Explosion weld clad for magnesium melting furnace crucibles

Large magnesium melting and alloying crucibles, referred to as "mag pots", are typically constructed of cast iron or low carbon steel. The steel interior is resistant to attack by the molten magnesium. However, the exterior of the steel pot is subject to high temperature oxidation. Cleanliness and control of iron oxide accumulation in the furnace is critical for safe operations. Clad pots consisting of an exterior layer of high temperature stainless steel or nickel alloy and a low carbon steel interior provide a number of operational benefits. These include improved safety, increased dimensional stability, and considerably longer service life, especially for gas fired furnaces. The explosion weld (EXW) cladding technology has been used for clad pot manufacture since the mid-1980's. The clad's metallurgical bond is not deleteriously affected by long term operation at high temperatures or the stresses of cyclic temperature exposure typical during mag pot operation. Test data indicate long-term stability at up to 1000degreesC. The presentation discusses the various metal alloys that are being used in magnesium pot applications, their performance attributes and limitations, clad fabrication techniques, and inspection methods. Pot design issues as related to both performance and economics are discussed. Other applications such as hydrometallurgy autoclaves, refinery reactors, chemical process vessels and heat exchangers, as well as shipboard and electronic uses are manufactured from clad metal. Different metals such as nickel alloys, stainless steel, titanium, zirconium, tantalum, aluminum; copper alloys have been commercially clad using EXW for decades. Some of these are briefly discussed.