Effect of Si content in the zinc-aluminium bath on the formation of slag phase

Abstract

The solubility of silicon in a Zn-50%Al-xFe-ySi(in atomic fraction) molten bath and the content of silicon in a Zn-30%Al-2%Fe-xSi(in mass fraction) molten bath corresponding to the appearing of τ5 slag phase and the disappearing of FeAl3 phase were calculated at different temperatures using the Thermo-Calc software. At the same time,the solubility of silicon in liquid phase in the Zn-50%Al-xFe-ySi alloy and the phase equilibrium relationship of the Zn-30%Al-2%Fe-xSi alloy were experimentally determined by using the equilibrium alloy method. The results show that the calculated solubility of silicon in liquid phase in the Zn-50%Al-xFe-ySi system at 540,560,580,600 and 620℃ are 0.82%,0.95%,1.11%,1.28% and 1.47%,respectively,which agree well with the experimental data. When the temperature of the molten bath is 580,600,and 620℃,the calculated content of silicon in the Zn-30%Al-2%Fe-xSi alloy corresponding to the appearing of τ5 phase in the molten bath is 0.6%,0.72% and 0.84%,and the values corresponding to the disappearing of FeAl3 phase are 1.12%,1.22% and 1.34%,respectively,which agree basically with the experimental results.

Keywords

• hot dip galvanizing
• silicon content
• thermodynamic calculations
• slag