Flux core cracking out

[Tech Support Copy?]

Im welding some 1/2 and 3/8 a36 plate to some 10 x #33 I-beam. The plates have been plasma cut by one of our cnc plasma cutters in various shapes; base and cap plates, knee brace mounts etc... Im using a miller deltaweld 452 with a 70 series wire feeder, running .045 dual sheild. I have the the machine set at 25 volts, with a wire speed of 450. Im using airgass blueshield (85% argon 15% co2). All the welds have been applied in the horizontal position. The problem is that some of the welds have cracked out after they have been welded. There is a hairline crack that runs directly down the center of the weld. I have tried to be detailed in the explanation of the problem. If anyone could give me some advice as to the cause and what I can do different it would be much appriciated. Thanks again

[diamondback]

cored wire

TSC,
A couple of other questions just for clarity.
1. which dual shield wire are you using? there should be some numbers and letters to help out.
2. Are you pushing or pulling the puddle?
3. Can you see the weld cracking as the puddle solidifies or does it crack later when the part has cooled some?
4. Have you call the guys at Miller? 902 954 3813 or Hobart 800 424 1543

[Tech Support Copy?]

TSC,
A couple of other questions just for clarity.
1. which dual shield wire are you using? there should be some numbers and letters to help out.
2. Are you pushing or pulling the puddle?
3. Can you see the weld cracking as the puddle solidifies or does it crack later when the part has cooled some?
4. Have you call the guys at Miller? 902 954 3813 or Hobart 800 424 1543

I dont know the numbers on the side of the roll Im not at work today, but I have been pulling the puddle, with an angle of about 10 - 20 degrees. I have noticed the cracks after the parts have cooled.

[diamondback]

cracking

What you are seeing is cold cracking. It is probably being developed from the joint configuation where there is a high amount of restraint on the parts after they are welded. It could come from a rigid fixture or just be built in once the weld is complete. A couple of things to try: 1. look at the ambient temperature, cracking usually happens when a part cools to fast, you might need a little preheat or wrap the weld area with a fire blanket as soon as you are done welding. 2: try a small root pass before the finish pass, if you are trying a 1/2", 5/8" or larger with one pass then you are trying to fill the center of the weld to much for the heat you are putting in. You should also look at your settings and make sure they are in the correct range. When wire feed welding keep in mind that your energy input is much higher than if you are stick welding and is run different than wire. Make sure you are running stringer beads. If your weld gets real wide compared to it's depth you can get cracking also.

[lars66]

Are you grinding the plasma cut portion that is in the weld back to clean metal before welding?

[tacmig]

Another suggestion...

I think that diamondback has rolled out some good advice here but here's another thought. This happened to me about a year or so ago and I did everything including kicking the shop dog to no avail. One of the perks I have is that we have a metallurgist that is right down the street (offshore inspector) and I can pick his brain. So of course I did, he sampled the weld (hydro & paint) and with the exception of the cracking it was sound. The problem: contaminated steel! I never even heard of this. We always clean our weld points with acetone but the problem was with impurities within the steel not the weld area. we had to return the entire lot and once we did, no more problem....go figure


Just a thought....

TacMig

[Jolly Roger]

If you have gotten contaminated steel only once boy are you lucky. The stuff from India seems to be real bad for that, almost like it has sand in it. I have also gotten some Chinese steel I wasn't very impressed with. I won't even use a Chinese pipe fitting, making it work costs more than the difference in price over domestic.