What are carbides?

[NJBillK]

Larrin and @knarfeng , you guys are the heavy hitters (no offense to everyone else, no doubt you all will agree)...so I have a carbide question for you two that I have had for years.

Can they be "aligned" in steel? If they can, can they aligned by stropping?

Eta: Yes, I do agree about those two gentlemen. Thank you both.
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I would think that they can be when stropping with the correct media. If someone has a diamond paste, when stropping, they are abrading the surface ever so slightly. If this surface happens to contain Vanadium or Niobium carbides, they will be cut by the Diamond content of the paste.

While it isn't "aligning" the carbides by movement of mass (straightening a roll for example), it is aligning them by removal of mass that is not in plane and and centered on the apex of the cutting edge.

This should happen any time the abrasive media is harder than the cutting edge and carbides, be it for better or worse (sharpening vs. blunting).

 

[Larrin]

When sharpening you are grinding away steel and carbides not really changing the shape of anything, so no aligning of the carbides.

 

[marcinek]

When sharpening you are grinding away steel and carbides not really changing the shape of anything, so no aligning of the carbides.

And with stropping on a leather strop hone loaded with emery or chrome oxide? Does that process "align" the carbides in the steel?

 

[Bo-dacious]

Lapedog: what do these rows do and what happens when these rows are broken up?

Someone Said that free carbon reacts with other elements. And that if nothing else, it reacts with some iron, forming cementite.
What else can it do in those reactions, and what exactly is cementite?

Thanks guys,

Bo

 

[danbot]

Lapedog: what do these rows do and what happens when these rows are broken up?

Someone Said that free carbon reacts with other elements. And that if nothing else, it reacts with some iron, forming cementite.
What else can it do in those reactions, and what exactly is cementite?

Thanks guys,

Bo

Cementite is an Iron carbide. When Iron bonds with Chromium, it forms Chromium carbides, when it bonds with Vanadium it forms Vanadium carbides etc. Carbides increase wear resistance, but decrease toughness.

 

[Lapedog]

Lapedog: what do these rows do and what happens when these rows are broken up?

Someone Said that free carbon reacts with other elements. And that if nothing else, it reacts with some iron, forming cementite.
What else can it do in those reactions, and what exactly is cementite?

Thanks guys,

Bo

First off let me say that I am a total novice when it comes to these things. There are members here who’s knowledge on this subject is a TRex compared to mine which is more like an ant.

The bands can apparently behave sort of like the grain in wood making the steel stronger against breaking in one direction and more likely to break in another. Like how wood can break more easily depending on how the force is applied.

If we look at a wood baseball bat standing on its end the grain runs end to end vertically which makes the bat stronger against breakage. If the grain ran horizontally through the bat (parallel to the floor the bat is standing up on) it would be easier to break the bat.

Seems like that is part of the reason knife makers anneal the steel to try to get rid of the carbide banding. (Annealing means heating the steel just enough that those carbides dissolve back into the steel) So that way the knife isn’t more likely ti break in a certain direction.

Cementite is just the name for iron carbides.

 

[Larrin]

And with stropping on a leather strop hone loaded with emery or chrome oxide? Does that process "align" the carbides in the steel?

You might align a burr.

 

[danbot]

First off let me say that I am a total novice when it comes to these things. There are members here who’s knowledge on this subject is a TRex compared to mine which is more like an ant.

The bands can apparently behave sort of like the grain in wood making the steel stronger against breaking in one direction and more likely to break in another. Like how wood can break more easily depending on how the force is applied.

If we look at a wood baseball bat standing on its end the grain runs end to end vertically which makes the bat stronger against breakage. If the grain ran horizontally through the bat (parallel to the floor the bat is standing up on) it would be easier to break the bat.

Seems like that is part of the reason knife makers anneal the steel to try to get rid of the carbide banding. (Annealing means heating the steel just enough that those carbides dissolve back into the steel) So that way the knife isn’t more likely ti break in a certain direction.

Cementite is just the name for iron carbides.

I don't think annealing has much effect on carbide banding. It just gets the steel to a uniform pearlite structure for ease of working. The segregated carbides would tend to stay put.

 

[Lapedog]

I don't think annealing has much effect on carbide banding. It just gets the steel to a uniform pearlite structure for ease of working. The segregated carbides would tend to stay put.

I definitely could be wrong about that.

 

[Korean Hog]

Talk about getting down to the nitty gritty of knives....
This is a cool thread

 

[marcinek]

You might align a burr.

Thanks. A long time ago a maker made the claim that stropping "aligns the carbides." Never bought that story, especially the coming from the source, but I'm no steel expert.

 

[Larrin]

Annealing typically does not eliminate carbide segregation though it can be significantly reduced in some simple carbon and low alloy steels with certain types of cycles.

 

[Bo-dacious]

Thank you very much guys. I'm slowly getting more knowledgeable thanks to you all. I will read that article on carbides as soon as I can.

Korean: yes, I'm trying to learn everything I can about knives. If I realize I don't know something, I write it down and look it up later. If I can't find it, I ask about it on here. I'm very I retested in this nitty gritty stuff, like many of you!

Thanks fellas,

Bo

 

[me2]

This is kind of an old thread, but it might be helpful for this discussion.

www.bladeforums.com/threads/grains-carbides-and-you.1208483/

 

[Wowbagger]

If I realize I don't know something, I write it down and look it up later. If I can't find it, I ask about it on here. I'm very I retested in this nitty gritty stuff, like many of you!

 

[Chris "Anagarika"]

Is the banding shown by Lapedog what people usually refer to VG10 having special texture (obvious on Spyderco Seki series)?

 

[Lapedog]

Is the banding shown by Lapedog what people usually refer to VG10 having special texture (obvious on Spyderco Seki series)?

I think you are talking about the vertical lines that run spine to edge along the blade? This is actually just the satin finish. Carbides are microscopic. You won’t see their effects with the naked eye.

 

[halden.doerge]

Thanks. A long time ago a maker made the claim that stropping "aligns the carbides." Never bought that story, especially the coming from the source, but I'm no steel expert.

Stropping hones and burnishes the apex of the edge, which includes both the steel matrix and the carbides at the apex. There may be some sort of alignment happening when you strop, but what's really being "aligned" is not the microstructure of the steel, but any imperfections in the apex.

 

[mete]

Lapdog. Well you haven't been in a steel mill where the steel is poured into ingot molds. As the ingot cools and solidifies the center of the ingot is richer in alloying elements .cutting the ingot and with just a rough grind you will see what we call " massive carbides " Yes they are massive and they cause lots of problems when processing the steel . So you then can understand why we metallurgists have spent lots of time trying to keep carbides small.
On the other extreme we have something like eta carbides which requires a microscope to see !
Carbides are a mixture of metals and carbon. They are different in hardness and melting point . Bonding between the metal and carbon can be very complex. While some carbides come from the original steel, others form from precipitation process.

 

[Mecha]

Lapdog. Well you haven't been in a steel mill where the steel is poured into ingot molds. As the ingot cools and solidifies the center of the ingot is richer in alloying elements .cutting the ingot and with just a rough grind you will see what we call " massive carbides " Yes they are massive and they cause lots of problems when processing the steel . So you then can understand why we metallurgists have spent lots of time trying to keep carbides small.
On the other extreme we have something like eta carbides which requires a microscope to see !
Carbides are a mixture of metals and carbon. They are different in hardness and melting point . Bonding between the metal and carbon can be very complex. While some carbides come from the original steel, others form from precipitation process.

Yes yes. Precipitation process.