Influence of Fe on Cr content in Al-Zn-Mg-Si molten bath

Dissolution experiments of Cr and Fe in 55%Al-Zn-2%Mg-1.6%Si molten bath were carried out in the zinc pot of a hot-dip galvanizing process simulator to study the influence of Fe on the Cr content in the molten bath. With a continuous addition of Al-10Cr master alloy ingot, the Cr content of the alloy bath reached a saturated content of 0.15% when the bath temperature was 630℃. Above its saturated solubility, bottom dross with the main component of Al-Cr will be formed. When enough steel sheet was added to the Cr-saturated molten bath, the saturated Fe content of the bath reached approximately 0.53%, while the Cr content decreased significantly from 0.15% to 0.026%. Al-(Fe, Cr)-Si intermetallic compounds with relatively high content of Cr, Fe and Si were formed in the bath, precipitated as bottom dross. The calculation results of the phase diagram further confirm that increasing Fe content of 55%Al-Zn-2%Mg-1.6%Si molten bath significantly reduces the saturated solubility of Cr in the alloy bath, resulting in the precipitation of Cr to form bottom dross.