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Copper is harder to melt than I expected


NguyenHoang

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Hey, hope everyone enjoys this little story of me getting mentally destroyed by copper :)

I thought it would be fun to try melt down some copper to use for fittings for some knives. Using a charcoal forge, turned more into a furnace, I placed some stripped copper wire in a graphite crucible, aaaaannnnnnd….

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the crucible either shattered or just completely eroded before the copper got hot enough (I warmed up the crucible slowly over 20-30 minutes to avoid temperature shock). Copper 1, me 0

tossed the copper into the forge to see what would happen, it melted and I got some rough looking copper. 

I took the crucible, cut off the base, ground down the sides so that the base and the crucible sat flush, and covered it in high temp refractory mortar. Placed the copper in it once it cured and hit it directly with a propane torch, aaaaaaannnnd… nothing. It probably needed something more insulating. Copper 2, me 0.

placed it in the forge again. It survived longer than the new graphite crucible. However the graphite completely eroded within 30 minutes without the copper melting. With no surface to hold onto, the refractory didn’t look too safe to use so I binned it. Copper 3, me 0.

I took a steel pipe. Forged the ends shut and then folded it up to create a little steel crucible. Aaaaaannnnnndd….

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the copper refused to melt… until the steel melted and formed some abomination of steel/copper . The break in the steel was at the bottom yet somehow the copper traveled all the way up the pipe? Copper 4, me 0.

Not willing to be defeated but with nothing else to use, I took my homemade ceramic ingot mould, copper inside and left it in the forge. Aaaaaannnnd….

 

it actually worked this time (kind of). The ingot had large pores in it rendering it unusable so I threw it back in aaaaannnnnddd…

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yep the mould cracked before the copper melted this time.

so I made a little bowl from some mild steel, placed the copper it in and watched and waited for the copper melted and yep you guessed

it…A6CD7D9B-E1CF-449B-AF6E-900EED9258E3.thumb.jpeg.715b4575d2fa1b19b0c3e17f9fcc4832.jpeg

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The bowl nearly melted completely, save for a few pieces, taking the copper with it.

I don’t know if I just looked away at the wrong time but I swear the copper only melted when the steel started to melt.

I am now inclined to believe the melting point of copper > tungsten (joking of course!)

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I don't do any melting so I can't offer any help. Just be careful... Exploding crucibles filled with semi-molten metal sounds pretty dangerous... make sure you have all the required PPE.

Should you use flux? Do you have to degas the melted copper? Does an oxidizing charcoal fire degrade the crucible? I have no idea.. Do you know?

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Yeah exploding crucibles was my main concern. The graphite crucible was heated slowly to remove any moisture, the little homemade ingot mould was twice fired and then slow heated as well. The forge (A JABOD) was converted to a 'furnace' with just an opening at the front and the rest surrounded by fire brick, just to keep the heat in and to stop anything from flying out (mainly charcoal, for what ever reason the charcoal I bought likes to violently explode).

It was fun regardless, I am just curious about the weird steel copper baby that I created, I have no Idea what happened there.

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Crucibles issues: too oxidizing a fire!

Copper issues:  No flux and too oxidizing a fire---you are basically producing copper oxide that has a way higher a melting temp than pure copper.   I've melted a bunch of copper and fine silver using my coal forge in stainless steel creamers, (disposable, plan for one melt/pour per good heavy creamer till you get good and even then I think 4 was my limit!)  I used borax as a flux and DRY charcoal as a degasser.  

Making sure the fire is NOT oxidizing is important!!!!!

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