Knowledge of galvanized steel plate

by Zhi shang Metallic material

1, What is the main use of hot galvanized sheet?

A: Hot galvanized sheet is mainly used in construction, home appliances, automobiles, machinery, electronics, light industry and other industries

2. What kinds of galvanizing methods are there in the world at present?

Answer: There are three types of electrogalvanizing, hot-dip galvanizing and coating galvanizing.

3. Which two types of hot dip galvanizing can be divided into according to the different annealing methods?

A: It can be divided into two types of in-line annealing and out-of-line annealing, which are also called protective gas method and flux method.

4. What are the commonly used steel types of hot galvanized sheet?

A: Product categories: General coil (CQ), structural galvanized sheet (HSLA), deep drawing hot galvanized sheet (DDQ), baking and hardening hot galvanized sheet (BH), duplex steel (DP), TRIP steel (Phase change induced plastic steel), etc.

5. What are several forms of galvanized annealing furnace?

A: There are three kinds of vertical, horizontal and vertical annealing furnaces.

6, usually cooling tower cooling ways are several?

A: There are two kinds: air-cooled and water-cooled.

7. What are the main defects of hot dip galvanizing?

A: Mainly: peeling, scratches, passivation spots, zinc particles, thick edge, air knife stripes, air knife scratches, exposed steel, inclusion, mechanical damage, poor steel base performance, wave edge, ladling bend, inappropriate size, embossing, zinc layer thickness, roll printing, etc.

8. Known: the production specification is 0.75×1050mm, and the volume weight is 5 tons. What is the length of the coil steel? (The specific gravity of galvanized sheet is 7.85g/cm3)

Solution: L = G/ (h×b×p) = (5×1000)/(0.785×1.050×7.5) = 808.816m

Answer: The coil is 808.816m long.

9. What are the main causes of zinc layer shedding?

A: The main reasons for zinc layer shedding are: Surface oxidation, silicon compounds, cold bound emulsion is too dirty, NOF section oxidation atmosphere and protective gas dew point is too high, air fuel ratio is unreasonable, hydrogen flow rate is low, furnace aerobic infiltration, strip into the pot temperature is low, RWP section furnace pressure is low and door suction, NOF section furnace temperature is low, Grease evaporation is not enough, zinc pot aluminum content is low, unit speed is too fast, insufficient reduction, zinc liquid residence time is too short, coating thickness.

10. What are the causes of white rust and black spots?

A: Dark spots are formed by further oxidation of white rust. The main causes of white rust are:

Poor passivation, passivation film thickness is not enough or uneven; No oil on the surface or residual water on the strip surface; The surface of the strip contains water when it is rolled up. Passivation not completely dried; Getting wet or rain-soaked during transportation or storage; The storage time of finished products is too long; Galvanized sheet and other acid and alkali and other corrosive media contact or stored together.

11. What is the maximum time for finished products to be stored in the warehouse? Why?

A: It is allowed to store for three months to avoid oxidation caused by too long storage.

12. What is the length tolerance of galvanized steel plate?

A: The length tolerance is not allowed to have negative values, the maximum is not allowed to exceed +6mm.

13, What is big zinc flower? What is a small zinc flower?

Answer: large zinc flower is normal zinc flower, according to the normal production process can produce large zinc flower, its crystal core diameter is not less than 0.2mm; The diameter of the crystalline nucleus less than 0.2mm is called small zinc flower, which is generally not identifiable by the naked eye.

14, the protection principle of hot dip galvanized layer?

A: Because zinc in corrosive environment can form a good corrosion resistance film on the surface. It protects not only the zinc layer itself, but also the steel base.

15. What is the principle of passivation of hot galvanized sheet?

A: Chromate passivation treatment of galvanized sheet can form passivation film, its chemical reaction formula is as follows: Zn+H2GrO4-ZnGrO2=H2

The trivalent chromium in solution passivation group is insoluble in water, and its chemical properties are not active, which plays the skeleton role, while the hexavalent chromium is easily soluble in water, which can play the role of re-passivation when the passivation film scratches, and has the healing effect of passivation film. Therefore, within a certain limit, passivation film can prevent steam or moist air directly erosion galvanized sheet, zinc layer plays a protective role.

16, test the corrosion resistance of hot galvanized sheet which several methods?

A: There are three ways to test the corrosion resistance of hot-galvanized sheet: salt spray test; Wet test; Erosion test.

17. Why should we carry out anti-rust treatment on hot-dip galvanized products?

Answer: When the hot galvanized sheet is in the humid air, especially when the air contains SiO2, CO2, NO2 and NO and other acidic substances, the surface of the galvanized layer will soon produce loose white rust. The main components of white rust are ZnO and Zn (OH) 2. This kind of white rust not only affects the appearance, but also brings great difficulties to the future use.

18. What are the causes of white rust?

Answer: The causes of white rust are: hot dip galvanizing and other acid, alkali, salt and other corrosive media together; Passivation film or anti-film is destroyed; Passivation or oiling effect is not good; The storage warehouse is not well ventilated and damp; Galvanized sheet in the transport of water; Transported at low temperature and stored at high temperature, condensate is formed.

19. How to calculate the coating thickness?

A: The coating thickness formula is: Dz = Gz (Sz*dz), where: Dz -- coating thickness mm, Gz -- per square meter coating weight g, Sz -- coating area mm2, dz -- zinc specific gravity, the above formula can be simplified as: Dz = 0.000139Gz

20. What are the causes of zinc granules?

Answer: The problem of the original board is mainly the cleanliness of the original board and the iron powder content of the original board; Zinc liquid temperature is too high, make the bottom slag float; The solubility of iron is affected by the high content of Al.

21, what is the significance of hot galvanized sheet finishing?

A: With the continuous expansion of the use of hot galvanized sheet, the following purposes can be achieved by polishing the strip steel in the modern continuous hot dip galvanizing unit:

(1) Improve the flatness and flatness of the sheet, but also the surface of the zinc particle flattening, so that the surface of the strip smooth, which is especially advantageous for later deep drawing and other occasions with higher precision;

② The polishing roll used has been pre-shot peening, so the surface of the plating plate has a certain roughness after polishing. It can improve the adhesion of the coating, but also can store a certain amount of grease, in the deep drawing process, the lubrication of the die is beneficial;

③ For the plating plate after painting treatment, although the surface is controlled into small zinc flowers, small zinc flowers can still be exposed through the paint layer. Therefore, for some high requirements of galvanized sheet, small zinc flower surface needs to go through polishing treatment. This can make the galvanized sheet obtain a more uniform silver appearance;

(4) By finishing, the lower yield point can be reduced to make the yield platform disappear or less obvious, which can prevent the slip line in the future drawing or deep drawing, and improve the possibility of deep drawing.