380 BEPOET— 1889. 



as regards ferro-chrome, it is only when very high percentages of chro- 

 mium are reached that the material is not susceptible. 



Malleable ferro-alloys. — Malleable compounds of iron with other ele- 

 ments so far experimented upon (including carbon, silicon, sulphur, 

 phosphorus, chromium, tungsten, aluminium, and nickel) are strongly 

 susceptible to magnetisation. 



Alloys of manganese and iron, however, form an exception to this. 

 As is now well known in manganese steel, as soon as the manganese 

 exceeds 8 or 9 per cent, the material is only attracted when in a finely 

 divided state, such as drillings or powder, and with further increase of 

 manganese even this slight susceptibility disappears. The same fact is 

 noticed as regards the non-malleable compounds of iron and manganese. 

 Alloys of iron, nickel, and manganese are also uot susceptible. 



2. Cast State. — As might be expected, the whole of the samples are 

 very free from honeycombs ; but this soundness in the cast state is only 

 acquired at the expense of toughness or ductility. As regards this free- 

 dom from honeycombs, it may be of interest to state here that although 

 silicon does produce soundness in steel, yet Mr. Holgate noticed that in 

 making ferro-silicon of 13 to 15 per cent, there is in casting an unusually 

 large outburst of gas, and the pigs are exceedingly full of honeycombs. A 

 sample is exhibited among the specimens accompanying this paper. In 

 watching a cast of material of this percentage from the blast-furnace he 

 noticed that when the exterior of the pigs became almost solid, and whilst 

 the interior was still liquid, the metal began to boil up, and frequently for 

 fifteen or twenty minutes some cwts. of metal in each bed boiled over, this 

 going on until the pigs were quite set and solid. 



It would be interesting to know what is the cause of this outburst, and 

 the composition of the escaping gases. It has been stated in metallurgical 

 literature that in some hot overblown Bessemer charges silicon may be 

 present in considerable percentages and yet the steel rise or boil over 

 when poured into ingot-moulds. 



Silicon steel pipes or settles to a much greater extent than ordinary 

 steel, and this in itself is a considerable disadvantage. Its fluidity when 

 being poured is less than that of ordinary steel. The crystallisation or 

 form of fracture of the lower percentages is somewhat like ordinary mild 

 cast steel, but on exceeding about 2^ per cent. Si, a striking change occurs : 

 the crystals become very large, glazed in appearance, and cleave somewhat 

 after the nature of a spiegeleisen. As this large aiid marked crystallisa- 

 tion increases the material becomes exceedingly brittle, and if still further 

 additions are made tlje appearance of the material approaches silicon pig- 

 iron, and is non-malleable. 



High percentages of silicon in the cast or unforged material cause a 

 considerable increase in shrinkage or contraction. This point is already 

 a difficult one with the steel founder, who for many years has been on the 

 horns of the dilemma that whilst silicon increases soundness it increases 

 the tendency of castings to draw. In cast-iron this fact of silicon also 

 increasing contraction has been noticed by Mr. Keep. 



Also as in the forged, so in the cast material, when the Si exceeds about 

 2 per cent., and the peculiar crystallisation noticed in the samples exhibited 

 commences, neither annealing nor water- quenching seems to have any 

 efiect in changing the structure. 



It is well known that considerable difficulty is experienced in dis- 



