1974 Volume 60 Issue 1 Pages 104-107
As the aluminium in galvanizing bath is consumed through the reaction of dross and the alloy-layer formation, it is usually difficult to keep the aluminium content in the bath at a predetermined value. On the basis of our recent results, the aluminium content in tailored zinc required to keep the aluminium content in the bath at a desired level has been calculated.
The aluminium content in tailored zinc (yT) can be expreessd as the sum of the aluminium concentration in liquid zinc (y) and the amount of aluminium consumed, in concentration, through dross and alloy- layer formations:
where w is coating weight of sheet, and ΔW1 and ΔW2 are iron dissolved and iron in alloy layer, respectively.
Under conditions of sheet temperature of 470°C, line speed of 100m/min and coating weight of 305g/m2-sheet, the aluminium content in tailored zinc is estimated to be 0.31% to maintain the bath at 0.14% Al. When the coating weight is in the range of 305±60g/m2, to increase the aluminium content in the bath by 0.01% the aluminium content in tailored zinc should be increased by 0.05-0.08% under the operational condition of 0.10-014% Al in the bath.