240 



STRENGTH OF MATERIALS 



strength, from 47,900 lb./in. 2 to 124,800 lb./in. 2 ; the elongation, from 

 46.6 per cent to 2.80 per cent; and the reduction of area, from 74.8 per 

 cent to 3.30 per cent.* The following table gives average values of 

 the ultimate strength in both tension and compression for Bessemer 

 and open-hearth steel containing different percentages of carbon. 



Carbon tool steel furnishes material for springs, saws, chisels. Hies, 

 etc. When annealed it is strong in both tension and compre- 

 and quite ductile, but when heated to the critical temperature and 

 then quenched it becomes weak, brittle, and hard. 



Silicon in carbon steel and wrought inn generally strengthens the 

 material, but decreases its ductility. In amount it is usually less than 

 0.6 per cent. 



Manganese increases both the strength and hardness of carbon steel 

 and wrought iron, and decreases ductility to some ext-m. M<MV than 

 1.5 per cent makes the steel very.brittle, "When manganese is present 

 in quantities of from 10 to 15 per cent, with a small amount of car- 

 bon, say 1 per cent, the steel becomes hard and is used for castings 

 and forgings. When annealed the castings are both strong and tough 

 enough to resist wear. 



Sulphur increases the brittleness and hardness of steel and wrought 

 iron, and is, in general, a very harmful ingredient. Low percentages 

 of sulphur somewhat increase the tensile strength. 



Phosphorus increases hardness and tensile strength, but decreases 

 ductility, making the metal weak under impact and unsuited for any- 

 thing but static loads. 



Proc. Inst. Civ. Eng., 1895. 



