Author Topic: Aluminum Copper Alloy Experiment  (Read 16271 times)

Offline Joules

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Re: Aluminum Copper Alloy Experiment
« Reply #75 on: October 31, 2017, 11:57:04 AM »
The slag is dross and impurities that precipitate out of the metal to the melt/crucible wall.   I was thinking your aluminium bronze wouldn't be true, but as you created it in a steel crucible it will have pulled some iron out of the metal into the melt.   Casting molten metal into moulds is almost a chill process as the temperature drops off quite rapidly.  if you can slow the cooling to extended times you will form large or even single crystal components as in Rolls Royce turbine blades, though they have a little more trickery than just that.   Watching the big forge hammers "beat the crap out" of metal is probably the simplest way of explaining whats happening.   You are purifying the metal by squeezing out impurities that would remain in the metal and create weakness across the grain structure.  The heat allows the impurities to migrate through the metal, as when it cools they are locked in.
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline NormanV

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Re: Aluminum Copper Alloy Experiment
« Reply #76 on: October 31, 2017, 12:17:42 PM »
Thank you Joules for taking the time to read my questions and to reply. What you say makes sense. Now I just have to translate that into action and make my metal machinable.

Offline Joules

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Re: Aluminum Copper Alloy Experiment
« Reply #77 on: October 31, 2017, 12:27:15 PM »
Norman, as mentioned by others.  It work hardens rapidy and is really abrasive on HSS tooling.  You know when you have it wrong as the metal screams at you, and watch if you drill it, the metal is really grabby and will clamp down on a drill bit and shatter it.   LOL those have been my experiences with Ally Bronze, does make great bearings though.
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline NormanV

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Re: Aluminum Copper Alloy Experiment
« Reply #78 on: October 31, 2017, 12:39:36 PM »
I've just been into the workshop and tried to drill it. After my heat treatment it seems to be harder than ever!   :doh:
At the moment it feels very disappointing, I searched for a long time to find some scrap copper. It took a long time to melt it and the result is....... difficult!
This is the problem when you experiment to try to save money, it can turn out cheaper to buy the thing that seemed so expensive in the first place.
No worries, I have learned something new and I will remember it because I did it and did not just read it.

Offline mattinker

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Re: Aluminum Copper Alloy Experiment
« Reply #79 on: October 31, 2017, 01:41:24 PM »
The answer to your question about why your alloy is not sof when cooling down after casting might be in this article.

http://mit.imt.si/Revija/izvodi/mit144/slama.pdf

The scale forming on the outside of you steel crucible looks like oxidisation.

Have fun with your traction engine on the beach!

Cheers, Matthew

Offline Joules

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Re: Aluminum Copper Alloy Experiment
« Reply #80 on: October 31, 2017, 02:08:06 PM »
What he said above....   :thumbup:

High heat and long cool down times, in hours not minutes.

If i didn't have the furnace, it would be wrapped in stainless shim and put in the the stove with coals burning bright for 30mins+ then run the stove down slow and move the metal out of the hot zone.   Might as well do some jacket potatoes as the heat comes down.    :drool:
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline NormanV

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Re: Aluminum Copper Alloy Experiment
« Reply #81 on: November 01, 2017, 03:17:36 PM »
I put it in the furnace, heated it up to a nice red heat and then blocked the orifices. I'll leave it till the morning to cool and then see how it is tomorrow.

Offline David Jupp

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Re: Aluminum Copper Alloy Experiment
« Reply #82 on: November 01, 2017, 04:05:50 PM »
I noticed that some of the stuff quoted mentioned a high temp solution heat treat and quench to soften, followed by a lower temp age hardening, whilst other stuff seemed to suggest a very slow cool from high temperature for softest condition.  Seems like some possible confusion here, or that things are very dependent on actual alloy composition.

If composition is not very close to a published spec, expect that you may have to experiment to find exactly what gives the behaviour you desire (perhaps limited by heat treatment facilities available).



Offline sparky961

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Re: Aluminum Copper Alloy Experiment
« Reply #83 on: November 01, 2017, 09:20:00 PM »
This is the problem when you experiment to try to save money, it can turn out cheaper to buy the thing that seemed so expensive in the first place.

It's taken half my life for this one to finally sink in!  I still have days where I temporarily forget.

No worries, I have learned something new and I will remember it because I did it and did not just read it.

But alas, this is why I don't regret the learning process.

Offline NormanV

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Re: Aluminum Copper Alloy Experiment
« Reply #84 on: November 03, 2017, 09:00:43 AM »
This metal melting mallarky is mystifying! My first attempt at making aluminium bronze took nearly 5 hours to melt 3kg of copper plus 300g of aluminium. This produced an alloy that was almost unmachinable. Even after annealing. I decided to dilute it 50%.
I placed 2kg of aluminium in the crucible and when that was melted I added 2.3kg of my bronze. The total time to when it was ready to pour was 1hr50min. I was ready for another 4-5 hour stint!
I am waiting for it to cool down to see whether I have an alloy that will do the job.
This is such fun!

Offline NormanV

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Re: Aluminum Copper Alloy Experiment
« Reply #85 on: November 03, 2017, 09:42:49 AM »
I've just tested a piece. A file cuts it and it compares quite well with steel in its resistance. It turns ok but not a great finish and it is drillable. I'm going to use it for the bearings for my traction engine which is not going to see a lot of use so it should be good enough.

Offline mattinker

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Re: Aluminum Copper Alloy Experiment
« Reply #86 on: November 03, 2017, 09:48:30 AM »
You melted the Al first in the second attempt. Molten Al is very corrosive and will dissolve copper at well below it's melting point I think you will find the melting point of your Al bronze should be just a little above that of the Aluminium.

Regards, Matthew

Offline seadog

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Re: Aluminum Copper Alloy Experiment
« Reply #87 on: November 03, 2017, 10:23:10 AM »
I don't think it's corrosive. What does happen is that a eutectic alloy forms which has a much lower melting point than the copper.

Offline mattinker

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Re: Aluminum Copper Alloy Experiment
« Reply #88 on: November 03, 2017, 10:56:10 AM »
I don't think it's corrosive. What does happen is that a eutectic alloy forms which has a much lower melting point than the copper.
I don't doubt you for a minut! I was told it was corrosive, but I think your explanation sounds better! I know that the resulting alloy has a lower melting point than copper. I can't find it now, but if I remember correctly, it's just a little over Al, which is very handy.

Offline seadog

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Re: Aluminum Copper Alloy Experiment
« Reply #89 on: November 03, 2017, 01:38:01 PM »
When I was doing Engineering Science, a new A level for 1968, our teacher demonstrated this by heating a piece of copper strip whilst rubbing an aluminium rod against it. When the temperature reached the melting point of aluminium he  was able to push the rod through the copper. I don't think it reached more than a dull red heat.

Offline SwarfnStuff

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Re: Aluminum Copper Alloy Experiment
« Reply #90 on: November 04, 2017, 01:32:11 AM »
These last few posts reinforce to me the reason I like this forum. "I learn stuff."  :smart:
   In this case it actually confirmed what I sort of knew but Eutectic was a word I failed to recall but sounded sort of familiar.
   Thanks
John B
Converting good metal into swarf sometimes ending up with something useful. ;-)

Offline NormanV

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Re: Aluminum Copper Alloy Experiment
« Reply #91 on: November 04, 2017, 03:02:05 PM »
I've had a go at making a part. It turned like cast iron with dust instead of curly swarf. It drilled but blunted the drills and it was too brittle to do anything with it.
Not a success.

Offline PekkaNF

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Re: Aluminum Copper Alloy Experiment
« Reply #92 on: November 04, 2017, 03:19:34 PM »
Aluminium alloys can be funny. My brother told few years back about some rivets used in aeroplanes. Can't remember exactly how it went but there was a very exact heat treatmen cycle and if I remember right there was a little time, something like few hours rivets kept froxen, really cold, something like -60C just before use and riveted in very conrolled manner and then they age hardened in two hours or so to full hardness.

Pekka

Offline Meldonmech

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Re: Aluminum Copper Alloy Experiment
« Reply #93 on: November 08, 2017, 07:33:50 AM »
 
   I have found this to be a very interesting topic, with practical experience combined with technical facts.
 I tried to produce a copper/aluminium alloy some years ago using copper wire to the melt. The percentage copper was quite small, and the difference in machined surface finish was similar. The intention was to produce duralumin but I never got round to doing any strength or wear tests.
 On my next melt, the aluminium is from the same source and I will use copper wire. From what I can remember only a small percentage of copper is required, to substantially increase the strength. I also have some small brass pipe  fittings and use some of these in a melt to compare  the results.

                                                                                                      Cheers David

Offline NormanV

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Re: Aluminum Copper Alloy Experiment
« Reply #94 on: November 10, 2017, 02:23:30 PM »
My last post on this subject. (famous last words!)
I had cast an ingot 100x40x250mm from the 50:50 aluminium:copper mix. I took it in my workshop and dropped it half metre onto a concrete floor. It snapped in two!
I don't think that this alloy has any practical use.
I will save it to use to add small amounts of copper to future melts.
This alloying business is quite complicated!