Seamless Versus Welded Stainless Steel

Stainless Steel pipes and tubes are strong and sturdy, making them suitable for pressure applications. Many water, chemical, pulp, oil, gas, petrochemical, energy, and paper industries depend on Stainless Steel pipes and tubes. Initially, all Stainless Steel tubular products were seamless. Now, there are many choices in the market.

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a Seamless Stainless Steel Exhaust Pipe by Shanghai Metal Corporation

For instance, welded pipes and tubes are popular in the market because of its many advantages. Using welded tubes and pipes is more cost effective than the seamless alternative. In addition, welded pipes and tubes have a narrower tolerance for wall thickness and better concentricity. Welded pipes and tubes can be created with a larger diameter and longer length. Unlike seamless pipes and tubes, the surface of welded pipes and tubes can be checked prior to being made. In general, welded pipes and tubes are more available both from distributors and mill production companies. Consequently, welded pipes and tubes are able to be delivered faster and cheaper.

welded pipes by Shanghai Metal Corporation
welded pipes by Shanghai Metal Corporation

In contrast, seamless pipes and tubes are still widely used. You can get a wider variety if you purchase seamless pipes and tubes. Seamless tubes are produced in highly specialized grades. There may be some heavy wall sizes that are too thick to form to the required diameter. Thus, the material cannot be made through welding. You will need to rely on seamless pipes and tubes, which are commonly available with very thick walls. Compared to welded pipes and tubes, the seamless alternative may have the advantage of having a heat-affected zone. Some argue that seamless pipes and tubes resist corrosion better than welded pipes and tubes. Furthermore, seamless pipes and tubes have a more homogeneous grain structure compared to the welded alternative.

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An example of a thick, seamless tube

Whether you prefer welded or seamless, the two products generally complement each other. In fact, most places utilize both. Even if the pipe or tube is welded or seamless, they are likely to be connected with circumferential welds to each other, fittings and flanges. Take into considerations the advantages of utilizing welded tubes and pipes and the advantages of utilizing seamless tubes and pipes before selecting the best material for a specific application.

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Written by:

Alexis Ty // SMC Editor

International Trade and Marketing Specialist

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Not Just Hollow Cylinders

In the Steel manufacturing industry one often hears terms such as steel pipes or steel tubing.  Most people would just think, they are just hollow cylinders, but what they don’t know is that there are a couple differences between a steel pipe and steel tube.

For instance, a pipe is a vessel and a tube is structural.  The pipe is measured by ID and a tube is measured by OD.  Tubing is more used in structures so the OD is the important number.  The strength of a steel tube depends on the wall thickness.  Therefore, tubing is specified by the diameter and the wall thickness which is often specified as a gauge.  Steel tubes are used in structural applications and will most likely be seam welded.

Pipes are normally used to transport gases or fluids so it is important to know the capacity of the pipe.  The internal cross-sectional area (ID) is important because it measures the inside diameter of the pipe.  Since the outside diameter of a single nominal pipe size is kept constant, the inside diameter of a pipe will depend on the “schedule” or the thickness.  The actual thickness of a pipe varies with the size of the pipe.  The size usage of pipes apply to all plumbing, natural gas, heating oil, and other piping use in building construction.

So in the manufacturing industry, the tolerance of pipes are looser compared with tubes and they are often less expensive to produce. Tubes on the other hand have a higher tolerance,  therefore are often more expensive to produce than pipes.

Remember, a hollow cylinder has 3 important dimensions:

  • The outside diameter (OD)
  • The inside diamter (ID)
  • The wall thickness (WT)

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