STEEL 



909 



that employed in the Bessemer process, is mounted upon wheels, and travels upon a 

 railway, the ingot-moulds being arranged in a straight line in the pit below. 



According to the size of the furnace, the charge may be from 35 cwts. to 5 tons. 

 The materials used are good pig-iron, such as that employed for Bessemer steel-making, 

 wrought iron in the form of bars, malleable scrap, or Bessemer steel cross-ends and 

 waste, and spiegeleisen. The pig-iron is first melted, and the malleable iron or steel 

 is added in small quantities at a time ; care being taken to raise it to a white heat by 

 exposure to the stream of gas on the bridges before immersing it in the bath of molten 

 cast iron. 



The reversal of the gas- and air-valves takes place every 20 minutes. As soon as 

 the entire charge is dissolved, a sample of the metal is taken out in a small wrought- 

 iron ladle, and after casting, is cooled in water and broken. 



The heat is continued with an oxidising flame until the assay-sample, although 

 suddenly cooled, gives a perfectly soft and tough metal, indicating the point of total 

 decarburisation. When the spiegeleisen is added, care should be taken to charge it 



1911 



through the hole nearest to the bridge, which at the time is on the flue side of the 

 furnace. When it is melted, which usually takes about 20 minutes time, the charge 

 is stirred, in order to mix the contents as uniformly as possible : an operation which 

 must be done quickly, in order to prevent loss of manganese in the slag. The contents 

 of the furnace are then run into the ladle and cast into ingots in the usual way, the 

 same precautions being observed as in the Bessemer process. Usually three charges 

 are made in 24 hours. The yield per charge of 35 cwts. is from 32 to 33 cwts. of 

 ingots, the ordinary loss being 8A per cent., or in the most favourable case, about 6 

 per cent. The furnace must be let down for repairs at intervals of six weeks at the 

 longest. 



This process is of great advantage for the working-up of the waste of Bessemer steel- 

 works, which cannot safely be added to the charge in the converter ; a plan which has 

 been tried, but not with success. Puddled bars, made specially, cut into proper 

 lengths, and good scrap, such as that obtained in the neighbouring tin-plate forges, 

 are the principal forms of malleable iron used in South Wales. 



Another modification of the Siemens process consists in the use of finely-divided iron 

 in the spongy state produced by the reduction of a pure red or brown haematite by a 

 current of carbonic oxide at a red heat, instead of bars or other manufactured forms 

 of malleable iron. In the newest arrangement adopted for this purpose, the finely- 

 divided spongy iron produced in upright retorts is made to pass into a gas-furnace 

 witli an enclosed bed, where it is consolidated by immersion into a melted magnetic 

 oxide of iron, produced by the partial reduction of haematite, sufficient lime being in- 

 corporated with the mass to flux the silica of the ore. These agglomerated masses are 



