Warpage question..

swede2207

swede2207

Joined
Mar 10, 2002
Messages
323
Hey fellas..i have been hit by a new phenomena for me. I had a couple knives ground from 01..down to about .025 at the edge. Put them in my evenheat ran it up to 600 coated the edge area with pbc powder and then up to 1475 for 15 minutes quenched in the oil from Darren Ellis suggested for 01. Tempered twice for 2 hours at 475 upon further investigation we have warpage! that sucks i had already spent the time hand sanding down to 80 grit, thought it might make life easier later on..Im at a loss here this hasnt happened before..can i count on a certain number of my blades warping and just junk them..when i tried to straighten one it broke of course..had nice grain structure..but broken nonetheless..anyone who heat treats lots of big knives id appreciate your thoughts. One was a 10 inch chopper from 1/4 inch the other a medium size 6 in blade from 3/16. Thanks Luke
 
I dont do big fixed blades and am mainly a folder guy. I do my grinding after the heat treat for that reason, so it dosnt warp. Mine is all stainless and is rapid air quenched in between two 1" thick aluminum plates. Goes from 1950 to picking it up in the hand in about 1 minute. Minor/minimal warpage this way. I know making sure its extremely even on both sides helps too.
 
Luke,

Did you edge quench these blades? Full quench?

The 01 should be pretty tough after the heat treat. I am surprised that it broke when you tried to straighten it.
I make mostly big knives the only times I have had them warp is when they were ground to thin.
Sounds like you have the heat rite. Fred
 
Fred..the blades were full quenched..i had planned to draw the spines afterwards..The 3/16 ths one is a pretty wide blade(1.5 inch) but it didnt seem too thin..the 1/4 inch chopper slightly warped. I have an arbor press rigged up for straightening knives..guess it puts on lots of stress it was tough to break trust me..but we knuckle draggers can find a way. Also both knives were ground evenly..I couldnt tell any difference between them.Guess ill try again tomorrow..
 
Normalizing after grinding would help. If I have a warp, I straighten right out of the quench, you have a few minutes to do so. If that doesn't work, I normalize, straighten and re-HT. It's just about impossible to straighted after the blade is tempered.
 
My suggestions for the future would be to stress relieve the blade prior to austenitization. The thermal cycling not only refines the grain, but relieves the stresses. Upon quench, examine the blade while still hot (below 900 but above 400). If there is a warp, you can straighten it then any way you like. Hammer it on the anvil, twist it in a vise, etc. Prior to the Mf you are straightening soft austenite. After the transformation, you are trying to straighten brittle martensite. Once the Mf point is reached, it will break, so the work needs to be done quickly and in one step. Once the blade is cooled and then tempered, it is harder to get warpage out. If you notice it after temper, re-heat the blade to the temper target (475 in your case) and straighten at that point. If it is a bad warp, re-do the HT with several cycles prior to quench.
Stacy
 
Swede, I work with 01 almost exclusively. If you don't get the warp out immediately after quench, then go ahead with your temper cycles. After the blade is tempered, locate the area of warp. Polish/sand the blade so you can see heat color. Apply heat with a torch around the warped area up at the spine until you reach a dark straw, but don't allow the heat to go to the edge. At this point, overflex the blade and pour water on the heated area. This will lock it in straight, or close to. You may have to repeat, but it will work without having to do another HT. I just did a Bowie, 2 1/4 wide, that took a slight warp. It just took more strength to do the overflex, but came out quite straight after three tries at it. One try seems to do it with the simple steels, but you have to fight with 01 a bit, but it will come around.
 
I swear that most all steel needs to be stress relieved right out of the package. I think your edge was too thin also.
 
Thanks for all the help guys..How hot is hot enough for thermal cycling(stress relieving) is it 1200..for some reason that temp sticks out..ill try to fix the one i got left..but just starting over may be my best bet at this point..I knew that knife was going to give me problems i could hear it pinging in the quench..it was a terrible sound. Im used to the pbc cracking but this was a loud pinging..Ok so i wont sell my knifemaking equipment and ill get back to work..Isnt this fun? Thanks again Luke..

Also how thin should i grind the edges of my choppers and such before heat treating?Later Luke
 
IMHO, .050 -.060 for long, thick blades, a bit thinner for smaller blades, in an oil quench.

I don't use them but, if you were heat treating with salts, you could go much thinner.
 
LRB said:
Swede, I work with 01 almost exclusively. If you don't get the warp out immediately after quench, then go ahead with your temper cycles. After the blade is tempered, locate the area of warp. Polish/sand the blade so you can see heat color. Apply heat with a torch around the warped area up at the spine until you reach a dark straw, but don't allow the heat to go to the edge. At this point, overflex the blade and pour water on the heated area. This will lock it in straight, or close to. You may have to repeat, but it will work without having to do another HT. I just did a Bowie, 2 1/4 wide, that took a slight warp. It just took more strength to do the overflex, but came out quite straight after three tries at it. One try seems to do it with the simple steels, but you have to fight with 01 a bit, but it will come around.
Click to expand...

This method would scare me to death IMHO. The blade is already heat treated to it's optimal state. Heating the blade up in an uncontrolled manner (color only) after tempering and then bending it and shocking it with water might get it straight, but I'd be more worried about the stress it might put into the steel.

It's much safer to do it right out of the quench. If you get it straight...great! If you can't get it straight right out of the quench, heat it up and straighten it, then normalize and harden it again. This would be my suggestion.

Ickie
 
That method is straight from Bill Moran. I've never had a problem with it. One could put it in the oven at the temper heat and do the same thing if you can move fast enough. I don't believe that the water is a great shock, the area is at temper heat, not much beyond.
 
Ok so now ive tried two more and both have warped and subsequently broken two(noticed right out of the quench one straightened a little then snapped) so i have cut out new blanks and profiled them..I wonder if me filing in the plunge cuts with a square edge file had anything to do with this thats all i did different..i am at a loss here and very lost..later Luke
 
I'm going to say something is wrong in the quench. What temp is the quench oil? Is there any possibility that you got the wrong quench?
You mention sanding to 80 grit. Crosswise, or longitudinal? I finish mine to 100 grit, crosswise, some to 220 grit. I shouldn't say this, but I have never had a blade break, or crack, unless on purpose. I take my edges to about
.015 before heatreat. Never a related problem. I have done quite a few with the 90o filed plunge also. Never a problem. Check this photo. The file worked Spanish notch is about .010. Not a problem. I have no idea!
wicksknives013.jpg
 
Wow Wick another beautiful knife as usual..As far as i know this is the quench that is recommended for 01 from ellis custom knifeworks..i heated it to 130 degrees before quenching..i just dont know what to do at this point..
 
I don't use a hammer to straighten blades after quenching. I pull the blade from the oil, wipe it off (it's still smoking) with a rag and sight down the blade. Usually they're straight but if it's warped. I put it over my knee and with gloved hands, pull (flex) it straight. At this point, they usually bend pretty easy, so don't over do it, bending it back can be bad. You only have a short time to do this. I will re-heat treat, before I break the blade. Just takes practice.

Try normalizing before HT.
 
Thermal cycling is a repeated normalization.
Heat the steel until completely austentitized ( For O-1 use 1600F and a 10 minute soak ), and allow to air cool to 900. Repeat three times. The grain is made even sized and refined, the stresses are relieved, and a good pearlite structure is formed. Now when you do the final austenitization and quench you should have much less chance of warpage.

Stacy
 
I'm no expert in 01, but quenching any blade in anything, if you don't keep it practically and perfectly straight when you quench it, it's gonna warp on you. If you put it to one side of your kiln and more heat gets to one side and you quench it, it's gonna warp. Try doing an edge quench on the blade instead of quenching the entire blade as i'm sure your results would be much better. It's only the cutting edge that needs to be hard and tough anyways and if you like etching, it will definitely make some sort of hamon. I also have an evenheat knife oven and I mainly use A2 steel but have done 01 a few times. Definately check the blade for straightness as fast as you can before you quench it right out of the kiln. Your problem could just flat out be it's warping in the kiln. I doubt it would warp while it's being tempered unless by some odd ball angle you're leaving the blade in. I don't know how you're setting it in in the kiln, maybe with knife blade holders, but definately if you're using something like that possibly made of ceramic or something to definately stick some pieces of cracked off firebrick to make sure the blade doesn't move when it's being heat treated. If you just put it knife holders and it's just possibly is able to tilt over during treatment just an itty bitty bit, you're gonna have the warp already before you've even quenched it. can't tell you how many blades i made and heat treated of A2 that came out already warped out of the kiln because I didn't have some nice proper fit/brick holding the blade perfectly on the spine. Evenheat kilns in my opinion seem to work pretty well.
 
Leu Custom said:
I'm no expert in 01, but quenching any blade in anything, if you don't keep it practically and perfectly straight when you quench it, it's gonna warp on you. If you put it to one side of your kiln and more heat gets to one side and you quench it, it's gonna warp. Try doing an edge quench on the blade instead of quenching the entire blade as i'm sure your results would be much better. It's only the cutting edge that needs to be hard and tough anyways and if you like etching, it will definitely make some sort of hamon. I also have an evenheat knife oven and I mainly use A2 steel but have done 01 a few times. Definately check the blade for straightness as fast as you can before you quench it right out of the kiln. Your problem could just flat out be it's warping in the kiln. I doubt it would warp while it's being tempered unless by some odd ball angle you're leaving the blade in. I don't know how you're setting it in in the kiln, maybe with knife blade holders, but definately if you're using something like that possibly made of ceramic or something to definately stick some pieces of cracked off firebrick to make sure the blade doesn't move when it's being heat treated. If you just put it knife holders and it's just possibly is able to tilt over during treatment just an itty bitty bit, you're gonna have the warp already before you've even quenched it. can't tell you how many blades i made and heat treated of A2 that came out already warped out of the kiln because I didn't have some nice proper fit/brick holding the blade perfectly on the spine. Evenheat kilns in my opinion seem to work pretty well.
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the oven im sure is right on..it hardens perfectly just the warpage is the bummer..edge quenching was one thing i did think of..i thought i might get some of that clay coating and coat these blades then quench..is it likely that that will lessen the chance of warpage. As far as holding them directly on spine..that may have been an issue..im going to get a new blade holder for my oven..I want to thank everyone who was nice enough to offer advice and suggestions..it is greatly appreciated..later Luke
 
One of the first things I do when starting a new knife project is to surface grind the steel out to remove the gray coding on the steel and this also straightens the steel if there is any warping in the steel. perfectly flat is what you want. I then layout my pattern on the steel and and grind it out. I then drill all holes and cleanup. Stamp my name in the steel using my stamping press. Heat treat my steel utilizing my evenheat oven. Then quench in oil and hold there. When I am ready to temper my steel I placed back into the oven and do so. When this is done and am ready to surface grind the black scale off. In doing so I know it will come out with no warping at all. It will be perfectly flat ready to grind on my 2X72. I like doing it that way and believe me it will reduce the possibility of getting warped knives. ------------:thumbup:
 
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