1919] The Hardening of Steel 4.^1 



AYEEKLY EVENING MEETING, 



Friday, March 7, 1919. 



Sir William Phipson Beale, Bart., K.C., Vice-President, 

 in the Chair. 



Professob. H. C. H. Carpenter, F.R.S. 



The Hardening of Steel. 



The capacity of steel for hardening by being quenched from a bright 

 red heat in water is the most important property possessed by any 

 metallic substance. This property is utilized practically in the arts 

 in a great variety of ways, and is the basis of all modern engineering 

 work. To take two types of application only— 



(1) It is utilized in the i^reat variety of tools which are employed 

 in modern engineering work, for machining metals and alloys to a 

 high degree of accuracy so that they may constitute a given part 

 of one of the thousand and one machines employed in the mechanic 

 arts of modern civilization, e.g. the locomotive, turbine, gas engine, 

 electric motor, etc. 



(2) The razor, the balance spring of the chronometer, the knife, 

 the needle, the pair of scissors, the surgeon's lancet and the dentist's 

 twist drill, are instances of the utilization of this property in the 

 finished steel as well, and they depend upon the capacity of such 

 material to retain its hardness in the absence of stress indefinitely at 

 the ordinary temperatures. 



Not only, however, is this property of the greatest practical 

 import, but of the highest scientific interest, inasmuch as the search 

 for the explanation of the capacity of steel for hardening has given 

 rise to a large number of scientific investigations, which have done 

 more than anything else to throw light on the constitution of steels 

 and metallic alloys generally, and have helped to establish the modern 

 science of metallography. 



My object this evening is to trace rapidly the history of some of 

 the salient features of this scientific work, and to bring to your notice 

 the most modern views as to the scientific explanation of this wonderful 

 property of steel. I must preface my remarks, however, with this 

 warning — that within the compass of an hour's lecture it is not 

 possible to attempt a complete exposition of the theories relating to 

 the great variety of steel alloys that are now used in the arts, and I 

 shall be obliged to confine my thesis to one of the simplest, albeit 



