Copper now liquid

I’ve been playing around with many crushed aluminum cans and has worked out well. I’ve graduated to copper and brass and have hit a brick wall.

I constructed my own can crusher driven by a windshield wiper motor and with a lightning speed of 15 cpm (cans per minute).haha…. Anyway it works well.

I also built my own furnace from an old propane tank. I used steel fibers mixed into the 2” floor and the removable top (to prevent spalling or any detachment from the steel cover (4 stainless bolts were also used to help anchor the refractory concrete. I’ve reached 2200°. Anyway enough of my entry into melting metal…kind of,

I have moved up to copper and have unfortunately taken a crew steps backwards.

I was attempting to melt some junk copper and while I was placing these pieces (some were fairly large) old not see any copper in its liquid form. I believe I was asking my furnace to do to much too quickly. Tried for approx 60 min. Shut down the furnace and managed to remove the glob of copper and slagfrom the crucible this am.

Bottom line…any advice would certainly be appreciated. I’ve been melting for a few months and am somewhat proud of my accomplishments and do understand my failures which I would like to correct.

 

Hello G-Man43,
Possible to get a picture of the scene of the incident and any more written details on furnace, burner, crucible...?

 

Yes some photos of the furnace setup would be nice. At a guess you're going to need a higher flow rate of gas to reach temp faster and achieve a higher maximum temperature. Also molten copper absorbs oxygen over time which makes it less fluid and gives a spongy mess on cooling if any of my earlier results are anything to go by: lumps of copper full of tiny gas holes under magnification like sponge cake. The way around this is to add small amounts of phosphorus copper shot that reacts with the oxygen and forms dross that can be skimmed off. The effect doesn't last long so it's done shortly before pouring the metal.

 

I just joined and pretty much took the majority of my morning entering the text of which has some confusing explanations.

 

No worries, furnace look nice. Are you 'naturally aspirated' by the propane or using a fan/blower? I was pouring with a friend this last weekend and a small adjustment on the propane made a world of difference.

 

The burner is a Frosty T Burner design (works well)

hope the photos get thru…d

 

Nope…just using Frosty T Burner with a high pressure regulator

 

What size is your propane tank?, is it large enough to avoid freezing with the gas demand?.

 

Typical 20# … and it sits in a tub of water (a porox12”)…I believe my problem was self inflicted. Instead of melting a small quantity, I pretty much jammed too much and somehow managed to disrupt the melting process (if that makes sense). My crucible was very hot (glowing red) when I attempted to pour. First off in I’m opinion I used a crucible that was goo large. It was very difficult to remove with my tongs (never liked them for this process ordered a new style where I am above the furnace with a scissor like tong…attached).
I managed to remove the glob of copper from the crucible without much of a problem.
Anyway like I saltwater previously “pilot error”. Gotta get on that bike and ride again.

 

Copper is one of the hardest metals to pour. It hates Oxygen or loves it depending on how you look at it. It absorbs the O2 and turns into a glob. Keep O2 away by running your burner fuel rich and throw some chunks of charcoal on top of the copper. Use real hardwood charcoal if you have it, briquets would work I guess there is just other stuff in them. Don't stir much or fiddle with it, and pour quickly into a closed mold if possible.

Just starting in casting it might help to stick with the easier metals Like Aluminum, Not cans, try to get some good alloy like auto rims. Brass is easy but there is a slight danger of zinc fumes so I like using Bronze alloys like Everdur or a Tin Bronze.

 

Got it.,.I use lump charcoal…is that appropriate?

 

What is your suggestion regarding my pressure gauge …I’ve got to 3 on my gauge.

 

It will work.

 

What is your gauge reading? It looks like Millipascals. Since your using natural draft you need to tune it until it's putting out the most heat and then just turn up the fuel a tiny bit. You want to keep the heat inside the furnace not blasting out of the top.

 

A 20 pound bottle with natural aspiration should work if Bigstack D's videos are anything to go by. A K type thermocouple maybe one of those cheap stainless sleeved ones coming in through a hole about halfway up the side of the crucible into the chamber (sealed with clay) and hooked up to a digital readout would let you tune for the hottest flame mixture very easily. It'll die at iron temps of 1350 deg C but should be fine for several runs at bronze and brass temps. You'd want an orange to yellow temperature to the melt for good results.

 

Sounds like a plan…I am still trying to digest my settings.

The black numbers are psig
The blue numbers are kPa which is used with the metric system.
1 kPa = .145 psi
This is a 100 X kPa gauge so the blue 1 = 100 kPa = 14.5 psi
This gauge is reading 9 psi or approx 60 kPa

Info from a good friend

 

I didn't notice that. I was wondering what the scabble was supposed to be??

 

I’m confused…haven’t seen #7 /#9