Production technology of galvanized steel coil
The galvanized coil has different surface states due to different treatment methods in the coating process, such as ordinary zinc roller, fine zinc roller, flat zinc roller, non zinc roller and phosphating surface. The galvanized coil plate shall have a good appearance and shall not have defects harmful to the use of the product, such as no coating, holes, cracks and scum, too thick coating, scratches, chromic acid dirt, white rust, etc.
According to the production and processing methods, it can be divided into the following categories:
Hot dip galvanized steel coil. The coil is immersed in a molten zinc bath so that its surface adheres to the coil. At present, the continuous galvanizing process is mainly used to produce the galvanized steel coil, that is, the rolled steel plate is continuously immersed in the zinc melting galvanizing tank.
Alloy galvanized steel coil. This kind of steel coil is also made by hot-dip method, but as soon as it comes out of the tank, it is heated to about 500 ℃, forming an alloy coating of zinc and iron. The galvanized coil has good coating adhesion and weldability.
Galvanized steel coil. The galvanized steel coil produced by electroplating has good processing performance. However, the coating is thin and its corrosion resistance is not as good as that of hot-dip galvanized coil.
Single side and double side difference galvanized steel coil. Single side galvanized steel coil, that is, the product is only galvanized on one side. It has better adaptability in welding, coating, antirust treatment and processing than double-sided galvanized coil. In order to overcome the shortcomings of one side without galvanizing, the other side also has a galvanizing roller coated with a thin layer of zinc, namely double-sided differential galvanizing roller.
Alloy and composite galvanized steel coils. It is an alloy made of zinc, lead, zinc and other metals, and even a composite electroplated steel coil. This kind of steel coil not only has excellent antirust performance, but also has good coating performance. In addition to the above five, there are color galvanized steel coil, printed coating galvanized steel coil, PVC laminated galvanized steel coil, etc. However, hot dip galvanized coil is still widely used.
The reason why the galvanized coil is coated with zinc on the steel surface is that the steel plate is easy to be oxidized by oxides in the air, such as water, so as to be corroded. The purpose of applying a layer of zinc is to better protect the steel. Galvanized coil has two advantages, one is adhesion, the other is weldability. Because of these two advantages, they are widely used in the fields of construction, industry, automobile industry and commerce. Another important feature is corrosion resistance, which can produce good results in the manufacture of household appliances.