Bending test of titanium alloy weldment

[mrmalcolm]

I have a consultation regarding the bending test of titanium alloy welding

ISO 15614-5
Quote
The diameter of the former or the inner roller shall be 6 t except for material group 51 when 4 t shall be used. The bending angle shall be 180° for parent metal with elongation A ≥ 20%. For parent metal with elongation A < 20% the following formula shall apply:
d=(100*ts)/10-ts
Unquote

(1) Bending angle and bending diameter for group 51 with elongation A ＜ 20%
Which of the following viewpoints is correct?
a) Bending angle shall be 180° and bending diameter shall be calculated according to the formula
b) Bending angle shall be 180° and bending diameter shall be 4t

(2) Bending angle and bending diameter for material group other than group 51. The elongation of all material groups :A ＜ 20%
Which of the following viewpoints is correct?
a) Bending angle shall be 180° and bending diameter shall be calculated according to the formula
b) Bending angle shall be 180° and bending diameter shall be 6t

 

[kingnero]

If A < 20%, the formula should be used (no matter the alloy).
Note: the formula is incorrect, it should be A in the denominator.

BTW, good luck bending welded titanium... Can't say for sure for gr. 51, but we've had quite some difficulties with Ti-Al-V alloy.

 

[EdStainless]

The bend angle is always 180deg.
For A>20% group 51 is always 4t and others are always 6t.
For any alloy with A<20% the formula is used for the inner roller diameter.

Are the elongations the specified minimum for the alloy?
And yes, bending Ti welds can be delicate.

 

[mrmalcolm]

Thank you for your professional comment.
We agree that bending of titanium alloy weldments is not an easy task. AWS D1.9-2015 Structural Welding Code-Titanium has also been reviewed. It has been noted that its requirements for bending tests are different from ISO standards.
Quote
AWS D1.9
Part B—Types of Tests, Test Methods, and Acceptance Criteria
3.11.2 Test Procedures—Bend Tests—Plate and Pipe
3.11.2.1 Bend Test Fixture. A wraparound fixture (Figure 3.16) shall be used. The face surface of the specimen is turned toward the outer roller for face bend tests, the root surface for root bend tests, and the side with the larger discon tinuity, if any, for side bend tests. The specimen shall be wrapped around the center roller by a 180° movement of the outer roller.
Unquote
The bending angle and bending diameter are shown in Figure 3.16.
AWS D1.9 have much lower requirements for bending tests than ISO 15614-5, while bending diameter in AWS D1.9 are greater than ISO 15614-5. In practice, requirements for bending tests of ISO 15614-5 are too strict and difficult to achieve.
What do you think about this?

 

[EdStainless]

I have seen more than one case where samples all passed the AWS tests and all failed the ISO tests.