Another wootz question

[ariel]

I seem to have more and more of them...
My next one: does the wootz pattern ( for example, khorasan vs. sham) reflect an intrinsic pattern of the ingot or do the more complex patterns result from more sophisticated manipulations of the original material by the bladesmith? In other words: could the smith take any wootz-y ingot and, by turning it, drawing under different angles, twisting etc, produce a complex pattern? Were all ingots created equal or did the smith choose a particular one to produce an "Assadollah-style" blade?

[kisak]

I suspect that it is at least largely dependant upon the ingot. Looking through Manouchehr's book he mentions that the finer pattern of Indian wootz would be due to quick cooling, resulting in a finer grain structure (which makes metallurgical sense). So that's one form of pattern which is ingot-dependant.

There would seem to be a limit to the amount of deformation you'd want to subject the steel to as well. Working it will tend to reduce the distances involved in the chemical segregation which forms the basis of the pattern, greatly reducing the time the steel can be kept hot before aid segregation starts to fade and disappear.

Also, taking the chance to add a question of my own. If we first look at http://www.tms.org/pubs/journals/JOM...even-9809.html it mentions that depending on how the steel was heat treated, we'd generally get bands of carbides in a pearlite matrix. In Manouchehr's book there's also mention of low-carbon variants (hypoeuctectoid) where the pattern is formed by ferrite banding instead.

This then raises the question of just how these blades would have been heat treated. To the best of my knowledge, any ferrite remaining in such low-carbon steel after the normal heat-quench-temper treatment would indicate that the heating stage wasn't properly done (too short soak time), whereas pearler turning up in the more high carbon steels would either indicate a rushed heating there as well, or an insufficient quenching leaving retained austenite (which can then decay into pearlite). In either case, as both ferrite and pearlite are considerably softer than martensite the hardened form of steel basically) and the carbides, I've been thought that the presence of either is to be considered a failure in most cases.

So all said and done I'm rather curious as to what forms of heat treatment may have been applied to crucible steel blades, why, and with what result.

[Chris Evans]

Originally Posted by kisak

So all said and done I'm rather curious as to what forms of heat treatment may have been applied to crucible steel blades, why, and with what result.

Hi,

Well, as far as I can tell, this is the area about which we know the least and the key to understanding the legendary reputation of Wootz. This matter came up before: http://www.vikingsword.com/vb/showthread.php?t=3377

Cheers
Chris

[Jeff Pringle]

The answers are yes and yes!
The alloy and cooling history of the ingot determine in a fundamental way the clarity, contrast and scale of the pattern, but then it is up to the smith to manipulate the metal & influence the pattern. So only some ingots could become AA-style blades, and then only if manipulated correctly.
I did some experimenting this past spring to see how many different effects I could get out of one ingot; the first photo is the pattern that all the ingots start out with, more or less, the second is an attempt to mimic Figel’s figure 8a. They are in different states of polish and degrees of etch, so they look more different thean they are - they are from the same ingot, just forged differently.
But many ingots would not be able to look Persian, the banding can be muddy, too small, the waters choppy.