44 PYROMETALLURGY. [ill. 



this process. The decrease is not in the (graphitic) carbon 

 insoluble in acids, but in the chemically combined portion. 



Steel from Cast-iron. — The conversion of cast-iron into steel 

 is desirable, if it can be effected rapidly and economically ; 

 for articles might be cast directly from a blast-furnace or a 

 cupola, and then steeled to a greater or less depth, without 

 altering their form, inasmuch as only a small quantity of carbon, 

 a small percentage of the weight, is required to be removed. 

 For a large number of purposes, this steeling need not proceed 

 to a great depth, especially where toughness of body is not a 

 requisite. 



Attempts have been recently made to effect this decarbon- 

 ization of cast-iron by burning off a part of the carbon in 

 cast-iron, since it is known that the intermediate qualities of 

 steel between bar and cast-iron are due to its intermediate 

 state of carbonization. Riepe's process (Lond. Journ. Oct. 

 1850) is a modification of the process for decarbonizing cast- 

 iron in a puddling-furnace by regulating the heat in the finish- 

 ing process, and adding iron towards the latter part of the 

 process. He also proposes imbedding cast-iron in clay and 

 keeping it at the welding heat of steel, to effect the same pur- 

 pose ; and still further, the oxidation of castings by atmo- 

 spheric air. The process of making malleable castings is also 

 based on the same general principle. Such processes, as far 

 as we know, can only produce inferior qualities of steel, al- 

 though they may possibly produce a material having exactly 

 the due quantity of carbon ; for as the metal is subjected to a 

 comparatively small amount of working, a considerable propor- 

 tion of the impurities, silicium, phosphorus, sulphur, metals, &c. 

 will remain in the mass and deteriorate the quality of the 

 metal. The superior quality of steel is mainly due to a more 

 or less perfect removal of injurious constituents, while, at the 

 same time, much iron is oxidized and removed. By any of the 

 processes yet known, it is impossible to avoid labor and loss 

 of iron in making steel, and these seem to be in direct pro- 

 portion to the quality of steel to be made. Late examinations 

 by Miller of castings rendered malleable by cementation, 



