Bending of Hot Rolled Plate 1

[JCWilson]

In our line of business we often specify a lot of bent plate fabrications, typically from 16gage cold-rolled steel sheet to 3/8" hot-rolled plate. Often, we take it for granted that the materials are "bendable" and that there will not be any adverse affects from the bending process.

It was recently brought to our attention that a fabricator was trying to bend 50 ksi 1/4" steel plate with a tight radius of about 1/2" to the outside edge. When the bend line was parallel to the grain orientation, significant tearing/cracking was observed. When the bend line was perpindicular to the grain, the texture of the grain could be observed after bending, but it did not appear to crack.

Is the plate acceptable in this condition where the bend is perpindicular to the grain? Where can I find design data as to the limitations of bending steel plate of verious grades, including cold and hot rolled.

 

[smcadman]

Generally speaking, concerning hot-roll, cold roll and even pickled-in-oil steel, grain direction shouldn't matter whenever you follow a general standard for air-bending using 1 m.t. for the punch, and 8 x m.t. for the die. Also when bottoming and coining, we used 1 m.t for the punch, and 6 x m.t.
(where m.t. is the material thickness)

Flores

 

[JAE]

AISC Steel Manual (ASD) Ninth Edition - page 4-174 has a table - "Bent Plates - Minimum Radius for Cold Bending"

 

[Ron]

Is the plate acceptable? Depends on the application, applied stresses, cyclic loading, corrosion potential, and other factors. I would typically reject the material if cracks visible.

Your radius could be a bit tight for the actual material properties though it might be OK for the "class" of material (see JAE's reference for material class). I would suspect that your material's elongation properties might be a bit off. If you are on the low end of the elongation spec, you are more likely to get this problem.

Not sure why you are seeing grain preference. Shouldn't happen for typical steels.