So I'm working on my smaw vertical V groove bend test (1/4" mild steel) in shop now. I'm looking for overall tips. So far I bent it up today and almost passed.
The way we have the test setup is you have 2 6" pieces of 1/4" mild steel with a 45* V cut in them. I ground everything down to near perfectly flat, then used a wire wheel to clean off any oxidation. I tack welded the two plates onto 1" thick runon/off tabs about 1/2" from the edge. The space between plates was about 3/32" (with 3/32" lands ground into the V edge). I then took the wire wheel to it again for good luck. I did the root pass with 3/32" 6010 on about 95a dcep (dcrp), I key-holed the weld (was told to) so you could see the weld from the backside. Used a slag hammer and wire brush to clean off the slag and then put on a weaving pass with 3/32" 7018 on the same amperage. Cleaned that slag off and put a cover pass with 1/8" 7018 weaving about 110a. Allowed whole setup to cool about 22 hours- was room temperature when handled next.
Ground down both sides of the plate perfectly flat and sheared it into 4 1 1/2" pieces (yes the weld was in the center of each...). I wire wheeled the edges of each piece to remove and little bits of metal that may have been on there from the press. Upon inspection I couldn't even see there was a weld going through the pieces. Time to bend a perfectly nice hunk of steel...
First up- unwelded side down. Two small cracks on one side (1/16") and one on the other.
Second- same as #1
Third- welded side up. One crack on each side.
Fourth and final- welded side up. Pass- no cracks.
What I think I need to do- use slightly more amperage on the 6010 root, make the 2nd pass wider and taller to fill the groove up more. Finally make the cover pass wider, and flatter. What do you guys and gals think I need to do so my weld does not crack? Remember the rules of the test are 3/32" 6010, 3/32" 7018 and 1/8" 7018, vertical position.
I need a picture because I cant get your description to come together in my head
1/4 inch steel thickness.... Beveled... 3/32 land, Backing strip, and Keyhole? That is a mighty strange combination.
Or am I seeing "run off tabs" and mistaking it for a full length backing bar?
Also also, If your work is to be compliant with D1.1 structural code, you have not described a failure. Two sixteenth inch indications on a standard bend is not reason for a failure. There may be other factors that you diddn't describe that caused the failure... But from what you have provided I don't see a failure.
I'd put a picture up... but I don't have a digital camera and don't know how to transfer pics from my cell. I'll try and draw a ms paint picture after school for you guys. There's no backing strip (because you can't keyhole with a backing strip? LOL). I kind of expected it to fail, noone gets it on the first try.
Hey Fritz
I get it now...
Quarter inch is pretty thin to weave 7018 1/8... If you are allowed to run them, stringers may help you get that crown a bit flatter. It will certainly help reduce undercut.
Also 110 amps is on the low end for 1/8 E7018... Running it that cold may increase the chance for slag inclusions or sticking. Again, it can be done but it's difficult... I like between 120-130 when running 1/8 E7018 Vertical.
Keep that 6010 deep at all times, You want the reinforcement on the back side of the weld. A flat to concave profile on the root pass will leave a bit more space for your fill... V-groove in 1/4 inch and 3 layers is an interesting project... 3/8" is better suited... But also more spendy.
i believe you can put a 1/8 radius on those edges try that to and always adjacent to the weld bead
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