SOME PHYSICAL PROPERTIES OF NICKEL STEEL. 155 



5. Present Series of Tests. — The authors considered that a more 

 useful and exact knowledge of the properties of nickel steel could 

 be obtained from a series of careful tests of material supplied by 

 steel manufacturers of acknowledged reputation, as so much 

 depends on the cautious treatment during the heating and forging, 

 more especially with the alloys containing from 3 to 8% of nickel 

 which are capable of being hardened. The following tests were 

 made from specimens selected by one of the authors during a 

 recent visit to the firm of Fried. Krupp of Essen, Germany. Three 

 kinds of steel were tested which are denoted in the test sheets as 

 follows : — 



F — Mild, containing approximately 3% nickel 



T — Medium hard, „ „ 8 „ 



E — Non-rusting ,, „ 25 „ 



The tests made by the authors were somewhat restricted in con- 

 sequence of the limited number of specimens available, but they 

 are sufficient to bring out clearly the physical properties of the 

 material. 



6. Tensile Tests. — These consisted in the first place in the deter- 

 mination of the elastic limit and coefficient of elasticity, the 

 extensions being measured by Marten's mirror extensometer. 1 The 

 test piece was afterwards divided between the reference points 

 into spaces of one-quarter of an inch, and connected to the auto- 

 graphic apparatus and tested to destruction. The yield point 

 recorded on the diagram is consequently higher than would have 

 been the case if the test piece had not been previously strained 

 in obtaining the true elastic limit. The results of these tests 

 are shown in Tables I. to V., and in the summary Tables X. 

 and XI. 



The results of testing specimens cut from a railway axle made 

 by Messrs. Vickers of Sheffield are also recorded, as showing the 

 results of testing good steel of the ordinary kind, for the sake of 

 comparing the results with those obtained from nickel steel. 



1 See Journ. Roy. Soc. Vol. xxxi., pp. 89-111. 



