Why there is Cobalt in VG-10

Great article... for those who actually have a background in metallurgy! How precise it is, I don't know. How true? I don't know either. But sure is well structured. I can appreciate that.

Thanks for your effor Larrin!
 
very good write up, with a difficult element ;) I like to mention as an aside, it's also one of the few elements needed by us for biological processes (which I find interesting but has nothing to do with steel)
 
So, what I get from this article, is that VG-10 and N690 really offer no advantages over similar steels as far as use in blade steel is concerned, unless they are subject to a surface treatment that requires a high temperature application. And these types of coatings are primarily for corrosion resistance are they not?
 
danbot said:
So, what I get from this article, is that VG-10 and N690 really offer no advantages over similar steels as far as use in blade steel is concerned, unless they are subject to a surface treatment that requires a high temperature application.
Click to expand...
Some people like to have some tempering resistance to help with heating of edges during grinding. I did not mention that in the article.
And these types of coatings are primarily for corrosion resistance are they not?
Click to expand...
I would say yes, though in some cases it is cosmetic (black knives are tactical).
 
Larrin, Does the cobalt have less/different effects when at lower compositions? Example ATS 55 with .40 % ( but with added copper ?)

Thanks again Larrin. I'm having to read these a couple times also to digest them and you are going pretty easy on us.

Joe
 
The Mastiff said:
Larrin, Does the cobalt have less/different effects when at lower compositions? Example ATS 55 with .40 % ( but with added copper ?)
Click to expand...
You mean just the amount of cobalt is lower or that the overall composition of the steel is leaner?
 
Interesting article. I wonder if the cobalt in powder steels (by Crucible, Carpenter, Bohler) acts differently.
 
It also sounds cool to tell the people that ask about my funky purple handled knife with the spider and a hole in the blade, that it has cobalt.
 
Alberta Ed said:
Interesting article. I wonder if the cobalt in powder steels (by Crucible, Carpenter, Bohler) acts differently.
Click to expand...
It probably depends on which steel you are referring to. The article describes the reason for using cobalt in Crucible's S110V, for example.
 
Korean Hog said:
It also sounds cool to tell the people that ask about my funky purple handled knife with the spider and a hole in the blade, that it has cobalt.
Click to expand...
Ha! Is cobalt more impressive than chromium, molybdenum, or vanadium?
 
"You mean just the amount of cobalt is lower or that the overall composition of the steel is leaner?"

Both ATS 55 and VG10 are 1% steels with similar chrome percentages.

Is the Cobalt in ATS 55 for the same reasons as it is in VG10 or does it work differently because of things like added copper in ATS 55?

Is the copper there to work with / or in place of more cobalt?

Also just having Cobalt wouldn't give these steels any red hardness like a HSS would it?

"Ha! Is cobalt more impressive than chromium, molybdenum, or vanadium?"

Or worse to breathe in when hand sharpening?

Thanks.




Joe
 
The Mastiff said:
"You mean just the amount of cobalt is lower or that the overall composition of the steel is leaner?"

Both ATS 55 and VG10 are 1% steels with similar chrome percentages.

Is the Cobalt in ATS 55 for the same reasons as it is in VG10 or does it work differently because of things like added copper in ATS 55?

Is the copper there to work with / or in place of more cobalt?

Also just having Cobalt wouldn't give these steels any red hardness like a HSS would it?
Click to expand...
A 0.4% cobalt addition is pretty small. I don't know what they were trying to accomplish with that.

I'm not aware of any interactions between cobalt and copper; they don't have a similar effect.

Red hardness is achieved primarily through Mo or W additions (through V and Cr also have a contribution), cobalt simply enhances the effect of those elements.

Edit: I forgot about copper-induced "hot shortness." Additions of cobalt or nickel help prevent this effect of copper.
 
"I forgot about copper-induced "hot shortness." Additions of cobalt or nickel help prevent this effect of copper."

I had to go look that up. It makes sense now, thanks!

Joe
 
ATS 55 was a cost cutting measure when announced. Most of the performance of ATS 34 without the added cost of the Moly. They are known for using virgin iron for the premium cutlery steels. That little two step would allow the use of recycled steel with steps taken to contain the drawbacks of the copper. On the other hand that is pretty high copper for just recycled steel so maybe it is there for whatever reason. Corrosion resistance?
Joe
 
The Mastiff said:
"You mean just the amount of cobalt is lower or that the overall composition of the steel is leaner?"

Both ATS 55 and VG10 are 1% steels with similar chrome percentages.

Is the Cobalt in ATS 55 for the same reasons as it is in VG10 or does it work differently because of things like added copper in ATS 55?

Is the copper there to work with / or in place of more cobalt?

Also just having Cobalt wouldn't give these steels any red hardness like a HSS would it?

"Ha! Is cobalt more impressive than chromium, molybdenum, or vanadium?"

Or worse to breathe in when hand sharpening?

Thanks.




Joe
Click to expand...

According to zknives.com, which has been a pretty good resource.

Cobalt: increases hardness, allows for higher quenching temperature during heat treatment procedure, intensifies the effects of other elements in more complex steels. Cobalt is not a carbide former but allows for higher attainable hardness and higher red hot hardness.
 
The Mastiff said:
ATS 55 was a cost cutting measure when announced. Most of the performance of ATS 34 without the added cost of the Moly. They are known for using virgin iron for the premium cutlery steels. That little two step would allow the use of recycled steel with steps taken to contain the drawbacks of the copper. On the other hand that is pretty high copper for just recycled steel so maybe it is there for whatever reason. Corrosion resistance?
Joe
Click to expand...
It could be that the copper was simply a maximum due to the use of recycled steel and there was miscommunication about what the spec meant. It's hard to know what exactly they were thinking if it was an intentional addition.
 
So let me ask: people love M4, especially CPM M4, for hard use knives. CPM Rex 45 is basically CPM M4 + cobalt. Shouldn't that then make for an even tougher, easier to work with M4? Why doesn't anyone use Rex 45 for knives - availability?
 
You must log in or register to reply here.
Back
Top