CHAPTER XIII. 



STRENGTH PEOPERTIES OF THE PRINCIPAL 

 MATERIALS OF CONSTRUCTION. 



In the present chapter the strength properties of 

 the chief materials used for engineering purposes, so far 

 as they have not been referred to up to the present, will 

 be briefly discussed, and standard test results given. 



IRON AND STEEL. 



The most important materials used for constructive 

 purposes at the present day are the carburets and alloys 

 of iron. These are usually classed as either wrought iron, 

 containing little or no carbon ; steel, containing rather 

 more carbon ; and cast iron, which has the largest per- 

 centage of carbon. Each of these three contains so many 

 different varieties that a more detailed classification is 

 necessary, such as the following : 



CLASSIFICATION OF IRONS AND STEELS. 



(1) Wrought Iron. Consisting of iron containing not 

 more than 0'35 per cent, of carbon. It has a fibrous fracture 

 and is tough ; very malleable at high temperatures, and 

 partly so at low temperatures ; is not susceptible to 

 hardening effects to any appreciable extent. Produced 

 either by puddling or a crucible process, in three or more 

 grades. 



(2) Steel. Consisting of iron containing from" 0'35 to 

 1*50 per cent, of carbon ; malleable at a red heat, and 

 partly so when cold ; is non-fibrous and tough ; is more 

 easily fusible than wrought iron ; and those steels high in 

 carbon, or hard steels, possess the power of hardening 

 when heated or quenched. But this property is only 



