Galvanized steel sheet
1. Overview (1) Definition: In order to prevent corrosion on the surface of the steel plate and prolong its service life, a layer of metallic zinc is coated on the surface of the steel plate. This kind of zinc-coated thin steel plate is called galvanized steel plate. (2) Classification and use: According to production and processing methods, it can be divided into the following categories: ① Hot-dip galvanized steel sheet. The thin steel plate is immersed in the molten zinc tank, so that a thin steel plate with a layer of zinc is adhered to the surface. At present, the continuous galvanizing process is mainly used for production, that is, the rolled steel sheet is continuously immersed in a galvanized bath with molten zinc to make a galvanized steel sheet; ②Alloyed galvanized steel sheet. This kind of steel plate is also manufactured by hot dipping method, but immediately after leaving the tank, it is heated to about 500 ℃ to form an alloy film of zinc and iron. This kind of galvanized sheet has good paint adhesion and weldability; ③Electro-galvanized steel sheet. The galvanized steel sheet produced by the electroplating method has good workability. However, the coating is thinner, and the corrosion resistance is not as good as the hot-dip galvanized sheet; ④Single-sided and double-sided poorly galvanized steel. Single-sided galvanized steel sheet is a product that is galvanized on one side only. In welding, painting, anti-rust treatment, processing, etc., it has better adaptability than double-sided galvanized sheet. In order to overcome the shortcomings of uncoated zinc on one side, there is another kind of galvanized sheet coated with a thin layer of zinc on the other side, that is, double-sided differential galvanized sheet; ⑤ alloy, composite galvanized steel sheet. It is a steel plate made of zinc and other metals such as lead and zinc alloys and even composite plating. This kind of steel plate not only has excellent anti-rust performance, but also has good coating performance. In addition to the above five types, there are color galvanized steel sheets, printed coated galvanized steel sheets, polyvinyl chloride laminated galvanized steel sheets, etc. But the most commonly used is still hot-dip galvanized sheet. Galvanized steel sheets can be divided into general use, roof use, building exterior panel use, structural use, corrugated sheet use, drawing use and deep drawing use. (3) Main production plants and import producing countries: ①Main domestic production plants: Wuhan, Anshan Iron and Steel, Baosteel and Guangdong, etc.; ②Main production countries abroad include Japan, Germany, Russia, France, etc. 2. Size specifications The relevant product standards list the recommended standard thickness, length, width and allowable deviation of the galvanized sheet. You can refer to the relevant product standards provided in “8” of this section. 3. Appearance (1) Surface condition: The surface condition of the galvanized sheet is different due to the different treatment methods in the coating process, such as ordinary spangle, fine spangle, flat spangle, zinc-free and phosphated surface. German standards also provide for surface grades. (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, excessive plating thickness, scratches, chromic acid dirt, white rust, etc. Foreign standards are not very clear about specific appearance defects. Some specific defects should be listed in the contract when ordering. 4. Galvanized amount (1) Standard value of galvanized amount: The galvanized amount is a commonly used effective method to express the thickness of the zinc layer of the galvanized sheet. The unit of galvanizing amount is g/m2. Japanese, American and German standards for the galvanized steel sheet galvanized amount are detailed in Table 6-7-4. (2) Measurement method: See the relevant standards in “8” for sampling requirements and test methods. 5. Chemical composition The requirements for the chemical composition of the galvanized sheet substrate are different in various national standards. For example, Japan does not require it, but the United States requires it. Generally, finished product inspection is not performed. 6. Packaging There are two types of galvanized sheets cut to length and galvanized sheets in coils. It is usually packaged with iron sheet, lined with moisture-proof paper, and tied with iron waist on the bracket. The strapping must be firm to prevent the inner galvanized sheets from rubbing against each other. 7. Main foreign standards related to galvanized sheets (1) Product standards: JIS G3302-94 galvanized steel sheet; JIS G3312-94 painted galvanized iron sheet; JIS G3313-90 (96) electro-galvanized steel sheet and steel strip; hot dip General requirements for galvanized steel sheet; ASTM A526-90 commercial-grade hot-dip galvanized steel sheet; ASTMA 527-90 (75) bite-type hot-dip galvanized steel sheet; ASTMA 528-90 deep-drawing hot-dip galvanized steel sheet; roofing and Hot-dip galvanized steel sheet for siding; hot-dip galvanized steel sheet for ASTMA444-89 trenches; ASTM A446-9 3 structural hot-dip galvanized steel sheet; ASTMA5999-92 cold-rolled electro-galvanized steel sheet; ASTMA642-90 hot-dip galvanized steel sheet Special deoxidized deep drawing steel sheet; ΓOCT7118-78 galvanized steel sheet; DINEN10142-91 part 1 low carbon steel hot-dip galvanized steel strip and steel plate; DINEN1012-92 part 2 hot-dip galvanized steel sheet. (2) Test method standards: JIS H0401-83 hot-dip galvanizing test method; DIN50952-69 hot-dip galvanizing test method. 8. Mechanical properties (1) Bend test: Bend test is the main item to measure the process performance of thin plates, but the requirements of various galvanized sheets in various national standards are not consistent. American standards do not require bending and tensile tests except for the structural level. In Japan, bending tests are required except for structural grade, building corrugated board and general corrugated board. ①Requirements: Generally, after the galvanized sheet is bent 180°, the outer surface of the galvanized sheet must not have the zinc layer detached, and the plate base must not be cracked or broken; ②Test method: See “8” for the relevant product standards for sampling locations and quantities, and the bending angle is 180 °, the ratio of the inner space to the thickness of the test sample, see the relevant product standards listed in “8”. (2) Tensile test: ①Performance index: Generally speaking, only galvanized sheets for structure, drawing and deep drawing have tensile performance requirements. Among them, the structural galvanized sheet requires yield point, tensile strength and elongation, etc.; for stretching, only elongation is required. For specific values, see the relevant product standards in “8” of this section; ②Test method: the same as the general thin steel plate test method, see the relevant standards provided in “8” and the test method standards listed in “Common carbon steel thin steel plate”.