First iron melt - Real time

Pete,

Anxious to see your casting pics. I guess those are the brushes from the blower motor. Ya, they don’t look good!

A few comments.

You used a lot more FeSi than needed. I think about 1 ounce per fifty pounds (1:800) is the right mix. Too much and you.can get excessive shrinkage etc.

For FeSi to benefit you, no more than 5 mins should elapse from time of inoculation to pour.

There is no need to wrap it in paper and plunge it. It erupted as the air in the bag exploded from expansion due to heating. Probably not moisture. I just use a long handle shovel and drop the FeSi onto the recently skimmed pot. If the is slag on top, the FeSi won’t get to the molten iron.

You need to stir the pot after adding Fe Si. I use a 1/2” graphite stick held in a steel bar. The graphite stick is surprisingly tough. A few good swirls will do.

Thick slag is expected. On a fifty pound melt the layer might be a 1/2 to 1 inch thick. Skimming late in the melt when the metal is good and hot seems like it works better to get the iron to dribble out of the slag on the skimmer.

I have several skimmers—-heavy duty with a bent handle, straight with a heat shield to protect my hand, small curved to fit the contour of the crucible for final cleanup.

Sooting the skimmer makes separation of the slag easier after skimming. A 2 pound hammer will usually crack off the slag.

I am sorry that I forget what burner you are using. But having it tuned just right can make the difference between a 50 minute and a 100 minute melt as the difference between the flame temp and melting temp of iron is relatively (compared to Al, bronze, brass, lead etc) small.

Hey you got it done. Sure the first few melts are usually a little raggedy as there’s a lot to keep in mind.

Denis

 

Still in my jammies lol!

 

I'm going way back
we used to add something to the Cast Fe heats to clump up the slag, and just pulled it out with a rod bent to 90 degrees, it was something like vermiculite or kitty litter... I really think it was vermiculite, you ended up with a clumpy ball like a hot corn ball, but it snatched all the slag no problem


V/r HT1

 

Dolomite lime is an iron flux, maybe that's what it was.


Pete: Looking forward to your results with the castings and furnace construction details too. I've been skimming and adding the ferrosilicon to the top and stirring in with a steel bar: it melts very quickly with no pyrotechnics.

 

Sorry the pictures aren't sorted.


We're looking at a link arm for the power feed leadscrew and the compound. Drag side showing.



Cope side of the compound casing shown with the original broken part. Depth of cavities in red. I believe those defects are from slag entering the mold. They are evident on the blind riser as well. The stain is spit (poor man's pyrometer).
I'll get those cavities cleaned out with a die grinder before machining. Once the part is milled I'll repair whatever remains of them by brazing. I don't think they should compromise the part. Time will tell.




Cope side showing.



Some family pictures




A couple of interesting things here. First is the piping in the blind riser. Over 1" deep. The other is the metal that overflowed onto the top of the mold from the sprue. I had the 4x4 shown in the picture on top of the mold with a couple brake rotors on top and the metal hit it and some got underneath resulting in the charring. That metal is very smooth and was shiney when it cooled.



I've begun to machine the link arm. It seems fine. I test drilled several different areas of each mold and all is well.

Pete

 

Good work, for sure. Thickish casting tend not to harden as they cool slowly. You might just see some white iron when you break the thin base of the sprue. Might be only along an edge, But you might look for it. If there, try drilling or filing—-not likely. It is very likely to be present in the flash since flash quenches quickly.

Fairly marked piping might relate to high silicon levels causing increased shrinkage or not...

Denis

 

Those castings are great, you're moving along at rapid pace with your technology . I have a famous lathe brand and during some repair work discovered a few hidden, deep holes in the iron castings.

So Pete, was your furnace running off oil and had the refractory disc on top of the plinth for this iron run?. I cast a new refractory disc yesterday as I've had three test runs without it with various burn rates and air nozzles and just can't get iron to melt.

 

I went and looked it up, it's a product called Foseco Slax , still seems to be available as Slax 20 or SLAX 30, all I can find is ist is silicia based, and safe, non flamable
no idea save a foundry supply where you would get it.
if you do a google search,
tons of info on it if you google Foseco slax


V/r HT1

 

Foseco is the closest foundry supply company to me, I'll ask them about it, might be possible to get a small amount from them.

 

Thanks Denis. I've drilled various areas including that thin shiney area shown in the last pic and had no trouble drilling any of it. (Bear in mind that I've never machined cast iron in any capacity other than drilling and tapping so I'm just now learning how it behaves.) I've checked various areas with a file as well and although the file doesn't "skate", it doesn't peel and remove material like steel or aluminum would. I've begun milling the link arm. I milled the bottom flat surface, only about .015 per pass, and have flipped it and am getting ready to bore the though-hole. Hopefully there will be no surprises. So far so good.

What i find so interesting about the piping in that riser is that there is absolutely none in the riser of the other casting. Given that there are visible slag inclusions in that other riser, there might be other factors involved.

Thanks Mark. No disk this time. My previous disk which was 1" thick blu-ram developed some severe cracking a few burns back and has been discarded. I think I was a bit too cavalier about the drying and firing of the first one and paid the price. I made a new one but have not yet fired it. I've found that once my furnace has really soaked through with heat I can cover my exhause hole almost entirely, to the point where visible flames are coming out between the body and lid, without any negative effects on combustion. This seems to really seal the deal so to speak and keeps that heat in.
My fuel on this burn was a bastard mixture of whatever was in my tank but it was primarily diesel, probably 90%.

Pete

 

The piping in one and not the other is interesting. They were from the same melt?

Soft iron should file very easily—-just like common structural angle iron or flat bar. Very thin sections like papery flash I would expect to quench hard.

As a general rule the cooler the iron as it flowed the shinier the finish. The shiny blob flowed as long as it could until it started to solidify is the way I would read that.

All of the above varies some depending on the individual alloy melted.

Denis.

 

Hmm that's one thing I haven't tried: reducing the lid opening diameter, which is 125mm or 5 inches at the moment. A throttled down exhaust might increase chamber pressure and boost burn speed. I wonder if the back pressure loaded down your blower motor, made it work harder and burnt the brushes out faster?.

 

Good job Pete. Drill a hole in a sample of your first melt and hang it up somewhere. It has been my experience with cast iron that when the failures show up it is rewarding to be able to reassure yourself that you have been successful in the past. And in your case success on the second melt is outstanding.

I use straight Borax when I slag a melt. I just dump a small ladle of the powder in the center of the crucible and use a round wooden dowel to scrape it off while the crucible is held in a fixture that I can tilt over a sand bed. It clumps up as HT1 describes. An old school method for cleaning a melt was to plunge Willow twigs into the metal to create agitation.

The slag inclusion has always been a problem. For cast iron, chocking the sprue is important because the lighter slag will rise there and the iron canl flow past. I use a glass mesh at the bottom of the sprue to catch any that gets to the bottom and have had good luck with that. I'll try to get a name later this morning.

 

Ht1 and ESC, the MSDS for Slax matches what you would expect for borax. The name suggests the ingredient too—-SLag + borAX = SLAX. Sounds like something to add to my process. Good tip. I’ll try straight borax next melt. If I can find some Slax, I’ll it as well.

Denis

 

The other possible and I think likely beneficial effect of reducing the lid opening may be it reduced air flow that was excessive and therefore cooling. Cutting back airflow and, with it, fuel flow has been good for my melt times and the converse has resulted in ridiculously long times.. The graph I imagine that describes furnace temperature must have a peak where air flow is optimal—too much and you actually blow the stream through the furnace before it has time to burn and too little results in inadequate energy release so the furnace dissipates heat faster than the flame adds it. For me my optimal fuel flow is .18 L per min of diesel. I would bet most of our furnaces won’t be very far from that equivalent fuel energy flow rate adjusted for BTU content of the various fuels. No proof of that, just offering the idea FWIW.

Denis

 

Black smoke is generally my indicator. I turn up the fuel until I'm getting black, then rein it in with air. Once I've run out of air capacity, I'm done turning up the fuel.
I learned just how balanced things are in the furnace when the blower quit. Flames and black smoke came out of everywhere in quantity including back through the burner and into my air hose extension. Could have been bad.
I dont have video of that but here's the pour. I can see now just how much slag got in there!


Pete

 

Sure, not to be argumentative, but I can balance my air based on smoke, sooting a coupon in the flame, or flame color at .10 L/m, .18, and .28L/m and so on. I will guarantee you it melts a lot faster at .18. If I were simply to turn my air to max, I’d probably be running “ balanced” but cold at .35 L/m. Just trying to raise the question...

Denis

 

I understand your point. The furnace probably has an ideal capacity for a given fuel and once that is reached additional fuel and air, although balanced, begin to deliver diminishing returns. At the risk of asking you to repeat yourself, how did you get to .18L? I know you have a flow meter but did you get to that figure by trial and error?

 

Trial and plenty of error. The flow meter has helped a lot, but is not essential. For a while I simply put my fuel can on a scale and measured its weight vs time. That works, but there is a necessary delay for each flow measurement. I gradually got a feel for what was too slow a flow and what was too high by observing melt times, rate of temp rise (I remember a few times late in the melt dropping temp over 10 mins due to tweaking flow for what I thought was more power!) and the feel of the heat when I opened the furnace. Over the last 20 melts I’ve pretty well nailed .18 as the optimal burn rate. Interestingly, that did not change appreciably when I went from a slightly smaller furnace to my current furnace.

You’ve done well to get iron melted, poured, and your mold filled!

Denis