How do I know if my pipe is seamless or welded?

Concepts and characteristics of seamless steel pipes and welded steel pipes:
Seamless steel pipe (SMLS) means that there are no seams and the whole is a uniform hollow steel pipe. Compared with welded steel pipes, seamless steel pipes have the advantages of higher strength, toughness and corrosion resistance, and are widely used in various fields.

Welded steel pipes are made by connecting multiple steel plates into one pipe through arc welding or gas welding. There may be some defects such as welds or bubbles inside.

How do I know if my pipe is seamless or welded?

1) Appearance features

Seamless steel pipe: 

a. Smooth surface: The surface of seamless steel pipe has no obvious unevenness, burrs, cracks and other defects;

b. Uniform cross-section: The seamless steel pipe has a circular cross-section, uniform diameter, and consistent thickness;
c. No oxide scale: There are no signs of rust, oxide scale, etc. on the surface of the seamless steel pipe.

Welded steel pipes have certain welds or melt marks inside or outside the steel pipe, which usually leave traces of welding and slag particles, and the surface of the steel pipe is relatively rough.

2) Detection means
In addition to observation, seamless steel pipes can also be effectively identified through the following detection methods:

1. Magnetic detection: The seamless steel pipe material is relatively pure and has good magnetic permeability. Under the action of a magnetic field, it will produce obvious magnetization phenomenon. It can be detected by a magnetic flaw detector or a hand-held magnet.

2. Hand feeling detection
Compared with welded steel pipes, seamless steel pipes are smoother, have no edges, burrs, etc., and have a more even feel.

3. Internal defect detection
Internal defects of seamless steel pipes, such as inclusions, bubbles, cracks, etc., are usually detected through ultrasonic testing or radiographic flaw detection.

4. Pull out test
The pull test is to fix both ends of the steel pipe, and then pull the middle part to observe whether cracks appear in the steel pipe. Seamless steel pipes usually do not show obvious deformation and cracks after a pull-out test. Welded steel pipes are prone to cracks at the welded joints.

5. Stress test
Pressure testing is a method of hydrostatically testing steel pipes. The steel pipe is usually filled with water and a certain pressure is applied to detect whether there is water leakage in the steel pipe. Seamless steel pipes can usually withstand higher pressures and are less prone to leaks. Welded steel pipes often leak at the welded joints.

3) Application identification
1. The overall performance of seamless steel pipes is better, and there are no internal defects such as welds, so it is usually used in high-pressure, high-temperature and important mechanical equipment.
2. Welded steel pipes are suitable for low-pressure, small-diameter pipes and some buildings, bridges and other fields.

Precautions:
1. First, look for manufacturers with high credibility to avoid buying fake and shoddy products;
2. Before purchasing, you must understand the material, specifications, performance and other parameters of seamless steel pipes;

3. During use, the seamless steel pipe must be protected from external impact, wear, corrosion and other damage.

Tips: ASTM A106 seamless pressure pipe (also known as ASME SA106 pipe) is commonly used in the construction of oil and gas refineries, power plants, petrochemical plants, boilers, and ships where the piping must transport fluids and gases that exhibit higher temperatures and pressure levels.

Go here to learn more: Schedule 40 pipe