THE ANATOMY OF A STEEL RAIL 61 



of rails let us digress a little to explain the birth of the 

 rail. The steel for a rail is made from a molten mass of 

 cast iron, or pig iron, which is iron containing a large 

 amount of impurities, the most notable of which is carbon. 

 This cast iron is run, white-hot and liquid, from a blast 

 furnace into a Bessemer converter, through the bottom of 

 which air under pressure is blown in large quantities. The 

 impurities in the pig iron are burned by the oxygen in the 

 air blast, arid pass off as gases or rise to the top of the 

 refined metal as slag, essentially a silicate of iron. Fig. 2 

 is an illustration of a Bessemer converter in full blast. 



The whole operation of converting ten tons of cast iron 

 into steel takes only about ten minutes, and when complete 

 the molten mass is made to absorb the required amount of 

 carbon to give the necessary strength to the rail by adding 

 spiegeleisen or ferro-manganese, both alloys of iron and 

 manganese containing carbon. 



We now have a molten mass of steel, which is poured 

 into iron molds to solidify. When cool the molds are 

 stripped off and we have left large masses or ingots of 

 steel, and this steel is only an alloy of iron and carbon 

 with a few impurities present in very small quantities. 

 From one of these ingots several rails may be made by 

 reheating and passing it through suitably shaped rolls. 



I have shown here in Fig. 3 a diagram of a longitudinal 

 section of one of these ingots. It is not at all homogeneous, 

 as can readily be seen, and has a cavity or "pipe," above 

 C, which is caused by the unequal cooling of the sides and 

 the top. The black spots near the edge, A and B, are 

 called blow holes and are caused by imprisoned gas; they 

 are subsequently closed by the rolling, so that they are not 

 detrimental to the quality of the steel rail. 



Now this "pipe" cavity should be all cut off, as a rail 

 which is rolled from the end of the ingot containing this 

 pipe is sure to be faulty, for it will always contain this 

 cavity, which will be but imperfectly closed by the rolling 

 and only elongated. To be absolutely sure that all the 



