PatJ You should watch this video. You will kick into the curb all your previous ideas about a high mass furnace. In the first part of the video there is a shot of the furnace and the lid. The furnace lid is made in two sections, the bottom part is made from fire bricks and the top is just a thick steel plate so more metal can be charged without swinging the lid away. What surprised me was that steel plate would be wasting a lot of energy because it is not insulated. Although it can’t be seen I would say the rest of the furnace would have fire bricks. Check out the size of the crucible, I would estimate that there would be at least 200 Kgs of iron in it. If they can melt large amounts of iron with a high mass furnace you should be able to melt small amounts of iron in your high mass furnace. The video is about a highly skilled molder making a copy of a highly ornate stove door. This video would have to be my all time favorite iron casting video. If anyone is a beginner to metal casting you should watch this video. Near the end of the video all the molds are poured and most of them erupt like a volcano. This is what happens when green sand is too wet! All the molds have plenty of vents but they will not save a mold if the sand is too wet. Hope you all enjoy this video.
Man that is a big crucible and furnace. It is difficult to tell how they are firing it. Natural gas, propane, fuel oil ? Those doors are out of this world. Makes you wonder how they made the patterns. And what is with the nails? Stiffening up the sand so it pulls out of the deep voids? I wonder if the parts they clean the sand off of are the same parts they poured. Seems like all that volcanic action would ruin the part, with partial fills, interrupted fills, etc. My guess on the furnace is that they get it hot and then repeatedly charge it/melt with it, so the mass is not critical since you only have to wait for it to heat up the first time. After that you are just heating the mass of the metal. Seems like that lid would degrade fairly quickly, such as happened when I use to use steel crucibles to melt aluminum, but it is hard to argue with success like that. One definitely does not want to see the eruptions though; that is bad news, but as you say he just got too much water in his sand mix. They probably got the new kid to mull the sand and they got a little overzealous with the water. Lots of dross coming off the top. I did not notice them using any additives. I will watch it again. I am going to do some serious iron melting in 2018; at least that is the plan. I am feeling good about iron this year, and I think I am ready and understand it. I do need to get my new furnace rammed. I got my storage shed cleaned up and shelving built to organize it, so now I have some elbow room to work on the new furnace and some new patterns I am making.
Nice trick using the nails to help retain the mold in the detailed webbed parting areas. Also like the simplicity of just molding the expendable sand follower and then parting it off and digging it out....nice example of free molding such a piece. I wonder how the molds that spit turned out? Seems like there must have been a pretty good pressure rise inside the mold to eject that much iron.....but sure didn't seem to phase them. Now there's someone that is completely unconcerned about pouring (even iron) on concrete floors, especially when they just turn the empty hot crucible upside down resting on its rim on the floor....LoL. Thanks for the vid. K
I had an ingot mold pop on me (not preheated hot enough), and it spit molten metal like that. I had on plenty of leather, but the problem was my gloves were over my jacket, so beads of molten iron went onto the jacket and then rolled down inside the gloves. I got some small but 3rd degree burns on my hands from the beads of metal. The beads basically vaporize flesh. And you thought iron spilled on concrete was bad. Concrete is the least of my concerns (but don't ask the wife about that). Would have been worse if the beads had be a little larger. Word to the wise; watch the open gloves. One local foundry person said depending on who is doing which part of a iron pour, they either tuck the gloves under the jacket, or not (I think she said the person tapping the cupolet has the gloves over the jacket, but the persons handling the ladle have gloves tucked inside the jacket).
I had a cold ingot mould spit a tiny drop of molten bronze onto the plastic face mask, you know the full face type used when grinding. It was visible for an instant right in front of my eyeball, then there was an audible "crack" and it disappeared. Looking at the completely undamaged plastic showed a cleaner spot in the dust on the front surface. I theorise the mask which had a generous layer of shop dust, allowed the surface dust/moisture to vapourize and pop the bronze off before it could melt the plastic. Not the sort of thing you could rely on long term.
PatJ This video always amazes me when I watch it. I was thinking the same thing, it must have been the sand mixer guy first day on the job. Have a look at when he restarts the furnace, the flames look like propane escaping from the second lid. Oil has a very rich yellow flame. In a small shop like that they would only pour once a day because it would a while to make all the molds, pour and shake out all the molding boxes. I could only see three employees and they dropped everything they were doing to help pour. It would be nice to know how long it took to melt that much iron and how much fuel they used. Kelly Now you know why I like this video so much. They do the same as I do after a iron melt they just put the crucible on the floor and not in the furnace. Mark It always pays to have a full face shield on when pouring.
I see what the nails are doing. Some of the doors are perforated, ie: they have holes in them, and the nails are securing the sand at the holes. And the crucible they are using is one of their smaller ones. Check out the one on the left at 12:13; now that is a nice sized crucible. Below is a commercial furnace chart, with the maximum crucible size being a #225 crucible, which is good for about 650 lbs of iron. The Morgan charts lists a #400 crucible for about 1,000 lbs of iron, with a height of 24" and a width of 20". And a BTU chart: 3412 BTU/hr = 1 KW Oil Burner Approximate Values: 1 gal/hr = 138,500 Btu/hr (40.59 kW) 2 gal/hr = 277,000 Btu/hr (81.18 kW) 3 gal/hr = 415,500 Btu/hr (121.77 kW) 4 gal/hr = 554,000 Btu/hr (162.36 kW) 5 gal/hr = 692,500 Btu/hr (202.96 kW) 6 gal/hr = 831,000 Btu/hr (243.55 kW) 7 gal/hr = 969,500 Btu/hr (284.14 kW) 8 gal/hr = 1,108,000 Btu/hr (324.73 kW) 9 gal/hr = 1,246,500 Btu/hr (365.32 kW) 10 gal/hr = 1,385,000 Btu/hr (405.92 kW) 11 gal/hr = 1,523,500 Btu/hr (446.51 kW) 12 gal/hr = 1,662,000 Btu/hr (487.10 kW) Heat Value of Materials: #2 Diesel = 138,500 BTU/gal So assuming at least a #400 crucible, then I would guess if it were operating off of oil (looks like it is actually running on natural gas) then it would probably be using in excess of 10 gal/hr, perhaps as much as 15-20 gal/hr, and I would guess 2-3 hours to melt 1,000 lbs of iron, probably in the 500-1,000 kW range. Repeat melts perhaps 1.5 hours and half as much fuel, or maybe less according to Clarke's repeat melt times. An induction melter would be much more efficient, but requires a significant equipment cost, and a very substantial electrical service. A large gas pipe would be cheap compared to large electrical service equipment. You would have to sell a lot of doors to keep up with expenses at that foundry. My guess is they make their money on the larger parts/pours given how slow and labor-intensive those door molds are to make. If you had an operation like Lodge, you could make 1,600 doors per hour on one molding line, and perhaps make some cash.
