Why I hate casting aluminium.

[@akdenyer]

Hi, I had a good friend that used to cast engine pistons commercially. The alloy is critical to get the correct structure then they had to be heat treated to give good machinability and hardness. They came out like jewels they were so perfect. He always used CBN and diamond tools. Now those castings you have been looking at are pressure castings. The metal is pumped into the mold under pressure. I worked at Cosworth where they developed this process filling molds from the bottom. Aluminum also has to be degassed before pouring but I am sure you know that. I have done a little aluminum casting just making blocks for machining and they worked out ok.

[@xXMACEMANXx]

I read a paper some time about some Silicon containing Aluminum alloys can have an issue with the Silicon Carbide crystals floating to the top of the cast. Industrially, they use big mixers to agitate the Aluminum while it's molten. I'm not 100% sure about that answer, but when I saw that the alloy had separated like that it reminded me about that paper and it made me Google what alloys are used for cylinder heads, and all of them are Silicon containing, so that's my best guess.

[@UncleKennysPlace]

I believe that silicon carbide is more dense than aluminium, thus would sink to the bottom of the mold.

[@xXMACEMANXx]

@UncleKennysPlace I may have gotten that backwards, but I do know it had separation issues

[@policedog4030]

The BMW Rim is likely forged aluminum alloy so it would have been alloyed to withstand that processing. Here is a cut and paste from Fuchs: (as you know most cheaper wheels are cast aluminum): "In the first forging stage, the blank is forged into a rotationally symmetric piece under a force of 4,000 tons. In the second forming stage, the styling is pressed into the pre-forged blank in a 7,000 ton press, which largely gives the wheel its later appearance."

[@ryebis]

Aluminium car rims are usually a decent source for casting projects.

[@paulkurilecz4209]

Car rims are usually made with A356 which is a hypoeutectic Al-Si-Mg alloy containing 6.5 to 7.5% Si. It has excellent fluidity and minimal porosity created when solidifying.

[@oscarbaez4756]

Ese defecto es por aluminio contaminado ,puede ser antimonio ,zinc u otro metal de aleacion .Quizas con una temperatura mas alta podria mejorar ,pero no es seguro que pase . Para desgasificar el aluminio uso cloro en polvo (el que se usa en las piscinas ) una cucharadita de te por kg de aluminio ,luego una cucharadita de sal comun de mesa ,quitar la escoria y verter en el molde .

[@innleadair]

I've been casting aluminium on and off for decades, never has this problem. I have learnt to cast my scrap into batches of ingots first and test each batch by breaking an ingot from each batch to see how the strength and grain structure is. Had a problem a few years ago with huge crystals forming and a very weak (useless) castings, think it was some diecast zink that got in the mix? I use oil bonded sand, dead easy and no need to vent except for things like long cores. Agree about the car wheels being a pain to cut up. Easier to break them up with a sledge hammer, than to cut them. Water cooled VW cylinder heads are made of really nice alloy....

[@williamlefave4058]

If you can tell me how to get the air pockets out and how you are testing the alloy, I would be eternally great full. My goal is to just be able to cast a cylinder so it can be machined for students. It would help a ton with getting the costs lowered for the class and make it so we don't have to charge as much.

[@notyouraveragegoldenpotato]

I've been using a bunch of Audi heads I've saved up (destroyed) over the years of my car hobby. They cast very well, very cleanly. Wonder if Volkswagen auto group just used a better alloy for its Al parts. I've worked on porsche, audi, VW and they all share a surprising number of parts

[@fullmetalmachinist3883]

Casting twice once into ingots and later final part mostly removes the problem, as it is caused by impurities carrying gas. One other thing that can be done is degassing using small quantity of baking soda (sodium carbonate, NaHCO3)

[@techno_mesh]

Hi, I will try to remember some of the things one of my best friends told me some 20 years ago when he worked at a company that was doing aluminum and bronze castings. It was mainly in metal molds if I am not mistaken. I have never in my life worked doing any kind of foundry work so take what I write with a grain of salt. First I recall aluminum-silicon alloy would generate bigger grain structures and worse flow than aluminum-copper alloy. They would always try to use the one with copper alloy. The other issue was that molten aluminum will absorb a lot of hydrogen very fast and at cooling it would exit the molten matrix and leave small bubbles inside (not sure if on the surface) and they would show very bad later when machined. To solve that they would use some sort of tablet or cookie shape tablet that would be tossed into the crucible just before pouring. That thing would sink to the bottom and generate a lot of bubbles (I might recall it was some chlorine gas) and that gas would drag or combine with the hydrogen, lowering its concentration to a big extent. He told me too that for car rims they would apply some sort of low pressure to obtain a better casting surface. A vacuum like the one generated by a vacuum cleaner with a relief adjustable hole. I imagine there might be some way on the internet info to discover if your source material is more silicon or copper inclined.

[@custos3249]

Surprised you haven't rigged up a hydraulic press out of something like an old log splitter to break up the car rims. Heavy blanket over it should eschew any risk of bits shooting off. Also, I agree. Part of me was thinking some metal in the alloy may be holding onto oxygen much more aggressively, but looks more like a constituent metal is precipitating out as it cools. I suspect there is still a way to use it, but the ideas that come to mind would be quite the engineering undertaking. Alternatively, might be able to use that to your advantage if you can find a way to control where it precipitates out, remove that section, and reuse the clean material.

[@jimintaos]

I have never used scrap aluminum-I'll have to try it sometime. I order ingots of known attributes. It costs more than free but a thing is not free when you have to redo the labor when you are already under the gun to get the damn thing out the door.

[@markfryer9880]

Hi Luckygen1001, great to see a video from you again! The shed seems a lot clearer now? Have you been working your way through your stocks of materials? Mark from Melbourne

[@Marc83Aus]

What are you using for flux? In regards to the inconsistency of your pours if you cant identify the alloy used i would advise trying to use an entire part for each cast since you know that whole part was one alloy, you might want to do test pours with a chunk of the scrap first, a mini ingot and see how that comes out before doing a large pour. if you are doing a large cast that requires several donor parts of indeterminate alloy you might also want to do a test pour using parts of those donors to see if the mix of alloys at the required ratio work. there also could be alloying agents you could add to make it more consistent, IIRC higher silicon content is desired for better castibility, copper being the opposite making it flow worse and more likely t o crack. However I believe your major issue is either trace iron from the car parts or gas bubbles, So i would say look into aluminum casting fluxes.

[@luckygen1001]

I don't use flux with aluminium car rims and always get a excellent result. If I get a large amount of one type of scrap it pays to melt a small amount to see if it is suitable for casting.

[@matthorn6118]

Gas in the Aluminium smelt must be removed. 1) Using degassing tablets. Difficult to find. And when you do, a huge amount must be bought. 2) Use another gas, nitrogen to bubble through your smelt. Think "aquarium bubble" system, but now with nitrogen and heat resistant. Expensive and overkill. 3) The Chinese method! Melt the Aluminium, let it solidify in the crucible. Then re-melt. WITHOUT STIRRING then poor: no more bubbles. This cannot be done in a commercial smelter, as re-melting is too expensive (time consuming), that is why a reference to this method is difficult to find. I found it on some Chinese website. The alloy might make a difference, but don't focus on that.

[@canadianoddy8504]

Well ------------- I think I'm going to have to try that idea. Thanks for posting that. Chinese "quality" is always suspect but they are smart over there and may have stumbled onto something. At the end of the day I think it's quality of the aluminum. Any car parts aluminum is going to be impregnated with oil and it would be very difficult to get it clean. Then there is temp control of the melt , degassing and venting. I have done a little bit of aluminum casting and mine are very poor quality. It's an art form for sure.

[@stickyfox]

@@canadianoddy8504 China is just a little more pragmatic. They know there's demand at every price point, regardless of quality; and will rise to any challenge. Our best *and* worst consumer products come from there.

[@nobodynoone2500]

@@stickyfox It's true they can make quality things, but I would stop well short of "the best".

[@stickyfox]

@@nobodynoone2500 they make all our computers and smart phones and most of our car parts now. I mean, I agree... we shouldn't think of that as the summit of achievement.. but we don't make those products here because we don't want to pay the taxes on them. Even tho we'll pay a tariff to get it from overseas.

[@Fragaut]

Wow. It looks like very uneven retraction during cooling and solidification. My guess is the melt viscosity gets extremely high near solidus. Segregation and forming of dispersed precipitates before bulk solidification would be the perfect mechanism for that to happen. And the metal cannot flow to fill the shrinkage around cooling zones. It would be consistent with the defects being way worse on the cope side. I see @akdenyer talking about pressure casting. He may well be correct. High pressure injection would actually solve this problem by forcing the metal to flow towards the shrinking areas, regardless of the viscosity. This alloy seems useless for fine casting. You may still be able to produce ingots for machining or forging.

[@luckygen1001]

The cope side is usually the last part to solidify and the top of the sprue as well so that is why that defect happens the most.

[@Fragaut]

@@luckygen1001 Yes. If the metal is too viscous and cannot flow from the riser to compensate for the solidification shrinkage, it will draw from whichever part of the casting is nearby and still somewhat fluid. And the weird voids is what one would expect if the viscosity is uneven, and the metal is not pulled equally.

[@MarkATrombley]

I think it was aliens.

[@ChirpysTinkerings]

It looks like sand wash to me, or steam pockets due to water droplets in the sand, but I know you run your sand through the sand muller, so it should be thoroughly mulled well, so Im not sure what it could be really. Those hub caps might be some wierd mix of A380 or A413 since it is a bit more tarnish resistant, but Ive cast with those alloys quite a number of times and havnt had much trouble with them. It is defenitely weird that it is only happening with that one source of scrap.

[@luckygen1001]

This is why I made a video about that defect, very strange. It does not like to be poured into a sand mold. Looking at the ingot fracture it seems more suited for die casting.

[@ChirpysTinkerings]

@@luckygen1001 After thinking about it, it looks like an aluminum alloy with high copper content, which really dont like moisture in sand at all, but it looks like almost an extruded alloy by the way the crystal grains were on the top of the ingot tbh. Either way, looks like metal to be turned in for "beer money" really, lol.

[@pjofurey6239]

Very Interesting and some good testing done. I recycle a lot of Japanese motorcycle parts in my foundary , I hear you about cutting up wheels , years ago I decided to try breaking my melting stack up using my 30 tonne hydraulic press, it has become somewhat of a sport here , after a few months I now drop a heavy beach towel over the scrap being crushed apart and wear a heavy smiths leather apron, the ballistic capabilities of the press are impressive! I listen put for the “creak” usually between 12-20 tonnes of pressure then it just goes “SPAAAAAANGGGG! “ Just got back into the shop and planning a new burner etc , will look at your channel as great reference and up date my vintage set up . Thanks mate .PJ

[@luckygen1001]

Years ago I had access to a 150 ton press and I have to agree it is the only way to break up scrap. So now I am retired and have to use other methods.

[@rogertaylor1589]

I agree with matthorne8116. 'We used nothing but random aluminum scrap when i taught high school foundry. Nitrogen degassing tablet's allowed us to make pressure tight castings from scrap.

[@MuzzahA1]

I knew a bloke who cast stuff years ago. He said he only uses aluminium that is machined, if you can machine in a commercial setting it has some quality about it. His go to material is car rims, the same as yourself. As for cutting the rims up, plasma, I can make perfectly good metal in to scrap with one of them.

[@siggyincr7447]

I'm guessing here, but as far as I know modern aluminum casting like the ones giving you trouble are a strange alloy that has an almost 2 stage crystallization process with some of the metal starting to form crystals while the rest is still molten. They inject the molten alloy at high speed and pressure into metal molds where it cools down very fast leaving a very strong micro crystalline structure. But if you try to cast it traditionally it can get all funky with the initial crystals getting quite large while the rest is still molten.

[@Preso58]

Martin Olfoundryman West shamed me into buying new 601 series ingots, and overnight, my castings improved. I think i paid $5 per kg (in cash). How do you break up the wheels?

[@highlandermachineworks5795]

Happy to see you here. It tells me I'm watching a quality channel, when I see other you tubers that have good channels. Eventually I'll work on mine.

[@jirvin4505]

Preso where do you get your ingots from. Locally qld?

[@markfryer9880]

Hey Preso! Good to see you again! Mark from Melbourne

[@VladekR]

Waiting for Martin's reply 😉

[@luckygen1001]

@@VladekR So am I.

[@electro1622]

Aluminium casting is very sensitive to temperature and overheating the melt often causes porosity however, your porosity seems to have sharp edges so it is probably inclusion porosity rather than shrinkage or gaseous porosity.... onother thing which points to that is that it's on the surface and not within the casting.... I would smooth out the flow (no 90 deg. bends in the sprue ) and remember the golden rule which is ALWAYS make sure the sprue is thicker than the casting and always sprue to the thickest part of the casting. Upon further research there seems to be an issue with Aluminium and hydrogen absorbtion... this sort of porosity looks an awful lot like yours does so a quick trial may produce what you want. Several methods are currently in use to degas aluminum. These methods include the use of nitrogen or argon, or a mixture of either of these with chlorine, as a purge gas

[@stickyfox]

Hydrogen is a lot more of an issue than people first assume. I spent a year trying to solve a plating problem that eventually was solved by baking parts for an hour in a slightly warm oven.

[@stewartwoerle6351]

Perhaps before you toss that stuff, try lost foam and see if you get the same thing happening. Foam with plaster painted on and straight sand to support. If it works, happy days, if not you can still send that 200kgs to the scrap merchants. On another tangent, the crucibles you use for cast iron, would they handle casting steel? If so, what type are they and where do you get them? Have been watching your channel for years, and have learnt so much. Thanks mate for sharing your knowledge

[@luckygen1001]

There is one problem using clay graphite crucibles for steel is it will absorb the graphite and change the carbon content in your steel.

[@stewartwoerle6351]

@@luckygen1001 So, adding carbon to the melt would fix that….or use something other than graphite crucible?

[@luckygen1001]

@@stewartwoerle6351 I f you don't mind the carbon content in steel changing use a graphite crucible.

[@stewartwoerle6351]

@@luckygen1001 I’ll give it a go on some smaller stuff. I eventually want to make a pourable crucible/furnace to try making a swage block somewhere around the 50kg mark. Will mean making the crucible to suit, so want to find the best materials that will withstand the temperatures required

[@luckygen1001]

@@stewartwoerle6351 That is the best way, do a small scale experiment instead of spending lots of money and find out that it does not work.

[@MarksGoneWicked]

I haven't read the books @olfoundryman mentioned in a video. He suggested 3 books to read to get good castings of aluminum.

[@jamesmihalcik1310]

It appears that a low percentage of magnesium was used in that aluminum alloy. The magnesium is forming grain structure at a different temperature than the aluminum as the alloy is cooling. Better for injection molding than sand cast. I seem to recall an acid test you could do on the casting to see if it contained magnesium, I will have to look up the test to find the correct acid and percentage. Interesting video, thankyou.

[@luckygen1001]

I do have some HCL I could put on that hub cap.

[@rudycandu1633]

One more Internet Expert. (reading some of the previous ones were painful) Different aluminum alloys have different characteristic. General wisdom is that if it was previously sand cast then it should be a good alloy to sand cast. That automotive parts should be a good source of aluminum for sand casting. I wish it were so simple. There are many factors when choosing an alloy and with it process considerations. And you don't know all those details when dealing with scrap. Some castings are die castings and that process is totally different than gravity casting. Iron is a required element in the alloy when working with steel dies, but is undesirable from a metallurgical aspect. Hydrogen in the melt is bad, but sometimes desirable. More hydrogen will cause more porosity in the structure but can also reduce the external shrinkage. When the alloy solidifies it will shrink, but where? Internal porosity might be acceptable depending on the part designed. Some alloys have a fast freezing behaviour and some are slow freeze. Another factor to consider. Without knowing the alloy's composition, and testing how to work with that alloy, the best solution is to use only what you know that works with your process.

[@luckygen1001]

The iron is added to stop the alloy welding itself to the steel die. I think this alloy has a wide freezing range so some parts solidify first blocking metal to the last place to solidify. Die casting would prevent a lot of those defects.

[@Angus_McGyver]

Well, im a rank amateur, but i have never seen the type of anomaly seen on the top of the sprue and ingots. I have used all kinds of scrap, from wheel rims to extrusions. It makes me think of boiling.

[@felixbors7546]

I would talk to a metallurgist at the nearest university. Also are the pockets superficial (if you face it on a mill, are they distributed evenly with depth?). Really enjoy the channel. Thank you.

[@DrTheRich]

Seeing the segregation of the different metals in the alloy, I wouldn't use it even if you could just surface it. Way to non-uniform. You'll never know where it will be weak and break.

[@luckygen1001]

@@DrTheRich It did take a lot of blows to fracture that casting but you are right it could break at the weakest point.

[@gafrers]

Always interesting to learn more. I had some clues but not a firm answer.

[@kokodin5895]

i belive welders also hate cast aluminium from similar reasons, bunch of traped impurities that leach out when melting metal but i don't know what causes it but i would really like to ask about something else how do zink aloys behave in similar situations, and are they any suitable replacement?

[@luckygen1001]

I have never used zinc alloys so I don't know how they behave.

[@lodgecav490]

Do angle grinder discs leave traces of impurities in the alloy when cutting? Just a thought, maybe plasma cutter or sledge hammer would be better. .🤔

[@felderup]

long time ago i had an e-book about aluminum and all the varied processes, one thing it talked about was the specific alloys that were best for casting, extrusion and machining, you _might_ be able to use a camera to figure out what alloy you have when it's hot, then amend with a high alloy ingot.

[@mikegregory460]

i have found the same and it isn't the mold as i cast the ally into steel or graphite molds to use as cast stock to be machined later. my results are similar

[@luckygen1001]

How does the cast stock machine? When I poured the ingot the steel mold drove the defect to the top.

[@mikegregory460]

​@@luckygen1001 i get huge porosity mainly deep in the center of the piece. I still have some that i cut in half so could send a photo if i knew how. If i remelt it again and recast it then it does get somewhat better so i assumed it was the oils giving dirt and gas that doesn't skim off. Was going to try fluxes next time i melt some. Pure ally comes out with very little porosity.

[@luckygen1001]

@@mikegregory460 Dirty oily scrap will cause a lot of defects.

[@DDB168]

I've saved a heap of small engine (lawn mower) alloy bodies. I guess they'll be useless? I do have two car rims though, but as you say, very difficult to chop up. I read a lot of the comments and it appears silicon is the culprit. Are there any additives that can be used to to lessen it's impact? oldfoundryman suggests strontium or sodium, a lot of derivatives containing those, so which to choose is beyond me. Interesting video.

[@luckygen1001]

The best way to find out if your lawn mower scrap produces this defect is to melt a 0.5 kg sample and pour it into a ingot mold. if the top of the ingot has those odd shaped depressions don't use for sand casting. Those additives suggested by olfoundryman can be hard to get so in the end car rims are your best bet.

[@BlainesGarage]

A few years ago I made a wheel melting furnace from a 55 drum and made a shallow funnel from a top of another drum. Since this video was made, we burnt a hole in the bottom of the stainless steel pot, so i now use a cast iron Dutch oven to catch the aluminum. All the nasty remains on the funnel. Very little dross skimming. I pour it all in to ingots. Nice clean aluminum to use in my electric furnace that i use for casting. kzbin.info/www/bejne/omjXooKur9J6oJIsi=0fmm3S_a2xcX81Fd I’ve never experienced the issue you’re having, but i only use petrobond, and lost foam in dry play sand. No experience with greensand.

[@a-k-jun-1]

Very informative as always, thanks for taking the time to show us

[@heilerdelarosa]

Greetings, my friend, you would have to make a large oven, insert the entire tire without cutting and when melted, pour it into ingots so you use portions in the small oven.

[@ASoftaaja]

Alloy segregation sounds plausible. I was thinking you could try the molding techniques which should reduce air entrainment to see if that has any effect. Smaller size sprue, pouring basin, tilting a plate casting like the one in the video so that it fills from one side gradually raising and not having streams running across the plate.

[@luckygen1001]

I use the same methods pouring castings from aluminium car rims and this defect dos not happen. I think this alloy is more suited for die casting.

[@michaelclark2840]

If you put the alloy rims on a fire bed, heat them up to a reasonable temperature it is easy to break them apart into small pieces with a hammer.

[@fluffyfullbox2075]

You need to preheat the mold to stop freezes.

[@paulkurilecz4209]

It is difficult to say specifically what is causing your casting defects. However, I can speak in generalities. First, it is important to know which alloy that you are using. The most common casting alloy is A356 and is the main alloy for aluminum wheels. It is a high Silicon (6.5% to 7.5%) content alloy. It is slightly hypoeutectic so porosity during solidification is minimized. If you are pouring a lower Si content or Zn content alloy the castings will not be as good. Cylinder heads may have Zn added for strength and higher temperature strength. Castings such as the alternator and starter motor castings may be low Si and are likely pressure die cast. I haven't seen how thick your casting is at the beginning of the video, and this may be part of the problem. Some of the defects that you showed on the casting look similar to freeze outs and cold shuts. If your casting is relatively thin you may need to preheat your mold or increase the superheat on your melt; or, both. Thin castings are difficult to do in sand castings because the metal will cool before the mold is filled. If this is the case, then just a slight adjustment is needed. Depending on the scrap that you start with, you can adjust your melt. For example, if you are using aluminum cans as your raw material, this is a poor choice for a casting alloy but you can handle that. Aluminum cans are usually made from 3104 which has almost no Si but is alloyed with Mn and Mg. To use aluminum cans, make your melt, refine and cast into ingots. After the ingots have cooled, weigh them. Then when you go to remelt, add about 7% by weight Si. You will then have a good casting alloy. The small amounts of Mn and Mg won't have much effect. hth. PS: @5:15 the results look like shrinkage during solidification. Again, it depends on what your starting alloy is. It is definitely a lack of fluidity and possibly cold shuts. PPS: On the 200 kilos of scrap that you have, don't throw it out straight away. Make some ingots and have them tested for composition. Once you know the composition, you can possibly adjust your chemistry. Another good scrap source for you would be extrusions which are a 6000 series and would only require some additional Si to make it a good casting alloy.

[@svenp6504]

I would be curious if adding a substantial riser (4-5 in) would help by adding hydraulic pressure to fill the mold better and counteract steam or gas being released from the melt as it cools. It would be an easy thing to try...

[@luckygen1001]

I did use very dry sand and vented it so it still made those defects.

[@svenp6504]

@@luckygen1001 Right, with a 'good' alloy it should have worked much better. But with this one, there could be extra gas release at solidification or it may just be lumpy due to different fractions solidifying at different temperatures. But maybe the extra pressure would still help.

[@tobhomott]

Wow... Never had Al behave that way for me. But I mostly stick with "wheelium" too

[@luckygen1001]

Yep I will stick with wheelium also.

[@shortaybrown]

Question: Can you cut the car rims up with an oxy/ acetylene torch? That would make quick work of them right? Nice vid!

[@luckygen1001]

I don't have a oxy/ acetylene torch also it will only cut steel.

[@Masirah1]

I am not expert, but I think you need to fast cooling quench the cast as soon as it get the shape, then you will heat treat to relieve the stress.

[@dmitriykolesnik4462]

Strangely abnormal shrinkage. Motor aluminum is usually alloys with a high silicon content, they do not behave this way. There may be a high content of oxides; you can try letting the melt sit for half an hour or more in a closed crucible so that the oxides settle to the bottom.

[@luckygen1001]

Interesting idea.

[@Rick.123]

You need to put a degassing compound based on calcium carbonate

[@creast56]

I haven't seen this anomaly on aluminium so far as I tend to use wheel rims. But, I have seen this on zinc alloys or pot metal and you do get severe shrinkage and that strange pattern. Maybe your alloy has a high zinc content?

[@luckygen1001]

It could be.

[@rufustoad1]

Can someone suggest a general of how high above melting point is best to pour any medals?

[@glandanit]

Could you show us the result of Car parts alluminium vs Mag rims alluminium using the same mold so it is a fair comparison for quality.

[@anneinfurna8528]

The biggest part of using Scrap to cast from is This -- There are a Lot of garbage alloys used that work for processes such as injection molding, Pressure casting, etc That just Do not hold up when sand casting. A lot of monel metals (Pot Metal) Look like al, but do not mix well and cast well. Another consideration is Green sand versus a Petrol Bonded oil sand, I have had perfect results in the second one than the first. Critical to the process is cleaning the scrap before you use it -- I use sand blasting to clean crud off. Clean up your grading of the white metals, and when in doubt -- Use only metal off of 1 known piece -- no Mixing. This should go a Long way to cleaning up your operation. Lessen the variables, and enjoy good homogenous castings that are a Pleasure to dig out of the sand. Carry on!

[@xlerb2286]

Oh yes indeed, 100% agree. You can buy yourself a lot of trouble trying to save a bit of money and use whatever Al scrap you have on hand. Beverage cans are the worst. They aren't an alloy meant for casting. And between paint and coatings there's a lot of impurities that as they burn off will leave impurities in the metal. Fwiw back when I was doing casting I just didn't do anything with aluminum. It pollutes everything.

[@davidhannah4302]

I am affraid your choice of aluminium scrap is a poor choice alloy wheels are much better as theres more magnesium in them those parts are diecast and contain zinc also i would recomend a higher temp and a slow stir or degassing i cast aluminium thin sections every week with a 200 kilo bale out furnace into greensand or bonded sand with great results the bonded gives much better results but is more expepensive i have followed your chanel and have 2 of your furnaces for our cast iron buisness and they work very well

[@lancer2204]

Silicon content? It reminds me of slag inclusions after shot blasting.

[@DerrangedGadgeteer]

What temperature are you pouring at? Those look kinda like cold shuts, and I wonder if the alloys you've formed by mixing scrap just need to be poured with some more overheat.

[@nobodynoone2500]

Looks mildly contaminated. Just cast ingots first if you have the ability. Should clean up a bit.

[@erwe1054]

Привет дорогой друг! Не используйте для литья алюминиевый силуминовый лом, сначала необходимо первичная переплавка очистка

[@Scumvermin]

Hi you probably don't want a Kiwi telling you what to do but I have been a supplier of Al and Cu base ingot to NZ and Aussie for a fair few decades now I will refer to alloys by the Australian standards but these alloys have equivalents world wide Wheels are CC601 that is 7% Si for moderate fluidity and 0.3% Mg for heat treatment and 0.05% Sr for grain refinement the smaller castings like alternator bodied are pressure die casting alloys like DA401 with 12% silicon and 1% iron very fluid but very subject to surface shrinkage such as you see also your remnant ingot and sprue top indicates this alloy Bell housings are often CA313 another pressure die casting alloy 9%Silicon 1% Iron and 3% Copper often very shitty ( technical jargon ) and the Cu% causes corrosion Forged wheels have no Silicon and run very poorly wheel may have the word geschmiedet on it you have no riser to help feed the casting however a large runner bar and in-gates can be better for the type of casting shown and allow the casting to feed instead of sucking in the surface Good to see your sprue taper toward the casting The finer grain toward the surfaces is purely due to the faster cooling rate against the sand I know wheels are a bugger to break up but they are the best option for sand casting short of paying twice as much for certified ingot and the CC601 alloy develops micro porosity in the center rather than huge sucks on the surface Good luck with your castings

[@luckygen1001]

Thank you so much for your description of alloys. I would add that every foundry does use different alloy for the same casting as most seem to come from overseas these days.

[@JoseSilveira-newhandleforYT]

Good video! I read in several places that the alloys used in the car industry (all of them patented) are very bad for recasting, probably because remelting them, changes the composition somehow, making it unfit for purpose. Most of these patented aluminium alloys crumble like cast iron, when hit with a mallet, instead of deforming like normal aluminium does, which is probably a good way to predict which are good for recasting.

[@luckygen1001]

So true and that is why I will be throwing out the lot.

[@JoseSilveira-newhandleforYT]

@@luckygen1001 Yep. It's so unfortunate. Such a large quantity.

[@DrTheRich]

My thought was segregation or like de-emulsifying of the different metals. Seems to be your conclusion too in the end.

[@katough]

circular saw to cut alum wheels

[@markfryer9880]

Or a Plasma Cutter

[@Drottninggatan2017]

Maybe a hydraulic wood splitter.

[@VladekR]

small tile cuitting saw with small 'steel demon'

[@VladekR]

@@markfryer9880 no

[@VladekR]

@@Drottninggatan2017 no

[@grahambird1570]

Interesting >> More 'Big Bore' Vents Preheat the Mold. Add small amount of Cadmium Pressure the Aluminum at the end of the pour before total solidification. Don't use old Aluminum castings. There's a list of tips for you.

[@Kevin-ht1ox]

Don't try to degas the aluminum.

[@VladekR]

Why?

[@Kevin-ht1ox]

@@VladekR the sodium bicarbonate creates CO2 gas which is what makes the bubbles. It also leaves some in the metal. People think they're degassing it but they're not, they're actually just making their aluminum bubble and providing it the opportunity to capture more gas.

[@luckygen1001]

@@Kevin-ht1ox I made a video about this subject, it is the moisture that causes the bubbles using sodium carbonate.

[@VladekR]

@@luckygen1001 moisture (as you prooved) seems to be a culprit, also sodium bicarbonate is the wrong substance to use, there are cheap degassing tablets on the market too, but reducing bubbles seems to be more of the pouring technique then composition of the metal (need to be clean too). The great John Campbell (who I met in Melbourne at the AFI 57th National Conference) describes ins and outs of casting in his books too. Best Regards.

[@ducatist4s45]

Salt in a aly foil wrapper poked to bottom of melt. Reduces hydrogen gas. Use at end of melt and wait for gassing to stop.

[@rudycandu1633]

And since that is such an easy solution, industry decides to go a different route. (sarcasm)

[@luckygen1001]

@@rudycandu1633 Cant argue with facts!

[@JFirn86Q]

Die cast aluminum alloys are going to have a lot more silicon than alloys designed for sand casting, as well as copper. This could give you issues for sure. However I think this is from hydrogen. You need to remove the dissolved hydrogen, which can be increased with these alloys that have more magnesium in them too.

[@jdmccorful]

Vote for trapped gas from foreign material. Always enjoy!

[@DrTheRich]

my minde went to oil soaked into the metals, but makes no sense of course, that would burn out during the melting. Other gasses would also escape during melting.