What are carbides?

Lapedog said:
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.
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Not vertical. It’s actually parallel to the blade length. I’m trying to find a good representative picture.

Something like on this thread https://www.spyderco.com/forumII/viewtopic.php?t=72250, 2nd picture of the Endura, near the Bug. It’s hard to see but there’re lines parallel to blade length (not the grind finish, which is vertical), or first Endura image bear the border of dark and light areas (requires good lighting).
Found another good example: https://www.bladeforums.com/threads/need-help-on-endura-4-real-or-fake.1280034/
The first image near the bug.

It’s also often mentioned like post by Sharp Guy on this thread: https://www.spyderco.com/forumII/viewtopic.php?f=2&t=73077

All my VG10 Enduras have it but difficult to capture on camera. Are these the banding spoken about?
 
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halden.doerge said:
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.
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Thanks. Again, the claim was that it "aligns to the carbides." Like "the carbides move around in the steel and get in lines." The maker has a tendency to claim his products and methods defy the laws of physics and mathematics.
 
Interested**

Mete: I may have missed this, but what is the precipitation process?.

Chris: I'm probably wrong, but could that be another process like polishing? I notice some of my blades have a polished finish over the rough grind. I mean you'd think it would go the same way but who knows.

Thank you everyone. This is a big help!

Bo
 
B Bo-dacious If you want to get the attention of a member you can tag them with the @ symbol.
The way that I think of the precipitation process is like sweating (but it's probably more like boiling). When the steel is heated to transform it to austenite before the quench, carbides are formed at nucleation sites (commonly between grain boundaries) and new carbides are formed from the carbon and whatever alloying element(s) are present.

Edit: You really should read Larrin's articles. Most metallurgical information is geared towards industrial applications, whereas he relates it more specifically towards our knife interests!:thumbsup:
 
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Bo-dacious said:
Interested**

Mete: I may have missed this, but what is the precipitation process?.

Chris: I'm probably wrong, but could that be another process like polishing? I notice some of my blades have a polished finish over the rough grind. I mean you'd think it would go the same way but who knows.

Thank you everyone. This is a big help!

Bo
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Probably. Some has also suggested that. However the pattern is so irregular that it cannot be (IMO) result of polishing or buffing. It can be, though, brought out as a result of some buffing or polishing (comparing to katana blade polishing that brings out certain aspects of the steel to surface).
That was why I asked for insight from the experts here. ;)
 
mete said:
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. :confused:
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I was talking about finished product steel like bars or rolled steel. I believe before the steel is rolled the carbides are not typically in bands.
 
Chris "Anagarika" said:
Not vertical. It’s actually parallel to the blade length. I’m trying to find a good representative picture.

Something like on this thread https://www.spyderco.com/forumII/viewtopic.php?t=72250, 2nd picture of the Endura, near the Bug. It’s hard to see but there’re lines parallel to blade length (not the grind finish, which is vertical), or first Endura image bear the border of dark and light areas (requires good lighting).
Found another good example: https://www.bladeforums.com/threads/need-help-on-endura-4-real-or-fake.1280034/
The first image near the bug.

It’s also often mentioned like post by Sharp Guy on this thread: https://www.spyderco.com/forumII/viewtopic.php?f=2&t=73077

All my VG10 Enduras have it but difficult to capture on camera. Are these the banding spoken about?
Click to expand...

No the banding is made of microscopic carbides and you won’t be able to see it with your naked eye. I’m nit sure what those heel to tip lines are.
 
Chris , the beautiful hamon of a properly made katana is not brought to the surface by polishing ! ! The hamon is an area of various metallurgical structures . These , by the way are seen because the proper polishing of the hamon can only exist because the polishing is all done BY HAND ! A power too would destroy the delicate structures !

Lapedog, solidification of the ingot creates structures like massive carbides . These structures are broken down, strung out during rolling. We try to minimize the problem but traces remain. This is complicated by the specific alloy and HT. Remember also that most alloys are directional [the properties of the three directions are different .! ]
Banding involves more than just carbides.
 
Bo-dacious said:
danbot danbot okay great. A little hard to follow but good information. What is austentite?

@Chris yeah, just trying to help..

Thanks to those who helped out,

Bo
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Austenite is a solid solution of iron and Carbon. As steel is heated it goes through different phases until it reaches "critical" temperature. This is the point at which it's microstucture will transform to austenite (which is non-magnetic). Then it is held at (or just above) the critical temperature (soaked) for an appropriate amount of time (generally 1hour per inch of thickness) to ensure complete transformation to austenite through the entire piece. Then it is quenched (rapidly cooled) so that it does not have time to transform back through the phases into pearlite again. Instead it transforms to "untempered" martensite which is very hard and very brittle. Then it must be tempered to reduce hardness and increase toughness.
Hope this helps!
 
danbot danbot yes that helps. Still confusing but I know more now. I'll have to read a book on this when I begin to forge knives to know it inside and out.

Thanks,

Bo
 
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