ZebraPaste

Update to the aluminum phosphate binder. One test (filled a steel bottle cap) turned out successful. No shrinkage cracks, thermal shock test passed, harder than expected (used it like a sharpening stone on a scalpel I made from L6 scrap). Can’t get it work work again, must have some contamination or something.

A little late but maybe this will help someone. Galvanized coating is not just zinc. It’s mostly zinc, but also has more than a small amount of lead, antimony, cadmium depending on what process was used and the grade of coating. The zinc is the least of your worries. I’ve had galv poisoning a few times, sucks each time and you don’t get immune to it it actually gets worse each go around if the dose/exposure duration is the same. Anyway there’s a chelating chemical called EDTA disodium-calcium that you can get online. It’s very important to understand the caution you need when using that, it will strip metal ions from your body, starting with the heaviest (lead etc.) and moving all the way to down the line. If you use it too much it will make you anemic and hurt you. It’s an old treatment for chemo detox and regular heavy metal poisoning. It’s been replaced with other things for human use but it’s cheap and shelf stable so if you’re in a pinch and idk swallow some mercury it’ll do the trick. Read about it thoroughly before you use it.

I’ve gotten my hands on some phosphoric acid and aluminum hydroxide. Mixing them with a little water (amount almost doesn’t matter it acts as a vehicle/lubricant for the reaction) and gentle heating (keep above 170F but below 212F, it will boil but not at true water boiling temp) makes aluminum phosphate. If you heat too much you will get crystalline product at the bottom of your container, I used a mason jar and burnzomatic. There are plenty of videos on the process online. I’ve tested some aggregate mixtures and curing temperatures. This stuff is amazing so far. The mixture doesn’t dry and harden at room temp, which means you have loads of time to work it into your shape/on you the surface required. Curing is starting around 175F which is lower than what google showed in search results. Very hard and durable product at 400F cure, better than any water cure castable I’ve gotten yet. It is cheap, and quite strong as far as binders go. You won’t need 85% lab grade acid, you can boil down cola if you really wanted to. So far any aggregate has responded well, but mixing with a water curing cement has yielded significant expansion. The expansion is temperature dependent and increases in a linear fashion. Curing at 180F gives roughly 35% increase in volume, 400F about doubles the initial volume. The product is well worth the expense of raw materials. If you’re looking to create your own firebrick this is very good for making an insulation layer and flame face/abrasion resistant face all in the same unit. My tests are showing virtually no cracking when heated with propane air. Will use acetylene/oxy to failure for more data.

Excellent advice rockstar.esq and Brian Hibbert. It is very often the job you take that hurts the most. Economy of scale is also very important. We are a small fabrication shop that specializes in stairs and rails. On occasion we get asked for structural steel but often we turn the customer to other shops because we know right off our bid won’t be competitive or it won’t be profitable for us. Learned that the hard way so being cautious and not over extending yourself is very important. One thing I’d like to add is know your market in your area. We’re right next to the very wealthy towns and New York, often we see oh they are willing to pay $90k for this house to have metal work….9 months later the project is done and our profit is nonexistent. So don’t be swayed by a contractor being willing to share a budget number with you.

Has anyone here tried making crucible steel in a propane forge? I’ve seen many videos of using coal set ups and even one guy on YouTube (shake the earth, his videos are cool) using a microwave casting set up. I’m making my forge to be able to take the heat and will try it anyway but if anyone else has I’d like to hear their side of it. Thanks

Hi JHCC, I want the cast mixture to be more durable and already have the IR reflective properties of the available coatings. I have been experimenting with binders, instead of silicate binder or calcium aluminate, the next one I’ll be trying is alumina phosphate. Even if none of this works it’s still very fun.

I’m currently exploring how to get better performance from cast refractory. Some notable things I’ve come across include calcining your own additives. I learned that if you burn epsom salt with a torch it releases some toxic gas that is basically sulphuric acid. What’s left over however is magnesium oxide, the highest melting temp oxide you can get. In small amounts it increases the melting point of refractory materials. 1/10% is enough to stabilize alumina and zirconia when brought up to full temp (3000f+) Alumina hydroxide aka alumina hydrate is usually available as a pottery additive. If you calcine/burn the heck out of it you get alumina as a raw material. Great for refractory mixes. Don’t mix alumina hydrate into refractory mixes. It has made several of my tests fail. The hydrate vents a ton of water (roughly 1/3 by weight) when it heats up and it blows up and or crumbles to dust. A fair few times I’ve read posts on websites about people trying to create a flame face coating using water glass/sodium silicate and a product called zircopax. The zircopax is never going to stick doing that, and due to the super fine particle size it will flake and crack and warp as it dries. Get calcium aluminate cement binder instead. When using the CAC, calculate the amount of water you need, and use the water glass instead of just water. Water glass is 40% solids, so that remaining 60% is available water for your cement to cure. The effect is a faster cure, and a much stronger binder. Sodium metasilicate is sold dry as deck cleaner. It’s cheaper than buying the pre diluted solution, just dissolve it in hot water. If youre trying to go the zircopax route like I am since its got a higher service temp than most other products, you will benefit from making frit out of it first. Mix a batch with 10% water glass and pack it into a sheet. Let it dry and then heat it up as much as you can. I ran it in my forge until it was white hot. Then smash it up into coarse sand size particles. Mix 4 parts sand size particles, one part fine particle as you bought it (should be 2-5 micron powder), and somewhere around 15% by weight of CAC. Casting this 1/2” thick should be a very durable material. As an optional note I got from one of the manufacturers of similar products, add a 1/4% by weight polyester fiber to the mix. Its job is to burn out and make vents for excess water vapor to get out as you cure and fire the mixture.

When we have rails or other steel products going outside we use cold galvanizing paint as the primer coat. We have to warranty our stuff so we opt for the zrc brand 98% zinc. It’s certified for repair on hot dipped industrial products. Doesn’t have the same abrasion resistance as hot dipped but it’s as protective as it gets and takes top coat really well. Best brand of paint we’ve used is majic farm implement paint. Not sure if those are available where anyone else is but I’d put those layers up against sand blasted and powder coated products any day.

I never spoke directly with Frosty but his posts and replies were what drew me to this forum. Literally his opinion on what we’re doing now was the only reason I made a profile. You are missed Frosty.

Update to coal slag puck: calling this one a failure. Didn’t break from the thermal shock testing but lost strength and I broke it with a slight smack from a steel bar. Next puck will use phosphate bonded alumina binder.

Hi Brian thanks for the heads up about the header info. I’m testing a new puck tomorrow so I’ll update with what happens. From what I’ve gathered, a forge liner has slightly different needs for the roof, sides, and bottom (if the burner is blasting directly down) or whatever the direct flame contact face is. I spoke with some sales reps from the companies that make the available products and a few raw material producers to get some data. My goal for tomorrow’s test is can I get this puck to heal itself with each thermal cycle. Basically I’m going to heat it to bright yellow and let it air cool. Then heat it again and throw it in water. Then dry it out, heat it again and let it cool in a slow controlled environment to see if it deals with thermal shock. Last time the puck stayed whole but I was able to snap it with my hands. So this one has the added coal slag to see if a lower melting point aggregate can act as a binder since the calcium aluminate cement is probably being calcined again at those temperatures.

Hi all, throwing my cents in here. If you heat a hydrocarbon beyond its auto ignition temp without a source of oxygen, or with very little oxygen, you get molecular breakdown. Some of those new products burn at higher temperatures than propane normally does.

A bit late to the party on this thread but currently researching the same thing, using coal slag as a portion of refractory mix. My recipe is using coarse grade blasting media, roughly 1/16” particle size. Still in the mixing formula phase but so far I’ve found it to be a good mix in for the wet consistency I look for. I’m also using zircopax plus, perlite, calcined alumina, alumina hydroxide, dry sodium metasilicate, magnesium oxide that I calcine myself from magnesium sulphate, bentonite clay, and calcium-aluminate cement binder. So far it has been a mix of great and awful. Some mixes set too fast to work. Some take too much water to make workable. A few have held up really well. One puck (3” diameter by 1/2” thick) I was able to make glow white with an acetylene torch and it vitrified down 1/8” ish but no further after about 5 minutes. After cooling it was very hard to break by hand. Most of the other recipes failed my expectations. Two exploded which I’m chalking up to retained water even though they got dried in an air fryer for a couple hrs. I’m mostly doing this for fun but also so I can stop melting down my forge. It’s the third rebuild, last one I coated in a mix of zircopax and kastolite-97l which was decent.