Pre Galvanizing Process of Steel Pipe

Content Details

What is Pre Galvanized Steel Pipe?

Pre Galvanized Steel Pipe is manufactured by forming and welding galvanized steel strips or coils into pipes after the steel has already been coated with a zinc layer. Unlike Hot Dip Galvanized Steel Pipe, which is galvanized after pipe production, the pre galvanizing process applies zinc coating to the steel material before tube forming.

During production, galvanized steel coils with a uniform zinc coating are processed through slitting, forming, welding, sizing, cutting, and inspection procedures to produce finished galvanized pipes with a smooth surface and consistent coating performance.

Pre galvanized steel pipes are widely used in applications requiring economical corrosion protection, good appearance, and efficient production.

Manufacturing Process of Pre Galvanized Steel Pipe

1. Galvanized Steel Coil Preparation

The production process starts with high-quality galvanized steel coils. The steel coils are usually produced through a continuous hot-dip galvanizing line, where steel strips pass through molten zinc to obtain a protective zinc coating.

The galvanized coating provides corrosion resistance and protects the base steel from oxidation. Common coating grades include:

• Z40
• Z60
• Z80
• Z120
• Z180

The galvanized steel coil is inspected before processing to ensure:

• Zinc coating quality
• Surface smoothness
• Chemical composition
• Mechanical properties

2. Steel Coil Slitting

According to the required pipe specifications, large galvanized steel coils are slit into narrower steel strips with suitable widths.

The slitting process ensures:

• Accurate strip width
• Smooth strip edges
• Stable pipe forming performance

The processed galvanized strips are then transferred to the pipe production line.

3. Tube Forming Process

The galvanized steel strip enters the forming machine and gradually changes from a flat strip into a round, square, or rectangular tube shape through a series of forming rollers.

During this process:

• The strip edges are aligned accurately
• The pipe shape is gradually formed
• The original zinc coating remains on the surface

Advanced forming technology helps maintain consistent pipe dimensions and surface quality.

4. ERW Welding Process

After forming, the edges of the steel strip are joined through High Frequency Electric Resistance Welding (ERW).

The ERW welding process uses electrical resistance heat to melt and bond the steel edges together without additional welding materials.

Advantages of ERW welding:

• High production efficiency
• Strong and reliable weld seams
• Smooth internal and external surfaces
• Suitable for large-scale pipe production

After welding, the weld area is treated to improve appearance and quality.

5. Sizing and Straightening

After welding, the pipes pass through sizing rollers to achieve accurate dimensions.

The sizing process controls:

• Outer diameter
• Wall thickness
• Roundness
• Straightness

Straightening equipment ensures the finished pipes meet international dimensional requirements.

6. Cutting and Surface Inspection

The continuous pipe is cut into standard lengths according to customer requirements, commonly:

• 5.8 meters
• 6 meters
• Customized lengths

Each pipe is inspected for:

• Surface appearance
• Zinc coating condition
• Welding quality
• Dimensional accuracy

Qualified products are prepared for packaging and shipment.

7. Packaging and Delivery

Pre galvanized steel pipes are usually bundled with steel straps and protected during transportation.

Common packaging methods include:

• Steel strip bundling
• Waterproof wrapping
• Customized marking
• Container loading

Proper packaging helps prevent damage during international transportation.

Difference Between Pre Galvanized Pipe and Hot Dip Galvanized Pipe

Advantages of Pre Galvanized Steel Pipe

1. Uniform Zinc Coating

Since the steel strip is galvanized before forming, the zinc layer is evenly distributed across the surface, providing consistent protection.

2. Smooth Surface Finish

Pre galvanized pipes have a clean and attractive appearance, making them suitable for applications where surface quality is important.

3. High Production Efficiency

The continuous manufacturing process allows large-volume production with stable quality and shorter delivery time.

4. Cost Effective Solution

Compared with hot dip galvanized pipes, pre galvanized pipes provide economical corrosion protection for many indoor and light-duty applications.

5. Easy Fabrication

The pipes can be easily cut, welded, and processed according to different project requirements.

Applications of Pre Galvanized Steel Pipe

Pre galvanized steel pipes are widely used in:

Electrical Conduit Systems

Used for cable protection and electrical wiring systems due to their corrosion resistance and smooth surface.

Greenhouse Structures

Suitable for agricultural greenhouse frames because of their lightweight structure and durability.

Furniture Manufacturing

Commonly used for steel furniture frames, shelves, and decorative structures.

Light Steel Construction

Applied in partition frames, support structures, and indoor building systems.

Ventilation and Mechanical Systems

Used in air duct supports, equipment frames, and other industrial applications.

Why Choose Our Pre Galvanized Steel Pipe?

We manufacture pre galvanized steel pipes with advanced ERW production lines and strict quality control systems.

Our advantages include:

• Stable galvanized steel coil supply
• Professional ERW pipe production technology
• Accurate dimensions
• Smooth surface finish
• Customized sizes and specifications
• Reliable export packaging

Our pre galvanized steel pipes are suitable for construction, industrial, agricultural, and infrastructure projects worldwide.