Color steel commonly used substrates and coatings

According to the coatings, the coatings that can be produced by hot-dip plating can basically be divided into the following 6 types:

GI (pure zinc coating);

GA (zinc-iron alloy coating);

55% Al-Zn (aluminum zinc coating; GALVALUME);

5%Al-Zn (zinc-aluminum coating, GALVAN);

Aluminizing (aluminum plating), aluminum plating can be divided into two categories, one is pure aluminum plating, and the other is aluminized silicon products;

Zinc-aluminum-magnesium products, new types of coated zinc-aluminum-magnesium products in recent years, such as Zn-5Al-3Mg. Zinc Aluminum Magnesium is a series of products that can include different Mg content and Al content.

1. Color coated steel plate for cold-rolled base plate

The color plate produced by the cold-rolled substrate has a smooth and beautiful appearance, and has the processing performance of a cold-rolled plate; but any small scratches on the surface coating will expose the cold-rolled substrate to the air, so that the iron is exposed quickly Red rust is formed. Therefore, these products can only be used for temporary isolation measures and indoor materials that are not demanding.

2. Hot-dip galvanized color coated steel sheet

The product obtained by coating the organic paint on the hot-dip galvanized steel sheet is the hot-dip galvanized color-coated steel sheet. In addition to the protective effect of zinc, the hot-dip galvanized color-coated sheet also has an organic coating on the surface to insulate and protect and prevent rust, and its service life is longer than that of the hot-dip galvanized sheet. The zinc content of the hot-dip galvanized substrate is generally 180g/m2 (double-sided), and the maximum zinc content of the hot-dip galvanized substrate for building exterior is 275g/m2.

3. Hot-dip aluminum-zinc color-coated sheet

According to requirements, hot-dip aluminum-zinc steel sheets can also be used as color-coated substrates (55% AI-Zn and 5% AI-Zn).

4. Electro-galvanized color coated sheet

The electro-galvanized sheet is used as the substrate, and the product obtained by coating with organic paint and baking is an electro-galvanized color-coated sheet. Because the zinc layer of the electro-galvanized sheet is thin, the zinc content is usually 20/20g/m2, so this product is not suitable for use to make walls, roofs, etc. outdoors. But because of its beautiful appearance and excellent processing performance, it can be mainly used for home appliances, audio, steel furniture, interior decoration, etc.

In China, for the choice of color-coated steel plates, users are relatively less concerned about steel types. Because most of the domestic color-coated steel production plants have fewer types of steel, most of them are DC51 (because the hot-rolled plate or rolled hard coil they purchase is basically a steel type), and some color-coated steel plants with hot-dip galvanizing production lines It is very difficult to produce full-hard steel (S550) or high-strength steel (S350, etc.) through hot-dip galvanizing and annealing, because they cannot control the quality and chemical composition of the substrate. Therefore, the quality stability is poor, which leads to large performance fluctuations and causes deterioration of the profiled board.

For buildings, the bearing weight (wind load, snow load, construction personnel and machinery), the span of the building, the design of the purlin, etc. all depend on the strength of the steel plate. For the building maintenance structure, color coating and galvanized steel are used. In other words, there are corresponding standards in foreign countries. Such as ASTM653 and ASTM792 in the United States, JISG3302 in Japan, JISG3321 in Japan, and EN10215 and EN10147 in Europe. According to steel types, it is divided into CQ (common commercial grade), DQ (general stamping), HSS (high-strength structural steel), and FH (full hard steel).

CQ general commercial grade

Non-ferrous metal smelters (copper, zinc, aluminum, lead, etc.) are the most challenging for the service life of color-coated steel sheets. However, a reasonable selection of materials, design, and environmental protection investment can ensure or increase the service life of color-coated steel plates. It should be possible to perform replacement or maintenance in 10 years.

DQ general stamping

Since the general construction color panels are roll forming or composite sandwich cores, they do not require high stamping performance of the materials, so they are rarely used in the construction field (except for some doors and windows color panels).

HSS high-strength structural steel

According to the European standard HSS, it can be divided into 4-5 steel grades with different strengths. However, because ordinary CQ grade materials can replace low-strength HSS steel, the steel grades with a yield strength of 280Mpa and 345Mpa are more commonly used in the market. TSTE28 and TS350GD produced by Baosteel are these two steel grades. Compared with ordinary CQ, HSS steel has several advantages: 1. Due to the low yield ratio, this steel has good fire resistance and seismic resistance. 2. For thicker steel plates, it can manufacture large-span arched plates. 3. For general exterior wall and roof panel type, it can be appropriately thinner than CQ material, which can save material consumption.

FH all hard steel

It is a type of steel that increases the yield strength of steel plates by controlling the annealing temperature. According to international general standards, the yield strength is ≥550Mpa, and the tensile strength is ≥570Mpa. This type of material has high strength and low elongation, and is suitable for shallow formed steel plates, which can greatly save materials when used. Therefore, various countries are rushing to research and develop this kind of steel. In foreign standards, materials with high strength and good elongation are also described. For example, HSLA (low-alloy high-strength) is used to add strengthening alloying elements during steelmaking, but due to the high strength, there is a limit to increasing the reduction rate during rolling in steel plants, so it is used as a thinner color-coated plate for maintenance structure The HSLA steel grade is rarely used (the other disadvantage is the high cost).

Based on Baosteel's years of experience in using steel grades, the shape of the final product of color-coated steel plate is closely related to the strength grade of the steel plate, the shape of the profiled steel plate, and the processing machine.

In general, the more processing passes, the better the plate shape, and the slower the processing speed and the better the plate shape. For the profile of the profiled steel plate, the shallow wave plate is better than the high wave plate. For the strength of the steel plate, the tendency of the plate shape after strength processing to deteriorate is more obvious. Another reason for the relatively poor shape of high-strength steel is that many color-coating manufacturers only increase the yield strength of the material by lowering the annealing temperature of hot-dip galvanizing, which will result in an imbalance in the mechanical properties of the steel plate in the width direction. This imbalance is caused by the unevenness of the strip temperature in the entire width direction. The temperature drop may cause the temperature of some parts to be lower than the annealing temperature for recrystallization of the steel sheet.