silicon, and is readily accounted for by the similarity of action of these substances with carbon. Recent experiments have shown that an amount of phosphorus which would be highly detrimental to steel containing say 0-50 per cent, of carbon, may be present with safety when the carbon is as low as 0*10 or O20 per cent., or in other words when the steel passes into soft iron. The effect of this formerly much dreaded enemy of iron and steel has been so thoroughly studied that " phosphorus steels," so called, are manufactured and sold. Phosphorus makes iron hard, brittle, and cold- short (see IRON), and this is also true in a modi- fied degree of carbon and silicon ; hence, when two or all three are present together in iron, the effect is cumulative. The contradictory statements as to the maximum percentage of phosphorus that Bessemer metal will bear find here their explanation. It was formerly said that Bessemer steel with more than 0*05 per cent, of phosphorus was unfit for rails, but later experience has shown that if the amount of carbon does not exceed 0'15 per cent., phos- phorus to the extent of 0*35 per cent, may ex- ist without seriously impairing the strength and ductility of the metal. This fact, recently brought into prominence by the manufacture in France of phosphorus steel on a large scale, was recognized in this country as early as 1870. Samples of boiler plate and tough steel made at Trenton, N. J., by the Martin process, showed on analysis the following composition : ELEMENTS. 1 2 8 4 5 Carbon. . . Sulphur 0-160 0-008 0-120 0-008 0-120 O-OOT 0-125 0*120 Phosphorus 0-580 0*118 0*275 0*814 0*272 Manganese 0-144 0*580 0*072 Silicon . 0"174 0*015 0*025 .... While it appears from the above that phos- phorus may in a measure replace carbon in steel, the effect of these two substances is not identical, and the limit of rigidity is much sooner reached with the former than with the latter. The use of phosphorus steel is solely a question of economic advantage, since its manufacture permits the use of impure and consequently cheaper materials ; but as far as is at present known, the compounds of iron and phosphorus possess no properties that give them a superiority over the carbon compounds for industrial applications. The effect of sili- con on steel appears to be similar to that of carbon, as the general analogy of the two ele- ments would suggest ; but to produce a given degree of hardness, the amount of silicon neces- sary is very much greater than that of carbon the reverse of the case with phosphorus. The most contradictory statements exist regarding the effect of silicon on steel. The best estab- lished data are summarized by Turner as fol- lows: A small amount of silicon is not neces- sarily injurious to steel, and may be an advan- tage in those varieties which are to be used without hardening, and where there is no spe- cial demand for tenacity and strength. On the other hand, where steel must be hardened for use, as for tools, silicon can only be injurious, and that in proportion to the quantity present. This is one reason why Bessemer steel cannot generally be used for purposes requiring a fine, hard steel ; for it is usually made from highly silicious pig iron. But some of the Swedish Bessemer steel, made from pure manganiferous pig iron low in silicon, approximates in quality to ordinary cast steel. A puddled steel made with the addition of a highly silicious iron ore has been brought into prominence under the name of " silicon steel ;" but there is no evi- dence that it derives any of its properties from silicon, or indeed that there is any more silicon in it than in ordinary puddled steel. The ef- fect of sulphur on steel is entirely different from that of the elements already mentioned. It makes it " red-short," that is, brittle when hot ; but unlike phosphorus, it does not sen- sibly affect its malleability when cold. The largest amount of sulphur that steel will bear without serious impairment of its malleability is said to be about O'lO per cent. Oxygen produces the same effect on homogeneous iron as sulphur, as might be inferred from the close chemical relations of the two elements. It can never exist in the harder steels prepared by fusion, for it would then combine with the carbon ; but it is frequently met with in the Bessemer low steels and iron, and makes them red-short. Red-shortness, formerly ascribed exclusively to sulphur, has been found in very many instances to be due to oxygen. Consid- erable importance has been attached to the presence of nitrogen in steel, and Fremy con- siders it an essential ingredient. Numerous analyses do not support this view, and it is probable that its presence in steel is entirely accidental and due to the property which many metals possess of absorbing or occluding gases. The compounds of iron with the metals, or the true alloys of iron, have not been as closely studied as its compounds with the non-metals, and but little can be said with precision of the physical characters of these alloys as such, or as modified by the presence of the non-metallic elements. The properties of iron are not as radically modified by the addition of small quantities of metals as is the case with the
