So amongst all the activity with pouring aides, I decided to make an aluminum duty contact pouring ladle. Here’s the basic premise as borrowed from Campbell: A ladle with a plunger which is immersed through the surface of the melt and then the plunger is opened to fill from the bottom of the ladle. The ladle is filled to the shot size of the pour, the plunger is set, and then the ladle is set on the mold and opened. In my case, since it’s lost foam, I added the contact base to momentarily isolate the foam sprue from the ladle heat until the pour is triggered. This probably wouldn’t be necessary for green sand but might help prevent dislodging sand in the mouth of the sprue. The ability to clean the ladle after pours and keep the plunger from fouling will likely be the operative factors in how effective and reusable it is. To test the concept, I decided to start with one of my most familiar castings; the automotive water neck. With sprue, it weighs 1.3lbs. The ladle cup dimensions are 2.875” ID by 4” tall. It’s .063” wall. That’s about .65lbs of aluminum per inch of fill height. I’m figuring on filling it ~3” full. That will be a big improvement in metal usage as I usually had 1x-2x of the part weight in the cup, especially with the offset basin. I should be able to get 3-4 dips from a full A-10. Here it is welded up. Here’s the assembly. I haven’t decided if I’m going to make it spring loaded open so you hold the plunger closed with your thumb or spring loaded closed and trigger lever to open. Here’s the contact base. It’s just a piece of insulating fire brick (IFB) coated with moldable ceramic fiber (MCF) so it can withstand molten metal contact. Here’s the ladle on the contact base. I’m still fussing around with the plunger. I figure it will be a wear/expendable item with use, so it’s replaceable and threads onto the end of the plunger and is isolated from metal contact by the MCF. I’m experimenting with encasing metal and IFB in the MCF for the plunger seal. All of the ladle that sees metal contact will be media blasted and coated with Boron Nitride to prevent iron contamination of the melt and wetting by molten aluminum. As an added bonus, the 3” OD ladle fits through the furnace vent hole in my resistive electric furnace. That should make preheating easy. We’ll see how it works out. If it does well, I plan to make a 10lb shot size version that is 5” diameter by 7” Tall. It would have a capacity of about ~2lbs per inch of fill depth. Probably only one dip from my A-20, but if I fired up my A-60, probably 3-4 dips. Best, Kelly
You know... you could probably adapt your furnace to accept one of the bottom tap crucibles from an induction furnace. Imagine never having to lift a hot crucible again Plus melting under vacuum in an inert environment, bifilms would be a thing of the past. Makes me want to build one myself, but soo little time anymore...
Cool. I did something similar when I was pouring the pistons for the V8 in the permanent mold. I made the mistake of turning the nose from a mystery stainless? and it couldn't take the immersion and melted. I'll see if I can get a picture tomorrow. As far as controls go; I would think nomally closed, then lift to fill before submerging to avoid turbulence and then lift again to fill the mold/ pouring basin.
I would have it closed under spring tension. Not that there is any safe fail, but an incident that involves molten metal streaming out from the bottom of a laddle seems to me the less desireable option of the two.
At some point you are introducing oxygen into the melt front and creating 'bi-film unicorns or ... seriously, I don't get it. You draw from the bottom of the crucible into a void that is full of air, probably in a rather turbulent fashion through the plug. The only benefit I can see to that is possibly not drawing crud from the top of the melt. You are still splashing molten all into an oxygen rich chamber then pouring. Take what I say as clap trap as I really can't keep up with this bi-film concept and need to have more of a brain to accept the true relevance to porosity. No offence to anyone intended.
Well, I guess we'll have to see about that, but not according to Campbell and the rest of the Gurus Peedee. In fact, the purpose is just the opposite....to eliminate splashing and additional exposure to oxygen caused by a poorly controlled pouring stream from a furnace tap or crucible. Dip ladles in general are less turbulent means of transferring metal if they are dipped properly starting on their side. The procedure with the contact ladle would be to preheat the ladle, then with the plug closed, immerse the bottom of the ladle just below the surface of the melt. Then open the plug. With a fraction of an inch of head I wouldn't expect that to be a violent or turbulent event. Next you slowly immerse the ladle the rest of the way until you have reached the desired charge size, filling it like a riser in a mold would tranquilly fill during a pour. Then seal the plug, transport to the mold, set in place of above the sprue and open the plug into your well designed, naturally pressurized, counter gravity feed system. The biggest advantage for bifilm theory disciples is no pouring stream our splashing in the cup or basin, and it inherently has the zero velocity start of molten metal feed. I just want less initial pouring turbulence as I often have to hit a pouring basin in the middle of a large round flask and that can require excessive pouring heights with big crucibles. Best, Kelly
Not to hijack the thread, but just some thoughts to try to explain it to myself. Sometimes we get a porous mass in the Kush head or cone basin. This seems to be based on the amount of air available as an aid to combustion, because sometimes it is relatively calm. Whether or not this mass is Al2O3 from the melt or created by the turbulence, the agitation seems to raise it to the surface, because I have found fewer folded bifilms in lost foam than in my open cavity molds. Kelly has suggested that there is probably an absence of O2 at the front face of the metal as the foam is vaporized and so does not produce oxide film. Also the speed of the advancing melt may be below the sessile height of the metal and so preclude formation of oxides anywhere but the exterior of the casting. With the contact pouring ladle by immersing at less than sessile height drop while filling, that action would only produce the oxide film on the exterior of the molten metal as it lays against the side of ladle, and when discharged into the mold the only oxide might be on the face of the plunger. It should be much less than might be formed by an open pour. I would think there would be less turbulence if the plunger is open when the ladle is submerged, but the proof of a method will be the quality of the casting.
I did watch the video and saw the crucible with the hole in the bottom. Would be interested in seeing how they open and seal it. We did talk about a vacuum furnace before and I did briefly consider it at one point but I'm not up for building an induction system. I thought there was a possibility that the radiative energy from resistive electric could would work in the vacuum.....just not worth the pain to me......at least so far. Best, Kelly
When he is assembling the machine you can see the arm looking part he installs, that's the way it is sealed and actuated. Doesnt look like anything fancy. Just a flat faced disc on the end of a rod. No tapered seat...
Radiant energy will work better in a vacuum. But not so much you'd notice. Any air you don't heat lets the energy hit the crucible or other wall. By the time you get the walls hot they will radiate just fine as well.
One would think it needs to be like an automotive valve seat, two surfaces which meet at different angles. If you get some freezing you sure want the contact area to be small. A wedge away from the seat will be hot short and not stick quickly. A sphere and a cone meet that way.
I used the smallest punch flare I had to punch the hole and form the radius on the bottom of ladle. I was planning on building up some of the moldable ceramic fiber around a support washer and then grinding a 45 degree seat on it so it (point) contacted the radius. The moldable ceramic fiber can be compressed and conform so I was thinking light pressure would coin in the seat.....now whether it resists fouling.....dunno. Best, Kelly
I think most of the samples you show and for sure the cavities on the surface of my rims fall in the category of folded , or as I notice Campbell uses the term furled and unfurled bifilms. I sent a PM.
Managed to do a little more work on the ladle. Built up the plugs with moldable ceramic fiber and ground a chamfer on the seat, then coated them with Boron Nitride. Coated the rest with Boron Nitride. There’s a spring under the bolt. Advancing the bolt increases the preload on the plug/seat. I still need to build a detent on top the bolt head to hold the plug open. That’s all for today. Best, Kelly
Looking good! Do you keep boron nitride around? I've thought about buyinng some but it's pretty steep.
