Study of application of rare earth elements in advanced low alloy steels

Effect of rare earth elements on modification of inclusions, deep purifying, refinement of grain size and micro-alloy function in advanced low-alloy steels have been investigated with metalloscopy, XRD, SEM, EDS and IMMA. The dissolved rare earths were appeared in the grain boundary better than into the grain, and the grain boundary was cleaned by a trace of the dissolved RE. Precipitation phases-Nb(C, N), (Nb, Ti) (C, N) are fine dispersed promptly by the dissolved rare earths. The strength and toughness of the advanced low-alloying steels are improved finally. The results of the inner rust layer in the weather resisting steels show that rare earth elements is enriched in the interface between the rust layer and the steel substance, which result in that Si4+, P5+ and Cu+ are moved into the inner rust layer. As a result, a dense composite rust layer containing Si4+, P5+, Cu+ and RE3+ is formed, and the property of the corrosion resisting of weather resisting steels is improved by rare earth elements. (c) 2007 Published by Elsevier B.V.