Undercutting is another sign of imperfect welding, like porosity, that can result in a poor and fragile combination of a particular metal and work-piece. Basically, it leaves a U-shaped dip over the toe of the weld which can be a great concern for any welder in work. There are diversified reasons lie behind this crucial problem which can be easily prevented if sufficient precautions are taken before.
Let’s learn about them:
The Causes Behind Undercutting In Welding
Excessive Heat: The fluctuation in voltage especially high voltage can lead to an unanticipated supply of heat over the weld metal. Consequently, it melts the weld metal or the parent metal and makes the surface rough which can result in serious undercutting.
High or low travel speed: Arc travel speed can play a big role in occurring unexpected undercutting over the weld area. Basically, this happens because of two reasons. One is fast solidification and the other is drainage or mixture of parent metal into the molten metal. When the ark travels fast, it leaves a very peak weld bead because of the quick solidification process. On the other hand, too low travel speed can also result in undercutting.
Contaminated or improper shielding gas: We all know that shielding gas is formed by a combination of some other protective gas with an accurate ratio in order to act as a protective layer against atmospheric contamination. But the metal that is being welded may often need a unique composition of those gases according to its thickness and type. Hence, contrary to this may result in significant undercutting of the weld area.
Wrong use of electrode: Now, the way we use electrodes during performing the welding task may also cause undercutting. Because inefficient manipulation of the electrode may leave an excessive or insufficient amount of molten metal across the weld area which therefore causes undercutting.
Incorrect electrode angle: Do you know incorrect electrode angle is one of the most common causes behind undercutting? Well, let’s make it clear. Incorrect electrode angle can provide more heat to thinner edges which can subsequently result in undercutting. Alternatively, correct electrode angle can provide heat to thicker areas which will ensure strong welding of that particular material.
Wrong welding position: It often occurs when we are welding a horizontal area but subconsciously hold the electrode over the vertical metal which leads to significant undercutting as insufficient filler metal is being put into the joint area.
Using larger electrodes: Sometimes using too large electrodes can create undercutting because it may melt an excess portion of the parent metal other than the joining the edges.
Incompetency of the welder: Now, this is very important as there are many things to consider before performing a welding task. A welder must be aware of the correct size and technique of weaving while joining the two edges otherwise; it may lead to serious undercutting of that particular area. Besides, aggressive weaving style may also cause this defect. Apart from that, the ignorance of considering fast solidification and correct travel speed of the welder may also result in undercutting.
Improper filler metal: Improper or too hot filler metal can cause undercutting as with using a contaminated shielding gas. Using an improper filler metal can cause temperature gradients across the weld area which subsequently results in undercutting.
Inadequate deposit of filler metal: Finally, as we all know there are many types of welding metals that require sufficient supply of filler metal across the joining position. Failing to do this may result in significant undercutting as filler metals are very crucial to ensure the perfect welding between two edges.
Now, it’s time to learn about some of the remedial actions in order to avoid undercutting in welding. Similar to that of porosity, undercutting can also be prevented if the welder is always conscious about the remedial steps that we’re going to share you. If these steps are duly followed, there’ll be less chance of occurring most of the welding defects including undercutting. So let’s learn about them:
Recommended Steps to Avoid Undercutting in Welding
- Effective control of amperage: The first stage in preventing undercutting in welding is to continuously monitor and control the amperage settings. You can set a low or appropriate voltage in a stabilized manner so as to ensure proper heat supply to the joining metals and durable welding of those edges.
- Using proper shielding gas: Now, as we already know that different sorts of metal require a different composition of shielding gases that can have a big impact over causing undercutting. In this case, shielding gases and their ratio composition should be selected according to the type of metal. Besides, you have to make sure the gas is free from any sort of contamination in order to ensure perfect welding.
- Make sure the weld position is correct: The welder should be aware of the correct weld position and use special techniques if necessary while performing a horizontal weld against a vertical joint.
- Use an effective welding strategy: The use of an effective welding strategy especially by performing different weaving techniques can significantly reduce the occurrence of any undercutting in welding. Some of these techniques include crescent, zigzag and curlycue. It controls the heat and ensures strong welding of the edges.
- Correct the angle of electrode: As stated before, using the wrong electrode angle can trigger undercutting whereas using a correct angle can produce a perfect weld bead and ensure a strong combination of that area.
- Use proper size electrodes: Electrode should be selected while taking consider the thickness of the weld metal. You have to make sure the electrode doesn’t heat any excess portion outside the weld area.
- Have a relevant travel speed: If you have gone through the list of reasons that causes undercutting, you will be aware of the fact that this remedial step should appear on the second or third position because of the impact of its application. Both low and high travel speed can cause undercutting and a welder should use a relevant arc speed in order to prevent this welding defect.
- Implement Multi-Run strategy: This is one of the most effective techniques especially in preventing any sort of undercutting as well as under filling of the weld area. This strategy can be executed by making three runs between the joining edges. One is onto the center of the joint while the other two will be performed subsequently over the upper and lower portion adjacent to the center line.
Final Words
Undercutting is one of the several defects in welding which can be easily prevented if sufficient precautions are followed. We believe this comprehensive guide has made you aware of the most common causes behind undercutting in welding as well as how to successfully prevent them by taking some remedial steps.
Thanks for reading the whole post. Being onto the field of welding, our main objective is to always provide detailed information and tips about the welding industry in order to make your fusing task convenient and professional. Stay along with us.
References
https://www.theweldingmaster.com/welding-defects/
https://www.welding.com.au/news/view/how-to-fix-8-common-welding-problems-with-these-easy-steps
https://www.weldpedia.com/2015/05/7-effective-ways-to-prevent-weld-undercutting.html
https://www.bernardwelds.com/the-causes-of-gmaw-flaws–p152072#.XQuactIzZdj
https://en.wikipedia.org/wiki/Welding_defect
https://www.esabna.com/euweb/mig_handbook/592mig5_1.htm
https://www.thefabricator.com/article/testingmeasuring/understanding-weld-discontinuities
