An overview of weld discontinuities

The main concern with any kind of welded tube should be the quality of the welding. There is the chance for all kinds of different flaws. Of them, discontinuities are one of the worst. We want to look closer at this topic here so you know what they are and the five major types. Then, if you want to order high quality ERW steel tubes in the West Midlands, you can speak to us.

What are discontinuities?

ERW steel tubes West MidlandsA discontinuity is anything that interrupts the structure of a material. It ensures that the mechanical, physical, or metallurgical properties of a material are not homogeneous. This lack of homogeneity can result in major issues in some cases.

There is an important thing to note here though. Generally there is a level of discontinuity that is acceptable. As long as the part can meet the minimum acceptance standards for its use, there is no issue. However, if the discontinuities mean the item does not comply with the standards, it becomes a defect and the only option is to reject it.

It is also crucial to think about the fact that a weld may have several different types of discontinuity. Separately they may not cause issues. However, the accumulation can result in a defect.

The five types

As we said above, there are five common discontinuities. Let’s look at them before you order ERW steel tubes in the West Midlands.


The first issue is pores in the metal. They are tiny bubbles or pockets that appear in the weld due to gas entrapment. Because the gases can’t escape when the weld solidifies, it creates the porosity.


Easily the worst discontinuity is cracks. It is the most self explanatory too. The problem is so many different things can cause cracking. It could be stress concentration or anything that has an impact on the ductility.

Incomplete fusion

Next up is a discontinuity where the weld metal and fusion face or weld bead don’t properly fuse. So, there is literally a point where the sides aren’t joined properly. It tends to happen because the temperature of a base metal or deposit is too low so it doesn’t hit its melting point.

Incomplete joint penetration

This issue is something people often confuse with the one above. However, it is very different. What happens here is the weld does not extend through the entire thickness of the joint. Typically, the discontinuities happen because of poor joint design, set up and preparation.

Poor weld profiles

Finally, there could be a problem because the profile of the weld itself is wrong. What we mean here is the shape and form. It includes everything from height to thickness. There can be different profile issues, including overlaps and undercuts.

Choose the best ERW steel tubes in the West Midlands

Ordering tubing only to then find it is low quality because of discontinuities is a massive headache for businesses. It can cause big delays in projects, especially if they decide to reject it and then have to wait for new tube. Even if they use it, there is a risk that over time a discontinuity could become a flaw. The best thing to do is order high quality tubes to begin with.

Union Steel Tubes is a great company to work with in this regard. We prioritise quality, even having ISO 9001 certification. As a result, clients can trust us to make sure we only supply products that meet the relevant standards.

So, if you want to purchase ERW steel tubes in the West Midlands, we are the go to local expert. Get in touch to learn more or browse a selection of sizes and services on our website.