puddling furnace

[connor bachmann]

Hey, has anybody tried building and using a puddling furnace?


I'm thinking of building one out of brick and use it to burn mild steel into wrought iron blooms, any suggestions?

[ThomasPowers]

Puddling turns cast iron into wrought iron. Mild steel won't work. Instead if that's what you want to do read up on the Byers process where they made wrought iron from molten slag and bessemer steel;

"Wrought Iron; Its Manufacture, Characteristics and Applications"
Aston, James and Edward B. Storey


Have you ever thought of running a bloomery and going from iron ore to wrought iron? (I was part of a bloomery crew for a decade).

[MattBower]

I think you might be better-off remelting your mild steel in something like a bloomery. I think that could work -- though what I know of the subject is purely theoretical -- and I suspect it'd be much simpler than trying to build a puddling furnace. (Producing steel melting temps in a reverberatory furnace doesn't sound easy.) Lee Sauder and Skip Williams say that their bloomery smelts produce cast iron, which is then (they think) decarburized to low carbon iron by the slag bath. If that's true, then I would think you might be able to get a similar result simply by melting steel under similar conditions, and into a similar slag bath.

You might try emailing Skip or Lee. See here: http://iron.wlu.edu/

[connor bachmann]

yes, I have run a bloomery on a few occasions. I'd just like to cheaply and effectively produce wrought iron from scraps that I have in a bucket in my shop.

Charcoal's too expensive, and time consuming to make if I want to smelt AND forge.


Anyways, I had the idea of using my coal forge with a brick construction set up to focus the flame on the mild steel, melting it, then mixing in some iron oxide, which burns all the carbon out, and stirring. Finally I would (hopefully) have a bloom. Could this work? or would cast iron be the only method?

[fciron]

Define "cheaply and effectively" lol

You'll want a sand bottom or an iron oxide and ore bottom for your 'puddle'. That's where the slag comes from. You'll have to use charcoal or coke to avoid the impurities in coal.

Look for a copy of "Wrought Iron: It's Manufacture, Characteristics and Applications" from the AM Byers Co. It's got some decent descriptions of various processes and furnaces. Nice pictures too.

[thingmaker3]

yes, I have run a bloomery on a few occasions. I'd just like to cheaply and effectively produce wrought iron from scraps that I have in a bucket in my shop.

Charcoal's too expensive, and time consuming to make if I want to smelt AND forge.


Anyways, I had the idea of using my coal forge with a brick construction set up to focus the flame on the mild steel, melting it, then mixing in some iron oxide, which burns all the carbon out, and stirring. Finally I would (hopefully) have a bloom. Could this work? or would cast iron be the only method?

What is the plan for including ferrosilicate slag?

[connor bachmann]

Define "cheaply and effectively" lol

You'll want a sand bottom or an iron oxide and ore bottom for your 'puddle'. That's where the slag comes from. You'll have to use charcoal or coke to avoid the impurities in coal.

Look for a copy of "Wrought Iron: It's Manufacture, Characteristics and Applications" from the AM Byers Co. It's got some decent descriptions of various processes and furnaces. Nice pictures too.

the plan was to use either sand or clay. Oxide, I assumed, was added after the iron was melted, was I wrong?

[MattBower]

I don't think it will work, or at least not more cheaply and efficiently than other alternatives, but this is one of those situations where I doubt any of us has actually tried it. So if you really want to know for sure, you should probably just do it.

Coal was the primary fuel for puddling furnaces for a long time. The reverberatory nature of the furnace keeps the sulfur from contaminating the iron (too much, anyway). You wouldn't have to use charcoal.

[Dragons lair]

If I may guys, i do NOT want to know what ya think or what ya were told. If ya havent done it and have all your fingers. SHUT UP. I get guys all the time who know welding tell me how to do it. have ya done it? NO (Iwas told)
Here is the torch and the GAS tank. GO ahead I'll be back to bury ya. If you have done it and survived it MAY be viable. If not PLEASE keep the advice to yourselvs. Yeh I do things I shouldn't But I woun't tell ya to do um.
When a sportster tank goes 20+ ft in the air on a 2-3 inch columb of fire it makes ya think twice about doing it again.
Ken.

[Nakedanvil - Grant Sarver]

If I may guys, i do NOT want to know what ya think or what ya were told. If ya havent done it and have all your fingers. SHUT UP. I get guys all the time who know welding tell me how to do it. have ya done it? NO (Iwas told)
Here is the torch and the GAS tank. GO ahead I'll be back to bury ya. If you have done it and survived it MAY be viable. If not PLEASE keep the advice to yourselvs. Yeh I do things I shouldn't But I woun't tell ya to do um.
When a sportster tank goes 20+ ft in the air on a 2-3 inch columb of fire it makes ya think twice about doing it again.
Ken.

Are you on drugs?

[ironsmith]

hehe, thats a good question Grant !:blink:

[ironstein]

Wow. That reminded me of a Hunter S. Thompson rant!

[gazilla]

Some guys in France do a "grappage" to make tool steel out of mild: load small scrap in a fire with abundant charcoal, where it forms something like a bloom, that nees to be consolidated and refined to make decent steel. The same method was described by Evenstad in his treatise on iron production and was used by Japanese blacksmiths to make higher carbon steel out of lower grades.
Evenstad also described a way of improving the "raw" iron produced in a first reduction step. You might try something similar, adding small scrap like nails, together with silicium, aluminium and iron oxides to a more oxidizing charcoal fire, in order to get a decarburized iron with oxides that have a low melting point (important if you want to actually forge this iron). Lee Saunders and Skip Williams (see Matt Bower's link) might be able to give you more information on this, they helped us a lot before we did our first bloomery experiment.
What are you planning to do with the blooms you'll hopefully make?

[connor bachmann]

well, I'm thinking of making the blooms into wrought iron bar stock and making decorative work out of it. If people are going to be calling my work "wrought iron", I might as well use it so that they're correct for once.


Also, I love working with wrought (at least when it has a constantly low carbon content), it's like butter

[MattBower]

How many customers do you have who'd be willing to pay for real, homemade wrought? This is not a trivial thing you're talking about. Even if you do get it to work, and work well, there's going to be a lot of labor involved and you'd have to charge a significant premium on your work to break even. I mean, I think the reason no one is supplying new wrought on a commercial basis anymore is because not many people are willing to pay for it. Of course if you want to do it just for the experience, that's great. But if you want it to make economic sense, buying antique wrought may very well be the smarter way to go.

[connor bachmann]

How many customers do you have who'd be willing to pay for real, homemade wrought? This is not a trivial thing you're talking about. Even if you do get it to work, and work well, there's going to be a lot of labor involved and you'd have to charge a significant premium on your work to break even. I mean, I think the reason no one is supplying new wrought on a commercial basis anymore is because not many people are willing to pay for it. Of course if you want to do it just for the experience, that's great. But if you want it to make economic sense, buying antique wrought may very well be the smarter way to go.

this could be implemented on a larger scale, and could possibly be cheaper than recycling scraps of wrought, it would be recycling scraps of extremely cheap steel.

That is, if it works of course.

I don't plan on doing that any time soon, I just want to make some wrought iron for artwork.

[maddog]

I agree with Matt. It would be a great project but I don't see it being economicaly viable. About 15 years ago (time is vague to me) there was a company producing Pure Iron. This was very soft iron with a very low carbon content and unlike wrought, no silica. I am not sure where it was manufactured, US or Europe but an industrial steel maker was involved. This was not a back yard operation. In it's heyday it sold for a little over $1/lb. Everybody extolled its virtues. It's ductility, resistance to cracking, ease of working, ease of welding without burning etc. Some even argued that if you took into account all the labor and wastage of material you saved by using PI, it more than covered the additional cost of the material. At the time, the product was widely known among the US smithing community and there was quite a bit of enthusiasm for it. Yet after a few years, the makers went out of business.

[connor bachmann]

economic viability is irrelevant to the topic, I'm just wondering about the process itself

[fciron]

the plan was to use either sand or clay. Oxide, I assumed, was added after the iron was melted, was I wrong?

OK, I'm checking through the book again, looking to answer specific questions. It does appear that coal fired reverberatory furnaces were used. I am still not convinced that a box on top of a coal forge will be sufficient to burn off all the coal crud. In 'dry' puddling (in a furnace with a sand bottom and no oxide addded) about 30 percent of the charge was lost. In 'wet' puddling, with an iron oxide and ore bottom and oxide added to the molten metal (like you plan to do) the loss was reduced to 10 percent.

It sounds like a huge pain in the patootie to me. Have fun and take pictures.

The book I referred to is by the last company producing WI commercially in the US. They used a different (not puddling) process of melting cast iron; adding oxide to create something close to pure iron; then pouring it over molten slag, which was cooler than the melting point of the iron; the iron would solidify in the molten slag, but as a 'Sponge Ball' rather than an ingot, so it could be drawn out into WI.

http://www.alibris.com/search/books/qwork/7325957/used/Wrought%20iron,%20its%20manufacture,%20characteristics%20and%20applications

[John B]

I agree with Matt. It would be a great project but I don't see it being economicaly viable. About 15 years ago (time is vague to me) there was a company producing Pure Iron. This was very soft iron with a very low carbon content and unlike wrought, no silica. I am not sure where it was manufactured, US or Europe but an industrial steel maker was involved. This was not a back yard operation. In it's heyday it sold for a little over $1/lb. Everybody extolled its virtues. It's ductility, resistance to cracking, ease of working, ease of welding without burning etc. Some even argued that if you took into account all the labor and wastage of material you saved by using PI, it more than covered the additional cost of the material. At the time, the product was widely known among the US smithing community and there was quite a bit of enthusiasm for it. Yet after a few years, the makers went out of business.

Posted about Pure Iron on this site in November in Everything else section, should be here for those who missed it.

[ThomasPowers]

Ahh if you re-read that book it says they took a good grade of bessemer steel and added it to the slag and then worked it hydraulically to mix it up.

They did not use cast iron and add iron oxide to it.

(I've got 3 copies of the Byers' book and have given several more away over the years to people interested in historical wrought iron).

Sulfur makes steel work very poorly, makes it hot short and NOT something we want to smith with. Most of the early methods of using coal for puddling are very much large scale industrial with a lot of time spent getting the system up to temp and a LOT of energy "wasted". If you really wanted to try messing around on a small scale perhaps an induction furnace would make for fast small batches to play with?

ObSafety: don't forget that the PPE to work *molten* steel is much more extensive than that for forging!

I've been able to find real wrought iron as scrap or free much faster than I have used it and a heck of a lot faster than I can smelt it---I plan a bloomery run in January once the college kids get back to help...

[connor bachmann]

thanks for the advice, I know this is probably not profitable, but possibly much easier and predictable than the bloomery process.

I'll try it out with various different charges, building materials, designs, etc when I get back from my vaccation

[MattBower]

Just remember that if you get this to this work you're going to have molten steel at some point. As a wise man (I believe it was Thomas!) once said, hot metal will burn you; molten metal will chase you down the hall and burn everything. So have a very solid plan for keeping it contained. And don't dare even think about sticking anything in molten metal that hasn't first been heated above the boiling point of water. When water flashes to steam it wants to occupy about 1500 times its previous volume. If it happens to be underneath molten metal at the time -- boom. Ouch!

[fciron]

thanks for the advice, I know this is probably not profitable, but possibly much easier and predictable than the bloomery process.

I'll try it out with various different charges, building materials, designs, etc when I get back from my vaccation

Actually, I suspect that the bloomery process is easier for a small operation. No idea about predictability.

Like I said, you do it and take pictures. :P

[Nakedanvil - Grant Sarver]

Never seen any indication that puddling can be done with steel scrap. Very much easier to melt cast iron. No reason you can't build a reverbatory furnace that is propane fired. For small scale production, the direct process might be better. Or look at the Lancashire process.