July 4th, 2018
By Dave Lynnes
The first weld on a pipe is called the root pass. Before starting the weld, first, grind (feather) the tacks on both ends until the material turns blue. Try not to remove the material from the middle of the tack. I call this ramping up and down on both ends of the tacks. If you do not grind the ends of the tacks thin enough, you will not get good tie-ins to your tacks.
Start welding on the center of one tack to preheat the material, and by the time you get to the end of the tack, a proper tie-in to the tack is achieved. Weld to the center of the next tack without stopping between tacks.
If you stop between the tacks, you must grind (feather) 1/2″ back on the end of the weld. Start welding 1/2″ back from the end of the weld to get a good tie-in with the end of your weld.
I use 1/8″ 6010 electrodes for the root pass, and I set the welder around 80 amps.
When starting a weld, a keyhole opens, and I want to keep it a little larger than the diameter of the electrode. Maintain a short arc length while welding to get good penetration on the inside of the pipe. While welding, if the keyhole opens up too much then increase the travel speed. If you still can’t control the size of the keyhole then stop welding and turn the amps down on your machine. The amps can vary from one welding machine to another, continue adjusting until you find the setting that works.