MIG Welding Pipe: Welding the Root Pass



*See bonus footage on How to Fix a Void in Pipe at the bottom of this page*
 

What you will see in this episode:
In this episode of TIG Time we are back at Cowley College in Ark City, KS. Many of you have been asking about MIG welding pipe, so I recruited the head instructor, Bob Moffatt, to show us some of the techniques he teaches to future pipeline welders. To demonstrate these techniques, Bob will be using 8 inch (standard wall thickness) carbon steel pipe.

The Setup:
This episode will concentrate on the root pass; and in this case, the MIG (GMAW) process is going to be used. Before we begin the root pass, the pipe was tacked in three spots around the pipe with a gap of anywhere between 5/32” to 3/16”.

  • Voltage: 18.2V

  • Wire Feed Speed: 225

  • Amperage: Approx. 125

The Welding:
For this demonstration, the pipe was setup on a turning wheel in order to maintain constant travel speed. Bob sets up his torch at about 10 O’clock as the wheel is turning the work piece away from him. In order to get necessary reinforcement and proper sidewall fusion, it is critical to keep the wire on the leading edge of the pool so you can shoot up and underneath it.

Equipment Used:
Machine: Lincoln Power MIG 350
Wire: Short circuiting ER70S6 .035 diameter wire
Gas: 75% Argon 25% CO2

BONUS FOOTAGE: Fixing a Void in Pipe