IKON AND STEEL 



241 



Nickel is added to steel up to about 35 per cent. When the per- 

 centage of nickel is low, say about 5 per cent or less, the elastic limit 

 and tensile strength are raised without any reduction in the elonga- 

 tion or in the contraction of area. Because of this increase in strength 

 without loss of ductility, nickel steel is used in the manufacture of 

 armor plate, armor-piercing shells, boiler tubes, shafting, etc., where 

 a steel is needed which shall combine great strength with toughness. 

 The following table shows the relative properties of low carbon steel 

 tubes and high nickel steel tubes.* 



The same authority also gives the average tensile strength of six- 

 teen steel tubes, composed of 25 per cent nickel, as 108,913 lb./in. 2 

 for unannealed specimens, and 97,300 lb./in. 2 for annealed specimens. 

 The elongation in the former case was 28 per cent in 7.87 in., and 

 in the latter case 38 per cent in the same length. 



Tests made by the Watertown Arsenal on a 3.37 per cent nickel 

 steel gave an average elastic limit of 56,700 lb./in. 2 and a tensile 

 strength of 90,300 Ib./inAf 



193. Steel castings are made both by the Bessemer and open- 

 hearth processes. In the Bessemer process the iron is first reduced 

 to wrought iron, and then spiegeleisen, or ferromanganese, added to 

 furnish the necessary carbon. Aluminum may be added to prevent 

 blowholes. The metal is cast in the same way as in making other 

 castings. 



On page 242 is given a report of a series of tests made at the 

 W;itertown Arsenal on castings for gun carriages.^ The elastic limit 

 varied from 47,000 lb./in. 2 to 21,500 lb./in. 2 , and the tensile strength 

 from 81,000- lb./in. 2 to 43,000 lb./in. 2 . Good average values might be 

 given as 30,000 lb./in. 2 at the elastic limit and 66,000 lb./in. 2 at the 



Proc. Soc. Naval Architects and Marine Engineers, November, 1903. 

 t Watertown Arsenal Report, 1899. J Watertown Arsenal Report, 190d. 



