504 METALLURGY OF CAST IRON.
of chill used with the test bars shown, and is three-eighths inch thick by three inches long, and made of soft steel. Only one side or half of the test bar is here considered in measuring a chill for record. For iron above 1.25 per cent, silicon and no higher than 0.03 per cent, in sulphur, this system of obtaining chill-records indicated in Fig. 121, will work very satis-factorily. For iron lower in silicon or higher in sul-phur, it may be often necessary to have a larger body of iron, in order to prevent a specimen being chilled all the way through. In such cases, chill-blocks, as shown in Figs. 114, 115, and 116, maybe required to obtain chill records. Where best value is to be attrib-uted to the chill records, the fluidity should be noted to be the same by eye or by the means shown in Fig. 121.
Fig. 116 shows a longitudinal section through the chill pig-mould of Fig. 114. The well at B is provided to prevent cutting the chill in pouring, and to cause the bar to pull towards one end in contracting, so as to permit the contraction to be readily measured by means of the tapering rule, shown at D. This test specimen, being twelve inches long, provides a convenient length for measuring the contraction, and can also be readily broken to note its fracture, or can be drilled to obtain samples for analysis.
The sections in Fig. 115 show that the bottom surface of the chill-mould is round, possessing no corners to cause any one part of the specimen to be. chilled deeper than another, thereby causing internal strains and preventing natural contraction of the iron, owing to one part of the specimen being thrown into higher combined carbon than another. This consideration, the author believes, will cause any one making ad which is a forma warm ladle to receive the liquid iron. The lining used for the cupola is simply a coating ofnovice desires to use the smallest cupola practical for melting small samples. "............ " " i in square hnrH........................