Bending Stainless 440C
Bending Stainless 440C
(OP)
We have come across a situation in which we have 2 bends on a 5/8" dia. bar of 440C stainless, annealed and recorded at 225 Brinell, where we have compressive failure on the one bend and not the other. The bar is 20" in length with 2-90 degree bends located 5 inches apart. The bar also gets machined to an external 3/8"-16 thread 1" in length. The bend closest to the machining is consistently failing, while the bend further from the machining is fine. We are using a tube bender with the same setup and clamp area for both bends, 1 7/16" inside bend radius. It also does not matter as to what order these bends are made, same results occur. Is there any good reasoning why the bend closest to the machining is consistently breaking?





RE: Bending Stainless 440C
RE: Bending Stainless 440C
RE: Bending Stainless 440C
RE: Bending Stainless 440C
I envision a long bar, with approx. 2" protruding into the working gap of a lathe. The remaining 18 in. or so is hanging off the back of the lathe chuck and running out thru the tailstock. If not supported, the 18 in. tail may be whipping/vibrating during machining. This may work-harden the material near your bend, or possibly cause fatigue (but you don't say the material is cracking, but failing by buckling?)
RE: Bending Stainless 440C
RE: Bending Stainless 440C
RE: Bending Stainless 440C
You are thinking in the same path as we were. We took a piece that was not threaded, and bent the end. We matched the distance from the bend to the end of the bar, to be the same as the distance from the threads to the bend. Result: a clean bend with no cracks. We actually even bent this to a 110 degree angle with no cracks.
RE: Bending Stainless 440C
RE: Bending Stainless 440C
RE: Bending Stainless 440C
RE: Bending Stainless 440C