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53°                      MJ£TA1
duplicates similarly as cited above for car wheels, etc., the only difference being that these single castings are not cast in large numbers and may have months intervening between their production, so that in a practical sense castings can, when they are occasionally duplicated, have the test bar records accepted to denote their physical qualities in a comparative manner, as where any number of castings are steadily or daily made from the same pattern.
The utility oi the test bar is being more and more recognized arid made use of. The author believes that within ten years almost all founders and engineers will recognize standards for physical tests.* How are we going to be able to make intelligent comparisons with our own records or those of others, where we find bars as small as one-half inch square to two inches square being used, and some of rectangular form and again, it can be said, in all kinds of lengths, from a foot up to four feet long, so that we practically find hardly two founders using the same form or length of a bar, or builders and engineers exacting the same character of tests? Some will say that the difference in both the length and area of such a variety of bars could be computed to strength per square inch, in making comparisons. It can be shown (see Chapter LXL, page 476) that there is about as much difference to be found in formulas for computing such variations as is found above in test bars, and also that so eminent and able an authority as Prof. C. H.
*Many consider that the distribution of the first two editions of this work, in connection with the author's advocacy of round bars cast on end in trade papers, is largely responsible for the conditions leading tip to the recommendation by the American Foundrymen's Association of the proposed standards seen in the next chapter., if they have not drawn              '1