Post HT blues

Phil705

Phil705

Basic Member
Joined
Aug 23, 2007
Messages
364
What the **** am I doing wrong?!! I recently finished the HT for four blades in 154CM, and I am still cleaning crud off the blades!

Here is what I did: Cleaned with acetone, washed with water. Dried. Dosed them with talc, added a piece of cedar, wrapped in heavy duty SS foil, pressed out the air as best I could, double crimped the edges with pliers. HT was 1950 degrees F, with 45 minute soak. Pretty sure my oven is accurate. Plate quenched with light pressure. I had no foil-welding, but the blades have a scale, almost a patina, that requires grinding to get off.

Is this normal? I have spent about 20-30 minutes per blade getting the crud off, really difficult near the plunge lines. Steel wool wouldn't touch it; hand sanding was a waste of time.

I would appreciate all ideas on preventing the build-up and/or getting the stuff off if it can't be prevented.

(I did put one post-HT blade in vinegar to see if that would help. Big mistake. The blade turned almost black, and I almost decided to leave it that way as it looked pretty good if you like the military tactical look. Had to grind it off with 500 grit.)

Phil705
Winthrop WA
 
I did a folder blade and spring out of some .103/.113 CPM154 and both were clean following HT. My profile was a fast ramp to 1425°F and a 10 minute soak to stress relieve the steel. Fast ramp to 1925°F and a 30 minute soak. I plate quenched between 2 pieces of 1" thick copper while blowing shop air between the plates. I measured 61.x Rc on both pieces following this profile. They were a bit discolored, but light sanding took care of that. I only put a small corner from a post-it note into the foil. I crimp the edges by rolling them with a piece of round stock and light taps with a hammer. I used a digital furnace here at work, so your results may vary depending on our set up.
 
Why use cedar instead of paper?

It's a very resinous pitchy wood.
Is the crud you are cleaning off coked on cedar pitch?
 
The discoloration is normal. Just soak the blades in muriatic acid for a short while and the steel will be flat gray. You are going to have to sand down the blades post HT anyway, but this shortens the cleanup a bit.
I would skip the cedar and just give the blade a spray of WD-40. That should accomplish the same thing. Others wrap a piece of paper around the blade. Some do nothing but seal the packet well. Al these procedures seem to work and get similar results.
 
+1 for Stacy's comments.

I just heat treated a batch of 12 pieces of A2 wrapped in foil without anything to consume oxygen - I just sprayed them with WD-40 to clean them up, then wipe it off.

Two had a bit of scaling where there were small holes in the wrapper, the others were quite clean.



p.s. I think it would be pretty easy to test whether cedar is best for you, paper, or nothing - just heat treat a couple of small pieces.
 
Keep striving for better Phil. It is possible to get blades out that are clean enough to be finished up on the buffer alone. It sounds like air is getting in your envelope - either by inadequately sealed envelope - or from rapid expansion of air and moisture blowing the envelope. Try less - or no - cedar. It does burn off what little oxygen is there, but if it can find air, cobustion of a hydrocarbon leaves CO2 and water - both of which expand a lot when heated.

Don't start your blades in a hot kiln. The expansion can be so violent as to blow the envelope - where a slower rise can allow expanding air to escape without much damage to the seal.

Don't peek. A little cooling when you open the door causes expansion / contraction and the envelope 'breathes' fresh air in.

You may get some oxides, but you shouldn't get scale.

Just for giggles, try doubling envelopes - a sealed envelope inside a sealed envelope. You may not be willing to take the extra cost and trouble regularly, but if you find it a lot easier to clean up..... :)

Good luck

Rob!
 
Thanks for the tips. Ok, no more wood in the envelope, better seal, WD40, and a muriatic acid bath. It's got to be better than what I'm doing now.
 
her eis a piece of D2 i did not long ago and i had to take it out of the foil pack as i was air quenching it and could not plate it
dsc02480sm.jpg


on my palate quench blades they for the most part are a milky grey with maybe a flash or 2 of color from extra air in the pouch

i add nothing and all i do is get them most the air out the pack and double fold the edges

here is a pile of blades untuched from HT they are all cpm154
dsc00502sm.jpg
 
I have been doing a lot of S30V and even some CPM-M4 in foil with plate quench. I don't spend much time cleaning them after finishing to usually 400 grit. Then wipe down with WD40, single foil envelopes with double folds. In Evenheat at about 2000F for 30-40 minutes. I stopped doing pre heat when I could find no advantage over just putting the packets in the kiln at 2000 after the kiln is at heat for 10-15 minutes. After quench, usually just have coat of soot that comes off with hand sanding at 400grit in a few minutes. I started using WD40 after I had a packet weld to the blade. That took a while to get off! There is so little air in the packets that I can't see how it could cause much in the way of oxidation. My S30V blades come out at better than 62 and the M4 was over 64 on my Ames tester.
Chip Kunkle
 
Here's one I pulled out this morning. It's been Hardened, Cryo and double tempered. Not our cleanest, but pretty typical.

ht.jpg


As you can see, we still use a scrap of paper - just seems to work better for us. This blade won't need much cleanup at all.

Rob!
 
Yep, that's what I'm shooting for, grey not black, and easy to clean up. I've actually had a few come out that way, but usually I get a lot of coloration.
 
Lose the cedar, lose the paper. Nothing in the packet but your blades.

Just saying, been doing this for years....
 
Forgot to add-You will always need to re-grind your blades to some degree. And, yes, the oxide layer on the surface (regardless of how the blades look when they come out of HT) will be different to grind than what's underneath.
 
RJ Martin said:
Lose the cedar, lose the paper. Nothing in the packet but your blades.

Just saying, been doing this for years....
Click to expand...

I also put nothing in the packet but the blade.They come out with a light gray oxidized layer.
Stan
 
If you send your blades out for heat treat do they usually wrap em in foil or do you need to go nuts cleaning em when they get back?
 
jaymeister99 said:
If you send your blades out for heat treat do they usually wrap em in foil or do you need to go nuts cleaning em when they get back?
Click to expand...

Really depends on who does them and what sort of furnace they use. Industrial heat treaters can "Bright harden" blades in a vacuum furnace and quench in the furnace using N2 gas, they will come back looking pretty much like they did before HT, just a different shade of silver. For this proces, you are looking at some sort of base rate, though, so, for just one blade up to maybe 20-30 lb of blades it's the same cost.

Not sure how you crimped your foil edges-I have had excellent results folding the edge over by hand, then running the back of a spoon over it to crimp it uniformly along the whole edge. Then, repeat the process.

Also, do you have a grinder available to re-grind the blades after HT? No matter how perfect your grinds are, during HT things almost always move and need to be re-ground, thinned out, whatever, to get the blade to it's final configuration.

Plus, most blades are only "rough" ground, to maybe 220 grit, before HT
 
RJ Martin said:
Really depends on who does them and what sort of furnace they use. Industrial heat treaters can "Bright harden" blades in a vacuum furnace and quench in the furnace using N2 gas, they will come back looking pretty much like they did before HT, just a different shade of silver. For this proces, you are looking at some sort of base rate, though, so, for just one blade up to maybe 20-30 lb of blades it's the same cost.

Not sure how you crimped your foil edges-I have had excellent results folding the edge over by hand, then running the back of a spoon over it to crimp it uniformly along the whole edge. Then, repeat the process.

Also, do you have a grinder available to re-grind the blades after HT? No matter how perfect your grinds are, during HT things almost always move and need to be re-ground, thinned out, whatever, to get the blade to it's final configuration.

Plus, most blades are only "rough" ground, to maybe 220 grit, before HT
Click to expand...

Ive taken em down to 220 grit. I'll probably be sending to Peters HT or Texas Knife Supply. Do they wrap em up?
 
I use nothing in the foil. They come out clean gray, with a touch of color here and there. I fold a seam and use a little roller, then I fold it again and roll it again.

I use 309 foil. I wonder if that makes any difference?
 
jaymeister99 said:
Ive taken em down to 220 grit. I'll probably be sending to Peters HT or Texas Knife Supply. Do they wrap em up?
Click to expand...

I use Peters now. They use an inert gas setup that will prevent oxidation. No need to wrap. They blades come back clean as a whistle... just slightly cloudy. I would highly recommend them.
 
You must log in or register to reply here.
Back
Top