How to add carbon to steel.

[jgourlay]

You have two things.

1. low carbon steel
2. A lump o' coal.

How do you get the lump o' coal into the low carbon steel to make high carbon steel?

[Rich Hale]

Actually there is another solution to this problem, which I will get to later in this post.
For a long time I have heard of the old smiths that could increase the amount of carbon in a bar of steel with hammer and forge and coal...And have also heard of charcoal being used. Now I supose there are couple of questions that we need to find answers for. One you can do as some claim, sprinkle a bit of coal or charcoal dust on the anvil and pound the hot bar onto/into it and after a few rouinds of this you could spark test the piece and compare it to a piece of the same stock you kept as a test sample. You could also forge weld a piece of high carbon steel to the low carbon and cut stack and reweld it until you get enough layers. .
If you wonder why a smith would go to the trouble of all of this work to get a higher carbon steel it is simple. They did not have the resources then as we have now.
Here is the other solution,,,buy some high carbon steel or recycle some..get what you want and make what you wish from it. Enjoy

[oakwoodforge]

To answer your question: Time, Temp and air ( O2 control ) ... Carburizing mild steel or iron takes lots of time and fuel and is not easily, predictibly or econimicly done in small batches without LOTS of practice. If you need High carbon steel why use $100.00 worth of Coal/charcoal to get $5.00 worth of marginal quality semi-carbon steel with unknown properties? If you can't get any High carbon steel localy try ordering from some place like Clark and Osborne, A 3 foot long peice of 1/2 inch diameter O-1 High carbon steel will cost only about $6.35
ToolAndDie.com - The Toolmakers Marketplace: Oilcrat (O1) Drill Rod 3 feet Long
Hope this helps

Jens

[bruce wilcock]

change your low carbon steel ,for wrought iron and you will easily steel it up in a coal forge by working it at full welding heat folding and refining it driving out the slag and caburising it ,if you throw some casenit in the fire you will land up with a type of blister steel, if you fold that in ,or get some silver steel and have a easy life

[ThomasPowers]

Unless you are careful you are more likely to lose your carbon layer to scale than to increase the carbon content of the piece while forging it.

Also coal has sulfur in it something you *DON'T* want in any steel you make.

In general the old way was to enclose it in a refractory container with carbon compounds---charcoal, leather, horn scrapings, etc and heat as hot and as long as possible.

Theophilus mentions this in a book he wrote in 1120 AD, "Divers Arts", when he mentions greasing a file and wrapping it in leather and then encasing it in a good clay and then heating till it's red.

nb: coal was not used by blacksmiths till the high to late middle ages and charcoal was still the preferred fuel for much longer. (see Abraham Darby and his work to commercially smelt iron using coal instead of charcoal in the 1700's!)

You can also use "natural steels" naturally high carbon blooms from your bloomery.

And for an off the wall method the UN book on blacksmithing tells hoy you can use cast iron as a hardfacing compound for mild steel, heating both pieces and "crayonning the cast iron onto the steel".


Thomas

[bruce wilcock]

yes you are right you have to be verry carefull to get the blister folded in without it crumbling and loosing it. Have you had a try at putting a wash of cast iron on steel ,i have found that when working with a cupula all the lances and pokers have a coat of iron thats has hard as flint, though i never thought of using it as a wear resistant tool, can you find out more about rubbing a cast wash onto steel,its worth giving it a try .

[Ferrous Beuler]

Man I love this forum... so much good stuff here. My question is how does one add carbon to something BIG, like say, a buggy axle. Lots of wisdom from oakwoodforge but even today, as in days of yore a smith is likely to use something from the heap first rather than seek a specific piece new and take it from there. Once I watched a man named Herschel House "add carbon" to some small pieces he had just forged, gun parts, a flint hammer and a frizzen. These were small bits of iron which he placed in a crucible of about cup size with some hardwood charcoal from his forge and steeped it in his fire. At this point he mentioned what Thomas cited, horn or leather could be used here as all organic matter is carbon based. He made it all look so simple and I don't doubt his work as many a backwoods smith did just this for many a rifle. Could this be done on a larger scale, such as for a long rod like a buggy axle or anything else of that size. Some of us LIKE doing things the hard way for the sake of nostalgia. Dan:)

[Rich Waugh]

Nope, the idea is to keep the carbon in and oxygen out, but creating pressure isn't necessary. Something combustible (the carbonaceous material)in there burns up any oxygen that might creep in.

[Rich Waugh]

Nope, it doesn't have to be sealed super tight; you're not trying to move the carbon into the steel by creating pressure. The carbonaceous material in there will burn up any stray oxygen that creeps in.

[Woody]

Ferrous:

what you are describing is "Case Hardening" it does impart some additional carbon to the metal part, but the depth of penetration is only a few thousandths of an inch. You can check Richardson's Practical Blacksmithing, I believe it has several pages on the process. If you had a forge big enough to handle a buggy axle, you could case harden it, but the results would be the same, an axle with a hard layer that is only a few thousandths of an inch thick. Rather than an exercise in nostalga, I fear it would be an exercise in futility.

Woody

[ThomasPowers]

At Quad-State a couple of years ago Ric Furrer demonstrated 3 ways of making steel; One was melting in a crucible, one was making blister steel and one was in a charcaol forge making orishnaghane (sp).

For making blister steel they used to put 1" steel bars in refractory boxes with carbon compounds and heat to red for a week to 10 days---this may be repeated! (even at the time of the ACW steel could be 5 times the cost of iron).

The resulting blister steel could be used as is or cut-stacked-welded to make shear steel that was a bit more homogenious and that repeaded for double shear steel---so you could have double blistered double shear steel if you were really picky.

The "o" method was to take small bits of wrought iron (rivets, nails---small cross section stuff) and put them in the charcoal forge and heat them for an hour or more to soak in carbon. You then weld up the scraps into a solid piece of steel.

How an old times smith would do a buggy axle? Weld some steel on the ends and forget the rest that doesn't need it!. He could do this by welding a steel piece on the ends or wrapping the ends with a steel "sheet". Since they used to weld up the drive shafts for ship engines they were able to get good enough welds for a buggy axle...

A source of info would be "Steel Making Before Bessemer, vol 1 Blister Steel, vol 2 Crucible Steel" (need to check that title when I get home)

Also "Mechanics Exercises" by Joseph Moxon discusses the various wrought iron available around 1700 and what each was good for.

"Practical Blacksmithing", Richardson, has a lot of info from the late 19th century when the switch from real wrought iron to Bessemer steel was taking place in the smithy. It's a collection of articles from a Blacksmithing Journal of the time.

Thomas

[jgourlay]

Great information all, and thanks. Here is the reason I ask. I work with several chemists and several metallurgists.

I posed this as a simple question to many of them. At first they gave the flippant answer of, "you just add carbon to molten iron" with "stupid" being the subtext.

So then I started asking things like, "well, at that temperature, how do you keep the carbon from simply burning off as C02?" and "with such different densities, won't the carbon just sit on top of the iron?" and "will the iron wet the carbon?"

That just got gaped mouth stares and stumped expressions. So, I thought I'd throw it up here....and sure enough get better answers. Not that I plan on doing this, it's just monkey curiosity.

[Jeff Mack]

For making blister steel they used to put 1" steel bars in refractory boxes with carbon compounds and heat to red for a week to 10 days---this may be repeated! (even at the time of the ACW steel could be 5 times the cost of iron).

Thomas,

Does the box need to be truly sealed, or just real close. I'm paranoid about butting anything sealed in a forge. A little moisture could ruin my day.

Thanks!
Jeff

[ThomasPowers]

Their idea of sealing was to lute the seam in the box with clay---a fairly porous non pressure seal. The idea is to keep the C0 *in* the box in content with the metal and away from the possibly contaminated (sulfur) combustion gasses.

I remeber a mosaic damascus demo at Quad-State where that very question came up. The demonstrator had mad a Ni form and put it in a piece of square tubing and filled around it with shot blasting medium and had the helper go weld the top on (after a shot of WD40). Turns out that the helper was better with the arc welder than the demonstrator was and while the box was heating it "popped". No excitement though.

Thomas

[FredW]

Interesting post. I am going to try the box method of making a steel billet (for knives). I have some high nickel iron powder and graphite. My plan was to weld up the billet inside a mild steel case with a mixture of the powder graphite and some pieces of high carbon steel (shavings probably). Now I think when I weld it i will leave some of the seam unwelded.

You could also add carbon, if you wanted to melt the steel, is add graphite, charcoal, coal, etc. to the charge then through charcoal on top. A fairly thick layer to keep out the O2. The ashes will help to seal it theoretically. I guess you could even use glass on top.

Fred

[oakwoodforge]

Very thorough article on Ancient carburisation of iron to steel:
Ancient carburisation of iron to steel: a comment
A bit dry perhaps but an interesting read none the less.

[Sam Salvati]

JPH does case hardening, it was a really interesting process to talk wiht him about it. I never even heard the word plumbago before.

[rfraser]

This could be a really dumb question. I was watching tv and seen that they can make diamonds from the carbon from human hair. This is done at high heat and pressure. My question is: Has anyone tried to add carbon to mild steel using human or pet hair? If not, could someone try this and let me know if it works?

Best Regards
Randy

[Randy]

I have found, and use this often, that if I want more carbon in an end of a bar, I simply heat it in the coal forge to a welding heat. I take the heat up slow and make sure it's a good thorough welding heat, but don't burn it, and that's it. I show this in my tool making classes and I do it in wrought iron and mild steel. Spark test it first, heat it and then spark test again and you'll see how much carbon is added. It's also a very deep penetration of carbon, not just on the surface.

[ThomasPowers]

RFraser; not much difference than using cow horn scrapings that I mentioned several years earlier... keratin is keratin and in the box carbon is carbon...

[thingmaker3]

I have found, and use this often, that if I want more carbon in an end of a bar, I simply heat it in the coal forge to a welding heat.
...
It's also a very deep penetration of carbon, not just on the surface.

The "secret" here is the very high temperature. Rate of carbon diffusion into (or out of) steel is proportional to the square of the Kelvin temperature. A 16 percent increase in temperature (from 1700F to 2000 F)gives almost 36 percent increase in diffusion rate.

[rfraser]

Thanks Guys

That just sounded like it would work.

I will have to give it a try as soon as I get set up. I have no experiance in this art. I just got my anvil this summer and the only thing I made was a set of skidding tongs in the fire pit using a piece of pipe and my wifes hair blower.

I only read one book (New edge of the anvil) about 2 years ago and forgot most of what I read.

I made a small mini forge for hardening and tempering some woodworking tools. Worked OK but not good engough for large pieces. Thats it. Can't wait to get started.

Thanks again. Randy

[Jeff Seelye]

You have two things.
1. low carbon steel
2. A lump o' coal.
How do you get the lump o' coal into the low carbon steel to make high carbon steel?

Well, you can and you can't. If you want a bar of high carbon steel that is hi carb all the way thru then buy it. If you want to add carbon, you can, but only on the surface, this is called Carburizing. Steel is made up of atoms of iron and carbon that hook together. When you heat it, the atoms of iron vibrate faster and move further apart. When this happens, carbon can be added (around 1800 degrees F). I use Barium Coke in a box. This process takes time, (4 to 8 hours) and you are only getting around 40 thousandths depth (.040) of carbon. There are many ways to add carbon, this is only one. I only use this when someone brings me a frizzen that doesn't give the spark they want. Carburizing is also good for shafts that have a tough core and a hard surface.

[thingmaker3]

The added carbon is not "just at the surface." It is, however, more concentrated at the surface. "Case depth" is usually the depth where a quenched part will be 50% martensite. (This measure is easy for the QA folk to test with an etch.)

Diffusion rate of carbon in steel is proportional to the difference in carbon levels. So a low-carbon piece in a carbon rich atmosphere will carburize at a higher rate than a medium-carbon piece. A high-carbon piece in a carbon free atmosphere will decarburize at a higher rate than a medium-carbon piece.

As noted earlier, temperature plays a geometric role.

The diffusion rate is a rate, so more time means more difference. Of course the rate changes over time because concentrations change over time.

[Jbiasca]

Would it be possible to make high carbon steel by case hardening some mild steel, folding it a few times and repeating the process a couple times?  Would the higher carbon content on the surface by mixed in by folding?