238 



STRENGTH OF MATERIALS 



Deflection should not be less than 0.08 in. 



Tensile strength must not be less than 22,000 lb./in. 2 . 



The following specifications for cast iron are suggested by J. \V. 

 Keep as being representative of modern practice.* 



Transverse test bars were cast 1 in. square and 12 in. long, and 

 were tested with a central load. Tensile test bars were cast 1.13 in. 

 in diameter and were tested as cast. 



190. Wrought iron and steel. Wrought iron is made by 1 mining 

 the impurities out of cast iron. In the process tin* foundry pig inm 

 from the blast furnace is first placed in the puddle furnace, where it 

 is heated and stirred until the carbon, silicon, and inan^aiu-se are 

 almost entirely burned out. When taken from the fumuv, the iron 

 is in the form of a pasty ball, which is sqiurzed until the cindei 

 expelled, after which it is rolled into bars known as /////</ /////*. . 

 being reheated it is rolled again, and is then known as merchant 

 If a better grade of wrought iron is desired, the merchant bar is 

 reheated and rolled a^ain, when it is known as lest iron; if rolled 

 :i;ain, the quality is still further improved. 



In methods used by the ancients the ore and fuel were placed 

 together. This necessitated a pure fuel and did not admit of rapid 

 manipulation ; it is still used, however, to obtain wrought iron uf a pure 

 quality, and in obtaining very tine grades of steel. 



Proc. Amer. Soc./or Testing Materials, 1904. 



