Abstract
The world’s first plant for manufacture of stainless steel clad structural steel is now operational in the USA. The process consists of coating round steel billets with a spray of stainless steel. A metallurgical bond is achieved so that the billets can be reheated and hot worked into long products while retaining the integrity of the coating. The process consists of teeming stainless steel from a ladle into a spray chamber and atomizing the emerging stream with jets of nitrogen to form a spray of semi-liquid particles. The spray is directed onto a 140mm diameter preheated carbon steel billet to form a thick coating (4 – 5mm). The spraying rate of 50Kg/minute produces clad billet at the rate of 15tonnes/hr. Billet is then hot rolled in a conventional bar mill to make corrosion resistant clad steel sections such as rebar and dowel pins. Coating thickness after rolling is in the range 0.5 – 1.0 mm depending on the final section. Clad products have a life expectancy of 75 – 100 years in high chloride environments such as tidal zones, bridge decks and highways treated with de-icing salts. The spray coating process is described together with mechanical properties of the clad bar and results of corrosion tests. The economics of stainless clad steels vs. other corrosion resistant materials are reviewed.
