Carburizing raw iron

[Dan Zawacki]

to make blister steel for eventual crucible melting

Initial research suggests that packing the wrought iron in (enough) powdered charcoal in an airtight container, and heating for the right time and temp are all that are required.

Naturally, the carburized layer will be only the skin (thus the subsequent crucible melting), meaning surface area to volume ratio would be the natural choice of controlling the carbon uptake for the final product.

Aside from experimenting, is there a reasonable source of information that will help me predict BEFORE I fire it up what kind of surface area to volume ratio I'm going to be looking for? I am aiming for a blade worthy concentration of carbon, being somewhere (in my admittedly undereducated opinion) between .6% to 1.0%

Actually, the iron isn't wrought iron, but raw meteroric iron.

6.68% Ni,
0.43% Co,
0.25% P,

87 ppm Ga, 407 ppm Ge, 3.6 ppm Ir.

Will the cobalt and phosphorus be problematic in these quantities? I have a hard time believing the gallium, germanium and iridium would have any real effect at these concentrations, but the cobalt and phosphorus very well could!

with all of that nickel, would I be wasting my time trying to get the iron to take on carbon in such a low tech process? I know nickel can have an inhibiting effect on carbon migration, and 6.68% is a lot more nickel than I'm used to seeing in the kinds of steel I'm even a little familiar with.

I would really like to make this project work. It's something pretty special to me, but if it's not going to happen, then I may have to drop back ten and punt.


Also, as an aside, in the not too distant future, I will be making hardwood charcoal if anyone is interested in some. Once I get the (55 gallon drum) retort up and working, I'd be willing to share from time to time.

 

[Sam Salvati]

Dan, I think when carburising the wrought iron, you are going to want to pack a bunch of small peices into the carburizing can, more surface area means more area for the carbon to absorb/diffuse, which means more carbon in the final steel.

GOOD LUCK!!!!!!!!!!!!

 

[Jesus Hernandez]

to make blister steel for eventual crucible melting

Why make blister steel to later put it into a crucible?

I would make blister steel then stack up the bars and weld it into a billet. You can then fold the billet a couple times to make the carbon content more homogeneous.

Or else skip the blister steel step altogether and just do a crucible smelt.

 

[Dan Zawacki]

Well, historically, blister steel was folded to evenly distribute carbon. Once was called "shear steel" twice was "double shear steel" and so on.

The crucible method was actually invented by a watchmaker who couldn't get satisfactory springs made from the highest quality triple shear steel he could buy.

In doing a pure crucible melt, I'm not sure how I would have any controll over the amount of carbon the steel takes on. I don't want to end up with cast iron.

Sam

Of course I'll likely want a bunch of small peices in the can, but what I'm after is some sort of resource that could point me in the direction of figuring out HOW SMALL before I fire up the first shot.

I could powder grind the oron and mix it with 50 / 50 charcoal dust, but I'm fairly sure that will end up with cast iron type carbon content. Alternatively, putting one big lump of iron in will result in a very small amount of carbon int he billet overall.

Is there a resource or place where I can get reliable information on how thick the carburized skin is likely to be, and / or how much carbon by volume that skin is likely to contain?

I have been searching the net for a while and I can find enough basic information to make the process work (likely with some fidgeting and trial and error) but no quantifyable information on rate of carbon uptake.