Maximum size fillet weld that can be done in single pass

[ajk1]

What is the maximum size fillet weld that can be done on site in a single pass?
5 mm? 6 mm? 8 mm?

 

[structSU10]

some info...

https://app.aws.org/forum/topic_show.pl?tid=33799

 

[PSEPK]

According to Structural Steel Design 5e by McCormac & Csernak 2012, about 8 mm for SMAW and 13 mm for SAW process.

A good structural engineer is often a blessing for others.

 

[mike20793]

The AISC Manual shows the number of passes. See Table 8-12.

 

[kingnero]

With what size wire or rod?

 

[ajk1]

I am in Canada and don't have a recent AISC Handbook, but you have provided me with sufficient information for me to have a level of comfort that the weld size I want to specify can most certainly be done in one pass. Thanks very much.

 

[msquared48]

I was told years ago by a mentor 3/16", but I have heard larger recently.

Mike McCann, PE, SE (WA)

 

[MrHershey]

Was not aware of that AISC table. Looks like they added it for the 14th edition.

In any event, AISC lists 5/16" (8 mm) for fillet and single-bevel groove welds.

 

[gtaw]

It depends on the welding process, the electrode, and the position.

AWS D1.1 Structural Welding Code/Steel provides some excellent guidance if you look at the table 3.7 for prequalified welds.

Best regards - Al

 

[ajk1]

Decades ago I too was told 3/16" was the maximum size for single pass weld, but it seems based on what gatw and others here say it is a little more complicated than that. Since I do not have copies of the referenced documents to which you refer, let me rephrase my question, as follows: For steel plate to steel plate fillet welding on site, some of it involving overhead welding, is there a significant cost difference between 5 mm and 6 mm (3/16 and 1/4 fillet weld of 50,000 psi yield strength steel. I would say that if the 6 mm weld requires an additional pass, then there is a significant cost and time difference.

 

[gtaw]

You have not specified the welding process or the electrode diameter.

Best regards - Al

 

[ajk1]

As building structural engineers, we never ever specify the welding process or electrode diameter. We leave that to the contractor's welding engineer. Let me rephrase my question: Are we significantly increasing the time and cost of the project by specifying a 6 mm rather than an 5 mm weld, assuming that the weld length is the same? In other words, 5 mm would work by calculations, but we were considering a 6 mm weld, would we be increasing the welding time and cost by more than 25%?

 

[Agent666]

No, you pay for a little bit more weld metal and potentially some additional time to put the weld down. Apart from that most of the process is essentially the same. I've seen contractors who price a difference and others who don't for a single pass weld.

More often I find you specify 5mm with a view to some economy, and you end up with an 8mm+ fillet round these parts. Welders like to weld I guess.....

Additional passes are where the cost increases, or full penetration welds, because of the prep required to the plates and preparation between individual passes.

 

[ajk1]

To Agent666 - Perfect. That is clear and concise. Thanks very much. Much appreciated.

 

[thaidavid40]

Up sizing from a 5mm to a 6mm fillet leg width should make minimal difference in the weld time - regardless of the position, and the only realized cost increase should be the additional filler metal involved. This would be an increase of weld area of about 44%, and the weld filler metal cost would increase proportionately, though not the total cost of making the weld, which will depend on the welding labor costs in your area.
Dave

Thaidavid

 

[ajk1]

To thaidavid40 (Structural)- yes I see it is a lot more weld material to deposit, I had not thought about it in those terms. I am curious as to why the time to deposit the weld would not increase in about the same ratio?

 

[thaidavid40]

They are both a single-pass welds - ergo, the welder moves continuously one time through. The time to deposit the larger amount of filler metal is, electrically speaking, about the same time as needed to deposit the smaller amount. The actual time spent laying down the larger bead is not appreciably longer than the next smaller size bead.

Thaidavid

 

[ajk1]

thaidavid40 (Structural)- ok, that is clear. Thanks very much.

 

[gtaw]

No one seems to consider the welding process in this discussion. Traditionally, SMAW was used to fabricate structural steel. Large diameter electrodes were able to deposit large single pass fillets with little difficulty. That is no longer the case where fabricators are using small diameter electrode with either GMAW or FCAW. The small diameter electrode makes it difficult to deposit large single pass fillets because the welder must manipulate the electrode to achieve the desired weld size. The manipulation, i.e., weaving, can result in the proper weld size, but it is very likely to suffer incomplete fusion at the joint root.

As a normal practice, I require the welder to pass a T-fillet break test described by AWS D1 structural welding codes. It is surprising how high the failure rate is. I believe the codes fail to take this into account. Many of the code provisions relating to performance qualification were developed when SMAW was the predominant welding process. Using a large diameter electrode, i.e., 3/16 inch, it was easy enough to make a single pass 1/4 or 5/16 inch fillet weld. That is no longer the case. The codes are in agreement that a welder that qualifies on a grooved joint (plate or pipe) is automatically qualified for filet welds. Therein lies the disconnect. My experience has been that a welder that can pass the single pass fillet break test can easily pass the grooved joint test, but a welder that can pass the grooved test will more than likely fail the fillet break test. The disconnect is that the codes (AWS, ASME, etc.) fail to recognize the degree of difficulty the large single pass fillet present when welding with GMAW or FCAW.

Best regards - Al