I have never used a Heat Treat oven, but starting tomorrow I will...some

Chris Railey

Chris Railey

Well-Known Member
So what is the accepted practice in general when heat treating in an oven. When I harden the steel do I let it ramp up with the oven or keep the steel out and introduce it after the oven is at proper temp? If you leave it out until the oven is at temp how do you know when to start your hold time? For other heats such as refining grain or annealing do I let the steel ramp up in the oven? I know specific steels require specific HT stuff but I am asking in general what is the best practice. Thanks for your responses I have only used a forge or an oxy/acetylene torch until tomorrow.
 
Thanks. I read contradicting info on pre versus post ramp insertion. I figured I would get the right info here.
 
Since I mostly do stainless, I put the blades in when the oven is ramping up. The oven's usually at about 1,000 by the time I get the blades wrapped in foil and I put them in the oven. That gives it time to settle and come up to temp with the oven by the time the oven gets to the intermediate temperature. (there are two set points / soak times for the AEBL recipe most of us use.)

I've tried it all different ways. I've put the blades in as soon as I turned on the oven and let them come up to temp with the oven, and I've put them in at various times during the ramp up. I can't tell any difference in performance of the finished blades. I suppose if you studied them under an electron microscope you may be able to tell which was done which way but in practical usage, no difference that I can tell.

For 10xx series steels, I do what tkroenlein says. Let the oven get to temp. Put the blades in and let the oven temp settle back to normal. The timer starts when the oven settles at temp.

I'm no metallurgist, but my blades work extremely well. Don't overthink it. People made swords that conquered civilizations and changed the course of history before they even had thermometers to tell them what temp they were heat treating them at.
 
John Wilson said:
Since I mostly do stainless, I put the blades in when the oven is ramping up. The oven's usually at about 1,000 by the time I get the blades wrapped in foil and I put them in the oven. That gives it time to settle and come up to temp with the oven by the time the oven gets to the intermediate temperature. (there are two set points / soak times for the AEBL recipe most of us use.)

I've tried it all different ways. I've put the blades in as soon as I turned on the oven and let them come up to temp with the oven, and I've put them in at various times during the ramp up. I can't tell any difference in performance of the finished blades. I suppose if you studied them under an electron microscope you may be able to tell which was done which way but in practical usage, no difference that I can tell.

For 10xx series steels, I do what tkroenlein says. Let the oven get to temp. Put the blades in and let the oven temp settle back to normal. The timer starts when the oven settles at temp.

I'm no metallurgist, but my blades work extremely well. Don't overthink it. People made swords that conquered civilizations and changed the course of history before they even had thermometers to tell them what temp they were heat treating them at.
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Thats another question. What of this foil you speak of? When do I use the foil? For what steels?
 
It’s a stainless foil. There’s 2 grades rated for different temperatures. Stainless steel, due to the high temperature and longer soak times, needs to be wrapped in this foil to prevent decarb when heat treated.
 
Gene Kimmi said:
It’s a stainless foil. There’s 2 grades rated for different temperatures. Stainless steel, due to the high temperature and longer soak times, needs to be wrapped in this foil to prevent decarb when heat treated.
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Ok I got it. Use on SS but its not needed on high carbon. Thanks
 
Well...

There will be large amounts of scale and decarb in the static atmosphere of an oven. Many folks will still use some sort of barrier to protect the blade. This is probably more often anti-scale since the foil envelope presents some unique challenges to the fast quench requirements of simpler steels. Does your oven have a view port of some sort? The ideal way to do it would be to set your oven and let it equalize at temp and then introduce your blades. Allow the oven to readjust, and observe the blades in a view port. When they assume the same color as the kiln walls, begin you soak time. If they are 10XX series almost as soon as they reach temp they are ready. If they are alloyed to any extent then you want to give them a little time at temp.

Depending on the make of you oven, this may be easier or more difficult. I have found some controllers do not like the door being opened and will struggle to hold level, perhaps overshooting after the blades are in. A good controller will have the fuzzy logic necessary to adjust for this and recalibrate for quick regulation.
 
Kevin R. Cashen said:
Well...

There will be large amounts of scale and decarb in the static atmosphere of an oven. Many folks will still use some sort of barrier to protect the blade. This is probably more often anti-scale since the foil envelope presents some unique challenges to the fast quench requirements of simpler steels. Does your oven have a view port of some sort? The ideal way to do it would be to set your oven and let it equalize at temp and then introduce your blades. Allow the oven to readjust, and observe the blades in a view port. When they assume the same color as the kiln walls, begin you soak time. If they are 10XX series almost as soon as they reach temp they are ready. If they are alloyed to any extent then you want to give them a little time at temp.

Depending on the make of you oven, this may be easier or more difficult. I have found some controllers do not like the door being opened and will struggle to hold level, perhaps overshooting after the blades are in. A good controller will have the fuzzy logic necessary to adjust for this and recalibrate for quick regulation.
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No viewport but I do have what I consider to be a good controller. I have a newer Bartlett computer touchscreen. I will be using it to harden some 10XX series steels but mostly to allow me to experiment with some stainless steels. I can see the open no flame inside of an oven to be a great source of scale and stuff I guess I will have to just experiment with all of the above until I get a good process down. I just needed a jumping off point.
Are there any “home remedies” for anti-scale compounds kind of like using Borax for flux? Or am I stuck with using the commercial stuff?
 
No theory here just things I have done(That may or may not really help)....double fold the seam of the foil....fold edges once and tap the crease with mallet...fold again and tap new crease again. Do not wrap the blade tightly...it's not a christmas present (even if it is...lol) you want that blade out of that wrap quickly! I do put paper in the wrap to burn off the oxygen. My knives always come out very clean slate gray. I do wash them in hot water and dish soap and rinse in hot water so they are real clean before wrapping...and a day before wrapping/heat treating...I don't know what water does to a furnace and don't plan to discover.

Make your packet 3-4 inches longer than the blade(s) being heat treated. Then when pulling them you can easily cut the packet open while the blade its self still is in the furnace. Of course you want the tang coming out first. I am treating A-2 tool Steel so multiple blades with air quench make the extra foil economical...(it is easier for me to handle 5-7 blades in one wrap than a single blade...but I bolt them together...)

Do a dry run...with no heat. You'll be amazed at what you learn wearing them big goofy gloves...Keep extra grabbing tools on hand....if you drop tongs/pliers you can grab the other set faster than retrieving off the floor....(guess how I learned this one...) make sure EVERYTHING you do is right there...no walking. Out or the foil...out of the furnace...into the quench...whether it be air/oil/plates...(You already know this...just stating for any beginners reading this thread...)

How you handle things right out of the furnace is the main variable you will be introducing to your process. Be methodical. be quick.

Advice from a HT oven semi-noob to a noob... ;)

...and like my sis said when I bought an Apple Phone..."Yer gonna love it...!!!"

She was wrong. I am not.
 
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Chris Railey said:
Are there any “home remedies” for anti-scale compounds kind of like using Borax for flux? Or am I stuck with using the commercial stuff?
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I'll suggest ATP-641 anti-scale paint from Bownell's for the 10xx steels and such. It's what I use on my 1080/15N20 damascus and It's pretty cheap (~$15 for a quart IIRC) and this will last quite a while. It goes on as a thin paint and I'd estimate it'll end up being pennies (maybe a few dimes) per blade.
 
It's going to depend on the instructions for heat treating a particular alloy. I read one set of directions for hardening a steel alloy, I don't remember if it was a complex tool steel or a stainless, and it read to heat the steel to something like 1400° then slowly allow it to come up to target temperature and then soak for a given amount of time before quenching which was probably an air quench. Even if you only do 10XX steels that oven will be great. There's no such thing as too much heat control in heat treating. You might end up wishing that you had two or three ovens.

Doug
 
I only had a chance to HT two knives this weekend. One worked wonderfully one warped like a banana. It did make me think of another question for those of you who HT in batches. Lets say you have 4 knives in the oven. When you start quenching knife 1 by the time you reach knife 4 is the temp of knife 4 still in range? I assume you would close the door each time and hopefully the steel stay warm enough? That about right.
 
I can't say chris...I do batches of the same knife bolted together...air hardening so i get a fan on the set immediately.

I do always hold them spine up even when I've done singles. Perhaps the air getting in on the next knife caused the warp?
 
It was damascus so it could have just been the two different steels. I would not think the air would have been much different than me pulling it out of the forge and sticking it in my tank. The mono steel one did not warp. But hey thats 50%...Batting .500 would get you into the hall of fame so.

I can already tell I am going to really like having the oven option. It opens up a chance for me to play with some stainless stuff so that is coming up soon.
 
After quenching put blade in a straightening jig. A couple pieces of angle iron in a vice works good. Have to do it quick though!
 
Yeah I put it between my quench plates after quenching in oil which I do to keep them straight. Normally I put a 25 pound weight on top but for some reason I did not do it this time and guess what, warp city. I will straighten it in subsequent temper cycles no big deal.
 
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