Today, hot-dip galvanized steel pipes are a common type of fire protection pipes, playing an irreplaceable role in the fire safety industry. Why can't hot-dip galvanized pipes be replaced by cheaper welded pipes or cold-galvanized pipes?
Hot-dip galvanizing was invented in the mid-18th century, evolving from the hot-dip tinning process, with a history of over 300 years. To this day, hot-dip galvanizing remains a widely used and effective processing method for steel corrosion prevention.
Hot-dip galvanized pipes: They involve the reaction between molten metal and the iron matrix to produce an alloy layer, thereby integrating the matrix and the coating. The process begins with pickling the steel pipes to remove iron oxide from their surfaces. After pickling, the pipes are cleaned in a bath of ammonium chloride or zinc chloride aqueous solution, or a mixed solution of both. They are then fed into a hot-dip galvanizing bath. Hot-dip galvanizing offers advantages such as uniform coating, strong adhesion, and long service life. In northern regions, the majority of processes adopt the technique of directly rolling galvanized strips to form pipes and replenishing zinc.
Hot-dip galvanized steel pipes: Complex physical and chemical reactions occur between the steel pipe matrix and the molten plating solution, forming a corrosion-resistant and structurally dense zinc-iron alloy layer. This alloy layer integrates seamlessly with the pure zinc layer and the steel pipe matrix, resulting in strong corrosion resistance.
To enhance the corrosion resistance of steel pipes, galvanizing is applied. Galvanized steel pipes are categorized into hot-dip galvanized and electro-galvanized types. Hot-dip galvanized pipes have a thicker coating, while electro-galvanized pipes have lower costs but a less smooth surface. Blow-oxygen welding pipes: Used for steelmaking blow-oxygen applications, they typically employ small-diameter welded steel pipes in eight sizes ranging from 3/8 to 2 inches. Made from steel strips of grades 08, 10, 15, 20, or 195-Q235, some undergo effective aluminizing treatment for corrosion prevention.
Production Process:
Galvanized strip → Uncoiling → Stretching → Pipe rolling → Welding → Scar removal → Passivation and rinsing → Zinc replenishment → Shaping → Marking → Cutting → Packing → Drying → Weighing.
