Well we have been seeing some weld cracking imediately after welding. This is the what I have
A913-Gr. 65 column
A572-Gr. 50 2"T doubler plate with two 2"T CJP continuity plates on both sides of the doubler plate.
Preheating to 225
Welding with FCAW 71 ultracore
Cracking at the root pass, but not every weld just random welds.
30 degree weld prep
No gaps between web and doubler plate.
We have tried multiple welding parameters.
We are now arcing out the welds then trying to re-weld but still same problem.
What size wire and gas are you using? and what parameters and stickout.
Keep the voltage as low as possible to avoid cooking out the manganese and use a large enough wire and current to get a good size rootpass so that it does not crack due too resididual stress. Inrcrease the Preheat.
The max CE for the A913 gr 65 material is 0.43%
Try using 1/16" 71 ultracore, 75%/25% Ar/CO2, 330 Amps, 28V about 3/4" stickout. 400F preheat
Richard,
This is a bit off-topic - do you have any references for the manganese cooking out that you mention? I'm curious because the "new" welding fume issue seems to be turning towards manganese , now that chromium 6 has been talked about.
We don't currently have a cracking problem but we do have a tendency to weld with voltages too high. We recently switched to C25 gas from 100% CO2 and welders still tend to set voltage too high. I'm just wondering if that is a contributor to higher manganese levels in our fume samples?
Sorry folks for diverting the topic. If need be, I'll start a new one.
supermoto,
You don't state if your working to a specific code, are you? Typically A913 is recommended to be welded with H8 max diffusible hydrogen. Also, a higher preheat might be a consideration
Are the columns fairly large. Cracking root passes on continuity plates isn't anything new. Are you letting it cool down before completing the weld? If you heat the web to a higher temperature than the continuity plate, you will end up with compressive stresses in the weld, which will help. Also, is that a 30 degree single bevel? That will create a bead shape prone to cracking. Open the groove angle up to at least 45 degrees, and that will help some. AWS D1.1 actually allows welding the A913 without preheat, but no the A572, so you have to go to at least 150F according to D1.1 table 3.2. Try heating the continuity plate to 150F, and the web to 200F and see what happens. Another thing that could help would be to switch to a filler that is higher toughness/lower strength. Try one of the E71T-12MJ electrodes, and that can help sometimes.
I am working to D1.1 with a H8 1/16 wire.
These are not continuity plates they are doubler plate. There are continuity plates next to the doubler plate. So I cannot heat the web more thant the continuity plate but I could heat the doubler plate.
I do know that the 913 doesn't require preheat. That is a whole other confusing issue when looking up preheat and matching filler metals when welding A913-65 to A572-50 material. It is quite contradicting. We are trying it again this morning. We have had cracking issues before and it sometimes just goes away.
supermoto
I saw what may be similar problems on the Freedom Tower of the new World Trade Center. (A913 Gr-65 Arcellor W14X730s with 3", 5 1/2", or 6", by 42 inch wide, A572 Gr. 65 "Mod" (Not an ASTM Spec.) Arcellor doubler plates on each side, attached to the 5" thick flange legs.) If your doubler plates are along the web, this does not apply!
-Preheat the entire length of the column assembly simultaneously, using pipe heaters.
-Uniform preheat that is maintained and not cycled through the allowable ranges was part of the solution.
-Squeeze and tack weld at or above minimum interpass temperature.
-Do not let the part cool down between tack welding and running the fitst three passes.
-Make sure that the carbon deposits from starting the heating torches do not get in the root pass. Light the pipe heaters outside the tube and slide them in after flame adjustment.
-Deposit enough weld metal in the root passes.
-Increase the bevel angle to 45 degrees.
-Watch your depth to width ratio in the root and second passes.
-Use the largest diameter electrode you can handle.
-Start from the center of the column and weld out toward each end.
Joe Kane
Joe Kane
That is great info, but these doubler plates are along the web.
The strange thing is that on one only the transverse welds are cracking. On another only one transverse and one longitudinal weld are cracking.
We may have to increase the bevel.
How is the Freedom tower coming along?
Well not sure what happened but the cracking stopped on the one piece that we were working on.
We did increase the beveled weld prep which I think it helped because the arc length was a little long due to the tight conditions.
Maybe there are welding stress, You need to reduce & redistribute the residual stress
the process
weldment----stress relief (welding stress)----rough machining----stress relief(machining stress)
our is vibration stress relief
My Email: sunnn@semboo.com
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