Cast iron?

I've been working on getting cast iron into my tool box for a few months now.

Here's where, if interested, you can find the background info that has been previously posted :

There's a YouTube playlist with some video covering parts of the cast iron project. More will be added to it later if/when I find time for editing:

https://youtube.com/playlist?list=PLo6k_ZP-VFj7LpFVo2xZbJdc5gS-DgsIf&si=DCq8OntDEqBfb589

Building the pouring shank and tongs for my Morgan A12, my road trip to the foundry supplier with stops at a couple other forum member's shops, and making ~450# of iron rated greensand are already covered in the upcoming projects thread starting here:

https://forums.thehomefoundry.org/i...-on-wanting-to-work-on.2781/page-2#post-54671

So, what's new then?

I made a few molds of patterns I had lying around for my first test pour. Sprue covers, pattern rappers, and a skull shaped ashtray. The sand still felt quite wet, so I let those molds sit for a couple of weeks to dry out more.

Last week, I baked my crucible at 250F for 3 hours to make sure it was completely dry, then I used HT1's tip for preparing new crucibles as seen here
(https://forums.thehomefoundry.org/index.php?threads/bubbling-blistering-crucible.2998/#post-55020 - pics of my results a few posts later) - seal it up in a hot furnace that's just been shut down, for an hour, to get it glowing red hot as slowly as possible, then fire up the furnace and bring it to operating temperature, shut down, and seal up the furnace overnight.

This was a good excuse to get my big old castable refractory furnace fired up and dust off the optional oil burner plumbing for my oversized Moya burner. I got it running but preheating it so the diesel drips would burn well was harder to get done than I remembered. I guess the smaller low mass propane furnace has spoiled me. But it did work.

Then a couple days later I got worried I'd have way too much metal and rammed up another pattern for a small maple leaf decoration that I had handy, and a chill wedge mold, and a greensand ingot mold.

So, finally Saturday was the day. I decided to use the small furnace as I knew I could get it hot enough easily and didn't want to be worrying about getting the bigger furnace up to temp on top of all the other new issues and concerns I might have to face. I don't plan to do that often, as I'm sure iron temps will take a heavy toll on the 2600 rated ceramic fiber blanket behind the thin layer of Satanite before too many melts go by.

I'd been told about the insane next level heat that will make your belt buckle brand you on your belly through your leathers which comes off a cast iron furnace/crucible, so I ditched my belt and emptied my pockets and wore extra layers of PPE, some of which I'd never tried before. Namely, chaps. I wore a set of leather ones, tied the straps the around my waist thinking that'd hold them up. Then on went the leather spats I always wear. Over that, the aluminized chaps I got from Bldr J. They just velcro shut up the back. Then my spare leather apron, then my leather welding sleeves, then my leather coat, then my usual leather apron.

Then I lit the furnace, but the wardrobe malfunctions had already begun. Beginning with the very bottom layer, the leather chaps. The straps tied around my waist with immediately started falling down and trying to pull my beltless pants with them, so I was trying to pull them back up the whole time... With heavy gloves on and the wardrobe malfunction happening under multiple other layers... Not fun. Eventually one of the aluminized chaps' velcro came undone, so I tore off the other as well and tossed them aside. Then the neck strap for my normal (outer) apron came unsewed from the apron and it fell off. By the time I poureed, my remaining chaps were just about down around my ankles!





This was very distracting, not what I'd hoped for. In the end I'm pretty sure I poured it a little too cold. Firstly, after adding some borax for flux and perlite as a slag coagulant (if you know, let me know if I can do better or should do different), I wound up having to skim off just about half of what was in the crucible if not more than half, to get down to the liquid iron. (Also found out the slim tool I built is a bit awkward to use, so I'll have to do some grinding on it so it stops getting in its own way when I try to skim.)

I assumed that foamy scum was dross and slag, but maybe it was just not quite fully melted iron? Maybe I should have tried to give it more heat before that skim, but I was just *done* messing around with my PPE while also trying to do this for my first time. I added 40g of 75% ferrosilicon, weighed out ahead of time based on sketchy google searches and my 20# charge of busted up brake rotor iron. But I must have skimmed off 10# of junk...

So I only had enough metal for the first 3 molds. Poured the smaller ones first, the sprue covers and rappers. Assumed they filled, and poured the ashtray. The cold riser on its far side never filled so that's where I dumped the last of the metal I could, though by then it was getting slushy. I figured the ashtray mold was a write-off. Then I tried to scrape out as much of the junk left in the crucible as possible and returned it to the furnace and shut everything down for the night.



Next afternoon I opened up the molds and as it turns out I had it all backwards - the molds I assumed filled had not, but I did have a complete cast iron ashtray! Since this was a test pour, I consider them all successful even though not all the castings came out. Hopefully I can learn something from the ones that didn't fill.



Next time I'll keep my belt on and trust my 3 layers of leather to keep its buckle cool, athen I can tie the chaps straps to the belt so they stay up and let me focus on the melt!

The good news, no chill wedge to check, but everything I have checked that was inside the molds came out as nice grey iron from what I can tell. The only chill/white iron I could find was on a small puddle that froze on top of the cope





Next time I'll try to do a little better, pour hotter. Still, stoked that this worked as well as it did. Any tips would be most appreciated!

Jeff

 

Wow, I'd never have come up with that. "Outside the box", but so simple! Thanks Pete.

Jeff

 

I weighed the iron I poured. For what it's worth, I didn't lose half of it, actually more like a quarter. But by volume at the time it seemed like more, surprisingly bubbly foamy stuff. Surprising to me anyway. I took a closer look at the junk I skimmed off too, seems way less dense than iron and breaks up easily but there's also a bit of iron that was mixed up in it.

Jeff

 

Thanks Rob. The heat wasn't as bad as the bright, I sure was glad Bill Jurgenson set me up with the dark shaded face shields along with his hard hats and leathers etc. Glad I had a layer or 2 of leather still covering me up most everywhere that faces the furnace and crucible though. I had double aprons and double chaps on so I could afford to lose a set of each I might do the double aprons again, it didn't impede my movement or anything and I didn't get cooked. But just one layer of the chaps I think. The apron that fell apart is long enough to cover the top of my spats, so I've never considered using any of the chaps before this. But if I don't break them out for cast iron, why even keep them around?

All the dried up cooked greensand is still in my wheelbarrow, but I'll be sure to report back once I mull it.

Jeff

 

Thanks Rotarysmp! I did get sparks, took me a minute to notice because my apron was falling apart just then, but when I did see them that's when I went to get ready to pour. But it took longer than I expected. I had the furnace open for quite a while, so long, losing heat. By the time I added ferrosilicon and skimmed off a little more, the sparks had long since stopped. Next time I'll skim, then close the lid again and heat it back up first before proceeding... I know you already saw this, but here's a video of the casting session for anyone else who's interested and/or able to provide additional useful feedback. Watching it back was what made me quite sure I poured too cold:



I do also wonder though if, being used to petrobond, I rammed the molds too hard and gave myself permeability issues that contributed to the first 2 smaller molds not filling. I used the pointed vent wire poked down through the cope, but I believe that does more to allow steam occuring in the sand adjacent the mold cavity an easy exit than it does to help displace air and gases from actually inside the cavity. The sand has 10% clay and the molds seemed really hard when I was cutting pouring basins and gating. The ashtray mold that sort of did fill had a cold riser on the far side that gases inside the cavity could escape through (not that any metal made it that far before I poured the rest of the iron down it)...

Said I'd report back on this. I ran the used sand through the muller, adding a little water at a time until it felt right. The green strength still seems good to me, but of course I'm just going by feel - I don't have one of those 400-1 sand testing machines like the supplier has to really quantify that. I won't be using it to make molds again until I've gone through the rest of the barrel of virgin sand, which could take a while. I have a second barrel I'm keeping the remulled sand in until then. Then I'll cycle it back from the second barrel into the first. Hopefully delaying reusing the same sand over and over again as much as possible will extend its lifespan? I don't know if the barrel seals well enough to keep it from drying out for that long, but I'll find out.

Jeff

 

Appreciate the tips, thanks!

Jeff

 

7 back to back melts today, all one mold per pour. 6 came out good but we were a little short on the biggest one. This time I used my oil furnace not the kaowool and Satanite one and done propane melter. I started preheating it half an hour before the artist arrived using propane easing into waste Jet fuel, then switching over to a mix of diesel and WMO later, and with the furnace nice and hot the oversized Moya/Brute-like drip burner worked better than it ever has before.

All open molds that I did not ram up. The patterns were just squares and rectangles of XPS, with draft cut on the sides.

The woman who did ram them up came out from Montreal and is making a bunch of these rectangular slabs of different metals with the items that were melted to make them stamped into the metal... That's why it was one melt per pour; each piece has to only have the specific scrap metal pieces in it that she brought with her, pre-weighed and pre-smashed up.

She's already got a bunch of these plaques or tiles or whatever you'd call then done in pewter, brass and aluminum, but her usual foundry guy doesn't do cast iron. Here's a screenshot of one of her pewter ones.



If cast iron poured in open molds will actually accept letter stamp impressions, she wants to come back and make 8 more before the end of July. Thankfully not all on the same day, as I'm medium rare at this point after pouring 7!














Jeff

 

As long as the iron is soft gray they should stamp ok but probably shouldn't expect the depth and definition achieved in pewter on an as-cast iron surface. Also, they better be well support on the backside to avoid breaking them. Is the last picture feedstock or a plaque broken by a stamping attempt?

7 iron pours is a lot. Congrats on that. Any idea how many lbs of iron and how much fuel burned? How long was the average melt?

As an aside, your furnace looks to be pretty close to that wood frame wall, especially for when the lid swings open on a white-hot iron melt. Don't burn your foundry down!

Best,
Kelly

 

Thanks Kelly. I definitely don't want to burn down my shed! Already thinking about steps I can take to make things safer and more comfortable long term, and also about quick improvised measures I can have in place before the next session. One of them will be simply doing fewer melts per session, but I might be able to cover up a bit more wall with some sheet metal.

We were working from just after 9:30AM (starting with a preheated furnace, mind) and finished the 7th pour right at 5pm, with one mid day break to cool down, maybe half an hour long. So about an hour per A12 melt.

I think the biggest pour was a 22 pound charge, but Maggy has notes on all that and I may be able to verify that later.

Other than a little propane for starters we went through 10L of jet fuel first, then another, I want to say, 15L or so of diesel mixed with WMO. That might not be right; I didn't record that info at the time. Invariably my hanging oil tank ran dry right when the melt was almost ready to skim, so I'll try and figure out the volume of that tank when I get a chance, that will be pretty close to what I need per melt, or realistically a little under. It's a good deal smaller than the 1972 puke yellow thrift store coffee urn aka heated waste oil tank I want to replace it with though. But I want to put a better tap on that one than the flimsy little plastic one it came with.

I still might not have had enough heat to fill a proper mold with a sprue and gating system on some of these melts, certainly the one that poured short was also a colder pour. But it was fluid enough on the rest for these open molds.. Clarke Easterling (Windy Hill foundry) told me the slag should have become a hard crust by the time the iron is hot enough to pour. I might have experienced a little of that on a couple of these melts, but for others it was more like skimming off foamy goo.

She took the couple ingots home too, to experiment with patinas and stamping, and they did take the stamps well. But she says the plates are harder to stamp - not as thick and demolded sooner explains that, I suppose. She asked if using more ferrosilicon next time would help that. I told her we can try it, but if we could use 2 part molds and leave them in there to cool down slowly, that might help more. But that might not be practical for her timeline on the remaining 8 pieces.

The broken piece is the biggest one, which we short poured. But on my screen it's the second last pic - are we talking about the same image? That one didn't go well, the crucible stuck to the plinth and the plinth wouldn't fit through my pouring shank... I had to pour using the liftout tongs after we wasted at least a minute failing to knock the piece of firebrick off, allowing the melt to cool and cause the cold shuts also visible on that pic... How the F are you supposed to get a piece of cardboard to last long enough to pick up and set the crucible back on it in a white hot furnace anyway? Easy enough when the furnace is cold. We even tried wet cardboard after seeing someone suggest that, but it dried up and burned and the ashes blew away before I even had the crucible picked up. Maybe if it was really soggy it'd buy me an extra second or two? We kept trying but for almost every melt Maggy had to knock the brick off the bottom of the crucible with a big hammer before I could set it in my pouring shank. I had to yank it off the plinth again today when I went out to mull and tidy up. Furnace was still warm to the touch inside. Had me worried for a second that it was stuck for good, but it came free with a bit of gentle violent yanking.

Anyway, we broke that plate to have a look at the iron inside, plus she might want to remelt it because it is still made of the particular scrap iron items she'd hand picked previously. The broken plate appeared to to be grey throughout, for whatever that's worth. I'm not sure remelting it again will help make it any easier to stamp though.

Jeff

 

I think a sheet metal barrier with air gap to combustible surfaces to shield from the radiant heat would help. On your previous video it looked like you may have had something like that between the furnace and the wall. I'd imagine a stack of bricks or cinder blocks would do the job as well. Didn't you get a pile of fire brick from your artist friend? Might be a good place to store them. Aside from that, maybe remove any loose combustible items in the vicinity. If you had a crucible failure that dumped 20lbs+ of molten iron on the floor, those plastic buckets would become fuel and lots of flame and black nauseous smoke and could get out of control very quickly. It's not when things go right......it's when they go wrong that the disasters occur.

I'll bet that white hot lid staring directly at you when you open the furnace is attention getting! A lid that stays pointed at the ground instead would probably be more comfortable but require a lot more floor space.

That's quite the casting session, especially in iron. -Good job.

Would have to help slow the cooling but use twice as much sand.......as long as you have it.

Yes, sorry last and also as a thumbnail at bottom.

I think I remember Melterskelter ultimately buying a bag of graphite from a farm supply store and sprinkling that on the plinth. His melts melted the glaze on the crucible which then ran down onto the plinth and glued the crucible to it. Might be a good question for Clark.

Best,
Kelly

 

Thanks again for the thoughts, I'm always looking for ways to improve things.

Oh, the lid of the castable refractory furnace we used for the long session does face the ground, it wasn't the same little kaowool and Satanite melter from the video of the first melt where the lid does flip up. That one's easy to get heated up fast so I used it for the first one and done melt just to have the experience without much trouble, but I think a full day of iron casting in that one would require a significant relining job afterwards, whereas the heavier furnace was built with iron capability in mind. Its lid does have to swivel over top of the burner and fuel lines though, because of the wall behind it preventing swinging it the opposite way as I intended when I built it years ago. Not ideal, but I have a piece of kaowool that I lay on top of the burner and lines when the lid is open to shield them.

Jeff

 

I hung up a piece of sheet metal next to the raging fire as Kelly suggested, great idea, thanks! It's only an improvised solution for now, but it got us through today's melts.





72 pounds of iron melted, 4 more open molds poured. She didn't go for the idea of the 2 part molds, her patterns were all thicker than the castings she wanted, designed with these open molds in mind and consistent with the plates she's had cast in other metals for this series of pieces. Maybe if she does another series.

I did convince her to try leaving them with me to cool off overnight in their molds. I don't know if it'll help keep them soft enough to letter stamp - they're open molds after all. But they're thick enough castings that she can grind down well past the surface to look for softer iron to hopefully be able to stamp "4 piggy banks", "2 kettles", "3 small skillets" etc. into, that might work. If not, we'll call our friend Jacques the blacksmith. He has a bigger hammer.

Thanks for the ideas about stuck crucibles. For what it's worth, we figured out the wet cardboard trick. It has to be really soggy, not just damp. I tossed some pre-cut squares in a bucket of water when I got up his morning and let them soak til we needed them. No issues this time with stuck crucibles.















I'm cooked, time for bed!

Jeff