Welding vs Bending
Welding vs Bending
(OP)
A question arose today... If 2 plates welded together at a right angle with fillet welds, are stronger than a single plate of the same thickness and material bent on a brake to form a right angle. I have always been informed that a welded part is stronger at the welds than the material itself if welded correctly. I have also been told that when metal is bent it alters the structure of it in a way that it is weakened due to the plastic deformation. Does anyone have any documented proof of this or perhaps some simple calculations to prove it.





RE: Welding vs Bending
This is not totally correct. Weld metal strength should be equal to or stronger than either of the base metals being joined. In some cases the weld metal strength may exceed the base metal strength, but you still have the affects from heat of welding that alters the mechanical properties of the plate material surrounding the weld region.
So, in essence you still have a local region in the base metal adjacent to the weld region that could be weaker in comparison to the weld or base metal. Also, fillet welds by design have limited load carrying capacity in comparison to a full penetration weld (which is what I believe you meant in your OP).
RE: Welding vs Bending
RE: Welding vs Bending
RE: Welding vs Bending
How thick are the plates. What is the material. What is the bend radius or weld detail.
Some materials work-harden when bent, and may actually get stronger. Some materials weaken in the heat affected zone.
RE: Welding vs Bending
RE: Welding vs Bending
However, the welded joint will have to be checked and performed by a capeable welder to have capacity. I also agree it should cost more to have the welded joint.
RE: Welding vs Bending
Not true. Fillet welds have inherently poor fatigue properties in comparison to full penetration welds. Also, most code and standards limit the use of fillet welds and require a hefty penalty for their use versus a full penetration weld.
RE: Welding vs Bending
Good luck
luis marques
RE: Welding vs Bending
But on the other hand, depending on your loading condition, those fillet welds could have poor performance as well. What's the application?
Hg
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RE: Welding vs Bending
RE: Welding vs Bending
Hg
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RE: Welding vs Bending
RE: Welding vs Bending
Why bend this or weld this? It seems like angle iron 5 x 5 x 3/4in would meet your needs. Is the material grade exotic?
Regards, RAF
RE: Welding vs Bending
RE: Welding vs Bending
I routinely bend plates to form angles for misc. attachments of carbon steel, but very often for stainless steels or other alloys where shapes are not available.
But for pressure applications, like maybe a rectangular shaped chill box or something of that nature, I would select welding the corners as my preferred method.
If you bend plates for shapes, like angles, so many factors are involved such as grain stucture, grain direction, radius of bend, radius of bend die all vs. thickness of plate being bent. Often times thick pieces start requiring such a large radius bend that either asthetically or physically it become impractical to bend them.
all things considered, if it a short piece, I would just go ahead ad place 2 plates corner to corner and weld both sides. takes longer to move through shop to pressbrakes and to set it up, than to weld it up.
Long pieces like stiffener lips on baffles and such, will be taken to press brakes.
In these "non-pressure" application it is more economics than anything for us and do what suits the particular situation.
RE: Welding vs Bending
Good Luck whichever way you do it.