PROPERTIES OF STRUCTURAL METALS. 41 



The basic Bessemer process is identical with that just 

 described, except the converter or furnace is lined with a ma- 

 terial that resists the action of the basic slags. Again quoting 

 from the " Manufacture and Properties of Structural Steel": 

 "This lining is usually made of dolomite, but sometimes a 

 limestone is used containing a very small proportion of magne- 

 sia. The stone must be burned thoroughly to expel the last 

 trace of volatile matter, and then ground and mixed with an- 

 hydrous tar. The highest function of the lining is to remain 

 unaffected, and allow the basic additions to do their work 

 alone, so that the rapid destruction of a basic, as compared 

 with an acid lining, is not due to any necessary part it plays 

 in the operation, but to the fact that there is no basic material 

 in nature which is plastic, and which by moderate heating will 

 give the firm bond that makes clay so valuable in acid practice.'* 



Acid and basic Bessemer steel is sometimes known as con- 

 verter steel, and depending largely upon the product of the 

 blast-furnace, as well as the possibility of large output, the cost 

 of production of Bessemer steels is considerably less than the 

 product of the open-hearth process, which finds it advantageous 

 to use a considerable proportion of scrap steel, and is more 

 limited in the matter of its output. It is claimed by many 

 authorities that the metallurgical conditions are such that a 

 greater degree of certainty in the production of open-hearth is 

 possible, and, whether this be true or not, the fact remains 

 that the general tendency among engineers and as evidenced 

 by numerous recent specifications, is to give a preference to 

 the open-hearth product over Bessemer steels. 



A description of the process of manufacture of the open- 

 hearth product is as follows, and is also from Mr. Campbell's 

 admirable work: 



Open- hearth Steel. " The open-hearth process consists of 

 melting pig iron, mixed with more or less wrought iron, steel, 

 or similar iron products, by exposure to the direct action of 



