Work flow of galvanized pipe welding machine

Galvanized pipe welding machine is the core equipment for the production of galvanized welded steel pipe. Its process combines high-frequency welding technology and hot dip galvanizing process to form a galvanized steel pipe with both strength and corrosion resistance.

1. Equipment composition and process principle
Galvanized pipe production line mainly includes ‌ uncoiler, leveler, shear butt welder, forming unit, high frequency welding machine, galvanized equipment ‌ and testing system. The process is divided into two stages:
Welding pipe forming stage ‌ : steel strip is formed and welded into steel pipe;
Galvanizing treatment stage ‌ : Hot dip galvanizing on the surface of the steel pipe to form a protective layer.
2. Detailed work flow
1. Prepare raw materials
Steel strip selection ‌ : Choose SPHC, Q195 and other low carbon steel strip, width according to the diameter of the pipe customized.
Uncoiling and leveling ‌ : the steel strip is unfolded by the uncoiling machine, and the internal stress is eliminated by the multi-roll flattening machine to ensure that the flatness error is less than 0.5mm/m.
2. Forming and welding
Forming machine processing ‌ :
The steel strip is gradually curled into a tubular shape by 12-24 sets of roller die, and the forming Angle is precisely controlled (±0.1°).
High-frequency induction welding:
The high frequency current of 100-400kHz is applied at the joint of the forming tube blank, and it is heated to 1350-1400℃ instantaneously. The metallurgical bonding is realized by applying 300-500MPa pressure through the extrusion roll, and the welding speed can reach 30-120m/min.
3. Post-welding treatment
Water cooling type ‌ : spray cooling system fast cooling, stable steel pipe crystal phase structure.
Sizing and straightening ‌ : Adjust roundness (ellipticity ≤1%) by a three-roll sizing machine, and eliminate bending by a multi-stage straightening roll.
4. Pretreatment before galvanizing
Pickling and rust removal ‌ : The steel pipe is immersed in 18-25% hydrochloric acid solution (50-60℃) for pickling for 3-10 minutes to remove surface oxides.
Assistant plating treatment ‌ : immersed in zinc ammonium chloride solvent (pH 4.5-5.5) to form a protective film to prevent secondary oxidation.
5. Hot dip galvanizing
Zinc pot process ‌ :
The steel pipe is immersed in a liquid zinc tank (zinc purity ≥99.995%) at 450-460℃, and the residence time is 8-15 seconds to form a 60-120μm coating. The thickness of zinc layer is controlled by an air knife, and the standard for double-sided galvanizing is 275g/m² (ASTM A53).
Cooling passivation ‌ :
After water cooling, chromate passivation treatment (Cr³+ concentration 0.2-0.5g/L) enhances corrosion resistance.

Through the integration of precision forming, efficient welding and advanced galvanizing process, the anti-corrosion performance of steel pipe and production efficiency are improved. With the application of intelligent manufacturing technology, the equipment is continuously upgraded in the direction of higher precision and lower energy consumption, providing high-quality pipe protection for construction, municipal, energy and other fields.