Posted 20 May 2010 - 06:39 AM
I have been having a lot of problems with destroying bandsaw blades.
I do all of my welding at a good yellow heat and every fold is cut cold (I thermal cycle at each new weld)
after I've done my pattern and drawn my bar out to stock dimension I normalize.
I soak at 1500 for 10 minutes, then 1450 for 10 minutes, then 1400 for 10 minutes, with a full cooling between each cycle.
I have a 30 Gallon drum lined with 2" Kaowool, using a 3/4 TRex burner and an Auber Instruments thermocouple.
and I'm still destroying high quality Olson bandsaw blades (14 Tpi) cutting a 1/4 x 1 1/2 bar on edge.
am I missing something, I've thought about trying a Spheroid anneal by quenching on the second cycle (1450) and going straight back into the fire at 1400.
would that be better? I'm just nervous about quenching a bar that I know has to have a huge grain.
"Wisdom and experience are built of bricks made from the mud of failure" Dr Mike Blue
Posted 20 May 2010 - 08:12 AM
1) Heat to 1550F, Cool in still air.
2) Repeat 1.
3) Heat to 1500F, & quench in fast oil.
4) Soak at 1300F for 1 hour.
Works like a charm for me. The first two heats are just normalization, the quench is to "lock in" my reduced grain size (not sure if this is necessary in a non-hypereutectoid steel really, but I don't want to take a chance...), and then the 1300 subcritical anneal softens it all up. At least, I think that's the way I understood it.
Posted 20 May 2010 - 05:22 PM
As our good friend Kevin Cashen will tell you, don't go above non-magnetic again after the quench on a hyper-eutectoid steel until you harden.
But, you can do the 1300 sub-critical soak and I hope you are letting the blade cool back to room temp in the oven - right?
It's that sloooooooooooow cool that what will give you the spheroidal anneal, after a sub-critical soak, which, Stephan, will cut like butter!
And, you haven't disturbed any grain size by going over non-mag.
As well, your steel matrix is now properly set-up to harden.
You guys know I do a lot of take-downs, and this procedure allows me to thread, drill, tap, etc as much as I want.
I still do all of my cutting with a cut-off saw, but every now and then I use my band saw to cut damascus fittings, etc, which MUST be spherodize annealed, and I've been using the same bi-metal blade in all of 2010 and probably back before Christmas!
The key here, is the post-forging quench, a sub-critical soak, and then slow cool with the oven off over night.