Editing Bessemer process (section)

==Technical details==
[[File:Bessemer Converter (PSF).jpg|250px|right|thumb|Bessemer converter components.]]
Using the Bessemer process, it took between 10 and 20 minutes to convert three to five tons of iron into steel{{snd}}it would previously take at least a full day of heating, stirring and reheating to achieve this.<ref name="Harcourt Brace Jovanovich"/>

===Oxidation===
Blowing air through the molten pig iron introduces oxygen into the melt. This [[oxidation process|oxidizes]] impurities such as [[silicon]], [[manganese]], and [[carbon]]. These [[oxide]]s either escape as gas or form a solid [[slag]]. The refractory lining of the converter plays a role in the conversion — [[clay]] linings may be used when little [[phosphorus]] is present in the raw material. Bessemer himself used [[ganister]] sandstone–in the [[acid]] Bessemer process. Given high phosphorus content, [[Dolomite (mineral)|dolomite]] or [[magnesite]] linings are used in the [[Base (chemistry)|basic]] Bessemer [[limestone]] process. Materials such as [[spiegeleisen]] (a ferromanganese alloy), can then be added to the molten steel to establish specific properties.

===Process===
When the required steel forms, it is poured into ladles and then transferred into moulds while the (lighter) slag is left behind. The conversion process, called the "blow", initially took approximately 20 minutes. During this interval, the progress of the oxidation of the impurities is judged by the appearance of the flame in the mouth of the converter. The human eye was later replaced by photoelectric methods of monitoring the flame, increasing ultimate precision. After the blow, carbon is readded to the liquid metal and other alloying materials are added.

A Bessemer converter could treat a "heat" (batch of hot metal) of 5 to 30 tons at a time.<ref>{{cite web |url=http://www.steeltalk.com/bessemer_convertor.php |title=Bessemer Converter |website=www.steeltalk.com |access-date=14 January 2022 |archive-url=https://web.archive.org/web/20080117065932/http://www.steeltalk.com/bessemer_convertor.php |archive-date=17 January 2008 |url-status=dead}}</ref> They were usually operated in pairs: one was blown while the other was filled or tapped.

==="Basic" vs. acidic Bessemer process===
{{further|Gilchrist–Thomas process}}
Industrial chemist [[Sidney Gilchrist Thomas]] tackled the problem of phosphorus in iron, which resulted in the production of low grade steel. Believing that he had discovered a solution, he contacted his cousin, [[Percy Gilchrist]], who was a chemist at the [[Blaenavon Ironworks]]. The manager there, Edward Martin, offered Thomas test equipment and helped him draw up a patent issued in May 1878. Thomas's invention consisted of using [[Dolomite (rock)|dolomite]] or [[limestone]] linings for the Bessemer converter rather than clay, and it became known as the 'basic' Bessemer rather than the 'acid' Bessemer process. An additional advantage was that the processes formed more slag in the converter, and this could be recovered and used profitably as fertilizer.<ref>{{Cite web|url=http://www.visitblaenavon.co.uk/en/WorldHeritageSite/TheBlaenavonStory/BlaenavonandtheGilchrist-ThomasProcess.aspx|archiveurl=https://web.archive.org/web/20131212031458/http://www.visitblaenavon.co.uk/en/WorldHeritageSite/TheBlaenavonStory/BlaenavonandtheGilchrist-ThomasProcess.aspx|url-status=dead|title=Blaenavon World Heritage Site: Blaenavon and the 'Gilchrist-Thomas' Process|archivedate=12 December 2013|website=www.visitblaenavon.co.uk}}</ref>