heat treat problem/question

SDS

SDS

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Oct 22, 2007
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I have had this happen the last few times I have heat treated 154CM. After the heat treat the blade has what almost looks like stains in the steel. It's difficult to explain and I don't have any pictures to help out with the explanation.

Immediately after removing the blade from the foil wrap it has a mottled appearance instead of an even gray coloring all over the blade. I have had this on some other steels but a quick run over a sisal wheel and it usually dissapears. The past few times I have used 154CM however, it won't buff or sand out. I haven't tried going really deep with the sanding but it does not appear to be only on the surface.

I have had it happen with my own knives and I heat treated a blade for a friend today and it happened with his blade as well. I haven't spoken to him yet but I believe the steel he used for this blade is from the same batch that I have been using. Is it possible that I have a bad batch of steel??

Here is my process for heat treating 154CM:

1-I clean the blade and handle with acetone and allow it to dry.
2-I wrap the handle with a piece of paper to burn off oxygen in the foil envelope.
3-I seal the blade inside a foil packet double folding the edges (this last knife I even placed the first packet inside a second packet to ensure it was well sealed.
4-Place it in the oven (Evenheat) and bring up to 1950 for 30 minutes.
5-Remove from the oven and plate quench (between two one inch thick aluminum plates)

I'm wide open to critiques, criticizms, suggestions, ideas??????

I have not had this happen with D2 or with ATS34 or 154CM in the past. This leads me to believe that the problem may be with the particular batch of steel???

Thanks,
SDS
 
Two suggestions.

  • You don't need to wrap the blade in paper - a couple little squares will do.
  • Don't remove blades from the foil to quench. If they are plate quenched in the foil, the hot blade never sees oxygen - and the blade should come out almost shiny.
  • OK - a third thought - just in case. Don't put blades in a fully preheated oven. The violent expansion of air will amost certainly compromise the envelope.
Crucible does (did?) certs on every melt, so a bad batch is unlikely.

Rob!
 
Thanks for the reply.

On the paper, I use a piece that is about 1X3 inches, sometimes larger if it is a large blade. I only wrap the paper around the handle area, never the blade itself.

I take the blades directly to the quench plates without removing from the foil. Before I used the quench plates I did remove the foil then used moving air to quench the blades. Is it possible that the plate quench isn't quick enough? Do I need larger plates or maybe add moving air along with the plates??

I usually put the blades in a cold oven, raise the temp to 400, hold for 5-10 mins, then continue up to full temp.

I'm stumped on this and getting really irritated with myself for doing this to someone elses blade. I can handle a screw up on my own stuff, I can redo that.

Thanks again for taking the time to reply.
SDS
 
Do your blades look anything like these?

dpierson.jpg


If so, nothing to worry about. It does not change performance of the knife.

if you take off about .001 off the surface, the odd appearance will be gone.

it is usually unable to be buffed off completely and most of the time leaves

a ghostly appearance.

Also: forget the paper completely. the paper at some point in your life, will cause

the envelope to blow up. instead squirt WD-40 all over the blade while inside

the foil packet. let the excess drip off, do 2-3 good crimps....you won't have any

decarb (especially if you're plate quenching). I don't care for plate quenching as

it can also cause undesired results (in thinner stuff) and may not even always

come out perfectly flat !!!!

I believe the colors left on the steel (or gray as you call it) is caused by oil whether

uncleaned off or purposely sprayed on. Buffing compounds will also cause steel

to gray up.

If you use ACETONE and completely 100% degrease off a blade, plate quench it, the

blade should come out almost the same exact color as when you put it in, no color at all.

assuming you don't have oil inside the foil packet via the oils in your hand, etc etc.
 
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That's exactly what it looks like! And your right, after cleaning it up it's sort of a ghost like shadow. I haven't tried grinding it down farther, just hand sanding. I have had the colors you see there on other steels but they clean up. On the 154CM it just won't go away completely.

I went so far on this last couple of knives that I even cleaned the inside of the foil with acetone and handled everything wearing rubber gloves.

I haven't heard of using the WD-40 on the blade in place of paper. Does it perform the same function of burning off the oxygen?

Thanks for the information. I was starting to think that I had made such a stupid mistake than no one wanted to tell me how much of an idiot I was.

SDS
 
SDS said:
That's exactly what it looks like! And your right, after cleaning it up it's sort of a ghost like shadow. I haven't tried grinding it down farther, just hand sanding. I have had the colors you see there on other steels but they clean up. On the 154CM it just won't go away completely.

I went so far on this last couple of knives that I even cleaned the inside of the foil with acetone and handled everything wearing rubber gloves.

I haven't heard of using the WD-40 on the blade in place of paper. Does it perform the same function of burning off the oxygen?

Thanks for the information. I was starting to think that I had made such a stupid mistake than no one wanted to tell me how much of an idiot I was.

SDS
Click to expand...

I too was having the same weird issue A LOT and then I asked Stacy Apelt (bladsmth) and he was the one that told me to use WD-40 instead of the paper. To ensure I get the colors and grays, i tend to open the envelope a little earlier while the blade is almost still slightly showing color. as the envelope is opened and the oxygen goes in, it starts to show gray.

the funny part is, the more white you get (color of the steel i mean) means the better you cleaned and sealed that foil packet. when you get it to completely the same color as it went it is when all oils are gone and the envelope packet completely sealed !

hand sanding the blade you again would have to go rather deep say .001 which i guess aint much, but can feel like an eternity via hand sanding ! the grinder will make the marks/stains/spots go away instantly.

I think that the oxygen in the foil packet is going to disapear and get burned off whether you have paper in their or not. I have never had decarb on a blade even after not using the paper method
 
I've never tried it without the paper but I'm willing to give it a shot. I'm still not sure why this only happens with the 154CM and not the other steels that I use.

Thanks again for taking the time to offer advice.
SDS
 
I haven't used A2 before. I have primarily heat treated 154CM, ATS-34, 440C, and D2.

Since the blade in question was not mine I didn't do much to it to try to figure this out. I met with the maker today and we took some 220 grit paper with a block behind it to the blade. The ghosting/shadowing vanished. I guess I just panicked a bit early on this one.

Thanks for the input on this one guys. I kind of feel foolish for bringing this up but I was in a bit of a panick since it wasn't my blade.

SDS
 
As you have already discovered, it is a surface discoloration. It can come from many sources,even the pressure of the plates, but regardless of the reason, it sands off. All blades should be re-sanded after HT ,IMHO. If you want an experiment, next time you have a blade with this discoloration, dip it in muriatic acid for a short etch. See if the color goes away. Let us know what the results were. I'm guessing the blade will turn an even gray color.

Spray the blade in the packet with WD-40, and let the excess drip out. Some makers do this twice. Let sit for a few minutes so the volatile carrier compounds can evaporate. Seal the packet up and bake as usual. I believe many canister weld damascus makers use WD-40, too.

WD-40 is a petroleum based hydrocarbon compound, so it will combine with any oxygen in the packet as it heats up. Since it coats everything evenly ( it is basically a thick sticky oil that has a solvent and propellant added), the surface will have a much better chance of being evenly colored.

BTW, the name comes from the original product development. He was trying to make a water displacing protectant for coating the outer surface of Atlas Missiles to protect them from corrosion. He came up with a suitable compound on the 40th attempt...thus WD (water displacement) -40 (40th attempt).
Its popularity outside missile defense was an unintended by-product. He never expected universal use as a household product. If you have a very old can of WD-40, the label will say, " Produced by the Rocket Chemical Company, San Diego, California"

Stacy
 
I forgot the paper one time and it didn't make any difference. I don't bother using paper anymore. Main thing is get a good seal on the pouch.

How does plate quenching in the pouch work for a knife that is not flat? A Loveless style knife with a tapered tang for example? I'm always afraid I'll bend or warp those blades or not get a good quench so I quickly pull them out of the pouch and depending on the blade I'll put it between plates or set them in front of a fan to cool.
 
Thanks Stacy. I'll give the WD-40 a try the next time I heat treat. I probably wouldn't have panicked so bad if it were my own blades. I can regrind my own stuff. I'll try to remember to grab some muriatic acid the next time I'm in town.

Cfendley, I figured the plate quench would be more even than fans. I figured the fan would have to diffused pretty well to avoid having it blow on just one side or point. That said, I never had any problems when I was using fans instead of plates.

Thanks again to everyone.
SDS
 
I'm sorry if I'm hijacking the thread here.
SDS. So if you plate quench a hollow grind you just get the plates on the high spots of the blade and it pulls the heat out fast enough? On a hollow grind with tapered tang the plates wont actually touch much of the blade. I assume you put the plates against the recasso and spine. The plate quench in the pouch seems like the way to go but I've always wanted to make sure I get a good quench on the cutting edge and afraid the pouch would hold the heat since the plates wont actually be against the cutting edge.

Thanks for the info
 
There are a lot of guys on here a LOT smarter than I am about these things but my experience has been that the plate quench works well. I had to find aluminum plate with enough mass to draw the heat out quickly but once I did that the temperature of the blade seems to drop at least as quickly as an air quench and probably faster.

I do understand your concern about the edge not being in contact with the quench plate but that has not caused me any problems personally. I have tried both the air quench with fans and the plate quench and to me the plate quench seems more controlled. With the fans it seemed like whichever side the air was blowing on cooled faster than the oppposite side.

To be honest it may be a matter of splitting hairs. I don't think your hijacking this thread but you might want to start a separate thread asking about the details of plate quenching. You would be more likely to get a specific response. I have found nothing but great folks here who are willing to bend over backwards to offer advice.

SDS
 
A little explanation of how plate quenching works may help.

When the austenitized blade ( still in the foil packet) is placed between the heavy aluminum plates, the heat from the blade conducts to the foil, and then into the plates. It only requires minimal contact, or even close proximity for this conduction to occur. As for the speed being fast enough, the martensitic stainless steels we use have a very long cooling window, usually over five minutes, to get below 900F. With carbon steels you deal in seconds, with stainless steels you deal in minutes. The thin cross sections of a knife blade, and the even thinner edge will assure a fast enough quench. If you are really concerned, having air blow down the gap between the plates would speed things up, but as has already been said, speed of quench is not needed.....eveness of quench is what you want.

So, to sum it up......You don't need to rush the packet into the plates, or worry about cooling fast enough.Taking your time to see that the packet is properly clamped between the plates will be the best way to eliminate warpage. Removing the blade after a few minutes, and immediately straightening any slight warps or twists before it cools farther is usually no problem.

Stacy
 
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