14 
MR. J. MUIR ON THE TEMPERING OF IRON 
The Tempering of Steel from the Condition as supplied. 
It was found that the change in elastic properties shown by a comj)arison of 
Diagrams 1 and 2 to be produced by annealing, could be brought about gradually 
by heating the material to temperatures lower than that which is commonly known 
as an annealing temperature. Any temperature exceeding 600° C. was found 
sufficient to produce a distinct lowering of the primary yield-point and a reduction 
of the step by which the yield-point is raised in consequence of recovery from over¬ 
strain. Diagram No. 3 illustrates this gradual tempering of the material from the 
condition as supplied by the makers, that is, from the condition of high yield-point 
and large step. 
Six sjDecimens were employed to obtain the curves shown in Diagram 3, and these 
Diagram No. 3. (Tempering of Steel from the condition as supplied.) 
Scale :—/ Unit = 
Curves A—Material as supplied. 
„ B—After heating to 600° C. 
C- „ „ „ 650°C. 
of an iticlt. ^-i-5 
Curves D—After heating to 700° C. 
„ E- „ „ 730° C. 
„ F_ „ „ .. 7S0-O. 
5 ) 
5 ? 
