Chlorination (metallurgy)
Chlorination , also called chlorination, is a term from the metallurgy of non-ferrous metals . By supplying chlorine gas or thermally chlorine-releasing organic compounds such as hexachloroethane , undesired elements such as calcium or sodium can be removed, preferably from melts of aluminum or copper alloys, by converting them into their chlorides , which are either volatile or go into the slag .
When melting and casting aluminum and its alloys, it has been shown that the production of high-quality cast parts is difficult because of the tendency of the aluminum melts to oxidize and absorb hydrogen. The hydrogen solubility in the melt is 15 times higher than in the solid state, so when the melt solidifies, precipitation occurs with the formation of bubbles in the casting. Purging the melt with a suitable purging gas reduces the hydrogen content. Chlorine gas was proposed by David Ronald Tullis in 1926 and mixtures of chlorine and an inert gas were soon developed as a purge gas. Chlorine reacts with aluminum to form aluminum chloride and because this leaves the melt at approx. 180 ° C with a surge, it is suitable as a rinsing agent / degassing agent (see also melt treatment ). Today an inert purge gas is usually used, for. B. nitrogen or argon is used for aluminum melts, to which in some cases sulfur hexafluoride or chlorine is added in low concentrations (<2.5%).
Individual evidence
- ↑ a b Stephan Hasse: Giesserei-Lexikon . Fachverlag Schiele & Schoen, 2007, ISBN 3-7949-0753-1 , p. 186 ( limited preview in Google Book search).
- ↑ Google Patents: Patent US1636881 - Process for purifying or refining metals and alloys - Google Patents , accessed May 16, 2014
- ^ Wolfgang Schneider: Continuous Casting . John Wiley & Sons, 2006, ISBN 978-3-527-60715-0 , pp. 13 ( limited preview in Google Book search).
- ^ Lexicon: Giesserei - Lexikon , accessed on May 16, 2014.