Puddling (metallurgy)
The puddle method (also called reverberatory furnace, refining ) is a process for the production of steel from pig iron. In puddling produced malleable iron is also called wrought iron (English wrought iron ). When this material is curable, it is also called forged steel.
Invented by the Englishman Henry Cort puddling 1784. He had noticed that the carbon in hot cast iron fizzles when air touches it.
Method
In the fire chamber coal or other fuel is burned. Thereby melting the pig iron, which is located in the trough- shaped hearth. The passing across the iron hot air leaves the impurities such as carbon oxidize before they escape through the chimney. Iron occurs during the process with hot air into contact, not with the coal, and thereby not contaminated again.
When puddling is the pig iron in the large pans (English puddle = " puddle " ) melted a Puddelofens and then stirred with long poles (English puddled ) to produce steel, with frequent stirring.
Thus, the slag layer is broken up and repeatedly exposed to oxygen-containing combustion gases and thus, the iron is refined in order to expel the impurities, and to combust the carbon.
Further processing of the billet (iron pieces ) allows the generation of low-cost mass steel. This work was extremely difficult and dangerous. A Puddelvorgang lasted about 24 hours, had become to malleable iron from the crude steel.
The quality of the steel depended largely on the skill and power of Puddlers. There were chunks of steel that brought the puddlers with tongs from the oven.
This was the first time be produced in larger quantities a break-resistant, elastic steel. Until then there were only two iron materials that were available in larger quantities. Firstly, cast iron, which was very brittle but due to high carbon content. On the other wrought iron, is obtained from the smelting furnace, manufactured at the often almost pure iron. By reforge and refining slag proportions are driven off and the carbon content set by the fire management. However, this process was very expensive mainly because of the high labor costs.
But the puddling process was very labor intensive. In addition, the furnace constantly spent fuel. The furnace was not allowed to cool down completely to prevent damage to this and cheering to shorten ( after holidays ). Thus, this method was expensive compared to current methods. In addition, only quantities not exceeding 300 kg iron could be processed in a single operation in a puddling furnace. The production of large quantities of steel has not been possible in this manner.
History
The puddling process is one of the oldest methods for steel production. It was developed in 1784 by Henry Cort and gained during the onset of the industrialization of great importance (eg for the production of steam engines ). The method was in use until the late 19th century, where it was gradually replaced in the second half of the 19th century by the Bessemer process and later the Thomas process, which usually turned out to be more economical.
It is known that the rusted steel was particularly resistant to corrosion due to the phosphorus content and the British Navy therefore insisted on its use in shipbuilding.
Henry Bessemer realized that the oxygen of the inflated air reacted with the carbon atom of iron and thereby generated enough heat to keep the liquid iron. An additional fuel was no longer necessary. With this method, not only the carbon burned, but also contained in the iron-sulfur and other impurities. It remained only steel left.
Franz Anton Lohage and Gustav Bremme from Unna to generate hardenable steel in the puddling furnace succeeded. The new process created a high-quality intermediate, the welding of steel.
The puddling process lost its importance, when spread with the Bessemer converter and later the Thomas process more efficient and above all, much faster cast iron conversion method: A batch of pig iron could be converted into the Bessemer converter in 20-30 minutes to steel.
Use
Use was rusted steel in steel construction, among other things:
- Rhine bridge Waldshut -Koblenz, built 1858-1859
- Griethausen railway bridge, built 1863-1865
- Eiffel Tower, built 1887-1889