Effects of Al and Ni on copper-rich phases in the scale/steel interface after high-temperature oxidation of copper-containing steel

摘要

A study was conducted on the formation of a Cu-rich phase at the scale/steel interface of Cu-containing steel by high-temperature oxidation with varying amounts of Al and Ni.Both Al and Ni were found to help decrease the amount of the Cu-rich phase at the interface.Analysis of the effects by these elements was conducted in terms of the melting point of the Cu-rich phase, the solid solubility of Cu in austenite, the rate of oxidation, and the amount of Cu-rich phase occlusions in scales.Because of selective oxidation, in which Al and Ni are oxidized more and less preferentially than Fe, respectively,Al was weakly concentrated at the interface whereas Ni was more heavily concentrated in it.Thus,Al exerted no effect on the melting point of the Cu-rich phase,whereas Ni raised its melting point.Al,which was applied at contents of less than 2.0%, decreased the solubility of Cu in austenite but this effect weakened at the interface during oxidation. By contrast,Ni increased the solubility of Cu,and this effect was strengthened with oxidation.Both Al and Ni promoted internal oxidation and the formation of occlusions.