How much do you know about galvanized coil?
Galvanized coils are made by placing thin steel sheets into a molten zinc bath vessel, which causes a layer of zinc to adhere to the surface of the thin steel sheet. Currently, the main method is the continuous galvanizing process, in which rolls of steel are continuously soaked in a molten zinc bath vessel to make galvanized steel; alloyed galvanized steel. This type of steel is also manufactured by the hot dipping method, except that it is heated to about 500°C immediately after leaving the bath to produce an alloy coating of zinc and iron. This galvanized coil has excellent paint adhesion and weldability.
The advantages of galvanized coils are as follows: Very strong corrosion resistance. It prevents corrosion of the steel surface and extends the service life of the galvanized coil. And galvanized coils look clean and beautiful, adding to the decorative nature.
What do you know about galvanized coil?
Some advantages: strong surface resistance to oxidation and corrosion, which can strengthen the rust penetration resistance of other parts.
Galvanized coils are mainly used in air conditioners, refrigerators, automobiles and other industries.
As an example, the back panel of the indoor unit of an air conditioner, the back panel of a cabinet unit, and the housing and interior of an outdoor unit are made of galvanized sheet. The working environment of these parts is subject to strong oxidation conditions such as rain, sunlight and gas corrosion, so galvanized coils are often chosen as the main raw material.
Hot-dip galvanizing general knowledge
I. Classification of hot-dip galvanizing
Hot-dip galvanized coil is produced from hot-rolled steel strip or cold-rolled steel strip as a substrate by successive hot-dip galvanizing technology. Hot-dip galvanized sheets are supplied in rectangular flat sheets by cross-cutting; hot-dip galvanized coils are supplied in rolls by coiling, so they can be divided into hot-rolled galvanized coils and cold-rolled hot-dip galvanized coils, which are mainly used in construction, home appliances, cars, containers, transportation and home industry. In particular, steel construction, car production, steel silo production and other industries.
They are characterized by strong corrosion resistance, beautiful appearance and good quality, and are conducive to deep processing and economical and practical.
Second, commodity specifications, trademarks, classification; technical specifications, functions and raw materials, etc.
* Example of symbols: zinc layer weight 140g/m2, function JY, exterior structure Z, exterior treatment Y, dimensional accuracy B, size 1.0*1250*C.
The symbol is: 140-JY-Z-Y-B-1.0*1250*C-Q/BB114-2002
(1) Baosteel hot-dip galvanized part
Produced with cold-rolled or hot-rolled steel successively dipped in zinc for usual use or structural use. The usual scope of supply of hot-dip galvanized.
Thickness (0.3-3.5) Width (800-1830) Length (plate 1000-6000, roll inner diameter 610) Unit mm.
(2) Galvanized part of this steel
Bensteel galvanized are cold-rolled substrate galvanized. The primary trademarks of BenSteel galvanized are ST01Z, ST02Z, deep-drawn, ST03Z, and ST04Z.
(3) Taiwan Yehui galvanized part
Taiwan Yehui galvanized, can be divided into cold-rolled substrate galvanized (SGCC), hot-rolled substrate galvanized (SGHC).
(4) South Korea POSCO hot-rolled galvanized coils
Now the company is doing two kinds of galvanized cold-rolled substrate and galvanized hot-rolled substrate. The quality is stable and the market response is outstanding.
Easy to present quality problems: white rust. Others are basically not.
Uses: Widely used in cars, home appliances, computers and audio materials. Another big use is when secondary electro-galvanization is used – Guangzhou mall.
Easy to present quality problems: uneven thickness.
(5) Indian galvanized coil
India National Factory, India TATA, India SHREE, India Pushan, India Udon
Thickness below 0.5MM, function and appearance: small zinc bloom (National Factory, India TATA), no zinc bloom (SHREE), appearance usually unpassivated, lightly oiled. Piece weight at 5 tons, zinc coating at 120g on both sides.
Use: Ventilation ducts and chimneys in northern malls, as color coated substrates.
Easy to present quality problems: white rust, volume deformation – can not be on the machine, demolition and bending up marks (not through the length of the flattening, the appearance is not through the finishing).
Defects of galvanized rolls
Mainly: shedding, scratches, passivation spots, zinc grains, thick edge, air knife strip marks, air knife scratch marks, exposed steel, inclusions, mechanical damage, poor steel base performance, wavy edge, scoop bend, size discrepancies, embossing, zinc layer thickness discrepancies, roll marks, etc.
The main reasons for zinc layer shedding are: surface oxidation, silicon compounds, too dirty cold tie emulsion, too high NOF section oxidizing atmosphere and protective gas dew point, unreasonable air-fuel ratio, low hydrogen flow, oxygen infiltration in the furnace, low temperature of strip steel in the pot, low furnace pressure in RWP section and air absorption in the furnace door, low furnace temperature in NOF section, etc.
White rust is produced mainly due to the following reasons.
(1) poor passivation, passivation film thickness is not enough;
(2) The surface of the galvanized coil is not oiled or there is residual moisture on the surface of the strip;
(3) The surface of the strip contains moisture when it is rolled;
(4) passivation is not completely dried;
(5) damp or rain during transportation or storage;
(6) The finished product is stored for too long;
(7) Galvanized sheets are in contact with other corrosive media such as acids and bases or stored together.
Finished products are allowed to be stored in the warehouse for a maximum of three months to avoid oxidation from excessive storage.
Plating Definition
(1)Normal zinc spangle coating
Zinc layer in the normal solidification process, the zinc grain free to grow into the shape of the obvious zinc flower coating.
(2)Minimized spangle coating
A zinc layer in which the zinc grains are artificially restricted during solidification to form the smallest possible zinc spangle coating.
(3)spangle-free coating
A coating layer with no visually visible zinc bloom and a uniform surface, obtained by adjusting the chemical composition of the plating solution.
(4)Zinc-iron alloy coating
This coating has a dull gray appearance, no metallic luster, and is easily chalked during the intense forming process, and is suitable for coating that can be painted directly without further treatment except for general cleaning.
(5)Differential coating
A coating that requires a different weight of zinc on both sides of a galvanized steel sheet.
(6)Skin pass
Skin pass is a cold rolling process with a small amount of deformation of galvanized steel for one or more of the following purposes.
Improving the surface appearance of galvanized steel or making it suitable for decorative coating; minimizing slip lines (Lüders lines) or folds that occur when the finished product does not see processing, etc.