Small Diameter Welded Pipe

The small-diameter welded pipe is also called small-diameter welded steel pipe, which is a steel pipe made by welding a steel plate or a strip steel after being crimped. The production process of small diameter welded pipe is simple, the production efficiency is high, there are many varieties and specifications, and the equipment cost is small, but the general strength is lower than that of seamless steel pipe. Since the 1930s, with the rapid development of continuous production of high-quality strip steel and the improvement of welding and inspection technology, the quality of welds has been continuously improved, and the variety and specifications of small-diameter welded pipes have been increasing and replaced in more and more fields seamless steel pipe. Welded steel pipe is divided into straight seam welded pipe and spiral welded pipe according to the form of weld.

The blanks used for small-diameter welded pipes are steel plates or strips, which are divided into furnace-welded pipes, electric-welded (resistance-welded) pipes, and automatic arc-welded pipes due to their different welding processes. There are two types of welded pipe: straight seam welded pipe (LSAW/ERW) and spiral welded pipe (SSAW). Because of its end shape, it is divided into round welded pipes and special-shaped (square, flat, etc.) welded pipes.

The production process of small-diameter welded pipe is simple, high production efficiency, low cost and rapid development. The strength of spiral welded pipes is generally higher than that of straight seam welded pipes. Welded pipes with larger diameters can be produced from narrower billets. Welded pipes with different diameters can also be produced with billets of the same width. However, compared with the straight seam pipe of the same length, the weld seam length is increased by 30 to 100%, and the production speed is lower. Therefore, the smaller-diameter welded pipes are mostly straight seam welded, and the large-diameter welded pipes are mostly spiral welded.

Steel Pipe Size & Specification:

General specifications of small diameter welded pipe:

1. Outside Diameter Range (OD)
Welded pipe offers greater flexibility in specifications for small diameters, and is particularly adept at producing extremely thin pipes.
Extremely Thin Range: Available as small as 0.5mm to 1.0mm (e.g., capillary tubing).
Common Range: 10mm to 88.9mm (e.g., common specifications include Φ21.3mm, Φ26.9mm, and Φ33.4mm).
Upper Range: Easily covers pipes up to 114mm and larger.

2. Wall Thickness Range (WT)
The wall thickness of welded pipe is limited by the thickness of the raw material strip steel, and very thick wall thicknesses are generally not produced.
Extremely Thin Wall: Available for very thin pipes, such as 0.3mm (much thinner than the limit of seamless pipe).
Common Wall Thickness: 0.5mm to 3.0mm (e.g., common wall thicknesses for 25mm welded pipe are 1.2mm, 1.5mm, and 2.0mm).
Limitations: Small-diameter welded pipe with a wall thickness exceeding 4 mm is difficult to economically produce.

Representative standards for small-diameter welded pipe:

ASTM A53: Seamless and welded steel pipe.
ASTM A269: Austenitic stainless steel seamless and welded steel pipe.
EN 10305-1: Welded steel pipe for precision applications.
GB/T 3091: China's national standard for welded steel pipe for low-pressure fluid transportation.

Note: The small-diameter welded pipe is welded with strip steel, so its status is not as high as that of the small-diameter seamless pipe.

Read more: Types and Uses of Welded Steel Pipe