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I Forge Iron

Coal forges and adding carbon to material


Cethial

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Hi IFI

I work as a machinist and at work I often talk to my colleague about forging, he gave me some material to try forging at home. I went home to forge it and for the first hour it was alright to hammer the material, but after 4 hours of hammering I started getting nowhere. I asked him back at work what kind kind of material he gave me and he said it was special tool steel. I complained for a while as I barely could hammer it. He then said that since I'm using a coal forge, I'm passively increasing the carbon content in the steel. I was aware of this, but I didn't think it would be by such a huge amount.

my question is does anyone have an estimate on how much it matters? And how much carbon is added to the steel?

Best regards

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I think what zone of the fire the stock was in would play a big part. Carbeurizing metal in the forge requires a reducing flame. Someone with more experience can probably expand on this but I have a feeling it would be a negligible amount of carbon being added to the stock without it being packed in a container with carbon material and being heated to critical temp without much oxygen being present. I'm sure someone will be along shortly to explain it better and correct anything I've gotten incorrect. My inexperienced instinct says after four hours it may be decarbeurizing the steel but I've been wrong before and will be wrong many more times to come.

Pnut

Edited by pnut
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Thanks for the quick response, honestly I barely have any experience. I'm having a tough time finding good material here in Denmark, which is why my colleague told me to bring the tool home and try it. It might as well be the material the tool is made out of that is hard xxxxxxxl. Otherwise I might do something horribly wrong when I'm forging

 

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I'm not sure of the European designations but A-36 or 1018 is good for decorative forgings and cars have lots of useful parts to salvage for tools,blades, and axes etc.  I too don't have a lot of experience. I just started smithing maybe six months ago but feel like I've learned a lot in that time. Clay or plasticine moves just like hot steel so it's a good way to figure out order of operations and such. There's plenty of info on this site when you have time get comfortable and start reading. I learned a lot from IFI and it's members. Try to find books too and more importantly if there's a blacksmithing group near you join it you'll learn much faster in person than by trying to figure it out on your own.

Pnut

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Mr. pnut has already expressed what is likely going on. 

In simple terms, carburization (or decarburizarion) occurs through diffusion into (or out of) the steel. The primary things which control diffusion speed and direction are:

1) Carbon concentration in the atmosphere (i.e., your forge fireball) versus in your steel. The difference in the concentrations (which will really be more of a gradient within the steel) creates a driving force for diffusion (you can perhaps think of this driving force like a voltage, with the carbon "being" electrons). 

2) Temperature -- diffusion is much faster at high temperatures (You can think of this like reducing the resistance in an electric circuit, and carbon "being" the electrons). 

3) Material phase/structure -- carbon will diffuse at different speeds in Austenite versus ferrite, for example. 

This link explains how these different factors work reasonably well:

https://www.tf.uni-kiel.de/matwis/amat/iss/kap_5/illustr/s5_2_3d.html

 

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Welcome aboard Cethial, glad to have you. 

The carbon you MIGHT increase your stock by in a coal fire, forging, is insignificant. You're forging mystery steel without the knowledge of experience to evaluate it. To use an extreme metaphor, this is like putting a student driver in a Formula 1 race car, you are just NOT equipped to deal with the material. Seriously, it may not even be forgable steel, even if it is the tool holder you show in the picture. 

Your best bet learning is to start with the fewest variables as possible. I start folk with mild steel and simple processes. A: straight even taper, finial scroll, spreading draw, smooth uniform bend, counter punch, hole punch, HARD wire brushing and wax finish. None of these processes are difficult in themselves and combined they make an attractive or really weird, coat hook. Depending on how quickly a person is picking things up I might add a decorative twist to the hook's shank. This can complicate things and can be a challenge so I hold it in reserve.

Anyway, that's my advice to ANYBODY learning any new craft, forget acquiring tools and equipment, just get the basics, Acquire skills one step at a time. Combine the basic steps to make your products. 

Frosty The Lucky.

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Thank you all for the good advice. I did start out with mild steel. I've been lurking around the forums for a few months now.  Although I got to admit I have far more reading to do. I guess I should wait with my mystery steel and gather more information.

Thank you all.

Cethial

 

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Generally beginners decarburize their metal through scale losses rather than carburize them. They scale off faster than carbon can diffuse into the metal.

"The Cementation of Iron and Steel" has way more information on carburization that normal folks want to know including a lot of odd ball experiments---carburization without the presence of CO for instance or the use of diamonds as carbon donors...

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On a related note...

Not long ago, I took my family to a public event where re-enactors demonstrate to and educate visitors (with a high admission ticket price).

We watched a 1/2 hour blacksmith show where the demonstrator, several times, told everyone that the gray stuff coming off of the hot metal is excess carbon that the fire (gas forge) imparts onto the steel (rebar).

This was just one of many untruths that he passed out.

My head nearly exploded as I watched the young teen boys in the front row hang on every word that this dimwit spewed.

One should educate themselves before they attempt to educate others.

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