coal furnace help

[Anonymous]

I tried to build a furnace using a flower pot and charcoal for the heat. I soaked the coal with lighter fuel before i got started but the fire still didn't last. The problem is, it wasn't hot enough to melt the copper i was trying to melt. I did not use a fan. Could this be the reason? how do I properly use a coal furnace to melt copper?

 

[Anonymous]

you need to use coke or charcoal also need to have a air source of some sort.

I am working on building a melting furnace from an old propane moble home furnace. When complete I will post pictures and instructions to the forum.

Copper looses heat real fast so you will have a hard time keeping copper molten to pour the mold.

What are you using for a crucible? If you are using iron the copper will dissolve it and spill into the furnace (best case) or on you or something you value (worst case).

Sorry skipped over the part were you said charcoal, if it is commercial like kingsford or something it has a lot of fillers and will not work so well.
Better to make your own with scrap wood.

I used a 5 gal metal can with a lid, poke a small hole in the lid, load with wood and build a fire or heat the wood in some other way, lite the smoke that comes out of the hole on fire when it goes out plug the hole with nail or something that fits to block out the air and turn off the heat, then let it cool and you will have good charcoal that will burn better and hotter with less ash to get in the way of melting your metal.

 

[bmgold]

I had, at one time, a homemade foundry furnace built out of a 5 gallon metal bucket lined with fire clay and used a vacuum cleaner or a hair drier (with the heating element unhooked) to blow air into the bottom through a piece of exhaust pipe to keep the heat away from plastic hoses. I never tried melting copper but it did melt aluminum.

For fuel I used charcoal or regular soft coal. I even used straight wood when I didn't have charcoal. The wood may or may not get hot enough to melt copper but I think the charcoal or coal should get plenty hot enough. I once used too much air and it melted/burned a hole through the steel pipe crucible I was using to melt the aluminum in and spilled it into the driveway. No harm done except to the crucible since it was a dirt driveway but be careful of fire danger and burn danger. Hot, molten metals and any moisture is a bad combination. A teacher in high school once got burnt pretty bad from spilled aluminum and kept his aluminum covered safety glass to show the students that it could have been a lot worse.

Also, for aluminum I didn't need any sort of flux but I expect that copper would need some type of flux. Maybe borax but I don't know for sure. The temperature of copper would also be higher than aluminum so a steel pipe crucible might not work. Again, I don't know. I never got very good at the sand casting game and moved on to other hobbies.

 

[Harold_V]

The temperature of copper would also be higher than aluminum so a steel pipe crucible might not work.

Metallic items used as a crucible are, at best, a horrible idea. Molten metals are strong solvents of other metals, so not only will your metallic "crucible" be destroyed, but you contaminate the charge with the dissolved "crucible", a word I'm using very loosely in this conversation.

When you contaminate an alloy with unwanted substances, it can lose all of its desired properties. Traces of lead in gold, for example, render it brittle as glass. Iron in aluminum is a source of coarse crystal development.

If you must use a metallic vessel for melting, it should be covered with a refractory material. There are refractory washes available from supply houses.

Harold

 

[bmgold]

Thanks again Harold, you are a great asset to this forum.

I didn't consider a refactory wash to the "crucible". My problems were more with the sand molds being too wet and not enough venting but the contamination would have been a problem too.

I can't imagine the amount of time you must spend helping out on this forum but thanks for doing it.

 

[Oz]

Do not even think of venting to keep you safe with a sand mold that is wet or even damp. It is the fastest way to get a face full of molten metal from a steam explosion.

 

[bmgold]

I hesitate posting any more on this topic since it is a bit off topic and I just got my dvd's from Lazersteve but:

http://en.wikipedia.org/wiki/Molding_sand

"Green sand is not green in color, but "green" in the sense that it is used in a wet state (akin to green wood). According to the Cast Metals Federation website, an alternative casting method is to heat-dry the molded sand before pouring the molten metal. This dry sand casting process results in a more rigid mold better suited to heavier castings"

I'm going to watch my new dvd's now.

 

[Oz]

I have used green sand with cope and drag casting and talc for a release, but thanks for the link. My apologies if by “wet” you meant something other than moisture but it is very important that others do not think they can have a damp mold of any kind and pour in molten metal. For the record I do not see it as “off topic” as many here melt, pour, and cast molten PMs.

Again I meant no disrespect, I just like to see people safe.

 

[Harold_V]

I can't imagine the amount of time you must spend helping out on this forum but thanks for doing it.

All it takes to get me to talk is to remember the laughs I received from those that had knowledge but refused to share it with me when I was trying to learn to refine. I succeeded in spite of them, and feel I owe it to them, more or less rubbing their noses in my success.

My reward comes from seeing others achieve. What better way to pass on one's skills and knowledge, such as they are?

Harold

 

[Anonymous]

I tried to build a furnace using a flower pot and charcoal for the heat. I soaked the coal with lighter fuel before i got started but the fire still didn't last. The problem is, it wasn't hot enough to melt the copper i was trying to melt. I did not use a fan. Could this be the reason? how do I properly use a coal furnace to melt copper?

To light coal takes a bit of practice. Wad up some newspaper real tight. let it start to burn. then turn on your blower. work with a light volume of air and adjust as needed.

A note on this is that as ink and paper compositions have changed in the last decade newspaper does not always burn as good as it did. Also water based inks leave the paper somewhat moist. the paper needs to be dry as possible.

This is how I light my forge for Blackmithing.