8 
MR. J. MUIR ON THE TEMPERING OF IRON 
recovery from overstrain was decidedly reduced. Diagram No. 2 gives the history 
of a specimen of this steel, which was first of all annealed by heating for a few 
minutes to about 750° C. with a slow cooling, and was then subjected to series of 
operations exactly similar to that described for Diagram No. 1. 
A comparison of Diagrams No. 1 and No. 2, or an examination of the following 
tables of extensometer readings, clearly shows the effect produced on the elastic 
properties of the material by the process of annealing. Only a few of the readings 
taken to obtain the various curves of the two diagrams will be tabulated for the 
sake of comparison; and it should be mentioned that the curves were in many 
cases obtained from second loadings of the material at the varies stages of the 
experiments. 
Readings for Diagram No. 1. (Steel as supplied.) 
Load in 
tons/sq. 
inch. 
Extensometer readings. (Unit = of an inch.) 
Curve 1. 
Cm-ve 2, 
zero time. 
Curve 3, 
If days. 
Curve 4, 
2 weeks. 
Curve 5, 
200° C. 
Curve 6, 
200° C. 
0 
0 
0 
0 
0 
0 
0 
8 
240 
262 
260 
260 
242 
246 
16 
484 
548 
533 
519 
490 
494 
24 
734 
856 
832 
789 
738 
746 
32 
986 
1192 
1154 
1061 
990 
1004 
36 
1112 
1396 
— 
— 
— 
— 
38 
Yield-point 
1540 
1426 
1281 
— 
— 
40 
— 
— 
— 
1248 
1256 
44 
— 
— 
— 
— 
1374 
1386 
48 
— 
— 
■- 
1506 
1513 
49 
— 
— 
— 
— 
Yield-point 
52 
— 
— 
— 
— 
— 
1638 
56 
— 
. - 
— 
— 
— 
1758 
60 
— 
— 
— 
— 
— 
1884 
60i 
— 
— 
— 
— 
— 
Fracture 
Curves 5 and 6 relate to tests made after exposing the material to a temperature of 200° C. for a few- 
minutes. 
