4g gmaw root pass
by Alex Sanchez
(Dallas Texas USA)
how do i keep from being concave on back of root weld ?
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For the most part, it boils down to how you prep the joint. a 1/16" land and a 3/32" gap tends to work pretty well. After that, setting the voltage and wire speed right is the next most important thing.
The voltage should be around 18-19 and wire speed at around 200 ipm using .035" bare wire.
If your machine does not display inches per minute, the best way to get in the ball park is to press the trigger for 6 seconds....thousand one...thousand two...etc.
and let wire run out ...then measure the wire, round up to nearest whole inch...then add a zero.
thats your ipm or inches per minute.
so you need to run out 20 inches in 6 seconds in order to have 200 ipm of wire feed speed.
make sense???
for the root pass only...
Use a slight drag/pull angle....very slight.
You may feel the need to weave a bit so that the root pass does not crown up too much but dont weave much at all and stay on the front of the puddle as much as is possible without shooting whiskers thru.
I did a video on this a few weeks ago that might help...
you can click below to see the page with 4g test tips or just watch it here.
4g mig test
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