716. PROCEEDINGS OF SECTION H. 
and steam hammers, and hydraulic press cylinders. For 
such purposes nickel steel is much superior to carbon steel, 
and the good results obtained more than compensate for the 
increased price of the material. Straight and crank axles 
of nickel steel have been used to a considerable extent on 
the railways in Europe with most satisfactory results, which 
might reasonably have been anticipated from the results of 
the physical tests, viz., high elastic limit, resistance to 
repeated stresses in the alternating bending tests, ductility, 
and strength. It is generally considered that all large 
forgings should be forged with the hydraulic press in prefer- 
ence to the steam hammer, and whenever practicable a hole 
should be bored through the axis of the shaft to remove any 
possible defects and give lightness. The removal of material 
along the axis is also desirable, since its position in regard 
to the radius of gyration renders it least effective. Again, 
it is an advantage to compress the ingot while it is in a fluid 
state, after the method introduced by Sir J. Whitworth. 
To obtain the best possible results, forgings should be 
tempered in oil in preference to annealing them. 
Annealing and Treatment during // eating and Forging ; 
W elding.—The effect of annealing is to slightly reduce the 
tensile strength and tenacity in nickel steel containing from 
from 3 to 6 per cent. of nickel, and to increase slightly the 
ductility. : 
Nickel steel containing a high percentage of nickel does 
not harden, but the 3 to 6 per cent. alloys are capable of 
having a high degree of hardness imparted to them. Owing 
to this fact and other special properties of nickel steel, it is 
necessary to carefully treat it during during the heating 
and forging, as unsuitable treatment may destroy its good 
qualities. Nickel steel cannot be welded in a satisfactory 
manner, and test bars always break at the weld. 
Corrosion.—In regard to resistance to corrosion, nickel 
steel containing from 3 to 6 per cent. nickel does not possess 
any marked superiority over ordinary carbon steel; but the 
25 per cent. alloy shows considerable resistance to corrosion. 
In the author’s experiments repeated boiling in a 1 per 
cent. solution of sulphuric acid extending over four days, 
the steel surface was as brightly polished as when first 
immersed ; it is, however, considered by Hatfield and others 
that all nickel steels yield to the corrosive mixture ulti- 
mately, when the experiments are extended over a sufficient 
time. 
