Degassing Tablets

Where the metal submits. Metallurgy to Melt point.
dallen
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Degassing Tablets

Post by dallen »

how many guys have gotten them bigo hard as rocks degassing tablets that Harrys is selling, not his fault there all like that, even the flux tablets from BCS. Well I put in an order to Legend Mining supply the other day and stumbled across a not large but about the size of a coffee cut mortar and pedestal made out of Cast Iron so I ordered it. Well it arrived yesterday pretty rough, but all in all your typical chinese Casting.

So I grabbed one of the tables and dropped it in, and commenced to pounding on it, well it wasn't not time I had it all in a nice fluffy white powder that is manageable to be for packing it in a little degassing tool I made . and I don't have to stand around scratching my butt trying to figure out how to smash the damn things up right when I need a teaspoon full of the stuff.

I'll get a picture up in a day or so. but I cleaned it up so its nice and smooth, cause I plan on casting a couple of them out of some Cast Iron, now I just gotta find a miniature baseball bat for the pedestal.
David and Charlie aka the shop monster

If life seems normal your not going fast enough" Mario Andrette
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Harry
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Re: Degassing Tablets

Post by Harry »

Yeah, those tablets are meant to be used whole in very large crucibles. Our range of crucibles is so pitifully small compared to what is used in industry so we got to work with what we can get. Good idea on the mortar and pestle though, might have to make one of those myself. Still trying to get things together for moving to iron. Finally got some new crucibles so I can donate one of the older #10s to be an iron pot.
I'd rather laugh with the sinners than cry with the saints the sinners are much more fun...
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dallen
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Re: Degassing Tablets

Post by dallen »

I found a degassing agent that is in a powder form, more granular then powder haven't gotten to use it yet, but hopefully in a day or two, have some work to do on the house first thou.

the granular form makes for easier proportioning of the chemical I will say that much, this is suppose to be a combined degasing /fluxing or drossing agent, with one pound of chemical per hundred pounds of molten aluminum, so you have to weigh it out, they say its pretty vigorous in its actions, and that its better to use to small application rather then one large one.

David
David and Charlie aka the shop monster

If life seems normal your not going fast enough" Mario Andrette
HT1
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Re: Degassing Tablets

Post by HT1 »

Give these guys a call and ask for Calcium hypoclorite. I got a case of it," technically "expired from work, I will never run out, and if I seems to be going bad, I can use it in the laundry. they will sell it powdered/ granular, all you have to do is weigh it into aluminum foil packets, and Walla! instant degasser, no fus no muss
dallen
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Location: Oklahoma

Re: Degassing Tablets

Post by dallen »

HT1 wrote:Give these guys a call and ask for Calcium hypoclorite. I got a case of it," technically "expired from work, I will never run out, and if I seems to be going bad, I can use it in the laundry. they will sell it powdered/ granular, all you have to do is weigh it into aluminum foil packets, and Walla! instant degasser, no fus no muss
name, number.
David and Charlie aka the shop monster

If life seems normal your not going fast enough" Mario Andrette
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Re: Degassing Tablets

Post by HT1 »

http://www.ritekem.com/ Sorry Senior moment
dallen
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Re: Degassing Tablets

Post by dallen »

thats ok I wake up in that state
David and Charlie aka the shop monster

If life seems normal your not going fast enough" Mario Andrette
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Harry
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Re: Degassing Tablets

Post by Harry »

I used some of the degassing tablets I have today. I made up a tool by welding a 1/2" x 3/8" bell to a piece of square tube. Using a 3/8" pipe nipple I wrap a small piece of foil around the outside and pinch the end closed. This can be dipped into a baggie of crushed degasser then the nipple removed and the other end closed off. It fits nicely into the bell and by packing it a little holds nice and tight.

I plunged this into the melt and held it at the bottom of the crucible, give a couple of slow swirls and wait until I can no longer feel the bubbling through the handle and pull. I dont see a whole lot of bubbles which surprised me, I thought it would bubble and gas like crazy. Not sure how effective it is or if it is fixing the micro gas porosity I have seen in machined pieces. The pieces I was casting today do not take machining so I wont know until I do some other castings. I was also a little surprised at how long it took for it to completely stop, even though I could not really see much for bubbling I could feel it in the handle and I could feel when it stopped. If I pulled before I felt it stop there would still be some degasser in the tool.

One thing that keeps coming to mind was Murray always saying to degass on the fall meaning pull the pot (or in the case of how I am doing it, cut the propane and open the lid of the furnace) then degass. My understanding here is that the melt wants to draw in gas as the temperature is climbing but not so much as it is falling. Can anyone confirm or debunk my take on this? If this indeed the case it seems to make sense to overheat slightly then take a little time in the degassing to bring the temperature back down to the desired pouring range.

Will be doing some parts for machining this weekend hopefully and will be able to see if this is indeed putting me on the right track. If it is then I will probably start degassing every melt whether it will be machined or not just to make sure every casting is as good as it can be.
I'd rather laugh with the sinners than cry with the saints the sinners are much more fun...
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Re: Degassing Tablets

Post by HT1 »

That sounds complicated, I dont understand.
I welded a 1.5 long piece of 3/4 dia pipe across the end of a piece of 3/8 rebar. looks like a T . I measure my degasser into a bit of aluminum foil, and stuff it into the pipe, I stop the furncae, open the lid, and degass the metal sitting in the furnace. if you take it out it will start to cool rapidly. in the furnace, it wont loose much heat. is don't stir, just put the degqasser in althe way to the bottom. it is not a real violent reaction, unless you put in too much degasser. plunge in half a hocky puck and it will make a real mess.


also, remember to preeheat the degasser, and the degasser rod. the degasser will pick up moisture, and we all know what happens when you put moisture in a bath of molten metal.

P.S. with that note on moisture everyone is storing their degasser in air tight containers???
dallen
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Re: Degassing Tablets

Post by dallen »

I welded a short 1.5 long piece of stainless steel tubing to a 1/4" rod, I used to plug one end then scoop it full of crushed Harry's degas tablet, then plug the other end with paper and plunge and stir.

now I only have to plug one end cause I plunged it into some cast iron and one end is plugged with C/I now.

I have also switched to the degas powder that I got from Small Foundry Supply and have been using it lately it is a very active with lots of bubbles so you have to be careful not to use too much. But I haven't used enough to really see a big difference yet.

even when I kept mine in a plastic bag I didn't see that it absorbed enough moisture to cause a problem, biggest problem I can see it what moisture it would absorb creating more hydrogen gas problems. But thats my expereiances.

I do like the degaser that I got from Small Foundry Supply even the stuff that I got for brass, prices seems ok at about 8.00 a pound for the amounts that I use for my melts.
David and Charlie aka the shop monster

If life seems normal your not going fast enough" Mario Andrette
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