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(with Pics) Welded vs. Seamless Pipes: Exploring 10 Vital Differences for Enhanced Understanding and Identification

Hi, I’m Max Shi, the CEO of tytsteel.com. With more than 10 years of experience in OEM/ODM steel pipe, I’d love to share with you the valuable knowledge related to steel products from a Chinese supplier’s perspective. Hope you like this article, and please share it or subscribe to our newsletter.

Table of Contents

I’m Max. Today we are going to talk about:

  1. 10 most important differences between seamless and welded pipes
  2. how to tell seamless pipe from welded pipe

What is the difference between welded and seamless pipe?

1. Manufacturing Process:

Seamless Pipe: Seamless pipes are produced by steel mills through a series of processes such as heating and perforation to achieve the desired dimensions.

Welded Pipe: Welded pipes are created by bending and shaping steel strips or plates to predetermined specifications, followed by welding. As a result, welded pipes have a visible weld seam on their surface.

2.Presence of Seam:

Seamless Pipe: No seam is present along the entire length of the pipe.

Welded Pipe: Clearly visible longitudinal or spiral seams are present.


Seamless Pipe: Generally stronger as it lacks the weaknesses introduced by welding.

Welded Pipe: The welded region may have welding defects such as porosity, slag inclusions, etc., which can create weak points and stress concentrations, potentially affecting the overall strength of the welded pipe. This can result in a slight reduction in the strength of the welded region.

Our company provides a laboratory with free testing services for properties such as tensile strength, yield strength, impact toughness, etc.


Seamless Pipe: Seamless steel pipes have superior characteristics, but manufacturing costs are naturally higher.
Welded Pipe: Typically more cost-effective.

5.Production Rate:

Seamless Pipe: Seamless steel pipes are primarily produced through the hot rolling process, resulting in a relatively lower production rate.
Welded Pipe: Welded steel pipes have a simple production process, leading to higher production efficiency.

6.Size Range:

Seamless Pipe: Offers larger sizes and specifications.
Welded Pipe: Provides a wider range of size options. For specific ranges, please refer to our product catalog.

7.Surface Treatment:

Seamless Pipe: As the name suggests, seamless steel pipes have no weld seams. They are produced using round billets, which are perforated and processed through cold rolling, cold drawing, or hot extrusion. The pipes have a smooth internal surface.
Welded Pipe: Due to welding, there is generally a weld seam on the inner wall of the pipe.

8.Quality Control

Seamless Pipe: The raw materials used in seamless steel pipe production, such as continuous cast round billets and rolled (forged) round steel, play a crucial role in ensuring pipe quality. Factors include steelmaking level, casting and cooling processes, and shaping quality. Measures are taken to reduce non-metallic inclusions. Additionally, deviations in the appearance of billets, such as straightness, diameter, and ovality, directly impact perforation quality, leading to quality defects.

Seamless tubes with internal folding due to center loosening
Seamless tubes with internal folding due to center loosening
Seamless pipe cracks caused by inclusions
Seamless pipe cracks caused by inclusions

Welded Pipe: Our factory employs welders with over ten years of experience, ensuring strict control of preheating and heat treatment temperatures for each welding joint. High-pressure pipe welding requires attention to non-destructive testing of the root quality. Many processes require careful monitoring and control.


Seamless Pipe: Offers enhanced performance, especially in terms of pressure-bearing capacity, making it suitable for critical applications such as high-pressure and high-temperature environments, liquid transport, liquid support, and the transportation of petroleum and natural gas pipelines.

Welded Pipe: Commonly used in cost-sensitive non-critical applications, such as mechanical manufacturing, steel structure engineering, power engineering, and building construction.

10.corrosion resistance:

Seamless tubes: Higher reliability and corrosion resistance due to seamless construction.
Welded pipes: Welded areas can be a starting point for corrosion and require additional corrosion protection. Such as adding a layer of zinc to the steel pipe. Galvanized Steel Pipe Galvanizing increases the corrosion resistance of the steel pipe and extends its service life.

Want to learn more about zinc coating. You can check out this article by clicking: 2024 About Zinc Coating: 5 Things You Need to Know

The above is the main difference between seamless pipe and welded pipe. But with the advancement of technology, some welded steel pipe after treatment can also achieve the same pressure resistance value, and even from the appearance, many steel suppliers will give the welded steel pipe to do to remove the welding bar treatment, basically with the naked eye is difficult to distinguish. Therefore, when purchasing steel pipe, we must pay attention to the distinction.

How to distinguish seamless pipe and welded pipe?

Corrosion Method:

In the process of distinguishing between welded steel pipes and seamless steel pipes using the corrosion method, grinding treatment should be applied to the welded seam of the processed welded steel pipe.
After grinding, visible traces of the grinding should be observed. Subsequently, the end face of the welded seam should be polished with sandpaper and treated with a 5% nitric acid alcohol solution.
If a distinct weld seam appears, it can be confirmed that the steel pipe is a welded pipe.
In contrast, there is no obvious difference in the end face of the seamless steel pipe after corrosion.

If you have any question about purchasing steel please feel free to contact our business manager, she will give you a perfect solution.

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