CPM154 Mystery Problem

southriv

southriv

Joined
Feb 28, 2002
Messages
751
I've had this problem with 154CM before. The attached drawing shows the surface of a small (1/4" wide) flat area above the grind after going to mirror polish. I can just see this with the light the right way. The drawing is my attempt to describe what I see under an Optivisor

At first I though it was a haze given by the grease from the buffing compound. I tried every thing to make this go away: I went back through the sanding steps 3 times, once starting from 220, once from 600 grit and once using EDM stones – nothing works.

This is not the first time this has happened – and it is always with 154CM. The steel is from Crucible/ Paul Bos HT. What I have been doing is turning the knife into a satin finish piece. That's okay, but I did have different finish/Handle material plans.

Any ideas before I send this off to Crucible?? I'm off for the day on my motorcycle –I'll check back later

Bob
 
Several people have theories this is a minor seperation of the various elements showing up as a mottled look. I tend to agree. It is found more often in cold rolled than hot rolled steel. Admiral Steel has been blasted for it in dozens of postings. I believe Admiral got hung with the most complaints since they seem to have the biggest market share. The knife houses tend to sell hot rolled only ATS-34. The problem does seem to to vary from batch to batch.

I've had several ATS-34 pieces with this and at least a few 154CM pieces also. I now use 154CM since it happens much less often with it. I've never been able to get out the mottling as it usually runs completely through steel in splotchy sections. Buffing just seems to aggrivate it more. I did find using a cork belt with green chrome buff compound (pressing hard) helped minimize some of it. If that still doesn't clean it up, I take it back to a satin finish with 600 grit hand sanding. In theory, 154CM shouldn't have it like ATS-34 due to the different smelting process but it's still there, just less often.

I ruled out heat treating (I use Paul Bos also) when I took an annealed piece with a known problem and polished it before heat treating. The mottling was there prior to heat treating.
 
I've had that with 440V before. The only cure, if you could call it that was to only finish to 400 grit. I kept the blade and used it myself. I wouldn't let that one of my shop.

C Wilkins
 
Tracy & C L - thanks for chiming in - it looks like we have had exactly the same experiences and tried the same cures with just about identical results. I almost decided to go with ATS-34, but now I understand better about this occurance.

I've finished two other knives from the same bar and didn't have this problem. I have one more - hopefully I'll get lucky.


Bob
 
I had the smae problem with D2,I really started seeing it when I started to hand rub it.You do all that work and it shows up
just about makes you sick:mad:
 
I've had very little of this problem with 154CM
other then a short time ago
I had one bar give me fits I almost think it was marked wrong
and may have been D2? other than that I've had hazy spots that just
had to be taken down a little more to get past it, what I call,
the dead layer.

edited to add
I once left a 154cm blade in the oven for 2 hours in foil
( yes a goof up) it had a very open grain in no way
you could Mirror polish it and make it look even close to right.

no more than 15 min at Harding temp. or you'll have problems I will say
and I wonder if when cooling if for some reason it doesn't get
cooled evenly , say it's leaning up against something you'll
end up with a problem spot? just guessing on this one..
 
I've had the same problem with both ATS-34 and 154CM recently. Never had it before. It seems to be worse with bar that has been sheared from sheet as opposed to true hot rolled bar stock. I sent samples back both times and Admiral even sent one piece to the Japanese mill that the ATS originated from. They all said there was nothing wrong with it?? The US metalurgist that examined them also theorized the problem was exacerbated by sheet production as opposed to bar. Something about uneven cooling rate in the manufacture of larger sheet product, etc.

It is disgusting to get that far in finishing a blade and then have those squiggly marks show up. In some of mine, I couldn't even hide them with a 400 grit satin finish. I may try beadblasting them one day to see if that hides it.

If you like ATS-34, may want to try RWL-34. Guarenteed not to have the problem. No grain effect whatsoever. Kind of costly though, especially in the thicker sizes.
 
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