by Bob Moffatt
If you have been in the welding field for any amount of time, you have heard of the term 6G. Many people shiver at the sound of the word, it can be a very intimidating welding position.
After all, it is supposed to be the most difficult position setup aside from a 6GR. But it doesn't have to be. In this episode, Bob walks us through step-by-step on how to put in a good root weld with the Gas Tungsten Arc Welding (GTAW) process.
The first step is to make sure the material is prepped correctly. Preparation is key, and the biggest part of the preparation to a successful weld is to clean the base metal both inside and out. We want to clean all of the mill scale off of our coupons or pieces about 1/2"-3/4" back from where the weld will occur. The cleaner the metal, the better off we will be and the easier the material will accept the weld.
After we have every thing cleaned and ready to go, we want to set our gap and check the hi-lo. For this example we are using 4" SCH40 and setting our gap at 1/8" and making sure that we have little to no hi-lo, meaning the internal alignment of the pipe is flush with each other. Once we like the fit-up, we put in 3 tacks, just like in the 5G video, we are going to place them at 10 o'clock, 12 o'clock, and the last one at 2 o'clock. Again, this will allow you to rest the filler metal against the the outside tack so your filler is more stable.
Now, we light up in the 6 o'clock position and start to add our filler, the advantage to having the tack welds located where we put them is now we can see through the gap and backfeed our filler. From the initial start at 6 o'clock to 8 o'clock we will freehand the root and just move the tungsten from side to side. Once we're at 8 o'clock we can start walking the cup as we will have a bit more range of motion. We will then go all the way up to our first tack and and roll right over it very slowly ensuring we melt it in good and achieve penetration into the tack as we move toward the 12 o'clock position. That completes 50% of the pipe.
The next step is to feather out or initial start at 6 o'clock and perform a restart and follow the same steps as the previous half of the pipe. Depending on which half of the pipe you did, you may have to switch to your non-dominant hand to put in this weld. I highly recommend learning how to weld with both hands for exactly this reason. Once you are at the top of the pipe just melt into your 12 o'clock tack and ensure good penetration.
Thats it, now just setup for your fill passes and lace them in there starting where ever you like. I prefer to keep all of my stops and starts in different areas because it will keep the final weld profile more uniform and if the pipe will be cut for a bend test, your starts and stops will be staggered.