We are doing the same thing, with Lincoln 5/64" electrode and L61 flux, but we have never had a cracking problem. Sometimes we have a porosity problem from either too dirty metal or moisture contaminated flux, but no cracks.
If you find out the cause please post the cure so I'll know what to do if we develop a cracking problem.
Could your plate and/or flat bars possibly be A514?
Do you have Heat Number/MTR traceability?
Good Luck!
Tim
The first thing I would check is the depth to width ratio of the weld. If it is too deep as compared to the width, it can lead to centerline cracking. Also, an concave bead is more likely to crack than a convex bead, so compare the weld profile on welds that crack vs. ones that don't.
By -
Date 09-12-2003 05:53
This immediately comes to my mind, as well. I've seen it before.
Mankenberg
I would have to agree with GRoberts. Start getting into problems when you exceed 1.5 to 1 ratio. General rule of thumb.
kam
Is there any chance that your flux got moisture into it? Possibly you should try a different lot# of flux to verify you don't have a "bad" batch. I'd even try a different lot# of wire to see if it helps.
Going along with GRobert's post on concave beads, I was wondering if your beads are too thin due to concave profiles. With 1/4" thicknesses I don't imagine your beads are too deep compared to the width but a check won't hurt.
It seems unlikely that preheat would help much owing to your thicknesses.
If you can't resolve this can you switch to a process like FCAW or GMAW? A slightly lower deposition rate would still be faster than making 30' repairs.
Chet Guilford
I have tried a new batch of flux no better. I have checked the weld size and profile all looks good. We are tring a new vendor for the 1/4 x 6 flanges tonight. I will post the results tomorrow.
After running 1 full shift with the new vendors 1/4 x 6 we have had No cracks.We will see what the rest of the week brings. I will post any changes.
We changed vendors for the 1/4 x 6 and went to Lincoln wire and the problem seems to have gone away. We are saving $30-$40 per shift in consumables (tips and liners) just on this one SAW that we are now useing lincoln wire on.
What perameters are you running? (Amps/volts/travel speed/etc) The only other thought I've had so far, is when you run really fast, the grains grow almost straight into the center of the weld pool, which can segregate the impurities to the last spot to solidify and consequently the highest stess point too. Is there any difference on impurities between your heats of flange/web material or welding wire?
Settings for 3/16 fillet weld is
171-209imp wire feed speed,
25.6-29.4 volts,
45-61 imp travel speed
That is farily fast. Have you been able to look at CMTRs for the different heats of plate/wire to determine if some have higher impurity levels than others?
If the chemical composition of the workpiece promotes cracking, negative polarity should be used to reduce penetration and minimize admixture with plate metal.
Try these parameters. I found them in “the procedure handbook of arc welding” published by Lincoln Company for 3/16in. weld size.
Electrode size: 5/64in
Current (-): 340 Amp.
Volt: 33V
Arc speed: 31 -34 in/min
As mentioned before, check your weld prep.
If it is too tight, you will get cracking.
Also, be sure you are not running too hot for the particular wire/flux combination.
Good Luck
brad
I have played with the voltage setting and wire feed speed. This is looking alot better. No cracks so far. Thanks for all your help.
