Alloy banding / Carbide segregation

samuraistuart

samuraistuart

Joined
Dec 21, 2006
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As by request......What is the difference between alloy banding and carbide segregation? I haven't researched this much, but was under the impression they were the same thing. As Mete pointed out in another thread, "Banding is due to the mechanism of solidification of the molten steel !! Very early in the process ! Taking a look at an ingot after solidification the leaner [ lower amount of alloying elements] mix is on the outside and the mix becomes richer as you go to the center.] This becomes a big problem when working with large sections of tool steel where you have massive carbides !! You of course also have the dentritic structure just like when you start making wootz ! When you roll the steel you break down the dendrites .But the rolling also puts everything into bands. But the variation in composition from point to point creates the bands. in industry , no we don't want them !!"

So we can get banding during the rolling of the steel, but as I understand it from a metallurgist, it may also occur by excessive time/cycles in the subcritical heat range. Any thoughts?
 
We need Don to put up some more pics of that old W2 with the banding.

Hoss
 
Let me know when you find 20,000# of that stuff, I want some.

That stuff is cool.

Hoss
 
DevinT said:
Let me know when you find 20,000# of that stuff, I want some.

That stuff is cool.

Hoss
Click to expand...
You got it, Hoss.
butcher_block said:
don is that soem of the W2 round you sold a good many years back? i still have all of mine
Click to expand...
No, this is from 1/4"x1-1/4" flat bar. Only had 3 bars 6' long of this stuff. The round stock will show a faint damascus pattern sometimes, but no banding like this.
 
Almost looks like blister steel. I did have some 52100 do some heavy alloy banding. Very much like some of that W2. You could see where I had drawn it out with my dies. Looked like a wide ladder or as Nick says random ladder. Since I have been controlling my HT with the 52100 better though I no longer get the banding.
 
thought i lucked out and had a stash i only ended up holding on to killer clean and fantastic hanson W2
 
the impurity inclusions that are "stretched" by the mill act as preferred site, nucleation hot spots, for carbide precipitations.
That's why you could make it bold or minimize their appeareance through different heat cycles. Promoting carbide segregation you will "underline" them, and through omogeneization and dispersion of the carbides you make them almost invisible again, but those potential "strings" are still there.
 
"omogeneization"? I'm so out of my depth here.

Why don't the higher heat normalization cycles or austenitizing soak times disperse all those alloys and carbides like they're supposed to?
 
I'm starting to wonder that this may not be banding, but layers. Something that happen in the melt stage like was mentioned earlier?
 
To my inexperienced eyes, the blades Don posted look very much like the "hada" in my folded K120 steel katana. Not saying that IS what it is.....it just depends on what your definition of "Is"..is. Right, slick Willy?
 
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