galvanized sheet
1.What is the significance of leveling hot-dip galvanized sheets?
Answer: With expanding applications of hot-dip galvanized sheets, modern continuous galvanizing lines achieve the following through sheet leveling:
① Improves flatness and surface evenness of thin sheets while flattening surface zinc particles, resulting in smoother surfaces – particularly beneficial for deep drawing and high-precision applications;
② Pre-blasted leveling rolls impart controlled surface roughness. This enhances coating adhesion, stores lubricant for improved die lubrication during deep drawing;
③ For painted galvanized sheets with minimized spangle patterns, small spangles may still become visible through paint. Leveling provides a uniform silver-white appearance for high-end products;
④ Leveling reduces lower yield point, eliminates or obscures yield plateau, preventing stretcher strain lines during stretching/deep drawing, thereby improving formability.
2.What are the main uses of hot-dip galvanized steel sheets?
Answer: Hot-dip galvanized steel sheets are mainly used in industries such as construction, home appliances, automobiles, machinery, electronics, and light industry.
3.What types of galvanizing methods are currently available worldwide?
Answer: There are three types of methods: electro-galvanizing, hot-dip galvanizing, and zinc coating.
4.According to the different annealing methods, into what two types can hot-dip galvanizing be classified?
Answer: It can be classified into two types: in-line annealing and off-line annealing, also known as the protective gas method and the flux method, respectively.
5.What are the commonly used steel grades for hot-dip galvanized sheets?
Answer: Product types: Commercial Quality (CQ), High-Strength Low-Alloy (HSLA), Deep Drawing Quality (DDQ), Bake Hardened (BH), Dual Phase (DP), TRIP Steel (Transformation Induced Plasticity Steel), etc.
6.What are the forms of galvanizing annealing furnaces?
Answer: There are three forms: vertical annealing furnace, horizontal annealing furnace, and vertical-horizontal annealing furnace.
7.What are the methods for testing the corrosion resistance of hot-dip galvanized sheets?
Answer: There are three methods for testing the corrosion resistance of hot-dip galvanized sheets: salt spray test; humidity test; etching test.
8.Why is rust prevention treatment still necessary for hot-dip galvanized products?
Answer: When hot-dip galvanized sheets are in humid air, especially air containing acidic substances such as SiO₂, CO₂, NO₂, and NO, the galvanized layer surface will quickly develop loose-textured white rust. The main components of white rust are ZnO and Zn(OH)₂. This white rust not only affects appearance but also causes significant difficulties for subsequent use.
9.What are the causes of white rust?
Answer: The causes of white rust include: storing hot-dip galvanized products together with corrosive media such as acids, alkalis, or salts; damage to the passivation film or protective coating; ineffective passivation or oiling; poorly ventilated and humid storage warehouses; water exposure during transportation of galvanized sheets; condensation formed when transporting at low temperatures and storing at high temperatures.
10.How is coating thickness calculated?
Answer: The coating thickness formula is: Dz = Gz / (Sz * dz) where: Dz – Coating thickness (mm), Gz – Coating weight per square meter (g), Sz – Coating area (mm²), dz – Zinc density. The above formula can be simplified to: Dz = 0.000139Gz.
11.What causes zinc particles?
Answer: Causes include: issues with the base steel, primarily its cleanliness and iron powder content; excessively high zinc bath temperature causing dross to float; excessive Al content affecting iron solubility.
Since its establishment in 2008, GNEE STEEL has always been customer-oriented, constantly improving its product system and enhancing its service level. Today, our steel products are exported to more than 160 countries around the world, and we have more than 8,000 cooperative customers.
