Journal of the Franklin Institute of the State of Pennsylvania and Mechanics' Register, Vol. 20: Devoted to Mechanical and Physical Science, Civil ... and Other Patented Inventions: July De
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Publisher: Forgotten Books (6 Nov. 2016)
By: Pennsylvania Franklin Institute (Author)
It will be seen that if we take into view all the bars of this iron, on which experiments were made after they were reduced to a uniform size, and ex olude only 219 B., on which the sections were all deeply filed, the advantage will appear to be in favour Of the metal manufactured from white pig next to which, is that produced from lively gray, giving 98% per cent. Of the strength of the first. Next, in the order of strength, will be found the iron from dead gray pig, inferior to the first by 1 2-3 per cent.: next, that from the mixture of the four kinds of pig which appears to have been weaker than the same by 4 4-10 per cent.: and, finally that from mottled pig in which the inferiority extended to 5 per cent. The following table (lxxix.) exhibits, at a view, the comparative strength, and the respective degrees of uniformity of the several bars, with the strength of some of them at high temperatures.
At elevated temperatures, the results, except that on No. 219 B, are much nearer to each other, than those at the points selected for our general com parison. On that bar, the trials were upon filed sections. The experiment at giving a strength of 66620, exceeded those at corresponding tempera tures on the other bars, by an average of about 6222 lbs., or 10% per cent.: while the two experiments which were made upon it at low temperatures, as will be seen by table LXXXII., gave results, the mean of which being 66724 lbs., surpasses that of the other nine bars by 9275 lbs., or by 16 1-10 per cent. Hence we are compelled to believe that this specimen, as it came to hand, had undergone the process of hammer-hardening, - a process which the direct experiments of the committee have proved to be capable of essen ially modifying the tenacity of the metal.
From the above, it appears, that the greatest difference of strength which under ordinary circumstances, can be attributed to differences in the pig metal from which wrought iron is produced, is about 5 per cent., and that under every mode of trial, the article formed from a mixture of different kinds of pig, is inferior in tenacity and uniformity to those derived from either of the ingredients, unless we except that from mottled gray. And even this latter will, on a comparison of all the experiments made upon it, under every circumstance, be found superior to the bars from mixed castings.
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