What is the difference between seamless and welded steel pipe?

The main difference between seamless and welded steel pipe lies in their manufacturing process.

Seamless steel pipes are made from a solid cylindrical billet, which is heated and then stretched and pierced to create a hollow tube. This process ensures a consistent diameter and wall thickness along the entire length of the pipe, resulting in a smooth and continuous product without any welded joints.

Welded steel pipes, on the other hand, are manufactured by joining or welding two or more pieces of steel together. There are various methods for welding, such as electric resistance welding (ERW), submerged arc welding (SAW), and seamless welding. The welding process introduces a welded joint, which can be either longitudinal or spiral, depending on the specific manufacturing method used.

In terms of characteristics, seamless pipes offer higher strength and pressure ratings due to their uniform structure and absence of welded seams. They are generally preferred for high-pressure applications, such as oil and gas pipelines. Welded pipes, while not as strong as seamless pipes, are more cost-effective and suitable for less demanding applications, such as plumbing and structural purposes.

Ultimately, the choice between seamless and welded steel pipe depends on factors like the intended application, required strength, budget, and availability.