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Full text of "Metallurgy Of Cast Iron"

CONTRACTION VS. STRENGTH OF CAST IRON.    457
square bars cast flat, also the one and one-eighth inch round bar cast flat and on end, was dueto the body of the test bars being- sufficiently massive to overcome any tendency which variations in the fluidity of metal or dampness of the sand could exert in causing a difference in the combined carbon. With large-sized test bars, properly cast, having no corners to be affected by the " temper " of sands and fluidity of metal, contrary to the conditions seen in a square or small test bur, we are justified in placing the utmost confidence in the record which they may present. And were it not that in accepting castings there is generally a large margin permitting the founder to often greatly disregard obtaining the best possible physical properties of the iron in his castings, the error of using bars as small as one-half inch square or below one square inch area would have been clearly demonstrated long before this. (See pages 454, 467, 484, 511 and 573.)ous to these tests, I also made some in our foundry in the presence of E. Duqne Estrada, M. E., of Pittsburg, a member of the American Society of Mechanical Engineers' Testing Committee, to learn whether degrees in fluidity of iron would affect the contraction of large-sized test bars or thick castings. To test this point, two bars two inches square and forty-eight inches long were moulded together in the same mould. One was poured with the metal as '' hot'' as could be obtained from the cupola, and the other with the same ladle cooled down to pour the metal as '' dull'' as possible and still obtain a full-run bar. Two sets of these experiments were made, but no difference was found in their contraction. The fact of there being no visible difference in the contraction of the two-inchameter and made  a dry sand  mould, using" a piece              \