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Application of galvanized steel sheet
Galvanized steel plate is to prevent the surface of the steel plate from corrosion and extend its service life. The surface of the steel plate is coated with a layer of metal zinc, which is called galvanized steel plate or galvanized steel plate.
Galvanized sheet is widely used in construction, light industry, automobile, home appliances, electronics, agriculture, animal husbandry and fishery, commodity packaging and other industries. In recent years, China's construction, home appliances and other industries have a rapid growth in the demand for galvanized sheet, with great market potential. Especially in recent years, with the rapid development of light construction structure, the annual increase of car production, the widespread popularity of household appliances, and the large export of electronic products by joint ventures and wholly-owned enterprises, the consumption of galvanized sheet has increased rapidly. According to the production mode, galvanized sheet is divided into hot galvanized sheet and electro galvanized sheet. At present, the production of domestic galvanized sheet can not meet the market demand either in quantity or in variety. It needs a large number of imports every year. The market share of domestic galvanized sheet production is relatively low, the domestic market is in short supply, and the market potential is huge.
Galvanized sheet can be divided into the following categories according to production and processing methods:
① Hot dip galvanized plate
A sheet of steel immersed in a molten zinc bath to adhere a layer of zinc to its surface. At present, it is mainly produced by continuous galvanizing process, that is, the rolled steel plate is continuously immersed in the bath with zinc melting to make galvanized steel plate;
② Alloyed galvanized sheet
This kind of steel plate is also made by hot dip galvanizing, but it is heated to about 500 ℃ immediately after being out of the tank, so as to form an alloy coating of zinc and iron. The galvanized sheet has good adhesion and weldability of coating;
③ Electro galvanized sheet
This kind of galvanized steel sheet has good machinability. However, the coating is thin and the corrosion resistance is not as good as that of hot dip galvanized sheet;
④ Single side plating and double side difference galvanized sheet
Single side galvanized steel sheet, i.e. products galvanized on one side only. In welding, coating, antirust treatment, processing and other aspects, it has better adaptability than double-sided galvanized sheet. In order to overcome the shortcomings of one side not coated with zinc, there is another kind of galvanized sheet coated with thin zinc on the other side, that is, the double-sided poor galvanized sheet;
⑤ Alloy, composite galvanized sheet
It is made of zinc and other metals such as lead, zinc alloy and even composite plated steel plate. This kind of steel plate not only has excellent antirust performance, but also has good coating performance.
Appearance of galvanized sheet
(1) Surface state: due to different treatment methods in the plating process, the surface state of galvanized sheet is also different, such as ordinary zinc flower, fine zinc flower, flat zinc flower, non zinc flower and phosphatized surface.
(2) The galvanized sheet shall have a good appearance and shall not have defects harmful to the use of the product, such as no plating, holes, cracks and scum, over plating thickness, scratch, chromic acid dirt, white rust, etc. Foreign standards are not very clear about the specific appearance defects.
The main problems in the production and consumption of galvanized sheet in China
1. Insufficient production capacity and small unit capacity
2. Production varieties, specifications and quality need to be improved
① Incomplete production varieties
② Single production specification
③ Lack of zinc alloy plating plate
④ Low self-sufficiency rate of raw materials for hot galvanized sheet
In a word, high-quality and high-grade hot-dip galvanized sheet, especially galvanized sheet for automobile and household appliances, requires very high surface quality, excellent plate type, different alloying coating, good deep drawing performance and high strength. Therefore, the production of high-quality hot-dip galvanized sheet is a systematic project. The requirements of consistent quality system are put forward for a series of production processes, such as smelting, continuous casting, hot rolling, cold rolling, galvanizing, etc., which are difficult to produce.