HiTo Engineering assists Bangladesh customer in upgrading the technology of their coils continuous hot dip galvalume line

Several months ago,Bangladesh customer found their coils continuous hot dip galvalume line could not produce good quality galvanized coils , the problem is : there always had raised zinc particles or zinc scars on steel strips.

Their engineer  had inspected the annealing furnace,furnace nose and zinc pot,then found the furnace nose's internal excessive slagging/zinc accumulation leads to channel blockage. So customer asked HiTo Engineering for technical solutions.

Excessive internal slagging/zinc accumulation in the furnace nose, which causes channel blockage, can be primarily attributed to three core factors: abnormal zinc bath composition, temperature control failure, and poor sealing. The details are as follows:

1. Imbalanced zinc bath composition: A too-low aluminum content in the zinc pot (failing to effectively inhibit dross formation) or an excessively high iron content (iron elements on the steel strip surface dissolve into the zinc bath, forming Fe-Zn alloy dross) will lead to the generation of a large amount of floating dross/bottom dross. This dross flows into the furnace nose with the zinc bath, deposits, and gradually forms slag buildup.
2. Unstable temperature control: Excessive temperature fluctuations inside the furnace nose or in the zinc pot, or local temperature being too low (below the zinc bath's melting point or optimal flow temperature), will reduce the fluidity of the zinc bath. It then tends to condense on the inner wall of the furnace nose and the flow guide structure, resulting in zinc accumulation. Sudden temperature drops may also cause zinc dross to precipitate and adhere rapidly.
3. Failure of furnace nose sealing and inert gas protection: Aging gaskets, air leakage at joints, insufficient purity or flow of inert gas (e.g., nitrogen) will allow air to enter the furnace nose. This causes the zinc bath to oxidize and form zinc oxide dross; meanwhile, the steel strip surface may also undergo secondary oxidation. The oxidized scale mixes into the zinc bath, worsening slag formation, and the combined effect leads to channel blockage.
4. Production rhythm and operational factors: Frequent starts and stops of the production line (discontinuous production) cause the zinc bath inside the furnace nose to repeatedly cool and heat up, increasing the probability of zinc accumulation. Additionally, wear or installation deviations of components such as the flow guide plates and dross baffles inside the furnace nose will also lead to poor zinc bath flow, promoting the deposition of dross and zinc.

HiTo Engineering suggested customer to change a furnace nose.A good furnace nose need to satisfied four points :

1. Good quality.

2. Precise sealing,.

3. Smooth flow guidance.

4. Stable temperature control .

HiTo Engineering offers furnace nose and  installation guidance to customer. Currently, the temperature inside the furnace nose can be controlled within the range of 300-600℃, and its sealing is intact with no leakage. The galvanized coils produced are of high quality and stable in performance, which has satisfied the customers.