Limit throat thickness for fillet welds, Inspectors view? 4

[IJR]

My dear friends

At design time, we limit throat thickness to 0.707x min plate thickness, which implies that length of the leg can not be taken to be more than the plate thickness

But that is for calculations.

I am looking for a perspective from Welding Inspector's view

What is the concern if leg length happens to be somehow larger than the thickness of the plate(in other words throat thickness is larger than the above limit)

I have posted this one on AWS forum, your permission assumed granted.

Respects.
IJR

 

[PSlem]

I'm not an inspector, but I have been researching weld strengths for an ICC submittal and found one spot on the web that talks about under spec'ing the weld material for cost savings. In this application there may be no problem. In most, the weld steel is better than the base material so if the ratio of weld size/material thickness times the ratio of weld material/base material strength exceeds 1/.707 you will get a base metal shear.

 

[Rich2001]

I am not aware of anything prohibiting fillet welds that are oversized, unless they exceed the maximum size for single pass fillets. This does not apply where multi-pass fillet welds are utilized.

However, I have rejected items due to excessive distortion due to heat input during the deposition of oversized fillet welds.

Here are a few links with some useful information

http://www.twi.co.uk/professional/protected/band_3/jk68.html

http://www.twi.co.uk/j32k/protected/band_3/jk33.html

http://www.twi.co.uk/j32k/protected/band_3/jk66.html

http://www.jflf.org/pdfs/papers/design_file3.pdf

Vita sine litteris mors est.

 

[metengr]

Oversized fillet welds provide no additional load-carrying capacity if they exceed the thickness of either member being joined, as in a lap joint. In fact, the fatigue strength can be reduced by having an oversized fillet weld.


There have been several AWS papers discussing the effect of weld penetration into the base metal. In this case, credit can be obtained for reducing the fillet weld size and not increasing it.

 

[DRC1]

Min. weld size refers to a filet weld on an edge, such as in a lap joint. Max weld size is 1/16 less than plate thickness. For desiign puroses, weld is assumed to be welded at a 45 degree angle. Thus the throat is the distance from the apex of the joint to the middle of the leg, which is .707 times the weld thickness.

If you are actually welding to an edge of the plate, it is best if the weld is held down slightly from the top. Also gives a muchbetter looking weld. Otherwise, if there is no edge to the plate, such as a t-joimt, a larger weld is okay. It sometimes relives problems with a sligt amount of under cutting, which can ocurr esp. in field welds. Larger welds do need to bebuilt up in multiple passes.