Jerrod Miller

Working it cold is inducing a lot of stresses. These stresses will lead to grain refinement upon normalizing (really it happens upon austenitizing). The reason normalizing refines the grains is because of the stresses induced from the heating and cooling. Stresses pile up in the crystal lattice. Too many and you get a failure, just right and you create a source for creating a new grain boundary when heated to austenitic. Working cold is a dangerous game. I know I have been bit a few times doing it, and I now prefer to work hot and normalize several times afterwards.

I'd bounce the ball of a ball-peen hammer around on it. If you can't find a difference that way anywhere on it, it is probably good enough. If that surface was going to get constant wear, like if it was a chute liner for aggregate, any soft spot could be hugely problematic, because any uneven wear leads to a lot more wear in that location which causes early failure. For an anvil like this I would think a hammer test would be sufficient. And when I say bounce a hammer over it, I mean start lightly and increase in force as you feel confident/necessary. Watch for any marring of the surf

It would be interesting to find out if there are some sections that are harder than others. I would suspect there are some softer sections in between the obvious paths there. Probably/hopefully not enough to worry about, but possibly noticeable.

I've done some pretty big stuff this way with 10-12 layers of shell. But it was a fairly industrial type of shell. The normal practice was 7-8 layers.

You can do it with multiple pours, too! Just make sure you have a layer of wax around the metal in the mold first. Once the wax is all melted out the metal will rattle around, so be careful handling it so you aren't hammering on the inside. Then it becomes really easy to have pre-heated metal in there, as you should always pre-heat investment shells before pouring. Alternatively, you could try a single pour with just a bit of liquid metal (I would think 50% would be the minimum liquid I'd start playing with). Put some shot or slugs of metal in the de-waxed shell, and le them heat up with

Personally I wouldn't much bother with a sub-critical temp if your only goal is grain refinement. But if you are also going for softening then it is helpful. As Alan saaid though, do a break test and you'll really know what is important.

I just saw you post about induction forges, and noticed that the one you say is like yours is 15kW. I assumed 3kW when I was doing the math (as noted in that post). At 15kW I would be super tempted to use that to melt with! Figure it should get 30-45 pounds at once! Probably doesn't have the duty cycle need based on the specs on Amazon though. Bummer.

Yeah, now that I think about it, maybe it would be best to pour the handle solo first. Then take that and put it in the mold to make the other spacer. Then the third mold is the final product. This way there are a couple really good opportunities to get experience with molding and pouring 20 pounds of brass at a time before the final run. I honestly tried to download a 3D model of Bobba Fett's helmet, but couldn't find anything that played well with Solidworks. I now have several that show up in Solidworks, but nothing that allows for feature recognition, just surfaces. I wa

Pre-heating would be ideal, but becomes very difficult with sand casting. A ceramic mold would be the better way, but MUCH more difficult to DIY. A bit, but I would still recommend a mechanical shape to help lock it in.

Something more like this. Size and sculpt it appropriately. This would put the worst seams on the very bottom, so you wouldn't see it when sitting on the floor. You may still get a visible seam around the top of the helmet where the handle comes out.

OK, here is a VERY rough and crude sketch of it. The brass colored piece is the one you make first. Get it all cleaned up and it would go into the mold cavity as represented by the blue outline. The 3 smaller round protrusions will stick into the mold (sand, presumably) and hold up the larger cylinder to float in the middle of the cavity. When the second pour is done, there will be 3 protrusions out of it that will need to be cleaned up, 2 out the back of the "head", one down the "neck". The very bottom will also have a visible seam, but the 2 parts will definitely be solidly locked toget

There are various techniques to accomplish making a part in multiple pours. The one I would recommend the most for this project would be to first make a base/central slug. Then when you have that, it gets placed into a mold like a core and cast the second pour around it. This does require 2 patterns, and 2 molds, and a bit of time in between the castings. I've got a few things I have to get done this morning, but then I will try to put a couple drawings together to better explain it. It is a bit tricky and a single pour is definitely preferred, but that isn't always an option.

I am not familiar with that melting set-up, but there are definitely a couple things I can see from the pictures that are worth considering. In no particular order: I have no idea what those tongs are for; certainly not for pulling a full crucible out. Maybe adding metal to the crucible while it is in the furnace? You'll need a set of lifting tongs and a set-up for pouring. The insulation seems to be un-coated. For longevity you will want to coat it, even with a very thin layer of something. There is not a lot of room between the crucible and and the wall. Hard to

On a face like that I would think you would be better off heating it all up in one go with flame, then quenching it all at once. If you were doing induction it would be easier to do it in one progressive pass, but I suppose it is possible to do with flame too. Doing multiple passes would be less than ideal as each subsequent pass would mess with the heat treat of the previous pass. This would be very hard to do hand-held. If you had a method to control the torch and quenchant line travel that would be best. And doing the 2 torches with 3 rosebuds each was the most efficient w

You know those really big excavators like this one? Hitachi Excavator. I used to work at a foundry that made some tracks shoes for things like that. The kind where each track segment (track shoe) weighed a few hundred pounds. The section between the lugs was flame hardened to increase the wear resistance there. It took two specially build 3-rosebud heads (so 6 total rosebuds). Each torch had to be hooked to an array of 9 acetylene bottles (a 3x3 grid on a pallet for mobility) otherwise the draw on the tanks would be too much and it wouldn't work. This was done over a water thank that th