Welded vs seamless steel tube: a selection guide

Welded and seamless tube: two processes, two applications

Steel tube is manufactured mainly by two routes. The seamless tube is obtained by piercing a solid bar while hot, with no longitudinal seam. The precision welded tube starts from steel strip that is formed and induction-welded, then calibrated and, in most cases, cold-drawn to the final size. Both yield high-quality steel tubes, but their performance and cost diverge depending on diameter, tolerance and service conditions.

When to choose seamless tube

The seamless tube is the natural choice for large diameters, thick walls and extreme pressures: drilling lines, oil and gas pipelines, boiler-making or applications where the wall must withstand very high stresses uniformly around the full circumference. In these scenarios, the absence of a weld seam is a real advantage.

When precision welded tube is superior

For small diameters (3 to 25 mm) and tight tolerances, the precision welded tube matches or exceeds the seamless one, and does so at a significantly lower cost. Modern induction welding, together with calibration and cold drawing, removes the historical limitations: a reduced inner bead (≤ 0.15 mm or fully removed), an exact diameter to the tenth of a millimetre and a surface ready for direct chrome or zinc plating with no prior polishing. For axles, rollers, mechanisms, small-diameter fluid lines and structures, it is the most efficient solution.

Selection criteria

The decision is not "one is better than the other", but which one fits your application:

• Diameter: below 25 mm, precision welded is more competitive.
• Tolerance: if you need accuracy to the tenth of a millimetre on the inner and outer diameter, the calibration of welded tube guarantees it.
• Finish: bright, pore-free surfaces ready for galvanic treatment are typical of calibrated welded tube.
• Pressure and wall: for extreme pressures and very thick walls, consider seamless.
• Cost and lead time: precision welded offers a better performance-to-price ratio and greater supply flexibility.

Delmàs welded precision

At Delmàs we manufacture precision welded and calibrated steel tube since 1956, specialising in small diameters from 3 to 25 mm and tolerances to the tenth of a millimetre. You can explore our PREMIUM, OPTIM and PRECISE ranges or talk to our technical team to assess the best solution for your application.

Frequently asked questions

Is a welded tube weaker than a seamless one?

In small diameters and with modern induction welding and calibration processes, no. Precision welded tube offers strength and homogeneity fully suited to demanding industrial applications, with the added benefit of tighter tolerances and a better finish.

What tolerances can precision welded tube achieve?

We work to exact diameters down to the tenth of a millimetre, with a controlled inner bead (≤ 0.15 mm) or its complete removal depending on the range.

When should I opt for seamless tube?

When the application requires large diameters, very thick walls or extreme pressures outside the 3 to 25 mm range. For all other precision cases, calibrated welded tube is usually the best choice.