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  #1  
Old 02-16-2017, 07:50 PM
irishknifeworks irishknifeworks is offline
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New Oven/Severe Warpage Emergency

Help!

I've been heat treating 01 blades in my gas forge for several years. Never had much of a problem with warpage.

But I just bought an Evenheat Kiln. My first 4 knives have warped severely when I heat treat.

So here's what I'm doing. Full speed ramp up to 1475, soak for 20 minutes. Blade warps badly in the oven every time.

I can't understand why I never had this problem in my forge. The only difference I see is that the forge brings the blade up to non-magnetic way faster than the oven brings the blade up to 1475.

So I did some research and thought I'd discovered the problem. Many knife makers say they run a stress relief cycle before heat treat. They soak the knife at 1200-1300 for 30 minutes and then either air cool or ramp on up to their hardening cycle.

So I decided to give it a try. I Slowly heated a blade to 1250 and soaked it for 20 minutes. Guess what? WARPAGE BIG TIME!!!!!!

I'm soooo frustrated. What am I doing wrong? Somebody has to know what's going on here.
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  #2  
Old 02-16-2017, 08:16 PM
jimmontg jimmontg is offline
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The following are HT instructions from the manufacturer.

On large parts, pack-hardening and pre-heating at approximately
1200F,with a thorough soaking before raising to the quenching temperature of 1475 to 1500F,
are recommended. Hold at the quenching temperature for one half hour per inch of greatest
cross-section. Follow by quenching in oil to 150F and temper immediately.
A series of oil-quenched samples were tested. Here are the resulting hardness and fracture
ratings from different quenching temperatures:"
Quenching Fracture Rockwell
temperature -
F grain size C
1400 9 60
1425 9 62
1450 9-1/2 63
1475 9-1/2 65
1500 9-1/2 65
1525 9-1/4 65
1550 9-1/4 65
http://cintool.com/catalog/Oil_Hardening/O1.pdf

You forgot that you must bring the parts up to 1200 degrees and let them equalize for 10 mins or so slowly. 30 mins is too long. Also did you leave 15-20% of the blade left to grind off after HT? You need to leave .030 to .060 on the edge before HT. with .060 best. You cannot HT too much of a finished blade or it will warp. 1475 is the sweet spot for O1. It is my favorite steel. Temper immediately after HT at 450 for 2 hours and then check and straighten unless you are going to do a cryo treatment, story for another day. The factory instructions are for thicker sections, but the 1/2 hour per inch rule stands except for 1/8 to 3/16 you want to let them soak for 10 mins at 1475, 15 won't hurt either.
I presume you have your quench oil at 130 degrees for quench and Parks 50 is actually a little thin for O1, but shouldn't cause bad warping unless you are moving the blade side to side instead of up and down.

How thick is the material you are HTing?

Last edited by jimmontg; 02-16-2017 at 08:42 PM.
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  #3  
Old 02-16-2017, 08:44 PM
jimmontg jimmontg is offline
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I do not see that much wrong with what you are doing unless your oven is off. A 30 min soak is too long and bring it up slower with steps if your oven heats up too fast. Go to 150 degrees on your quench oil.

Last edited by jimmontg; 02-16-2017 at 08:50 PM.
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Old 02-16-2017, 09:06 PM
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Ray Rogers Ray Rogers is offline
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I made a lot of O1 blades and my formula is pretty much as Jim stated. Blade goes into a cold oven, temp ramps to 1200F as fast as it can, hold 5 minutes, then up to 1475, hold 10 minutes, quench in 150 degree Tough Quench.

One thing I do differently is that I don't do any grinding on the blade until the heat treat is complete - just a blade profile goes into the oven. I don't think I ever had an O1 blade warp, certainly not enough to lose the blade...


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Old 02-16-2017, 09:43 PM
jimmontg jimmontg is offline
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Fast? Ray I was always taught to bring to equalize temp not slow, but steady and not too fast. Then ramp up to 1475 and hold, but not too long, 5 minutes min and no more than 15 minutes for knife thickness. We used 80 viscosity oil for O1 which is the spec for it, so Parks 50 should be hotter, but Irish is talking about a lot of warp so I'm not sure. Then again my last name is Montgomery so maybe his Irish is making me think crazy.LOL

Jokes aside I never had a warp problem with O1 unless I ground it too thin.

Last edited by jimmontg; 02-16-2017 at 09:48 PM.
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Old 02-16-2017, 09:55 PM
jimmontg jimmontg is offline
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Irishknifeworks? What form of O1 did you use? Precision ground, mill finish bar or sheared sheet?
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Old 02-17-2017, 07:00 AM
irishknifeworks irishknifeworks is offline
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I'm using 01 Precision Ground, 5/32 thick. I've basically done everything you guys have mentioned except I do all my grinding prior to HT. I believe I'm leaving enough material to prevent warping.

The thing is, why has this never happened when I HT in my forge by simply bringing the blade up to non-magnetic then quenching?

I'm starting to wonder if I have a bad batch of steel. Could that be possible?
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Old 02-17-2017, 07:27 AM
gkyle840 gkyle840 is offline
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Could you try heat treating one from this batch of 01 in your forge to see if it warps in there as well? That should help you to determine if it is the particular batch of steel.
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Old 02-17-2017, 08:52 AM
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Jim,

I said 'fast as it can' but that really isn't all that fast, probably takes about 30 minutes.

Irish,

Bad steel is possible but I can't say that's the problem. There are lots of different manufacturers for O1 and the steel they make is not all the same though. How is the blade set in the oven? Flat on the floor would be a problem but I doubt you're doing that. Trying to do more than one blade at a time will make a blade sit too close to a heating coil on one side, that could be an issue...


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Old 02-17-2017, 11:10 AM
irishknifeworks irishknifeworks is offline
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I have one more piece from this batch of steel. I'm going to HT it in my forge and see if it warps there. Good idea Steel addict. I was already thinking along those lines.

Ray, I'm doing one blade at a time, center of oven, on edge. I've done 3 identical blades from the same batch of precision ground 01. Warpage all 3 times.
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  #11  
Old 02-17-2017, 11:17 AM
samuraistuart samuraistuart is offline
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My 2 cents....I've never had O1 warp on me....ever.
I've been told by metallurgists and guys that know infinitely more than I that with low alloy steels (higher alloy stainless is a different story...because of the high amount of alloying).....that the only time a steel like O1 "needs" a 1200F pre hardening soak is if it's a complicated cross section...which our knives are not. I've used the 1200F stress relief on other steels that did warp, with success sometimes, others not.
Kiln should be AT the hardening temp before placing the knife inside. 1475F ideal for O1 and most all hypereutectoid steels. Once kiln is at 1475F (and I wait maybe 15 minutes to be sure there is not temp overshoot and that the atmosphere inside the kiln, and not just the thermocouple reading, is 1475F), insert the knife, allow the readout to rebound to 1475 and begin a 15 minute soak. The blade will not be AT 1475 once the readout rebounds....but it is within 2 minutes.
The blade warping.....when is this actually happening? After the quench? If so, it may be bad quench technique, although you stated this does not happen with your forge. Most O1 comes precision flat ground, and is one of the most stable carbon oil quenching steels out there.
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Old 02-17-2017, 11:59 AM
irishknifeworks irishknifeworks is offline
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The warp is occurring inside the oven. It happens sometime prior to quench. I even did a 1200 degree pre hardening soak and one blade warped during that pre-soak phase. The more I think this through the more I think I've gotten hold a some bad 01.
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Old 02-17-2017, 01:52 PM
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Any chance the oven is heating unevenly? For instance, if the oven is the type that has a separate coil on each side but maybe one side is heating much more slowly than the other due to some type of electronic failure. It would be difficult to notice that happening after the oven is past 1200 and both coils have color in them.

Just a thought ...


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Old 02-17-2017, 06:01 PM
irishknifeworks irishknifeworks is offline
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Well, I think I'm on to something. I heat treated 3 old blades that never made it to heat treat because they had mistakes. Same exact HT formula. All 3 came out straight as an arrow. I have this last piece of steel from the batch I'm suspecting is bad steel. As soon as I finish the grinding I'm going to HT in my forge as I've been doing for years. If it warps in the forge I think I can pretty much conclude I have bad steel. I'll let you know how it turns out.


The crazy thing about this whole mess is that it occurred at the same time I'm trying out my new oven. Ray, I honestly don't know if there is any way of ever telling if the oven is heating evenly on both sides. The coils on each side seem to be functioning the same. Besides, if that were happening I would think the old blades I treated would have warped too!

I'll figure it out eventually. I really appreciate you guys and your willingness to try and help. I've fooled around with this for several years but in many ways I still feel like a newby. I need to utilize this forum a lot more.
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Old 02-17-2017, 06:34 PM
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Ray Rogers Ray Rogers is offline
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The main thing I was getting at was if the oven has TWO coils one might be having a problem and that problem might have only come about recently. If your oven has only one coil (like mine) then I doubt that uneven heating would even be a possibility ....


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