Difference between Seamless Steel Pipes and Welded Steel Pipes

Seamless steel tubes are long steel bars with a hollow cross-section and no joints around the circumference. These tubes, with their hollow cross-section, are extensively used as pipelines for conveying fluids, such as oil, natural gas, coal gas, water, and certain solid materials.

Welded steel pipes, also known as welded tubes, are pipes made by welding steel plates or strips after rolling and forming. The production process of welded steel pipes is simple, with high efficiency, a wide variety of specifications, and requires less capital for equipment. Their strength is lower than that of seamless steel pipes. Welded steel pipes are categorized into straight seam welded pipes and spiral seam welded pipes based on the seam type. Straight seam welded pipes have a simple production process, high efficiency, and low costs, and have developed rapidly. Spiral seam welded pipes generally have higher strength than straight seam welded pipes, allowing for the production of larger diameter pipes with narrower billets and the production of pipes with different diameters using the same width billets. However, compared to pipes of the same length with straight seams, the seam length increases by 30% or more, and the production speed is slower. Therefore, smaller diameter welded pipes mostly use straight seam welding, while larger diameter pipes generally use spiral seam welding.

Difference between Seamless Steel Pipe and Welded Steel Pipe

In general, seamless steel pipes have no visible seams on the outside surface; welded steel pipes have one or several welded seams. There are fewer welded pipes with DN100 or above, while seamless pipes are more common.