IROK AND STEEL 231 



The use of this machine should do much to standardize specifications 

 for railway material.* 



Tests in impact compression, impact tension, and impact flexure 

 are also made, but on account of the uncertainty as to the amount of 

 energy absorbed by the test specimen many engineers do not favor 

 such tests. Many of these objections, however, might be removed by 

 proper standardization. 



Some recent investigations seem to indicate that the impact test 

 shows very little that cannot be determined by static tests. 



182. Cold bending tests. Cold bending tests are tests of the duc- 

 tility of metals, and are designed to show the effect on the metal of 

 being bent in various ways while cold. Such material as rivet steel 

 and Bessemer steel bridge pieces are bent double over a pin of speci- 

 fied radius, and the result noted. In making these tests the angle at 

 which the first crack occurs and the angle at which rupture occurs 

 are read. 



Few machines for making cold bending tests have been made. 

 The tests are usually made by bending the specimen over the edge 

 of a vise, or some such simple device, according to specifications. The 

 tests have never been standardized, but their importance is obvious, 

 since the conditions of actual service are thus applied to the specimen. 



183. Cast iron. Pig iron is a combination of iron with small 

 percentages of carbon, silicon, sulphur, phosphorus, and manganese, 

 obtained from the blast furnace. The carbon probably comes from 

 the fuel used in reducing the ore ; the other impurities come either 

 f n iiii the ore or from the flux. The product is graded, according to 

 chemical composition, into forge pig and foundry pig. Foundry pig 

 is remelted in a cupola furnace and made into castings of various 

 kinds; forge pig is used in making wrought iron. 



Cast iron is a very brittle material, weak in tension and strong in 

 compression. Its great usefulness in engineering structures comes 

 fr<>m the fact that it may be readily molded into any desired form; 

 it is, however, being replaced by the various steel products. The 

 carbon, silicon, and other impurities contained in the iron affect its 

 physical properties. 



For a description of this machine see the report by Professor W. F. M. Goss, Proc. 

 Anier. Soc. for Testing Materials, 1903. 



