Heat treatment kiln

A

Artyom Glozman

Joined
Nov 20, 2017
Messages
12
Hey guys, my name is Artyom, and I'm enthusiast knife maker for hobby, recently I started working with a complex heat treatment steels like rwl34 s3v and s30v, and all of the heat processes that required, I'm sending to other people, that obviously costs me more money. I sure need my own kiln/heat treat oven.
THE QUESTION IS: does a kiln for ceramic will do the work for beginning, of course that the temperature is fits and I can program the kiln.
Thanks for all
 
Well, I suppose if you were determined you might be able to make it work? As you already know and have stated, the heat treat protocols are more complex for those steels, and involve varying ramp and soak times. I don't know what kind of kiln you have, but a lot of them have pretty basic controllers, not to mention the larger kilns might take hours to reach temp.
Don't forget you'll also need to set up for quench plates and cryo tempering if you want to do the steel any justice.
I have my own heat treat oven and I still send out any stainless I do, because I figured out long ago that I'd have a hard time actually saving any money by trying to heat treat them myself. Simple carbon and tool steels? Sure, I'll heat treat those all day long... Stainless, not so much.

I know Peter's HT has raised their prices a bit over the years for small numbers, but fellow forum member JTKnives has started offering some pretty competitive options. I'd probably talk to him first before I tried to rig up a ceramics kiln and everything else you'll need to get a decent result.
 
Thanks, but I forgot to mention that I'm from Israel, and to send it overseas will cost me more than a proper oven..
 
To do stainless your going to need a high temp furnace $$$$, stainless tool wrap$$$, liquid nitrogen$$,a dewar to hold the liquid nitrogen$$$, controlled tempering oven$$$ and a hardness tester$$$$. It ends up being a ton of money in the long run to get set up. I thought i was saving money in the long run buying all my stuff but in the end what paid it all off was setting up my heat treating business. The issue you have is you ask if a kiln will heat treat x steel. Well maybe, maybe not. How you get the heat is not important. Whats important is holding it at the exact temp for the 30-40min and shielding the steel from oxygen. Without some kind of shielding you will end up with just about a pile of scale. Next you need to quench it properly and keep it straight. Then you need to get the steel down to the required sub temp which is normaly -320f and hold it there for around 24hrs. Next your going to need to temper your blade at a precise temp and hold that temp for 2 hrs. after all that you then test the steel with a hardness tester and check if the steel got to the hardness you wanted. If not then you put it back in the oven and temper for another 2 hrs at a higher temp.

How many blades do you need to make per year to justify the thousands opon thousands of dollars. hell you could drop 5 grand in the blink of an eye and still not be set up. And to top it all off you are forgetting one valuable tool that you cant put a price on. That tool is knowledge and experience that a professional provides. This includes the hundreds of hours spent on other blades before yours and all the testing and tweaking of heat treating schedules. So the next time you look at the cost of $10-$20 to have a blade heat treated think about the time and investment that was used to provide that service at that price.

I'm not trying to discourage you or anyone else from getting set up to heat treat your own blades. I just want to inform you and anyone else that comes across this thread that its a bit more involved then "will this get hot enough to heat treat x steel" and then get a shock when you see everything else you need to buy.
 
Unless you do 24 blades a year or more, it will not be worth getting a HT oven. A pottery kiln will work for some purposes, but for the high alloy stainless steels, you need a proper knife HT kiln. Find a good person who does knife HT is Israel and send them to him. Check with large machine shops. Many of them have HT equipment and do knives.

Besides the kiln, you will also need a tempering oven, a roll of HT foil, a liquid nitrogen tank, and refilling the tank every two to three months. A hardness tester would also be a needed item if you are going to check your results. All this could cost Between 15,000 and 20,000 shekel.
 
I do agree with you. It cost some money, the stanless foil, the electricity, the aluminum plates , everything cost , but for a long time it could save me more money, and bigger profit. For today, to heat treat 3, 10inch blades it cost me approximately 150$. Without liquid nitrogen ... so I ask if anybody ever tried to do it with ceramic kiln.. because I can get it really cheap...
 
3 10” blades for $150? Sounds like you need a new heat treater. That’s a crazy prize to pay. Through me heat treatment and cryo would be $15 each. At $150 it would almost be worth it to look outside of your country. But first I would look around and see if there is anyone else you can do business with there.
 
Sounds steep with $50 per blade. The only time I sent out I payed appr $5 plus shipping for HT and deep freeze. But I had to wait a little because they were coordinating for many makers.
As for getting a kiln of your own and all that comes with it, you can reason from the purely economical/business perspective or from a hobby/interest/passion one. I am myself a hobbyist just starting out and plan on no more than I few blades a year as things are now. I work only with RWL 34. I sent out for heat treat once, then I invested in my own kiln. I want to do the whole process myself, and it is also more convenient and fun for me that way. I will probably never pay off my heat treat set up from selling knives.
 
Artyom Glozman said:
I do agree with you. It cost some money, the stanless foil, the electricity, the aluminum plates , everything cost , but for a long time it could save me more money, and bigger profit. For today, to heat treat 3, 10inch blades it cost me approximately 150$. Without liquid nitrogen ... so I ask if anybody ever tried to do it with ceramic kiln.. because I can get it really cheap...
Click to expand...
Do you have picture of that kiln or model numbers from manufacturer ?
 
Artyom Glozman said:
Thanks, but I forgot to mention that I'm from Israel, and to send it overseas will cost me more than a proper oven..
Click to expand...

Yikes. I just looked up international shipping FROM Israel to the US, and you're right... It is quite pricey, even for the "cheap" option.

Well, everybody pretty much laid out what you'll need to heat treat even a couple blades. As for whether the specific kiln you're looking to buy will work, you'd have to show us which one you're looking at. As long as the chamber is large enough to begin with, there are ways to upgrade controllers and heating elements in order to get it to do what you need it to do, but it will take time, effort, and money. You'll still need all of the equipment to quench and temper and so on.

One option you MIGHT consider: JTKnives (who posted above) offers both heat treating AND plasma cutting. If you had the materials drop shipped to him from, say, Alpha Knife Supply or New Jersey Steel Baron (both US based suppliers), he could cut out whatever designs you send him and ship you heat treated blanks. If I'm not mistaken, International shipping FROM the US to Israel shouldn't be more than $50 or $100, though it might take a couple weeks. It should still be quite a bit cheaper in the long run, though you will have to work and finish your blades in the hardened state, which is a little bit more of a pain, but it's still an option over spending thousands on your own tools.
 
ALL the people gave you sound solid advice. Everyone of them. However I'll offer a different path IF you or your buddies are handy with tools and electric. Buy the kiln as cheap as you can get it. Take it apart and only save the door and firebricks. Then make your own. There are lots of tutorials on line most with excellent videos. I used a furnace sheet metal plenum kit for the outer case. You can make it to the size you need. You could even use extra bricks as a double layer of fire brick for insulation and for feet. I built my own probably for $200 as I got a rather large rectangular pottery kiln that folks used the wrong clay in it and ruined it. But it took a lot of time and effort. Some will say I'd been ahead to build knives not ovens. But now I can do both.

I'm only a hobbiest at this point but I like doing it all in house and on the time line I have to do it. I only use SS that respond well with Dry Ice slurry cold treatment, 440C and AEB-L. Yes I'm sure I could pull another point or two with LN but my RH tester shows I'm right where I need to be. My friends and myself have been pleased with the performance.
 
Artyom
In order to get optimal performance from 154CM or one of its clones, the equipment listed by JT is usually required, however an acceptable heat treat can achieved with lesser equipment. Pre-heat is specified to reduce warping by getting all the metal stabilized at a temperature just below the Curie point. Ramping up to temperature, again allows the controlled expansion of the metal to help reduce warping and to start dissolving the various carbide. The soak time is to allow all (or most) of the carbides to dissolve putting more carbon back in the mix so it can again form carbides during the quench (the new smaller carbides are supposed to be more desirable). The foil wrap is used to limit the oxygen exposure of the steel to reduce decarb and oxidation. The cryo treatment reduces the retained austinites. So ideally you use all these things to hopefully gain optimal heat treatment.
BUT, (yes, all caps), since you are a hobbyist and are probably trying to obtain good heat treat vs optimal, I would suggest trying to heat treat with what is available.
If you use a plate quench (which usually holds the blade straight during quench) you might get by without the preheat at 1400°f.
The part that can't be skipped, is the soak at austenizing temperature. So what ever kiln you use must be capable of reaching the proper temperature.If no heat treat foil or controlled atmosphere is used you will have to grind off a lot of scale and decarb after heat treat. An overnight soak in vinegar will usually soften the scale enough where a new zirconia belt can remove it.
There are ceramic coatings which the blade can be coated with to act as a shield from oxygen during heat.
Overnight in the freezer followed by three temper cycles will remove most retained austinite.
treat.
So give it a try. Half the fun of making something yourself is learning how to work around obstacles.
Jim A.
 
Most of Jim's advice will work fine for a hobbyist knifemaker. Only thing I disagree with is an overnight in a home freezer (0 to 10F) will not remove most of the retained austenite. However, a bath of dry ice (-100F) and alcohol will remove most of it. This is what many of us do instead of liquid nitrogen. LN does other things, but the RA is finished converting at -100F.

A DI bath for a couple blades is usually a few pounds of DI and half a gallon or so of denatured alcohol. You can reuse the alcohol over and over again. The DI can be bought at many local grocery chains.
Just plate quench the blades, remove from the plates after 60 seconds, and let cool to room temp. Immediately place in the DI bath and leave for 10-30 minutes. Remove, let warm up to room temp. and do the two temper cycles. This will give a perfectly suitable HT for stainless steel.

I also highly recommend wrapping the blades in HT foil wrap. The damage to an exposed blade surface is pretty severe at 1950F for 30 minutes.

As said by Jim, the ramp and pre-soak times are nice but not all that necessary on modern blade steels. Many folks heat the oven to 1950F and add the blade packet. Once the oven rebounds to 1950F, start the 30 minute clock.
 
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this the kiln i can get. will it work?
l&l kilns, model number e23s-380-3py, serial 030805l, 380v/3 phase wye, max temp 2350f(1290c)
 
image not posting, link not right.

I see that the kiln is three phase 380V … do you have three phase 380 volt service?
 
If my math is right that kiln would take a good while to get up to temp. It’s sitting at 7600 cubic inches and if it had the same heating density as my oven it would require almost 42,100 watts. I bet that has a heat up time of what 3-5hrs.
 
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