Every things about hot dip galvanized steel coil
This article is written for those who want to know about galvanized steel coils and are considering purchasing product from China.
1. What is hot dip galvanized steel coil?
Galvanized steel is a type of steel that has a layer of zinc on its surface for corrosion protection. There are several methods to produce galvanized steel, with hot-dip galvanizing being one of the most commonly used. This involves dipping a thin, cold-rolled steel sheet into a molten zinc pot, resulting in a steel sheet coated with a layer of zinc.
The galvanized steel sheet is typically delivered in the form of a coil from the factory, and may be referred to as a GI coil or HDG coil.
2. Parameters of hot dip galvanized steel coil
When inquiring or ordering galvanized steel from the factory, it is necessary to know and provide certain parameters.
2.1 Thickness
The thickness of a galvanized steel sheet is determined by the combined thickness of the cold-rolled steel and the zinc layer, with the cold-rolled steel being the main contributor to the overall thickness.
TCT and BMT
Typically, the thickness of galvanized steel sheets ranges from 0.12 mm to 3.0 mm. Thinner sheets are more expensive as they require more time and coating per ton of steel during production.
2.2 Width
The standard widths for galvanized steel sheets are 914mm (3 feet), 1000mm, 1219mm (4 feet), and 1250mm.
The most common stock specifications for galvanized steel range in thickness from 0.25mm to 3.0mm, with regular widths of 1219mm and 1250mm. Sizes of 914mm and 1500mm are less common.
Customized sizes can range from 600mm to 1500mm.
2.3 Zinc coated quantity
The weight of zinc per square meter is used to measure the thickness of the zinc layer, with the unit of measurement being grams per square meter (g/㎡).
A thicker zinc layer provides better antirust protection. Zinc coatings ranging from 20g to 450g per square meter can be produced.
Zinc coatings of 40g to 275g are popular, and we suggest a 60g zinc coating for regular use.
2.4 Base steel sheet (raw materials)
Cold rolled steel is commonly used as the raw material for producing galvanized steel.
There are different grades of cold rolled steel including common grade, draw grade, deep draw grade, and structural grade.
In the European standard, DX51 is considered a common grade, while DX52 and DX53 are classified as deep drawing grades.
In the JIS standard, SGCC is a common grade, while SGCD is a deep drawing grade.
Similarly, in the ASTM standard, CS is a common grade, while FS is a deep drawing grade.
For more information on the comparison of galvanized steel standards, please click here.
2.5 Spangle
Hot-dip galvanizing can create spangle on the surface of steel sheets. However, the addition of inhibitors can result in the production of zero spangle galvanized steel.
There are also options for mini spangle and big spangle. Zero spangle offers the highest level of rust resistance. Customers can select their preferred galvanized steel spangle based on personal preference.
2.6 Weight
How many tons of each coil？
It can produce as customer requests, usually 4-6 tons.
How many tons can be loaded in 1 container?
Usually, loading 25 tons in a 20 feet container.
2.7 Surface treatment
Passivation and oiling are not required for customized galvanized steel, but they may be added as optional finishes.
Environmental passivation
Trivalent chromium passivation and chromium-free passivation are environmentally friendly.
Non-environmental passivation
Hexavalent chromium passivated surfaces can not come into direct contact with food.
Oiled
The coil with oil performs better of anti-corrosion, but you may need special equipment to deoil the coil.
2.8 Further processing for hot dip galvanized steel coils
Hot dip galvanized steel coils can cutting to flat plate, strips, and press to checkered plate.
3. FAQ about purchasing galvanized steel coil from China
3.1 Why choose of hot dip galvanized steel？
Steel is prone to rusting, but hot-dip galvanized steel can prevent rust and is much more cost-effective compared to stainless steel.
3.2 Whats is the different between hot galvnized steel and cold galvnized steel?
Hot-dip galvanizing involves immersing steel into a bath of molten zinc, resulting in a zinc coating.
In contrast, cold galvanizing involves electroplating steel with a layer of zinc.
Hot-dip galvanized steel typically has a thicker zinc coating, which provides superior anti-corrosion properties. However, cold galvanized steel is easier to machine.
3.3 What is different between galvanized steel, galvalume steel and SuperDyma?
Galvanized steel is steel that has been coated with a layer of zinc.
Galvalume steel, on the other hand, is coated with a mixture of 55% aluminum and zinc (Al-Zn). This coating provides better anti-corrosion properties compared to galvanized steel, but it is not suitable for cutting.
SuperDyma is a type of steel that has magnesium added to the zinc coating, which further improves its anti-corrosion performance.
3.4 How many meters of each ton galvanized steel coil?
A galvanized steel sheet consists of iron with a coating of zinc. The density of iron is 7.874 g/cm³, while the density of zinc is 7.14 g/cm³. Using the following formula, we can estimate their combined density:,
Length(m)=127.4/(thickness(mm)*width(m))
or use the calculation tool
3.5 How to find the price of galvanized steel coils?
The price of galvanized steel is subject to daily fluctuations due to changes in the cost of its raw materials. The primary costs involved in producing galvanized steel sheets are cold-rolled steel sheets, zinc, and processing time.
Cold-rolled steel is produced from hot-rolled steel, and its real-time price can be checked in the futures market.
The price of galvanized steel is determined by its weight, with thinner sheets and higher zinc coating resulting in a higher unit price.
3.6 Minimum order quantity（MOQ) of galvanized steel coils
Most factories require a minimum order quantity (MOQ) of 25 tons per size. This facilitates the handling of raw materials and saves time when switching between specifications. Typically, a 20-foot container can carry 25 tons.
3.7 Hot-dip galvanized steel coil in stock
Galvanized steel is commonly stocked in a range of thicknesses, from 0.25 to 3.0mm, and regular widths of 1000, 1219, and 1250mm. However, there are fewer options available in the 914mm and 1500mm sizes. Zinc coating options typically range from 40 to 275g/m2, and can come in regular spangle or zero spangle varieties.
Our minimum order quantity (MOQ) is 1 coil, with each coil weighing approximately 4-6 tons.
3.8 Hot dip galvanized steel coil standard
| GB/T2518 | JIS G3302 | EN 10142/10143 | ASTM A653M | |
|---|---|---|---|---|
| Common grade | DX51D+Z | SGCC | DX51D+Z | CS Type A/B/C |
| Draw grade | DX52D+Z, DZ53D+Z | SGCD | DX52D+Z, Dx53D+Z | FS Type A/B/C |
| Structural grade | Q280GD+Z | SGC340GD | S280GD+Z | SS275/Grade 40 |
| Q340GD+Z | SGC440 | S340GD+Z | SS340/Grade 50 |
3.9 Hot dip galvanized steel coil manufacturer in China
Large iron and steel enterprises are capable of producing a full range of products, from primary materials to deep processing. Some of China’s largest iron and steel enterprises include: Baosteel, WISCO, HBIS, ANSTEEL, Shougang etc.
Small private enterprises mainly purchase raw materials from large enterprises, and they specialize in producing a specific type of deep-processed steel plate. Galvanization is a common process among these private enterprises, with Shandong and Jiangsu provinces being the most concentrated areas.
You can find a lot of galvanized steel coil manufacturer in Alibaba & Made-In-China.
3.10 What are the main quality problems during purchasing galnvaized steel?
Wave edge
When the edge is waved during steel plate rolling, it may affect the subsequent processing.
White rust
Water remains on the surface, or the zinc is oxidized due to moisture during transportation and storage may cause white rust, but most white rust will not affect the processing or use.
Black spots
Black spots may be caused by further oxidation of white rust or friction during transportation.
3.11 How to deal with the quality problems of purchasing galvanized steel from China?
Due to high freight costs and customs duties, it is extremely difficult to return galvanized steel to China. In the event of any complaints regarding quality or delivery time, each case will be handled on an individual basis. After conducting a thorough investigation of the issues leading to the complaint and engaging in negotiations, cash compensation may be considered as a possible resolution.
4. How to produce hot dip galvanized steel？
4.1 Steps from iron ore to hot dip galvanized steel coil
Steel-making
Iron ore is melted in a blast furnace to produce molten steel, which is then cast into steel billets.
Hot rolling
The steel billets are heated to temperatures between 1100-1250 degrees Celsius and rolled into hot-rolled plates.
Cold rolling
The hot-rolled plates are further reduced in thickness to less than 8mm without reheating.
Hot-dip galvanizing
The cold-rolled steel plates are continuously passed through a molten zinc bath to apply a zinc coating.
4.2 Production process of continuous hot-dip galvanizing
The hot-dip galvanizing process involves several crucial steps. Initially, the steel undergoes a cleaning process to prepare its surface for galvanizing, including degreasing, pickling, and fluxing. Degreasing eliminates dirt, oil, and other organic residues. Pickling, which involves a mild acid bath, etches the steel and removes mill scale and iron oxide. Fluxing further removes any oxides and applies a protective layer to the steel surface to prevent further oxide formation prior to galvanizing.
After cleaning and drying, the steel is immersed in a molten zinc bath at temperatures around 840°F (449°C). The process involves coating the iron or steel object by immersing it in the bath, during which molten zinc spangles in and around the object, providing thorough protection to all surfaces.
After removing the object from the bath, the zinc coating on its exterior reacts with atmospheric oxygen to form zinc oxide (ZnO). Zinc oxide reacts further with carbon dioxide to form a protective layer called zinc carbonate (ZnCO3). This dull grayish film is relatively stable and adheres firmly to the surface of the iron or steel. In hot-dip galvanizing, the zinc chemically bonds with the steel, becoming an integral part of it, thereby providing protection.