by Jason Becker
Wormhole porosity can be a real pain, especially since you cannot see it while you are welding. It only rears its ugly head once you have chipped off the slag.
Wormhole porosity typically occurs during the flux cored arc welding process (FCAW) on both self shielded and gas shielded applications. The common cause of this condition is the nitrogen getting trapped as it tries to escape the puddle during the solidification process. There are three primary reasons why you would get wormhole porosity and we are going to cover them so that you can avoid getting these weld discontinuities all together.
The first thing we we want to look at is the condition of our electrode and make sure it has been properly stored. Basically if its in its original packaging on wrapped in a plastic bad and stored in a dry room out of the elements you should be fine. For instructional purposes only, we had Mancub leave out a roll of flux cored wire in the Florida elements for a couple weeks. Now, if you know anything about Florida, the outside conditions are far from ideal for electrode storage. With this wire, we got exactly what we were looking for. Having moisture in the wire, or using wire that has been allowed to collect surface contaminants will almost ensure that you get wormhole porosity. It is best to store these wires according to the manufacturers recommendation as this will help you eliminate improperly stored electrode from the equation. You will see in the video above, the results of improperly stored electrode vs. improperly stored electrode. We ran both wires on the exact same settings and used the same welding techniques.
Now that we know that we are working with a properly stored electrode, we need to dissect our technique to see if that is the culprit of the wormholes we are experiencing. The number one cause of wormhole porosity in my opinion is improper contact tip to work distance. Most people find themselves really burying the wire into the puddle much like they would with a short circuit MIG application. The recommended contact tip to work distance for most Flux Cored applications in 3/4"-1" and in some cases up to 1-1/4". It will vary depending on the manufacturer of the electrode. As you can see, even at its minimum distance, it is still twice as far, as compared to short circuit. But out of habit, many people just get really close with the tip and stay there, then they wonder why they are getting wormholes in their welds. Well, the flux needs time to preheat and that extra distance allows it to do just that.
In addition to contact tip to work distance, we also have to ensure our voltage is set correctly, too low of a voltage will cause wormhole porosity as well. Its usually an indication of needing to add 1.5-2 volts and that usually corrects things as long as the wire is clean and the contact tip to work distance is within the recommended distances.
So there you have it, the three most common causes of wormhole porosity and how to remedy them. Always ensure you are storing your electrodes and wires according to the manufacturers recommendation, maintain the correct stick-out, and be sure that your settings are correct. By checking these 3 things, you should be able to mitigate most of, if not all of your porosity issues. Until Next Time, Make Every Weld Better Than Your last.