Page:The American Cyclopædia (1879) Volume XV.djvu/372

 360 STEEL in number, are made of fine clay in the form of truncated cones, each perforated with 7 to 12 holes about three eighths of an inch in di- ameter. They are arranged on the bottom plate, and ganister or other material stamped around them ; and the finished bot- tom, after drying, is inserted in the I converter. The bottom ' lasts gen- ' erally for 6 to 10 heats, while a care- fully made lining may endure 1,000 or more heats. The converter is mounted on trun- nions, one of which is hollow and con- veys the blast to the tuyere box below the tuyeres, and to the other is attached the mech- anism by which the converter is revolved. Figs. 1 and 2 give sectional views of the con- verter in two positions. Fig. 3 is a plan of the converter with the rotating machinery. The ladle into which the steel is poured from the converter is shown in figs. 4, 5, and 6. Fig. 4 is a vertical section of the ladle crane and elevation of the ladle. Fig. 5 shows the platform on which the ladle moves, and fig. 6 is a partial section through the ladle, show- ing the loam-coated rod which acts as a stop- FIG. 2. per in pouring. By this lattsr arranga- ment the fluid steel is discharged in a thick stream, and the cinder remains on top. The steel is usually cast in long in- gots about 12 to 14 in. square at the base and tapering from 1 to 1 in., each in- got being rolled into two or three rail blooms. When the steel is intended for other purposes than rails, moulds of spe- cial forms are used. To obviate the occur- rence of air bubbles in the steel, caused by the falling of the stream from the top to the bottom of the mould and spatter- ing against the sides, bottom casting is employed ; that is, pouring the steel down a central sprue and causing it to enter the bottom of several moulds at a time through fire-clay distributors. The blow- ing engine for supplying the blast is usu- ally double, and should be able to deliver 8,000 to 11,000 cubic feet of air a minute nt a pressure of 25 Ibs. to the square inch. Probably no other invention of the magnitude of the Bessemer process ever came from the hands of its inventor in as complete a form. But while the accumula- ted experience of 15 years has added nothing to the essential features of the apparatus and machinery, yet in the minor details of construction improvements have been made which have increased the capacity of the process four fold. The highest perfection of ap- paratus and working has been attained in the United States, where there are now (1876) ten works with two FIG. 4. converters each, of five to six tons capacity. The improvements in American practice have been largely due to Mr. A. L. Holley, who has superintended the construction of most of the works in this country. In 1868 an output of 500 tons a month from two five-ton con- verters was barely reached. The pro- duction Jiad gradual- ly increased to 4,200 tons of ingots a month in the best works, in others to 3,800 tons, and in one instance to 5,000 tons. In the nominally five-ton vessels 5 to 5| tons are sometimes pro- duced at a heat. The improvements which have rendered this large and regular pro- duction possible in this country, far ex- ceeding that of Eu- ropean works, have been summed up by Mr. Holley as follows : 1, improved cupola furnaces and method of working ; 2, the means used for quick- ly and soundly renewing the vessel bottoms, and the use of fire brick around the tuyeres ; FIG. 8.