Heat treating bicycle rear derailer hanger after bending
 

I know I should have hit the hanger with a torch before sending it out, but
alas, I was so stricken by the drive train failure I skipped that.

Now that the crucial bending is done, for the second time since I have had the
bicycle, how can I heat treat the hanger to keep it ready for the next time I
snarl my gears?

There is something called "spheroidizing". What else is there? Annealing.
Quenching is unlikely. Tempering. That's all, folks, as far as I know.

I have a couple bottles of propane and couple MAPP and two big head torches.



My physics project at NVCC:
Google Groups, then "dgoncz" and some of:
ultracapacitor bicycle fluorescent flywheel inverter

Heat treating bicycle rear derailer hanger after bending
 

Heat treating bicycle rear derailer hanger after bending
 

" Doug Goncz " wrote in message
...
I know I should have hit the hanger with a torch before sending it out,
but
alas, I was so stricken by the drive train failure I skipped that.
....
There is something called "spheroidizing". What else is there? Annealing.
Quenching is unlikely. Tempering. That's all, folks, as far as I know.

Spheroidizing (has nothing to do with Spehro ;) is converting carbides in
white cast iron to spherical graphite nodules. This process makes malleable
cast iron.

Annealing is to remove stresses either from working or heat treating.
Softens the material and/or relieves stresses. Quenching is usually used to
harden, followed by tempering.

What's your hanger made of? Mild?

Tim

--
"I have misplaced my pants." - Homer Simpson | Electronics,
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Heat treating bicycle rear derailer hanger after bending
 

From: "Tim Williams"

Spheroidizing (has nothing to do with Spehro ;) is converting carbides in
white cast iron to spherical graphite nodules.

OK, I kind of remember that.

Annealing is to remove stresses either from working or heat treating.

Yep.

Quenching is usually used to
harden, followed by tempering.

Yep.

What's your hanger made of? Mild?

I assume it's mild. But it could be fully annealed high strength, too. It's the
integrated hanger and dropout, about 5/16 inch thick, with bosses around
dropout and hanger, that is, a thinner, yet substantial neck that is engineered
to bend.

So I thought if I plugged the hanger threads with a crank bolt, then torched it
a good long while, it'd be fully annealed and ready to bend again. Probably
should have fully annealed after the accidental bend, which may have work
hardened the hanger neck.

Seems clear now. The right way to repair MUST be get everything out of the way
after the accident, torch it, rebend it, torch it again. Yes?

LBS: Local Bike Shop (Performance, etc.)

FBS: Fake Bike Shop (No torch permitted on premises, no operator, no
understanding. If it breaks, buy a new bike.)

Framebuilder: Opposite of FBS. Do not ask this fellow to function as your LBS.

:)

But do I harden it a LITTLE to give it some strength after annealing, that is,
redden, quench, polish, and temper way down toward full temper but not all the
way. Actually a full temper is stronger than a full anneal, right?



My physics project at NVCC:
Google Groups, then "dgoncz" and some of:
ultracapacitor bicycle fluorescent flywheel inverter

Heat treating bicycle rear derailer hanger after bending
 

" Doug Goncz " wrote in message
...
I assume it's mild. But it could be fully annealed high strength, too.
It's the
integrated hanger and dropout, about 5/16 inch thick, with bosses around
dropout and hanger, that is, a thinner, yet substantial neck that is
engineered
to bend.

Well if it could be anything, that doesn't help much. :^) If it's an air
hardening steel (like 4340 I think?) it'll crack if you quench with water.
Low carbon 1020 doesn't harden per se, however it is definetly stronger
after quenching from an orange or yellow heat (did this the other day with a
coat hanger, incidental to more heat treating ... incidentally!). 1040 and
up get glass hard and must be tempered after quenching.

So I thought if I plugged the hanger threads with a crank bolt, then
torched it
a good long while, it'd be fully annealed and ready to bend again.
Probably
should have fully annealed after the accidental bend, which may have work
hardened the hanger neck.

Nah, a small bend won't really work it much. If it's mild I wouldn't worry
about it; annealed 4140 supposedly is extremely ductile as well. (30%
elongation is it?)

To anneal just about anything, you only need to heat it until nonmagnetic
then cool at a rate slower than causes hardening... although I'm sure
"slower" steels like air hardening alloys need much longer soaks.

Seems clear now. The right way to repair MUST be get everything out of the
way
after the accident, torch it, rebend it, torch it again. Yes?

Not necessarily. Your part might need the work hardening to strengthen it.

But do I harden it a LITTLE to give it some strength after annealing, that
is,
redden, quench, polish, and temper way down toward full temper but not all
the
way. Actually a full temper is stronger than a full anneal, right?

Can't do heat treating with unknown metal as I mentioned above.
I assume this "full temper" means either temper for ideal strength vs.
toughness, or fully tempered, temperature-wise (which would be up to a dark
cherry red, just about; not the more orange temp used in hardening)? In
either case, yes it would be a lot, and little stronger (respectively) than
an annealing. Remember tempering is like...controlled annealing. The full
deal (orange heat, slow cool) tempers out every last bit of stress in the
metal.

Personally, if I were going to fix your mount dealie, I'd spark it with a
grinder to get an idea of what kind of alloy it is, hot or cold forge it
back to shape then heat treat if necessary. Since I don't like unrequired
manual labor I'd let you polish it. :^)

Tim

--
"I have misplaced my pants." - Homer Simpson | Electronics,
- - - - - - - - - - - - - - - - - - - - - - --+ Metalcasting
and Games: http://webpages.charter.net/dawill/tmoranwms