The beds were formerly molded exclusively by hand and still are in many cases. The sand is leveled off in the cast house floor, there is a pattern for the sow and one for each pig, which are set down on the level surface thus prepared, the sand shoveled off the bed to level it is thrown back between the pigs and tramped to place to pack it, then struck off the top of the pig patterns. These, which are made with a considerable taper, are then drawn by hand and thrown to the place for the next bed below, followed by the sow pattern.

Fig. 216. Part of pig bed or comb in jaw of pig breaker.

This probably requires the most labor of any operation of importance around the blast-furnace, and no means have been found as yet to reduce it to a very great extent, although where there is a crane in the cast house the pattern for the whole bed is made up in one piece and handled by the crane; this saves a certain amount of manual labor, but so small a proportion of the total that the practice has in some cases been abandoned for the use of the old single patterns.

Various attempts have been made to reduce this labor but the sand has to be cut up with shovels after each cast has been watered down, not only in order to set in the pigs, but also because it is too much compacted by the wetting to provide the necessary free vent for the gases. This, with the necessity of having the beds nearly level but with just enough fall to the sows and the pigs to cause the iron to run into them without overrunning the far ends, has made conditions too difficult to be met by machinery sufficiently simple and robust to perform the service in other particulars.

It seems not improbable now that the increasing use of the casting machine will eliminate sand casting entirely before mechanical methods are developed for molding the pig beds.

Handling Liquid Pig Iron

In the early days of the Bessemer process, the first applied to the manufacture of steel on a great scale, it was customary to cast the iron at the blast-furnace as described, take it to the steel works, melt it down into cupolas and then take it to the converters for conversion into steel. This was done so that an opportunity might be provided to analyze the iron and to make the mixture in the cupola suitable for use in the converters. This practice involved an enormous waste in two ways, first the labor of casting the iron into pigs as described above, and the handling of the pigs; second, the labor and fuel required for remelting these in the cupola. This was accompanied by a very objectionable increase in sulphur from the coke used in remelting.

Many metallurgists sought to eliminate this double loss by using the metal direct, but furnace practice was not as regular and uniform in that day as it is now, and there was no certainty that the iron produced at a given cast would be suitable for the converters because the last cast had been, and if the variation in composition were great the converter practice was completely upset.