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Author Topic: Discussion of Metallurgy for Bladesmiths by John Verhoeven  (Read 17736 times)
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ChrisAnders
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« on: January 12, 2015, 07:35:11 PM »

As promised, here is the discussion thread on Verhoeven's book for bladesmiths.  Copies are available in the edge thickness before quenching thread.  Anybody got anything to discuss?     

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mreich
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« Reply #1 on: January 12, 2015, 09:11:37 PM »

Nice work, Chris. Thank you!

I'll definitely be here in the morning. Just tired.

« Last Edit: January 12, 2015, 09:21:38 PM by mreich » Logged
Ed Fowler
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« Reply #2 on: January 14, 2015, 09:23:51 AM »

I do not see a link?
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Daniel Rohde (D-Vision)
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« Reply #3 on: January 14, 2015, 09:37:35 AM »

Here you go Ed: http://www.feine-klingen.de/PDFs/verhoeven.pdf

I have been reading this quite a bit lately...
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mreich
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« Reply #4 on: January 14, 2015, 09:38:41 AM »

I'm sorry that I'm so tied up right now. I had an emergency call to take over a construction project, and it's really messing things up. I've got 7 orders for knives that I have to get done right now too.

I am truly looking forward to this discussion, but I'll have to settle for following along right now.

I read the first couple chapters, and I only remember a couple things that I wasn't clear on.
« Last Edit: January 14, 2015, 09:42:18 AM by mreich » Logged
John Silveira
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« Reply #5 on: January 14, 2015, 09:30:55 PM »

i haven't read a thing - just can't sit down to do it at the moment .

Question: i understand that Carbon will move inside the grain boundary . HOW MUCH carbon can go inside the boundary? Are all boundaries the same size ? Can multiple ( carbon ) bits (for lack of understanding ) fit inside the boundaries.

Question: So if the steel is brought up to the temp where carbon moves around would holding it at that temp for a bit allow more carbon to find boundaries to live in ?

Question: Perhaps bringing the steel up to non-mag so carbon moves into boundaries then does it make sense to heat and cool the steel many times to facilitate getting as much carbon into the boundaries as possible ?

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ChrisAnders
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« Reply #6 on: January 15, 2015, 05:51:42 AM »

Its helpful to keep in mind that carbon is a much smaller atom than iron is.  Carbon will fit between the iron atoms pretty much anywhere, inside the grains as well as at the grain boundaries.  How much carbon will fit between the iron atoms, or how much carbon is dissolved in the iron, depends on how much carbon you have (steel composition), and what temperature the steel is.  Hotter steel dissolves more carbon, just like hotter water dissolves more salt or sugar.

Yes, holding the steel at a certain temperature for a while will allow more carbon to dissolve, but there is a maximum amount, which is dependent on composition and temperature.

Yes, heating the steel and quenching it more than once will allow more carbon to be dissolved with each cycle, as long as the maximum is not exceeded on the previous cycles.  Also, slow cooling after heating will not do it.  If the steel is slow cooled, the carbon dissolved when the steel was heated will just undissolve on cooling if it is given time.  That is not to say there is nothing happening during slow cooling, its just the carbon won't stay dissolved during slow cooling.
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Ed Fowler
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« Reply #7 on: January 15, 2015, 10:36:26 AM »

The quality of heat treat can be evaluated by the amount of iron in the grain boundaries. The more iron the poorer the heat treat (in the same steel).  Iron in the grain boundaries is indicative of taking short cuts in the heat treat.
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ChrisAnders
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« Reply #8 on: January 15, 2015, 11:13:23 AM »

I'm not quite sure what you mean by iron in the grain boundaries.  Can you elaborate on this a little more?  There are also chapters in the book that deal specifically with grains, boundaries and how they move.  They are later in the book I think chapter six seven or eight.
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Ed Fowler
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« Reply #9 on: January 15, 2015, 05:27:24 PM »

I will let Rex explain it when he has time to join us. It should be explained in the book you are reading.
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ChrisAnders
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« Reply #10 on: January 15, 2015, 05:37:51 PM »

You can't drop a cliff hanger like that and let it hang there.  I have not read the Verhoeven book word for word, but I don't remember anything like that.
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John Silveira
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« Reply #11 on: January 15, 2015, 09:30:24 PM »

i could use a little clarification on what Boundary is in the first place.

I understand the iron/carbon for starters and then a host of alloys to comprise up steel but "Boundaries"!
Can grain boundaries be different sizes ( seems surely so ).

I've seen the diagrams showing the grain size and it's boundaries and how it expands with heat and carbon goes into it then cooled the grain gets smaller again but looking specifically at the boundary of an individual grain - what part of the steel matrix is that specific boundary ? Iron? sand? toilet paper - what the hell is it ?

Once i can understand basic boundary and whether or not JUST carbon can go into the boundary then i'll move on to getting a better understanding of where all the other alloys are within a given piece of steel like what we use for making knives.

I have to start somewhere .
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ChrisAnders
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« Reply #12 on: January 16, 2015, 05:58:41 AM »

To understand grain boundaries, it helps to start with pure iron.  No alloys, no carbon, just iron.  The most basic definition of a grain boundary is just the line that separates 2 grains.  Take 2 balls of clay and stick them together, but don't knead them.  The line that shows where the 2 clay balls used to be separated is similar to a grain boundary.

In more technical terms, it is not part of the steel matrix, but a border.  It is the line that separates the ordered matrix in one grain from the ordered matrix in the next grain. 

Remember that iron atoms stack themselves into cubes, and many many cubes stacked onto each other make a grain.  The next grain is also many many cubes, but it likely doesn't line up with the cubes in the first grain.  Now, in solid iron, these two grains are stuck together.  The grain boundary is the line that is the border between the cubes lined up in one way in the first grain and the cubes lined up in another way in the second grain. 
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John Silveira
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« Reply #13 on: January 16, 2015, 10:12:27 AM »

Ok - thanks for that explanation - brings me closer to the truth it seems.

What i didn't realize is the stacking of the iron that actually comprises a single grain !

Speaking of that ( a single grain ) - that's where my attention is at the moment -

suppose you do away with two grains that are joined together and think of ONE grain. Apparently they're cubical in dimensions , but the ONE grain must have a perimeter , such as a wall all the way around it ( i think of it as a boundary ) THEN when you bring that ONE grain into contact with another grain and they join that also becomes a type of boundary. 

i just want to be clear that one grain can be looked at as like a house for example , with it's own walls ?

thnx
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ChrisAnders
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« Reply #14 on: January 16, 2015, 11:13:15 AM »

Yes, good analogy with the house.  For a grain, think of one room.  The grain boundary is like the wall between rooms.  It is a divider and is shared by both rooms.  You can also think of rock candy.  The individual crystals are grains, and the faces where the crystals meet are the grain boundaries. 

As to the single grain, this might make it clearer.  The grains won't look like cubes because the little iron atom cube stacks are MUCH smaller, generally, than a single grain.  Think of Legos, all the same size.  The individual blocks are the little individual cubes formed by the iron atoms stacking.  Then build something like a "ball" out of the Legos.  It not really round, but close.  Then look at it from far away.  It looks smoother and more round the further you get.  Also, the little iron atom cubes don't have boundaries between them like the Legos do.  There isn't a divider between the little cubes. 
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