Abstract
Effects of niobium addition on strengthening, hydrogen absorption and hydrogen embrittlement have been investigated paying attentions to carbides morphologies by using laboratory melted clean steels. Addition of niobium and austenitizing at high temperature enhanced temper softening resistance due to fine niobium carbide precipitation during subsequent tempering. Addition of both niobium and vanadium improved temper softening resistance furthermore. High niobium steel absorbed less hydrogen in corrosive media than high vanadium steel. It would attribute to small size and incoherency of niobium carbide. High niobium steel showed good resistance to hydrogen embrittlement. It would be due to both uniform dispersion of cementite by high temperature tempering and low hydrogen absorption.
