118 JOURNAL OF THE [October, 



the metal has been strained upon the surface beyond its elastic 

 limits, and surface wear of metal rapidly occurs. To check this 

 wear we need high elastic limits of the metal for the surfaces in 

 contact. The metal in the tires of wheels abrades on the surface 

 and also drops out in patches, as may be seen in specimens Nos. 

 3 and 4. 



It will be readily understood that, while it is desirable to have 

 sufificiently high elastic limits in the steel to keep the section 

 from taking permanent set under the loads or trains, it is neces- 

 sary to have high elastic limits in the metal to resist wear. Steel 

 of .35 to .40 carbon has elastic limits in the head varying from 

 38,000 to 45,000 pounds per square inch, and even then, in the 

 thin-flanged rails, is liable to be brittle. In steel like that shown 

 in specimen No. 4 the elastic limits range from 60,000 to 65,00c 

 pounds in the head, and it is tough in the sections in which it is 

 used. In the 75-pound section, into which several thousand 

 tons have been rolled, the rails are exceptionally tough, exceed- 

 ing, so far as any records have been published, any tests which 

 have been made. In the 95-pound rails, into which many thou- 

 sand tons of high carbon metal have been rolled, they are much 

 tougher than was supposed possible to make such large sections. 

 The tendency of improvement in quality of steel is now the pro- 

 duction of a fine texture having high elastic limits and consider- 

 able percentage of elongation before the full limit of tensile 

 strength is reached. Specimen No. 5 shows the end of a tensile 

 specimen of 53,470 pounds elastic limit and 23 per cent of elonga- 

 tion, the fracture fine and silky, showing at once that it was a 

 tough piece of metal. No evidence of coarse crystallization on 

 the interior of the specimen is to be seen, portions of the matrix 

 penetrating and pulling out from the interior of all the crystals. 

 This steel has been worked to make a fine texture. Specimen 

 No. 6 is from the side of specimen No. 5, and shows on the ex- 

 terior a tendency to separation on the outside surface of the 

 original large crystals as soon as the steel has passed the elastic 

 limits. On the interior, each crystal being surrounded, greater 

 flow or distortion takes place before separation. This specimen 

 will also serve to better illustrate my remarks about the necessity 

 of high elastic limits in surface of the rails to resist wear. 



