I am currently in college for a welding techniques program and by the end of april the course will be over. I have been using class time to make my own CWB tests using a simple jig provided by the college and filling it in with the mig. I have done 5 of these tests and they all failed due to the same defect. Once i machined the backing plate off and grinded it out flat I would always notice a hairline crack on the 90-degree side of the groove. It is clear that I am getting lack of fusion on my first pass down in the lower corner where the 90 plate meets the backing plate. I tried a couple machines, I tried running hot and every test i made has been grinded so i am not welding on any surface scale or other impuraties. On the last attempt I even tried welding it backhand. As far as the rest of the welds go its nearly perfect but once that backing plate is off there is a very thin line where the filler metal did not fuse in that bottom corner. I want to be able to pass this test with the mig everytime so I can go out and get a job, can anyone give me some pointers? thanks
Results 1 to 4 of 4
04-08-2009, 11:39 AM #1Junior Member
- Join Date
- Apr 2009
Having Trouble with Flat-Position Mig CWB
04-08-2009, 12:46 PM #2
Sounds like you need either more root gap, or to hang out on the sides and move accross the center quicker to tie in the toes and fill the root better.
I weld in a NNN pattern at the bottom of the first N hang out and count 1,2 then quick whip accross the center and count 1,2 then quick across the center again repeated constantly till the end then put a pig tail whip in the end to fill the end crater and let off the trigger.
Practice it the only thing that counts here to get it right.
Best of luck,
04-08-2009, 04:12 PM #3Junior Member
- Join Date
- Apr 2009
I did it! Passed the root and face bend with not a single defect! I set the machine to 22.5 V and wire speed to 400 for the first pass and finished the rest of at 22.0/400, i up'd the wirespeed a bit more than before (380) and my voltage from 20.5 and now everytime i lay down my first pass i get full penetration! thanks!
Now that I am able to pass CWB in Vertical/Horizontal/Overhead/Flat (MIG) I'm practising highpressure plate, Im getting pretty good a keyholing just need to work on the undercut I am getting on the back of the plates
04-08-2009, 04:40 PM #4