TIG WELDING LAP JOINTS

by Jason Becker


Gas Tungsten Arc Welding (GTAW) or TIG welding, can be very difficult for new welders to master, especially without formal training. Today we are going to discuss and demonstrate some proper techniques and drop a few tips to help even the most novice of welders master the lap joint.

As with any welding process we get into, the first thing we need to discuss is the proper protective equipment for the application at hand. Although TIG welding doesn’t generate any sparks, we still want to wear a welding jacket to block out the UV rays produced by the intense arc emitted from the TIG torch. All exposed skin should be covered regardless of what welding process we intend to use and TIG is no exception.


Next, we want to make sure our hands are protected. A good pair of dry leather gloves are my first choice, you want to make sure they fit really well and are appropriate for TIG welding. A big pair of bulky gloves made for Stick welding would be a poor choice as they will not dive you good dexterity to control the filler metal. Gloves made with synthetic fibers like polyester should not be worn as they will not protect the wearer from the heat resulting from the welding process. Synthetic fibers also melt when they come in contact with heat and that’s not something you want to happen while you have them on your hands. A welding cap is also recommended especially for those with thinner hair or the absence of it. Safety glasses are a must and go without saying, but I will say it anyway. Polycarbonate safety glasses should be worn any time you are in a shop or work environment. They will help block UV glare and are also impact resistant. Safety glasses should be compliant with ANSI Z87.1. A quality welding hood goes without saying but something that is rarely discussed is the appropriate shade lens for the task at hand.


For the purpose of the welding we are doing today, I will be using a shade 9 as that is what is comfortable for me. For additional shade recommendations, I strongly encourage you to check out the ANSI Z49.1 Safety in Welding, Cutting and Allied Processes which is available free for download on the internet.


Now that you are familiar with the safety requirements, let’s get into the actual welding portion of this article. For this demonstration, we are going to perform a fillet weld on a lap joint using some 1/8” thick steel coupons. We are using the ESAB Rebel 205 AC/DC, since were running steel we will set the machine on DC- at 130Amps. We need roughly 1 amp for every thousandths of material thickness and 1/8 material is .125 amps. I like to add 5 additional amps just in case I need a slight bump. I will be using a 1/16” ER70S-6 Filler rod and a 3/32” E3 tungsten with a 30° grind angle. I want to keep my weld right around the 1/8 size so the 1/16” filler will give me just that. Remember the weld will be roughly 1 and 1/2 times the diameter of the filler wire. As with most TIG welding we will be running 100% argon and because I am using a gas lens I will run about 20CFH. If you are using a standard collet body you can set your flow around 15CFH or so.


Before we get into welding with filler wire, we need to understand how to manipulate and read the puddle. The best way to do this is to run a couple autogenous welds (fusion) first. Once we get the hang of welding without filler and fusing the materials together we can then add filler.