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DanielC

1.3-1.4% C Crucible Steel

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do have a sense of how long your nucleation cycle actually is? its a shame about that porosity in the previous attempt, its definietly a result of long nucleation, and also the thickness, i wonder if the shape can be changed to avoid thicker castings? im sure you know a lot more about that, but from a metallurgical standpoint that short cycle crystallization is key in making a void free casting. very cool thread and interesting results. i love the glass as parting agent trick too!

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DanielC  what kind of crucibles do you use?

I really enjoy your threads, btw, especially with the images. And after following your posts, I watched a video of Pendray making and talking wootz and Damascus (he uses busted beer bottles) and actually understood what was going on and why. 

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Gwen

I dont. I would consider it slow, but not the slowest I've ever heard. I cut back the juice for about 10min andnthen fully shut down, closing all entry points and letting it cool off in the furnace. A slow cool enhances cluster sheet spacing among the dendrites, and the final pattern is partly a result to this. Too slow and yes, pockets of CO2 form and could possibly be filled with precipitated graphite which will in turn wreck a pattern and create cold shut streamers containing graphite.

Tbh, that attempt was a little different than my usual and did not incorporate a means of burning any O2 in the steel as it was liquid. I tried using CaC as an oxidizer instead, but it seems to have failed me. I feel like this is a result of that, but I could be wrong.

A good way to check later on is to use my ruler for microscopy and measure the distance between aligned bands. If they are wider than 80 or so microns then it's probably a result of too slow of a cool. There is a fix to this however, and it is employed early on.

The ingot is quite large, and there are narrow crucibles available, however the more cycles ran and the more distance forged, the better things get.

Ohio

Thats a good documentary. I also use beer bottles. Preferably green. I had to stomach Heineken over the weekend for this last run.

I use commonly sourced graphite/clay crucibles. These are #3's, but I'm thinking about stepping up to #4s

 

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Daniel

interesting that sweet spot of fast enough but slow enough is a difficult one to nail down for sure. is this anything like spherical graphite iron? do you use a % of silicon in this alloy? outside of the dendritic patterns ,what are the forging characteristics of the alloy youre making ? im asking because i dont know too much about the families of iron/steel outside of ccasting them. i only have to deal with the alloy,its flow ,shrinkage, porosity and ductility. i dont know enough about forging to know if this alloy is better or worse in its physical working properties, i do get that its look is beautiful and also probably difficult to homogenize,thanks.

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Perhaps similar. I am not sure the mechanical properties dendritic cementite are the same for graphite in needle form, but maybe. The two processes impart similar properties to the elasticity of the metal, so maybe.

With cast irons you have a very high concentration of cementite in the form of ludabrite, and if Si levels are high enough (1-3%), it doesnt allow carbon into solution and precipitates graphite needles. Depending on heating conditions these needles can be in primary cementite or not. The carbon content will also dictate this as well, as you go above 4% or roundabouts regardless of Si content.

I've always imagined graphite being pockets of porosity among the hard ceramic ludabrite, and then becoming stress risers during a cold bend, rendering a snap. I assumed this is why white cast iron is both forgeable and is more durable. These are my assumptions though as I dont dive too deeply into cast irons except during the occassions that I make them, see them in the scope and read about them in literature.

Also, this material is a little different than general steels. Imagine a sea of pearlite (or martensite if its hardened) with very hard ceramic waves (cementite). 

This material gave swords the ability to be knife hard, and not snap when bent. It also gives a lot of edge retention and stability.

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im sure youre right about graphite needles,also has terrible shear value, but do you mean ledeburite? i know that doping the iron with Si moves those graphite needles around a bit. ive seen this in castings in areas that cool slower than the rest of the casting due to thickness.

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Yep, my spelling was off unfortunately. Ledeburite.

I have quite a variety of gray cast I've made on accident that formed in different structures depending on rate if cooling.

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