time as the other additions. This was done to assure complete melting of these higher melting point additives. For this cartridge brass standard, it can be seen that a total of 1 min 25 sec time had elapsed from pulling the stoppers in the pouring basin to complete solidification for the 600 lb disk 27 in. in diameter and 4 in. thick. The total time varied from about 40 sec to 2 min for the various melts and was dependent primarily on the alloy, but also to a lesser degree on the particular composition for a given alloy. Figure 1 shows the tapping of the molten metal from the furnace into the ladle. This was done approximately 100°F above the liquidus temperature for each melt. Once in the ladle, the molten metal was skimmed to remove the last of the charcoal cover and the dross. Figure 2 shows the pouring of test samples into separate ceramic molds on the water-cooled copper plate prior to pouring the main heat. In the background is seen the mold assembly into which the molten metal is poured. Note the stoppered pouring basin at the top. Once the molten metal has been poured into the basin, the plugs are pulled simultaneously. Figure 2. Pouring of test samples prior to pouring the molten metal into the stoppered pouring basin. Solidification is unidirectional, from the bottom up, with little freezing occurring from the periphery inward, or from the top downward. Figure 3 shows a view of the solidified casting. Note the use of the interlocking cast iron blocks to retain the circular disk casting. Figure 3. Solidified casting on the water-cooled copper plate after removal of pouring basin. Once a casting had been prepared, preliminary analyses were obtained on the separately cast test samples both at NBS At NBS, both chemical** and spectro and by a cooperator*. chemical determinations were made and a complete analysis for each heat was obtained before preparing a subsequent heat. In general, it was relatively easy to prepare the copper-base castings close to the aim or the desired composition. Before processing a casting into standard samples, extensive homogeneity testing was performed and figure 4 shows the selection of samples that were chosen for this testing. Metallographic studies, optical and x-ray analyses, and chemical analyses were made at NBS. In addition, a large amount of testing was performed by members of the cooperating Task Group 3, Subcommittee V of ASTM Committee E-2***. These studies provided information on the composition and structure differences from outside to center and from bottom to top of the casting. * F. V. Schatz, Revere Copper and Brass, Inc., Rome, N. Y. R. K. Bell, Quantitative Separations Section (formerly Standard Reference Materials Section). ** *** Task Group 3 cooperators: Bridgeport Brass Co., Bridgeport, Conn., A. W. Young Olin Mathieson Chemical Corp., New Haven, Conn., R. G. Russell F. V. Schatz (Chairman) Y., The Anaconda American Brass Co., Waterbury, Conn., J. P. Irwin Titan Metal Mfg. Co., Bellefonte, Pa., W. M. Rumberger |