by Bob Moffatt
In this episode, Bob explains the importance of gas shielding and tungsten stick out as It relates to Gas Tungsten Arc Welding (GTAW). He discusses how to properly set your Cubic Feet Per Hour (CFH) as well as how to set post flow and the importance of it.
In the beginning, Bob discusses the correct techniques and how to produce an acceptable weld and how to properly use your post-flow after it has been set correctly. He then demonstrates what happens when the adequate post-flow is not set and discusses how to avoid discoloring your tungsten at the end of the puddle and why it’s an issue.
Often times we say the more the merrier or more is better. That is simply not the case when dealing with shielding gas. An abundant amount of shielding gas coming from the end of the ceramic cup will create what is known as the Venturi effect. This is where you have so much gas coming from the nozzle, that it actually creates a vacuum and can pull outside air into the puddle. We then see that for the case of GTAW more is not better, its actually worse. At the end of the day, you’re just wasting your shielding gas.
We then drop the CFH way below normal, running 5CFH and produce a beauty of a weld complete with linear porosity. This is something you defiantly want to avoid. The old adage “Less is More” does not apply here. In order to shield our weld pool, we need to ensure we are using adequate shielding gas coverage. Too much or too little will yield undesirable results in one form or another.
Now that we understand the importance of the correct flow, we need to discuss the distance of the cup from the tip of the tungsten. Is the same gas flow adequate if we stick the tungsten out further than recommended? No, it’s not. What if we turn the gas up even higher now that we have a longer stick out? Well its defiantly not going to work out well for you that’s for sure. We need to ensure the relationship to our gas flow and our tungsten stick-out work well with one another and get along with each other. Bob’s recommendation is to keep your stick out the same distance as the diameter of your cup. It’s a good rule of thumb and works well for most cases. For instance, if you have a #7 cup, you can safely have a stick out of about a 7/16”.
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