To what specification was the 316L was supplied?
Is it hot rolled or cold rolled to a certain hardness? TS, YS and elongation?
As the amount of hard working increases, elongation and bendability decrease, so minimum bend radius increases.
ASTM A666 gives the following data for 316L (UNS S31603): Condition YS, ksi TS, ksi % elongation
Annealed 25 70 40
1/16 Hard 45 85 35
1/8 Hard 55 100 25
¼ Hard 75 127 8
½ Hard 110 150 6
ASTM A666 only gives bend test requirements for thicknesses up to 0.1874”.
ASTM A480 gives requirements for 316L supplied in the solutionized-annealed state. YS, TS and elongation are the same as given above for the annealed state in A666 (and also ASTM A167 & A240).
ASTM A480 Bend Test requirements are given in paragraphs 13.3 and 13.4:
13.3.1 [Unless otherwise agreed] “the axis of bend shall be parallel to the direction of rolling.”
13.3.7 The bend test specimen shall withstand cold bending through the bend angle specified without cracking on the outside of the bend.
…
13.4.2 Material over 3/8” [9.5 mm] and up to and including 1 in. [25.4 mm] in thickness shall be bent over a piece (or pieces) of flat stock equaling two times the thickness of the material being tested (2T), allowing the test material to form its natural curve.”
So, if you have hot rolled material, it is close to the annealed condition, and an inside radius slightly greater than 1” (liberal interpretation of para. 13.4.2).
If the material has been cold rolled to ¼ hard, estimating from the elongation values of ASTM A480, the inside radius should be 5X that of the annealed state, i.e., 5 inches.
If ½ hard, use an inside radius of 7 inches.
Alternatively, calculate the inside radius of curvature such that the given % elongation is not exceeded in the outer surface. This gives slightly more conservative values.
For the 40% elongation value of the annealed condition, a simplified solution gives r + 0.5” = 1.40 r, so r = 1.25”.
For 8% elongation, r = 8.33 inches.
Have you been able to find any good references for stainless steel in general? I'm trying to find out the minimum bend radius for 304 stainless. Any help would be appreciated.
