Separation behaviour of zinc dross from hot dip galvanising melts of different aluminium concentrations by alternating magnetic field

Abstract

Dross in zinc pots is the most important factor that impairs the surface quality of hot dip galvanising automobile steel sheet. Separation behaviour of zinc dross from galvanising melts of different Al concentrations (0?12, 4?5 and 55?0 wt-% by an alternating magnetic field has been investigated in order to reduce the dross defects on steel sheets. The properties of different zinc drosses were investigated by means of EDAX and the quantitative metallographic method and the conductivities were measured by physics property measurements system. The experimental results show that the zinc dross in different hot dip galvanising melts has different morphologies, compositions and structures, and the average particle size of the dross increases with the Al concentration. In the case of extra iron (above the solubility limit) in the zinc melt, zinc dross quantity also increases with the Al concentration. All of the three types of zinc dross particles .5 mm can be successfully separated when the magnetic frequency is 17?5 kHz, effective magnetic flux intensity is 0?05 T, imposed time is 15 s and the cross-section of the ceramic square pipe is 565 mm.

The Evaluation on Corrosion Resistance and Dross Formation of Zn–23 wt % Al–0.3 wt % Si–x wt % Mg Alloy

“…In addition, salvaging the dross at regular intervals would cause a loss in efficiency. Dross can usually be removed by applying an external magnetic field or a specific device in the process of galvanizing [8][9][10], but these methods only remove the top or floating dross, it is difficult to deal with the hard and heavy bottom dross [11]. The routine reasons for the formation of bottom dross during the galvanizing process are the high content of Al and the supersaturated iron in zinc pot.…”

Modelling the Electromagnetic Separation of Non-metallic Particles from Liquid Metal Flowing through a Two-stage Multichannel

“…Laboratory-scale experiments have demonstrated successfully the separation of (i) non-metallic inclusions (Al 2 O 3 4) or SiC 5) ) from Al melt, (ii) Fe-rich phase from hypoeutectic Al-Si alloys, 3,6) primary Si particles from hypereutectic Al-Si alloys, 7) and Fe-Al-Zn dross from galvanizing Zn melt, 8,9) where a single straightpass circular or square separator with a uniform cross-section are commonly used. For industrial applications, the feasibility of using a bundle of small channels for inclusion removal has also been investigated.…”