PROPERTIES OF STRUCTURAL METALS. 33 



until the proper degree of oxidation is secured, and then 

 working of the molten metal into a pasty mass or "puddle- 

 ball," which may then be squeezed or hammered into a suit- 

 able shape or " bloom" for rolling into bars, technically 

 known as "muck-" or "puddle-bars." When cold, this inter- 

 mediate product is sheared and bundled into piles of proper 

 sectional area, to which wrought scrap is most commonly 

 added, after which. the pile so formed is brought to a welding 

 heat in a "heating-furnace," to be afterward passed through 

 the finishing rolls, 'becoming "merchant iron," a finished 

 product. 



The strength and quality of the finished product depends, 

 naturally, upon the character of the crude iron or "stock," 

 the skill in puddling, or reducing the non-metallic sub- 

 stances, and particularly upon the method and materials used 

 in forming the " pile" to be made into " blooms." All met- 

 allic iron contains more or less impurities, and in general such 

 elements as silicon, manganese, carbon, sulphur, and phos- 

 phorus appear; the best wrought iron can only be produced 

 from crude iron containing a limited percentage of sulphur 

 and phosphorus, neither of which can be entirely eliminated 

 in the puddling process, a sufficient percentage being left in 

 the product to give unfavorable results if they were able to 

 exert their full effect in the production of crystallization of 

 the fibres of the metallic iron ; but the slag, resulting from the 

 other non-metallic impurities, overcomes this tendency in a 

 degree. 



The presence of considerable percentages of sulphur pro- 

 duces in the finished iron a condition termed by smiths as 

 "red short "- an inclination to disintegrate or crumble when- 

 ever the iron is heated to a working temperature ; the cohesion 

 of its particles being affected adversely, the strength of the 

 metal is correspondingly reduced. 



The effect of phosphorus, the most detrimental of all the 



