Tianjin Tianyingtai Steel Pipe Co., Ltd. is one of the most credible manufacturers and suppliers of galvanized steel coil cold rolled material for roofing in China. Welcome to consult the quotation and import cheap galvanized steel coil cold rolled material for roofing made in China here from our factory.
Product Introduction
The galvanized coil is immersed in a molten zinc bath to adhere a zinc-plated steel sheet to the surface. At present, it is mainly produced by a continuous galvanizing process, that is, a coiled steel sheet is continuously immersed in a zinc-plated plating tank to form a galvanized steel sheet; an alloyed galvanized steel sheet. This steel sheet is also produced by hot dip, but immediately after it is taken out, it is heated to about 500 ° C to form an alloy coating of zinc and iron. This galvanized roll has good adhesion and weldability of the coating.
Defects and possible problems
Mainly: shedding, scratching, passivation spots, zinc particles, thick edges, air knife streaks, air knife scratches, exposed steel, inclusions, mechanical damage, poor steel-based performance, wave edge, buckling, size difference, Embossing, zinc layer thickness, roll printing, etc.
The main causes of zinc layer detachment are: surface oxidation, silicon compound, cold emulsified emulsion is too dirty, NOF oxidizing atmosphere and protective gas dew point is too high, air-fuel ratio is unreasonable, hydrogen flow rate is low, furnace aerobic infiltration, strip steel The temperature of the boiling pot is low, the pressure of the RWP section is low, the suction of the furnace door is low, the temperature of the NOF section is low, the oil is not evaporated, the aluminum content of the zinc pot is low, the speed of the unit is too fast, the reduction is insufficient, and the zinc liquid stays. The time is too short and the plating is too thick.
White rust and black spots are caused by the fact that dark spots are formed by further oxidation of white rust.
The main causes of white rust are:
(1) Poor passivation, insufficient or uneven passivation film thickness;
(2) The surface is not oiled or the residual moisture on the strip surface;
(3) The surface of the strip contains moisture when coiling;
(4) Passivation is not completely dried;
(5) getting wet or rainy during transportation or storage;
(6) The finished product storage time is too long;
(7) The galvanized sheet is in contact with or stored together with other corrosive media such as acid and alkali.
The finished product is allowed to store for up to three months in the library to avoid excessive oxidation for storage.
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