Cast brass 23,000 Annealed brass wire 49,000 Cast copper 24,000 Annealed copper wire 32,000 Gun bronze of copper and tin cast 39,000 Average American cast iron 16,000 Good wrought iron 50,000 Best American wrought iron (exceptional) 76,100 Iron wire ropes 38,000 Malleable iron castings 48,000 Steel plates (rolled) 81,000 Cast steel average Bessemer ingots 63,000 +----------------------------------------------------------------------+ | ALUMINUM BRONZE. | +---------+------+-----------------------+----------------------+------+ |Per cent.| | Tensile strength per | |Ingots| | of |Grade.| square inch. | Elongation. | per | |aluminum.| | | |pound.| +---------+------+-----------------------+----------------------+------+ | | A 1 | 90,000 lbs. and over. | 0 to 5 per cent. |$0.45 | | | A 2 | 75,000 to 90,000 lbs. |10 per cent. and over.| .40 | | 10 | A 3 | 65,000 to 75,000 lbs. |25 ” ” | .37 | | 7½ | B | 47,500 to 65,000 lbs. |20 ” ” | .33 | | 5 | C | 35,000 to 47,500 lbs. |25 ” ” | .26 | | 2½ | D | 27,500 to 35,000 lbs. |30 ” ” | .20 | | 1½ | E | 20,000 to 27,500 lbs. |15 ” ” | .16 | +---------+------+-----------------------+----------------------+------+ The specific gravity of the A grade is 7.56, that of steel being 7.88. Its coefficient of expansion is small at ordinary temperatures; its electrical conductivity is about 9, and with the lower grades the expansion by heat, specific gravity and heat and electrical conductivity increases the nearer the metal approaches to pure copper. With more than eleven per cent. of aluminum the bronze rapidly becomes brittle. In color, aluminum bronze of the C and D grades is the nearest to gold of any known metal, the higher grades being lighter in hue than the lower. The A grade melts at about 1700° F., a little higher than ordinary bronze or brass. Aluminum bronze shrinks about twice as much as brass.