So I made a video of a billet I poured from my last video and thought it would be full of air bubbles. Pouring from the top with water can cause a lot of turbulance but it was not the case with this billet.
We have used water on a plaster mold with a plexiglass front. We actually have it around here on vhs. We were horrified by the results. So much turbulence. Forced a rapid gating change. I do not think water behaves the same as molten iron but close enough to see turbulence. I believe the bubbles created during the pour penetrate the water further than they would on cast iron due to the surface tension of the iron vs water but bubbles are present around the top. The heat would also help drive bubbles higher in the casting. Just add a little extra metal on top to cut off before machining and you are gold!LOL We see this on sprues. The bottom is always cleaner than the top...except for the very bottom which is a sand trap for loose sand and first metal.
When I was going to Journeyman school they showed us AFS Videos from the 50's of molds being Xrayed as they poured, molten metal did not act at all as we had been taught. basically AFS knew their gating system was imperfect, but it worked better then trial and error. Cast Fe acts the most like water of all the common metals, Aluminum ( proper cast aluminum) the Least , Give Campbell his due , bottom feeding gets the best clean metal into a mold cavity, but it is often the hardest way to gate a casting, at least now we know crazy ideas like Pencil gating is insane V/r HT1
We tried some crazy stuff before we started doing simulations and found out how the metal really flows and acts. Im sure we sent the metal velocities through the roof trying to squeeze it into small channels to float out impurities above them...which was really just creating new trash at the exit. I spent many hours trying to determine just how to get the iron clean when in reality there is no substitution for proper slagging. If you pour dirty iron then no gating system is going to magically clean it up for you. If I had time I would try to recreate some of those just to see how bad they really were.LOL
