Making Silicon Bronze At Home

Discussion in 'General foundry chat' started by Swiftsure 33, Apr 23, 2023.

  1. Swiftsure 33

    Swiftsure 33 Copper

    Here goes with the question that inspired me to join the forum. Is it feasible to make your own silicon bronze (C87300/Everdur) at home with a propane furnace? I've found a few threads here and elsewhere vaguely discussing the topic but information overall is scant online. Perhaps this is for good reason, but the challenge is part of what makes this all appealing.

    My primary reasoning, though, is cost. The cheapest everdur I've found online so far comes to ~$11/lb with shipping. I am slowly growing my stack of road-side scrap copper, and I can get it locally for just under $5/lb. Having priced out silicon and manganese I could make my own everdur for just over $6 plus fuel if I am producing decently large quantities. If anyone can advise on suppliers of bronze ingot in the central FL area I may scrap this idea altogether for my main melting stock, but it may still be a worthwhile experiment.

    So far the only alloys I've played around with are aluminum bronzes. I've done a bit with a straight 90/10 alloy and the golden color is very nice. I've also managed a successful homebrew of C95300 (87.5/11/1.5 Cu/Al/Fe) for use in casting bronze knives, this stuff is ridiculously strong. These are both great metals but I've found that the shrinkage is quite hard to deal with in greensand molds. The scrap Si bronze I've used is leagues ahead in terms of castability in a home foundry with limited post-processing resources. I mainly want to use it for decorative pieces, but if I could achieve a repeatable high-quality result I would be looking at making some marine hardware down the line as well.

    From what I have gathered so far, it seems like the process would go something like this: Melt a heel of pre-made everdur purchased from retailer, add desired amount of copper and heat to puddle, plunge required amount of Si and Mn into melt and allow dissolution, stir. As I understand the melting temps of Si and Mn do not actually need to be reached in the furnace, and that the inclusion of the bronze heel encourages them to "dissolve" into the larger melt. My immediate questions are temp required in the melt for this dissolution to occur? Length of time of reaction needed before pouring? I'm sure there's plenty of other nuance to this but it seems like there are at least a few users here that have had some success at this so any information is appreciated. I would also love to hear about other alloys that can be made at home.
     
  2. FishbonzWV

    FishbonzWV Silver Banner Member

  3. Petee716

    Petee716 Gold Banner Member

    My best advice is to send a private message to Lou from the thread Bonz linked above. I don’t know about his price these days but but he is a great and reliable source. I’ve bought from him a couple of times and had absolutely no complaints.
    Rasper makes his own everdur for his sculpture routinely and is happy with the process. Others, including myself have done it and have found the process cumbersome and not worth the effort compared to buying it. I suspect if Rasper could buy it in ingots in Mexico he would do so. The method Rasper has taught us is exactly as you described above with the exception of stirring. Plunging is the recommended method which is where I had trouble. I had my Si and Mn measured and wrapped in aluminum foil and plunged it into the molten copper-and-heel mixture as you described and held it down there as best I could, but the contents rapidly floated in the form of what looked like a vermiculite-ish dross. I’m sure most of it went into solution and I pushed the dross layer down into the melt just a bit to try to get more of it to dissolve, but not all of it did so. I scooped off the dross after 5 minutes or so (with the furnace running) but it still had some of that stuff in it, so the integrity of the resulting alloy was iffy. I poured it into ingot molds and later integrated it into the melt with known everdur on later casting projects. I did about a half-dozen alloying heats one after another on the same day and ended up with the same process every time. All told I did about 40lbs that day. I remember it was a hot sunny day in Buffalo that day and I pretty much got my ass handed to me by the end of the day. That’s when I decided that it wasn’t worth the effort as I could buy it cheap from Lou.

    As far as performance goes, anyone who has melted everdur knows that dross is minimal and almost non-existent. Copper on its own oxidizes readily and produces a good amount of dross, but when melted into a generous heel of everdur I found it to be minimal before adding the other elements. I just skimmed off what was on it before plunging. When using the ingots for later projects I combined them with known alloy as I mentioned and had no noticeable performance problems with the castings either in the crucible or with the resulting castings. Of course my castings are for decorative purposes (with no chemical patina) as opposed to functional so I don’t know how the castings would hold up as far as end-use metallurgical requirements go.

    So my recommendation is to buy it if it can be had reasonably, but I’m a big advocate of testing and experimenting. So have at it. I still hoard #1 copper and am keeping my supplies of Si and Mn just in case I decide to take another stab at it!

    Pete
     
  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Just as a general comment, when alloying metals, constituents with higher melt points than the primary metal (but actually any metal) will go into solution much more rapidly if you reduce the size of the added alloying metal pieces. This is because the smaller particle size increases the surface area/volume ratio so they rapidly come to melt temp and the increased surface area increases the rate of dissolution thus the use of shot for adding phosphur bronze for example.

    However, if the metal is less dense than the primary metal, it will float, and depending upon the metal, rapidly oxidize, and the increased surface area will work against you and greatly aggrevate the degree to which oxidation occurs. Once this occurs, the melt point of metal oxides can be quite high and resistant to dissolution, thus becomes dross and never dissolves into the metal.

    You can make metal tools to keep the elements submerged, but they will often dissolve too, so better to make them from refractory materials rated for metal contact and preheat them.

    I don't do much with bronzes but there are similar challenges with aluminum alloys. One of the most common aluminum alloying elements is Si, but it is surprising hard to drive Si into solution in aluminum. Same with Ti, B, and Strontium. Metal suppliers sell master alloys that have these elements in aluminum wire and waffle chips at near Eutectic levels, and those will rapidly dissolve and can be added just before the pour.

    Some elements that will dissolve won't stay in solution as melt temps increase and approach their boiling point and are lost at the melt surface. So the alloys should be poured soon after adding the master alloys. I'll never figure out how they get some of the additions to steels to stay put!.......but Everder is quite stable in these regards and with the additional fluidity from Si, among the reasons it is so pleasurable to cast.

    To your original question, one of the biggest alloying challenges for hobbyists is knowing the true composition of your scrap. Often, small amounts of tramp metals can make big differences in the physical properties of alloys and obtaining high purity alloying metals can be quite expensive, thus the comments about whether it's really a worthwhile endeavor. -Your results may vary ;-)

    Best,
    Kelly
     
  5. Swiftsure 33

    Swiftsure 33 Copper

    Hi Pete,

    I sent Lou a message, looking forward to his reply. If his prices are still in the neighborhood of what what was posted in the linked thread that would pretty much put an end to any aspirations I might've had about cooking up my own casting stock. I am planning on ordering some manganese to play around with some of the the Ni-Mn aluminum bronzes though so I think I will still pick up some silicon to at least make an attempt at this.

    When I say stirring I'm thinking more of an up-and-down motion rather than a swirling one. I've made a few batches of the 953 I mentioned now and some portion of the Al always migrates to the surface and requires a bit of this type of agitation to prevent it from sitting on the top of the melt and turning to dross. I'm certainly not the expert here but perhaps a well timed stir (thinking as soon as the minor metals start hitting the surface) would help keep them in solution? There is also another thread where someone mentioned putting charcoal on the melt to keep oxygen away from the metal. I will see if I can find it again but if there is something to that effect which provides a barrier against the atmosphere I would think it would buy some more time for the reaction. In any case I'll keep researching for now and find out when I get around to giving it a try. At some point my time is just better spent buying materials and focusing on making my patterns, but few things come close to the satisfaction of producing a good-looking casting from a metal you alloyed yourself out of scrap.

    Charlie
     
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  6. Swiftsure 33

    Swiftsure 33 Copper

    Kelly

    Thanks for the generous info. Your videos actually inspired one of my first projects, a small lost foam aluminum plaque. I have very limited machining capability at the moment so chopped up car wheels have been sufficient for my aluminum projects. I do have some load bearing parts in mind for down the road but for anything critical like that to be cast as a one-off I would be more than happy to spend the money on pure ingots. Most of what I'm doing now is purely decorative or easily made oversized such that potential weaknesses are mitigated, and various scrap has served me well in this regard. That said, I was lucky to get my current bin of scrapped out Si bronze parts and I will soon be needing another source. The low percentages of the minor metals in everdur mean I could justify paying retail for them, assuming I can nail the alloying process. I do plan on purchasing powdered forms of the Si and Mn, and I am imagining something to the effect of a graphite cup as a plunging tool. I've seen something like that sold as a degassing plunger, or possibly make something out of heavy steel with a generous refractory coating. If I can get a good result in decorative castings it would be interesting to have a few samples strength tested as well. I have a lot of information yet to read here and elsewhere but if you have any books or other resources on these topics that you recommend I'd love to know. Cheers.
     
  7. Jammer

    Jammer Silver Banner Member

    Those bolts from Lou are great. I've finally started using some I got from him several years ago. I hope he still has some available. A little Phos/copper really helps with the pour.
     
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  8. metallab

    metallab Silver

    That is what I experienced when alloying Si bronze. I melted copper and added crumbled Ferrosilicon (70% Si, rest Fe) to it, but what a mess went it !
    A very thick syrupy and sticky substance was on top of the liquid metal. After pouring out the metal I had to scrape the still hot crap out of the crucible. After freezing and cooling the metal appeared pink and thus was almost pure copper. The frozen sticky substance was probably partly oxidized FeSi. Then I tried melting the FeSi with some copper in an electric arc using a welder with carbon rods to get the melt white hot and heat is over 1500 C, but the sticky and syrupy FeSi / Cu slag / dross (or somewhat in between) remained.
     
    Last edited: Apr 26, 2023
  9. Rasper

    Rasper Silver

    I have been making Everdur for years. I melt a heel of Everdur in the crucible. Enough that I can load scrap copper wire and push it below the surface so it doesn't oxidize. Then I add some silicon (not ferro silicon; why get that iron in your mix?) then some manganese. Then more copper wire, more silicon and more manganese until I have a full crucible. A bit of borax in the center mixed a bit and some beer bottle glass to gather the dross into a glob I can skim off in one lump and I pour ingots. I always pour ingots first and then re-melt them. It seems to make better alloy that way. Go figure.

    Richard
     
  10. Jason

    Jason Gold

    11bucks a pound SHIPPED is a good deal. Pay the man! I was paying 6.50 a pound back 4 or 5 years ago. With today's BS inflation AND shipping, I consider 11bucks a pound delivered a bargain!

    Yes you can make it, but if you are just starting out, you are going to have enough issues without creating new ones in the process.
    Got any friends in arizona or commiefornia? Industrial metal supply has great prices on CMX Sil-bronze. Get someone to send you some in a if it fits it ships box. Just INSURE it. The current high price of bronze is because of the price of copper and bronze is 94% copper. Unless you are machining tons off, you have very little waste. Sprues, pouring cups and all the bits and pieces go in the next melt with some fresh stuff. When I first started pouring sil-bronze, I had a bad habit of overheating it. Don't do that, pour only as hot as you need to make it go where you want.
     
    Tops likes this.
  11. Swiftsure 33

    Swiftsure 33 Copper

    Sounds like you've got the process down, I will try to follow this when I get to my first attempt. I am curious about how you are getting the the Si and Mn under the surface of the melt?
     
  12. Swiftsure 33

    Swiftsure 33 Copper

    It's not that I have a problem paying for the stuff, it's just that if I can make it reliably at half the price it seems like its at least worth a couple of attempts. Not to mention my stack of free scrap copper is ever-growing a la curbside treasures. But I do have some family out West so I appreciate the tip, I do suspect that making my own bronze will start to become more trouble than its worth if I want to attempt larger projects than what I'm doing now.
     
  13. Jason

    Jason Gold

    Go for it! You'll figure it out one way or the other.;)
    I sold all my scrap copper off and one of the guys here actually gave me the manganese and silica! I'll mess with alloying it some day when I'm Richards age. I often have to assemble my castings and that means a lot of tig welding. I need my filler rod to match my base metal, that alone is reason enough for me not to mess with a homemade brew. Most of us design, build, enginerd every thing on our own, sometimes it's just better to pick our battles wisely.
     
  14. Mantrid

    Mantrid Silver

    I melt a bit of silicon bronze in the crucible then add the silicon and manganese and they dissolve in the puddle. Then feed in the remaining copper. Dont waste fuel making ingots just use straight away on your casting
     
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  15. Rasper

    Rasper Silver

    My fuel is free so that is not an issue for me. I take my empty five gallon plastic jugs to the motorcycle shops and they fill them up with waste oil. They are glad to get rid of it. I find motorcycle oil is much cleaner than automotive oil.
    Probably why I seem to have better results if I pour ingots first is that it gives the silicon more time to dissolve in the copper. That does not happen in an instant. The silicon doesn't melt; it dissolves in an alloying process which takes a bit of time.

    Jason,
    I pour my welding rods when I pour the casting. That way the alloy is exactly the same color. Unfortunately I have to weld with an oxy/acetylene torch. My 6500 F. as compared to your 35,000 F. I'm too damn old to buy a TIG welder now. I try to plan my castings so I don't have to weld them. I do have a good bit of experience in welding .050 aluminum sheet metal with a gas torch, which helps, as the way aluminum and Everdur conduct heat away from the weld is similar.

    Richard
     
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  16. Mantrid

    Mantrid Silver

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