178 ANNUAL OF SCIENTIFIC DISCOVERT. 



CHEMISTRY OF STEEL. 



M. Caron, in a communication made to the French Academy of 

 Sciences, attributes the combination of iron with carbon or other ele- 

 ments of the same family, by which tempered steel is formed, to the 

 sudden shrinking of the mass, which he considers as analogous to the 

 instantaneous compression produced by hammering. In illustration of 

 this point, he found that by hammering a bar of iron heated to a 

 bright redness, on an anvil covered with powdered charcoal, the face 

 of the bar in contact with the charcoal, was, in spots, converted into 

 steel, and made capable of resisting the file. His researches also con- 

 firm the results of previous experiments, that the density of steel is de- 

 creased by tempering. In one specimen, after thirty successive tem- 

 perings, the density was reduced from 7.817 to 7.743. 



BESSEMER'S PROCESS FOR THE PRODUCTION OF IRON AND STEEL. 



This method of converting pig-iron into steel and bar-iron (described 

 in former numbers of the Annual Sci. Dis)., is constantly increasing in 

 favor among European ironmasters, and thousands of hundred-weight 

 of Bessemer steel and iron are now annually produced in England and 

 Sweden and it has become an article of commerce ; while large works 

 are also being erected for the employment of the method in France. 

 Whenever the proper raw material is used, Bessemer's process gives 

 steel, which in all respects is fully equal to the best varieties of cast- 

 steel ; and iron of as good quality as the best forge iron. The loss in 

 converting pig-iron into steel, by this method, is twelve to fifteen per 

 cent., and in making bar-iron eighteen to twenty-two per cent. In five 

 to ten minutes, fifteen to twenty cwt. of fluid pig-iron are converted into 

 steel or bar-iron with scarcely any cost for fuel, and without hand la- 

 bor. The pressure of blast used is from one-half to one one-half atmos- 

 pheres, and the amount is 800 to 1200 cubic feet of cold air of the or- 

 dinary atmospheric density. Only good charcoal-iron is adapted for 

 conversion by this method, and the reason of the failure of the earlier 

 experiments was the employment of improper and inferior raw-materi- 

 al. Swedish pig-iron is now always used in England for the produc- 

 tion of the best sorts of steel and iron. In some of the new iron works, 

 attempts have been made to improve the quality of English pig-iron 

 which has been carried to the point of conversion by adding to it melt- 

 ed Swedish pig-iron ; manganese compounds have also been used for 

 the same purpose. But the separation of the deleterious substances as- 

 sociated with carbon in pig-iron still remains an unsolved problem. For 

 the success of this method, a good quality of pig-iron is therefore indis- 

 pensable, and further a high temperature ; this last is attained by con- 

 verting large quantities of iron in a single operation. In Sweden, fif- 

 teen cwt. for a charge is the minimum quantity used, and if sixty to 

 one-hundred cwt. be employed, the result would be still more favorable. 

 In converting large quantities at one operation, the cost is proportion- 

 ally diminished, and the product may also be made more uniform. 



One great advantage of Bessemer's process is that so much larger 

 quantities of material can be operated upon at one charge than in the 

 oi'dinary methods of refining, and this quantity is not restricted within 

 narrow limits, as in puddling and hearth refining. For the production 



