Welders Galore

Welders Galore

What is Welding Burn Through and How to Prevent It

Welding burn through is a common welding defect that can cause a weld failure and rejection. New welders are prone to causing a burn through welding defect as they learn. But, with a little extra care and some essential knowledge, this defect can be prevented, and we will explore this topic in this brief guide.

What Is A Burn Through Welding Defect?

Prevent Burn Through In Welding

So, what is a welding burn through defect? This occurs when the weld penetration is too deep and reaches the weld root. The base metal thickness is melted entirely, and this is why this defect is also referred to as a melt-through. The burn through creates a hole in the weld joint on or near the seam. This is very common in thinner materials and work-pieces that have low thermal conductivity. The weld joint strength is degraded because even small holes are prone to deformities and cracking under load.

An immediate rejection should be expected when a burn through is produced during pipe welding. This is understandable because any holes will cause leaks in the pipe joint. The aesthetic appeal of the weld is also ruined by a burn through, and this is an important consideration for many clients. If you take steps to avoid burn through defects your welding will improve, and your work will be in high demand.

10 Causes of Burn Through In Welding?

There are ten reasons why a burn through welding defect is produced that can be linked to a wide variety of parameters. It’s important to exercise care during the setup and execution to prevent burn through and many other errors. Let’s take a closer look at the common causes of burn through in more detail:

1.    Welder Set at a High Amperage

The most common cause of welding burn through is excessive heat input into the weld joint, which is dependent on the amperage. If the amperage (current) is too high, the heat input is greater, and holes are burned in the weld. Before you begin, check the amperage and use the recommended settings for the job.

2.    The Person Welding is moving at a Slow Travel Speed

The electrode travel speed can affect the heat input; the longer it’s kept in one place, the higher the heat input is at that point. When the heat input is too high, the result is over-melting and burn throughs. The recommended travel speeds for jobs can be found on charts and in catalogs. But, these are not particularly useful because it’s hard to track your speed as you’re welding.

The only way to prevent slow travel speeds is with focus, practice, and experience. If you can see frequent burn throughs, it’s a sure sign that you’re welding too slowly.

3.    Improper Joint Penetration Due to Poor Metal Preparation

Poor joint preparation is a common cause for burn through welding defect issues. Using the proper techniques and parameters is not helpful if the preparation is not good. There are two main categorizations for joint preparation, grinding too much base metal and insufficient base metal cleaning. We will cover this in more detail next to ensure that you’re ready before you even strike an arc.

4.    Grinding Too Much Base Metal

Before welding begins, it’s expected that the base metal edges are beveled by grinding. This provides a groove for the filler material to form a strong weld joint. But, it’s important to take care when grinding because the bevels can be too deep. If the bevel edges have been ground down too far this makes the joint prone to a burn through.

5.    Insufficient Base Metal Cleaning

All base metals must be properly cleaned before welding commences. Sheets of aluminum and galvanized steel have a protective layer that is highly reactive when the surface temperatures are high. Aluminum oxide has a thin protective film to resist corrosion, but this coating creates spatter and impurities when it reacts with the weld pool. Controlling the weld pool is difficult because the reaction moves it away from the weld zone.

Burn through occurs when the heat is transferred to the base metal. Thorough base metal cleaning is essential to avoid these issues; a small grinder or a wire brush is usually sufficient to remove thin films, layers, and coatings,

6.    Incorrect Arc Length

The arc length is the distance between the electrode tip and the work-piece. If the electrode is too far from the work piece, the arc is longer. This arc is discontinuous and unstable, and excessive spatter may be produced. The heat disposition is difficult to manage, and the arc movement is harder to control.

This causes excessive melting, and a burn through is more likely. If the electrode is too close, this can raise the current, and this will also cause a burn through. It’s important to find the lower and upper limits for the arc length and work within this range to prevent a burn through welding defect.

7.    Steep Travel Angle

The travel angle is the tilt that a welder places on the stick or electrode as they weld. This angle can affect the heat input, and an angle that’s too steep will focus too much energy on the weld pool. If the angle is too shallow, this can distribute the heat over a wider area, and finding the proper angle is essential to prevent a burn through.

8.    Poor Welding Technique

There are two main mistakes that new welders make:

First, they drag along the weld seam as they bend the stick towards or away from the travel direction. This is also known as “pulling the bead,” and it’s a common burn through cause. Dragging the weld seam causes some of the energy to be directed to the metal that is going to be welded. The weld pool gets some heat, but pre-heating in the metal that the welder is moving towards may occur. This raises the heat input in the joint, and a burn through is more likely.

Second, new welders want to create the best-looking welds to impress, and they move the stick in patterns to make their weld joints neat. This is a useful technique to learn, but it can be overused, and there are some drawbacks. Weaving the stick means more time spent on each successive pass, and this increases the heat in the weld joint. If the heat input is higher, the risk of a burn through rises.

9. Wrong Welding Type

There are many welding processes, and finding the right one for any given job is important if you want to prevent burn through and other errors. High-intensity welding types rely on larger heat input, and this is why many welders prefer MIG or other low-intensity processes when they work on thin workpieces. Choosing the best welding process for the job will come naturally with practice, more knowledge, and on-the-job experience.

10. Incorrect Machine Settings

There are a lot of knobs and buttons on welding machines, and many of them are not touched. It may be necessary to change the wire feed speed or amperage for a specific job. But, the polarity and other settings tend to stay the same and this is why it’s important to check before you get to work. If the voltage, polarity, pulse, and other settings have been altered without your knowledge, it’s easy to cause burn through and other defects.

How To Prevent Burn Through In Welding

Welding Burn through

Let’s take a look at six things that you can do to prevent burn through defects:

  1. Apply a clay heat sink to the rear of thinner metals to pull heat away from the weld.
  2. Clean the metal thoroughly to remove films, coatings, impurities, and more.
  3. Grind down poor welds to produce fresh and clean welds that will be stronger.
  4. Grind a bevel on the edges of the workpiece to prepare them for the weld, but don’t go too deep, or burn through can occur.
  5. Keep lubricants off the metal surfaces because they break down during welding and cause hydrogen to seep into joints.
  6. Degrease joints with a solvent and wipe it dry afterward to remove any remaining impurities that can cause burn through.

How To Weld Thin Metal Without Burning Through

The electrode should be smaller than ¼”, and the rod should not be thicker than the metal. The smaller electrodes work better with low amperage settings and this will prevent burn through.

How Do You Fix Burn Through In Welding?

Even experienced welders make errors, and burn through can occur. But, it is possible to fix burn through, the hole can be sealed with a tack weld, and you can grind off any rough edges. If there are multiple burn through defects, it may be possible to fix them with a second pass.

How To Prevent Burn Through When Stick Welding

The arc must be maintained at a consistent length that’s equal to the electrode diameter. If the arc is longer or shorter, you may experience burn through on the work-piece. When you weld, use a shallow travel angle and maintain this angle across the entire weld joint.

Welding Burn ThroughIn Conclusion

Welding burn through is dependent on a number of variables; fast travel speeds, high current and poor joint preparation can all be contributing factors. Improving your welding technique will certainly help, but it’s important to check the settings before striking the arc. If you experience a lot of burn through, you’re probably welding too slowly, and you’re spending too long in one location.

Burn through is an ever-present problem; experienced welders can create these defects too. But, ultimately, there is no substitute for welding practice, experience, and knowledge. If you make a mistake, learn from it and make a conscious effort to make the next weld joint even better.

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