This process converts pig iron into steel by blowing cold air through the molten metal to burn out the carbon. After the carbon is removed (and incidentally some other impurities are removed), and the air blast stopped, enough carbon is re-introduced into the charge to give the steel the amount required.

This operation is carried on in a large vessel called a converter, a view of which, partly in cross section, is shown in Fig. 24. The shell of the converter, marked D, is built of steel plates in three sections, held together by brackets E. To the bottom is bolted two castings J and K which form a hollow receptacle called the blast box or wind box. Two other plates may be seen in the bottom, the upper serving to strengthen the bottom, and the lower, marked L, serving to hold the tuyeres M in place. The shell is lined for the acid process with ganister, and for the basic process (not used in

America) with magnesite, chromite or dolomite. The lining is marked C.

The vessel is supported by an encircling band G, which carries two trunnions BB, by means of which it can be tilted when necessary. One trunnion is solid, and carries a large-toothed wheel A to which is geared the rotating mechanism. The other trunnion is hollow to afford a means of conveying air to the blast box K, through the pipe H. The small sketch M at the side shows one of the tuyeres, made of refractory material, which conveys air from the box to the interior of the converter.

Fig. 24. - Bessemer Converter.