Charcoal Welding

[Arbalist]

Thanks very much for that Frosty, I can certainly get to 3 or 4 Travis Perkins stores so one of them should have it. Much appreciated.

Vic.

[John Martin]

As someone else said before. I bought briquettes to test it against lump charcoal. I wrecked four pieces of stock, couldn't weld, couldn't even get it above yellow heat. ALL in ALL I WAS MAD.

[Frosty]

You're very welcome Vic.

I hope they still carry it. From the posts I was reading in the short search I did it sounded like fewer and fewer places were carrying it at all. I think I'd be on the phone till I got a firm positive before I did any driving.

Frosty

[FredW]

I have lined my forge with fire clay, 35 mesh Hawthorn bond, and did not like it at all. It works but doesn't seem to last and it shrunk a lot. I went ahead and bought allumina (Mizzou) and love it. It,s a lot more expensive but worth it. I got Mizzou for the floor of my gasser because it takes flux a lot better and found that it does not shrink much at all.
FYI on charcoal briquettes, when watching one of my favorite T.V. shows (How Its Made) they showed how the briquettes are made. This manufacturer did not use a binder, the pressure from forming the briquettes was all it needed and it had 2 ingredients, charcoal dust and anthricite coal dust. Aint them burgers tasty?

Fred

[Frosty]

No, no anthricite in briquettes, FDA doesn't allow known carcinogens except maybe tobacco. The only binders are cellulose, primarily wheat starch.

I saw the How It's Made episode and don't recall that particular mistake. How It's Made is loaded with glaringly sloppy mistakes like the time they said, with great authority, the farrier uses LEAD nails to attach horse shoes. Did they even TALK to the guy? I don't watch the show anymore, WAY too sloppy on their facts.

To prevent shrink checking when using clays you need to mix them with sand and grog and as little water as possible. At the correct moisture should resemble properly tempered green sand for casting. Squeezed HARD in your hand it should form a lump that breaks cleanly and leaves your hand clean. If it crumbles it needs a little more water. If it's sticky or leaves a mud on your hand it's too wet.

When you have the correct moisture ram it into place with wooden a mallet or other mid weight ram/hammer. when you have it shaped using a scraper, burnish with burlap, denim, etc. the smoother the surface the less will stick to it. Lastly score it with a butter knife, etc. to control shrink and heat checking.

Allow it to dry completely, times will vary with your weather and you may find it necessary to aim a light bulb at it or hang one in it. Once it's completely dry it's time to begin firing it. Start with a small fire to warm it to a couple hundred degrees f. for a short time. Let it cool slowly before the next curing fire. The second firing should be of medium intensity and last for an hour or two.

The final firing can be brought slowly to forging heat and should be held there for several hours at least and allowed to cool over night or longer. If you can bring it to a nice bright red and hold it there for 5-6 hours it'll fire like a fire brick and be pretty bullet proof.

However, it is NOT a high end refractory like Mizzou or others and will suffer flux erosion. It's also more hassle to install and maintain. It is however far FAR better than kitty litter ever will be.

Frosty

Edited September 1, 2008 by Frosty

[Arbalist]

No luck with the fireclay so far but one thread I read somewhere said Kaolin is better than Fireclay - more resistant to fluxes? :confused: Readily available "China Clay" is 70 - 90 Kaolinite. This is getting complicated (for me!) now, but using the "recipe" for Mizzou castable:

Silica (SiO2) 32.4%
Alumina (Al2O3) 60.3%
Iron Oxide (Fe2O3) 1.4%
Titania (TiO2) 2.3%
Lime (CaO) 2.6%
Magnesia (MgO) 0.4%
Alkalies (Na2O & K2O) 0.6%

I think I should be able to make a suitable substitute using supplies from here:

Clayman: Ceramic Products & Equipment
(They give full chemical analysis of their products which is handy)

When I have more time I'll see if I can get the real deal (Mizzou) in small quantities without paying through the nose for shipping (I doubt it!) In the meantime I'm not that far from Clayman so this is probably going to be the most viable option - except it's going to do my head in working out the proportions of what I need :confused:

Vic.

PS this is not the first time that I've found that you can get what you want in this country - you just need to buy a truckload of it! :rolleyes:

[Frosty]

Of course Clayman no longer carries #5409 Fireclay. Right?

Don't worry too much about matching fireclay's analysis, by time you did you could probably ship 25kg from Alaska and be money ahead.

I'd go with a high cone 10 or so stoneware clay from the dry clay selections. Porcelain is higher fire but you aren't going to need that much and it's more heat check prone.

Use plenty of good sharp silica sand (with breathing precautions) and grog.

I've lined barrel stoves with stoneware clays many times and have been plenty happy with the results.

Frosty

[Arbalist]

Apparently they no longer keep Fireclay as there is no demand for it (according to one thread) but I did email them just in case

I was thinking of the China Clay - Grolleg (High Alumina content) plus the White (Silica) sand, with Perlite added. I could also add some additional Alumina if required :confused:

I'm sure I'll get there in the end. I wish I'd known this earlier as I must have driven right past them several times a couple of weeks ago! :p

[Frosty]

Why the perlite?

Are you trying to make an insulating refractory for a gas forge?

If you're making a solid fuel forge it's unnecessary and degrades the temp rating of the clay. Perlite is only good for 2,000f and then melts, making the remaining refractory crumbly and weak. Even commercial insulating refractories containing perlite rate top heat at under 2,000f.

You'll need to use a layer of straight refractory in contact with the fire to prevent degradation of the perlite but that isn't dificult, just time consuming.

If you really want an insulating refractory use sawdust in the mix instead. It will burn out in the firing and NOT contaminate the remaining refractory, just leave little voids. The finer the sawdust the better it'll work.

If you wet the sawdust, then mix it with the sand and grog thoroughly before adding the dry clay you'll get your best results. Once mixed thoroughly seal it in an airtight container and let it rest a day or two so the moisture will distribute evenly.

Frosty

[Arbalist]

One recipe had vermiculite or perlite in it but sawdust is good

Ah Found it - the perlite came from a link earlier in this thread: Insulative Ceramics for Improved Cooking Stoves

Vic.

[Frosty]

Vermiculite has an even lower level of heat resistance.

These cook stoves aren't going to see interior temps over 1,600f give or take so almost anything will safely improve the insulating properties of the adobe. Using a refractory to build one of these is pretty unnecessary.

Frosty

[pauldude000]

I have a variety of hobbies, which also include in their number metal casting.

I have used a product called "durabond 90" which is a chemical set drywall compound to cast aluminum, and know those whom have used it successfully to cast small brass. I refer to the "hard sand" brown bag variety, NOT the easy sand white bag stuff.

This stuff might work great for a refractory liner for a washtub, or other style, charcoal forge.

I thought you all might be interested.

Paul Andrulis