Seamless vs Welded pipe

Seamless pipes (SMLS) and welded pipes are two common types of steel pipes. They differ significantly in terms of manufacturing processes, performance characteristics, and applicable fields. The following are the main differences between seamless and welded pipes:

1. Manufacturing process

 Seamless pipe is manufactured by heating, punching and rolling a steel billet, resulting in a pipe with no welded joints.

This method ensures smooth and uniform surfaces both inside and outside the pipe, providing better fluid flow and corrosion resistance. Welded pipe, on the other hand, is made by rolling steel plates into a tube shape and joining them by welding, resulting in one or more long welds along its length. In some applications, these welds may create weaknesses that require additional corrosion protection.

2. Wall thickness

The precision of welded pipes is high, with a usually thin wall thickness, while seamless pipes have lower precision and a relatively thick wall thickness.

3. Price

Seamless pipes are more costly than welded pipes due to the more complex production process and higher costs associated with seamless steel pipes.

4. Performance characteristics

Seamless pipes perform better in high temperature, high pressure, and corrosive environments due to the absence of welded joints.

They are suitable for applications requiring high strength and corrosion resistance, such as oil and gas transmission, chemical industry, and high-pressure boilers. The performance of welded pipes often depends on the quality of the weld. Welded joints can be a potential source of corrosion and weakness, but with proper welding techniques and corrosion protection, these problems can be reduced. Seamless pipes are superior to welded pipes in terms of corrosion resistance, pressure bearing, high temperature resistance, and other properties.

5. Applicable fields

Seamless pipes are commonly used in applications that require high reliability and safety, such as nuclear power plants, high-temperature and high-pressure vessels, and chemical equipment due to their high-performance characteristics. Welded pipes, on the other hand, are suitable for general engineering and low-pressure applications, such as building structures, hydraulic transmission, and general piping systems. They are typically more affordable.

Seamless and welded pipes have different advantages in various applications. The selection of pipe materials should consider engineering needs, performance requirements, and cost factors to determine the most suitable type of steel pipe for a specific project.