Building a coal forge - refractory?

[Gazz]

I have a large fire pot and an angle iron frame with steel plate top.  I cut a hole in the plate to set the fire pot into and will be using a steel wheel barrow tub for the hood.  My question is, should I line the fire pot with refractory cement?  Years ago in a shop I worked in, the firepot there was lined with refractory but that forge burned 10 hours a day heating stock up to 3" in diameter.  I'm not going to work it that hard.  What do you folks think?

[JHCC]

Photos would help, but probably not. 

[Irondragon Forge ClayWorks]

I lined mine with plain old fire clay 30 years ago and it's still going strong. It's in my avatar.

[Frosty]

Not refractory cement, mortar, etc. If it's hard and cemented in place thermal cycling WILL break it up. Masonry has a different coefficient of expansion than steel; steel expands and contracts more and faster than masonry. If they're glued together the steel will win because it WILL flex and masonry is as flexible as . . . Hmmm?

2-3 parts sand or crushed ceramics grog to 1 part clay makes a fine solid fuel liner. Just enough moisture it can be compacted hard and ram it in.

If you make it like mud or pottery clay and it WILL shrink check as it dries. It'll end up just like a dry mud puddle, all the cracks are "shrink checks." 

Frosty The Lucky.

[anvil]

Use castable refractory or "fire clay". Google it for location. There are many companies who make it. You buy it by temp needs. It can be found at pottery supplies as well as hardware stores and fireplace supplies. The hardware stores and fireplace supplies usually don't have the needed temps 

Do not line your firepot. Clinker can stick to it and your fire tools will trash it with normal use.

[Frosty]

Almost every sand and gravel supply that's  more than just a pit, concrete batch plants and masonry places carry fire clay. It's used in all sorts of fire structures from fire places to outdoor fire pits. Just do a web search for "Fire Clay." 

I don't know of different grades of fire clay, fire brick yes, there are several common available temp ratings.  The local concrete batch plant makes fire bricks in different shapes. They'll even use one of their many paver molds if you want to pay the price. 

Call around, it's everywhere.

Frosty The Lucky.

[Gazz]

Sorry I haven't been able to get pictures posted - I've been busy with truck repair and getting my small vegetable garden ready so the forge work got set aside.

I do have a bag of castable refractory that I used when I made the floor for my gas forge.  I also have a friend who owns a pottery studio so stuff like fire clay and grog are easy to get from her.  I do intend to put 1.25" thick fire brick around the fire pot mostly to bring the level up close to the edge of the fire pot.  Pictures will explain it all and I'll take some tomorrow.  

[Gazz]

Here is my project.  The flat area will be covered with 1.25" thick fire brick.  The hood will be removable and have hinged sides to help create better draft through the chimney.

[ThomasPowers]

How are you keeping coal from falling off the forge table?

[pnut]

Might want to put some angle iron around the perimeter of the table to keep the coal from falling off. Looks like it will be a fine forge when you're finished. 

Pnut

[Gazz]

I had planned for that and did get some flat stock to make a fence around the perimeter but haven't got to that yet.

[Gazz]

Still interested to hear thoughts on whether I should line the pot wit refractory.

[Charles R. Stevens]

Slag will stick to refractory like glue. Your cast iron pot will do fine as is.

 

[Irondragon Forge ClayWorks]

On 5/17/2021 at 7:57 AM, Gazz said:

flat stock to make a fence around the perimeter

When you make that, leave the center of both sides across from the dished out sides of the fire pot open, with a lift out section to pass long stock through. When not needed the lift out is replaced to close up the opening.

[Irondragon Forge ClayWorks]

It took me a while to find this picture of the coal forges at ESSA. The "fences" are all removable mounted with rebar welded to the fence, which goes into a piece of tubing welded to the table. You can see the pass through area and the fence portion can be put into position to keep any coal from falling off the table.

[anvil]

Like I said above and Charles said, don't put fireclay in your firepot. It's unneeded. That's why it's made out of cast iron. Clinker sticks to the fire clay. And finally normal fire control with your poker will chip it off.

[DennisCA]

I remember Joey Van Der Steeg saying to leave a layer of ash in the pot, it acts as an insulator.

[Irondragon Forge ClayWorks]

That's what I do makes easy removable of the clinker.

[Samuelc123]

Perhaps maybe lining your forge with soap stone sheets cut to fit. Soap stone is a great refractory material because it holds alot of heat in better than most ceramics but also will not break and degrade over time as fast. It'll probably take decades to degrade im not sure. I don't know much about it. But I do feel like you should crush some and add it to your mix that frosty recommended

[Frosty]

There is a serious problem using soapstone, it's the same thing as asbestos with a slightly different molecular water content. It's very soft, your stock and fire tools will be scraping dust off it constantly. The dust will be blown into your breathable air because it won't melt or stick to anything at the temps a forge fire can reach. 

It's a good thought but I think the lung hazard makes it a poor choice.

Frosty The Lucky.

[JHCC]

 

13 hours ago, Frosty said:

There is a serious problem using soapstone, it's the same thing as asbestos with a slightly different molecular water content.

Not quite. Soapstone is basically talc, and while some varieties contain asbestos, others do not. 

[Irondragon Forge ClayWorks]

Talc is still hazardous to inhale.

[Samuelc123]

On 7/10/2021 at 8:07 PM, Frosty said:

There is a serious problem using soapstone, it's the same thing as asbestos with a slightly different molecular water content. It's very soft, your stock and fire tools will be scraping dust off it constantly. The dust will be blown into your breathable air because it won't melt or stick to anything at the temps a forge fire can reach. 

True i just realized that lol, I do believe theirs a loop hole to this tho. The soapstone layer can be a secondary layer but the first layer can be something else?

[JHCC]

21 hours ago, Irondragon ForgeClay Works said:

Talc is still hazardous to inhale.

True, but whereas the OSHA standard for asbestos exposure is no more than 0.1 fibers per cubic centimeter of air (~2,830 per cubic foot), the standard for asbestos-free talc is 20 million parts per cubic foot. Hazardous, yes. As hazardous as asbestos, no.

[Frosty]

Okay, chemically, soapstone is too all over the place for my above statement to be accurate. Depending on where it's mined it may be talc, some mines produce and sell serpentines and chrysotile (known as white asbestos) as soapstone. 

Soapstone does contain silica and it's natural formation is long thin layers almost fibers. If it's really fibrous it probably contains asbestos.

As a general rule, if you can't identify which mine it's from and the lens it was mined from, treating it like it contains asbestos is NOT a mistake.

Good grief, I thought I sent this yesterday. At least it was still here so I don't have to rewrite it.

Frosty The Lucky.