What Is Welding Undercut?

With welding being used in so many different industries today, it’s no wonder that new welding techniques are continuously being developed. One such technique is welding undercut, which is becoming increasingly popular due to the fact that it is both economical and efficient. In fact, surveys estimate that welding undercut is employed in more than 60% of all businesses that involve welding.

Now, you may be wondering: What is welding undercut and how can it benefit my business? In this article, we’ll take a closer look at the topic of welding undercut, from its definition to how it works and its advantages.

With this information, you’ll be better prepared to make informed decisions regarding your welding processes.

What is Welding Undercut?

Welding undercut is a type of welding defect that occurs when an over-egged weld causes the metal to be melted more than required, leaving a “scoop” in the metal when it solidifies again. Undercut is difficult to repair, making it important to identify the defect before the weld is cooled.

Causes of Welding Undercut

Welding undercut may occur for a variety of reasons, including:
  • Inadequate joint design
  • Incorrect heat input
  • Inadequate weld size
  • Inappropriate welding technique
  • Improper fit up of the two weld components

Welding undercut Inspection

Regular inspection of welds is important to identify any defects. When inspecting for undercut, it’s important to inspect an actual cross-section of the weld.

The undercut can be difficult to identify with a surface examination. Common methods used to inspect a cross-section of a weld are:

  • Coupon test specimen
  • X-ray examination
  • Carbon arc test
  • Helium Leak Test

Welding Undercut Repair

Welding undercut can be difficult to repair.

The most common approach is to grind down the undercut to a uniform thickness and make sure that it does not exceed the thickness limits specified in the codes. This approach is effective for small sections of undercut. However, for larger sections, the material must be removed using an oxy-arc technique or a flame-cutting technique.


Welding undercut is a type of weld defect, which can be difficult to repair. Therefore, it is important to identify and inspect for undercut, as early as possible. Various techniques can be used to inspect for welding undercut including coupon test, X-ray examination, helium leak test, and carbon arc test.

If undercut is detected, repairing it can be difficult and the material must be removed manually.



thorlabs. com/tutorials/what-is-welding-undercut-in-weldinghttps://www. tracto-technik. de/en/blog/undercut-in-welding-why-it-occurs-and-how-to-avoid-it

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