Hi all:
On Wed, 06 Mar 2002 12:32:02 -0500 "Joe Bender-Zanoni"
<velo531@hotmail.com> writes:
> Mark Bulger's comments seem right to me as I have studied metallurgy
and
> have considerable experience with high strength steels, heat treating
etc.
>
> However, the previous comments, I think by Bicycle Mark, about cold
setting
> as a measure of brazing impact on the tubing properties is too simple,
at
> least as applied to rear triangles.
>
[ snip ]
Thank you, I was trying to keep it simple (using the K.I.S.S. system), mainly because I could tell by reading comments from other list members, that there were people out there who didn't understand strengths of metals very well. But I was hoping that someone else would pick up the ball and carry it further. And someone did.
On the subject of quenched-and-tempered ("heat treated") steels...
> Quenched-and-tempered ("heat-treated") steels like 753 can be a lot
stronger
> than normalized steel of the same alloy, but the trick is to not lose
that
> extra strength at the joint. It will lose a fair amount of it, that
much is
> inevitable, but your best hope is to keep the temperature below the
> transformation temp, as well as keeping the time-at-temperature short
as can
> be. Cooling rate doesn't much matter in this case. Silver brazing
usually
> takes place completely below the transformation temp, in the tempering
> range. A little tempering is OK, but it is weakening the steel, so one
> should keep the time in the tempering range as short as possible, and
the
> peak temp as low as possible. Brass brazing takes place above the
> transformation temp, at which point the heat-treatment "slate" is
> essentially wiped clean, and you don't have heat-treated steel anymore,
at
> least in the heat-affected zone (HAZ).
I would like to add just one item. It is also my understanding that one brand of bicycle frame tubing, Tange Prestige tubing is supposed to have a transformation temp. which is a few hundred degrees higher than normal brazing temperatures. I have used this tubing on my MTB (Tange Prestige Mtn OS), lugless, fillet brazed in 1992, and IMHO this is one of the strongest, and stiffest steel frames that I own. And, I do realize that the diameter and thicknesses of the oversized tubes have a lot to do with that. One frame (out of the five that I have built) isn't very much experience, but it's been ridden hard, and even crashed hard once (ouch), and it's still straight & strong, and in one piece.
Thanks for explaining the process better, and refreshing my memory.
"Bicycle Mark" Perkins Fresno Cycling Club - Historian in cold, wet, windy and rainy, Fresno, California, U.S.A.
________________________________________________________________
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today! For your FREE software, visit:
http://dl.www.juno.com/