ALUMINIZED STEEL GRADES WITH IMPROVED COATING STABILITY AT HIGH-TEMPERATURES

The present paper reviews the physical principles, the metallurgical d evelopment and the industrial implementation of two new grades of type 1 aluminised sheet steels. The materials are characterised by a much improved high temperature behaviour resulting from the inhibition of t he growth of intermetallic phases due to the formation of an AIN diffu sion barrier. This diffusion barrier is due to minute amounts of inter stitial N (< 20ppm) in the substrate at the time of use under high tem peratures of the finished part, An original metallurgical method, whic h is different from existing or patented metallurgical routes, was use d to develop the new products, Two grades were developed, which corres pond roughly to the DX52D+AS commercial grade and DX54D+AS deepdrawing grade according to the EN10154 specification.