| When one thinks of charcoal, we normally think of | | | | ward off the strongly carburizing tendency of the |
| the most important historical use of wood | | | | charcoal. |
| charcoal; as the main ingredient in gunpowder. | | | | Only a good quality of pig iron (nearly always |
| However, it was of major importance in | | | | charcoal pig) is used, as the process is expensive, |
| metallurgical operations as a reducing agent, | | | | and is employed only for a high grade of wrought |
| primarily in the manufacture of steel. The most | | | | iron. The pig iron is often given a preliminary |
| common use in the modern era for charcoal is as | | | | refining to eliminate most of the silicon. The |
| a fuel source, but still has industrial application. The | | | | hearths are usually built of unlined cast-iron plates, |
| Charcoal Hearth Process was vitally important in | | | | at least in part water-cooled. Brick-work is |
| the early industrial steel age. | | | | avoided as the silica would enter the slag. The |
| Charcoal Hearth Processes were sometimes, but | | | | processes may be classified according to the |
| rarely, called forge processes, and bustling and | | | | number of times the metal is melted down |
| buzzing are very obsolete terms. These | | | | before the tuyere, into single melting, double |
| processes are designed for the production of | | | | melting, and triple melting (or German or breaking |
| wrought iron (charcoal iron), usually by refining | | | | up); into Walloon and non-Walloon. |
| cast iron, occasionally by melting scrap before a | | | | The hearth may be covered or uncovered; if the |
| tuyere with charcoal for fuel, the product being | | | | latter it is called an open fire or open hearth; if the |
| obtained in a pasty condition, and containing a | | | | former, a closes hearth. The bloom, after rolling, is |
| certain amount of slag, but less than puddled iron. | | | | called finer's bar (cor- responding to muck bar in |
| Only the latter method survived the early 20th | | | | puddling), and after piling and rerolling, finished |
| century in this country. | | | | charcoal bar. German general steel ( is an obsolete |
| In general the furnaces or hearths are like the | | | | name for the product obtained by melting white |
| Catalan and bloomary hearths for reducing iron | | | | or refined pig in a charcoal hearth; it may also be |
| from the ore, low, rectangular chambers, | | | | made of poorer quality. In the Bohemian process, |
| sometimes roofed, and with one or more | | | | mottled or even gray pig is used, and the blooms |
| tuyeres. The chief difference is that in refining | | | | are reheated in the same hearth. Charcoal is first |
| cast iron much more strongly oxidizing conditions | | | | charged, and on top of this some slag and the pig |
| are brought about, chiefly by melting the metal | | | | which is melted down slowly, the iron cake which |
| down in drops before the tuyere, repeatedly, if | | | | is formed being frequently raised up. The cinder is |
| need be, so that it passes in a state of minute | | | | tapped at intervals. Finally the bloom is welded to |
| subdivision and with great surface exposure | | | | the end of a rod and taken to the hammer; any |
| through a part of the hearth where the | | | | particles of iron that remain in the hearth are |
| atmospheric oxygen is in excess; and by the | | | | retreated. |
| action of the basic ferruginous slag with which the | | | | The use of charcoal in steel making rapidly |
| metal is mixed during the earlier stages, and with | | | | diminished with the introduction of coke, anthracite |
| which it is covered during the later stages, to | | | | smalls, etc. for industrial processes. |