This is true. As a matter of fact, Jerry Hossom speaks about passivation. It still doesn't solve the problem though as anything that will remove the patina will get you back to square one.
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Fehrman vs Busse video
- Thread starter James0723
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This is true. As a matter of fact, Jerry Hossom speaks about passivation. It still doesn't solve the problem though as anything that will remove the patina will get you back to square one.
I don't think this is the case. If you read this comment from Jerry Hossom
you will see that the respone he got from Crucible Steel's chief metallurgist does not leave any room for "faulty steel". His reply just explains why this is the case with 3V.
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Iron oxide is rust. He is basically saying that the pitting is caused by rust. This is not unique to 3V but applies to any steel. CPM 3V does have some mild pitting resistance. You can calculate the pitting resistance by the equation:
PREN=%chromium+3.3x%molybdenum+16x%nitrogen,
where PREN is pitting resistance equivalent number and percents are in weight percent of elements in solid solution.
Source: http://www.eng-tips.com/faqs.cfm?fid=285
Gravelface
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After seeing him hold the Fehrman, I had to handle mine again, and again, to each his own.
While I like the Shadow Scout, different folks will get different things from the grip and his hold on the knife while his slashing and stabbing demo may have felt as though he could generate the most power and stability, his hold felt weak to me and honestly.......how many folks are going to actually use the knife in a slashing motion. Not too many knife fights with fixed blades going on these days.
And again, these are my opinions
Certainly not knocking either brand as I have many of each and believe that each produces a fine blade. At some task I would pick a Busse and others the Fehrman.
I have had more Patina and VERY light rust on my Busses than the Fehrmans, but it has never been a deal breaker.
While I like the Shadow Scout, different folks will get different things from the grip and his hold on the knife while his slashing and stabbing demo may have felt as though he could generate the most power and stability, his hold felt weak to me and honestly.......how many folks are going to actually use the knife in a slashing motion. Not too many knife fights with fixed blades going on these days.
And again, these are my opinions
Certainly not knocking either brand as I have many of each and believe that each produces a fine blade. At some task I would pick a Busse and others the Fehrman.
I have had more Patina and VERY light rust on my Busses than the Fehrmans, but it has never been a deal breaker.
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I'm getting quoted, and some might be just a little off the mark or need clarification.
The problem with corrosion of 3V is in fact oxide contamination in the base powders from which the steel is formed. This may be as small as parts per million, maybe even less of the 3V steel particles that are hipped to form the final steel. Yes, that oxide is rust, but the problem is not rust in the conventional sense, but those tiny rust spots are a nucleus for attracting/trapping additional oxygen which promotes further rust in the same area. Absent these nuclei, 3V is very corrosion resistant. I etch my 3V blades after they are done to a high quality brushed finish, then lightly rebrush them after etching. I THINK this removes those surface oxide nuclei, but in any case it seems to prevent the rust spots that might otherwise form.
All that said, if you put a light coating of a teflon containing synthetic gun oil (I use Birchwood Casey's), it seems to protect the steel forever. I've never had a problem after a single light coat of such oil, even a couple years later. I think this is because any initial (microscopic) spots attract the oil by capillarity and prevent further oxidation in the area where it might have formed a visible spot.
To put this in perspective, however, on an unprotected 3V blade having an area of maybe 1-1/4" x 6", you might see 6-8 spots when the problem arises. As has been said though, those spots sit atop a pit which can be fairly deep and not easily removed.
If anyone here thinks tool steels are meaningfully protected by a patina, you'll find 3V will corrode a whole lot less than your tool steel, patina or no.
Actually, this whole subject pisses me off because S30V was SUPPOSED to have been a tweaked CPM-3V, since all 3V needed to be corrosion resistant was a little help, NOT a MAJOR overhaul. They either had to remove or neutralize the tiny amount of oxide contamination or add just a little more free Chromium to surround it. By doing so they would have retained most if not all of the toughness of 3V even at the expense of a little hardness. INSTEAD, they added a whole bunch more Chromium (14% instead of 7.5% as in 3V), then added a ton more Carbon (1.45% compared with 3V's 0.8%) to make it hard again, which made the steel completely unlike 3V in every respect. THEN they added another point of Vanadium which took it to 4% and still called it S30V instead of S40V which it is. I can get very emotional on this subject...
The problem with corrosion of 3V is in fact oxide contamination in the base powders from which the steel is formed. This may be as small as parts per million, maybe even less of the 3V steel particles that are hipped to form the final steel. Yes, that oxide is rust, but the problem is not rust in the conventional sense, but those tiny rust spots are a nucleus for attracting/trapping additional oxygen which promotes further rust in the same area. Absent these nuclei, 3V is very corrosion resistant. I etch my 3V blades after they are done to a high quality brushed finish, then lightly rebrush them after etching. I THINK this removes those surface oxide nuclei, but in any case it seems to prevent the rust spots that might otherwise form.
All that said, if you put a light coating of a teflon containing synthetic gun oil (I use Birchwood Casey's), it seems to protect the steel forever. I've never had a problem after a single light coat of such oil, even a couple years later. I think this is because any initial (microscopic) spots attract the oil by capillarity and prevent further oxidation in the area where it might have formed a visible spot.
To put this in perspective, however, on an unprotected 3V blade having an area of maybe 1-1/4" x 6", you might see 6-8 spots when the problem arises. As has been said though, those spots sit atop a pit which can be fairly deep and not easily removed.
If anyone here thinks tool steels are meaningfully protected by a patina, you'll find 3V will corrode a whole lot less than your tool steel, patina or no.
Actually, this whole subject pisses me off because S30V was SUPPOSED to have been a tweaked CPM-3V, since all 3V needed to be corrosion resistant was a little help, NOT a MAJOR overhaul. They either had to remove or neutralize the tiny amount of oxide contamination or add just a little more free Chromium to surround it. By doing so they would have retained most if not all of the toughness of 3V even at the expense of a little hardness. INSTEAD, they added a whole bunch more Chromium (14% instead of 7.5% as in 3V), then added a ton more Carbon (1.45% compared with 3V's 0.8%) to make it hard again, which made the steel completely unlike 3V in every respect. THEN they added another point of Vanadium which took it to 4% and still called it S30V instead of S40V which it is. I can get very emotional on this subject...
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Thanks for the informative clarification. Do all CPM steels have oxide contamination, or is this just limited to 3V? I've had 1095 blades that pitted at the very edge, ruining the knife as holes ran throughout the steel, so that is my worst fear when it comes to knives. 3V's composition has some corrosion and some pitting resistance, but oxide/sulfide contamination could make it pit even worse than plain carbon steels according to the PREN calculation (in the negative range). Once it starts pitting, it is unstoppable murder on the steel.
Actually, this whole subject pisses me off because S30V was SUPPOSED to have been a tweaked CPM-3V, since all 3V needed to be corrosion resistant was a little help, NOT a MAJOR overhaul. They either had to remove or neutralize the tiny amount of oxide contamination or add just a little more free Chromium to surround it. By doing so they would have retained most if not all of the toughness of 3V even at the expense of a little hardness. INSTEAD, they added a whole bunch more Chromium (14% instead of 7.5% as in 3V), then added a ton more Carbon (1.45% compared with 3V's 0.8%) to make it hard again, which made the steel completely unlike 3V in every respect. THEN they added another point of Vanadium which took it to 4% and still called it S30V instead of S40V which it is. I can get very emotional on this subject...
I want a knife made out of stainless/pitless 3V, that would be amazing. Even though my tool/carbon steel knives don't rust anyway, the pitting scares me, as once it starts, it's unstoppable murder.
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All steels contain oxides when they come from the mill. They're incorporated into the steel when it's rolled or processed. Normally it doesn't make it's presence known, but CPM steels are a bit different. They are formed from very tiny steel particles that are essentially welded into a solid block of steel. The process is called "hipping". IF one of those steel particles has oxides on it's surface they are incorporated into the steel along with that particle, but in a manner that's a bit larger problem than the equivalent amount of oxides spread throughout an ingot of tool steel. In CPM, if the hipped particle that's contaminated is on the surface of the steel it forms a more meaningful nucleus around which rust can develop, because oxides are concentrated in that area. It's not just a molecule here and there; it's a lot of molecules in one spot. Countering this is any free Chromium that retards the development of rust, but there is no free Chromium on the surface.
As I mentioned, there are very few such particles on the surface of CPM-3V but you have to be aware that some are there. With tool steel, meaning any non-stainless steel with little or no free Chromium, all the steel on the surface is susceptible to oxidation and will rust, but it does so in a more friendly manner since you can see it better when the whole blade turns orange. You wipe it off, there are micropits all over the steel, but you don't see them. All steels rust, stainless steels rust less because they are protected by Chromium, tool steels rust more. Think not? Put any steel in a wet sheath for a couple days and see what you have when you take it out. Polishing helps, simply because it provides less surface area than is present on a rough surface and there are fewer places for water to be trapped to do its dirty work.
The PREN equation doesn't really apply to non-stainless steels nor to any steels which don't contain Manganese and Sulphur. PREN describes a process where the sulfide from Manganese Sulfide combines with the Chromium to form Chromium Sulfide which is basically taking away the Chromium's capacity to retard rust. It essentially reduces the amount of free Chromium in the area where there is Maganese Sulfide contamination - thus pitting in that area.
"PREN=%chromium+3.3x%molybdenum+(16 to 30)x%nitrogen"
These are the protective elements in the PREN equation. CPM-3V contains all three, though Crucible doesn't publish the amount of Nirogen. CPM-3V contains no Maganese or Sulphur.
Think about keeping your knives clean, dry and using a little oil now and then, even on stainless steel which isn't. It's been my experience that people who really care about knives do these things anyway. People with tool steel blades probably do it better because they know their blades can rust. People with stainless steel blades don't because they think they don't need to.
Good topic, I'm glad we could discuss it. Hopefully what I've written is clear enough to be useful. It's not a simple topic.
As I mentioned, there are very few such particles on the surface of CPM-3V but you have to be aware that some are there. With tool steel, meaning any non-stainless steel with little or no free Chromium, all the steel on the surface is susceptible to oxidation and will rust, but it does so in a more friendly manner since you can see it better when the whole blade turns orange. You wipe it off, there are micropits all over the steel, but you don't see them. All steels rust, stainless steels rust less because they are protected by Chromium, tool steels rust more. Think not? Put any steel in a wet sheath for a couple days and see what you have when you take it out. Polishing helps, simply because it provides less surface area than is present on a rough surface and there are fewer places for water to be trapped to do its dirty work.
The PREN equation doesn't really apply to non-stainless steels nor to any steels which don't contain Manganese and Sulphur. PREN describes a process where the sulfide from Manganese Sulfide combines with the Chromium to form Chromium Sulfide which is basically taking away the Chromium's capacity to retard rust. It essentially reduces the amount of free Chromium in the area where there is Maganese Sulfide contamination - thus pitting in that area.
"PREN=%chromium+3.3x%molybdenum+(16 to 30)x%nitrogen"
These are the protective elements in the PREN equation. CPM-3V contains all three, though Crucible doesn't publish the amount of Nirogen. CPM-3V contains no Maganese or Sulphur.
Think about keeping your knives clean, dry and using a little oil now and then, even on stainless steel which isn't. It's been my experience that people who really care about knives do these things anyway. People with tool steel blades probably do it better because they know their blades can rust. People with stainless steel blades don't because they think they don't need to.
Good topic, I'm glad we could discuss it. Hopefully what I've written is clear enough to be useful. It's not a simple topic.
I really enjoyed your comments on this subject as they contain very useful informative material. Thank you for passing on part of your knowledge.
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I'm guessing the N is a byproduct of how the powders are made. The molten steel is aerosolized into a cold nitrogen atmosphere, likely forming some nitrides in that process. Their keeping it secret, well not really secret but they don't list it with the formulation information, might be because the amount of N isn't entirely controllable and varies more than they'd like to reveal.
I've never mentioned it as a performance feature of 3V, and only mentioned it here in the context of the PREN discussion on pitting. Who knows? It might be one of the reasons 3V is as corrosion resistant as it is. No claims, no foul.
I've never mentioned it as a performance feature of 3V, and only mentioned it here in the context of the PREN discussion on pitting. Who knows? It might be one of the reasons 3V is as corrosion resistant as it is. No claims, no foul.
I have taken my 3V and INFI knives on several hunting trips.
In miserable weather, sometimes weeks at a time, the 3V knife has never shown any signs of corrosion.
The INFI blade retards corrosion pretty well too, but the edge doesn't hold as well as the 3V.
Overall, I prefer S30V to either. Damn tough steel if you ask me.
In miserable weather, sometimes weeks at a time, the 3V knife has never shown any signs of corrosion.
The INFI blade retards corrosion pretty well too, but the edge doesn't hold as well as the 3V.
Overall, I prefer S30V to either. Damn tough steel if you ask me.
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