Figured out that a stress relieving step before heat treating completely eliminates warping. Confirmed the theory first with a bad ass metallurgist guy.
See the vid.
I quenched this 4130 receiver from 1600 right into brine, normally that warps it a bit, a bitch to straighten in that state.
With this new method, zero warp..
Update 3/25/07, I"ve had a home heat treat break through! In addition to the 750F for 2hr pre-heat treat stress relieve step, if you get your buddy to stir the living hell out of the brine tank, warping is almost gone! so the combination of very fast agitation in quench and pre-stress relieve is the best one for kiln and brine quench. Note, the direction of flow in your 5 gallon bucket should be INTO the receiver shell opening - that way brine flows into the receiver and cools the inside rail areas very quickly.
You'll notice the back end of the receiver where you holding it does not want to dunk all the way - due to the circuating current.. that was a surprise to me - and the only place i got a litte warping becuase i didn't get it under until a second later.
To harden, heat to 1600F but do not hold, remove, quench into brine @ 3lbs salt / 5gal bucket.
Temper 750F for 1 hr, sets up 42Rc.
Side benefit? The oxide layer formed during the stress relieve pre step protects the steel surface from scale build up & decarburization softening during the high temperature step.