Galvanized sheet refers to a steel sheet coated with a layer of zinc on the surface. Galvanizing is a frequently used economical and effective anticorrosion method, and about half of the world’s zinc production is used in this process. Hot-dip galvanized steel sheet has ideal corrosion resistance, forming, coating and other comprehensive properties, as well as low cost and good appearance.
Hot dip galvanized steel
Galvanized sheet is mainly used in construction, light industry, automobile, agriculture, animal husbandry, fishery and commerce. The construction industry is mainly used to manufacture anti-corrosion industrial supplies and panels, roof grilles, balcony panels, window sills, newsstands, warehouses, rolling doors, heaters, rainwater pipes, etc. used in civil construction houses; and the light industry industry uses it to manufacture household appliance shells , Civil chimneys, kitchen utensils, etc., the automotive industry is mainly used to manufacture corrosion-resistant parts of cars, etc .; agriculture, animal husbandry and fishery are mainly used as food storage and transportation, meat and aquatic products frozen processing appliances, etc .; commercial use is mainly used as materials Storage and transportation, packaging utensils, etc. Household appliances such as refrigerators, washing machines, switch cabinets, air conditioners, microwave ovens, toasters, copiers, vending machines, electric fans, vacuum cleaners, etc. will also use galvanized sheets.
The packaging of galvanized sheet can be divided into two types: galvanized sheet cut to length and galvanized sheet with coil. It is usually packed in iron sheet, lined with moisture-proof paper, and strapped on the bracket with an iron waist. The strapping should be firm to prevent the internal galvanized sheets from rubbing against each other.
Hot dip galvanized steel sheet classification
The galvanized sheet is divided according to the layout: there are zinc flower galvanized sheet and non-zinc galvanized sheet according to layer thickness: 80G zinc, 100G zinc, 120G zinc, 180G zinc, 275G zinc can be divided into the following according to production and processing methods class:
(1) Hot-dip galvanized steel sheet. The steel sheet is immersed in the molten zinc bath, and a layer of zinc thin steel sheet is adhered on the surface. At present, it is mainly produced by a continuous galvanizing process, that is, a coil of steel sheet is continuously immersed in a zinc-melted plating tank to make a galvanized steel sheet;
(2) Alloyed galvanized steel plate. This kind of steel plate is also made by hot dipping method, but it is heated to about 500 ℃ immediately after leaving the trough to make it form an alloy film of zinc and iron. This galvanized sheet has good paint adhesion and weldability;
(3) Electro-galvanized steel sheet. The galvanized steel sheet manufactured by the electroplating method has good workability. However, the coating is thin, and the corrosion resistance is not as good as the hot-dip galvanized sheet;
(4) Single-sided and double-sided galvanized steel sheets. Single-sided galvanized steel sheet, that is, products that are galvanized on only one side. 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 a galvanized sheet coated with a thin layer of zinc on the other side, that is, a double-sided galvanized sheet;
(5) Alloy, composite galvanized steel plate. It is a steel plate made of zinc and other metals such as aluminum, lead, zinc, etc. alloy or even composite plating. This steel plate has both excellent anti-rust performance and good coating performance.
In addition to the above five types, there are color galvanized steel sheets, printed coating galvanized steel sheets, polyvinyl chloride laminated galvanized steel sheets, etc. But currently the most commonly used hot dip galvanized sheet.
Basic requirements for appearance quality
1. The galvanized layer is slightly silvery gray with light yellow tone, and the crystal is uniform and fine;
2. The galvanized layer passivated by chromate is divided into four types according to different processes. Its typical appearance is as follows: bright: bright, clear, sometimes with light blue tone bleaching: clear, slightly rainbow-colored rainbow: rainbow Color dark: grass green, olive green, tan, black, etc.
No defects are allowed:
1. No local coating;
2. Rainbow color, the color is purple-red after passivation;
3. More water marks or chromate residues;
4. Orange peel, blisters or more severe stripes;
5. Dendritic and spongy crystals;
6. Excessive corrosion or mechanical rubbing;
7. Erasable passivation film or partial passivation film.
1. Due to the different materials, processing methods and surface conditions of the workpiece, the coating has a slightly uneven color and gloss;
2. Slight water marks and chromate residues;
3. The passive film has slight local abrasions and spot mechanical abrasions;
4. The screws or rivets and other fasteners are slightly darker in the holes or percussion parts;
5. The workpiece color after dehydrogenation is slightly dark;
6. There is slight roughness on the sharp edge of the workpiece that does not affect the assembly;
7. Slight fixture printing;
8. The coating at the welding seam of the weldment is dark or has small black spots;
9. For non-through holes with a diameter greater than 8mm at a depth exceeding one diameter, or for a through hole with a diameter not greater than 6mm at a depth exceeding two diameters, no plating is allowed;
10. On the premise of not affecting the assembly and performance, the plating surface of the workpiece that is partially electroplated is allowed to expand.
Standard value of galvanized amount: galvanized amount is a commonly used effective method to indicate the thickness of zinc layer of galvanized sheet. The unit of galvanization is g / m2.
Galvanized steel sheet index (unit: g / m2)
JISG3302 code: Z12, Z18, 222, 225, 227, 235, 243, 250, Z60
The galvanized amount is: 120, 180, 220, 250, 270, 350, 430, 500, 600
ASTMA525: A40, A60, G60, G90, G115, G140, G165, G185, G210
The galvanized amounts are: 122,183, 183,275, 351, 427, 503, 564, 640
(1) Tensile test: generally refers to the tensile test, which can measure a series of strength indexes and plastic indexes of the material. Strength usually refers to the ability of a material to resist elastic deformation, plastic deformation, and fracture under external force. Plasticity refers to the ability of a metal material to deform plastically under load without damage. Commonly used plasticity indicators are elongation and shrinkage.
Performance indicators: Generally speaking, only the galvanized sheets for structural, drawing and deep drawing have tensile performance requirements. Among them, the galvanized sheet for structure requires yield point, tensile strength and elongation, etc .; for stretch, only elongation is required.
(2) Bending test: The bending test is mainly used to determine the flexural strength of brittle and low plastic materials (such as cast iron, high carbon steel, tool steel, etc.) and can reflect the deflection of the plastic index.
Requirements: It is generally required that after the galvanized sheet is bent 180 degrees, the outer surface must not have the zinc layer detached, and the sheet base must not be cracked or broken.
Calculation formula of galvanized sheet: M = 7.85 * length * width thickness + calculated weight of zinc layer (lookup table) (density of steel = 7.85 g / cm3).
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