THE PUDDLING-PROCESS.
The process of puddling, or the decarbonization of cast iron by stirring it while in a fluid condition and exposing all parts to an oxidizing current of flame and air in a reverberatory furnace, was invented in 1783-84 by Mr. Henry Cort, of Gosport, Eng land. He also invented, about the same time, the use of rollers for the purpose of pro ducing bar iron from the puddled blooms or balls.
"It is not, perhaps, generally known that Mr. Cort expended a fortune of £20,000 in perfecting his invention for puddling iron and rolling it into bars and plates, that he was robbed of the fruit of his discoveries by the villany of officials in a high depart ment of the Government, and that he was ultimately left to starve by the apathy and selfishness of an ungrateful country."* The process of converting pig metal to bar iron in the puddling-furnace, as before stated, is the reverse of the processes employed to produce the pig from the ore in the blast-furnace. In the puddling-furnace the pig iron is reduced to a fluid condition by a strong heat. In this fluid state it is subject to currents of flame and air while agi tated by the tools of the puddler. This brings the iron into contact with the oxygen of the air, which absorbs or burns out the carbon from the pig metal. In other words, the carbon unites with the oxygen and passes off as the vapors of combustion, leaving the iron in a decarbonized and crystalline condition. The crystals are elongated or drawn into fibres by the rolling or hammering process, and thus form malleable or bar iron.
In the puddling-process great care must be taken by the puddler to prevent the burn ing or oxidization of the iron when divested of carbon, which is done by constantly shifting the masses and immersing them in the fluid cinder of the puddling-hearth. The operation of puddling by hand is very laborious, and can only be done by experts without great loss. The stirring process should not be suspended an instant from the time the iron is in a fluid state until it is ready to ball, or is free from its carbon.
In the best puddling-furnaces, expert puddlers make six heats per day, of 4 cwt. to each heat, or 24 cwt. of pigs used, and 22 cwt. of puddled iron produced with an ex penditure of 28 cwt, of coal in the single and 17 cwt. in the double puddling-furnaces to the ton of puddled bars made.
These are the results of the best English puddling-furnaces. We do not do as well at home with the best anthracite coal. The average consumption of coal in our rolling mills is three tons to the ton of railroad bar produced; but this includes, of course, the reheating and rerolling of the puddled bars.
The total consumption of anthracite coal to the ton of railroad iron produced, from the ore to the rail, is an average of five tons, in this country. Where bituminous coal is used, the consumption is from six to seven tons per ton of rail.