Temperature of Iron and Steel during Recalescence. 191 



traction of a hardened steel rod by means of re-tempering. 

 They contain simultaneous longitudinal and temperature 

 measurements of hardened steel rods of Sandviken wire con- 

 taining 1*0 per cent, and 0'9 per cent, of carbon, which had 

 been repeatedly heated to different degrees of temperature, 

 and which were allowed to cool slowly after each heating. 



Table VIII. — Sandviken Wire, 0*9 per cent. C, hardened. 



Time of Heating. 



Final Temperature. 



Magnitude of 

 Contraction. 



6 sec. 



110 



000007 



12 „ 



200 



000134 



18 „ 



280 



000023 



24 „ 



395 



000082 



30 „ 



438 



0*00025 



36 „ 



498 



0-00005 



90 „ 



784 



0-00031 



i 



Table IX. — Sandviken Wire, 1*0 per cent. C, hardened. 



Time of Heating. 



Final Temperature. 



Magnitude of 

 Contraction. 



18 sec. 



333 



0-00186 



18 „ 



279 



o-ooooi 



18 „ 



284 



o-ooooi 



18 „ 



285 



0-000C3 



30 „ 



479 



0-00121 



30 „ 



446 



0-00004 



30 „ 



438 



o-ooooi 



90 „ 



782 



000037 



Tables VIII. and IX. show :— 



(xiv.) In heating a hardened steel rod to a temperature 

 between 150° and 450° and then allowing it to cool slowly it 

 undergoes a contraction corresponding to each final tempera- 

 ture*. In order that the rod shall contract still more, it is 



* M. Le Chatelier, Comptes Rendus, cvii. (1888), p. 862 writes :— " A 

 hardened steel rod, 0*1 metre long, contracts 0-285 millim. after having 

 "been heated to 350° and then allowed to cool slowly, and 0*545 millim. 

 after having been heated to 900° and allowed to cool. The different 

 values of the magnitude of the contraction thatM. Le Chatelier and myself 

 found may, doubtless, be explained by the difference in material used. 



P2 



