Hello All. I have started designing a furnace based on Steve Chastain's oil fired tilting furnace book. Rather than tilt, I am going for a dip out option of having roughly 75 lbs capacity of aluminum. His design had a 50 lb capacity and melted it in 35 min with oil. I'd love to make it module meaning I can have one lid for aluminum crucible and another for brass/bronze. For the brass bronze option I would have a plynth that puts the crucible right under the lid. In the book, he just uses a steel pipe (8 or 10" ID) as a crucible, but lines the inside with a non-wetting coating to protect the steel from aluminum. I don't know how this held up for him or how much flaking he would get on the outer portion of the steel crucible. I have used protective coating on ladles at a former foundry I worked at and it works well, just need to reapply daily. Here are a few of the main areas I'm looking for feedback on: For the lid, I am thinking of a 3/8" piece of steel putting a couple layers of kaowool under it for insulation Looking for best option to insulate the main body of the furnace (wool & mizzou?) How thick would you make the bottom base and would you make it a separate piece? The burner inlet would come in towards the bottom tangentially The burner outlet would come out at the top also tangentially. I'm thinking ~4" ID on that. With the burner coming out the side of the furnace, it eliminates the metal from being exposed to the burner combustion and hopefully reduce any hydrogen pickup during melting. There will be a little flapper lid on the top of it that I can open for charging and. Let me know your thoughts/suggestions/questions. I've attached an exploded view what I have so far on the model.
On the subject of steel crucibles for aluminum, if you are just doing ornamentals and don't care about the impact on mechanical properties due iron contamination, I'd say OK. You can coat the interior with washes, or Boron Nitride, but even so, a carbon steel exterior will be reduced by temperature and the furnace atmosphere. There is a member here who has several hundred melts on a stainless steel crucible. Furnace atmosphere will be a major factor in longevity. For brass/bronze, I would say forget the idea of a metal crucible. One thing about dip outs, do you plan on using all 75lbs and the complete melt each time? You would never leave any appreciable heal in a non-metallic crucible because the expansion of the metal on the next melt would break and put an end to the crucible. Maybe that's why most dippers are also tippers. Frankly, even though a large clay graphite crucible will be expensive, I'd advise against a steel crucible all together. If you get your burner tune a little lean with some impingement, you'll be spilling 75lbs+ of aluminum into your new furnace. I'm sure you'll get some comments on the side exit exhaust. I suspect an equivalent area of 4" diameter might be a little on the small side for an oil burner in a furnace of that size. That location will be very hot and take a beating from the heat. You will still need to cover the crucible for heat retention. Best, Kelly
Thanks Kelly. My intent would be to pig out the entire unused metal each time I melt. I have a couple of 35 lb pig molds for that. Definitely was going to have a proper crucible for brass/bronze and with your comments really considering doing one for aluminum. How much of an air gap between the crucible and furnace wall is ideal for the oil fired furnaces? I have a 20 foot long section of 24" diameter duct work I was going to use. I also have an old air compressor tank that measures 18" in diameter I could use as well.
Well, probably 2.5-3" clearance per side for an oil burner of that size. You're going to want the 24" duct for the outer skin. An A70-A100 crucible would be in the range of 12-13" Top OD, plus another 5-6" for clearance, put's you in that 18" bore range you had mentioned. That allows for 3" or wall on each side. Even with a relatively thin hot facel that puppy will take some materials to build and some energy to heat up initially. -Very curious about what you're up to with all that metal.......I have an A60 and thought that was ambitious! Best, Kelly
ambitious means sometimes crazy. But, along with ambitious, is crazy... comes ingenuity. Kelly comes across as the type of guy that has three different back doors/fixes to any project (this probably comes from experience). I'm more of a trial and error guy. I almost never get something right my first try. That said, what does A60 weigh empty???
50lbs in 35mins. N O P E! Maybe a subsequent melt, but not from cold. And I run an oil burner myself. Why do you need to melt such a large amount at once? Melting metal is only 10% of this casting thing and the easiest part. The real work is before and after the pour.
33lbs With his previous posts, sounds like J is planning on permanent mold casting. With simple gravity fed PM, consistent cycle time can be a key factor, so having a large source of metal to is advantageous. It will need to be able to hold temp if so and he'll need to get to know his burner well for that. Best, Kelly
Exactly. That is the reason for holding so much metal. With the permanent mold machine I've constructed, I could pour roughly 2-5 lbs every 2-3 min once the die is hot and running right. Just need to make sure whatever crucible I use has a large enough opening for whatever ladle I am using. Ideally I could find an old electric resistance furnace with a 250lb capacity. We had one at the last foundry I worked at and could get up to pour temp within a 3 hours, but those babies are $18,000 brand new. Kelly, I just looked at your furnace build and holy crap. That thing is amazing. Have you melted any aluminum in the A60 crucible yet and how long did it take on electric.
The top ID is 9". The top OD is 11" without the spout which projects about another 1". It is about 14" tall. Here's a link to the Morgan full line. You can drill down into any line and select the leaflet with application data and dimensions. I use the Morganite series. The others are more recent additions/acquisitions. Morgan Crucible Full Line I use Salamander Super Clay Graphite. Here's a direct link to those under the Morganite product area. Salamander Super Clay Graphite A 5lb shot would be a pretty good size ladle for an A60. With the depth of the ladle, not sure how many full dips you could get out of an A60 but I'm guessing no more than 30-40lbs depending on ladle dimensions. You'd have to tell me a little more about your casting objectives, but I was thinking holding furnace makes sense for you. If you are just going to cast aluminum, I'd say resistive electric all the way. For Bronzes, with Kantlal A1 type (FeCrAl) wire, possible but marginal. -Would need more discussion on that one. Are you going to permanent mold bronzes? You could have very precise control of temperature with a resistive electric. I wouldn't recommend this for the average hobbyist, but a guy with a Fadal in the corner of his shop isn't the average hobbyist. My resistive electric is only 8kw 240vac single phase but there is no reason to be limited to that power input even in a residential setting.....but it is sufficient and practical. What kind of electrical service do you have available? I think you could purpose build a resistive electric for $2k worth of materials, and $500 of that would be the crucible. In fact, you could probably buy a used kiln for a few hundred dollars that would do the job, if you were willing to wait 4-5hrs for the first heat. If you watch Craig's list and ask around people practically give them away. The best deals are ones that have failed heating elements but otherwise good refractory. They are cheap and easy to rebuild. I went ape sh!t on the metal fab but it serves my purposes very well and I really like it. When you commit to a furnace size and heating approach we can talk materials. I have only used the larger furnace for heat treating at this point but my next project may be it's maiden melting voyage with the A60. Like I mentioned in another post, I can pour 20lbs Al out of my 10" bore rig but the larger 14" ca\n be mounted on that same lift apparatus. I said screw the switching and built a (somewhat) simplified lift for the larger one at the link below. 14" Bore A-60 Furnace Lift For melt time, 8kw will melt about 20lbs/hour in my rig. There's not much difference in first heat and subsequent heats in my smaller furnace because this furnace is very low mass but a given furnace the first heat will be lengthen and a strong function of furnace mass. Initial heat is much longer in the larger furnace. But you can throw more power at it in a bigger furnace than 8kw. My larger furnace was intended to be fuel fired for melting, and electric for heat treating. KCs low mass furnace Best, Kelly
you might lookup die casting furnace. That is essentially what you're building, just scaled way down.
