A Dictionary of Arts, Manufactures and Mines / containing a clear exposition of their principles and practice

by Andrew Ure

We thus see that carbon may combine with iron in several manners; that the gray cast iron is a mixture of steely iron and plumbago; that the white, rendered gray and soft by roasting, is a compound of steely iron and a carburet of iron, in which the carbon predominates; and that untempered steel is in the same predicament.

For the following analyses of cast irons, we are indebted to MM. Gay Lussac and Wilson.

Table.—In 100 parts.

Cast iron.		Iron.	Carbon.	Silica.	Phos- phorus.	Man ganese.	Remarks.
White cast from	Siegen	94·338	2·690	0·230	0·162	2·590	By wood charcoal
Do.	Coblentz	94·654	2·441	0·230	0·185	2·490	do.
Do.	a. d. Champ	96·133	2·324	0·840	0·703	a trace	do.
Do.	Isère	94·687	2·636	0·260	0·280	2·137	do.
Gray	Nivernais	95·673	2·254	1·030	1·043	a trace	do.
Do.	Berry	95·573	2·319	1·920	0·188	do	Mix. of coke & do.
Do.	a. d. Champ	95·971	2·100	1·060	0·869	do.	Charcoal
Do.	Creusot	93·385	2·021	3·490	0·604	do.	Coke
Do.	a. d. Franche Comté	95·689	2·800	1·160	0·351	do.	do.
Do.	Wales	94·842	1·666	3·000	0·492	do.	do.
Do.	Do.	95·310	2·550	1·200	0·440	do.	do.
Do.	Do.	95·150	2·450	1·620	0·780	do.	do.

Karsten has given the following results as to carbon, in 100 parts of gray cast iron.

Gray cast iron.	Combined carbon.	Free carbon.	Total carbon.	Remarks.
Siegen, from brown iron-stone	0·89	3·71	4·60	By wood charcoal
Siegen (Widderstein), from brown and sparry iron	1·03	3·62	4·65	do.
Malapane, from spherosiderite	0·75	3·15	3·90	do.
Königshütte, from brown ore	0·58	2·57	3·15	coke
Do. at a lower smelting heat	0·95	2·70	3·65	do.

[Fig. 607.] represents in section, and [fig. 606.] in plan, the famous cupola furnace for casting iron employed at the Royal Foundry in Berlin. It rests upon a foundation a, from 18 to 24 inches high, which supports the basement plate of cast iron, furnished with ledges, for binding the lower ends of the upright side plates or cylinder, e. Near the mouth there is a top-plate d, made in several pieces, which serves to bind the sides at their upper end, as also to cover in the walls of the shaft. These plates are most readily secured in their places by screws and bolts. Within this iron case, at a little distance from it, the proper furnace-shaft e, is built with fire-bricks, and the space between this and the iron is filled up with ashes. The sole of the hearth f, over the basement-plate, is composed of a mixture of fire-clay and quartz-sand firmly beat down to the thickness of 6 or 8 inches, with a slight slope towards the discharge-hole for running off the metal. g is the form or the tuyère (there are sometimes one on each side); h the nose pipe; the discharge aperture i is 12 inches wide and 15 inches high; across which the sole of the hearth is rammed down. During the melting operation, this opening is filled up with fire-clay; when it is completed, a small hole merely is pierced through it at the lowest point, for running off the liquid metal. The hollow shaft should be somewhat wider at bottom than at top. Its dimensions vary with the magnitude of the foundry. When 5 feet high, its width at the level of the tuyère or blast-hole may be from 20 to 22 inches. From 250 to 300 cubic feet of air per minute are required for the working of such a cupola. For running down 100 pounds of iron, after the furnace has been brought to its heat, 48 pounds of ordinary coke are used; but with the hot blast much less will suffice. The furnace requires feeding with alternate charges of coke and iron every 8 or 10 minutes. The waste of iron, by oxidization and slag, amounts in most foundries to fully 5 per cent. For carrying off the burnt air, a chimney-hood is commonly erected over the cupola. See [Foundry].

The double-arched air or wind-furnace used in the foundries of Staffordshire for melting cast iron, has been found advantageous in saving fuel, and preventing waste by slag. It requires fire-bricks of great size and the best composition.