Transverse cracks in weld

By ravi theCobra (**)

Date 04-30-2009 22:32

Preheat is low - I would use 200 -225 ' F How many days from welding to X Ray ?

By ctacker (****)

Date 05-01-2009 01:22

a little over 3 days from welding to Xray, D1.1 suggests 50F for 3/4" and under, that seemed low, and before we go into producing parts, I wanted to keep the preheat low to speed up time somewhat. so I went with 100F.

By jarcher (**)

Date 04-30-2009 23:47

We had this problem welding with 110 wire in A514. The cause is longitudinal shrinkage of the weld metal is occurring too rapidly. We had good resolution by 1) decreasing the amount of metal carried in single beads (about a 1/4" - 5/16" wide) and 2) making sure the interpass temperature was between 250 and 350 for the whole length of the weld during the entire welding operation. A possible further help would be a prolonged bakeout at 600 to 700 immediantly upon completing the weld. I would guess a couple of hours should be sufficient on 1/2" plate.

By Kix

Date 05-01-2009 13:14

What is the tensile strength for A514-T1 GR B, does anyone know? I would think more preheat would help things to cool more slowly and might solve the prob.

By ctacker (****)

Date 05-01-2009 14:24

110 to 130 Ksi, the last PQR I tested ran at 121 & 123 Ksi.
I'm going to try a higher preheat (200F) and throw some K-wool over the part to slow down cooling, I'll post results next week!

By Kix

Date 05-01-2009 15:10

We use an E90C-D2 wire on all our A514-T1 GR B. I just checked my procedures and they all came out around the low limit, but still passed. One pulled at 111ksi and the other was 112ksi. We have never had any cracking issues and we use no preheat on anything under 3/4" thick. What we build is probably in another ball park from what you're doing though. Is there any way you could switch the wire or do your circumstances require the 120?

By ctacker (****)

Date 05-01-2009 15:28

we have a stock of 120S wire, I was told to use what we have, so I'm limited to it. we have several procedures in place,but they all call for PWHT. and I am in the process of coming up with another, trying to eliminate the PWHT. I'll have to remember the E90C wire, Ive used ER80 with good success before also, coming in at over 100Ksi.
due to the economy, I'm stuck with using our wire.
Regards, Carl

By Kix

Date 05-01-2009 15:45

Yeah, it's a metalcore wire and it's only draw backs are that it can only be used in the flat and horizontal positions. We rotate our stuff on a fixture, so this wire is beneficial to us.

By jarcher (**)

Date 05-01-2009 14:32

The UTS on most of the "B" we've received is between 115-121K, ASTM specifies 110-130K up to 2.5" thick with a min yield of 100K. The preheat ctacker was using is correct according to the plate's manufacturer, but certainly could be somewhat higher. As I posted, its important to keep interpass up and minimize bead size. Some welder weaving a 5/8" wide and 5/16" deep pass is just begging for this kind of defect. My informal observation is that travel speed is somewhat more important than preheat and interpass temp in regard to minimizing this defect, but still the effect of interpass temperature is not trival.

By ctacker (****)

Date 05-01-2009 15:32

I don't think bead size was an issue, 5 passes in a 1/2 plate 60deg bevel with 0 root opening 1/16 root face. I will speed up a little and see if that helps also.
thanks, Carl

By MBSims

Date 05-02-2009 01:34

Transverse weld cracking usually means either high weld metal hardness or hydrogen. Both can be reduced with preheat. High weld metal hardness is associated with cooling rates too fast, and preheat slows cooling rates. When we were welding HY80 and HY100 with E110-18, a 250 F minimum preheat temperature was required and weld puddle size was limited to 2.5 times the core wire diameter. The puddle size limitation doesn't work well for GMAW, so I would try to limit puddle diameter to say 1/4"-5/16" with no weaving permitted. Somewhere at work I have a copy of the ISG Plate welding recommendations for A514 and will try to post them here later.

By GRoberts (***)

Date 05-02-2009 20:42

I agree with MBSims. Transverse weld metal cracking is usually hydrogen cracking of the weld metal. Because weld metal has a lower lower carbon equivalent than base metal, it usually only occurs in high strength weld metal. I have only seen it on 120ksi electrodes and higher, but it can happen on lower as well. As MBSims mentioned, the strength (hardness) of the weld metal and the cooling rate both affect the cracking. While the 100F preheat might have been high enough to meet the recommendations for the base metal, the weld metal in this case requires a higher preheat. Make sure there are no contaminants contributing any hydrogen as well, such as rust, poor shielding gas, cutting fluids, etc.