Long cold tack on thick steel plate

[ATSE]

Code is AWS D1.1-20
Material: A572
Thickness: 0.5" stiffener plate to 1.5" thick flange (1.5" flange is high load tension component)
Application: statically loaded built up plate girder (similar to bridge, but not D1.5)
Shop temperature range: 40 degrees to 60 degrees
Dual shield w/ C25
Fabricator welded a "temporary handling tack weld" via 3/16" leg x 8" long fillet between the .5" stiffener plate and the 1.5" flange joint.
The fabricator says that this supersized tack weld will be incorporated into the final production weld, so no problem, and it satisfies D1.1-20, 7.17
This gives me a bit of heartburn. D1.1-20 7.17 is somewhat vague on this specific item. Does not Table 7.7 apply? I thought this minimum fillet size table was all about minimum heat input, not strength.
An 8" long weld seems to fall outside the understood definition of a tack.
My inclination is to say that a tack weld is still a weld, and low heat input weld on this plate can initiate cracking.
Question: If the AWS codes are the only defining basis for an answer (engineering judgment and common sense do not matter here), is this weld legit, or must it be ground out before welding? The final weld is a fillet weld.

 

[kingnero]

I don't know A572 nor AWS D1.1, but:
What is the carbon content/equivalent for both plates?

If low enough, it might be acceptable. Either way, your concern is valid and should be rightfully addressed.

 

[dik]

What sort of pre-heat?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[ATSE]

Shop temperature range: 40 degrees to 60 degrees (technically below the 50 deg min in the mornings)
Customarily, no pre-heat is used with tack welding for structural steel, and none used for this project. Preheat used for production welds as required.

 

[TugboatEng]

Do you not grind the tack weld out during production welding? Any cracking will be in the tack, not the plate.

 

[FacEngrPE]

ASTM A572 Standard Specification for High-Strength Low-Alloy Columbium-Vanadium Steels Of Structural Quality. In other words HSLA steel.
Carbon content varies per grade. The grades do not all have the same WPS details.

Was the welder of the tack welder qualified per the approved WPS, and was the WPS followed?

 

[MintJulep]

What does "incorporated into" mean in the fabricator's mind? Buttered over? Fully melted into the weld pool? Something else?

1.17.5 Additional Requirements for Tack Welds Incorporated into SAW Welds. The following shall apply in
addition to 1.17.4 requirements.
(1) Preheat is not required for single pass tack welds remelted by continuous SAW welds. This is an exception to the
qualification requirements of 1. 17 .1.

What if it were two 4-inch long welds?

What if it were four 2-inch long intermittent tack welds?

What if it were 8 1-inch long intermittent tack welds?

What length is ok in your mind?

At what length does something magically different happen?

 

[ATSE]

Thanks for the replies.
However, this feels a little like my college Philosophy class. Plus whack-a-mole.
I have no idea what is in the mind of the fabricator. And my general feelings (negative) and past experience don't matter either; what matters right now is code and contract language. And my book spec does not address tack welds outside of D1.1.

Assume all other variables are okay (welder certs, WPS, lighting, weather...). This is not SAW, but dual shield with high toughness wire.
I usually don't get the mill certs until after fab starts, and they always meet ASTM, including carbon content.

Here's my question: Is a 3/16" x 8" long fillet tack weld acceptable per AWS D1.1, if the final production pass is 5/16" over top the tack (without removal first)? Or must the tack be removed prior to final production pass?
My question is an AWS code interpretation question. Or other authoritative source.

Second question: does anyone use specification language (book spec) and/or drawing notes that exceed AWS D1.1 tack welding language. I've never seen this kind of hybrid tack before - gives me heartburn but I need something other than "This gives me heartburn."
Thanks again.

 

[MintJulep]

Well, the only thing I see that supports your remove it position is:

7.17.1(1) Tack welds and construction aid welds shall be made with a qualified or prequalified WPS and by qualified personnel.

If the weld in question was meets 7.17.1(1) then the rest of 7.17 seems to allow its incorporation into the final weld.

Table 7.7 refers back to paragraph 7.13. Both seem to address the final size of the fillet. Paragraph 7.25.1.2 allows adding more metal to undersize welds.

 

[EdStainless]

Fully incorporated in the key here.
If the final weld does not fully remelt the tack then it isn't acceptable.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[DekDee]

Not sure how 8" long can be classified a tack weld (my opinion only).
Regardless, if it is 1", 3" or 8" - it must comply with the WPS regarding preheat.
Nothing wrong with an incomplete weld (or 8" long tack weld) with the following caveats.
Why is the weld incomplete ?
The fabricator must obtain permission from the Client/Owner to transport items with incomplete welds via a Technical Query or Deviation.
That gives the Owner / Client the option of demanding NDT on the incomplete weld prior to completion to ensure possible undue stress was not placed on the incomplete weld which may have initiated cracks.

 

[david339933]

Being in Canada, I deal with CSA W59, not AWS. But normally if the hydrogen designation of the filler metal is H8 or less the material thickness for fillet welds is the thinner part joined...being 1/2". Which gives a minimum of 3/16". Single pass requirements also are not applicable.

 

[ATSE]

Thanks all for the responses.
DekDee said "...Regardless, if it is 1", 3" or 8" - it must comply with the WPS regarding preheat."
I think this is a common disconnect, and vague in D1.1. For structural steel, shop preheat (for shop conditions above 50 deg) before tack welding is not the standard, and very uncommon, particularly for section thickness 1.5" and less. I my mind, this becomes a metallurgical problem with thicker sections.
Tack welding is primarily for fit up.
Is there anyone here with significant HSLA welding experience that is convinced preheat before tacking is a code requirement (1.5" thick to 0.5" thick A572 at 60 deg)? What about thicker sections?
That's a big deal for cost and schedule. If it's absolutely required, I've been lenient for many years (rarely do I deal with steel thicker than 3", though).
My intuition and wishful extraction of D1.1 tells me Ed's response might be the best I can do, in the absence of additional contract language above and beyond D1.1. Which is what I will clarify moving forward on future projects.

 

[gtaw]

The exception to preheating requirements only applies to tack welds that are remelted and incorporated into the production weld using SAW. It is noted that the production weld does not utilize SAW, thus the exception does not apply. Preheating applies to all welds, i.e., tack welds, root bead, intermediate beads, cover beads, single pass welds, multipass welds, need I continue? All welds are required to comply with the preheat requirements included by D1.1 if that is the governing document.

Best regards - Al

 

[r6155]

Preheat and interpass temperature are requirement.

Regards