Cobalt in Steels

Cobalt in Steels  Cobalt (Co) (atomic number 27 and atomic weight 58.94) has density of 8.85 gm/cc. Melting point of Co is 1493 deg C and boiling point is 3100 deg C. At temperatures below 417 deg C cobalt exhibits a hexagonal close packed structure. Between 417  deg C and its melting point of 1493 deg C, Co has a face centered cubic (fcc) structure. Co is a magnetic metal with a curie temperature of 1121 deg C. The phase diagram of the Fe-Co binary system and is given at Fig 1. Fig 1 Fe-Co binary phase diagram Co is not a popular element which is commonly added to alloy steels. It does have some effects but these can also be achieved with other alloying elements such as molybdenum (Mo), and nickel (Ni) etc. at lower costs and mostly with better results. Due to this factor, Co does not find enough use in high tonnage low alloy steel production. However it does have some niche markets in steel. Co becomes highly radioactive when exposed to the intense radiation of nuclear reactors, and as a result, any stainless steel that is in nuclear service will have a restriction in the Co content which is  usually around 0.2 % maximum. Adding agents In the production of co bearing alloy steels, additions of Co during the steel making is made in the form of Co metal which is supplied to steel producers in the form of briquettes, granules, and broken electrolytic cathodes. Content of Co in these additive agents is usually in the range of 98 % to 99.9 %. Scrap of super alloys normally contains high percentage of Ni and hence is not used for the production of tool steels. However this scrap can be used...