Galvanized welded pipe and seamless galvanized pipe are two common metal pipe products, which have significant differences in manufacturing process, performance characteristics and application scenarios. The following are the main differences between the two:
1.Manufacturing process
Galvanized welded pipe:
First, the steel plate or steel strip is curled and formed, the seam is welded by high-frequency welding process, and then hot-dip galvanized. The welding process will leave a longitudinal weld inside the pipe.
Seamless galvanized pipe:
Solid steel billet is formed in one time by perforation, hot rolling or cold drawing, without welds, and the overall structure is continuous and uniform, and then galvanized.
2. Structural characteristics
Galvanized welded pipe:
There is a longitudinal weld, and the material and mechanical properties of the weld area may be slightly different from those of other parts of the pipe body. The pipe wall thickness is relatively uniform, but due to the influence of the welding process, there may be slight internal and external burrs.
Seamless galvanized pipe:
Completely without welds, uniform overall structure, smooth inner wall without joints, high wall thickness precision, and isotropic mechanical properties.
3. Mechanical properties
Strength:
The compressive and tensile strengths of seamless pipes are usually higher than those of welded pipes because they have no welding heat-affected zone and the material is more uniform.
Pressure bearing capacity:
Seamless pipes are more suitable for high-pressure environments (such as hydraulic systems), while welded pipes are mostly used in medium and low-pressure situations (such as building scaffolding).
4. Corrosion resistance
The galvanizing process of both is the same (hot-dip galvanizing), but because there are welds in welded pipes, if the welding quality is poor, the welds may become weak points in corrosion resistance. Seamless pipes have no welds, so the overall corrosion resistance is more stable.
5. Cost and price
Galvanized welded pipe:
The production process is simple, efficient, and low cost, and the price is usually 20%~40% lower than that of seamless pipes.
Seamless galvanized pipe:
The production process is complex, the energy consumption is high, the cost is significantly increased, and the price is relatively expensive.
6. Application scenarios
Galvanized welded pipe:
Building structures (such as scaffolding, guardrails), municipal engineering (drainage, HVAC), agricultural greenhouses and other occasions with low pressure requirements.
Seamless galvanized pipe:
High-pressure fluid transportation (petroleum, chemical pipelines), mechanical structural parts, automobile transmission shafts and other fields with high strength and sealing requirements.
7. Size range
Galvanized welded pipe:
Wide diameter range (usually Φ15mm~Φ2000mm), large diameter thin-walled pipes can be produced.
Seamless galvanized pipe:
Due to process limitations, small-diameter pipes (Φ6mm~Φ500mm) are more common, and the production cost of extra-large diameters is extremely high.
How to choose?
Prefer welded pipes: when budget is limited, low pressure environment, large diameter or thin wall pipes are required.
Seamless pipes: when high pressure, high strength, high sealing requirements (such as gas pipelines) or precision machinery applications.
Notes
Welded pipes need to check the weld quality (such as X-ray flaw detection) to avoid incomplete penetration or cold welding.
Seamless pipes need to confirm whether they have been cold rolled/hot rolled. Cold rolled pipes have higher precision but higher costs.
Both need to check the adhesion of the zinc layer (such as hammer test) to ensure that the anti-corrosion performance meets the standards.
Through the above comparison, you can reasonably choose galvanized welded pipes or seamless galvanized pipes according to specific usage requirements.