steel. He states that both forged well, and were as malleable as pure iron, and that both gave a very beautiful damask when rubbed with sulphuric acid. From these results as to malleability, and also from the mixture used, the percentage of chromium must have been small. This damascening of chrome-steel is interesting when we consider that it is not producible with ordinary steel, and that it is only otherwise produced by taking extreme precautions in the working of the purer forms of malleable iron. 1 Schneider has shown that chrome pig-iron is not a homogeneous body, and the fact of the damascening being produced in the steel would indicate that the observation would also apply to it. Two alloys prepared by Berthier, one containing 1 and the other 15 per cent chromium, forged well, and made razor and sword blades of excellent quality.

M. Brustlein, of Unieux, France, commenced the manufacture of chrome-steel in 1875. Ferro-chrome is produced in crucibles and a certain proportion of this rich alloy is added to the steel. The usual specimens of the ferrochrome contain from 42 to 52 per cent of chromium. The metal is cast into iron moulds and chilled. The following table shows the composition per cent of different samples; and it is interesting to notice the large amount of carbon taken up by the alloys :

The remainder would be iron and silicon, the latter sometimes exceeding 2 per cent. The hardness and brittleness increase with the proportion of carbon and silicon. When ferro-chrome is cooled slowly it crystallises into a mass of needle-shaped crystals, which are more apparent when the carbon is low.

With regard to magnetism, chromium has a much less.

1 Oesterreichische Zeitschrift für Berg und Hüttenwesen, 1886, tom. xxxiii. p. 29.

powerful effect in destroying the magnetic properties of iron than manganese, for iron containing 65 per cent of chromium is still attracted by a magnet.

In the manufacture of steel, varying proportions of chromium may be used. Brustlein states that steel containing 2 per cent carbon and 12 per cent chromium may be forged. The presence of chromium in steel increases its tenacity and imparts a higher resistance to pressure. It also renders steel harder to file or work on the lathe in proportion to the quantity of carbon present. Hardened steel containing chromium has a very fine grain, and breaks with a glassy fracture. Chrome-steel cannot be welded; it burns when highly heated, owing to the strong affinity of chromium for oxygen, and the oxide formed is infusible even at the melting-point of steel. From the above table it will be seen that ferro-chromes may be combined with exceptionally large proportions of carbon, and they may in consequence be used instead of ferro-manganese in making Bessemer or Siemens's steel. But extra soft steel, containing much chromium, is at present impossible. If ferro-chrome be made, having little carbon, it is very oxidisable, and almost infusible, so that many difficulties stand in the way of supplanting ferromanganese by ferro-chrome.

§ 183. Iron and Titanium.-Pig-iron sometimes contains titanium, when obtained from ores containing that metal, which often occur along with iron ores. The titanium is either minutely disseminated through the iron or alloyed with it. Some analyses by Mr. Riley of gray pig-iron from Wiltshire gave 1·15, 71, and 47 per cent of titanium respectively. But iron smelted from titaniferous iron-ore may be quite free from titanium. 1 In 1877 Mr. Riley showed that the so-called titanium steel of Mushet 2 contained no titanium. Faraday failed to reduce titanium oxide, although he states that rhodium, and, imperfectly, platinum were melted

1 Iron and Steel Institute, 1887.
2 Mushet's patents, 1859 to 1861.

in the crucibles he used. In 1742 Mr. Horne successfully smelted the titaniferous ores of Canada, and good steel was made from them, the virtue of which was ascribed to this particular ore, although this was before titanium had been isolated as an element. It is a noted fact that titanium iron ores are practically free from phosphorus, which may readily account for the good quality of iron produced therefrom. We may consider then that titanium steel exists only in name. What titanium occurs in the pig-iron passes into the slag when the iron is refined.

§ 184. Iron and Tungsten. These metals unite to form some valuable alloys. Steel containing tungsten is highly valued for cutting tools. Formerly, the oxide of tungsten and carbon were melted in crucibles with Swedish or good hematite pig-iron. The steel is now made by introducing a rich alloy, containing up to 50 per cent of tungsten, into the crucible or bath of metal. Tungsten steel is known in England as Mushet's special steel. It possesses a natural hardness of its own, and, when upwards of 3 per cent of tungsten is present, instead of being hardened by heating and quenching in water, like ordinary steel, it is actually softened. It is very difficult to forge, and cannot be welded when the tungsten exceeds 2 per cent; but can be cast into the form of tools, which can be ground to a fine edge. Tungsten gives to steel a very fine and uniformly crystalline structure, and such steel is less affected by the atmosphere than ordinary steel. 1 Mr. Stroh states that tungsten-steel possesses remarkable magnetic properties. He uses a 3 per

cent tungsten alloy for telephone magnets with marked advantage. It is stated by several experimenters that tungsten imparts to cast-iron great hardness and tenacity, but Guettier found no advantage in adding tungsten to cast iron as regards resistance to shock or flection. The general concensus of opinion appears to be that tungsten in steel is valuable for certain purposes, but that the general method of 1 Transactions of Soc. of Telegr. Eng. 1882.

obtaining it is too expensive to make its manufacture on an extensive scale a commercial success. Sieward examined six samples of tungsten steel: four of them contained from 1 to 3 per cent tungsten, while none was found in the other two. The best results are obtained when the alloy is reduced from iron ores containing a little tungsten oxide. The difficulties in making stable alloys with tungsten are increased in consequence of its high melting point, and high specific gravity.

§ 185. Iron and Copper.1 Guettier states that the alloys of iron and copper are difficult to procure by direct fusion of the metals. The copper remains in a pulverulent state within the iron, has a tendency to become precipitated to the bottom of the fluid mass, or in the moulds, and the combination is generally incomplete. Copper imparts to cast-iron a grayish lustre, probably due to uncombined copper.

Copper is considered very injurious in iron and steel even when present in minute quantity, but the late Mr. Willis of Landore stated that 1 per cent of copper produced no appreciable effect on the quality of steel. The injurious effects attributed to copper are very marked when sulphur is present in notable quantity, making the metal red-short. M. Choubly of the Firminy Steel Works has experimented on phosphoric steel containing copper, and he states that a metal containing 5 per cent of carbon, ·15 phosphorus, 04 sulphur, and 1 copper rolled perfectly well.

2 Messrs. Ball and Wingham have investigated the influence of copper on the tensile strength of iron and steel. An alloy containing—

very hard, but Varying quan

was bright, white in colour, crystalline, and did not offer any great resistance to impact. tities of the alloy were melted down with Bessemer steel, and test pieces 1 inch by inch by inch were annealed and tested. The following table shows the results :—

3 18

From these experiments it is clear that copper increases the tensile strength of iron. The simultaneous presence of carbon assists in the more intimate association of copper with iron. In test-piece No. 1 the fractured surface was somewhat fibrous, while No. 2 and the others were highly crystalline. Even in the absence of carbon copper makes iron extremely hard.

Mr. F. Stubbs states that the presence of per cent of copper in steel gives it the property of preventing the oxidation of the steel on being subjected to a burning heat.

§ 186. Iron and Tin.-These metals may be alloyed together in several proportions, but the combinations are brittle, and the fusing-point diminishes with the proportion of tin. A small quantity of iron in tin imparts greater hardness and a duller lustre. A small quantity of tin in iron renders it cold- and hot-short. Cast-iron containing tin may have as fine a fracture as that of steel. It becomes black, is capable of a fine polish, and less tarnished in air than ordinary cast-iron. A proportion of 2 per cent of tin in cast-iron renders the metal dry and brittle, and the iron puddled from such pig-iron is hard and less malleable. The following alloys have been studied by Guettier1 :— 1 Guide Pratique des Alliages, 1865.