Quenching *very* large section of 4340

[Philip West 6]

Thinking of doing a home quench of a very large section of 4340.Appx 10"x 6"x 13" the ability to heat it and lift it is not a issue. Even have a creek close by for a large volume of moving water..

Ive quenched a lot of 4140 and 4150 in water when doing large sections(but not this large) with never a problem. Ive never done 4340 though..I was thinking since its such a large section that a moving water quench would be the way to go.

What say you?

[Connor J. Myers-Norton 19]

Just checked the bible, and it says oil only. Sorry

[Jerrod Miller 422]

Water is possible, but quite dicey. You need a lot of it, with good circulation, and it needs to start out at about 110F. And it may still crack. The good news is that oil is pretty safe, and it doesn't have to be a very quick oil. Downside there is that it still takes a lot of oil and you have to make sure it is circulating. Do you need the whole thing hard, or is this a post anvil that just needs the face hardened?

[Philip West 6]

Oil would be a no go, just too much and too large a piece of steel(250#). It would take a 50 gal drum to prevent auto tempering Im afraid. Not to mention a flash fire the size of a car hood.

I know what the books say about oil, but theres just no way..I wish it was 4140 to be honest then I would not be worried because we quench large sections of 4140 in water all the time. It only has to be a couple of inches of the face hardened. I may pass on it but I kinda het to because the price is so good.

Anything over say 2 1/2" thick(4140,4150 etc) that we have ever tried to harden in oil always ends up about 6-10rc softer in the middle of the face than the edges. and that's fast oil out of a heat treat kiln.

A polymer quench would probably work but cant swing that either.

Edited January 24, 2017 by KYBOY

[Brian Madigan 17]

Just pull it out of the kiln and spray it with a hose! It will probably temper itself if it doesn't crack. OR interrupted quench in moving water. If you have an IR thermometer, you can probably dunk it until it reaches 400F, pull it out and dunk it again when it rises above 400-500F. Just keep it above ~300F or so.