Information on metallurgy, casting and foundry work

[RCW]

New Question.

Will adding zinc to a questionable mix make it brighter?

Would someone please answer Charlie's very reasonable question?

I am afraid that I inadvertently hijacked his thread by asking about induction furnaces. Charlie, I apologize.

Please keep this thread going. I learn from each exchange. Don't most of you?

Thanks, Charlie for starting this one.

[steamin10]

I did, in the long winded post June 20th, page 3. I wont argue my opinion from here. I think I explained what I do fairly well. Follow at your own risk.

[Pipescs]

Ugh! When I say a 10% addition of zinc, that is a Swag on many times melted brass. This is where I am relying on color of the bar revert, as loss of the zinc will darken the alloy as more copper becomes evident.

Thanks Dave. Here is the part I believe you are mentioning.

As the brass will have some lead in it, I am assuming it will tarnish fairly quickly?

I am sorry I have not been paying attention to this thread. I have managed to get the Rust Bucket running on air and am now working on a the trailing truck for it along with a mock up for its cab. Looks like my next furnace project will be some aluminum Journal Boxes.

The pedestals will be steel and I am told aluminum will be a good material to mount the bearings in.

As to high jacking my thread, there is no such thing to me. It is all information transfer and I learn something every day.

[Pipescs]

New Question:

I am told that aluminum is a good material for a journal box when the pedestal is made of steel. The bearing is to be a roller type located in the aluminum block.

What are good add ins to make the Aluminum tougher when wearing on steel? I have heard copper wire helps.

[steamin10]

IMHO for the backyard guy, you want hard surface and low wear? Low silicon aluminum with a lot of copper. That means add about 3x the amount of the skull brass (bronze) in the pot (the heal of a just poured heat,) of aluminum extrusions. It should have a light yellow tinge, but is aluminum bronze that is hard with good wear characterics, and high strength. Again, consult the chart for the real compound alloy, and give it the best guess. A lttle lead will maintain machinability. Once more, the more lead, the greater the ductility to a point, but dont expect a lasting polish on anything that is leaded brass/bronze. Also, bell material has very low lead, a lead bell will not ring.

When alloying always melt the higher temperature metal, (copper- brass) and add the lower temp addition, ( aluminum-zinc-tin-lead) to assure complete solution mixing. Pouring a finger bar in sand can give you a quick check for color, strength, and bend testing, or pour a slug through water for a color test.

Complex journal boxes are the perfect excuse to explore lost wax/plaster process for fine measure and almost no machining. Only fit touchups are needed.

[RCW]

Question from an ignorant newby: Couldn't pouring copper into water produce a rather exciting spectacle? As in "explosion"?

[Harold_V]

Question from an ignorant newby: Couldn't pouring copper into water produce a rather exciting spectacle? As in "explosion"?

NO! Not so long as the body of water is large enough, of course. Don't do it in a cup. Don't pour to a vessel that doesn't have adequate depth, either.

The reverse, however, is a totally different matter. One would be wise to not introduce moisture to molten metal, especially in the way of what appears to be dry metal. Surface moisture can be instantly turned to steam, propelling molten metal from the crucible. Always preheat metal that is being introduced if the charge has already melted, as cold metal will condense enough moisture on the surface (from the furnace exhaust) to cause a steam explosion. Introduced metal should be heated beyond 212° for safety.

For years, I poured gold shot by that very process. So long as there's sufficient water to absorb all the heat without turning to steam (it takes a huge amount of energy for that to happen), all it does is quietly chill the molten metal, without oxidation. That's why Big Dave suggested pouring to water if you hope to see the color. What you see IS the color.

If the poured stream is hot enough and the pour lasts long enough, it can form a column of steam clear to the bottom of the vessel, with the metal remaining molten because the steam isolates the hot metal from the cool water. That has the potential to ruin your whole day. Don't ask me how I know this.

Harold

[steamin10]

Exactly to the point. We are interested in getting a button of a coupla ounces for a test. There is a U-tube thing with a japanese guy that starts his art medallions this way. I am only looking to get a disc to show the properties of what I have.

If you are sqeemish about the water, cast a finger bar, and cool it after is turns solid and get the bend test and color after polish, and airiness of what you have in the furnace. This only takes a coupla minutes, if you need to know.

A finger bar is similar to the Spanish Conqistador method of making easy to transport and divide bars of Gold and Silver. It is simply one or two finger trench made in damp sand and poured out into a roundish flat topped bar. Easy to do on top of any made up mold, or stock sand pile.