Casting Aluminum Brackets for Kayak

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F.C.
Posts: 560
Joined: Sat Jun 04, 2011 10:28 am

Re: Casting Aluminum Brackets for Kayak

Post by F.C. »

I don't think you're understanding the suggestions I've offered. You know for a fact you're overheating the metal... then don't! Melt slower, watch for the pinkish hue, shut down, degas, and pour like I suggested. Learn to read temp by visual clues. Do some research on it. How else do you think they cast metal before there were pyrometers? They made a literal science out of reading metal temps based purely on visual clues. For instance, if you see your metal vibrating inside the crucible you've gotten the metal to a point of boiling. Vibrating "IS" boiling. Metal doesn't bubble like water when it boils... it vibrates, beginning with very mild quivers (which is simmering). When metal gets to a near state of boiling it loses it's pinkish hue inside the furnace due to the radiance of yellow heat from the furnace wall. If you see your crucible inner wall bubbling at the metal's edge you can pretty much assure yourself that crucible's temp is at 2000 degrees. This is extremely too hot for aluminum. All you want is an even PINK hue to your crucible (not pinkish, but PINK) inside the furnace. Once all the aluminum is liquid it, too, will develop a hue... that pinkish hue I'm referring to. At this point you need to shut off the flame, purge and skim (if you're using scrap with manganese, high zinc, and magnesium additives), then watch for that hue to disappear and pour.

I also don't think you understand what contaminated metal is... dirt will not harm your metal, and oils will flare off... contaminated means, you're using metals with alloys you're totally unfamiliar with and are prohibitive of producing a quality of cast you desire using the methods you have at hand. Those wheels are chocked full of magnesium and manganese, both will give you problems if not dealt with under strict controls. Not to mention the cast product you do end up getting not only will have gas bubbles but will also be extremely brittle. Pistons and crank case metals will give you similar issues, as well. But... degassing and lower temps with pistons and crank cases will give you a workable product. Those blue cakes will work for these metals. I've suggested you to try that blue cake and yet you adamantly affirm what you're using will do the job... or should, at least, which implies you're not going to go that route. Learning this trade requires experimentation. What won't work every time for you should give you a clue it just may not be what you ought to be using. Those blue cakes are cheap as candy... it won't hurt you to try it.

Inside that furnace you need your crucible encircled by the flame and your melt not exposed to the combustion of gas and air, this is why I suggest to leave the skin on the melt till you're ready to pour, this helps keep the metal protected from the furnace combustion elements. This is true regardless what metals you're melting down. And as for melting wheels to cast into ingot, expecting them to be "cleaner", does not eliminate the difficult alloys, nor does it purify the aluminum. The ingots you make will have the same properties as the metal you've been casting. Shit in... shit out... in other words. Don't know how to explain it any clearer than that... :)
dallen
Posts: 2321
Joined: Sat Jun 04, 2011 9:06 am
Location: Oklahoma

Re: Casting Aluminum Brackets for Kayak

Post by dallen »

I fired up and melted a crucible of aluminum today, I watched the furnace and when all the metal that I had in the crucible was melted added some more so that I would have enough to pour the same part that I had posted a photo of a couple days ago. I watched the melt and I guess my color is off cause I never really saw any pink, but as the melt progressed I did back the burner down as the temp in the furnace came up.

I also went and got a 2000 flushes bar as you didn't say which one you use, I broke off a corner and put it in the tool that I had made and have been using, I didn't this before removing the curcible from the furnace and I left the pot sit for a few minutes after the stuff stopped bubbling.

the crucible had lost almost all of the color from being heated up in the furnace by the time that I poured and like you said it had a skin on the flowing metal as it entered the mold and also when I poured what was left into a section of 4 inch pipe.

I faced off one of the ends to see how the metal looked and I will say its a lot better then some of what I have been getting lately,

the black specks are dirt from where I ran my thumb across it,
Image

if weather permits I'll see about trying to dial the burner down some more.

DA
David and Charlie aka the shop monster

If life seems normal your not going fast enough" Mario Andrette
F.C.
Posts: 560
Joined: Sat Jun 04, 2011 10:28 am

Re: Casting Aluminum Brackets for Kayak

Post by F.C. »

WhooOOOOOHOOOOO!!! :lol: Congrats my friend... Now, you're learning. The visual acuities will take some time to develop. Photos don't do justice in showing folks what to look for... ya just about have to be stand'n there watch'n and memorizing as it's occurring to burn it (so to speak) to memory. Dial in all the other issues and all you'll have left is to witness what occurs within the pot, during the pour, etc., and burn every successful event to memory. Once you get far enough down that road of self experimentation you'll appreciate the two decades of results and conditions I've stuffed into my head from thousands of trial and error pours. The more you learn, the less fuel and time you waste. Start first with a full understanding what you have in your sand, too much?, too little?, need an additive??? Do research and be trusting of those with experience that can give you some insight how to improve your processes.

Then focus on your furnace, burner, fuel/air adjustments and control devices... Sand and furnace are the two most CRITICAL things you have to have carved in stone as a core foundation of your processes.

Glad I could help. :D
mite5255
Posts: 1746
Joined: Thu Jun 02, 2011 1:11 am
Location: Caboolture Qld Australia

Re: Casting Aluminum Brackets for Kayak

Post by mite5255 »

I have just made a new gas burner and I'll give this a go on Friday, I'll aim for the colour, degas then pour
When life gets tough, remember: You were the strongest sperm :)
Silverforge
Posts: 40
Joined: Mon Sep 10, 2012 12:21 pm

Re: Casting Aluminum Brackets for Kayak

Post by Silverforge »

FC- Following this and the SAND thread- Sent a PM... For the "Blue" Toilet chips... I have a bit of stainless pipe I want to use to plunge the de-gasser (funny- that is what the blue chip does in my bathroom too... at least the smell anyway!)... am I right in that an IRON pipe will dissolve into the melt... and will the STAINLESS pipe be ok to use?
F.C.
Posts: 560
Joined: Sat Jun 04, 2011 10:28 am

Re: Casting Aluminum Brackets for Kayak

Post by F.C. »

Silverforge wrote:FC- Following this and the SAND thread- Sent a PM... For the "Blue" Toilet chips... I have a bit of stainless pipe I want to use to plunge the de-gasser (funny- that is what the blue chip does in my bathroom too... at least the smell anyway!)... am I right in that an IRON pipe will dissolve into the melt... and will the STAINLESS pipe be ok to use?
Copper will most certainly melt in aluminum, Iron won't, nor will stainless steel. I recommend the stainless, though, as it will resist aluminum sticking to it more than the iron will. However, I also recommend no matter which metal you use, spray it down with a coating of automotive primer paint (from any rattle can brand., KRYLON is what I use) or stove black primer paint (it's actually a very dark primer if you compare it's ingredients with that of the paints. The primer will flare off when you enter it into the melt but as for the light colored residue left behind the aluminum will run off it like cooked egg from a Teflon coated skillet. Likewise, if you're using a metal ladle or metal crucible. A pre-coat of primer will keep the aluminum from sticking to the inside wall.
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