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Aluminum Casting experience anyone have any?

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  • Aluminum Casting experience anyone have any?

    Howdy. IS THERE ANY DIE MAKERS here?
    I read all the books available and I have built myself a casting furnace. Problem is I built it a year ago and just now getting to using it. I made it for charcoal and a blower, but now am going to use propane w/out blower. I have a PID controller I got for the powercoat oven, a thermocouple and a solonoid. I have a gas valve w.pilot but the flow is not high enough btu, so it has to be manned and monitored.
    I made the furnace with a 5 gallon bucket for form, and a hot water heater outside, 2200 degree refractory in the middle, outside that is a 55 gallon barrel with cer-wool
    inside and around the water heater. (double insulated for long term heats)
    I will have to lift the pot out real high. Has anyone ever put a plug valve in the bottom of a iron pot? I am thinking of it.
    How should I do it? will it swell and stick? should it be tapered to drop farther into the hole to seal when expanded? weighted?
    I am scared lifting and pouring the aluminum by myself. Standing behind a piece of tin, pulling a rod plug does not worry me as much. I read the post on aluminum blowing up on contact with water, and have built a tin-steel framed building to put it all in now. (thanks HSM)
    The thing I am wanting to do is cast metal in dies, pop them out into a bucket and cast some more.

    My real QUESTION is..
    IS THERE ANY DIE MAKERS here? What kind of metal do I need to make dies? the thickness? do they have to be preheated? cooled? can they be automated with a sprue cutter? The books don't touch any of this.

  • #2
    The Tool Engineer's Handbook specifies a hardened steel (416 - 460 bhn) with a "composition of 5% chrome, .9% silicon, 1%molybdenum, and .35% carbon with tungsten and vandium as optional constituents". They state that too soft a steel will allow the aluminum being cast to solder itself to the die. I did a small amount of work for a die cast company about 10 years ago, seems to me the dies had galleys in them for coolant.


    • #3
      Casting aluminum with die requires high pressure while the aluminum is still molten. I think this is beyond the means of most HSM.



      • #4
        X.. Thrud said my D2 steel was used for dies. I have about a 6 foot bar.. Problem is my portaband just squeals on it and barely will scratch it. I know my mill ain't gonna like it either.

        Rotate.. check out the die casting site on "A lot of Brass" they have a die casting pump made from turned fitted steel. (piston and cylinder) You got me thinking.. maybe the valve in the plug can be fitted too? a pump-valve with tapered top to seal off. I have not made the pot yet. I do have a piece of 8 inch pipe for it. Lift the plug fill the cylinder, allow the die to partially fill, then press the plug-piston and compress the molten aluminum?

        We built a resin casting setup at Dupont to make the pnenolic pcb used in satellite pcbs. Every time they used the system it would harden in the dowtherm heated pipes. Dissassemble the whole system to unstop.. kinda scary, with aluminum? I bet them pcb's cost a bunch thou..


        • #5
          There are spin cast machines that are not expensive out there.. Might look at how it is being done by them. Basically using the rotation of the table to get the pressure. I have seen it used for pot metal. Don't know about AL and how you would do it. Might be worth some thought.



          • #6
            <font face="Verdana, Arial" size="2">Originally posted by ibewgypsie:
            [B]X.. Thrud said my D2 steel was used for dies. I have about a 6 foot bar.. Problem is my portaband just squeals on it and barely will scratch it. I know my mill ain't gonna like it either.
            I machined quite a bit of D-2 when I had a gig for about ten years making extrusion dies for the wire and cable industry. Also used a lot of Inconel 718.
            Anyway, D-2 has a tendency to work harden in front of a dull cutter, this is compounded by the fact that it tends to gall on it's own chips. With sharp tooling and good chip evacuation, It's really not that bad to work with. I had pretty good luck using the old trichlorothane based "Tapfree" on it, but that's next to impossible to get any more (I've got a gallon stashed, I use it sparingly). Are you using a bi-metal blade in your saw?


            • #7
              Well the weed burner tip, PID controller, opto-22 relay, asco solonoid and two hydraulic needle valves (one for burner, one for pilot) work great together. If it ever gets below zero in my shop again I know how I can heat it.
              Man.. I moved the controller down to 80 degrees and zoom the metal building was that hot. My casting furnace is outside and wet at the moment (still working on the tin casting building), so redhot furnace is out of the question.
              I had my cutting regulator on it,It runs best at 15 pounds, has about a 18" blue flame. Throttle down (as low as it can go) is about a 8-10 inch flame with 3-4 inch yellow tips. I tried moving the pressure up and down but it needs a smaller orifice I think. #57 drill currently.
              I can post pictures as soon as the weather co-operates.

              X.. glad to hear about the D2.. I think this piece has been tempered. Maybe first thing to do is heat it up red and let it cool with the furnace slow. I have to temper the refractory anyways.


              • #8

                Looks like a molten aluminum squirt gun. Be very careful.



                • #9
                  yeah.. I want to stand behind something. The plug-piston will be inside at the bottom of the pot, no one around the discharge. I am still scratching my head and drawing that part. large mideval shield with eye hole? You know I got to metalflake it if I do.. ha ha.
                  I see something (in my head) dripping like a bad faucet.. drip drip drip.. molten aluminum. Ain't that a bad thought.. get ready to pour and its all gone.
                  I may build a couple of smaller crucibles to pour too..
                  I just think the 8dia x 16hi pot will be too much (too dangerous) for me by myself.
                  these guys in the books paint a pretty concept picture, but.. a guy could really get hurt. Yeah. I still got all my fingers too.
                  That's Why I like to ask questions.

                  (there are people already bringing me parts to reproduce and I ain't got a clue yet) I got the casting sand mixed thou.


                  • #10
                    Hi gypsie.As for the valve,lead pots for bullet and sinker molding have a pintle valve on the bottom so I don't see any reason you couldn't make one work for aluminum.The one on my pot has a taper and the wieght of the rod holds it closed with an ocasional drip or two.If you made the pot tall and skinny it would increase "head pressure" to give more pressure at the nozzle.Production bullet casters use a spin mould of some sort but I haven't seen one to tell you if it is a rotating mould that drops the cast bullet and resets for the next pour or if it is to increase pressure while pouring(probably the former).Good luck and be careful.i've had a lead pot erupt from dampness before and it aint pretty.We were really lucky we didn't get burned.I still don't remember how we didn't.


                    • #11
                      Hi Ibewgypsy,
                      I understand your trepidation, but before you go much further with new designs you really should melt some small amounts of metal to get a feel for it and learn the peculiarities about working with the molten aluminum. Sounds like you've put a lot of work in already and should be about there. I'm no die casting expert but I have poured ingots into metal molds. I think your success with this would depend entirely on the shapes you are casting. I think the shrinkage of the aluminum is about 7% so if your die has the appropriate draft angles it will pop itself out of the mold. If the mold is cool when you pour the metal, I think there will be little adhesion to the die but your surface finish will probably be more crystalline or mat flash finish. The difference in the coefficient of expansion and contraction will help unless your design "traps" your part in the mold. Still if you are new to it probably sand casting and lost foam casting would be good practice.
                      A couple of thoughts for you. You really should have the ability to adjust an air blower as well as the amount of gas you are burning. You can produce a lot of heat but you don't want to see any yellow flames and you don't want to see any flames coming out of the vent hole because you want it all burned inside. I'm not sure the bottom-pour method is going to be satisfactory because the dross is both on the top where you can skim it off, and the bottom because it sinks. Also once you unplug your crucible, can you stop the pour or does it all go down the drain? I've seen some steel pipe crucibles that look pretty good for aluminum. I use cast iron pots and I've done pours up to about a quart of metal. I should have used one of the available ceramic coatings because the wear and tear on cast iron is surprising. I wear both goggles and face shield and smock and welding gloves. I'm thinking of fashioning some sheet metal shoe covers. The thought of unlacing a molten boot isn't appealing. Your forge is probably cool to the touch in operation with your design, but having to lift the crucible very high seems like a problem. If you could hoist and trolley the crucible it might work. Otherwise it is nice to have it at a low work height. You may want to partially bury your forge to fix that. Having a comfortable and secure tool to handle the crucible is "crucial." I wouldn’t want to lift the crucible myself if it were very heavy and I don’t want it over waist high. Actually the closer you keep it to the ground the safer and less chance of splashing everywhere if you spill. I want the mold within a few steps so there isn’t much chance of tripping. I saw a good pipe crucible with simple “Jâ€‌ slots cut in the rim where a simple wire handle is inserted. Another wire tool is used to tip it for pouring. Here is a picture of a way that I don’t like, although I did like the design of his electric forge his methods are dangerous:

                      [This message has been edited by SJorgensen (edited 05-05-2003).]


                      • #12
                        I have only cast in sand using a crucible. Always had two people to pour. It is not a good idea to be alone when casting.

                        Have never seen or heard of a tap hole being plugged on the inside of a furnace for molten aluminum. The plugs that we used in the furnaces were on the outside of the furnace. They were tappered and counterweighted to keep them closed. They were made of a casting and a soft refractory cone was placed over the tappered cone producing a good seal in the tap hole.

                        Aluminum shrinks a good bit when it cools. The molds will have to be preheated. Don't know what you are going to cast but getting any kind of great detail on an aluminum casting without pressure or vacuum is going to be tough to do.

                        Good luck and don't get burned.



                        • #13
                          SJ.. thanks.. I have done silver casting via electromelt, lost wax casting and sand with purchased casting sand. I had about a 50 percent success rate with silver. Not real good but the successes were great.

                          I made my own sand this time, I hunted high and low for bentonite. I found it in kitty litter, the cheap kind. And it smells good.

                          I am engineering a valve for the bottom of the pot, one you can turn on and off. A fitted cylinder you can force down to push molten aluminum out under pressure. I am still in the thinking mode on this.

                          "a submerged casting die?"

                          I made a full length apron out of leather also. I hope I never need it's protection, but plan on wearing it. Also.. a green welding jacket. Also.. the shield is a ideal I have not gave up on.

                          Working (electrician) at wheland foundry was educational. YOU DON'T want molten metal around concrete, it'll jump 20 feet into the air and come back down in a shower. (guy on website was pouring on concrete)

                          Thanks for the help. It's all new to me.


                          • #14
                            <font face="Verdana, Arial" size="2">Originally posted by ibewgypsie:
                            [B] YOU DON'T want molten metal around concrete, it'll jump 20 feet into the air and come back down in a shower(B]</font>
                            That kind of sounds like fun actually. Jeez, I think I need more excitement in my life or something!

                            [This message has been edited by x39 (edited 05-05-2003).]


                            • #15
                              Not a die maker but I am a patternmaker (not journey level yet though. I'd be more concerned about a plug failure than spilling a large crucible as long as proper hoisting or lifting is used. As others have said I don't think you'll get acceptible results pouring into an open die. You need risers to get decent pressure and metal reserve. Since it sounds like you're relativly new to this I STRONGLY recomend experimenting with sand molds first. It's a lot easier to change the rigging on a pattern than on a die and I can tell you that everything doesn't go as planed the first time a pattern is cast even for people with years of experience. Patternmakers don't even try to figure it out, we depend on the foundry men to tell us how they want the pattern rigged and every foundry has his own opinion. For the sake of your own sanity cast smaller patterns in sand first. Also consider a hoist rather than a plug.