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burnmetal973
08-31-2010, 06:53 AM
I'm working on a job that requires 3/4" X 3" AR400 flat bar to bent to a 45 as tight of a radius as possible. Does anyone know exactly what the tightest radius I can get out of it is and what dies I need? I have a 1000 ton break.

Pyro J
08-31-2010, 09:48 PM
Welcome to the forum. I think you have enough press to do the job, I just don't know anything about bending of the ar400.

Someone here should be able to shed some light on that.

John

greywynd
08-31-2010, 10:16 PM
Interesting project..... but you may have to find someone that knows some metallurgy. AR400 usually has to be pre and post heated when welding, so heating it to make it a sharper bend may also be out of the question. There's a couple guys on here that seem to get into this sort of stuff more regularly, trying to think of who they are though!!

USMCPOP
09-01-2010, 08:44 AM
One hit from here: http://www.mcneilus.com/Specifications/SpecBook/WebPageSpecbookContents/P.59,60.htm

Excerpt:

Recommended Fabricating Practices for Cold Forming

(Bend axis transverse (perpendicular) to rolling direction “across the grain”)*

Suggested inside Radii for 90 degree bends for various thicknesses expressed in terms of “t” where t = material thickness

AR400 – 155,000 psi Typical Yield Strength (No ASTM exists)

Thru .787” 3t (use 13.5t bottom die opening)

Over .787” 4t (use 18t bottom die opening)

** The radii listed are the minimum recommended for bending sheets and plates without fracturing in a standard press brake with air bend dies. Other types of bending operations may require larger radii or permit smaller radii. The minimum permissible radii will also vary with the design and condition of the tooling.
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Other sources said the bend radius should be 8 or 10 times the thickness.

digr
09-01-2010, 05:35 PM
I think you can bend it but you will have two pieces when you are done. It will break unless heated. I would NOT try it someone could get hurt!!!

Whitetrash
09-01-2010, 06:30 PM
I remember doing some slight bends in AR plate years ago in the fab shop. Nothing even approaching a 45 and not as thick as what your contemplating. I believe it's going to be a tall order to pull it off without breakage and pieces flying like Digr said. What I do remember from when we did Ar was we radiused the edges of the plate with a grinder so there were no sharp corners and heated the bend area with a rosebud to around 700 degrees (This is going back 20+ years so I'm not positive on the temp) and hit it with the brake when the Tempilstik melted and we still snapped some.
Here's a neat bending calculator I stumbled on when I was looking for confirmation on that Temp.
http://www.jorgensonmachinetools.com/press-brake-tonnage-calculator

precisionworks
09-06-2010, 07:47 AM
some slight bends in AR plateThe fabrication shop often did this on AR400 plate, usually 1" thickness, but the bends were no more than 15 degrees. Preheat with a rosebud "for a while" (no TempStick or IRThermometer) & bend. Never saw one snap, but they used lots of preheat & very little bend.