Which order and size?

[Gijotoole]

I have a bunch of 4x9x1 hard firebricks, some vermiculite plates (8x10x1) and a zoellerforge mos sidearm burner. The back is blocked and I have a brick for the front to help cover the top half of the opening. I use two bricks for each side plus three for the bottom. The vermiculite plates are doubled for a top cover where the burner is centered. I don't have a pressure guage but my reg is a 0-30 Cajun. I have had it up and running, almost maxed out, but still can't reach welding temp. The chamber is about 180 in3. What am I doing wrong that I can't reach the correct temp? If it's a choke issue, I'll read up on how to adjust it. I have no refractory or blanket, but which goes where when I get some? I live in Germany and I can't find any ABANA folks anywhere near here. Supplies are uber hard to come by so I'd like to just make a large but from Coe or Zoellerforge or somebody to get it fixed.

Should I put the blanket inside the bricks and enlarge the chamber or should I get enough blanket to cover the brick structure and the rigidize/refractory coat it? Really sorry, really new. I can't find a good answer in the forums but I'll keep looking.

Thanks again.

[ThomasPowers]

Hard firebricks are real heat hogs and will take a lot of preheating to come up to full temperature. (Know a couple of folks who say they don't try to weld till about an hour after starting the forge---it then welds well until they run out of propane.)

 

Kaowool is a good insulator but is quite fragile and does not work with flux.

 

Have you tried to decrease the side of your chamber and reduce the opening as much as possible?

 

Have you welded before so you know what to look for?

 

When looking for kaowool you generally want to try to find places that sell materials for pottery kilns or boilers for house of industry heating.  Companies that deal with large boilers often have "scraps" around that may be sufficient for your set up.

 

As for in what order:  If you are rough with your forge you need to armour the inside with something---like fire bricks (or pottery kiln shelving) that maytake a long time to come up to heat.  If you are careful and gentle then a good coating of a flux proof material may work and the forge will heat faster. Having a kiln shelf slab or even a stainless steel try filled with cheap clay based kitty litter on top of the kaowool on the bottom of the forge can help deal with flux.

[Gijotoole]

Zoeller's brick forge seems simple enough and I could use my hard brick inside the softer insulating brick. I can't find anything over here. The Germans don't have their shops all over the internet like us Americans. I couldn't find a shooting shop until last week when I kind of got lost downtown-I've been here for a year. I'll look for pottery places. Thanks!

[Frosty]

The issue keeping your forge from coming to welding heat in a reasonable time is not insulation, it's the specific heat of hard fire brick. Think of heating and cooling like momentum in a moving object, the higher the specific gravity (density) of a given object the more energy it takes to raise or lower it's velocity a given amount. Specific heat is analogous but for a given amount of heat, energy is energy though it manifests itself in different ways.

 

So, your hard fire brick has a much higher specific heat than isulating fire brick or kaowool insulating refractory blanket. Hard brick has two things going that make your forge slow to come to heat, first it's high specific heat, second it's low insulating properties, I believe it's R value is pretty close to 1 rather than R 5 for Kaowool. That's per inch and I could have the numbers all wrong. Still, it holds as an example.

 

Simply insulating outside the hard brick is going to improve performance but not much in a small forge. What getting that mass of hard brick up to heat will do is impressive, it will heat your working stock much faster than an insulating refractory liner. We're using a reverberatory forge, meaning the flame heats the liner and the HOT liner heats the working stock by IR radiation. In this case the higher the specific heat of the liner the longer it's radiation will stay energetic. The working stock won't suck the heat from the forge as fast as it will in a Kaowool lined forge.

 

You have a few basic solutions  without having to go over the top. First, you can just let your forge get hot, maybe do some hand or prep work, clean and sharpen tools, have lunch or whatever it takes to keep you sane for the length of time and amount of propane you'll burn while it gets to welding heat. Once it's up to temp you'll be able to work fast as small stock especially will be sparking hot in a minute or two.

 

Another option would be to split your hard bricks. If you have access to a tile saw it's pretty easy, split the hard bricks to between 1 1/4" - 1" and lay your forge with a layer of insulating brick as backers. The liner will be pretty resistant to flux, not proof but resistant, it'll be resistant to getting poked and scraped by stock and it'll have a decently high reverbratory quotient. (Whatever the real term is)

 

Again leaving a free space behind the split brick liner and an outer liner will act as insulation to a degree. Not a lot but a whole bunch better than trying to heat a full brick.

 

Using an insulating refractory liner, be it light fire brick or ceramic blanket, Kaowool being one of many, has issues of their own. Light refractories are relatively fragile, even cold a poke or scrape with a steel bar is going to mark or seriously damage it. Get it hot and it's more fragile. Silicate ceramics are susceptible to caustics and forge welding fluxes are generally pretty caustic at welding heats. Borax and anhydrous borax will dissolve soft brick and ceramic blanket like hot water through cotton candy.

 

There are ways around flux damage though and those are generally kiln washes and the current favorite among the gas forge guys is ITC-100 though it's price is kind of taking out of the home forge market. There are others though and a web search for "kiln Washes," will find many. I'm sure some are available in Germany and everybody over here ships. An alternative I've adopted is mixing my own. ITC-100 is kaolin (porcelain) clay and zirconium silicate at about a 30%:70% ratio.

 

Another fellow on Iforge likes a different recipe being zirconium silicate, colloidal silica and sodium silicate. This recipe is an established kiln wash but is so silica heavy I feel it's likely a lot more susceptible to flux damage. That's just my opinion, I haven't tried it so my opinion is suspect and a LOT of guys like it. He has how to videos on Youtube but I don't have the link handy. Sorry.

 

Frosty The Lucky.

[Gijotoole]

Frosty,
You

Are

Amazing.

My brain hurts. I'll look at our nearby gartenmarkt and see what they have for supplies, too. Thanks again.

[Gijotoole]

Okay, folks. I think I got it pretty much figured out. I am using my mod side burner form Zoeller and one layer of hard bricks to maintain the temps. I haven't found any ceramic or pottery dealers anywhere near town but I did find some ytong (aerated concrete) at OBI (like Home Depot-it's even white and orange). I made a bunch of cuts and got her started up and man, did she get hot fast. And how! That chamber was screaming red in no time. Problem I have now is that the hard bricks were glowing all the way through and it started to really eat at my ytong blocks. The front of the forge is one ytong big brick and and I am not sure how long that stuff can hold out before it just crumbles. There are quite a few little cracks developing already. I have no pressure guage so I think I was really getting on it (turned the 30 psi reg all the way up and then backed off 5 full turns, no idea how much that is) but again, I can'tt tell what the temp was. I'm more presenting the fact that I am really glad I got it so hot than anythign else.

 

Can I use some lava rocks between the hard bricks and the ytong blocks to add more protection?

 

Will some ITC (or something else) help to preserve the soft bricks, like coating to preserve the hot face (is that the right term?)? I can add a couple more hard bricks for the opening but it seems like I'm going to burn through those unless I can get the heat under control.

 

Man, this is so much fun!

 

[jcornell]

I don't know if your soft, outer bricks are rated for this temperature.  If not, the expansion and contraction that come from heating and cooling will crack them into pebbles sooner than you think.  The hard bricks suck up a lot of heat.  If you coat it with Plistix, Metricote, ITC-100 or home-brew zircon/kaolin wash, all of these are refractive coatings that reflect heat back into the chamber, and incidentally, cut back on how much heat the hard bricks suck up.  The coatings make the chamber more efficient, but would do next to nothing if painted on the inside of the soft bricks that are outside the chamber's hard bricks.

[ThomasPowers]

Can you space the two apart?  Perhaps filling the gap with wood ashes?  Trying to decrease the temp the cement blocks see.

[Gijotoole]

I'll look into some sort of barrier material that will still help insulate the hard bricks. Can I use sand? I'll try ashes-gives me a reason to have some fires.

[jcornell]

I'm wondering if Vermiculite would work in a gap between the hard and soft bricks?

[Gijotoole]

I have access to a 10x20 Verm board (26€) at the hardware store. Can I use this or should I try and find the powder. Adding to the pain is the fact that I can't leave my forge in place, it has to be taken apart and then rebuilt when I want to use it. I live on a small chunk of US soil in Germany-different rules.