Time from Quench to Temper ?

[markb]

Heat treating 1084 in an electric oven, I went to 1475 degrees, quenched in ATF at 150 degrees and checked w/file for hardness.

Now to temper it takes the oven an hour to cool to 400-, my temper target.

In the sticky it mentions the stress at the martensite state, after quench (could crack blade)

Any other dangers waiting an hour to temper.

I'm using the oven (PID control) for its accuracy and fear of burning point in forge.

I'm taking notes and doing #d samples, but don't want to continue down the wrong road.

Thanks Mark

[Quenchcrack]

Mark, some folks use a snap draw to prevent cracking between quenching and tempering. If you can find an old toaster over, set it for 200F or so and keep the part in there while your furnace comes down to tempering temperature. You might have to make a very slight adjustment in your final tempering temp but it will not hurt the part. You can leave it in the toaster oven and go directly to the temper furnace when it hits the right temp.

[markb]

Thanks Bob

Garage sales this weekend. I'll get a t/oven.

Also I was wondering if there are any rapid transformations going on immediately after Quench that need to be addressed by the temper, other than the unstable state of the steel.

Mark

[Quenchcrack]

The transformation of austenite to martensite STARTS at about 700F and may not be completed until the part is taken well below 0F. The untransformed austenite (called retained austenite) can transform later after the part has been finished, causing distortion and possibly cracking. If you quench a high carbon steel to room temperature, you will probably have retained austenite. Double tempering will cause the retained austenite to transform to martensite (or other structures) in the first temper and then it will temper the new martensite with the second temper. Some people quench to room temperature, lightly temper, freeze to -300F, warm up and re-temper. This is beneficial to alloys like D2 but not particularly valuable for plain carbon steels. Some folks call this Cryogenic Tempering but it is actually a part of the quench, not the temper.

[markb]

I just got back from my garage sale search. No t/oven

But I found this cool BarBQ:D


Thanks again Bob for that explanation.

Still need a t/oven:o

Cheers
Mark

[Frosty]

Nice BBQ.

Frosty

[markb]

Another related ?
Can I temper at say 400 once, and I think it's to hard, temper again at 450 to soften a little?
Can I go back the opposite direction.

This has prolly been covered but I start spinning looking for these asnswers.

[brucegodlesky]

Good explanation Bob, thanks.

[Steve Sells]

Can I temper at say 400 once, and I think it's to hard, temper again at 450 to soften a little?

yes

Can I go back the opposite direction.

not really, while the for the most part, the highest temper decides the final hardness, all a lower temperature temper later will effect is the retained austenite, that has converted since the last cycle.

[markb]

Thanks Steve

Frosty
The guy says to me when I got it... Be careful you can burn-up all your charcoal if you crank to much. LOL

[Frosty]

Thanks Steve

Frosty
The guy says to me when I got it... Be careful you can burn-up all your charcoal if you crank to much. LOL

Probably why he got rid of it eh?

I bet it puts butt kickin sear marks on a steak.

Frosty

[markb]

I don't know why he sold it, had a lot of sentimental value to him...He and the guy he bought it from both lived in Buffalo , his dad worked at Buffalo foundry.

Blower runs smooth as silk.

I told him I'd take good care of it.

We don't have a grill, so this one may see a steak or two:)

[fat pete]

I got a nice oven yesterday on the way home ....big yard sale.....4 bucks....even has temp settings

[brucegodlesky]

Pete, is that a convection oven? They work much better than a toaster oven, more even heat.

[Quenchcrack]

Mark, how come when I go looking for a rivet forge, everyone has toaster ovens for sale? Nice score.

[johnptc]

mark

another approach is after quench leave the oven door open.....using the open oven like a forge gently heat the blade to 400 ( in and out) check with a temp crayon then air cool.......this works great with 10xx steels i dont know about higher alloyed steels

[markb]

Bob .....Murphy's Law

Thanks for the tip on the convection oven Bruce.

Went today 7am -10:30... micro wave, micro wave, micro wave, geo. forman

Good score Pete

[markb]

John
I like that idea, using the available heat, I'll try it.
Mark

[Quenchcrack]

Leaving the furnace door open at hardening temperatures can be hard on the refractories if they are the hard brick type. Thermal shock can cause them to crack and spall. Should be no problem if you have the ceramic wool type. I have used heavy sections of steel to act as a heat sink to bring down the furnace temperature with less thermal shock. After you remove the blade, turn the temp down, put it a few big blocks of steel and they will draw the heat out pretty quickly but without damage to the brick.

[markb]

I have a soft brick or maybe cast refractory, very soft. Replaced the door with ceramic wool.

Good tip. I have several 3/4" X4"x6" plates I use to heat the anvil.

Thanks everyone for all the help.

Mark

[mcraigl]

Mark,
Here's some yardsales with toaster ovens:

New & Used Yard Sale June 27


! MOVING SALE ~ INSIDE ~ EVERYTHING MUST GO !

and a countertop convection oven:
Emerson Countertop Convection Oven

an undercounter toaster oven:
Toaster Oven, Under Cabinet Mount

I know some of them are already past. The first link is this weekend though, so you ought to be able to get there early and score one. I picked one up two weeks ago for 5 bucks, and it didn't look like it had ever been used. Pretty sweet to set the temp on the toaster oven and the kiln at the same time. Blade comes out of kiln, into quench, wiped oil off, into toaster oven for temper. About that fast...