What Is Galvanized Steel Coil?

For galvanized coils, immerse the thin steel plate in the molten zinc bath, and adhere a layer of zinc thin steel plate to the surface. At present, it is mainly produced by the continuous galvanizing process, that is, the coiled steel sheet is continuously immersed in a zinc plating bath with molten zinc to make a galvanized steel sheet; an alloyed galvanized steel sheet. This steel sheet is also manufactured by the hot-dip method, but immediately after it is out of the tank, it is heated to about 500 ° C to form an alloy coating of zinc and iron. This galvanized coil has good paint adhesion and weldability.

ll

Galvanized coil

(1) The classification and code of the performance level are in accordance with the requirements in Table 1.

Table 1 Classification and code of performance

Level performance level code scope

General purpose 01

Mechanical bite 02 Zinc layer weight code should not exceed Z350

Stamping 03 thickness range 0.4mm zinc layer weight does not exceed Z275

Deep punch 04

Special Calm Steel Deep Drawing 05

No aging ultra deep punch 06

Structures 220, 250, 280, 320, 350, 400, 450, 550 Plates with a thickness of <0.4mm are not suitable for 220, 250, 280 and 320 grades

(2) The type and code of the substrate are as specified in Table 2.

Table 2 Types and codes of substrates

Substrate type code

(1) Normal

Mainly: shedding, scratches, passivation spots, zinc particles, thick edges, air knife streaks, air knife scratches, exposed steel, inclusions, mechanical damage, poor steel-based performance, wave edges, curl, mismatched sizes, Embossing, uneven zinc layer thickness, roll printing, etc.

The main reasons for the zinc layer to fall off are: surface oxidation, silicon compounds, cold rolled emulsion is too dirty, the NOF stage oxidation atmosphere and protective gas dew point are too high, the air-fuel ratio is unreasonable, the hydrogen flow is low, the furnace has oxygen infiltration, strip The temperature of entering the pot is too low, the pressure of the RWP section is low and the furnace door sucks air, the temperature of the NOF section is low, the oil is not evaporated, the aluminum content of the zinc pot is too low, the unit speed is too fast, the reduction is insufficient, and the zinc stays The time is too short and the coating is too thick.

The causes of white rust and black spots are: Black 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 there is residual moisture on the surface of the strip;

(3) The strip surface contains moisture during coiling;

(4) The passivation is not completely dried;

(5) Moisture or rain during transportation or storage;

(6) The storage time of the finished product is too long;

(7) Galvanized sheet is in contact with or stored with other corrosive media such as acid and alkali.

The finished product is allowed to be stored in the warehouse for a maximum of three months to avoid oxidation caused by long storage.