Snail trails on HT blade???

K

KnifeMaker.ca

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Let me start by saying this is not a blade we heat treated - but it is from a customer who uses essentially the same process we do. Lets start with a picture - post hardening - pre cryo.

cecil.jpg


Note the "snail trails". I have never seen this before BUT - this happens to him on different steel types such as 154 CM, ATS34, and in this picture on S30V. It is persistent in that if he finishes to 600 or 800 grit, it still shows in the right light.

He cleans his blade pre-HT - originally in acetone and more recently in soap and water - with no difference.

He uses a small scrap of brown paper (see near the butt of the handle mark)

He double wraps in the same 309 SS foil we use

He hardens at 1950F - 40 minutes - in the evenheat - plate quenches in the envelope to cool - and they come out like this. He follows with cryo in dry ice slurry and double temper to specs.

We are at the show in Kamloops BC and there are at least a couple other makers - respected makers - who say they get this all the time and just grind through it. We do well over 1000 blades a year and I have never seen this. here is the kicker - unique to this blade pictured. You can see some thumb ramp filework (gentle half rounds) and in the snail trail V in front of them, this blade has actually cracked. The crack seems to start about 3/32 in front of the last groove in the spine.

As I type this questions are coming to mind.

  • What is he using for quench plates? Could the surface be uneven?
  • How much pressure or weight is he using on the plates. (but there is clearly NO pressure on the bevels so...?)
I'm going to ask him to send us a couple blades to HT, but I hoped someone might recognize the problem and shorten our learning curve on this.

Thanks much

Rob!
 
I get the same effect on many of my stainless blades (when using foil). I have, in my mind, attributed it to oxidation colors/patterns due to inconsistent contact of the foil packet to the blade. I have never had a plate quench blade crack, though. As to the pattern, I also just grind it off, but I've tried to sand through it in the past and had the same thing as your customer...it showed up in certain lights.

--nathan
 
I personally like the looks, but I'm not a knifemaker, and not much of a collector, so take it for what it's worth.
 
its jsut a bit of left over air in the pack following the slight differences in the foil pack

if you want to you can kind of have fun with the foil and try and get a interesting look
(will look for the pic i have of a as HTed blade finished )
 
I agree with the other posts, it's the crinkling of the foil. I don't think it's the cause of the crack.
 
Is there any sign of the crack where the spine meets the plunge grind area. It would be best not to carry the grind all the way to the spine if your going to do any kind of filework.It creates an area of weakness.
 
I just got my CPM D2 blade back from heat treat that had the same type patterns. After 2 or 3 hrs of hand sanding, you could still see them if you turned the blade just right. Started over with 220 grit up to 600 and then the buffer with 600 white Ch. Patterns are gone.
Thanks for asking the question... I was wondering too
 
its really jsut kind of liek decarb but in the stages before it gets deep or eats the carbon
maybe calling it prescale might be better

it startes as light gray and then gets a bit darker then through the rambow of color (like an oil on water slick) then black folowed by what we all do not want to see mat black pitted hate of true decarb
 
Thanks all

I agree that the crack is a different issue - and no, it's nowhere near the plunge. It's about 3/32 in front of the filework, right in that little snail trail V. The filework is much too gentle and simple to have caused it. WEIRD.

I accept that this doesn't affect the quality of the knife, but it sure does affect the amount of work to clean up after HT. One of the reasons this customer bought a kiln was to get the easy clean up results we are getting. Now I have to figure out what the difference is. :confused:

Has anyone managed to resolve this issue in theit HT, and if so, how?

Rob!
 
so after you get the snail trails and if you have used a steel thatg can handle the 2ndary temper curve 1000f
you can bag it and put a chunk of wood in the foil pack with lots of air room
then you can get some tempering colors on the way up till the wood burns and eats up the last of the O in the pack stopping the colors

you can get something liek this then
 

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butcher_block said:
so after you get the snail trails and if you have used a steel thatg can handle the 2ndary temper curve 1000f
you can bag it and put a chunk of wood in the foil pack with lots of air room
then you can get some tempering colors on the way up till the wood burns and eats up the last of the O in the pack stopping the colors

you can get something liek this then
Click to expand...

that is an interesting way of dealing with what someone else would call a problem, looks good to boot:thumbup:
 
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