Reference Books and pages

32t

Member
I wish the guys that named these things would use a different suffix other than ITE.................... :D
 

32t

Member
the Widmanstätten patterns Were one of the more interesting things I looked up today of for no other reason than the name
 

32t

Member
Being of northern European decent I may have a genetic tendency towards hemochromatosis?

In the future when our sun blows up I might become part of a meteorite......................
 

Victor Creazzi

King of Bondo
Finished reading Larrin's book for the second time. Funny thing is that there were sections that seemed brand new to me even though I know that I read them the first time through.

@Brono, does your experience with wootz align with pages 338-339. with regards to thermal cycling with the max temps being between A1 and Acm?
 

Bruno

Administrator
Staff member
@Brono, does your experience with wootz align with pages 338-339. with regards to thermal cycling with the max temps being between A1 and Acm?
Yes, for the compositions mentioned. There is one smelter I am having a perpetual disagreement with on the use of manganese which imo changes what is going on for the worse. But yes in general. Although there are imo at least 2 omissions from the book that I can see.

The first is about the fact that the pattern dissolves above Acm which is true. But you can make it re-appear by thermal cycling. After all the CFE (Carbide Forming Elements) are still where they were before. Some smelters including Pendray later in his career, 'roast' the ingot above Acm for 24 hours after it cooled down after the smelt. It's packed in refractory cement to keep it from scaling away. The dendritic structure after solidification is almost fractal in nature, branching out into ever finer and finer arms. suppose you forge that ingot down as-is. those very fine cementite bands will still exist next to the bigger ones. As a result, the contrast between the martensite and the bigger cementite bands will be a bit 'fuzzy'. If you heat above Acm and dissolve all the carbon, then the 'surface' where 2 iron crystals meet can release some of the tension between them. This will eliminate some of the 'fuzz'.

The second concerns the exact nature of carbide formation. So imagine what happens when a fully molten ingot solidifies. From the outside in, temperature drops until solidification starts. This is like crystals growing from a mineral suspension. Austenite starts growing and like any other crystal, it wants to be 'perfect'. It doesn't want CFE in its matrix. So at the same time as CFE starts attracting carbon and growing, the steel crystals 'push' or 'squeeze' those CFE to the space between them as they grow inwards. Yes, carbides grow in a dendritic manner because of the CFE, but that is equally due to the iron crystals growing next to each other and squeezing the carbides from both sides. It's equally correct to say that the carbides grow in a dendritic manner, as it is to say that the steel crystals grow like balloons in a confined space and squeeze everything non-balloon in the space between them. Now that covers the initial carbide formation.

The book mentions e.g Vanadium as one of the dominant CFE (my guess is that Niobium would be equally suited or even better) and while that is true, it's not the only mechanism. If you read Verhoeven's work on heat treatment, he explains how the boundaries between Iron crystals automatically act as precipitation points where the growth of cementite (or ferrite in hypo eutectoid steel) starts. He even gives an example of thermo cycled 1095 where after specific thermal cycling, you can make the cementite bands grow around the iron crystal boundaries.

So if we tie that back to our wootz, it is fairly obvious that while the CFE had a huge influence during solidification of the ingot because of their ability to grow carbides even in the transition from liquid phase to solid. But during the forging and heat treatment phase, the CFE are just one of the mechanisms that will make the carbides (re)grow where they need to be. The very fact that that is also where the crystal boundaries are, means that the carbides would grow there anyway, albeit less quickly and after more thermal cycling.
 

Bruno

Administrator
Staff member
Those are the 2 main things I see missing. Another piece of information from the book that has my curiosity piqued is the part that covers re-crystallization. I've only read through that part once and I haven't put much thinking into it yet. But given that crystal boundaries do affect cementite growth, recrystallization should have 'some' effect although it will not change where the CFE are in the matrix so I am unsure how big an effect it would be.
 

32t

Member
I was working on rereading this book when my grandson called.

Not a recipe for steel but I wrote a recipe for water pie inside the back cover because it was the clean sheet of paper handy.
 

Bruno

Administrator
Staff member
It's not a real manual if you haven't written inside it or covered it with coffee stains :)
 

Victor Creazzi

King of Bondo
I was trying to loan a female acquaintance a novel that's subject was relevant to how we knew each other and she was weirdly reluctant. I more or less insisted the she take take it and she finally agreed saying apologetically "I'll try not to get chocolate on it."
 
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