"Rich-in-WA" wrote in message
om...
Hello again...

A couple months back I got some great advice from the group
concerning a set of large steel brackets I'm fabricating for a timber
frame house we're building. I have sixteen brackets to make, each
with five pieces, weighing about 40lbs total per assembly when done.
I designed the brackets so all the cutting could be done by my steel
supplier. I now have (32) 1/4"x2"x34" bars that each need six 90
degree bends (insert loud groan). Since I'm doing this in my home
shop, I plan to heat the bar at the bend spot to cherry red with a
MAPP gas torch. I'll then quickly clamp the bar in my (large) bench
vise and (hopefully) complete the bend using a sledge hammer.
My question concerns temper. These parts are grossly
over-designed for aesthetics, but I'd still like them as strong as
possible. Will it do any good to quickly quench the bar in water
after making each bend? I'd imagine that if I just let the bar cool
on it's own, it will end up fairly soft. The steel is nothing
special, just plain structural steel (probably A36) from the local
yard. I don't want to get too fancy here, but if it won't hurt
anything quenching in water seems easy enough to do. As I mentioned
in my original post, I plan to finish these parts by planishing them
with a ball peen hammer and then following up with some sort of rust
resistant finish.

Hardening the steel probably would not be a good idea. With A36, it's
especially not a good idea. A36 is graded for strength, not for alloy (it's
typically made from re-melted mixed scrap), and you don't really know how
it's going to behave after heat-treatment.

For starters, you don't have to get steel so hot for that kind of bending
that it would quench-harden, anyway. A dull red should be enough to forge it
over, and that's not hot enough to quench-harden.

It's true that you'll probably heat it enough to anneal it, more or less.
But, if the design is overbuilt to begin with, take solace in the thought
that by not quench-hardening it you've improved its ductility. In structural
applications, that can be a benefit. It's less likely to fail
catastrophically.

Good luck with your project. It sounds ambitious and interesting.

Ed Huntress