Nothing special. Just a pic of a small test pour today, probably you all have seen the same scene a million times before. But I always like to see pictures of people casting on a forum. so here's a pic on a bright day in June. I don't know why I'm not out fishing. I just felt like pouring.
Yes it is Petee. Some bad/failure/sprue/old stuff mixed together. I wanted to cast something around a 3/4" steel rod that I had smoked in a candle flame to see how bad it would stick, and how bad it would chill. Was the carbon enough to act as a release? How much contraction would there be? I had done a few steel cores in aluminum casting, and you can get away with it up to a reasonable size, but iron likes steel. Would it be possible to knock the rod out? So that's what I did. Not much of a casting, but something to play with, and mostly making small ingots from old iron.
Let's play "What's the Outcome?" Will the tube pound out? <Yes> <No> I will enter a "no" guess. I think the iron will absorb the carbon soot and bond nicely to the iron so that even slicing the assembly in half will not allow extraction. But won't it be interesting to find out. Denis
Well the answer is ........No! (also Yes and Maybe!) The bar did not pound out without breaking the casting, but it did pound out, AND for the most part it did not fuse with the iron. It left a shiny finish on the casting bore. The bar has a marbled appearance from probably either slight oxide scale or leftover carbon. It cleaned off with dilute acid I say "for the most part did not fuse with the iron" because in two very small spots the finish on the bar is very slightly less smooth, and there is nearby a small cut. The cut however probably came from the shattered sharp chunks of chilled iron carbide casting as they flew off into space after I gave it a good smack with a hand sledge. I have only two of the pieces of the original casting, but it broke into three. I've been looking for the third piece, because that one may hold more clues about what happened. Test procedure: uh......that's a pretty dignified term for what I did. I basically just took the casting and put the long end of the bar into an oversized square hardy hole in my anvil. The only other hole, more appropriately round, was too small. Then I started tapping on the short end of the bar with a brass hammer. Gradually the taps increased in violence. I noticed eventually that despite being a brass hammer it was still mushrooming the bar. I don't think the bar had moved at all, but my test procedure was too ill-informed to have marked the bar on the south end to determine if it did. Well, since the bar was already deformed, no need for a brass hammer, and I switched to a bigger gun, a 4 pound convincer. That one likewise started out modestly tapping, but eventually irritation at the stubbornness of the subject won the day and I whacked it a good enough one to crack the casting. This just made me mad, so I gave it a better one to teach it a lesson. That was when the various pieces vacated the area, lesson learned. After that, I went looking for them. ########################## Notes to self: next time mark the rod. Next time use a close fitting round holed arbor. Next time try pressing it out with vise, or even, heh, your wood splitter.........no, strike that....
Oh yeah, conclusion......so far my feeling is that it's doable from a fusion perspective, but that shrinkage is the main contributor to seizing. That might be reversible. Put the unit in the freezer, remove and play a torch on the casting only, and see if it can be pressed out. Re. the carbon release: It was put on evenly, but sliding down vertically into the formed sand mold would have scraped some off, thus creating the small heat affected spots. Casting horizontally would have made placement with intact release much more sure. btw ESC, I smoke my ingot molds over the top of my furnace, and they never stick. I just hold them upside down with tongs over the glory hole for a minute or so after starting up with a slightly reducing burner -- my main purpose then actually is to assure they are dry, but the side benefit is the deposit of a soot release. I do the same with my slagging tools and anything likely to go into hot iron. Moisture is no fun.
Steel spokes cast hub and rim .....built in 1896 Still tight engine wait 8 ton So definitely shrinks onto the steel Neat exspariment though Todd
So a slight taper to the steel mandrel or even a split mandrel with a wedge in the center would make removal easier.
Ironsides, maybe...well the advantage (if it works) to a solid bar would be to actually make a finished and fitted bore without machining. Mark, that would probably work. Though the bore would be tapered. But that could be useful in itself. The above all works in aluminum, and was outlined in David Gingery's casting and machine building books in 1980 -- actually a key element in helping an amateur making a machine without starting with a machine.
According to this chart, iron and steel have similar thermal expansion coefficients while aluminium is about double......so unless you have a bar of tungsten or invar alloy lying around , the mandrel will need to be split or have some suitable geometry for extraction. The steel bar appears to have chilled the iron if the white appearance of the crack is anything to go by, might have handy properties for engine cylinder sleeves. https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html
That's true Mark. But actually aluminum shrinks worse, yet the bar is removable (up to a reasonable size and bury limit). And yes, cylinder stock for a small engine is exactly what I'm trying this out for in iron. I'm going to be trying again with more ideas for both the release agent, and differential heating for removing the bar. If the release agent is good, then it's really similar to the situation of a heat shrunk fit. Yes, also to chilled iron, actually it varied -- more on that later.
