Metals:The truth comes out. Discussion Invited.

Three Sisters Forge

Three Sisters Forge

Forum Owner-Moderator
Good Morning,

This information comes out of a shop visit. A guy stopped by to order a folder. He felt it was important to share this info.

Metals: I specialized in Implants and reconstruction, faculty at two dental / medical schools (Dr. Jim). Did research on implant materials back in the early 80s. We looked at 440C, ATS-34, CMP metals, 60SV, 30SV, VG-10, and Ti. These were used for implants, blades and drills. Their use in knives is interesting, because these have been used in surgery for years. We found that once these metals went through a "Manufacturing Process" there was little performance difference. Most of the claims were based on one off, very critical handling. Once they made them in big batches, all hell broke loose. The biggest problem is with "sintering" on the surface. Sintering happens when different metals are ground or polished on the same grinders, belts etc. Even batch heat treating will do this.

I took 6 blades from BIG name makers and did EDEX surface scans. ALL were contaminated and sintered on the surfaces. We then did glow discharge to look at the grain at surface levels. The blades were hard, but the grain at electron micro levels was a mess. Picture 440C with bits of ATS-34 pounded in the surface.

Titanium: Most are alloys with Aluminum & Oxygen. Once fit and machined the SURFACE could be significantly altered by bead blasting and anodized, followed by heat. This was the exact process we used for implants. The silica blasting removes contamination and increases surface area for oxidation. The anodizing, if heat stabilized makes the surface very tough.

My recommendations:

Ti: Treat as described above.

Blades:
-Do NOT mix metals on grinding or polishing. Keep separate wheels for polishing.
-Surface clean, bead blast, rinse in distilled water. We use ultra sonics, blades in plastic bags, distilled water.
-Heat treat in small batches.

PS: Nothing cuts like 1095/Cable. Stainless is designed to RESIST corrosion, not cut better.
 
I'm no metallurgist (I can't even spell it without spell checker) but I see problems in the statements above. I don't want to become the instigator of drama on our forum that we want to keep drama free, but people (knifemakers in particular) have strong feelings about steel, when we state our opinions on this subject we usually wind up offending someone, I know because I have both offended and been offended :). I'll keep my reply friendly and hopefully others will too:

I'll just pick out one part of the above post to comment on

PS: Nothing cuts like 1095/Cable. Stainless is designed to RESIST corrosion, not cut better.
Click to expand...

Forge guys and stock removal guys don't usually see eye to eye on this subject, you work with what you like so naturally you support your favorites. I love and hate 1095, it's an excellent steel but the warpage during heat treat drives me nuts and too many people won't tolerate a knife that will rust that easily. I don't use much S30V but I strongly believe from my little experience with it and from talking to other knifemakers, that S30V will out cut 1095 easily, 1095 simply doesn't have the wear resistance of some of the better stainless's. I only picked this one steel because I have experience with it, I can't talk much about a steel like M4 witch is not stainless but since it is being used successfully in cutting completions must be one of the top performers.

Anyway, this subject has been beat to death over the years so I won't go any further :)
 
Les,

The main focus has to do with contaminating metals and wondering why they heat treat weird. It is an age old argument what is best settled by using what works best in your hands. This issue is mostly with stainless. I use clay or a torch with 1095/cable/damascus, no issue. Our quality jumped when we kept it clean.

I was just poking the tiger with the 1095 comment. :rolleyes:
 
So if this has to do with the surface alone, to what extent does this affect the performance of a sharpened edge?
-John
 
It possibly can have a dramatic effect. Simple to avoid; keep clean and don't contaminate. Try this as a demo; Rough forge or grind a blade, take filings drilling bits or whatever, mix with clay, apply and then heat treat. Now look at the surface, put an edge on it. Look at it under magnification with a little etch.
 
I am trying very hard to understand your post.

After HS I worked at a research lab, here in MD, and one of my first jobs as a lab tech, was sintering metal and ceramics. I worked in the area of metallurgy and ceramics for about 2-3 years. This was back in the 60s, so I understand how contaminates can be inadvertently sintered into the edge or surface of the metal.

I do not understand, however, how this would apply to a knife. The knife would be subsequently sharpened, after heat treating, whereby all contaminated layers at the edge would be removed. This would then allow any differences in alloy content to manifest changes in performances.

If the suggestion is, that this layer of sintered metal contaminate, is interfering with correct HRC readings, then this would seem doubtful since the surface layer would probably be thin enough not to affect the diamond penetrator.

I too, only desire exchanges in information and opinion, and certainly not heated debate and undue criticism.

Best wishes, Don
 
I can see that when forging and repeated heating can cause huge amounts of potential contamination and a clean work piece will aid in consistency, but to the stock removal maker I don't see much difference it makes. The steel is in a controlled atmosphere or wrapped in foil when heat treated. The steel won't have a chance to suck up contamination.

If I am working D2 and then switch to S30V I'm going through the belts and constantly changing them out so sintering would not seem like much of an issue (if I am understanding sintering).

Does anyone know if the steel can "absorb" the contaminant deep into the steel when it goes into solution at temperature like the carbon is drawn into the grain? Or does it stay more burned into the surface which would be removed as the blade is finish ground and polished?

Thanks
James
 
You must log in or register to reply here.
Back
Top