Can't harden O1 with HT oven... Where am I going wrong?

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Aug 4, 2008
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Hi Guys,
Last night I tried using my Evenheat oven to heat treat an 1/8" thick blade made from O1 steel.

I normalised 3 times (1600, 1500 and 1475) soaking for 10 mins each time.

Then to heat treat, I set the temp to 1475 F and let it soak for 15 mins. Quenched in Canola oil that I'd pre-heated with glowing hot steel (not ideal, but all I had to work with).

Tempered in the oven for 2 hrs at 250 F just to relieve some stress, and then for 1.5 hrs at 400 F in the Evenheat oven.

Problem is, a file easily bit into the knife. I cleaned off the scale, tried again, same thing. It just seemed to cut the blade way too easily.

I thought maybe the spine (which didn't get submerged all the way) bled heat back into the blade and ruined the heat treat.

So I got more oil and a bigger container.

Then I renormalized today at 1600 F (just the once) and then put the blade back in and set the Evenheat for a 10 min soak at 1250, then straight up to 1490 for a 20 minute soak, then Quenched in Canola oil that I heated up more than yesterday - It was just barely luke-warm to the touch.

After it cooled enough to handle, I quickly checked with a file... It still bit into the steel... I would have thought straight form the quench it would be hard enough to make the file skate...??

Can anyone see any problems with my method - or guess as to where I might be stuffing up?
 
Are you using any type of coating or foil to prevent decarb? That's a lot of heat cycles at fair temperatures, my guess is that you burnt up all the carbon.
 
It may be fine. I have a rockwell tester if you want me to test it for ya. A file is 63-65 rc hardness and will file anything less. Decarb/scale on the surface needs to be ground off as it may be soft a couple thousands deep. I like to use PBC anti-scale compound and have great results with O-1 steel. I make gun parts with it.
 
Randy - That may be the case. I didn't coat it... next time I'll try a thin coat of satanite perhaps.
I did quite a bit of reading and the suggested cycles were 3x normalizing, highest temp being 1600 F. Perhaps being such a thin blade and with the re-heat treating it did burn all the carbon out.


Bruce - thanks for the offer re: rockwell testing, but being in Oz the shipping/customs side of things might make that difficult. I'll check it again when it's done tempering and see what I can find... you may be right, perhaps down a little deeper it'll be harder.
I'll look into the antiscale compound, otherwise as mentioned before I can mix up a wash of satanite which may help too.

Cheers guys.
 
Like Bruce said, go a little deeper. I do 1/8" O-1 all the time in an Evenheat but coat it w/ satinite. I usually coat it for normalizing, then clean and re-coat for HT. Let us know what ya find.
 
It seems ok actually, it's definitely a lot harder to grind... But the file definitely doesn't feel like it skates across it - there is quite a bit of bite there. Edge seems softer than the body.

Think I'll switch to 3/16" steel for a while until I learn the process a bit better.

Is 3x normalizing @ 1600, 1500, 1475 ok or is this causing me to lose too much carbon in the process?
 
I had the same experience with my first 01 in an Evenheat. You have to have decarb protection!!!!
One other thing. If you used stock removal, normalizing is not necessary. Only if you forged it. If stock removal, just set your oven for a preheat around 1250° for 30 or 40 minutes before ramping up to 1475°.
 
The second thing to consider is - Are you sure it is O-1?

Decarb of the surface is most likely the problem, though. After hitting the belt sander, it may suddenly show a shower of sparks.
 
after you temper it a file is supposed to bite it
the file test (for what it's worth which isn't much) is only relevant to try to figure out if you have achieved full hardness. In order for it to indicate anything relevant you need to get through your decarb layer to full-chemistry steel. I put chunks of lump charcoal in my kiln to absorb any free oxygen any time I have steel in it, I have found that I get very little decarb that way, your mileage may vary

-Page
 
What that many cycles at that duration I would vote for the decarb. I am glad Page mentioned exactly what I was thinking as well, the file should skate on as-quenched hardness but not after any ammount of tempering. With your recipe, in the absence of decarb, you should have file skating 65 HRC right from the quench, with a 61-62 HRC after 90 minutes of 400F.
 
after you temper it a file is supposed to bite it
the file test (for what it's worth which isn't much) is only relevant to try to figure out if you have achieved full hardness. In order for it to indicate anything relevant you need to get through your decarb layer to full-chemistry steel.

I put chunks of lump charcoal in my kiln to absorb any free oxygen any time I have steel in it, I have found that I get very little decarb that way, your mileage may vary

-Page

Page

Don't you have any trouble with shorter life on your elements that way?

...the reducing atmosphere removing the protective oxide coating on the elements ?
 
I suppose I would have to have protective oxide coatings on my elements to notice that being a problem. My kiln is a lab kiln thrown out by Cornell university in the 90s I have been using it since with no problem

-Page
 
Your 'recipe' sounds good. I H/T 01 all the time in my Evenheat and I get very satisfactory results. I coat with high temp PBC to prevent de-carb, and I have to re-coat after every cycle ot heat / cool as the coating cracks off as it cools, but with the coating refreshed and good prior to the quench I get no scale at all and just a thin grey coating on the blade after quenching.
I test blades with hardness files, and even the 65Rc file won't touch the blade immediately after quench and before tempering.

Your problem sounds like de-carb, but you might find it helpful (for the sake of consistency if nothing else) to heat the quench oil to a known temperature each time. I quench tip to tang, dunking the whole blade in a steel tube of oil that I pre-heat with a gas torch played on the outside. I measure temperature of the oil with a simple jam thermometer.
 
I just Heat teated my first couple 0f stock removal 1/8" 01 blades in my Evenheat furnance. My procedure: wrap in foil, soak at 1500 for 10 minutes, as quickly as possible snip foil and drop blade into 125 to 150 degree canola oil. Let cool till able to handle it then into the 350 degree oven for two hours. Comes out at around 58 RC.

Tim H
 
I vote for decarb, too. You can always take a piece of stock, HT it with the same process, then break it in a vise and see how it looks. Should resemble fine, grey velvet.

I suspect that all the carbon is gone from your edge.

RJ
 
Thanks for the help guys, I'm sure it was just decarb. Rookie mistake not using a protective coating.

I Started with a new blade (3/16" O1) and used a wash of satanite to prevent decarb.

First normalization @ 1600F, second at 1500F and then HT @ 1500F into pre-heated canola did the trick. Reapplied the satanite each time and it came out great.

I kept the edge very thick, and I have to say those Orange Blaze belts are unbelievable. I will be leaving all griding of 1/8" blades until after HT now, and I'll just set the bevels and leave plenty of meat on my 3/16 blades.

Less warpage, still easy to grind, and those belts last and last. Al's carbide file guide is incredible too - the belts can't touch it. Dulls my files off quick though :\

Cheers all, I appreciate the help.
 
just do not let your post heat treat grinding heat your blade beyond what is comfortable to hold in your ungloved hand, grind dip grind dip grind dip

-Page
 
Another thing that has occured to me about this problem is this.. ( and no, I'm not trying to teach my granny to suck eggs ;) ) Don't hang around with hot steel between oven and oil when quenching to harden.
1/8" stock won't hold it's heat for long at all, it'll cool like mad if you don't get it out of the oven and into the oil within about a second.. literally.

If you don't quench quick enough you'll be losing heat quickly (but not quick enough to harden the steel) and you'll not get full hardness from the quench.
 
Another thing that has occured to me about this problem is this.. ( and no, I'm not trying to teach my granny to suck eggs ;) ) Don't hang around with hot steel between oven and oil when quenching to harden.
1/8" stock won't hold it's heat for long at all, it'll cool like mad if you don't get it out of the oven and into the oil within about a second.. literally.

If you don't quench quick enough you'll be losing heat quickly (but not quick enough to harden the steel) and you'll not get full hardness from the quench.

I did wonder about this as well. I have my quench tank directly below the bench that the oven sits on - so I basically grab the blade, pull it out and then straight down into the quench.

Even so, time elapsed from first gripping the blade with the tongs to getting it in the quench would be more than 1 sec. I'd estimate maybe 1.5 - 2 secs. Could also be part of the problem as you say.

Hopefully the more I do it the faster I'll get.
 
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