Small diameter welded pipes, also known as small diameter welded steel pipes, are steel pipes that are焊接 from steel plates or strips. These pipes offer advantages such as simple production processes, high production efficiency, a variety of types and specifications, and minimal equipment. However, their overall strength is lower than that of seamless steel pipes. Since the 1930s, with advancements in strip steel rolling and welding inspection, the quality of welds has continually improved, leading to a growing variety and specification of small diameter welded pipes. Seamless steel pipes are being increasingly replaced in various fields. Welded steel pipes are categorized by the weld type into straight seam and spiral seam pipes. The billets used for small diameter welded pipes are steel plates or strips. Depending on the welding technique, they are classified into furnace-welded, electric-welded (resistance welding), and automatic arc-welded pipes. Due to their different welding forms, they are further divided into straight seam and spiral seam pipes. Small diameter welded pipes are also categorized by their end shape into round welded pipes and non-standard (square, flat, etc.) welded pipes.

Small diameter welded pipes offer advantages such as simple production processes, high production efficiency, low costs, and more. The strength of spiral welded pipes is generally higher than that of straight seam welded pipes. They can produce pipes with larger diameters and narrower blanks, as well as pipes with different diameters but the same blank width. However, compared to straight seam pipes of the same length, small diameter welded pipes have longer weld lengths, resulting in lower production speeds. Therefore, straight seam welding is more commonly used for small diameter pipes, while spiral welding is more prevalent for small diameter pipes.