HARDENED BY OVERSTRAIN. 
9 
Readings for Diagram No. 2. (Annealed Steel.) 
i 
Extensometer readings. (Unit = inch.) 
Load ill 
tons/sq, 
inch. 
Curve 1. 
Curve 2, 
zero time. 
Curve 3, 
If days. 
Ciu’ve 4, 
2 weeks. 
Curve 5, 
300° C. 
Curve 6, 
300° C. 
Curve 7, 
300° C. 
Curve 8, 
300° C. 
0 
0 
0 
0 
0 
0 
0 
0 
0 
4 
122 
— 
— 
— 
120 
120 
122 
120 
8 
248 
254 
258 
251 
241 
241 
249 
241 
16 
498 
532 
528 
510 
491 
491 
498 
490 
24 
751 
838 
820 
770 
746 
742 
751 
' 740 
29 
932 and 
1060 
1022 
935 
32 
yield-point 
1010 
992 
1010 
991 
36 
— 
— 
t— 
— 
1146 
1122 
1140 
361 
— 
— 
— 
— 
1250 and 
40 
yield-point 
1256 
1264 
1242 
44 
— 
— 
-- 
— 
— 
1387 
1391 
44J 
— 
— 
-- 
— 
— 
1406 and 
48 
_ 
yield-point 
1520 
1499 
50 
— 
— 
_ 
— 
— 
1581 
52 
— 
— 
— 
— 
— 
— 
1661 and 
1627 
56 
yield-point 
1756 
58 
— 
— 
— 
— 
— 
___ 
1828 
59 
— 
— 
— 
— 
— 
— 
-- 
1880 
591 
— 
— 
— 
— 
_ 
— 
Fracture 
Curve No. 1 of Diagram 2 shows that annealing has had the effect of lowering the 
yield-point of the material by about 9 tons per stp inch. With the virgin material 
the primary yield-point occurred at about 38 tons per .sq. ijich, with the annealed 
material at 29 tons per sq. inch. The stretching which occurred at the yield-point 
was also less in the case of the annealed material, the permanent extensions in the 
two cases being respectively 0T3 and 0‘08 of an inch on the 4-inch lengths. 
A comparison of Curves 2, 3, and 4 of Diagram No. 1, with Curves 2, 3, and 4 
of Diagram No. 2, shows that immediately after overstrain annealed material 
exhibits rather less hysteresis than the same metal not previously annealed ; and 
that recovery from the semi-plastic condition induced by overstrain takes place rather 
more rapidly in the case of the material which has been first of all annealed. 
Curve No. 5 and the remaining three curves of Diagram No. 2 show that with an 
annealed specimen the step by which the yield-point is raised in consequence of 
tensile overstrain and recovery from overstrain is about tons per sq. inch, and 
that four such steps can be obtained before fracture occurs at about 59|- tons per 
sq. inch. With the material in the condition as supplied, fr-acture occurred at 
GOi- tons per sq. inch after two steps of about 11 tons. 
VOL. CXCVIII.—A. c 
