I've poked around the search info on the forum and found nothing specific on the subject: I'm new at this but so far my experience with manuals on the subject just point out billet specs with strengths, shrinkages, weaknesses and general information on which alloys are used in various markets and industries. The info I'm looking for is: If I'm casting aluminum in my hobby shop to make small machinable parts, what suitable salvage material should I be looking to melt down? I have access to several "known" alloys from pure 1100, 3003 and 6061. The parts are not subject to stress of any kind but they are small and have to be machined and tapped with small mill bits and taps. Thanks. Please let me know if there is a more appropriate place to post...
You'll want to avoid those wrought alloys and instead choose scrap castings. Casting alloys have better fluidity and less shrinkage. Automotive parts like wheels and engine castings are the best but will require resizing to manageable size for your crucible. Small engine (lawn mower) parts and old power tools are also a potential source scrap casting alloy but most things that were previously cast would be suitable. Best, Kelly
the materials that i use in my ingots sales are primarily automotive cylinderheads, the only motor parts you will need to avoid are transfer cases, most air-cooled 2 cycle engines, and Volkswagen engines,these contain or are magnesium, mag fires are something you want to avoid, any piece that i get that feels to light i take a small piece and put it into some Kaowool scrape and hit it with a torch, if it is mag it will ignite before it melts, if it melts it is aluminum. Most carburetors are not a good grade of aluminum. Pistons are excellent as they have a high silicon content, I don't use them in my ingot sales because they generate an inconsistent product. extruded aluminium doesn't have the silicon alloyed in that is needed for good castings. Art B
Here's the last one I nabbed. Knocked the valve seats and guides out of it and cut it down on my Band Saw at work.....made short work of it. It was an LS3 Chevy head that met it's demise due to a crack in the H20 jacket. What alloy do you typically see in cylinder heads? 319? What sets transfer cases apart? Knew about VWs and some of the (very) old LawnBoy mower decks being mag but sort of surprised about most 2-strokes being mag. I've found motorcycle and marine engines to be aluminum. The really small string trimmer and leaf blower engines I've never fussed with because they're too much work for very little metal. I do have a cast automotive oil pan that is suspiciously light. I have a good source of cast pistons from a friend who is an engine builder. They do (re)cast well but not quite as good for nice machine finishes....but better than some gummy castings. Since I've been doing lost foam I've been able to quench my castings very shortly after they freeze. Then a little aging makes the 356 alloy parts actually pretty nice to machine and hold a thread. Most cast aluminum wheels are 356 but many are forged and forging alloys. You do need to cut them up but at least you get 10-15lbs of metal for your trouble. Best, Kelly
What I'm finding is that the cylinder heads are close to 356 with a higher silicon content. The very small air-cooled engines like trimmer motors and chainsaws are the ones that I have found to be mag. The other item I have found to be mag is the connecting rods on the larger BS engines 8 hp and up. I have had very good luck using auto castings as the source for items needing machining, they hold threads real well and when i have made castings that are structural, if you bring them to about 850- 900 hold them for an hour and then air cool to 600 and then water quench them. They seem to have less tendency to cracking. Anything that i get that seems lite, I cut off about a marble size piece and put the torch to it, I have found that some of the Audi covers are mag. My last mag fire was an Audi valve cover. About the same time I threw it in my big furnace it registered that it was lite, it ignited before i could get it back out, The furnace had a pool of about 50 lbs of aluminum so I submerged it in the pool, by keeping it submerged it contained most of the fire but that batch of aluminum was about 4% mag when i had it scanned. Art B
About half the transfer cases are mag. starting in the mid 90 they started using mag in order to meet the mileage requirements. Art B
Wouldn't have guessed that but sure is good to know. There's a lot of mag parts in BMW engines too but no BMWs in my scrap sources . Best, Kelly
David- I didn't post in your introduction thread so I'll take this opportunity to say welcome. Your question has prompted a great discussion which I'll be following. As a hobby caster my main focus is generally just getting my castings to fill properly so I generally use previously cast alloys as has been mentioned. Lawn mower engines, cast rims, tranny bell housings, etc. I have the luxury of being able to have bonfires in the backyard, so that's how I generally render my large scrap. I also use both horizontal and vertical bandsaws with bimetal blades to cut up scrap when I'm able. That's an often-discussed topic all of its own. But as to other alloys, I have quite a collection of scrap from many different sources including harddrive bodies, commercial window frames, fuser rollers from photocopiers (alloy unknown, but I have an unlimited supply), etc. If I need to be assured of good flow and fill I always use the cast material. If I'm casting blanks for machining, I'm more inclined to use one of the other alloys. I have a 9" southbend lathe and small clausing vertical mill, and although both machines function perfectly as designed, I am a self-taught novice operator. Point being, I can't tell if poor machining performance is because of the alloy or because I suck at machining, but I can tell you that I've had passable results with all of it based on my end use requirements. I'm not sophisticated enough to heat treat yet, although some here are and I'm paying attention, but there are a couple things I've found. Any aluminum will easily break a tap, and any aluminum will plug up a file. It's all in the hands of the operator! Aluminum is pretty easy to get and pretty easy to hoard so get some various types, pour some ingots and see what works best for your needs. I'd still like to read more about aging- artificial or otherwise, simple heat treatment, etc. Pete
I'll cross post this here, it is from the "other place" way back in 2010 http://www.alloyavenue.com/vb/showthread.php?4256-Foundry-Alloy-Metallurgy-Slide-Show&p=68308&viewfull=1#post68308 Foundry Alloy Metallurgy Slide Show Here is a slightly modified training presentation I did for people at my last foundry job to try to explain some of the science behind the foundry art. http://www.slideshare.net/FoundryJoe...-hobby-foundry I know there are some other metallurgists/experts here, if anyone sees an error or has changes/ideas to add let me know and I can update and give you credit. And if anyone knows about the 9000 series alloys don't say anything, they are watching! ----------------------------------------------------- Since I first posted this in 2010 I have been at two foundries, casting a German version of the 300 series and now hundreds of tons of 500 series The MIB still haven't come for me about the 9000 series alloy
And here is another...no longer listed on Ebay, but I have some left if anyone is interested Aluminum Foundry Metal Grain Refiner (TiBor) & Modifier I bought several barrels of Strontium and TiBor at a foundry close out auction (sadly it was the place I used to work). I am offering it in small lots to help out hobby casters. I have it for sale on eBay , since I want to create an account. I want to keep the price low so everyone who needs it can get some, unfortunately I can’t create a Buy It Now price until I have enough feedback. I intend to list it for $5.00 plus shipping once I can, so don’t bid too high, I will keep setting up new auctions until eBay lets me set a Buy it Now price. What is a Modifier, What Does it Do, Why do I Need it? Typical foundry Aluminum casting alloys (engine blocks, heads, transmission cases, pistons, wheels, other cast scrap) contain 5 to 12% Silicon. Unmodified castings made from these alloys contain coarse, plate-like crystals of Silicon which forms during solidification (eutectic Silicon). These Silicon particles are in the form of brittle needles which reduce the strength and ductility of the casting. They also tend to create porosity by inhibiting the flow of molten metal (feeding) in to areas of the casting as it solidifies. With Strontium modification, a different and improved cast structure is developed in which the Silicon phase is “modified” by the action of Strontium to become fibrous and finely dispersed. The result is improved mechanical properties. In particular, both ductility and machinability are improved. Strontium also tends to reduce the size and shape of harmful iron compounds, resulting in improved ductility. It can reduce the embrittling effect of Iron contamination if you melt/pour with a steel ladle. Modification has been called “the poor mans heat treatment”, since it improves as cast strength without the need for heat treatment. Please note that if you are melting low Silicon alloys (Aluminum cans, siding, ladders or extrusions) this Strontium modifier will not make any improvement since there is little Silicon to modify. These materials are not designed to be cast, and you may want to consider changing to an alloy designed to be cast to improve your casting success. What is a Grain Refiner, What Does it Do, and Why do I Need It? When metals solidify they develop a grain structure. Slowly cooled metals (for example from sand casting) have a relatively large grain size. Faster cooled metals (for example from die casting) have a smaller grain size. Benefits from a smaller grain size include; better feeding for reduced shrink porosity and stronger castings. A grain refiner promotes a smaller grain size even in a slow cooled casting. Here is a good practical publication that explains this in a bit more detail. http://www.metallurgaluminium.com/Do..._Treatment.pdf How to Use As per manufacturers recommendations add 3 rods per 100 pounds (or 1 rod per 33.3 pounds). With a few rare exceptions, it would be hard to overdo it, so just add 1 rod of each if you are melting less that 30 pounds per melt. With a small melt, add both the TiBor and Strontium rods as soon as all the metal has melted, and gently stir, skim and pour.
I bought some of the modifiers years ago when you first got them. I haven't done more than a couple pounds of Aluminum since then, so I haven't used any of it. I even cut some down for a 10 pound pot of metal. I cut the rods in thirds.
