Beginner caster

[scote621]

Hello all,

I am a new member and this is my first post.  I just wanted to share my first few backyard metal casting projects, all of the pics posted are with rough sanding/grinding only, I hope to take some new pictures of the finished products soon.  I have found a lot of very helpful information on this site and would like to pass on my thanks to all the experienced members who have taken time to post tutorials for us newbies.

So far I have learned that I can do this and that I am more handy than I thought, but that each project comes out a bit different than what is in my head, and that each one has it's own lessons to learn from and take to the next project.

1. very first project, learned to make sure the casting molds are the right size for the amount of metal your crucible can fit, both were intended to have integrated stands but did I not have enough aluminum to cast the stand.

2. couple of ingots, made an aluminum bronze by melting copper into the crucible that still had some aluminum left over from a previous pour (unintentional but I like the result and may make a small bronze decorative knife blade from this ingot)

3. A present for my wife (the heart with our anniversary date) and a mother's day gift for my mom (who is a Disney Fanatic).

4. Rough sand on my F-22 profile desk sculpture (since sanded to a nice smooth finish)

5. Bathroom towel rack (this is a finished product, both my wife and I like an industrial unfinished look for our house's style)

6. towel rack in use

7. first attempt at a copper axed head, rough finish for now.  I plan on mounting on a dark stained custom wood handle.

 

[mutant]

Nice! Digging the towel rack. I also have a backyard foundry. I've done mostly lost foam casting but plan on making some patterns. I haven't tried bronze yet

[scote621]

Thanks, I was happy with how it came out.  I should have specified that all of my projects were done with the lost foam technique as well.  I am currently using the mini-foundry designed by Grant Thompson (kingofrandom on youtube) heated with a homemade ron reil style burner.  I know it is not an ideal refractory material using the plaster and sand but it works for now, I have found that i can get 2-3 days or weekend projecting out of it as long as I am careful not to jostle the foundry too much before the refractory has to be patched (easy enough to do takes about 10 minutes to mix a bit more up and line the sides, lot cheaper than investing in real castable high temp refractory for now).  Though I will say I do ultimately plan on buying better material in the future.  And copper melting is much more taxing on it due to the longer run times (prob takes 20-30 minutes of full heat with cover on for melting copper pieces).

If you try bronze/copper be careful seems to run faster/pours more easily out of the crucible.  In fact while making my axe head I think i did not use enough sand around it and the gasses from the foam vaporizing were strong enough to force a seam in the sand open and allowed molten copper to spill out through it.  Thankfully i was using a large rectangular rubbermaid container for my casting and it was all contained but that could have been bad if i tried it in a 5 gallon bucket.

[scote621]

Decided i did not like how the axe head came out and wanted to start anew.  Picked up a hatchet handle and mocked up a new foam head, made sure to fit the head prior to pouring the copper.  I am waffling between using copper/aluminum bronze or a true 100% copper head.  I love the look of the smooth finished copper, and this is soley a decorative piece so I am leaning more on that side of the fence.  Planning on a dark wood stain for the handle as well.

[ThomasPowers]

my suggestion would be silicon bronze

[David Durman]

I recently made some bronze with 12.5% tin and rather like the high blonde color I got out of it.

 

EDIT: Might help if I attached the picture. This is a very rough polish, mostly just to remove scale.

 

[ThomasPowers]

I was thinking of the working properties of silicon bronze...

[David Durman]

Fair enough. I was merely suggesting the 12.5% tin bronze because I like the color and he specified that this is a purely decorative piece.

[scote621]

David,

That pic sure shows some potential for a nice looking metal.  The below pic is an ingot of aluminum bronze (on left) I made by not clearing out my crucible after an aluminum melt and adding copper to it.  I have no idea on the ratio of aluminum to copper, but i would say it falls in the 5-10% range that is commonly cited for aluminum bronzes.

 

 

19 minutes ago, ThomasPowers said:

I was thinking of the working properties of silicon bronze...

Do you make your own silicon bronze or are you sourcing it ready for casting?

[ThomasPowers]

buying it for casting.  Most of my home made copper alloys are around 90:10  copper:tin  Medieval examples in Europe ranged rather widely...

[David Durman]

Thomas is right; just buying silicone bronze is going to be the easiest, but since this is a decorative piece then you will probably be more satisfied with making your own bronze so you can control the color. Thomas's 90:10 mix is by far the most common alloy, and probably what would be most commonly thought of as a bronze color. My 87.5:12.5 is going to give you that blonde color while mixes closer to 92:8 are going to give you a redder, darker color. The typical range I've seen for 'bronze' is 8-12% tin, but of course there are all sorts of other bronzes you can make if you are looking for a specific color. I would look up different bronze types and look at the images to find the color you want; statuary bronze for example is 97 Cu:2 Sn:1 Zn, but I would strongly caution against using any Zinc or Lead in your mix unless you can get some experienced supervision since both are potentially toxic. If you do decide to order some type of bronze rather than making it pay special attention to its alloy composition. 

[ThomasPowers]

Don't forget speculum metal among the "interesting" historical copper alloys.  Here in the USA I tend to get my Tin from rotometals.com and source my copper locally as wire and pipe; both traditionally fairly pure copper and I cut off any sweated fittings to avoid lead. (most of my tin is used retinning copper cooking pots so I want "clean" metal)

[David Durman]

When I made that bronze I ordered these tin ingots off of ebay and order 2 Two Pound Copper Bullion Ingots from Provident Metals. Certainly not the cheapest method. 

[scote621]

On 4/27/2016 at 11:18 AM, ThomasPowers said:

Don't forget speculum metal among the "interesting" historical copper alloys.  Here in the USA I tend to get my Tin from rotometals.com and source my copper locally as wire and pipe; both traditionally fairly pure copper and I cut off any sweated fittings to avoid lead. (most of my tin is used retinning copper cooking pots so I want "clean" metal)

So I attempted to pour the axe head last night and it was a spectacular fail (Well it could have been much worse as this isn't the safest hobby haha).  I am 99% sure I made a bad batch of speculum.  I weighed out my copper and aluminum and had it set for 8.5% aluminum which was in the range of 5-10% I read that is common for aluminum bronzes.  BUT I was stupid and against my scientifically educated brain (I have a B.S in biochemistry) decided I could add another aluminum ingot a few more small copper ones and would estimate the ratio in the middle of the melt.  I did this because i was not sure i had the required volume in the crucible for my pour.  I was also rushing as this was being done on a weekday night and I did not have much time.  So I had the melt going well and threw in the last small copper chunk and gave it a couple minutes and then attempted to pour it, little did i know the copper had not melted yet and stuck to the bottom of the crucible and acted as a heat sink to lower the temp and solidify a good amount of the bottom of the melt...so i poured the crucible out into my mold and was surprised to see it was not all melted (shame on me for not checking).  I did skim the top slag off but there wasn't that much and I didn't dig down deep like i should have which would have allowed me to discover the problem.  Anyways I only had about half the metal i needed in the pour so now the foam mold is destroyed and I know my project will need to go back to square one.  I pull out the metal after it solidied expecting to see a half aluminum bronze axe head.  BUT all i got was a grainy very fragile grey looking metal that crumbled with force applied to it, the only thing i can think of is the almuminum % was well over 25% and it was a poor alloy.

I am taking this a learning experience and now know to not do that, to weigh it and stick with it.  I also think using small copper ingots is leading to a ton of slag (copper oxide) I think i will try sanding and filing them down to rid them of the oxide layer for the ones i already have made, and then in the future try to not make ingots unless necessary and just go right from scrap copper to mold pouring.  I have attached a pic and youtube link to my furnace set up in action.

https://youtu.be/wUagRzIDzyM

 

Preview YouTube video FurnaceFurnace

 

 

 

[ThomasPowers]

Have you looked up the melting temperature of Al and the melting temperature of Cu?  

How are you degassing it?

[scote621]

49 minutes ago, ThomasPowers said:

Have you looked up the melting temperature of Al and the melting temperature of Cu?  

How are you degassing it?

I am familiar with the melting points aluminum is around 1200F and copper is around 1980F I believe.  I have not done any degassing, I am not familiar with that process.  I had one successful pour of molten copper and all I did was melt it from scrap fittings, pipes etc then skim the slag off and pour it.  The only issue with that casting was my sand cracked and allowed some of it to leak as i did not pack the sand tightly enough.  

I have seen some threads that state using charcoal on top of the copper can help prevent oxidation but I have not tried that yet.   

 

This is the copper from the mold I was able to pour.

[David Durman]

I had success with degassing copper/bronze by throwing in a handful of crushed charcoal and letting it burn for a minute before pouring. It worked well enough, but as I understand it there are better fluxes you can use but bronzes general shouldn't need much degassing if any, and aluminum doesn't need any at all. An interesting method someone told me was to put in some glass after your metals; the glass melts and floats to the top, sealing your metal away from the air. When you go to pour you just break the glass. I don't really think, though, that would need much beyond some crushed charcoal. 

Based on what you are saying, I would be largely concerned with the providence of your metals. If you are confident that they are fairly pure, then I would suggest cleaning them thoroughly prior to melting. The professor I had in my class will tell you all day about how temperamental aluminum is in regards to cleanliness. Is there any particular reason that you want to go with an aluminum bronze aside from that simply being the materials you have on hand, if I may ask? If all else fails, you can go the more expensive route of ordering copper bullion so you can eliminate it as a contaminant candidate.

[scote621]

So attempt 2 came out much better but still not exactly what I envisioned. I love the color of the alloy, I measured it around 10%Al 90% Cu before the melt and think I had a successful alloy produced. What I didn't like was the final finis . It had some cracks and porosity issues I think I needed a longer sprue and more finally packed sand. The sprue turned into a huge mass of metal I had to cut and grind down. The axe was sanded down with 60 all the way through to 800grit and is very smooth and shiny but the larger cracks prevented the smooth mirror finish I was after. I will probably keep this for a bit but it may end up getting melted down in the future for another project or attempt on a more refined axe head. 

[ThomasPowers]

If you are using the term porosity correctly it's due to not degassing the melt properly.

[scote621]

12 hours ago, David Durman said:

I had success with degassing copper/bronze by throwing in a handful of crushed charcoal and letting it burn for a minute before pouring. It worked well enough, but as I understand it there are better fluxes you can use but bronzes general shouldn't need much degassing if any, and aluminum doesn't need any at all. An interesting method someone told me was to put in some glass after your metals; the glass melts and floats to the top, sealing your metal away from the air. When you go to pour you just break the glass. I don't really think, though, that would need much beyond some crushed charcoal. 

Based on what you are saying, I would be largely concerned with the providence of your metals. If you are confident that they are fairly pure, then I would suggest cleaning them thoroughly prior to melting. The professor I had in my class will tell you all day about how temperamental aluminum is in regards to cleanliness. Is there any particular reason that you want to go with an aluminum bronze aside from that simply being the materials you have on hand, if I may ask? If all else fails, you can go the more expensive route of ordering copper bullion so you can eliminate it as a contaminant candidate.

Thanks for the info. Since my last post I did some research and also heard about crushed charcoal, I will try that the next time. I like the idea of finding scrap copper and aluminum for cheap at yard sales etc and using that. I also have a friend who is a commercial electrician and got me some scrap aluminum thick Guage stripped wire that was super clean/pure for free. I got like 20lbs from him and it had almost no dross at all. 

2 minutes ago, ThomasPowers said:

If you are using the term porosity correctly it's due to not degassing the melt properly.

I may not be using it correctly but maybe the latest pics I showed will allow you to see what I'm referring to. I fully understand I am a complete rookie at this and I am old enough now to know how little I actually know about something  and take guidance constructively from those with more experience. 

[David Durman]

Well, let's go through some of your setup and see if we can figure out the issue. What are you using for your sand? Better yet, do you have a picture(s) with your mold already made and your sprues cut into it? Walk us through your pour procedure; how long past melt are you letting your crucible sit in the foundry (overheating is a serious concern with bronze)? Do you have a picture of your dross (I'm not sure what you mean by not a lot)? More information will help someone smart, like Thomas, figure out what could be the issue. As it stands, I would agree that it is possibly a degassing issue; I've never had a degassing issue with bronze but 1) I haven't done too much bronze casting and, 2) I always use a handful of crushed charcoal so I've never actually seen if there is an issue when doing a straight casting. 

[scote621]

49 minutes ago, David Durman said:

Well, let's go through some of your setup and see if we can figure out the issue. What are you using for your sand? Better yet, do you have a picture(s) with your mold already made and your sprues cut into it? Walk us through your pour procedure; how long past melt are you letting your crucible sit in the foundry (overheating is a serious concern with bronze)? Do you have a picture of your dross (I'm not sure what you mean by not a lot)? More information will help someone smart, like Thomas, figure out what could be the issue. As it stands, I would agree that it is possibly a degassing issue; I've never had a degassing issue with bronze but 1) I haven't done too much bronze casting and, 2) I always use a handful of crushed charcoal so I've never actually seen if there is an issue when doing a straight casting. 

Here is a quick and dirty diagram of my set up, the orange outline is a 5 gallon home depot bucket, the brown is home depot play sand that has some moisture i.e. not 100% dry but not any where close to being wet enough to worry about molten metal contacting to much moisture.  The yellow is my axe template, and the pink is my sprue.  I tried to estimate the scale as best i could i think i should have buried the axe deeper and had less of the sprue sticking out.  I am thinking one mistake is that i did not have a second smaller vent sprue.  I also included a representation of the mass of metal that came out before all the cutting/grinding i did with my angle grinder.

As far as heating, it takes awhile to get the bronze melted in my foundry I would say at least 30-40 minutes of heating.  I started with and aluminum ingot and some copper and once there was a small pool of liquid i would slowing add more of the copper, my thought was that the aluminum already being molten might help cover the copper and prevent copper oxide from forming.  The copper ingots though were not melting quickly so i only added a few of them and then since i had a good idea of how much copper i needed i used a roll of scrap 1/2inch diameter copper pipe i had acquired and slowing feed that in, i was actually able to get an idea of the color of the alloy by doing this as when i would pull out the copper piping there was a reside on the end that was showing me the color after it had cooled for a couple minutes.  Using that process i filled up the crucible and then waited a couple minutes in order to make sure it was a bit over melting point, then shut off the gas and pulled the crucible out for pouring.  I would say that the time from pulling the crucible to pouring took less than 45 seconds.

[ThomasPowers]

Definitely a vent (or two) needed.  The time to pull and pour is good, the time hot is what can cause problems with gas absorption, your method would promote that in my opinion.  I use a DRY charcoal piece held in tongs to stir my melt to help degas it and save out large pieces when I use chunk charcoal for forging for this purpose.

 

I generally use petrobond oil sand and have even transferred fingerprints (accidentally) using it.

[scote621]

3 minutes ago, ThomasPowers said:

Definitely a vent (or two) needed.  The time to pull and pour is good, the time hot is what can cause problems with gas absorption, your method would promote that in my opinion.  I use a DRY charcoal piece held in tongs to stir my melt to help degas it and save out large pieces when I use chunk charcoal for forging for this purpose.

 

I generally use petrobond oil sand and have even transferred fingerprints (accidentally) using it.

I like the idea you had with the charcoal and tongs, I will try that next time I work with copper/bronze.  I will also use a vent hole or two in the future.  Are you making your own casting sand or buying it?

[ThomasPowers]

I got a couple hundred pounds when I went to a school auction and am slowly working my way through that; mainly doing knife guards and pommels and other small stuff.  I took a brass casting class given out of hours at a local university back around 1983/1984 and that got me started.