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Old 05-08-2006, 12:23   #46
CPTAUSRET
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Quote:
Originally Posted by Bill Harsey
Do you refer to the sub-zero quench used in the heat treat process?

I haven't given up on the stainless question yet...Reaper has good answer but there is more.

Bill:

This process. http://www.nitrofreeze.com/

Terry
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Old 05-08-2006, 12:33   #47
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Quote:
Originally Posted by CPTAUSRET
Bill:

This process. http://www.nitrofreeze.com/

Terry
Terry, Much to this.
I always use liquid nitrogen (-320 F) as an integral step during the heat treat of the steels I use here, so does Chris Reeve. This is critical to the ultimate performance of the blade steels we use but is only good if integrated at the correct time during the hardening and tempering process.

There is much discussion about how much good a cryogenic treatment does after the part has concluded it's heat treat and has been made into a finished part.
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Old 05-08-2006, 13:22   #48
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Quote:
Originally Posted by Bill Harsey
Terry, Much to this.
I always use liquid nitrogen (-320 F) as an integral step during the heat treat of the steels I use here, so does Chris Reeve. This is critical to the ultimate performance of the blade steels we use but is only good if integrated at the correct time during the hardening and tempering process.

There is much discussion about how much good a cryogenic treatment does after the part has concluded it's heat treat and has been made into a finished part.
Interesting!

Good thread, Bill!

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Old 05-08-2006, 13:41   #49
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I'm just venturing a guess on the Stainless/ Tool steel question. Tool steels have higher carbide content which gives them their hardness. (here comes the guessing) Stainless has a higher chromium content which increases corrosion resistance but limits the hardness.

BTW, great thread.
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Old 05-08-2006, 15:45   #50
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For the stainless tool steel question: My answer is yes, you can have a stainless tool steel.

Reasoning: It may have to be a precipitation-hardened, nonstandard chromium steel, AISI types 632-635. I chose the precip-hardened steel since the Martensitic grade is heat treatable, while the Austenitic grade allows you to add an array of elements to change formability (Cr-Ni), intergranular corrosion resistance (Mo), hardness (C), etc.

TR probably answered most of it; I don't have the numbers in front of me to compare the aforementioned steels to tool steels.
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Old 05-08-2006, 19:23   #51
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CPTAUSRET,
After main work hours, here's more answer to your question about cryogenic treatment of tool steels.

The reason we deep freeze tool steels is to force retained austenite produced during the high temperature phase to convert to martensite.
This happens because the freezing increases the mechanical driving force in the steel to complete this transformation.
This must be done during the initial heat treat cycle or the steel tends to "set" and the freeze will have much less ability to do any good.

Retained austenite in the steel causes weakness and we don't like weakness around professionalsoldiers.com. Just ask the Team Sergeant.
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Old 05-08-2006, 19:54   #52
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Quote:
Originally Posted by mumbleypeg
I'm just venturing a guess on the Stainless/ Tool steel question. Tool steels have higher carbide content which gives them their hardness. (here comes the guessing) Stainless has a higher chromium content which increases corrosion resistance but limits the hardness.

BTW, great thread.
Your more right than you know. There is an entire area on the "tool steel alloy composition chart" where tool steels are stainless because of the addition of chromium. You swerved into something here too, too much chromium displaces other alloys and isn't as hard of a carbide.

Maybe I should explain what knifemakers call stainless, tool steels containing 14% chromium are considered pretty stainless. 14% is the threshold of "stainless" in a tool steel. D-2 has about 12% chromium and has some stainless characteristics but is more prone to the surface discoloration some folks call rust. The D-2 certainly doesn't rust much compared to other non-chrome tool steels.

An interesting thing to know about 14% chromium tool steels like 154CM (common good blade steel) is that the kind of heat treat can change the ability to not stain. Some of these steels have two distinct final temper ranges, high and low. When 154CM is tempered in the high temp range of over 900 F, the chromium carbides continue to form thus pulling usable chromium out of the matrix for stain resistance. The difference is noticable especially with 154CM knives used around salt water.
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Old 05-08-2006, 20:05   #53
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Quote:
Originally Posted by Maytime
For the stainless tool steel question: My answer is yes, you can have a stainless tool steel.
Correct.
The term "stainless steel" got a deservedly bad reputation back when manufacturers figured out that you don't have to use a good grade or do a good heat treat to sell knives. Hard use knife folks got it and the word was "stainless sucks".

Much has changed. For one the business of selling knives is very competitive and if quality slips, someone else gets your market share.
Steel companies are supplying good working grades of these steels on a regular basis to knife companies who are careful to get the heat treat right because reputation is everything.
We now have more metallurgists than ever before working directly with knife companies to keep this stuff sorted out.
(I keep my metal guys on speed dial. )

The knife buyer is the winner.

Now we have a grades of stainless tool steels with hardness, toughness and abrasive resistance properties that few tool steels could even dream about 20 years ago.

Last edited by Bill Harsey; 05-08-2006 at 20:14.
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Old 05-08-2006, 20:08   #54
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Bill:

Let's cut right to the chase.

If you had to build a fixed blade knife that was going to be your only tool to survive with out in the woods (in combat), and you could have any alloy you wanted, in the dimensions you wanted, what steel would you pick?

What would it be for a folder?

That is really what we want to know.

TR
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Old 05-08-2006, 20:19   #55
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Quote:
Originally Posted by The Reaper
Bill:

Let's cut right to the chase.

If you had to build a fixed blade knife that was going to be your only tool to survive with out in the woods (in combat), and you could have any alloy you wanted, in the dimensions you wanted, what steel would you pick?

What would it be for a folder?

That is really what we want to know.

TR
The same stuff I'm using now, CPM S-30V for both.

Edited to add, some may be familiar with a few of the knives made with this steel.


Edited to continue: Reaper, as you probably know, we never stop testing new steels as we can get our hands on them. Yes there are a couple very exotic and difficult to work steels that can do a thing or two better than CPM S-30V and they are very cost prohibitive to manufacture and there will be huge downsides to the user.

These steels would defy re-sharpening in the field making them of little use to the soldier.


My answer remains CPM S-30V steel.

Last edited by Bill Harsey; 05-14-2006 at 19:19.
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Old 05-08-2006, 21:18   #56
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How we pick a knife steel...

As is beginning to be discussed here, tool steels are made from many different recipes of alloys.

The purpose of these choices is to try and combine multiple physical properties we want in a single piece of steel for a specific edged tool.

For a knife we want it to get sharp and stay sharp as long as possible while being able to use as a prybar if needed. These are two distinct and seperate physical properties.

Stain resistance is important to "sharp". We can lose the edge on a non-stainless knife without ever using it if your in the right geographic location like a warm marine or tropical climate.

If we pick any single steel designed for a single trait, there will be many other steels that do the other traits better.

These are some of the things we have to think about when choosing a tool steel for extreme use knives.

We haven't spoken about "particle metal steels" yet (CPM S-30V is one of them)... this stuff is gonna get like science fiction, only better.
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Old 05-09-2006, 02:47   #57
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Quote:
Originally Posted by Bill Harsey
Correct.
The term "stainless steel" got a deservedly bad reputation back when manufacturers figured out that you don't have to use a good grade or do a good heat treat to sell knives. Hard use knife folks got it and the word was "stainless sucks".

Much has changed. For one the business of selling knives is very competitive and if quality slips, someone else gets your market share.
Steel companies are supplying good working grades of these steels on a regular basis to knife companies who are careful to get the heat treat right because reputation is everything.
We now have more metallurgists than ever before working directly with knife companies to keep this stuff sorted out.
(I keep my metal guys on speed dial. )

The knife buyer is the winner.

Now we have a grades of stainless tool steels with hardness, toughness and abrasive resistance properties that few tool steels could even dream about 20 years ago.

Speaking of hardness and toughness. In the mid 70's I got a Puma Skinner. Still have it. Up the blade is the 'diamond punch mark' Did a quick search on the net. The design is like the top knife in that pic. However, There isn't any etching/writing on that side of my knife. It is on the opposite side and different. it is the 6393, serial # 56472.

http://www.foxridgeoutfitters.com/de...1&product=4109
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Old 05-09-2006, 08:44   #58
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Quote:
Originally Posted by 12B4S
Speaking of hardness and toughness. In the mid 70's I got a Puma Skinner. Still have it. Up the blade is the 'diamond punch mark' Did a quick search on the net. The design is like the top knife in that pic. However, There isn't any etching/writing on that side of my knife. It is on the opposite side and different. it is the 6393, serial # 56472.

http://www.foxridgeoutfitters.com/de...1&product=4109
Brad,
I'll assume your asking what steel this is and I don't know but I can ask the owner of Boker or his top knife designer over in Germany. Everyone knows what their competitor is doing.

The "diamond punch mark" is the impression left by the point on the Rockwell hardness tester. The diamond is gently preloaded onto the flat and parallel surface of the heat treated blade, while it rests on the machines anvil, then a known pre-set load is applied. The depth of this impression is carefully gauged by a large readable dial on the Rockwell hardness tester and the user reads off the hardness.
The less the penetration, the harder the steel.

A Rockwell Hardness test is that of testing a given steel or other materials ability to resist surface indentation.
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Old 05-09-2006, 11:05   #59
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In selecting steel, what we really need to do first is to determine what we want the blade to do.

The use of the item, and the characteristics we need will decide its optimal composition.

A soldier, a butcher, a surgeon and a gift-wrapper may all use knives, but what they are doing with them are completely different, as are their ability to maintain them. A surgeon may toss a multi-hundred dollar instrument, the soldier spend it reluctantly, but be unable to care for it and maintain it like the butcher, where the gift-wrapper will not spend over $10 for one, and will probably throw it out (or change blades) when dull.

The best steel is always going to be a compromise between multiple factors, only the user can decide whether a particular product is worth the price. For the soldier, I believe that the primary characteristic sought is toughness. For the butcher, it may be edge-holding, for the surgeon, it may be sharpness, for the gift-wrapper, it may be price.

Speaking of price, I know that steel prices are a portion of the finished product's costs, and that the time and abrasives it takes to prepare the steel is another portion of the cost. Clearly, CPM S-30V is a great steel for those serious users who can afford it, but is may not be the right steel for a knife going on the shelves at your local Wally-Mart.

Bill (or Mick, or any of the other makers here), can you elaborate at some point on the relative prices of the steel, the abrasives, the heat treat, and the time spent working it to the final cost of the knife?

Thanks much, great thread.

TR
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Old 05-09-2006, 18:22   #60
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Reaper,
Good overview, Your spot on about many things in your comments.

It is like trying to hit a moving target to find a tool steel that gives us the desirable performance traits in a knife and it does depend on the job your doing.

Let's stick to tactical knives and please remember:

"The biggest difference between knives is any knife over no knife at all"
(-Bob Loveless 1986, while I was his guest in his shop)

Yes we are guilty of trying to make the best possible knives with the best possible steel and it doesn't come cheap. The better the steel, the higher the price and we pay a premium for the steel alone and because of the properties we desire in the knife this correspondingly makes the manufacturing costs higher because of hardness and toughness to machine, grind and finish correctly .

CPM S-30V is running right at three to four times as expensive as other tool steels that knives could be made from. I haven't gone down the list of alloys and what they do yet so here is a start because it goes to "cost of making"..

CPM S-30V has, among other things, Vanadium in it, enough to form Vanadium carbides. Vanadium carbides are harder than the abrasive grit aluminum oxide. This is why this steel has some very good edge holding and abrasion resistance and it really sucks to grind and finish compared to other tool steels at the same hardness.

World markets are directly effecting the price we pay for steel. There is great competition for iron and all the other alloys that go in it. China is a huge factor in this situation. I'm seeing "surcharges" on my steel bill because of the added cost of getting particular alloys from various parts of the world.
This all goes to cost of manufacturing.

We also think the performance gained, as measured in toughness, edge holding and stain resistance, is worth it in life critical tools.

I would still take the knife forged out of a truck spring over no knife at all.
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