Max Size of Fillet Weld? 4

[Logan82]

Hi!

Is there a requirement in a standard specifying that the max size of a filled weld = the thickness of the smallest plate?

For instance, in this case, would the max size of the fillet weld be 12 mm?

Also, could it be possible to have 2 fillet welds of 12 mm on a plate of 12 mm?

 

[Enable]

There is no "max size" for a fillet in the condition shown except as a matter of practicality (assuming those plates are >> t). Limits apply when joints occur at plate edges / shoulders, which people sometimes erroneously think limits the fillet size elsewhere.

So to answer your question yes, it's possible. Though at some point your base metal becomes the weak link. Also, warping is a real thing!

See this thread:

https://www.eng-tips.com/viewthread.cfm?qid=428434

EDIT - Actually you will have a minimum fillet size due to the thicker plate! For example, if you connected a 12mm plate to a 25mm plate in a T-joint the MINIMUM fillet is 8mm whereas if you connected a 12mm plate to a 19mm plate the MINIMUM size would be 6mm (per CSA W59)

 

[Logan82]

Thank you for your reply. I understand what you mean by "Limits apply when joints occur at plate edges", but what do you mean by plate shoulders?

Also, is there a minimum plate thickness on which we can weld, considering that the weld root has a certain depth?

 

[Enable]

Sorry for the confusion they refer to the same thing. Sometimes people call them both depending on circumstance so I just put a slash. Same condition!

As far as I understand it we have minimum fillet weld sizes because a large plate will act as a heat sink and draw heat out of the weld, which can initiate cracking. So the size is not demand based but rather based on amount of heat produced by the welding process (of which you need a minimum). However, to get at more exact reasons we will have to wait for the metallurgists to comment!

EDIT - Misread your question. Not that I am aware of other then for practical reasons of burn-through. You'd have to be talking about a real small plate for this to be a concern.

 

[Logan82]

I have checked CSA W59 for a minimum plate thickness to prevent burn-through and I haven't seen any specified.

Do you know if this situation could impact negatively the resistance of the connection? Would it be where we would see those burn-through?

 

[kingnero]

Assuming there are no abnormalities (so you're using the correct filler for the base material, using a correct set of welding parameters for the joint, the final geometry is acceptable, you're not overwelding the joint, ...) then no, having the roots cross each other will not negatively impact the welded connection. It is basically no different than a multi run weld.

 

[Logan82]

Thank you kingnero. And imagine there is a very thin plate, with a very big weld, say 12 mm. The weld root depth goes through the thickness of the plate. Would you say there would be a problem there?

 

[david339933]

W59 states the fillet weld need not exceed the thickness of the thinner part joined, unless a larger size is required by calculated stress (4.3.4.2.1)
W59 also only deals with materials 1/8" and thicker...otherwise see AWS D1.3.

 

[kingnero]

The weld root depth goes through the thickness of the plate. Would you say there would be a problem there?

=> According to ISO standards, it would fail VT.

 

[Nashanas]

According to AWS D1.1 Table 5.8, the minimum fillet weld size for base metals between 12 and 20mm thick is 6mm.

We recently had similar problem, the thicknesses were a bit larger than yours, when designing the weld size keep in mind the thermal deformation caused. I dont know which process you are using and how long is your beam. Dont go for excessive weld sizes, it will make your process very complicated to manage.

If your deposited weld layer from one side is overflowing on the other side, you probably should perfrom backgouging by grinding to sound metal from the other side before putting weld layer to have acceptable geometry of the weld bead.