CHILLED IRON. 



15 



plant for melting; snitable heat for pouring; prevention 

 of lionoycombing ; forrostatic pressure of head ; " feedin" " 

 etc. Molting for rolls being mostly conducted in rever- 

 bcratorlos, the variations in the condition of the furnace 

 atmosphere, altering from reducing to oxidising, and vice 

 versa, in cases of bad stoking and different fuels, were re- 

 ferred to as occasionally affecting results. Melting beino- 

 an operation involving appreciable cost, and the achievement 

 of corresponding furnace effects in a series of meltings of a 

 standard pig mixture being a matter of much moment, the 

 question of the suitability of Siomen's Radiant-lioat Molt- 

 ing system for this purpose was introduced for discussion. 



For promoting the success of a chilled roll in its work, 

 latlieing or turning it to perfect circularity in the necks first, 

 and then turning the body while the necks bear in steady 

 brasses, are matters of the utmost importance. Tlie author 

 next referred to the great excellence for chilling purposes 

 possessed by some American pig irons, and to the fact that 

 iron of a given carbon content derived from some ores and 

 fluxes may differ much, in chilling properties from iron hold- 

 ing a similar proportion of carbon (free and combined) 

 derived fi'om other ores and materials. Those irons are best 

 which develop the hardest possible chill most uniformly to 

 the desired deptli, without producing a too abrupt lino of 

 division between the hai'd white skin and the softer grey 

 body. 



The impossibility of securing a uniform quality and che- 

 mical composition in any number-grade of any brand of 

 pig iron over a lengthened period was adverted to. At some 

 blast furnace establishments the pig-iron product, owing to 

 ono or other of several causes that were mentioned, varies 

 from day to day. In others the changes occur less frequently 

 but with equal certainty. Consequent from this a too reso- 



