Metallurgy Of Cast Iron

SPECIFIC GRAVITY OF VERTICAL-POURED CASTINGS. 379
Table 84 presents a series of tests on the specific gravity of vertical-poured gun casting's.
TABLE 84.—TKSTS OK SPECIFIC GRAVITY OF FIRST AND LAST SIX MORTAR CASTINGS.
Number of Heat. Specific gravity of muzzle or top end of gun. Specific gravity of breech or bottom, end of gun.
78 ............................... 7 2^8 7 2478
79 ..................................................... 7.2430
So ........................... .............. 7 256 7.269
87 7 2934 7 2882
88.::.::::;:::::::::::::::::::7:'":::::""::'::::::: 7 278 7.285
8q ..... .... .......... 7 335 7 329
185,:::: ..... ::;:::::;..:::::::::::::.::::.:.::::::: 7.3263 7.3182
1 86 ........... . ....... 7 3325 7.3252
187 .............................. 7.3404 7-345
188. . ......... 7 3636 7.3336
189 .................................................... 7.349 7.340
190 ...... .... 7 3345 7.3267

Total ........................... 87.6903 87 6524
Average ....................................... 7.3075 7.3043

The lower test disc was taken about 11 feet from the top of the casting and the upper test 2^/2, feet from its upper end. The majority of the tests showed the specific gravity of the muzzle specimens to be higher than the breech specimens and also to be harder and of higher tensile strength. This is the reverse of what many would expect. Table 84 shows the average specific gravity of all the casts made for specific gravity of breech and muzzle specimens on the first six mortar castings and on the last six mortar castings made by the Builders' Iron Foundry, from whom the author received these tests, and wishes here to tender his thanks for the kindness rendered.
The tests and figures in Tables 83 and 84 indicate that there is no condition which will cause any practical difference in the lower and upper end of longbsorbed — up to the limit of the iron'sding its mate.. 2111 3Os i m. mi 3os 3OS. 3111. im ^os Jill l^S i in.