Copper in Steels

Copper in Steels  Copper (Cu) provides interesting alloying advantages to steel and steel welds. Cu (atomic no. 29 and atomic weight 63.54) has a density of 8.96 gm/cc. The melting point of Cu is 1083 deg C while the boiling point is 2570 deg C. Cu is normally added to steel to increase corrosion resistance. Experimentation with the addition of Cu to structural steels for its ability to impart good atmospheric corrosion resistance properties began in the year 1916 in the USA. The first commercial use of Cu bearing steel as atmospheric corrosion resistant steel was during the period 1933 to 1935. Cu is beneficial to atmospheric corrosion resistance when present in amounts exceeding 0.20 %. The atmospheric corrosion resistance steels are also called weathering steels. Addition of Cu in steelmaking Cu is added to steel in the form of pigs, refined ingots or as copper and nonferrous alloy scrap. Any Cu already present in the steel scrap charge is carried over into the liquid steel with little or no loss. Scrap electric motors containing usually 10-15 % Cu are often used as a source of Cu during steelmaking. Cu can be added either in the steelmaking furnace or in the teeming ladle. Both techniques of Cu addition give very high recoveries. Losses, if any, are due to the mechanical reasons. When addition of Cu is made in the steelmaking furnace, it should be done before the end of decarburization. Effects of copper on steels The ability of Cu bearing steel to withstand atmospheric corrosion is not the major reason which provides the impetus for the development of Cu bearing steels today. Until recently, it was not fully recognized that along with the improved corrosion resistance, the precipitation of Cu can make a significant...