MIG welding certification testing is rare for structural welding work. They are more commonly used for pipe welding.
The MIG welding test given for pipe welder work is typically a 6 inch 80 gauge pipe welded at 6G [the pipe is positioned at a 45 degree angle].
This is a very common test setup:
- 6-inch carbon steel pipe, timetable 80, 37.5 degree bevel, 0" to 1/16" land. 1/8" gap.
- E70S6 bare wire with 75/25 argon / CO2 shielding gas.
- The root is welded downhill and the remaining channels are welded uphill.
After the root and bare wire MIG were welded, some MIG welding tests were filled using Flux core mig. E70S6 is used for the root and E71-T1 is used for the flux-filled channel.
Typically, if the root channel is downhill, it is an open butt joint without a backing. If a backing is used, an uphill channel is usually required.
For the open butt root channel, the thing that will kill the test is to slide and pass the back ray. Some test inspectors will not be able to pass your test… and all that is needed is a slip, so rock stability is key.
The 6G position of the downslope root channel without the backing requires the welder to continuously reposition his body to maintain the gun angle and maintain the best position in the puddle without shooting the beard. It sounds simple, but under the pressure of knowing the risk of a good pay tube welding job, the shock can take over and destroy your day. That's why practice is important enough so that you don't get nervous on the day of the exam.
- Stickout = distance between the arc and the tip of the contact . Keep short circuit on the bare wire and keep it on the core for a long time
- MIG gun angle. The tube is round. Hey. Correct? Keeping the gun angle correct on a 6-inch pipe means changing the position smoothly and often. Always make sure you don't cross the root line.
- Keep the nozzle clean . Splash-filled nozzles are often short-circuited when you touch the copper nozzles to the pipe. It always happens at the worst of times. Clean the nozzles every time you pass.