Heating carbon steel blades in an electric oven?

L6steel

L6steel

Joined
Sep 23, 1999
Messages
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How many of you use an electric oven to heat your carbon blades for heat treat?
I'm going to start doing this and was wondering if I need to use any blade coating like Turco. Is that just necessary for flame contact?
Any tips you can give me will be appreciated!
Take care! Michael
 
Heat is heat whether it comes from, coal, gas, or electric.
 
First of all let me say that I am an absolute amateur trying to learn everything I can about knife performance. Here is what works for me.

In heat treating HC such as 1095 and 1084 I obtained a small used pottery kiln and pyrometer. I heat HC to 1425-1450 F and let soak from 10 to 15 minutes depending how thick the blade is. I then remove the blade from the kiln and quench as quickly as I can in quenchant heated to 125 F. I keep it there for as long as I can hold my breath without passing out. Im not timing anything by doing this, I just dont want to breath the smoke. I then put the blade in a preheated toaster oven set about 525 F measured with a thermometer for about 1 1/2 hours. About this time my kiln has cooled to 600 F. I then put the blade in back in the kiln and draw it for another hour or so at 600 F. This, by what I have read, gives me 56 - 58 RC.

I have heated my blades using a hollowed out K23 fire brick and two propane torches. You can get a pretty decent even heat with this. I never have got an even consistant heat by using a torch or gas stove alone. Only with the one brick forge or electric kiln gets the even heat that I want.

Some like to temper in the low 400 F. The first 20 or 30 knives I made were in this range but they were much to hard for me to sharpen.

Randall knives heat O-1 steel and quench at 1475 F and temper at 571 F for their blades. Who can argue what they do is wrong?

Again, im not an expert but I get decent results with this. One knife I know field processed two elk and two deer last fall with this heat treatment and is still sharp.

Joe Yanta
 
I am HT'ing four 52100 blades this evening in the electric oven. I use Brownell's PBC coating on oil quench steels. Clean any coating residue from the oven before HT'ing foil wrapped steels. I found that PBC will eat through stainless wrap at higher than PBC recommended temperatures (PBC is recommended to 1650 F).

RL
 
Mike I use an electric oven for my heat treating. I wrap stainless but do not do anything to protect the carbon steels. This works for me because I grind my folder blades after heat treat. I also throw all of the blades and springs back on the surface grinder to clean everything up. I have tried the Turco and found that it causes pitting and I had to regrind all surfaces again. I dont reccomend turco.
 
Is Turco one of those coatings that you have to wire brush off?? I have some NO-CARB by Heatbath that is like that. I refuse to use it. Might as well grind decarb instead. Brownell's PBC does well and comes off in boiling water, which is tailor made for holding prior to temper . I am finding that the secret to using it correctly is to be sure the steel is equalized at least to 500 F to get it stuck to the steel uniformly and completely. Bruce Bump got me started using PBC and I am glad.

RL
 
How many of you use an electric oven to heat your carbon blades for heat treat?
I'm going to start doing this and was wondering if I need to use any blade coating like Turco. Is that just necessary for flame contact?
Any tips you can give me will be appreciated!
Take care! Michael

I do Michael. Generally there is no need for blade coatings, especially since carbon steels don't usually stay in at long or high enough aus temps to warrant a real problem found in stainless or most tool steels for example. I.e. bad decarburization/oxidation. Also, its possible to run into snags with proper through hardening of your carbon steel.

Good luck.
 
The reason I asked the question Michael is that I use gas to harden and electric to temper. I agree with mete, heat is heat.
I've tried a lot of coatings and different witches brews but as a rule, they are more trouble than they are worth. I am talking about simple carbon steels not fancier steel or the shiny stuff!
 
I do a lot of heat treating -- a few knives but a lot of gun parts and like many of you I use a gas oven for hardening and then an electric oven for tempering. I now use PBC as a coating on items that I put a good finish on before hardening and have found it both easier to apply and leaves a pit free finish after quenching. I feel this method saves me a lot of finish sanding time as steel is a lot easier to sand in the soft state than after hardening.
When I do annealing it is likley to be a can of a hundred or so rather small parts so I just fill in fine sand around the parts. This helps in reducing decarb and also cools the parts much slower than if they are not packed in some thing.
A caution to those of you using electric ovens for hardening. DONT do any hardening that could be considered case hardening in an electric oven as the heating elements will take on some of the carbon in the atmosphere of the furnace and become brittle and then brake during cooling.
Good luck
 
peter nap said:
The reason I asked the question Michael is that I use gas to harden and electric to temper. I agree with mete, heat is heat.
I've tried a lot of coatings and different witches brews but as a rule, they are more trouble than they are worth. I am talking about simple carbon steels not fancier steel or the shiny stuff!
Click to expand...

well ??? almost
unless its a gas atmospheric generating oven they rock :)
a gas forge is partially atmospheric also because it's consuming O2 .
if it's burning efficient, but can be full atmospheric if built with radiant heat.
but that's only as good as the air the blade hits removing it....
you'll get most of the decarb as you remove the blade from a Forge into the air out side going for the quench..
and the same as the ele oven but with the ele oven you have air in side to cause decarb too.

I'm just talking hardening here
 
I never had much luck with Turco either. I switched to PBC compound several years.

You certainly don't have to use an anti-scale coating. The reason I do is that I can take the blades to the final dimensions and a fairly fine finish before heat treating. My blades are taken to a 400 grit hand-rubbed finish prior to heat treating.

Here's a shot of one just quenched. The blade was edge quenched. The PBC slides off easily on the fully hardened area. The rest cleans off easily with boiling water. In this shot I'm testing the blade with a file.

file-test.jpg


Here is a closeup of the blade where you can see the 400 grit hand-rubbed finish has retained its integrity.

file-test2.jpg


From here it gets a bath in boiling water and then goes straight into the pre-heated tempering oven. This blade won't see the grinder again, except to put on the test edge.

It's like anything else. It takes a little practice. Roger mentioned the key to success. You need an even preheat to somewhere in the neighborhood of 500 - 560 degrees F. and an even coating of the PBC compound. I've had a tutorial on my website for about 4 or 5 years. You may want to take a look. I explain what PBC is, what it does, how to use, where to get it, etc. This stuff is great with a heat treat oven/furnace, not quite so successful if you heat treat at the forge, and you don't want to use it all with the high alloy stuff that requires heats above about 1600 - 1650 degrees F.

Tutorial: Scale Prevention During Heat Treating
 
Guess I missed that one Terry
you know where that is now don't you? Thanks :D


Terry you mentioned the back and tang being at spring hardness
would you elaborate on how this happened by
just edge quenching the blade.
for those who don't know how that happened :confused:
 
"Tough spring hardness" is a bad choice of words. I may need to change that to "tough and springy state", like this ...

bend2.jpg


... or just remove that part altogether, so as not to cause confusion.
 
Wow, I knew this thread would get some action, lol!
Peter, hardening. I have a regular stove that I do my tempering in.
Sorry I didn't answer sooner, I was out of town yesterday.
Thanks for the help guys!
Terry, I'll definitely be checking out your tutorial asap, thanks!
I prefer taking my blades as close to finished prior to heat treat, too.
Take care guys!
Michael
 
L6, Take'em to about 400 grit. I have been pouring some PBC on aluminum foil and kinda just bury the knife in it, tang and all. Let is coat and then gently scape off the clumps of excess before replacing in oven.

RL
 
Dan Gray said:
it does look very painful :D :D
though it doesn't answer the question :confused: :)
Click to expand...
I honestly don't know that I can answer the question. I don't think I have ever had a dead soft back or ricasso when edge quenching.

If I had to guess, it would be that I am getting a partial hardening in those areas above the quench line. It would make sense to me with the steels which we know can air harden to a degree such as O1, 5160, etc. However, I work primarily in the 10xx series steels, with 1084 being the most prevalent, and these don't contain any significant alloying elements unless you count manganese.

Who knows? Maybe it is due (in part or in whole) to my procedures, but I can't bring myself to speculate.
 
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