Hi I am Werner from South Tyrol Italy. Would like to build me a melting furnace. I am a complete novice, but I have a friend who casts at home, complete 2 stroke cylinders. He has already given me many tips for my first mold. Would now like to build myself a furnace. I'm not sure if I should start with just a small propane furnace for aluminum, or design the furnace to handle cast iron as well. For an aluminum casting of about 2-2.5kg without basin sprue or riser, how big does the crucible need to be. How would a possible simple melting furnace look like if it only has to reach the temperature for aluminum. 200lt and 60lt metal drums would be available.... Translated with www.DeepL.com/Translator (free version)
Ciao / Gruetzi Werner! I have just started casting Alu with a 6kg kit from Amazon which is really more like 1.5kg Alu once you figure the bronze to aluminum conversion and moving a smaller crucible to be in a better place from the burner. Also being so close to capacity makes it had to pull the crucible out with the supplied tongs and I have longer pieces of good scrap that stick up. Sometimes my casting the gating is as much as the part in weight. So maybe I need a bigger furnace too...I am not an expert but maybe if we have some more numbers people can read and comment. From Alibaba: innopack-steel drum oil paint bucket/dyestuff bucket 60 liter steel drum 415*395*480mm [ 16.25 x 15.5 x 18.875 inches] 75mm [3"] top, 75mm [3"] bottom, 50mm [2"] each side insulation, leaves 295mm [10.5"] diameter and 330mm [13"] interior. Need space along sides for hot gases and lifting tongs. Need space at the top for hot gases and longer pieces of clean scrap Alu to stick up before they melt. So if we allow say 35mm [1.375"] per side and 75mm [3"] on the top, crucible max is 225mm [8.75"] diameter and 260mm [10.25"] tall. So a Salamander A20 crucible would be about max height but only 1/2 full and A10 the smallest very full to have 5kg Alu 2.5 Kg [5.5#] part and 2.5 Kg [5.5#] gating system) assuming Alu is about 1/3 dense as bronze. You may want to check my math before ordering anything, still first cup of coffee... PS Something like this with the barrel, insulation, and A20 dims above:
I'm not a mason and wanted to keep the stove as simple as possible. With as few different building materials and steps as possible. preferably a steel barrel poured with a heat-resistant mortar And as a lid also the lid of the barrel poured out probably something like this http://forums.thehomefoundry.org/index.php?threads/my-small-propane-fired-5-gallon-furnace.2245/ but one number bigger.
An A10 is a good size crucible for a hobby furnace. For low cost and ease of construction, performance, and light weight portability, it's hard to beat ceramic fiber insulated furnaces. http://forums.thehomefoundry.org/in...ulate-the-right-furnace-size.1799/#post-40110 Best, Kelly
Welcome Werner, The biggest question is what type of refractory material is available for your furnace lining. Commercial products specifically made for foundry furnaces is highly recommended if you can get them. Not fireplace cement, but foundry furnace refractory. We have an active member here who lives in Austria so maybe he will have some recommendations for buying refractory materials and crucibles. Melting cast iron with propane is possible, but you would find it to be difficult. Aluminum and copper alloys are much easier. Your furnace bore size will be determined by your required crucible size, so I’d recommend finding an available crucible before building the furnace. Buying a commercially made crucible is highly recommended. Steel crucibles can be used for aluminum but are not great. For a 2.5kg casting, you’ll want a capacity of about 2 liters to accommodate sprue and gating. (2.7kg/liter). The furnace bore diameter will be 100mm larger than the crucible diameter. There are several ways to approach this, so finding out what materials are available to you before you begin will save much time, money, and aggravation. A list of potential materials: Refractory cement (castable or plastic) Ceramic fiber insulation Refractory mortar Dense firebrick Insulating firebrick Crucibles Pete
that's just the point. On the Internet, of course, there are many instructions, but usually some specific building material is used. I have to see if I can buy the building material here in Italy or Austria. Work as an agricultural machinery mechanic, dirty diesel, and waste oil would always be available. but first the melting furnace, before I take care of the burner. I think if an A20 fits straight in there that would be great. I would still like the version with the poured barrel best I think. Maybe just poured with a castable refractory cement ?
Ah, we have some new information. You may start out with propane, but you will not want to pay for it for very long. If you have diesel and oil available for free, that is what you will end up using. That is important because if you build a light duty furnace that will handle propane you will likely destroy it when you switch to oil. So here is a specific recommendation: your furnace should have 50mm of ceramic fiber insulation and 25mm commercial castable refractory cement rated to 3000F. It will be bulletproof. The bottom of the furnace can be solid 50mm thick or can have a ring of insulation, but it should be solid in the center portion kind of like a doughnut so there is solid support in the center. Your crucible will sit on a pedestal (plinth) which will be about 100mm tall. I agree with Kelly that a #10 is a good starter size but if you only want to build one furnace you might as well build for a larger crucible. A #20 would be the maximum in aluminum I would pour by myself. A #20 from my supplier is 190mm diameter by 228mm tall. Yours may be different. Make sure of your size before you start. So your steel shell should be about 440mm diameter. It should be 428mm tall. That leaves 50mm between the top of the crucible and the bottom of the lid. The lid should be 75-100mm thick with a 100mm exhaust hole. Pete
That's right, A20 is probably really too big. I found this A16 crucible here in Europe, for example, and an A10 would probably already be big enough. https://www.schamotte-shop.de/schmelztiegel-a16.html For the rest of the building materials, where could I look?
You can find ceramic fiber online. I think you can get 2200F-3000F. They probably carry it at the same place as the crucible you linked above. It can be layered so you could get thinner stuff and layer it. Shipping costs aren’t too bad. Refractory cement is very expensive to ship so you’ll have to do some searching for it to find it locally. Search for “refractory cement” in Italy, etc. For example I quickly found a manufacturers office in Trino called REFRATECHNIK. They probably wouldn’t sell directly to you but you could see if they have a distributor near you. Pottery shops, local foundries, furnace repair, masons of your acquaintance, etc. You’ll probably need a couple of bags (100lbs) but you won’t know until you’ve decided on your furnace size and then do the math. Pete
I would look for a place that supplies foundries or a place that artists go to to buy clay and supplies. Just an example, I am not a customer since not in the EU but buy my Bentonite and parting powder in large bags for small money from a similar place here nearby: https://www.hobbyland.eu/eng/shop/ceramics/kilns-and-supplies/fiber-products/c-00000961/ You may want some firebricks too. I found those to be less expensive from a professional shop that supplies industry.
Ceramic fiber from Grainger. very reasonable price and the fastest way to make a furnace..... if your in a hurry https://www.grainger.com/product/UNITHERM-Ceramic-Fiber-Insulation-5-54TP53
A lot of this information is totally out of date, but it's a good place for looking at pics of the many furnaces people have built for melting metal.. Don't think anyone posts there anymore.. There is a wealth of different approaches to melting metal for casting.. metalcasting and general metalworking links (backyardmetalcasting.com) Fred
I definitely second the recommendation for a ceramic fiber furnace! Mine was very easy to build, and it's incredibly light weight. Here's my thread on it: http://forums.thehomefoundry.org/index.php?threads/kaowool-propane-furnace-build.1031/ Inspired by Fishbonz's design (another member here); he was a lot of help throughout the process.
