At 10:45 PM -0700 7/1/02, Mark Bulgier wrote:
>Monkeylad writes:
> > is used to allow the grain
> > structure of the metal to return to the state it was in before it was
>> formed into tubing.
>
>Not quite; annealing makes the steel as soft as it can be, which may or may
>not be the state it was in previously.
The way I learned it was that it was specifically to put the metals
grain structure back to it's original state before forming and the
softness was an after affect. Like I said in the earlier post my
experience is more with brass, copper, and bronze which acts
differently than steels, though the process is the same. For those
not falling asleep here's a link of interest
http://www.efunda.com/
> > The after affects of annealing is "softer" and
>> more "brittle" tube.
>
>I assume this is a typo and you meant "less brittle", or "more ductile",
>right?
"DOH!" Dyslexia strikes again, if it looks right it must be right.
>Not quite; it's the cooling rate (namely, very slow) from above the
transformation temperature (henceforth "TT") that defines annealing.
Too true I just didn't want to far into the TT since that involves
lots of formulae I don't understand too well. Mark breaks it down
quite well in his post and if you really want to know more there are
plenty of charts on-line defining everything he said.
>If you've seen lots of crashed and/or fatigue-cracked frames, you may have
>noticed that brass frames often fail as much as a centimeter away from the
>lug edge, because that's where the steel only got up to silver brazing
>temps.
So bike frames are more normalized than annealed. The area where the
crack forms with brass brazed frames seems to me that that is where
the grain structure changes.
>I hope if you remember one thing about this, that it's "It ain't that
>simple!" Heat treating of steel is a huge field that even the experts don't
>know everything about.
I'm with you 100% on this. My background is in metalsmithing and jewelry making and Mark's built more frames than I ever will so when it comes to how these things apply to lugged frame construction I have to defer to Mark's experience. I know there are material engineers on the list, what have we missed? enjoy, Brandon"monkeyman"Ives Jumping on my "rat" bike to head to work in SB, CA.