210 
STEEL, AND THE BESSEMER PROCESS* 
BY A. L. HOLLEY. 
Although the general composition and nature of steel are well under- 
stood, it may not be inappropriate to refer briefly to these subjects, as 
preliminary to a consideration of the Bessemer process and its results. 
It is well known that cast-iron is substantially iron with five per 
cent, of carbon and one or two per cent, of silex and some other 
impurities. Steel is iron with one to one -tenth per cent, of carbon and 
a trace of silicium, and traces of some other substances. Wrought-iron 
is substantialy iron — iron from which all but a trace of carbon has been 
eliminated. These are the three commercial forms of iron. Steel is 
subdivided, first, according to its quality, that is to say, substantially 
according to the high or low degree of its carbonisation ; second, 
according to its method of manufacture. 
First, as to carbonisation. High steel, or hard steel, is that wjjrich 
contains a large amount of carbon and a low specific gravity. Its dis- 
tinguishing properties are extreme ultimate tenacity, hardness, and 
capability of extension, without permanent change of figure ; but its 
extensibility beyond the elastic limit is small, and it is therefore brittle 
under concussion. It will harden when heated and immersed in water ; 
it is with difficulty welded, because it deteriorates under high heat and 
because its welding heat is very near the melting point, and it is melted 
at a low temperature as compared with wrought iron on account of its 
excess of carbon. 
Low steel, also called mild steel, soft steel, homogeneous metal, and 
homogeneous iron, contains less carbon and has a higher specific gravity. 
It can be welded without difficulty, although it deteriorates by over- 
heating, and it more nearly resembles wrought iron in all its properties, 
although it has much greater hardness and ultimate tenacity, and a 
somewhat lower range of ductility, depending on its proportion of 
carbon. It has less extensibility within the elastic limit than high steel, 
but greater extensibility beyond it ; that is to say, greater ductility. 
The grand advantage of low steel over wrought iron, for nearly all 
purposes, is that it can be made liquid at a practicable heat, and run 
into solid, homogeneous masses, however large ; thus avoiding the great 
defect of wrought iron — want of soundness due chiefly to welds. It is 
also harder, more elastic, and more tenacious. 
Second, Steel is named according to the processes by which it is 
manufactured. 
"What is called " puddled steel " or, by some of its makers " semi- 
steel," ought not to be called steel at all. The idea of steel involves the 
idea of casting from a liquid state, and of consequent homogeneity. 
* A paper read "before the Polytechnic Association of the American Institute, 
New York, Oct. 12, 1865. 
