METALLURGICAL STUDY OF CAST IRON FOR GLASS MOLDS*

Research data are reported on the susceptibility of cast iron to cracking when it is used in molds for processing glassware. An accelerated test was run to produce cracking in a shorter time than would occur in the production of glassware. The results from this test indicate that sand-cast iron is more resistant to cracking than chill-cast iron of the same composition. The alloyed chill-cast irons, however, cracked less severely than the unalloyed iron. An annealing heat-treatment of these irons increased resistance to cracking, whereas a spheroidizing heat-treatment reduced resistance. A maximum resistance to cracking together with the ability of the iron to take a high polish apparently may be obtained by using an annealed, chill-cast alloy iron containing chromium, nickel, and molybdenum. Such iron is more susceptible to cracking than a sand-cast iron of the same composition, but the latter type is incapable of a sufficiently high polish and usually has an open, porous structure.