FAQ About Hot-dip Galvanized Sheet(一)

1. What is the main application of hot-dip galvanized sheet?

 

Answer: Hot-dip galvanized sheets are mainly used in construction, home appliances, automobiles, machinery, electronics, light industry and other industries.

 

2. What types of galvanizing methods are there in the world?

 

Answer: There are three methods of electro-galvanizing, hot-dip galvanizing and galvanizing.

 

3. What are the two types of hot-dip galvanizing according to the different annealing methods?

 

Answer: It can be divided into two types: in-line annealing and off-line annealing, which are also called shielding gas method and flux method.

 

4. What are the commonly used steel types for hot-dip galvanized sheets?

 

Answer: Product category: General commodity roll (CQ), structural galvanized sheet (HSLA), deep-drawing hot-dip galvanized sheet (DDQ), bake-hardened hot-dip galvanized sheet (BH), duplex steel (DP), TRIP steel (transformation induced plasticity steel), etc.

 

5. What types of galvanizing annealing furnaces are there?

 

Answer: There are three types: vertical annealing furnace, horizontal annealing furnace and vertical and horizontal annealing furnace.

 

6. How many cooling methods are usually used in cooling towers?

 

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

 

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

 

Answer: Mainly include: shedding, scratches, passivation spots, zinc particles, thick edges, air knife streaks, air knife scratches, exposed steel, inclusions, mechanical damage, poor performance of steel base, wavy edges, ladle warps, dimensions Inconsistency, embossing, inconsistency in zinc layer thickness, roll printing, etc.

 

8. It is known: the production specification is 0.75×1050mm, and the coil weight is 5 tons. What is the length of the coil? (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 strip steel coil is 808.816m long.

 

9. What are the main reasons for the peeling off of the zinc layer?

 

Answer: The main reasons for the peeling of the zinc layer are: surface oxidation, silicon compounds, too dirty cold-rolled emulsion, too high dew point of NOF section oxidation atmosphere and protective gas, unreasonable air-fuel ratio, low hydrogen flow rate, and aerobic infiltration of the furnace. The temperature of the strip steel entering the pot is low, the furnace pressure in the RWP section is low and the furnace door sucks air, the furnace temperature in the NOF section is low, the oil evaporates endlessly, the aluminum content in the zinc pot is low, the unit speed is too fast, the reduction is insufficient, and the zinc liquid The residence time in medium is too short and the coating is too thick.

 

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

 

Answer: Black spots are formed by further oxidation of white rust. The main causes of white rust are:

 

Poor passivation, insufficient or uneven passivation film thickness; no oil on the surface or residual moisture on the strip surface; moisture on the strip surface during coiling; incomplete drying of passivation; damp or rain during transportation or storage ; The finished product is stored for too long; the galvanized sheet is in contact with or stored together with other corrosive media such as acid and alkali.

Hot Dip Galvanized Steel Sheet