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Jason Becker

By: Jason Becker on September 16th, 2019

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TIG Welding Lap Joints

GTAW | TIG

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.Screen Shot 2019-09-16 at 12.56.59 PM

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.

One exercise I have my students do is take a 1/8” piece of filler metal and bend a small hook or loop at each end and practice moving the rod back and forth in their hands while they are watching a movie or lounging around the house. This helps to develop the necessary muscle memory in their hands so when it comes time to weld, it’s a natural movement to them.

Okay, so we have the appropriate PPE on, the machine is set the torch is setup and we practiced feeding our filler and we are ready to weld. Start off with a couple 1’8” plates in the lap joint configuration. I like to put two tacks on each side to prevent the material from opening up on the opposite side of the coupon. This sets up both sides so you can practice two lap welds per set. Once we are tacked up, hit the joint with a wire brush to remove any contaminates on the surface of the materials. With all of that done, let's discuss our angles, with TIG welding we need to focus on three primary angles. They are work angle, travel angle and filler metal angle. Our work angle should be roughly 45° so that both pieces of material are getting half of the arc. Our travel angle will be a 5°-10° push angle, and the filler angle should be 90° perpendicular to the electrode in the torch at all times.

With everything in place, set the torch up close to the material and slowly press the foot pedal in with the tungsten about 1/16” away from the surface of the material. We need to wait at this point to establish the puddle, you should see the both pieces of material heat up and turn into a liquid, once they join (just like in the autogenous weld) we start adding the filler metal to the liquid pool and slowly move down the joint pushing the puddle along the way and adding the filler metal as we go. The weld should not pass over the top edge of the top plate, we want to keep the weld at 1/8” the exact height as the thickness of the plate.

Once we get all the way to the end, it is important to make sure we fill in the crater to the entire cross section and slowly taper off the foot pedal until the arc extinguishes. Now, hold the torch still until the post flow stops. You should now have a pretty decent looking weld. Depending on the outcome of the weld, try at least 2 more before making any changes to your technique. You should analyze everything about the weld and your technique. Determine what went right, and what went wrong and adjust from there. Practice is going to be a crucial part of this whole operation. It will take a lot of time under the hood to get it right, but once you do, the rest of the weld joints will be easy. Make sure to join our Facebook group and post your progress with pictures and settings. You will be able to get good feedback pretty quick, and until next time Make Every Weld Better Than Your Last. 

About Jason Becker

Jason Becker is a welder/fabricator with 22 years of field experience in the welding industry and a Marine Corps Veteran. He is also an AWS Certified Welding Inspector and Certified Welding Educator (CWI/CWE). While teaching welding at his local college, Jason pursued his Bachelors Degree in Construction Management from Seminole State College and graduated with honors in 2016. He now works full-time as the co-host for Weld.com.