The increase of furnace outputs during the nineties, of which I have spoken, required very large cast houses to take care of the iron, and the labor involved in breaking and carrying out these huge quantities of iron by hand was, as I have already explained, frightful. The entire plant depended upon iron carriers, since the furnace could not be operated unless the iron were carried out, not any time but within a very limited period, so as to permit the beds to be made ready for the next cast. These conditions had the result of making this class of labor extremely hard to handle.

Conditions in this respect were, in one way, made worse by the growing use of hot metal at the steel plants, because it was necessary to have the iron carriers for Sundays and for emergencies when the steel works could not take the iron, while these men were not needed the rest of the time. This condition brought a demand for a mechanical means of taking care of the iron from the furnace. Casting machines had been in use at a much earlier period for copper, lead, etc., on a small scale, and under rather easy conditions, owing to the fact that the temperatures of those metals are far below the melting point of iron, so that iron molds could be used without great difficulty.

Fig. 219. Hol-metal ladle in pouring chain, pouring into branching trough which fills molds.

But the case was quite otherwise with the blast-furnace; the only material of construction available was iron or steel, and the iron cast into either of these was likely to burn fast to them if they were not thoroughly protected, while if the metal were poured into them while wet violent explosions would result.

Various engineers attacked this problem, but the credit for the first successful solution belongs to E. A. Uehling, who designed a machine consisting of two endless chains in tandem. The first carries molds for the pigs into which the iron is cast, it is chilled by passing under a heavy spray of water on its course, then discharges at the terminal sheave on to the second chain, a conveyor of slats running for some distance under water, which cools the iron down to a temperature low enough to do no harm, this conveyor in turn discharging on to the railroad cars which take the iron to its final destination.

Through the courtesy of the Heyl & Paterson Company I am able to show drawings, and an excellent set of photographs, of one of the largest installments of these machines ever built. Fig. 219 shows the ladle in a tipping chair which is elevated by the jib crane shown at the right and pours into a trough at right angles to the track, which branches both ways at its far end, each branch pouring on to a separate strand of the pig machine.

Fig. 220. First or casting chain of group of Uehling machines.

Fig. 220 shows a general view of the ascending chain of the machine with the returning buckets on the under side.

Fig. 221. Group of Uchling type machines.

Fig. 221 shows clearly a general view of the machines, the head houses where the casting chains discharge on to the cooling conveyors, the terminal houses from which the latter discharge into the cars, and the excellent ladder arrangement of tracks for serving the machines without the necessity of switching the cars under all of them to reach any desired car.

A view of the cooling conveyors with their water trough and the return side of the chain below is shown in Fig. 222.

The difficulty of having the metal burn on to the molds is obviated by having a jet of lime water from a tank underneath the return chain thoroughly sprayed up into the buckets as they pass over it on their return trip. The heat remaining in the mold causes the lime water to dry on it in a heavy white film, which of course is extremely refractory and prevents the contact of metal to metal, without which burning fast does not occur.

Another type of machine was brought out about the same time in which the functions of both chains are merged into one. This was the design of the Heyl & Paterson Company, who now build both the Uehling type of apparatus and their own.

Fig. 222. Coaling conveyors for Uehling type of machine. Water troughs empty.

In this apparatus one chain performs both functions. The metal is cast into it at one end, it then passes down a slight grade into a long tank standing full of water where the iron is thoroughly cooled, rises out of this tank at a sharp elevation and is discharged over the end sheaves directly into railroad cars.

A photograph of an installation of this type is shown at Fig. 223, also by the courtesy of the Heyl & Paterson Company. Unfortunately the machine was empty at the time the picture was taken, but the molds show so clearly, that their action is perfectly obvious, so is the way in which they pass under the water and out again and the overflow for keeping the water at the proper level. A photograph of the same apparatus before the water was turned into the tank is shown in Fig. 224. The molds used in this conveyor are of steel, formed in the hydraulic press out of a piece of plate. They are subjected to terrific strains with the hot metal on one side of them and the cold water on the other, and after a certain amount of this service they lose their shape but can be repressed and restored to useful condition several times before they break from this treatment.

In some cases cast-iron molds are used instead of steel. These of course fail by cracking and not by bending and are not capable of any further use after such failure. On the other hand they can be melted up and recast direct from the furnace in the floor of the cast house with very small expense, whereas when the steel molds once fail the loss is greater.

Fig 223. Heyl & Paterson type of casting machine, steel mold, single chain, trough filled with water.

Both styles of molds have their advocates and both continue to be used after a number of years experience so that the question of whether it pays better to use one kind or the other is probably very largely a local question.

The merchant blast-furnace isolated from steel works will probably prefer the cast-iron molds which it can produce from its own metal with a small amount of labor, while the steel works making steel plate and having available machinery for pressing the molds may find it cheaper to use the steel.

The introduction of casting machines of one type or the other has become practically universal at blast furnaces directly connected with steel works, and even at many merchant furnaces. The huge cast house was one of the prominent features of the blast-furnace of former times, it has disappeared at modern plants and nothing is left of it except a building large enough to cover the troughs in which the iron is run to the spouts above the ladles and to serve as a protection against the weather around the base of the furnace itself.

Fig. 224. Heyl & Paterson type of casting machine, steel mold, single chain.