Welding two plates of varying thickness

[SperlingPE]

I have a field situation. I need to weld two beams together at the flanges (one on top of the other). One flange is 7/16" and the other is 7/8".
This will be field welded with fillet welds along the seam between the flanges. Fillet welds will spaced not continuous.
Is there anything that needs to be done to get a good weld? Pre-heat?

 

[metengr]

Yes, surface cleanliness, proper fit-up/alignment and local preheat of 200 deg F. Most important have a qualified welding procedure and welder.

 

[dhengr]

SperlingPE:
Are either of the beams loaded when you are doing this welding? They should really be unloaded and supported before you do the welding, or you will likely defeat the purpose for combining the beams into one section. If the ambient temp. and the material you are welding allow, there may be no need for preheating. Why not a smaller continuous fillet weld btwn. the flgs.? This doesn’t require any weld layout, is usually done about as quickly as the stitch welding, is much cleaner because it has fewer starts and stops, and reduces moisture btwn. the flgs.

 

[SperlingPE]

dhengr
The beams will be un-loaded to do the welding.
Ambient temperature is likely to be less than 50 deg F.
The material temperature will be (or should be ) the same as ambient.

The beams in question are 45 feet long.
I would like to do a continuous weld, but usually am told that this is more expensive.
I will look into it, however.

 

[tbuelna]

This is a sticky problem. First, the large relative difference in section thickness between the two beam flanges presents a problem since the thinner flange will heat faster and have greater penetration when welded. Second, the thinner beam will distort (bow) more readily from weld heating than the thicker beam, so the finished weldment may likely be bowed in one direction.

In general, the one thing I would suggest with your stitch welded beam structure would be to start in the center of the 45' beam, and then alternate the stitch welds from side-to-side and end-to-end. Working your way from the center of the beam to each free end.

Good luck to you.
Terry

 

[SperlingPE]

tbuelna
Thanks - I have been thinking that part through.
Right now, I am going down a different path to avoid having to do this weld.