Propane tank/fueled furnace build

Discussion in 'Furnaces and their construction' started by Shawno, Dec 27, 2020.

  1. Shawno

    Shawno Copper

    Thanks again guys!!
     
  2. Shawno

    Shawno Copper

    Melted metal today. Cool! :)

    In the previous test burns, commented on earlier, the flame seemed to smooth out when I used my hand to slow the airflow. I put a restriction plate on the burner to adjust air flow but think that the cross piece which supports the plate might be so large, it impedes the air flow itself. I ended up running the furnace on about 12 psi today in order to get a "smooth" burn.... With the restrictor in place, I could adjust more easily and found that the lower pressure worked better. I will keep playing with this.
    The cross piece is only 3/4" wide but the fitting is only 1.5" iirc so the actual area the cross piece covers is possibly a factor...? But the furnace seemed to get hot quick and melted quite a few pieces for me so maybe it is as it should be.

    This is my absolute first time melting aluminum and probably have lots of things stacked against me but at least I got to see the process. When I put the aluminum into the lathe, it does not mill well. I made a few soup can size pieces. I only tried turning one piece, and only got as far as the photo below. I am wondering where my biggest gain might be though. I know I need to go to the graphite crucible. I am waiting to find a propane tank to put the extension on the top of the furnace to take the crucible I have. Not much use ordering a smaller one as the reason I wanted a furnace was to get larger chunks of aluminum to work with. So for now, using the steel crucible. This is the other extreme though. All of those castings (ingots?) except for one came from one pour.

    Here is the list of notes regarding my adventure today.....but did I tell you I melted aluminum? :D

    Feel free to comment if you see something that would have a large gain for me.

    I have a steel crucible.
    Metal was mostly clean. A piston had some carbon on it but I cleaned all of the oil off.
    All pieces going in were cast aluminum. (in typing that, I think one small piece of flat 3/32 plate went in. It was a small portion of all of it.
    I only removed dross with the lifter. I made a fast sieve (while the furnace was running) but found that most of it could be collected by my lifting tool. I have not researched removing the dross too much but it seems it was usually just collected as I did today., pulling to the side, then lifting out?
    I burnt off most of the cans liners before using them as molds but maybe not clean enough?

    Now that I have seen the process, I need to go back and reread everything. This project has dragged out for a while so nice to see it finally going.

    Thanks for the input along the way!

    Cheers,
     

    Attached Files:

  3. Ok that's another one hooked on casting :D.
     
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  4. Shawno

    Shawno Copper

  5. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    These are the most important factors, but also a lean furnace atmosphere, and minimizing melt temp to avoid hydrogen porosity. Some alloys have reasonably good machining properties as cast, others require heat treatment but as I think I mentioned early in one of your threads you will never get to the machining qualities of best wrought alloys with cast.

    Best,
    Kelly
     
  6. Shawno

    Shawno Copper

    This is from Post #2 of this thread. I think some of these were not addressed as we got off on the discussion of insulation for several pages but now that we are discussing machinability, Kelly's questions mean more to me. The metal going in was mostly storz fittings from large hose (should be good quality), one aircraft piston, a piece from a snowmachine undercarriage which looked very nice so I assume good quality and that one small piece of extruded mentioned earlier.

    I did notice my cutter with aluminum stuck to it so exactly what Kelly mentions.
    How do I find out if what I used is "300 series alloy"?
    As for the pounds of aluminum to cast? Not sure yet. I originally only wanted some pulleys but now, mmmmmm......
    I have some lawnmower engine blocks to melt down, and steps from trucks, but that is all I have collected so far. Is pop can metal good for anything? I know, generally, don't use it but if used in some percentage, does it add anything...? optimistic...:rolleyes: Or just don't even try....
     
  7. Shawno

    Shawno Copper

    Kelly, I guess we were both typing at the same time. Thank you.

    Temperature might have been another factor today. I was cutting up other stuff to go in while it heated/melted so did not monitor the melt much. Again, probably not remembering well, but had it in my head that melting longer was better. Sounds like the opposite. So are you saying that as soon as the last piece is melted, it should be poured? Not simmered like a tomato sauce? :eek:

    So now, another question, if I find these too crappy to use, any gains in remelting them and doing something differently? Assuming that the original casting was decent material?

    "I think I mentioned early in one of your threads you will never get to the machining qualities of best wrought alloys with cast." ok, starting to make sense now....
     
    Last edited: Mar 15, 2021
  8. Jason

    Jason Gold

    You'll get better at watching the temp of your aluminum and fuel mixture. It's not the soup cans. I do the same thing and sometimes get a turd when I turn it on the lathe.
    But at a minimum, always start with cast scrap and say NO to cans, ladders and window frames.;)
    Congrats!
     
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  9. Petee716

    Petee716 Gold Banner Member

    Way to go!
    Kelly's post #2 that you quoted above is great info.
    This is probably more info than anyone needs but it's interesting nonetheless:
    http://www.alcotec.com/us/en/educat...edge/understanding-the-alloys-of-aluminum.cfm

    I have to respectfully disagree with Jason though. Depending on what you want to do with the metal, extrusions can provide very good machinability. Next time you pour into tin cans pour a can full of extruded: window frame, plate, ladder, lawn furniture tubing, etc. Compare the machinability on your lathe and mill. Do some filing. I think you'll see much less gumming, plugging, and welding. The silicon in the 356 gives good flow but it messes up the machining. The fact that Kelly has the setup and desire to heat treat his 356 alloy gives him the best of both worlds, ie good castability and good machinability.

    Pete
     
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  10. Jason

    Jason Gold

    Pete is probably right. We say cast to cast, but you want to machine your scrap. I have pretty limited experience with aluminum, but I turn cast street light parts into some nicely machined stuff. Maybe i get lucky. My scrap comes from old city street lights, probably some grade A shit.

    Screenshot_20210315-225448_Gallery.jpg
     
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  11. Congratulations!

    You'll find if you quench an aluminum casting while still hot it will machine better. However, the tooling used and lubricant makes a lot of difference. I use kerosene for lubricant and it works great. For the lathe I hand grind a sharp tool steel point. I've not found any aluminum-specific carbide but tool steel lasts. For finish cuts I clean the cutter tip frequently by popping off the welded point. But light cuts with lubricant do great. I generally machine the entire groove in v-belt pulleys and get a nice slick finish.

    The main thing wrong with soda cans for me is it takes much longer to get a pound of ingot. Much longer. I've melted thousands of cans and have quit because of the time required. I get good castings from them, however. You can mix extruded ingots with ingots from cast scrap and get cast like results so if you're short of cast scrap just mix a little extruded in.

    Others disagree, but remelting your soup can ingots will result in a less porous, better casting. I've proven that to myself through sectioning and polishing.

    Your best teacher is experience, just keep trying, keep casting, and you'll learn what you like and what works for you.
     
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  12. Shawno

    Shawno Copper

    Thanks for the input. One of my goals out of this (recent motivation) was to make a large drive wheel for a 2x72 sander. Since this project was dragging out, I came up with one other ways but still need the smaller pulleys, hence the soup can castings yesterday. Not mentioned in my list of possible factors above was my tool bit geometry (oldironfarmer) so I have lots to experiment with. Although the tool I used turns regular aluminum great, it is not the geometry for aluminum. And I tried both steel and carbide, same thing so I will fix that too.

    I will report back. If I have to remelt those castings, that can happen. I remember reading something about gas injection to improve the melt....Argon? Need to go read that again. I am pretty sure there are threads on this forum regarding that since this is where I get most of my info from :)
    Once I find the propane tank to raise my lid, then I will need to take a sabatical to let the refractory dry. Honestly though, the crucible, with lifting and tilting tabs built in, is super easy to handle.....I picture the graphite being a little more difficult (precarious) and the tools being a little more elaborate than me bending a 1/4" rod yesterday for mine. Anything wrong with doing bulk melts in the steel to make ingots, then the final melts in the graphite? Especially since remelting seems to improve the quality....mmmmmm

    Jason, is that photo one of your casts? That looks nice!
    Thanks Pete too....I will try a solid cast of pop cans, then some mixes...see what happens. I am thinking my biggest error yesterday was the heat....it was not a concern for me and in fact, thought more was better. I don't know how to judge the "lean" so need to go research that too.....

    Looks like actually melting things is just the start rather than the finish.. oh oh! ;)

    All good.
    Cheers!
     
  13. Jason

    Jason Gold

    Yup! That aluminium block was the base of a city street light. Poured in a small soup can then milled it to use as a square block welding that bronze. When material is next to free, I dont mind sweeping up the floor. I have turned some soup can castings on the lathe and found it to be gummy and porosity was meh. I probably over heated the melt. I might try remelting again and see what happens. I hate cans because they are so much work, but would be willing to try and see how it machines. Let us know what you experience.

    I've got a buddy here with trashcans of extruded scrap chunks from his haas lathe. I keep meaning to load up the car and melt down a bunch of his crap, but I've been busy. The shavings he can keep.
     
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  14. dennis

    dennis Silver

    Perhaps melt down the cans with zinc, to make ZA-12/27?

    Those alloys are reputed to cast well....

    I received some ready-processed Can-demonium recently, so that will go in a pot with some zinc when I get the Barbie up and running. ("Fire up the Barbie" is a common phrase among some people I know. )
     
  15. Petee716

    Petee716 Gold Banner Member

    I'll take the liberty of answering for Kelly and say yes, this is correct. Unless you have specific provisions and reasons for holding, prolonged exposure to the atmosphere and the potential for overheating are unhelpful. Your metal melts at say, 675C. Your furnace is much hotter than that. Your melt, for all practical purposes, is no hotter than 675 until it's all molten which takes some minutes. Once it's all molten, the melt temperature starts shooting up very rapidly and the next thing you know you're up to 850 or whatever. Sometimes you need the metal hotter to fill certain areas of the mold or some other reason and you have to make a tradeoff (we're backyarders not metallurgists after all), but for the most part it's better to pour as soon as you can.
    If you're aiming for turning and milling stock, pour as many different sizes and lengths as you can. It will save you tons of hogging time.

    Pete
     
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  16. Shawno

    Shawno Copper

    Maybe a stupid question but where does one find Zinc?
     
  17. Shawno

    Shawno Copper

    Soooo, if I remelt what I did yesterday, and do as you say, does it reset the metal? Or since I may have contaminated it with overheating, how do I "fix" it? Or is that where the earlier statements made come in, re, second melts being better than the first....?

    I don't think my heat gun goes up that high so it will be a visual check of the pot to see when to pour.
     
  18. dennis

    dennis Silver

    Scrap metal yards, tire-changing places (zinc wheel weights), places that service boats (zinc anodes), eBay, and finally, rotometals.com.

    Zinc alloys are among the more commonplace metals in die castings.
     
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  19. Petee716

    Petee716 Gold Banner Member

    I can only guess. Oldironfarmers experience seems to indicate yes. I don't think all of the hydrogen will ever leave the aluminum, or even a majority of it without doing something to it outside of our abilities in the shed. It is pretty much saturated with it. What I think we do get is super-saturation. The hotter we get and the more time exposed, the more hydrogen goes into solution. Then, as the metal cools, the excess hydrogen starts coming out of solution and your casting solidifies and ends up looking like an aerobar (do you still have those in Canada? Lol.)

    Pete
     
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  20. FishbonzWV

    FishbonzWV Silver Banner Member

    If you have ingots that are so laden with hydrogen that it forms bubbles and you re-melt them, those bubbles will effervesce out. If you watch the melt closely as the ingots hot short and dissolve, you can see the bubbles pop on the surface. Been there many times until I learned to control my burner.
     
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