Soap may be framed and finished in this state, but almost invariably it receives a further treatment called " refining " or " fitting," in which by remelting with water, with or without the subsequent addition of other agents to harden the finished product, the soap may be made to contain from 60 to 70% of water and kept present a firm hard texture.
This method is rarely practised except by the rollers of zinc. A certain amount of refined zinc can be dipped from the furnace; a further amount, nearly free from iron, can be liquated out of the ingots cast from the bottom of the bath in a subsequent slow remelting, and it is sometimes possible to eliminate a zinciferous lead which collects in the sump of the furnace.
Some brassfounders break from a single ingot the quantity of zinc required to produce the amount of brass they wish to compound in one crucible, but when perfect uniformity is desired the importance of remelting the zinc on a large scale cannot be too strongly emphasized.
Its specific gravity is 1 54, and after remelting 1 56; after distillation it is 1.52.
In time the smith learnt how to convert this unwelcome product into wrought iron by remelting it in the forge, exposing it to the blast in such a way as to burn out most of its carbon.
With the second period began, in the 14th century, the gradual displacement of the direct extraction of wrought iron from the ore by the intentional and regular use of this indirect method of first carburizing the metal and thus turning it into cast iron, and then converting it into wrought iron by remelting it in the forge.
Grey iron castings are made by remelting the pig iron either in a small shaft of " cupola " furnace, or in a reverberatory or " air " furnace, with very little change of chemical composition, and then casting it directly into suitable moulds, usually of either " baked," i.e.
The shaping processes include the mechanical ones, such as rolling, forging and wire-drawing, and the remelting ones such as the crucible process of melting wrought iron or steel in crucibles and casting it in ingots for the manufacture of the best kinds of tool steel.
Indeed, the remelting of cast iron to make grey iron castings belongs here.
Thus the crucible process in its American form both carburizes and remelts, and the open hearth process is often used rather for remelting than for purifying.
It has long been seen that there would be a great saving if this remelting could be avoided and " direct metal," i.e.
At Hourpes, in order to save the expense of this remelting, the molten cast iron as it comes from the blast-furnace is poured directly into the puddling furnace, in large charges of about 2200 lb, which are thus about four times as large as those of common puddling furnaces.
For long all the best high-carbon steel was made by remelting this blister steel in crucibles (§ 106), but in the last few years the electric processes have begun to make this steel (§ 108).
It is still in great demand for certain normal purposes for which either great ease in welding or resistance to corrosion by rusting is of great importance; for purposes requiring special forms of extreme ductility which are not so confidently expected in steel; for miscellaneous needs of many users, some ignorant, some very conservative; and for remelting in the crucible processAll the best cutlery and tool steel is made either by the crucible process or in electric furnaces, and indeed all for which any considerable excellence is claimed is supposed to be so made, though often incorrectly.
- Cupola Furnace for Remelting cast iron of the Pig Iron.