Summary for fluctuating dross Discussion
The fluctuating dross in a bath question appears to be about hot-dip galvanizing, but the provided thread excerpt does not include the actual discussion or any answers. The only visible content is a promotional line for suggested galvanizing books, including "Faults in Hot-Dip Galvanizing" by Dietrich Horstmann. Because no technical advice, causes, or corrective actions are shown in the excerpt, there is no reliable basis to summarize a solution or attribute recommendations to any answerer. The page likely belongs to a larger Q&A archive entry about reducing dross formation or variation in a galvanizing bath, but the excerpt alone does not reveal the practical guidance given in the thread.
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Our time for removing of a bottom Zn dross was a 25-30days, but in the past one month the time of removing the bottom dross is reduced to 8-10 days. Why?
We don’t have a chem.treatment on Galv.line and 5 Stands Mill.
The temperature of the bath is 455-465 °C.
%of Al is 0.16-0.19 and Fe 0.03-0.04%.
After 8-10 days our Galv. strip is cover with a bubbles or spots from the dross only from a one side of a strip and that side is the one which is in touch with bottom roll in Zn bath.
The roll is with spiral grinding lines from the center to the end.
What we should do to reduce the fluctuated dross in a bath?
Zarko Ivanovski
Mittal Steel Skopje – Skopje, Macedonia
2006
A. Sir:
I can only speak from a general galvanizing point of view. Your iron of 0.03 to 0.04% is normal to me. The aluminum I have no experience for your sheet line. In general galvanizing the normal (good) dross amount is about 0.5% of steel galvanized. In a new steel (nearly pure iron) kettle there is much less dross for the first three months of production then normal dross amount is experienced. Temperature of the DROSS and the tool used for drossing are very important. Most general galvanizers find a clam difficult to use to get a good result. Using the correct temperature can give 1/3 less dross. Recently at a general (steel) kettle containing 30,000 pounds of dross only 4,000 pounds were removed using a clam. If the dross is not properly removed in a steel kettle, overheat in the dross zone can result causing a burn-though. I hope this response is of use.
Regards,
Dr. Thomas H. Cook
Galvanizing Consultant – Hot Springs, South Dakota, USA
A. Dear Zarko:
Have you asked for assistance from other galvanizers from within Mittal Steel or from anyone expert here at R&D USA?
Please e-email if you have not and wish to do so, and we can have a teleconference to discuss details of your operation and potential causes and solution to your dross problem. (I could not find your name in our Global Address directory but I know that it is not yet very complete, and does not include all Mittal Steel operations)
Regards,
Stavros Fountoulakis
– East Chicago, Indiana
Q. I would like to know what kind of measures can be taken to reduce the dross amount on the molten Zinc bath and Zinc in it.
Süleyman BEÞLÝ
Süleyman BEÞL
ÖZYAÞAR A.Þ – Istanbul, TURKEY
2007
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