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

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.

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.

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

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.

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.

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.

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.

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 coil is 808.816m long.

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.

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

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

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.

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.

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

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

Specification and thickness of galvanized sheet

The thickness of ordinary galvanized sheet is 0.4~2.0.

Generally, it is not produced by large steel mills of state-owned enterprises, but by small steel mills of private enterprises. Conventional specifications are 0.35, 0.30, 0.28, 0.25, the thinest is generally 0.1, more than 2.0mm, because straightening is very difficult, the price above 2.0 will increase with the increase of thickness.

There are two kinds of galvanized sheet: hot galvanized sheet and electrogalvanized sheet. The national standards of these two kinds of galvanized sheets are briefly introduced.

According to GB/T 2518-2008, the thickness range of hot galvanized sheet is 0.3 ~ 5.0 mm

According to GB/T 15675-2008 "Continuous electric galvanized, zinc-nickel alloy coated steel plate and steel strip", its plate thickness is not specified. But according to GB/T 708-2006 "cold rolled steel plate and strip size, shape, weight and allowable deviation", galvanized sheet thickness is 0.40 ~ 4.00 mm

What kind of materials are used in different kinds of galvanized steel?

1. hot dip galvanized steel plate. The sheet steel is dipped into the melted zinc tank so that the surface is adhered to a zinc sheet steel. At present, continuous galvanizing process is mainly used to produce, that is, continuous immersion of rolled steel plate in the melting of zinc in the plating tank to make galvanized steel plate;

2. alloyed galvanized steel plate. This steel plate is also made by hot dipping, but immediately after it is out of the groove, it is heated to about 500℃ to create an alloy coating of zinc and iron. This galvanized sheet has good coating tightness and weldability;

3. electric galvanized steel plate. The galvanized steel plate made by electroplating has good workability. But the coating is thin, corrosion resistance is not as good as hot dip galvanized sheet;

4. single-side plating and double-side difference galvanized steel plate. Single-sided galvanized steel plate, that is, galvanized products only on one side. It has better adaptability than double-sided galvanized sheet in welding, coating, rust prevention and processing. In order to overcome the shortcomings of single side without zinc coating, there is a galvanized sheet coated with a thin layer of zinc on the other side, namely double-sided differential galvanized sheet;

5. alloy, composite galvanized steel plate. It is made of zinc and other metals such as lead, zinc alloy or composite plating of steel plate. This kind of steel plate not only has excellent anti-rust performance, but also has good coating performance.

What is H-shaped steel

H section steel is a new type of economical building steel. It is an economic cross-section steel with good mechanical properties, which is optimized and developed for I-beam steel. It is named because its section is the same as the English letter "H".

The main features are as follows:

1. high structural strength: compared with I-steel section modulus is large, under the same bearing conditions can save metal 10-15%.

2. Flexible and rich design style: in the case of the same beam height, the steel structure can be 50% larger than the concrete structure, so that the building layout is more flexible.

3. high structural stability: the steel structure is dominated by hot rolled H-beam steel, scientific and reasonable structure, good plasticity and flexibility, high structural stability. Especially suitable for some earthquake prone areas of the building structure.

4. increase the effective use area: compared with concrete structure, steel structure column cross-sectional area is small, can increase the effective use area of the building. Depending on the building form, the effective use area can be increased by 4-6%.

5. easy processing: easy structural connection and installation, but also easy to disassemble and reuse.

6. High degree of industrial production: The steel structure based on hot rolled H beam has a high degree of industrial production, which is convenient for mechanical manufacturing, intensive production, high precision, convenient installation and easy quality assurance. You can build real house manufacturing plants, bridge manufacturing plants, industrial plants, manufacturing plants, etc.

7. the construction speed is fast: covers an area of small, suitable for all-weather construction, the influence of climate conditions is small. The construction speed of hot rolled H-beam steel structure is about 2-3 times that of concrete structure, and the capital turnover rate is doubled, which reduces the financial cost and saves investment.

Galvanizing  is the process of adding a layer of zinc to the outer surface of a metal. The idea is to add a protective coating to the underlying metal, reducing the likelihood of corrosion or rust.

Galvanizing process varies with specific technology. However, the most important part of the process is that it usually involves enclosing steel or iron in zinc, which may be in a liquid or dust-like state. When zinc is introduced, the iron in the surrounding metal reacts with the zinc to form a tightly bonded alloy coating.