Acceptable amount of bending for 6061-T6 shop fabrication
Acceptable amount of bending for 6061-T6 shop fabrication
(OP)
Hello, we have a structure that will require some connection brackets to join members that meet at odd angles. There are corner and intermediate joints where the 8" 6061-T6 channels or I-beams meet at 85 degrees, and in one location, 78 degrees. The brackets will be fabricated from excess length material by removing the flange from a channel section, and cutting to achieve an angle bracket with 3.75" and 7" legs.
Can 6061 angle bracket as described above be bent in the shop, by cold work, so to modify the 90 degree angle to an 85 degree angle? Also, can the reverse be done, to modify the 90 degrees to 95 degrees (for the opposite side connection)? Finally, will a 12 degree bend to create the 78 degree angle bracket exceed what can be done in cold work?
The steel shop manager is planning to cut and re-weld each angle bracket to the required angle. I would rather avoid the welding, as it is costly, and the shop I am working with has limited experience with Al welding.
Thanks.
Can 6061 angle bracket as described above be bent in the shop, by cold work, so to modify the 90 degree angle to an 85 degree angle? Also, can the reverse be done, to modify the 90 degrees to 95 degrees (for the opposite side connection)? Finally, will a 12 degree bend to create the 78 degree angle bracket exceed what can be done in cold work?
The steel shop manager is planning to cut and re-weld each angle bracket to the required angle. I would rather avoid the welding, as it is costly, and the shop I am working with has limited experience with Al welding.
Thanks.





RE: Acceptable amount of bending for 6061-T6 shop fabrication
If you can give the thickness of the material I can give you numbers for the recommended bend radii for a cold bend on a particular thickness.
RE: Acceptable amount of bending for 6061-T6 shop fabrication
A CS8 has a flange thickness of 0.41 inches and a web thickness of 0.25 inches, with a fillet radius of 0.35 inches at the inside. The web would be the most desirable to bend for the needed 5 degrees of sweep inwards or outwards.
If 5 degrees is possible, can a 12 degree bend be formed in the same manner? Five additional brackets with a 12 degree sweep are needed.
Thanks.
RE: Acceptable amount of bending for 6061-T6 shop fabrication
If I understand correctly you want the bending of the web to twist the flange either up or down depending on whether you are bending the web the hard way or easy way.
Here is the bend data
According to ALCOA data the min. radii for 1/4 " 6061-T6 is 3t-4t and 4t-6t for 1/2".
The only problem I see is the flange want to wrinkle as you are attempting to bend it.
All the bending I've seen on channel or angle is been in guides.
RE: Acceptable amount of bending for 6061-T6 shop fabrication
I think you have it right. The entire flange is rotated "up" or "down" by 5 degrees by bending along a line parallel to the web and the flange. This would make an "L" shaped angle bracket with an 85 or 95 degree "L" instead of the usual 90 degree "L".
From the ALCOA min radii requirement, it appears that in the metal shop, the part will have to be clamped so that the flange remains planar (no twist). Then for a 1/4" thick web material, the bending radius will be 3t = 3 x 0.25 = 0.75" . The bend should begin at the tangent between the fillet and the web. So the bend would actually begin 0.41" + 0.35" = 0.76" from the outside edge of the web-flange joint, continuing until the 5 degree bend is acomplished.
Mainly I am concerned about creating stress cracks, and the potential for SCC or actual fracture. If I keep within the ALCOA bend radii requirement, then this should be OK, it appears.
The 12 degree bend sounds trickier.
Would cutting and rewelding the piece be easier? My shop manager seems to think so, I think he wants to work with as familiar work as he can. I'm concerned that welding a small piece will weaken the bracket unnecessarily.
Thanks again for the help.
RE: Acceptable amount of bending for 6061-T6 shop fabrication
The weld and the HAZ will end up in the -0 temper, so size the part accordingly or heat treat the bracket after welding.
Mike Halloran
Pembroke Pines, FL, USA
RE: Acceptable amount of bending for 6061-T6 shop fabrication
I figured the 5 degree bending on the majority of the brackets would speed up fabrication, and be cheaper overall. I need about 280 of these brackets fabricated for this project.
Am I wrong?
Thanks.
RE: Acceptable amount of bending for 6061-T6 shop fabrication
I would get me a little jig setup to do the bending before attempting to heat the channel. 6061 responds very well to hot forming in most cases.