Trial-cast
A simple and inexpensive method of obtaining a trial-cast of pig iron is to possess a gas-blast or other good crucible furnace in which to melt a small sample at quick notice, and cast a bar one inch square, twelve inches long, and another two inches wide, one-eighth inch thick, also twelve inches long. These must be moulded carefully, by the same person every time if possible, in separate flasks, and poured with metal corresponding in temperature on each occasion. If a wedge-like projection two inches long be cast on one or both ends of the square bar, the tendency to chill will be at once determined by the amount of white iron extending from the point inwards, as well as by the edges of the thin bar. The amount of shrinkage is ascertained by careful measurement of the bars; and, if the same gates be used for each cast, the thin bar will serve to show the metal's fluidity. Tensile or transverse strength can be afterwards obtained on the testing-machine. See TESTING-MACHINE; STEEL CASTINGS; GAS-BLAST FURNACE.