ON THE INFLUENCE OF SILICON ON THE PFOPERTIES OF STEEL. 269 



glazed pigs, owing to their peculiar glazed appearance when fractured. 

 It is curious that this very material — burntpig, as it was often called, and 

 only then made accidentally — was formerly thrown on one side as useless, 

 whereas now it is made purposely on a commercial scale and in large 

 quantities — another of the many proofs of the advantage of bringing 

 scientific knowledge to bear upon industrial metallurgy. Such ferro- 

 silicon in itself alone is perfectly useless in the refinery or puddling 

 furnace or for iron castings. The early samples of silicious iron seldom 

 contained more than from 4 per cent, to 6 per cent, of silicon ; but Mr. 

 Riley of London, in 1872, was the first to point out that rich ferro-silicon 

 was likely to play an important part in metallurgical industry. By 

 means of laboratory experiments he made in the crucible samples con- 

 taining as high as 22 per cent, of silicon. He also discovered that as 

 silicon increased carbon deci-eascd, until with 20 per cent, of the former 

 the latter was not present in quantities of more than f per cent, to 1 per 

 cent., and the greater part of this small auaount existed as graphite. 

 Spiegeleisen and ferro-manganese are the richest carbon alloys that can 

 be produced, and they contain about 6 per cent, of carbon ; ordinary cast- 

 iron rarely exceeds more than about 4 per cent., and never more than 

 about 4^ per cent. So strong, however, is the action of silicon in pre- 

 venting carburisation, even in the presence of a large excess of carbona- 

 ceous fuel, that in silicon- spiegel, an alloy of iron, manganese, silicon, and 

 carbon, and notwithstanding the presence of a lai'ge amount of manganese, 

 it — that is, the silicon — has still the upper hand, and prevents, as in the case 

 of ferro-silicon, carburisation taking place. A few typical analyses of 

 ferro-silicon, silicon-spiegel, ferro-manganese and spiegeleisen may be of 

 interest here (see Table I.) ; for a fuller description, and for the methods 

 of manufacture employed in their production, reference is given to Mr. 

 Holgate's admirable paper on ' The Composition of Ferro-Mauganese and 

 Ferro- Silicon made in the Blast Furnace.' The writer is indebted to that 

 paper for the analyses in question. Four of the samples quoted represent 

 Spiegel and ferro-manganese ; and it is interesting to note that as the 

 manganese rises there is a gradual increase of carbon up to as high as 

 7 per cent. A noteworthy fact is that if silicon, even in 50 per cent, 

 ferro-manganese, is allowed to reach 4 per cent, the carbon is at once 

 much reduced, in some cases to the low amount of about 2^ per cent. 

 This action is still more intensified in the alloys known as silicon-spiegel 

 or silicide of manganese, of which two analyses are given. From the 

 latter it will be seen that, provided the silicon exceeds 10 per cent., the 

 carbon is reduced to an exceedingly low point, and that although manga- 

 nese may be present even in comparatively high percentages this is quite 

 immaterial. This decrease of carbon takes place both in the combined 

 and graphitic form, but principally in the former. A very valuable 

 property of these spiegel alloys is the fact that they contain practically 

 no sulphur, the much-dreaded enemy of the steel-maker. 



It will therefore be seen that in the blast-furnace, somewhat strange to 

 say, silicon cannot be reduced without carbon is also present ; yet when 

 reduction of silicon occurs with the production of highly silicious iron, 

 carbon is practically absent in the resultant material. The late Dr. Percy 

 more than twenty years ago referred to this in his work ' Metallurgy,' 

 and said that according to his experience no reduction can take place 

 when silica and iron, without carbon, are heated together even at the 

 highest furnace temperature. Possibly this might now be accomplished in 



