Transactions . A3 is only to indicate that this part of the curve rep-resents both heating up and cooling dawn, and not to suggest that the grain size changes,when rising temperature gives place to falling. Let the reader make abstraction of thisdoubling, and mentally superpose the unbroken on the broken line. 586 GRAIN GROWTH IN SILICON STEEL. occurs, hence I call it the congenital coarsening of non-gamma ironcrystals. The refining of this impure iron on rising above Ac3 is not sur-prising, meaning either that the crystals of gamma iron do not inheritthe size of the non-gamma iron whence they
Transactions . A3 is only to indicate that this part of the curve rep-resents both heating up and cooling dawn, and not to suggest that the grain size changes,when rising temperature gives place to falling. Let the reader make abstraction of thisdoubling, and mentally superpose the unbroken on the broken line. 586 GRAIN GROWTH IN SILICON STEEL. occurs, hence I call it the congenital coarsening of non-gamma ironcrystals. The refining of this impure iron on rising above Ac3 is not sur-prising, meaning either that the crystals of gamma iron do not inheritthe size of the non-gamma iron whence they spring, or that the crys-tals of the non-gamma iron born on again cooling past Ar3 do as Goerens9 has shown that the effects of overstrain are removedchiefly between 500° and 520°, and as therefore this should be the-temperature of dis-amorphizing, more precise experiments are needed 1200°1 Commercial. Low-Carbon Metal *- 020° Ac3 900-o ul £ 6C0- cr u (- 300 It \ GRAIN SIZE ElectrolyticIron. GRAIN SIZE Rising T°_ Falling T° Fig. 15. Fig. 16. Figs. 15 and 16.—Behavior of Very Low-Carbon Metal. The commercial coarsens on dis-amorphizing and refines at Ac3, the electrolytic coarsens at Ar3. to show whether this coarsening will occur there. Ir was actuallyobserved by Professor Sauveur at 650°, though Stead 10 reported thatit occurs between 500° and 770°. Turning to the pure electrolytic iron, Fig. 16, its coarsening occursvery abruptly in the change at Ar3 from gamma to non-gamma iron,so that this too is congenital coarsening of non-gamma iron. 9 Iron and Steel Institute, Carnegie Memoirs, vol. iii, p. 383, Fig. 42 (1911). 10 The Crystalline Structure of Iron and Steel ; Journal of the Iron and Steel Institute,vol. liii (No. I, 1898), pp. 145 to 189. Brittleness Produced in Soft Steel by Annealing ;idem, vol. liv (No. II, 1898), pp. 137 to 154. POSITION OF AE3 IN CARBON-IRON ALLOYS. 587 Determination of the Position of Ae3 in Carbon-Iron Alloys.* BY H. M.
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