The Hurdy Gurdy Man wrote in message news:SKVAb.
Finch writes that post-weld stress relieving of a weld in chromoly steel
using a torch is completely worthless because proper stress relieving
requires a six hour long process that simply can't be achieved with a
torch.

"Stress relieving" 4130

True Temper has done a great deal of fatigue testing to determine the
proper methods for joining 4130 steels. One of their engineers told
me that they found the best fatigue strength came with a low temp
pre-heat, and then after welding, just bringing the area up to
400-600F. I heard the same from the guy who taught me TIG welding,
and his background was in the Aerospace industry. These temps aren't
going to alter the grain structure, just put the area through an
expansion/contraction cycle. Theoretically, it shouldn't make any
difference, but I'll take test results over theory. BTW There is a
whole industry devoted to fatigue testing of bike frames and
components.

The best way to do this is with a propane torch. When you start to
heat steel with propane you get a shiny wet film on the steel. This
goes away at about 400F.

4130 filler rod.

ER80-S2 is usually used with plain "Aircraft grade" 4130. See
http://www.lincolnelectric.com/knowl...hrome-moly.asp

However, an increasing number of bike builders are using a stainless
filler, Weld Mold's Polytensile 880. http://www.weldmold.com/800.htm
It welds very nicely and has good mechanical properties, 110 kpsi and
35% elongation. It's expensive, about $15/lb. But a whole bicycle may
only need 3 or 4 sticks of 0.035" diameter rod. (When you are trying
to save grams, you don't go broke buying filler ;-)