Frequently Asked Questions about Galvanized Steel Coil

For galvanized coils, the thin steel sheet is immersed in a molten zinc bath to make a thin sheet of zinc adhered to its surface. It is mainly produced by continuous galvanizing process, that is, the rolled steel plate is continuously immersed in a plating tank with molten zinc to make galvanized steel plate; alloyed galvanized steel plate. This kind of steel plate is also produced by hot dip method, but immediately after it is out of the tank, it is heated to about 500 ℃ to form an alloy film of zinc and iron. This galvanized coil has good paint adhesion and weldability.

Mainly include: falling off, scratches, passivation spots, zinc particles, thick edges, air knife streaks, air knife scratches, exposed steel, inclusions, mechanical damage, poor performance of steel base, wave edges, buckling, size mismatch, Imprinting, inconsistent thickness of zinc layer, roll printing, etc.
The main reasons for the peeling of the zinc layer are: surface oxidation, silicon compounds, cold rolling emulsion too dirty, NOF section oxidizing atmosphere and protective gas dew point too high, unreasonable air-fuel ratio, low hydrogen flow, furnace oxygen infiltration, strip steel The temperature of entering the pot is too low, the furnace pressure in the RWP section is too low, the furnace door suction is too low, the furnace temperature in the NOF section is too low, the grease is not evaporated completely, the aluminum content of the zinc pot is too low, the unit speed is too fast, the reduction is insufficient, and the zinc solution stays in the liquid. The time is too short and the coating is too thick.

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