METHODS FOR CALCULATING THE ANALYSES OF MIXTURES.
Some adopting chemistry in making mixtures of
iron have the impression that iron should come from the furnaceman to them possessing the exact analysis required for charging. It is rare that furnace-men can do this. In our practice, although surrounded by blast furnaces from which we may obtain iron, we are often compelled to accept two or more different grades of extreme variations of silicon, etc., in order to make a mixture desired. As a rule, two or three different grades will often have to be accepted, especially by those using a large amount of iron, in order to obtain the average which should be charged. (See Chapter XXL, page 155.)
To illustrate methods that will utilize iron of different grades as used by the author and others, we will suppose that a charge of 2,000 pounds having an average composition as shown in Tables 39 and 40 is desired. These tables show that by a mixture of three different grades of iron and two of scrap, an average of 2.00 silicon, .032 sulphur, .62 manganese, .435 phosphorus, and 3.80 carbon, as shown in Table 41, is obtained in the iron to' be charged into the cupola Another plan is to divide the weight of each kind of iron into percentages, after the method seen in Table 42. grade of iron very distinct from the other specialties shown, owing to such castings having to stand radical, changes of temperatures, which cause an action of alternate expansion and contraction while the castings are in use. Iron of a medium soft character and low in phosphorus, or what is termed regular Bessemer, is found best for such castings. The cannon of No. 38 calls for a grade of iron that should be of fair ductility, but at the same time possess the greatest strength to be obtained. Cannons are generally made from the com-o.n. in ladle 1,772 Ibs. .100" -326 " I.IOO .242 3