Sudden Rash of Transverse Weld Metal Cracks
Sudden Rash of Transverse Weld Metal Cracks
(OP)
Comments would be appreciated on the likely causes for a recent outbreak of transverse weld metal cracking observed on fabrications.
Welding is carried out within a dedicated fabrication shop and is all fillet welds on A36 base material using E71T-1 cored wire and 100% Carbon Dioxide shielding gas.
Over the past week three different welders have produced welds with varying levels of transverse cracks plus a few longitudinal weld metal cente-line cracks.
Cracking is isolated to the weld metal - no base material cracks have been observed - and the cracks become apparent after post weld stress relief at 1100F when inspected by magnetic particle.
Welding is carried out within a dedicated fabrication shop and is all fillet welds on A36 base material using E71T-1 cored wire and 100% Carbon Dioxide shielding gas.
Over the past week three different welders have produced welds with varying levels of transverse cracks plus a few longitudinal weld metal cente-line cracks.
Cracking is isolated to the weld metal - no base material cracks have been observed - and the cracks become apparent after post weld stress relief at 1100F when inspected by magnetic particle.





RE: Sudden Rash of Transverse Weld Metal Cracks
This sounds like hydrogen embrittlement related to the weld wire/flux. How was the wire stored? Is the problem related to a specific spool of cored weld wire??
RE: Sudden Rash of Transverse Weld Metal Cracks
RE: Sudden Rash of Transverse Weld Metal Cracks
How are weld joints cleaned prior to weld?
Picking up a little moisture could give you some H issues.
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Corrosion never sleeps, but it can be managed.
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RE: Sudden Rash of Transverse Weld Metal Cracks
RE: Sudden Rash of Transverse Weld Metal Cracks
Hg
RE: Sudden Rash of Transverse Weld Metal Cracks
RE: Sudden Rash of Transverse Weld Metal Cracks
I'm in the south too, and we'll find fabricators not preheating in the winter because most of the year they don't have to and they just forget the whole concept. Or they don't realize that they have to heat more once the temperature drops.
Hg
RE: Sudden Rash of Transverse Weld Metal Cracks
Check the purity of the shielding gas. Is the welder purging the system priotr to welding?
RE: Sudden Rash of Transverse Weld Metal Cracks
Hg
RE: Sudden Rash of Transverse Weld Metal Cracks
Possible solution to your problem - order replacement flux core wire as SFA 5.20 E71T-1H8. The H8 is a hydrogen designator that specifies the maximum hydrogen level in the flux core wire.
Keep in mind that 99% of the time transverse cracks are related to dissolved hydrogen in the weld deposit. Purchasing new wire is the quickest way to verify your problem. Preheat will only help to reduce thermal stresses and reduce the level of restraint. The problem is that dissolved hydrogen reduces the ductility of the weld metal during solidification. Any subsurface cracks open up during PWHT.
RE: Sudden Rash of Transverse Weld Metal Cracks
You may also wish to check the deposited weld metal chemistry for a high Carbon Equivalent. It has not been that uncommon to find "out of spec" filler metals.
RE: Sudden Rash of Transverse Weld Metal Cracks
Is there a reason why you are using the E71T-1 in lieu of E70T-1? The quick freeze slag might be causing problems. With the E71-T-1 product the torch angle is much more important than with the E70-T-1 product.
RE: Sudden Rash of Transverse Weld Metal Cracks
No particular reason for the choice of wire - we have been using it very sucessfully since 1996 this is the first time I have observed any major problem with this consumable.
RE: Sudden Rash of Transverse Weld Metal Cracks
How did you get the pictures into your post?
StoneCold
RE: Sudden Rash of Transverse Weld Metal Cracks
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RE: Sudden Rash of Transverse Weld Metal Cracks
Hydrogen is usually the biggie. The best way to avoid hydrogen cracking is to avoid hydrogen, but if it is already there, the tendency to crack from hydrogen can also be addressed with preheat. This helps in several ways. It reduces the moisture available from the base metal, if there was any there to begin with, it slows the cooling rate, which produces a more favorable microstructure to resist cracking, and it gives any hydrogen present more time to diffuse out of the weld. It can also be addressed by post-heat. That is keeping the weld hot (usually 500-600F for 4-12 hours) after welding, or until PWHT.
Another factor that contributes to the tendency to crack is base metal and weld hardenability, which is related to their chemistry and thickness. The thicker the base metal & weld, the higher the cooling rate for a given base metal temperature (up to about 1 1/2"). The way to compensate for thicker base metal, is- you got it- more preaheat. As mentioned earlier, filler metal chemistry can also contribute if the carbon equivalent gets too high. A higher preheat help with hardenable filler metals too.
High joint restraint is yet another way to cause weld metal cracking. Thick plates or welds create tri-axial stresses in the weld, which if the weld is not tough enough, will cause cracking. This can be helped with preheat also, in order to reduce the residual stresses.
In a small number of cases, PWHT can also cause embrittlement of the weld metal enough to crack. This is the last of the reasons for cracking I would look at, but it is a possibility. Some manufacturers of E71T-1 add elements such as Boron that help with as-welded toughness, but can seriously degrade toughness after PWHT, depending on time, temperature, and amount of the additions.
Also, Per AWS A5.20, the limit to Ni in E71T-1 is .50% max. I do not think many manufacturers intentionally add Ni, as they can obtain the required toughness without the added expense.
RE: Sudden Rash of Transverse Weld Metal Cracks
RE: Sudden Rash of Transverse Weld Metal Cracks
This is the same reason why the first two or three feet of the flux core wire should be removed before use at the beginning of the day.