Are these carbide banding?

L

Laurarium

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What are these strips?
There is also a video, I believe is by another member here.
And there is a comment analyzing the strips, just as a side note.
 
Jerry Busse said:
Don't panic. . . It's a good thing. . . 👍

What you're seeing is the grain stucture of the steel. . . .They all have it. You have to hold it at the right angle to see but they are there... 👍

They are created when the steel is rolled lengthwise at the mill. . .. and just like wood, the direction of the grain adds to the lateral strength. . . .

Think of them as nuclear rebar reinforcing the blade. . . 👍

Let's Drink! 👍

Jerry :D
INFIGrainStructure.jpg
Click to expand...
 
You’re welcome. Apparently Stump was on the case while I was posting. Two minds with but a single thought. 👍
That quote from Jerry was on 11/15/2010 in a thread titled “Does your anorexic BOSS Street blade look like this?”
 
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I want all my Busse’s to have Nuclear Rebar!!
I had one once.. pretty sure it was a AMS also?? Sad I passed it along …No Wait….Did I pass that along to you ? Aw well…..No Regrets !!
 
SwissHeritageCo said:
Can someone point me to a photograph that shows actual carbide banding?

I just recently traded for a knife that has weird little horizontal artifacts in it.
Click to expand...
I think these stripes are in deed carbide banding.
Ideally we don’t want them, but it is not necessarily going to be a problem.
Carbide banding are caused by the slow cooling rate of large ingots, powder steels cool very fast in atomizers, so they don’t have carbide banding.
However, when carbide volume is very high, even powder steels form clusters of carbide.
 
I’ve never really understood, if the grain showing in INFI is imparted by rolling at the mill, why it apparently follows the curve of the belly on individual blades.
 
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Did a bit of late night rabbit hole research and I to believe it may be a bit of both the rolling AND carbide banding. Whether it's good or not seems to be up for debate as a uniform steel is ideal as Laurarium pointed out.
I wonder if too much banding is what caused that one AFBM to break out like it did.
The ASH2 on the other hand there was no edge deterioration.


I also found this info from American bladefmith society. Seems alloy banding is pretty common but does show what direction the steel was rolled in, which is a good thing, but overall uniformity is the goal.

"When the steel is poured at the mill the different elements in it will want to solidify at different rates. Since metals are crystalline in nature they will do this in just such a fashion making fern or tree like structures within the steel of higher concentrations of different elements, these are called dendrites due to their tree like appearance. Dendritic, or ingotized steel is very problematic to many steel properties and workability in a consistent manner so industry does all it can to counteract the problem. The first thing they do is subject the steel to heavy reduction by rolling, this breaks up the dendrites and rearranges them in an elongated form, stretched along the length of the steel in the direction of rolling. This gives steel a directional property so that instead of the segregation and other issues weakening the steel in all directions (isotropic), it makes the steel stronger along one access and not quite as so much along another (anisotropic). If you impact test steel perpendicular to this flow it is quite strong but if you impact it parallel to it is significantly weaker. After the rolling the steel is then subjected to various heat cycles to break any chemical compounds that want to hang out in the segregated areas and mix them evenly throughout, but the atoms that caused the segregation are much slower to move than things like carbon and there will still be zones in the steel prone to this concentration if the steel is not heat treated properly to avoid it.

Things like heavy thermal cycling and slow cooling from high temperatures will allow carbon to gather in places like this and accentuate the alloy banding. For the most part it is nothing to lose too much sleep over, but if it gets heavy enough to be really visible it can affect the steels consistency in its properties. For instance, in the case of higher carbon steels you will get bands and heavy sheeting of carbides that can have odd effects on the edge. Some people like the way such an edge cuts because they think it is sharper but it is actually less stable and sharpens in a rough and toothy manner and then as it cuts it wears in a very ragged way that allows it to tear through soft fibrous materials like rope and paper, but it does not handle other cuts and materials nearly as well. Another thing to beware of is how much carbon is trapped in the banding and if there is any leftover to fully harden the steel around it. Some steels are much more prone to it than others due to alloying. O-1 is one that will really band out if not heated just right and I often see subtle banding in the habuchi area of 10XX blades that have a hamon. If you see it before the final heat treatment it is easily erased by heating well above critical, holding for a bit followed by a quick air cool. This puts the segregation into solution and then robs it of the time required for going back into the concentrated areas when it comes out of solution. Heavily banded steel can be very ductile in its annealed form, (as was found in the research of Wadsworth and Sherby) since the material between the bands is almost pure iron but ductile is the opposite of strength and not necessarily synonymous with toughness.

In virtually every modern application steel reaches its highest levels of performance by homogeneity, the more even and smooth the internal structure, the more evenly it will respond to our heat treatments and handle forces applied to it, this is why industry and bladesmiths pay such close attention to things like normalizing, since heavily segregated materials are much less predictable than homogenous materials.

Some find banding interesting but its effects are purely aesthetic at best and somewhat detrimental at its worst." - Kevin R. Cashen
 
Jack of All Blades said:
Did a bit of late night rabbit hole research and I to believe it may be a bit of both the rolling AND carbide banding. Whether it's good or not seems to be up for debate as a uniform steel is ideal as Laurarium pointed out.
I wonder if too much banding is what caused that one AFBM to break out like it did.
The ASH2 on the other hand there was no edge deterioration.


I also found this info from American bladefmith society. Seems alloy banding is pretty common but does show what direction the steel was rolled in, which is a good thing, but overall uniformity is the goal.

"When the steel is poured at the mill the different elements in it will want to solidify at different rates. Since metals are crystalline in nature they will do this in just such a fashion making fern or tree like structures within the steel of higher concentrations of different elements, these are called dendrites due to their tree like appearance. Dendritic, or ingotized steel is very problematic to many steel properties and workability in a consistent manner so industry does all it can to counteract the problem. The first thing they do is subject the steel to heavy reduction by rolling, this breaks up the dendrites and rearranges them in an elongated form, stretched along the length of the steel in the direction of rolling. This gives steel a directional property so that instead of the segregation and other issues weakening the steel in all directions (isotropic), it makes the steel stronger along one access and not quite as so much along another (anisotropic). If you impact test steel perpendicular to this flow it is quite strong but if you impact it parallel to it is significantly weaker. After the rolling the steel is then subjected to various heat cycles to break any chemical compounds that want to hang out in the segregated areas and mix them evenly throughout, but the atoms that caused the segregation are much slower to move than things like carbon and there will still be zones in the steel prone to this concentration if the steel is not heat treated properly to avoid it.

Things like heavy thermal cycling and slow cooling from high temperatures will allow carbon to gather in places like this and accentuate the alloy banding. For the most part it is nothing to lose too much sleep over, but if it gets heavy enough to be really visible it can affect the steels consistency in its properties. For instance, in the case of higher carbon steels you will get bands and heavy sheeting of carbides that can have odd effects on the edge. Some people like the way such an edge cuts because they think it is sharper but it is actually less stable and sharpens in a rough and toothy manner and then as it cuts it wears in a very ragged way that allows it to tear through soft fibrous materials like rope and paper, but it does not handle other cuts and materials nearly as well. Another thing to beware of is how much carbon is trapped in the banding and if there is any leftover to fully harden the steel around it. Some steels are much more prone to it than others due to alloying. O-1 is one that will really band out if not heated just right and I often see subtle banding in the habuchi area of 10XX blades that have a hamon. If you see it before the final heat treatment it is easily erased by heating well above critical, holding for a bit followed by a quick air cool. This puts the segregation into solution and then robs it of the time required for going back into the concentrated areas when it comes out of solution. Heavily banded steel can be very ductile in its annealed form, (as was found in the research of Wadsworth and Sherby) since the material between the bands is almost pure iron but ductile is the opposite of strength and not necessarily synonymous with toughness.

In virtually every modern application steel reaches its highest levels of performance by homogeneity, the more even and smooth the internal structure, the more evenly it will respond to our heat treatments and handle forces applied to it, this is why industry and bladesmiths pay such close attention to things like normalizing, since heavily segregated materials are much less predictable than homogenous materials.

Some find banding interesting but its effects are purely aesthetic at best and somewhat detrimental at its worst." - Kevin R. Cashen
Click to expand...
Nice info.
I think afbm is a fluke, the cracks has weird color in it, probably a bad blank.
Ironic said:
I’ve never really understood, if the grain showing in INFI is imparted by rolling at the mill, why it apparently follows the curve of the belly on individual blades.
Click to expand...
In my opinion, I think the banding happened in heat treatment.
Though banding formed in ingots can be removed by dissolving the carbides, the alloy elements stil can’t move freely as in molten metal.
Therefore, the alloy segregation is not fundamentally eliminated and carbide banding can reappear in heat treament.
And this is why banding appears to follow the blade shape, instead of being straight lines:
During low tmeperature cycles, as the blades cool faster around its edges and at thinner sections, banding formed according to the blade shape, along lines at the same colling rate.(think of topo maps)

I think banding is a by product of the protocol in combination with the nature of the steel, although banding by itself is not desirable, the overall protocol still yeilds great performance.

I don’t have any recently released santin finish busse knives, it would be nice if someone would have a look and see if recent blades also have the banding.
 
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Ironic said:
I’ve never really understood, if the grain showing in INFI is imparted by rolling at the mill, why it apparently follows the curve of the belly on individual blades.
Click to expand...

The blade I have the artifacts/banding on is in 14c28n... but the lines do indeed follow the curve of the belly all the way to the tip. The only other time I've seen weird artifacts in the finish of a steel was a Ganzo, but they weren't linear bands that follow the curve of the belly like this one.


Edit to add: the knife I'm questioning is not a busse.
 
Laurarium said:
…
In my opinion, I think the banding happened in heat treatment.
Though banding formed in ingots can be removed by dissolving the carbides, the alloy elements stil can’t move freely as in molten metal.
Therefore, the alloy segregation is not fundamentally eliminated and carbide banding can reappear in heat treament.
And this is why banding appears to follow the blade shape, instead of being straight lines:
During low tmeperature cycles, as the blades cool faster around its edges and at thinner sections, banding formed according to the blade shape, along lines at the same colling rate.(think of topo maps)
Click to expand...

Interesting theory.

Maybe Jerry will clear this up. 👍
 
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SwissHeritageCo said:
The blade I have the artifacts/banding on is in 14c28n... but the lines do indeed follow the curve of the belly all the way to the tip. The only other time I've seen weird artifacts in the finish of a steel was a Ganzo, but they weren't linear bands that follow the curve of the belly like this one.


Edit to add: the knife I'm questioning is not a busse.
Click to expand...
I think the banding that follows the blade shape is the secondary banding that reappeared during heattreat.
 
Interesting…. If I recall my Choppasarus has some quite heavy banding. Will further investigate this evening.
 
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