Axial tearing on cold formed bends (316L)

[waynebgordon]

Would anyone know why cold-formed bends exhibit axial tears after bending?
The tears are not on the bends, but just before them on the straight portion.
There are plenty tooling marks on the external surfaces.
What are they doing wrong with regards to the bending process?

 

[kingnero]

What material, what condition, wall thickness and diameter, radius of the bend, what kind of tooling, dry or lubed, with or without mandrel, are those trough and through tears of just markings on the outside surface, ... ?

An exhaust manufacturer where I provide welding consultancy, employs two engineers that only focus on bending. This is a much more complex production process than many would think. Many things can go wrong there...

 

More information is needed.
To all of kingnero's points I would add:
What is the nickel content of the 316SS? Formability of the austenitic SSs is sensitive to the work hardening characteristics, which is strongly dependent on the Ni content.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[EdStainless]

Bar? Plate? Tube?
Starting properties?
Radius of bend?
This likely has to do with issues of clamping and how material is allowed (not) to slip into the bend tooling as the forming progresses.

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P.E. Metallurgy, Plymouth Tube