What Is Undercut In Welding

What Is Undercut In Welding?

An undercut is a surface and subsurface flaw caused by grooves in the parent metal area. Instead of improving joint strength, like other flaws, it adds weak spots frequently propagated structural failure. Weld quality ensures efficiency and safety during production.

The undercut flaw is commonly found in lap, butt, and fillet welds. It is caused by incorrect welding techniques, incorrect electrode angle, or incorrect welding current. The undercut can also be caused by excessive heat input during welding, which melts the base metal and creates a groove.

The undercut flaw is a serious issue because it decreases the strength of the weld joint. The flaw can cause the weld to crack or break under load. The flaw can also cause the weld to fail.

Undercuts are typically repaired by removing the metal around the undercut and rewelding the area. One must repair correctly to avoid further damage to the joint.

Cause of undercut in welding

Following are the reason for undercuts in welding

  • High Rates of Electrode Movement

If the Electrode is moving too fast, it can cause an undercut. The molten metal doesn’t have time to fill the weld joint, resulting in a shallow or incomplete weld.

  • Incorrect Electrode Tip Angle

The angle of the electrode tip concerning the workpiece also plays a role in preventing undercuts. If the angle is too acute, it can cause the Electrode to dig into the workpiece, making it difficult to maintain a consistent arc length. That will result in an undercut.

  • Insufficient Welding Current

Insufficient welding current cause Poor weld penetration and automatically leads to an Incomplete fusion of the filler metal to the base metal. Resulting in Poor wetting action of the filler metal on the base metal. Leading Porosity in the weld bead causing weld undercut and Poor mechanical properties of the weld joint.

  • Dirty or Oxidized Electrodes

If the Electrode is dirty or oxidized, it can also cause undercuts. That is because the dirt and oxide can prevent the arc from forming properly. As a result, the weld will be shallow and may not fill the entire joint.

  • Excessive Arc Length

It may cause deforming of the mechanical properties causing an undercut of the metal surface.

  • Use of the Wrong Electrode

It is the major cause faced by beginners. Using the wrong Electrode can cause undercuts. The wrong Electrode can affect overall weld quality causing deformation

  • Improper Welding Technique

Not using the proper welding technique is another major cause of undercuts. That includes not maintaining a consistent angle or feeding the Electrode too slowly. Both of these can result in an uneven weld that is more likely to have undercuts.

  • Excessive Heat Input during Welding

Excessive heat input during welding can cause the metal to melt too quickly. As a result, the weld will be shallow and may not fill the entire joint. That can lead to undercuts.

  • Poor Joint Fit-Up

If the joint is not fit together properly, it can also cause undercuts. That is because the metal will not be able to fuse correctly. As a result, the weld will be shallow and may not fill the entire joint.

  • Inexperienced Welder

An inexperienced welder can cause undercuts in weld by balancing the proper way to weld. Sometimes inexperienced welder uses unnecessary ways, including heat that causes undercuts.

  • Dirty or Contaminated Welding Surface

If the welding surface is dirty or contaminated, it can cause undercuts. That is because the dirt and contamination prevent the arc from forming properly. As a result, the weld will be shallow and may not fill the entire joint.

  • Contaminated shielding gas

If the shielding gas is contaminated, it can also cause undercuts. That is because the contaminants can prevent the arc from forming properly. Also, the specific heat of gas causes the abbreviation of the weld properties.

The solution to causes of undercuts in welding

one can take the following measure to avoid undercuts in welding:

  • The angle of the Electrode at 30-45 Degrees

The electrode angle should be between 30 and 45 degrees to the horizontal surface for optimal performance. That would give a suitable placement for molten metal to flow smoothly and evenly. It’s also feasible to perform activities at this angle rather than vertically, although not as easily.

However, you must balance the angle of the Electrode according to the type of welding used. For example, you should aim the gun at 10-15 degrees in wire welding. As a result, tilting the Electrode allows for an angle of tilt when working in a vertical posture.

  • Balanced travel speed

The travel speed is defined as the rate at which the Electrode moves across the surface of the workpiece. It is generally measured in inches per minute (IPM). You must balance the travel speed with the welding current to ensure proper weld penetration and avoid weld UNDERCUTTING. If the travel speed is too fast, the weld bead will be shallow and may not fill the joint. That can lead to undercuts. If the travel speed is too slow, the weld bead will be too deep and may cause the metal to melt too quickly. As a result, the weld will be shallow and may not fill the entire joint. That can lead to undercuts. You should set the travel speed to flush the weld bead with the workpiece surface.

  • Welding on a levelled platform

A levelled platform while welding is crucial since an uneven one can lead to undercuts. A sloped or tilted work surface can cause the molten metal to flow in the wrong direction, resulting in an uneven weld bead.

  • Maintaining current along with voltage.

When welding different materials, knowing what will be welded is important. Remember that higher currents are needed for stainless steel and mild steel welding than for aluminium. The type of Electrode would also differ. To ensure the welding is done properly, you must automate current and voltage control while working.

  • Using pure shielding gas

Shielding gas free of impurities ensures that the weld’s quality is not jeopardized. On the other hand, slag and porous welds are frequently formed due to this process, leading to weak areas and undercurrent. To select shielding gas correctly, consult with your local welding supply shop.

  • Clean metal surface

The best way to clean a metal surface is to use a wire brush. For best results, use a new brush for each welding session. That will remove any dirt, grease, or other contaminants that could prevent the arc from forming properly.

  • Correct welding technique

Different metals are welded with different welding techniques. Each shows the best result with the respective type of welding. So to avoid undercuts, choose the welding technique according to your metal.

Conclusion :

In conclusion, it is necessary to avoid undercuts while welding. Some of these include using the correct angle of the Electrode, maintaining a balanced travel speed, and ensuring that the metal surface is clean. Following these tips, you can weld without worrying about undercutting your work. If you are still facing the problem, it is better to consult a professional. We hope that this article has helped you a lot.

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