194 REPORTS ON THE STATE OF SCIENCE.—1913. 
two or three repetitions of alternate small overstrain and boiling be 
further tested. 
(4) That the effect of cold working upon the ‘ natural’ elastic limits be 
further investigated. 
(5) It would appear that two desiderata, viz., resistance to repeated 
stress and resistance to large impact, require somewhat inconsistent 
qualities in the case of steel. (Nos. 83, 3, and 66.) Thus further work 
(though probably mainly metallurgical and micrographic) should be done 
in order to ascertain, if possible, the best conditions for maximum resist- 
ance when both kinds of straining action above mentioned operate, as in 
certain service conditions. A point to be tested is the resistance to sudden 
impact of steel which has undergone test by alternating stress of approxi- 
mately the Wohler safe range. 
(6) That an elaborate series of alternating stress endurance tests, all 
with the same material, be made on all the alternating stress testing 
machines in use ; at the very least twenty test pieces to be tested in each 
machine, and special precautions to be taken to ensure uniformity in the 
material.* 
Note on Heat Treatment. By Dr. F. Rogers. 
The effects of heat treatment upon the resistance of metals to alternat- 
ing stress form an almost entirely metallurgical aspect of the subject. 
The value of some published work is very doubtful, because of the 
vague use of such terms as ‘ annealing’ and ‘ quenching.’ In order that a 
heat treatment may be sufficiently specified the following particulars or 
others from which they may be derived should be given :— 
Composition of the steel, process of manufacture, its condition before 
the treatment in question (whether as rolled or forged, or heat-treated and 
how), the size of the piece, top temperature of the treatment, duration of 
heating at that temperature, rate and manner of cooling, whether in a 
furnace, in the air, or a liquid. 
A so-called annealing of a small piece may happen to be equivalent to 
the quenching of a large piece at some point in the large piece, except in 
so far as the result is affected by the previous treatment in each case. 
The present state of knowledge is such that the condition of the ma- 
terial can frequently be equally well, if not better, defined by the results of 
various familar mechanical tests, together with composition and micro- 
structure, as by a precise statement of the known portions of the heat 
treatment. On this account, when the effects of heat treatment on the 
endurance under alternating stress are being dealt with, it is desirable that 
as much collateral information about the material as possible should also 
be given. Largely on account of the more or less natural jealousy of 
manufacturers, little information of practical value has been published. 
It may be as well to confine present attention to carbon steels of carbon 
contents not exceeding what is usual in rails, say about 0-50 per cent. 
carbon, since practically no information on the remaining steels is to be 
found in the literature. 
The complexity of the subject has already been suggested. Further, 
however, it is necessary to remember that in any dynamic tests the relative 
* Suggested by Mr. E. M. Eden. 
oO EEE 
