Made a Forge, Doesn't Work

[Frosty]

1 hour ago, JustAnotherBiker said:

All this talk of shells, fibre blanket, coatings and so on... What's wrong with a dozen soft fire bricks and a few bits of angle iron to hold the burner? 

Surely that's an easier, less expensive, more flexible entry to gas forges? 

Good question. As usual it's not really possible to answer without knowing what you have available as soft insulating fire brick. Here 2,000 f. soft brick are about $9.00 ea. IF you buy a box. 2,400 f. soft fire brick run about $13.00 ea and are special order by the box only. My shop forge will melt steel so even the expensive soft brick won't last long. I typically get 2 firings before regular soft fire brick begins to crumble, they'll often break in half on the first session if it lasts an hour or two at forging temps, welding temp just kills them.

I have a box of soft and one of 3,000 f. hard fire brick. I'll use a brick pile forge at demos so folk interested in maybe giving it a try aren't looking at several hundred $ just for the forge. Off the shelf plumbing parts and a stack of bricks isn't an unreasonable expenditure to see if they'll like it enough to buy or build proper kit. It gets us talking and that's what demos are for IMHO.

I use a brick pile to experiment with forge shape, size, burner placement and orientation as a matter of course. It's not necessary to let it get welding hot to see if the flame does what I need. I have practice though.

A hard fire brick will take the heat even if you build a "golden bullet" burner that will vitrify it. I have exactly ONE burner that actually melts a 3,000 f. split hard fire brick. That's out of a few dozen I've made for my own use and that was after I stopped using my lathe because most folk don't have one. Anyway, hard fire brick has a slightly better insulating value than limestone and it's a better heat sink, has a higher specific heat. 

When I've used a hard brick pile for welding demos they typically took half an hour to reach forging temp and something like another 20-30 mins to reach welding heat and I had the regulator maxed. The burners wouldn't burn at a higher pressure.

I've kiln washed the split hard brick floor of my soon to be retired shop forge and gave up kiln washing the soft brick, it breaks up anyway and kiln washes are too spendy to throw away. 

You can use soft brick as an insulating outer liner, pottery kilns are made this way all the time but you need something to protect it from getting too hot. All I can think of is either a dead air layer or perhaps a layer of ceramic blanket at which point it makes more sense to just use another inch of blanket.

A lot of thought has gone into this stuff and not just me, not by a LONG shot. We spread what we know works and is the most economical long term. If a person't goals are short term a brick pile makes more sense, it hardly takes any shop skills beyond Leggos. I just leave a gap and poke a burner in, no mounts, brackets, nothing more than something to prop it up.

Frosty The Lucky.

[JustAnotherViking]

That sounds quite pricey. The ones I picked up are rated to 2600f and were less than $5 each according to the current exchange rates. Can buy them in any quantity. 

Guess I've been lucky with the way I've framed mine. 

About 10 mins to get up to temperature, drop the pressure by half, and it runs at forging heat quite happily. Cracked, but not disintegrated. 

Running for an average of two hours a day for a month and a half so far and haven't had to replace any yet. 

Haven't tried welding in it though. 

 

[jcornell]

My first two forges were built from soft firebrick.  It works well, until the brick breaks down because of thermal cycling.  The next two forges were coffee can forges lined with Superwool HT.  Forge #5 is a freon can, lined with 8# kaowool.  So, yeah, soft brick works, but it's not a long-term solution.

[Frosty]

19 hours ago, JustAnotherViking said:

That sounds quite pricey. The ones I picked up are rated to 2600f and were less than $5 each according to the current exchange rates. Can buy them in any quantity. 

Guess I've been lucky with the way I've framed mine. 

About 10 mins to get up to temperature, drop the pressure by half, and it runs at forging heat quite happily. Cracked, but not disintegrated. 

Running for an average of two hours a day for a month and a half so far and haven't had to replace any yet. 

Haven't tried welding in it though. 

 

That's a different story, soft brick in that range just isn't used much here and shipping can double the price. Mike Porter posted a source for high temp. insulating refractory tile that comes in different size, shape and thickness. It's very versatile and reasonably priced. I don't have numbers off the top of my head but I know I've been thinking about getting some to put it to the test.

It sounds like you have the good stuff. A person doesn't need 2,600 f. to weld if they prep the joints well enough. I'd be running below it's max working rating for the most part anyway. I'm thinking a coat of Kast-O-Lite 30 and maybe a kiln wash would armor it enough to make a good daily driver.

Do you know how your brick stands up to borax based flux? If you have a broken brick you might want to give it a test to see. It really sucks to have a good forge dissolve before your eyes.

Frosty The Lucky.

[JustAnotherViking]

I got them from a pottery supplies store about 30mins drive from work, so pretty fortunate there.

Haven't tried welding/fluxing yet at home, although I did get a lump of vermiculite board to set on the floor of the forge for that purpose at the recommendation of another smith down at the local group.

I've 1/2 a kg of high alumina kiln wash sitting in the cupboard, but i'm going to save it for v2 of the forge (and try getting a kiln shelf for the floor)... the biggest issue i've had with the bricks to date have been me hitting them accidentally with bigger work that only just fits in the forge.. i've had a few bricks crumble a bit, but still hanging together well enough for continued use.

I wouldn't say it's a 'good' forge, just one that works well enough for my purposes to date 

 

I'll likely go down the wool/refractory coating route around v3 or v4 once i've a better idea of what sort of size and features I need.
Can probably keep it quite small if I get an oxy-propane torch as most stock i'm using is fairly small (as long as it can pass out the back), and only gets difficult to fit in the current forge when trying to bend it into odd shapes, lose the heat, fight with the vice, try and heat again, bit more bending, swear at it, and so on.

[Frosty]

Kiln shelf shouldn't be too hard to find, people fire pottery everywhere. Be sure it really IS high alumina, there are some grades that are close but no cigar.

Yeah, soft brick is pretty fragile at forging temps, really easy to gouge and it doesn't take much of a bump to break them. The HVAC supply, service company I buy from says fragile is pretty common for soft fire brick, even their high dollar grade. Ceramic blanket is REALLY fragile at forging temperatures, like taking a stick to a spiderweb. That bit of knowledge is from the days before I knew any better. I keep the blanket out of the air as much as possible, I even spritz it with water before cutting to keep particles from floating around.

There's nothing wrong with a brick pile forge if you have the right bricks. Good enough is good enough. Once you know what you need and want to go more permanent. Building one with a ceramic blanket insulating outer liner and a cast hard inner liner I think you'll be really pleased with how durable and efficient it is. You can poke 1/2" of high yellow hot, Kast-O-Lite 30 with sharp cold steel like it was concrete with about the same effect.

I don't carry on about the stuff because I get paid to. 

Frosty The Lucky.

[Mikey98118]

The bricks I recommend are K26; that "K" in their name is important because this brick from this manufacturer( Morgan) can match the insulating value of ceramic wool at 2000 F and up, but is much tougher than the standard foamed clay bricks that can't withstand thermal cycling.

By that I mean the fast thermal cycling found in forges; not the days long cycling found in kilns.

[Buzzkill]

22 hours ago, Mikey98118 said:

The bricks I recommend are K26; that "K" in their name is important because this brick from this manufacturer( Morgan) can match the insulating value of ceramic wool at 2000 F and up, but is much tougher than the standard foamed clay bricks that can't withstand thermal cycling.

By that I mean the fast thermal cycling found in forges; not the days long cycling found in kilns.

Mikey,  are you familiar with the Greentherm bricks?   They come in 23, 26, 28, and 30 designations which of course correspond to the the temperature rating in degrees F.  They seem a bit pricey,  but that could possibly be forgiven if they hold up to thermal cycling and are resistant to mechanical damage. 

I haven't seen much info from anyone who has actually used them for our purposes, so I'm looking for any firsthand knowledge I can find.

[Mikey98118]

Never heard of them, Buzzkill; this isn't surprising. I expect new bricks coming on the market to continue increasing, in response to increasing demands for high tech brick, which can do more. Fuel costs more money all the time, and that drives customers to pressure manufacturers to improve their products in order o protect their markets.

[Irondragon Forge ClayWorks]

Looked them up on Google. Nothing about forges, but the SDS is on their web site.

https://thinkhwi.com/products/greentherm-26-li/

 

[Buzzkill]

7 hours ago, Irondragon Forge & Clay said:

Looked them up on Google. Nothing about forges, but the SDS is on their web site.

Yeah, I found that too - and a few places that sell them, including Amazon.  I'm just curious if they are soft and crumbly in short order like the IFB's I've gotten so far or something different.  I'd rather not spend the money to find out if I can get that info from someone who has actually used them.