Enrichment of Cu,Ni in Surface Oxidation Layer of Copper-Bearing Age-Hardening Steel

Enrichment of Cu,Ni in surface oxidation layer of copper-bearing age-hardening steel was investigated. The results showed that copper enriched liquid phase is formed at reheating temperature of 1100~1200 ℃, and the liquid Cu enriched phase is penetrated along austenite grain boundary leading to surface cracking. But copper enriched liquid phase is not formed at reheating temperature of 1000 ℃ and 1300 ℃. The structure of copper-rich phase in scale is changed by addition of nickel, and Ni-Cu enriched phase is stayed in oxidized layer in form of granular particle which inhibits copper enriched phase from penetration into the base metal.