Editing Wrought iron (section)

===Puddling process===
{{Main|Puddling (metallurgy)}}
[[File:Puddling furnace.jpg|thumb|Schematic drawing of a puddling furnace]]

A number of processes for making wrought iron without charcoal were devised as the [[Industrial Revolution]] began during the latter half of the 18th century. The most successful of those was puddling, using a puddling furnace (a variety of the [[reverberatory furnace]]), which was invented by [[Henry Cort]] in 1784.<ref>R. A. Mott (ed. P. Singer), ''Henry Cort, The Great Finer'' (The Metals Society, London 1983).</ref> It was later improved by others including [[Joseph Hall (metallurgist)|Joseph Hall]], who was the first to add iron oxide to the charge. In that type of furnace, the metal does not come into contact with the fuel, and so is not contaminated by its impurities. The heat of the combustion products passes over the surface of the puddle and the roof of the furnace reverberates (reflects) the heat onto the metal puddle on the fire bridge of the furnace.

Unless the raw material used is white cast iron, the pig iron or other raw product of the puddling first had to be refined into [[refined iron]], or finers metal. That would be done in a refinery where raw coal was used to remove [[silicon]] and convert carbon within the raw material, found in the form of graphite, to a combination with iron called cementite.

In the fully developed process (of Hall), this metal was placed into the hearth of the puddling furnace where it was melted. The hearth was lined with oxidizing agents such as [[haematite]] and iron oxide.<ref name="Rajput2000">{{cite book |last=Rajput |first=R. K. |title=Engineering Materials |publisher=S. Chand |year=2000 |page=223 |isbn=81-219-1960-6}}</ref> The mixture was subjected to a strong current of air and stirred with long bars, called puddling bars or rabbles,<ref name="Gale1971">{{cite book |first=W. K. V. |last=Gale |title=The Iron and Steel Industry: a Dictionary of Terms |publisher=David and Charles |location=Newton Abbot |year=1971}}</ref>{{rp|165}}<ref name="mi">{{cite book |last=Overman |first=Fredrick |title=The Manufacture of Iron, in All Its Various Branches |publisher=H. C. Baird |year=1854 |location=Philadelphia |pages=267, 287, 344 |url=https://books.google.com/books?id=Gani2eHvhAkC}}</ref> through working doors.<ref name="Tylecote1991">{{cite book |first=R. F. |last=Tylecote |section=Iron in the Industrial Revolution |title=The Industrial Revolution in Metals |publisher=Institute of Metals |location=London |year=1991}}</ref>{{rp|236–240}} The air, the stirring, and the "boiling" action of the metal helped the oxidizing agents to oxidize the impurities and carbon out of the pig iron. As the impurities oxidize, they formed a molten slag or drifted off as gas, while the remaining iron solidified into spongy wrought iron that floated to the top of the puddle and was fished out of the melt as puddle balls, using puddle bars.<ref name="Rajput2000" />

====Shingling====
{{Main|Shingling (metallurgy)}}

There was still some slag left in the puddle balls, so while they were still hot they would be shingled<ref name="msts">{{cite book |last1=Camp |first1=James McIntyre |last2=Francis |first2=Charles Blaine |title=The Making, Shaping and Treating of Steel |publisher=Carnegie Steel Company |year=1920 |location=Pittsburgh |pages=173–174 |url=https://books.google.com/books?id=P9MxAAAAMAAJ |isbn=1-147-64423-3}}</ref> to remove the remaining slag and cinder.<ref name="Rajput2000" /> That was achieved by forging the balls under a hammer, or by squeezing the bloom in a machine. The material obtained at the end of shingling is known as bloom.<ref name="msts" /> The blooms are not useful in that form, so they were rolled into a final product.

Sometimes European [[ironwork]]s would skip the shingling process completely and roll the puddle balls. The only drawback to that is that the edges of the rough bars were not as well compressed. When the rough bar was reheated, the edges might separate and be lost into the furnace.<ref name="msts" />

====Rolling====
{{Main|Rolling mill}}

The bloom was passed through rollers and to produce bars. The bars of wrought iron were of poor quality, called muck bars<ref name="msts" /><ref name="Gale1971" />{{rp|137}} or puddle bars.<ref name="Rajput2000" /> To improve their quality, the bars were cut up, piled and tied together by wires, a process known as [[Faggoting (metalworking)|faggoting]] or piling.<ref name="msts" /> They were then reheated to a welding state, forge welded, and rolled again into bars. The process could be repeated several times to produce wrought iron of desired quality. Wrought iron that has been rolled multiple times is called merchant bar or merchant iron.<ref name="mi" /><ref>{{cite book |first=W. K. V. |last=Gale |title=The British Iron and Steel Industry |publisher=David and Charles |location=Newton Abbot |year=1967 |pages=79–88}}</ref>