Hello all. I'm working on my final set of welding certifications through the Ironworkers union here. The first test is 1" plate, with a 3/8" backing strip in 3G position. I'm using NR-233 .072, with a wire speed of 140, and a voltage setting of 19. My big problem is at the start of the initial root pass, I burn through, though not completely, and lose the puddle. It feels as though the backer is getting too hot and the wire's cutting through. I've had it do this several times, about 3/4 through the pass as well. I have tried adjusting my wire speed lower, upping my voltage to broaden my arc, etc. I hold my gun at a drag as instructed, and hold my distance between 3/4" and 1" away.
When I up my voltage to 20 or 21, I get porosity, and chicken tracks. When I lower my wire speed, I have to move slower, and it really directs more heat on the backer, getting it pretty hot. Any ideas on what I can do?
Once I get pass my root pass, and 2nd pass, my welds look almost picture perfect and the slag falls off half the time, as I'm still welding. Almost like if I were burning 7018 or 7016.
EDIT: I have read some of Blasters posts on NR-232 and it has helped. I just can't figure out what to do to get past this burn through/dig-out problem.
Thanks!
-Andrew
Sounds like you are running stringers. Did I read that you are using a drag angle while trying to run a vertical stringer in the root? You need to be more straight on to a push angle to run a stringer up that root. You do not want to add voltage if you are burning through. Tell us some more about what all you are seeing and trying.
I'm doing the root in one pass. I have a 3/8-1/2" space between the bevels at the backer plate. I have my gun pointed downwards like I was instructed by the welding instructors, at about 15-20 degrees. More or less it feels off the bat like I am starting to cut into the metal a little bit and then I lose my puddle and it runs out. Today I actually managed to push the wire through the backer plate. I've tuned the machine to where the puddle feels a little more fluid, and sounds more like sizzling bacon, or sparklers. I won't be able to get back into the booth until Tuesday, but I could always bring my camera in, and fix it inside my hood, and record a video of me running the root. Maybe that will tell more than what I can describe.
I appreciate the help so far.
They must be using a lesser degree of bevel on the plates to be opening up the root that wide. That is a whole bunch of material to fill in, in one pass. With a root that wide, a weave may be easier(don't know what your WPS says about that, you didn't say). With a weave, you hold the arc against the sides and travel pretty quickly across the middle and pause again, once you see how the puddle reacts you can time it pretty good so that you can travel on up the plate and not have undercut at the edges. Try angling the gun with the wire pointing upwards, gun handle down, so the arc force can help you overcome gravity and hold the puddle up there.
Watch this:
http://www.weldingtipsandtricks.com/vertical-mig-welding-technique.htmlIt's Mig(solid wire) so don't pay any attention to the machine setup because none of it applies to what you're doing...pay attention to the gun angle and his technique. He uses a slight push angle vs what you were doing. I think you will have better control of the puddle if you use this technique.
Im trying to remeber but it was either NR-211 or 233 or 232 but one was an out of postition wire and had a similar issue and it went away when some of the welders were pointing it down a few degees. I never tried it myself.
0.072 wire huh, seems pretty big. I am use to 1/16 FCAW Gas Shielded and you could barely run it vertical as the amperage was soo low that it almost couldn't hold the arc. Once you got it dialed in it ran really nice 3Gs. maybe your going to slow, we really had to move when using that diameter and on a root pass it can be difficult with the 400 amp guns we were using because its a little tight in the root with the size cups we had. That shouldn't be a problem for you with having 3/8-1/2 root opening. D1.1 says 1/4" root not sure about bridge stuff. I saw a few guys burn through but they couldn't run vertical without it falling out since the amperage was so high.
.072 232/233/any T-8 wire, I'm almost always angled down on verticals. A "traditional" style weave will kill you with those wires on xray/UT or a bend, you'll have mucho slag buried.
You can wobble tho, and the wobble can get fairly big assuming it's rapid. If you don't wobble at the starts you can drill a hole straight thru, those wires run at pretty high heat.
If you have a run off tab at the bottom of your vertical you can trigger the gun until there's a suitable shelf of iron to build on.
Don't try to run these wires cold. Learn to work with the appropriate heat ranges.
It's very helpful to have controls at hand and adjust as needed. Knowing what adjustments are are needed for the particular pass are crutial and only comes with experience.
A lot of people try to run those wires like they weld with Lohi or with the junk FC wires/dual shield wires but it's really a different world with different visual cue's. Learning those cue's is pretty important and the key to using them. They aren't exactly hard to run but they are different to run. And less forgiving than most process' so being on top of the fine tuning is really helpful.
Use a standard weave and you'll be guaranteed to produce defective welds every time.
Keep the heat up into the recomended range and learn to control it in different scenarios by tuning and you'll be good. Don't outrun the slag because it's the only thing holding the puddle, gravity always wins.
Hi heat is your friend, the slag shelf is your friend. Without either these wires will eat you alive.
That's just my experience so take it or not.
JT
I appreciate the advice. That's my main area of problem, is drilling through the bottom of the run off tab right before I get to the beveled plates. I lose the puddle and bore a divot into the tab within 3/4" to an inch of starting the weld on the backer. This is definitely different than running stick.
Then try wobbling the wire around a bit, that works for me and I know exactly what you're describing. It's a lot of heat to concentrate on one area of small plate and it will knock a hole in it for me without the movement. And away goes the puddle on your boots.
I knocked a hole in several backing plates before learning to move around, I use circles, jiggles, whatever makes me happy at the time but have to be moving some.
I've seen instructors tell students that you CAN'T wobble with T-8, you HAVE to move straight up but haven't found that to be true in real life. At least for me because I move it around constantly. But no weave.
Your mileage, of course, may be differnt.
JT
I wobble and wiggle right from the get go. I'm starting to think I am letting the backer get too hot, and my angle is too far down. I'm going to give it another good shot this Tuesday and Friday, and maybe get the hang of running the root pass. I definitely appreciate all the help and information, everyone.
How big of a wobble?
I only know what works for us, other people will have better understanding of 232 than me but at 140 and proper V and my version of a wobble the problem of digging a hole in the backing goes away. Wish I could be more helpful, we only run that wire every few years, but it's usually a lot of it at a time.
Is your travel speed too slow?
JT
I wobble between the end of the first 3rd of the backer plate and the beginning of the last 3rd of the backer plate. Maybe I'm not moving fast enough, or need a wider wobble?
Thanks! I went ahead and printed the manual and read through it. I'm going to keep it on me for reference as well.
One thing else to mention.
T8 Self shielded FCAW electrodes in my opinion are also a little more likely to cause problems with arc blow, especially in the vertical.
If arc blow is an issue.. It will get worse and the current increases... I still like to run the T8 wires at the lower end of the range.. (but always in the range)
Also... Make sure when you are looking for the best range (within the WPS) and you are looking at manufacturers data... Look at the BRAND and SPECIFIC filler... There can be some pretty pronounced differences in the "sweet spot" of one brand of self shielded FCAW filler and another brand...
For plate testing I would advise to put the work clamp directly on the bottom of the test plate and weld away from it.
If you are on an old work bench, it may be a good idea to break out the AC SMAW and run a few passes, moving the work clamp to various points on the fixture... This will break up magnetic fields in fixturing to some extent and quickly.
You may be running too far ahead of the puddle, resulting in the digging.
Your wire may not be fresh if you are getting gassing problems when turning the voltage up high enough to prevent burrowing.
You may be getting gassing resulting from slag emtrapment at only 140 IPM on your root.
With your .072 wire I would try going up to 170 IPM if doing a full width root pass on cold 1" plate with a 3/8" root opening (I think that was the fit up you said your were doing. The extra wire speed is particularly useful if you must burn out the 90 degree corner of a bevel groove, but it will help on a V groove too.
You will probably have to "trigger" the gun (periodically let off the trigger so the slag can freeze and follow close enough below the wire) while on your run off tabs. The simply don't have the mass to adequately absorb the same amount of heat that you will want once you get on to the 1" plate.
140 IMP is OK for cover passes, and it will be fine although slow during the fill passes.
General tips for T-8 roots in a groove weld: Use plenty of wire speed to get sufficient current to blast any slag out of the way and to tie in the bottom corners. Use a drag angle to blast any slag out of the way. Adjust the voltage to get a slag follow that is close behind the wire. Adjust your stick out on the fly if needed to maintain a clean puddle - I usually use a little shorter stick out on roots than on fills or covers as it raises the current level without piling additional wire and slag into the puddle. Don't run too far forward on the puddle - it will result in digging into the backing bar. This is one of the reasons you want to have plenty of current. If you don't have plenty of current and you stay back on the puddle a little to prevent digging into the backing, you may trap slag. Finally, it is fine to give the gun some side to side movement, especially with a root opening that is too wide for comfort with a single pass, but too narrow to comfortably put in two root beads. However you want to keep the puddle liquid from edge to edge, without alternating freezing like you may do with 7018. However, if you current level is high enough, allowing alternating freezing at either edge can still work too.
Thanks for the information! I'm definitely going to try it out. It's felt like I've been too hot, every time I run my passes, but from what I've been getting in replies, it seems like when I think I'm running too hot, I'm running too cold. I definitely appreciate everything I've gotten towards information so far from everyone.
The fit up is 1" v groove beveled plate, with a 3/8" thick backing strip, and a 3/8" to 1/2" root opening, for both the 3G and 4G positions. I'm certain once I get the root down, I'll have no problems with this test. It's just the root that's been killing me every time.
Thanks again for all the information and replies!
The root opening is too large if you are testing to AWS D1.1.
Arc blow can be a problem, especially toward the top of the groove when welding vertical uphill especially if the test plate is only tacked to the bench along the bottom edge. There are several means of mitigating arc blow. They include the following:
a) reduce the welding current since the magnetic field strength is directly related to amperage.
b) use heave tack welds to provide ample cross section for the current to pass through since current density is related to the cross section of the conductor (tack welds).
c) attach the test plate with multiple tack welds to increase the cross section of the conductors and use braces attached to the top of the plates as well as the tack welds along the bottom edge to provide multiple paths for the current. I prefer to use two tack welds along the bottom edge placed at the far corners of the test plate. I also attach two braces, one at each corner, along the top of the test plates to mitigate arc blow by providing multiple current paths and increased conductor cross section, thereby reducing current density, thus reducing the effects of arc blow.
There have been several other recommendations listed in the responses. I would visit the manufacturer's website to see what is recommended for welding parameters. Usually mid-range recommended by the manufacturer is a good starting point. Also, pay particular attention to the contact to work distance, sometimes the electrode extension or stick out is listed. The electrode angle is also important. Some FCAW electrodes utilize a slag system that freezes before the fluid weld pool. The slag acts as a form to hold and shape the weld bead as it freezes. Depending on the slag system used, the electrode is angled upward or downward (strange to get used to if you are experienced with SMAW). The manufacturer can usually provide direction in this regards.
I mentioned the root is too wide if testing to AWS D1.1 where the required root opening is specified as 1/4 inch. A slight weave is fine when welding the first and second layers of the V-groove. However, at some point it is advantageous to use a split layer technique. Attempting to carry too large a weld pool on the first or second layers is an invitation to burn through the backing.
Good luck - Al
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