STKKXOTll OK U'KOUCHT ll!o\. 



There is a wide range in the varieties of wrought iron 

 which are produced, varying from the highest quality 

 Yorkshire irons with a comparatively low tensile 

 strength of from 20 to 28 tons per square inch, with 

 an elongation on lOin. of 30 per cent., and reduction of 

 area of over 40 per cent. to the " common " merchant 

 iron with a tensile strength of 22 tons per square inch or 

 more, extension of from 12 to 2 per cent., and a reduction 

 of area of from 20 to 5 per cent. 



100 



JO 



10 20 30 40 50 60 



Loads. Tons per sq. in. on original section. 



FIG. 170. COMPRESSION LOAD-STRAIN DIAGRAM FOR SPECIMEN OF LOWMOOR IRON 

 UN. IMAM. AND '2IN. LONG. 



Wrought iron is characterised by the fibrous fracture 

 which it exhibits under a tension test. This fracture may 

 have a uniform, fine fibrous appearance, as in the best 

 brands, or the fracture may be wholly or in part 

 crystalline and laminated. The lamination is caused by 

 the process of manufacture, and may be due to the 

 presence of slag in thin layers, which prevents the metal 

 from being properly united. The crystalline appearance 

 may be in son^e cases caused by the sudden application 

 of the load. 



The following table exhibits some of the strength 

 properties of a number of brands of wrought iron as given 

 by different authorities : 



