Fixing warped 154cm

Robert_Phelps

Robert_Phelps

Joined
Nov 29, 2005
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475
I just heat treated 2 154 cm blades and they both warped, one more so than the other...They were brought to 1400 for 15, and held at 1900 for 30 minutes, plate quenched the first, then the second after it got back to 1900 for another few minutes... how should I fix the warps? I have them tempering now.. should I fix the bends at 400 degrees?

Thanks...

(These things better not frickin snap, it's my last steel and I have GOT to sell one:grumpy: )
 
I'm scratching my head as to how this even could have happened. I guess it's due to me not having a quenching press setup, I just put my weight on the plates while making sure they stay straight and parallel.
 
I have no answers, but plenty of questions. :o I'm also grinding some blades from 154 (actually I have CPM-154 but I think the HT info is the same). I was literally wondering about this very topic just an hour ago.

How thick is the stock at the spine? How thin did you grind the edges before HT? Should we attempt to correct warps while the blade is still fairly hot, before tempering? (that would be my guess.)

I hope mete chimes in on your thread; he's a big advocate of CPM-154 and has a lot of experience with it.
 
I straighten any warpage after heat treat/quench, but before it reaches room temp.
 
At a 400 temper, you'll likely have little luck straightening without snapping the blade. You can try, but no guarantees. It's a crap shoot, mostly. My suggestion would be to stress relieve at 1200 for around 45 minutes, straighten while hot, and then re-do the heat treat. You shouldn't have much warp the second go around after the stress relief.

The only plate quenched blade I've ever had warp was one blade and due to a specific cause. I'm also curious as to the stock thickness, etc. prior to heat treating.

The thing that caused my one warp was a poorly done foil wrap. Basically, I tried to skimp a bit, and in folding my final crease (double folded packets), I let the folded foil overlap the very tip of the knife. This resulted in a thin layer of foil on one side of the tip, and about 8 layers on the other. When the blade was still buttery from heat, the pressure from the plates bent the tip away from the thick foil. I've since made sure to never overlap folded foil with any part of the blade.

As for straightening during the heat treatment, the best thing I'd recommend is to plate the packet, leaving the very butt end of the knife and packet free of the plates. That way, when all the color is gone from the packet, you can take your snips, cut the end of the packet, and grab a hold of the end of the handle/tang. Once the blade is under the pearlite nose, quickly pull it from the packet and check for straightness, correct if necessary, and replate. If you catch it before Ms (martensite start...the beginning of the real hardening of the blade...not sure the exact temp for CPM154, but if you're around 500F you should be fine), you will be able to easily straighten out the blade with heavily gloved hands or a soft mallet and an anvil.

--nathan
 
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Alright, I'll do 1200 then re-ht. I think it might actually have been the foil wrapping, I used more than usual this time and probably folded it funny around the ends. Stock thickness was 1/8" at spine, and with distal and tang tapers.

I shouldn't have much decarb if the blades came out pretty clean, right?

Thanks for the help. I can't afford to take any chances here... and they have turned out so nice up till now, too.
 
:thumbup::thumbup:With a foil protected packet, decarb will be minimal. At most just the very surface that will be ground or sanded away in final finishing. The knife should look like a rainbow, an even and clean steely grey color, or a mixture of the two.

Good luck! I hope the packet was the issue as it's a really easy fix. Make your creases as neat and flat as possible. I use a piece of scrap micarta and a hammer to flatten 'em out real good so they allow max contact with the plates to the blade/foil. My grandpa told me long ago that a clean engine just seems to run better. I've found that to also be true with my shop, my work, and my foil wraps. :)

--nathan
 
Thanks for your insight, Nathan. Do you think it would be worthwhile to do a stress-relief cycle as you described, before HT, just to make sure the steel is "relaxed" and help prevent/reduce possible warpage? How thin do you grind your edges on 154 before HT?

I'm using stock that is nominally 1/8" thick, and grinding fairly typical hunting-type blades with a full-flat/slightly convex bevel. So they're relatively thin overall.
 
James, the stress relieving won't hurt, other than dirtying up your shiny blades. However, if you've kept the steel cool in grinding and haven't done anything crazy with it, you should be good to go as is. I've done some CPM154, a few 154CM, and a few 440C blades and never done a stress relieving unless I had to. These steels come well annealed from the foundry, and the grinding you do shouldn't add too much stress if you're careful.

I grind my edges down to between 1/32" and 1/64" prior to heat treating (probably leaning towards the 1/32 for most of them). However, I also use mostly 5/32" stock. 1/32" should be no problem even with 1/8" steel. If you're really worried about warping with 1/8" stock, I'd leave the edges just a smidge over 1/32, and then finish grinding carefully after heat treating.

--nathan
 
Glad to hear that, Nathan. The CPM-154, D2/CPM-D2 and 440C I've worked with so far seems to be properly annealed as you say; it's not all that much more difficult to grind than 1095 or O1 barstock. The difference is basically negligible to me. I grind bare-handed, dip in room-temp water often, and generally work on a couple blades at a time; this allows me to feel when the steel gets warm and let each piece cool down fully while I work on another one. I haven't noticed any work-hardening or anything like that. I've ground several blades from tempered files, and boy howdy, that's a whole different story.

A 1/32" edge is plenty thin for me to finish the edge after it's hardened and tempered.
 
So how should I go about straightening these? Obviously at 1200 this thing won't be glove-handleable.. are we talking about plate quenching it straight? One was warped at the tang (it leans to one side, now) and the other warped about an inch into the blade from the ricasso (4" handle 5" blade)
 
It's a trick at 1200 to be sure. I used some pliers and a small shop vice with smooth jaws. I clamped the blade in the vise gently just in front of the warp and tugged it straight. Careful where you grip the piers because it will cause marks. The easiest would be to use a flat surface and a soft wooden mallet (even a 2x4 section would work). An anvil would be best, but in a pinch I guess you could use a clean leveled concrete shop floor.

If you just can't get it straight while hot, it should be soft enough at room temperature to straighten without trouble (though with more force). If you straighten too much at room temp, it's a good idea to stress relieve once more prior to HT.

--nathan
 
One of these days I've got to make some de-warping jaws, and some micarta jaws for my vise. Alright, thanks a million for all the help :)

Edit...later, our intrepid knife maker returns from the kiln...

No sense in bumping this back up... but I clamped them in the plates from 1200, after 45 minutes, and they're as straight as can be.. re-doing the HT now with carefully folded and clamped tight foil,one less layer thick. I've re-applied the virgin blood to the kiln and I'm holding my mouth right, now. :]
 
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Damn thing (the original, worse warper) warped again. Even though rationally I knew it'd be very brittle, I guess I thought I'd teach it a lesson (:confused::foot: )and bend the tang right anyway? If it'd been any further down the tang I might could have re-ground it, but it'd be a 3-finger grip on a 5~" blade.

I do think I came across the problem. I might need to let the blades sit clamped for longer before I remove them. The one that warped/broke was probably still 300 degrees or so when I fought the foil off it.

I wanted to be shaping handles tomorrow, not picking up the hacksaw again>_<
 
Any steel should be heated to at least 400 F to straighten.If you've tempered above that you could straighten up to the tempering temperature.Normally plate quenching eliminates warping so if it does warp review all the HT variables.
 
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