Information on metallurgy, casting and foundry work

Home enthusiasts discuss their Foundry & Casting work.

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Pipescs
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Information on metallurgy, casting and foundry work

Post by Pipescs » Sun Jun 16, 2013 8:40 pm

RCW this title should look familiar to you as I pirated it from your last post Graham's Thread.

A lot of great information was being tossed around and I thought we should bring it all to one place.

It would appear that Big Dave is our resident knowledge base on this subject so I will lead this thread off with a question to him on technique.

Being a hobbyist that built a home made, oil fired, crucible furnace, I have melted Aluminum Scrap, Brass Scrap from my local junk yard and Silicon Bronze ingots I purchased in Pennsylvania from the Lancaster Foundry Supply. (Great guys to do business with by the way). I believe I represent the average guy in the hobby right now. We can melt metal but that does not guarantee a good, usable part at the end of the day.

The question for the day for Big Dave:

When dealing with scrap brass so far I have purchased it as industrial sized, used plumbing fittings. I am assuming it is a red or yellow brass by what I have read. Locally it is 2.00 per pound with the new ingots of bronze being 5.00 per pound. Hence my love for scrap material.

I understand that once it was melted and cast as the original part that something was lost.
Then after I have melted it again I end up with ingots I pour when the mold is full. Now it will have been melted three times should I use it again.

What material and how much by weight percentage should we put back into the crucible? You might mention how it should be done also.


Charlie
Charlie Pipes
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steamin10
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Re: Information on metallurgy, casting and foundry work

Post by steamin10 » Sun Jun 16, 2013 11:45 pm

Mr C Pipes: You embarass me with your salute. I am just a guy that travelled far, and do have very definate limits.

To much credit for being an expert, just had some practice and numerous failures. It is more important to understand the failures for pouring misruns, and oxidized parts that are pourous. I have enjoyed watching you accomplish in such a short time, some very solid methodology, and recover from some mistakes, not really evident when you started. Because of the costs, the learning curve can be quite brutal, and more than one hobbiest has given up on the whole deal and written the process off. OK, then pay a foundry, to do your bidding. Not wholly viable either if your patterns are flawed. So it becomes a process all its own. But then, this hobby is for those people that tend to do for themselves anyway. There are a lot of people that dont understand why you want to get dirty, playing with such an expensive toy, when there are boats, watercraft, classic cars, and Ninetendo to occupy their time. Not to mention buying a lot of exotic equipment (for the average homeowner) to put little metal bits in the carpet.

For me, it is a lifetime avorice to enable myself with tools and book knowledge to tackle all the jobs I come across, because I am insatiably curious. I am also seen as a windbag at times, when asked about what time it is, I go into building a watch or sundial. TMI. (tooo much information)! yet I run into people that believe they can do anything with 'I can ...' statements, that dont know a hill of beans about what actually happens and must be done. While they brag about certain things, they actually do little and get things done by hiring welding, for example, because they have little interest in owning a machine, or doing other projects. They are just outside the loop. They tend towards instant answers, guru-ish, and by some simple answer are now all knowing. PHap! Good luck with that. Give me someone who has singed his eybrows, burnt his fingers, melted his favorite swoosh shoe soles, that asks a key question, and I will show you a success story in the making. Given the right information, he will get it.

I will add to this thread directly and to the point of your question, as my day has run long here, and convey some of the things that I can do at home, that I believe have helped me in the process of producing castings for my projects, and controlling the metals I try to use. Some things may be a bit off, but it is what can be home brewed.

Just remember, several thousand years ago, Asian cultures, and the Middle East, were using Bronze chisels to shape the blocks for the Pyramids, and Horseman of antiquity had bits cast by the dozen, with fine art, in foundries run on wood charcoal. This was the modern science of the day. It should be a snap with modern technology, but its not. A lot of hidden rules.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

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Re: Information on metallurgy, casting and foundry work

Post by steamin10 » Mon Jun 17, 2013 4:00 pm

The question at hand is what to add back to the vessel for the next heat, as things may change.

First I have to define the question, in this case we are making something in brass. First off, brass happens to be one of the more dificult metals in the bronze (copper based) alloys by the nature of the metals invloved. It tends to oxidze and get gassy fairly easily, and this gas will come out as the metal solidifies, making either grainy or pourous castings, that are weak in strength and have a poor finish. Combining known pure stock is the best way to get an alloy, or buy certified bar(ingot)stock. These alloys are qualified by commercial numbers, and are standard in the industry, for strength, machinability and performing the job demanded of it in service.

Copper the base alloy is a high melting point metal, and the zinc that makes up the majority of the balance is quite a bit lower, so it is added after the copper is fully liquid, and temperature enough to completely consume the additions. Now the first rub. If you start with plumbing brass, and add machine turnings, what did you just make? What were the turnings? Were they oily? If you dont plunge the turnings below the surfac of the molten metal pool, they just burn to oxide the suraces in the furnace atmosphere, and paint and oils will contribute to the gassiness the metal will hold, unless we degass, with phosphorous or similar agents. At pouring temperature, the surface of the melt will cast a white smoke that is the zinc oxidizing off in air. This is more common when we convert scrap to a melt and have to build temperature to get to pouring level. so as soon as there is any liquidous metal it will start to cast the zinc smoke. Using a bit of flux we can cut down on the oxides, and by using smashed bottle glass floated on the top of the melt, we can virtually stop the smoke process while we get to temperature. It is important to gain experience to know waht the melt temperature is by sight, becasue we cant work the heat through the cover. We must hook the glass out, and make whatever degass, phos copper addition, by measured weight. A pellet or two of lead shot will help machinability if desired, but will kill the posibility of holding a shiny polish.

Virgin bar is easy, flux, melt pour. If you hold too long or stir in air, you are doing it wrong. Melt fast pour fast and quiet, and be accurate on your weight so as not to pig a lot of metal. Pig as little as possible.

The charge and all additions must be carefully weighed, to maintain proportions, for the alloy, or you go off in the woods someplace, never to know what you have for alloy. Ya, brass. Which one? Is it yellow like what you started with, or is it a cooked out dark orange? a color sample of the brasses can be a good comparitor for copper content by eye. Plumbing brass has a goldy tinge to it, and bearing brass can be from light yellow, to a deep reddish color, depending on alloy. A trick when you are bringing up temperature of questionable mix is to quickly sample the melt by taking an oz or so and pouring it into a hollow cup in a bucket underwater. You will get a nice clean button to look at for color, to see against your samples. You can buy zinc bar stock and have it handy for raising the content to fit your color, sawed into small blocks, or you can cheat and add some Diecast, which can be nearly 100% zinc, to zinc and aluminum combined. Ok the Aluminum doesnt belong in the brass. In General use, Aluminum bronzes can be stronger than cast bronze alone, and rival steel. So, for most purposes I can get away with a 10% addition of diecast to get back into the base metal copper range. Any one who has machined near pure copper will attest to poor finishes and terrible machining properties because it readily work hardens, Dark brass follow the same tendancies as the zinc is lowered.

Bottom line is always start with you pigged revert, no more than 25%, and preferably about 15% if you can match up your pours that well. The trick here is to get a consistant feed stock, be it brass compression fittings , plumbing brass, or other homogenous source, to eliminate the SWAG movements on making your home brew alloys. If you buy 50lb of sink faucets, except for the trashy plating, what is the diference from the ingots they poured these from? Consider it once pigged. (plumbing brass has some lead in it, to augment the automatic machining all these parts get. yes it shows up in the water. It gets rinsed out of the faucet in the first burst of water that changes the entire volume, so it winds up as inconsequential.)

If you can, always pour more metal in a larger pour in multiple molds. Small melts change rapidly in all manor of physics. So pour more molds while the metal is hot. That is an advantage toward synthetic oil sands, in that the mold cost is inconsequential. A 2lb pig is no big deal on 30lbs of melt. But 2lbs againt a 5 lb part, is going to creat a problem down the road with drift. Dont go there, and you wont get trapped. If you are doing some lost wax or plaster hard molds , pour them first, as the sand molds can be recreated easier if it fails on temperature.

I have cast small brass parts with a torch and crucibal, like a jeweler, but find bigger is better, so molding up 20 parts instead of 2, allows more metal stability, and more relaxing timing on my part.

When its all said and done, theres nothing left to say or do, I want to look at the day as an accomplishment, and my weird style of fun. A little planning lets everything fall in place, and the surprises are no longer a surprise because I have seen this before.

Always weigh your stock, and estimate you pour. weigh a simialr part if you need to. Always weigh your additions. Little food scales can help here. I have an electronic gram scale that I bought for $12, about 5 inches around. It weighs things like epoxy components to be mixed, lead shot for a melt, and similar weighty objects. Keep an alloy reference book handy, I cant remember diddly, so I am always checking back to reference some question or alloy, to keep at least close to the road when I have to guess at things. If you get a failed pour, it is just one way it did not work today, an adjustment or some venting, or thichness change can draw success from a failure, but more impotant, you sharpen your judgment. Learning is the most important part of the process, to ask the right questions, and develop an answer and process that works.

I am windy again, but this only scratches the surface of brass without being too comercially specific. You dont have to do anything, except what works for you.

I have three furnaces, each runs on house gas or propane. I use oil bonded sands now, after giving up on home green sand. I am tinkering with Waxes, and have glass plates and lamps for working the Brown casting waxes, and cookie squirter tubes for extrding shapes and parts to be joined together for complex assemblies. More art carving at this stage, but also vinyl materials for shooting wax masters. I have commmercial flasks about 15 x 24, down to fist sized aluminum split boxes , that are handy for the smaller parts without hoggin the sand. Most important is the pattern and core boxes for whatever you are in need of, and that entails a lot of fine wood working, that is completely a diferent subject.

I will be happy to answer any questions I can, or direct you to some of the books I have reference to, in these operations.

I have to go. TTFN
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

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RCW
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Re: Information on metallurgy, casting and foundry work

Post by RCW » Mon Jun 17, 2013 4:35 pm

Big Dave:

You're not windy. You're Steamin10. And I appreciate what you posted.

Have you done lost wax bronze castings? How did you make the wax patterns? What investment materials did you use? I could continue to ask questions, but I don't want to be windy, either.
--Bob

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Re: Information on metallurgy, casting and foundry work

Post by Pipescs » Mon Jun 17, 2013 7:49 pm

Thanks Dave.

Reading thru your response brings enlightenment and a bunch of new questions on how I am doing it.

Breaking down your comments into the issues for us learners

PART 1.
First off, brass happens to be one of the more difficult metals in the bronze (copper based) alloys by the nature of the metals involved. It tends to oxidize and get gassy fairly easily, and this gas will come out as the metal solidifies, making either grainy or porous castings, that are weak in strength and have a poor finish.
New Questions?.

1. Does using scrap materiel that has been melted before add to the gaseousness of the melt?

2. While I have never added turnings or machined chips, I have added large chunks. Does adding metal to the melt add gas?

3. Should Degassing be done before or after the Skimming or adding of such things as lead or copper phosphor?

On my part I am dealing with the gas issue with a "Brass Degasser" powder that I purchased from Budget Casting. It is a powder that I roll up like a paper cigarette and force down into the Crucible just after I reach the pouring heat. The creates quite a lot of popping in the hot metal. For an applicator I have a short pipe nipple welded to a steel rod. I also added a splash guard to the thing after getting burned a little. It is a paint can lid with a hole in it. I have a clamp around the rod to keep it from sliding too far down. So far it seems to offer me some protection. Needless to say it does not replace face shields and goggles.
DSC_0079.jpg

One of the issues I am having with my tool is that the tube will fill up with metal as I get in a hurry and put it down with out knocking it on the ground to clear the tube. So then it is full of solid brass the next time I wish to use it. I am thinking of going to a piece of two inch long by one inch angle iron welded so that the V is down. Then I would simply hold my Degasser paper tube in place with a rubber band to force it to the bottom of the crucible. (Is there a better way/)

I have yet to degas aluminum but bought some chlorine tablets to try after reading about them on another thread. As in the Degasser for the brass I will be using the TLAR (That looks about right) measurement system. For an A-8 I am using somewhere around a table spoon of powder

I am getting myself confused so I will stop and rethink my next questions
Charlie Pipes
USMC Retired

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2.5 Baldwin 2-4-2/2-4-4/0-4-4 Conversion (What ever)
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Re: Information on metallurgy, casting and foundry work

Post by redneckalbertan » Mon Jun 17, 2013 8:21 pm

steamin10 wrote:Using a bit of flux we can cut down on the oxides, and by using smashed bottle glass floated on the top of the melt, we can virtually stop the smoke process while we get to temperature.
Dave, I really enjoy reading your posts and the willingness to share information that you have shown.

A while back I was told a person was able to use kitty litter on top of a lead melt for bullets to keep gassing down and to insulate the melt and speed up the melting process.

I have never tried this, and my casting experience is very limited.

Why do you use broken glass to cover the melt?

Would something else work as well? Would kitty litter work?

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Re: Information on metallurgy, casting and foundry work

Post by Pipescs » Mon Jun 17, 2013 8:54 pm

You stole my question and welcome to the group. This is turning into one great thread already.
Why do you use broken glass to cover the melt?
And just as importantly.

1. What is the technique of using it?

2. When do you add the glass?

3. How much Glass to an A-8?

4. If you remove it prior to the pour, When do you remove it?
Charlie Pipes
USMC Retired

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2.5 Baldwin 2-4-2/2-4-4/0-4-4 Conversion (What ever)
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Re: Information on metallurgy, casting and foundry work

Post by redneckalbertan » Mon Jun 17, 2013 10:17 pm

Pipescs wrote:You stole my question and welcome to the group. This is turning into one great thread already.
Sorry for being quicker on the trigger! Lets continue on the list of questions.

5. How big are the pieces of broken bottle glass? Small pea sized? Large 1"ish size pieces?

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Re: Information on metallurgy, casting and foundry work

Post by steamin10 » Tue Jun 18, 2013 8:23 am

Ah, long day. So first things first. The question was about brass. Some of the issues are easier with Bronze. The tin that makes up the second portion of the alloy, is more stable, and imparts diferent qualities to the metal. So handling is diferent, and I believe easier to hit your marks for good parts. Bronze doesnt polish well, brass can be gleamingly beautiful. Aluminum, lead, silver, and pewter all have difernt traits, and must be treated accordingly. My best experience is Aluminum alloys. No matter.

Second, I am not a Guru to casting. I have done some, and only express some opinions that I believe. So, as always , take my litinay with that human grain of salt.

The interest seems to be in bottle glass as an oxide barrier. It is very effective at keeping Oxygen away from the melt process, and should be added as soon as you quit playing with the heat, or smashing the lumps and turnings into the growing puddle (with flux). Know that whatever brass is exposed to the furnace atmosphere will react with oxegen, and you will lose zinc and whatever else will burn in air and the copper base metal will oxidize, all are bad... Putting enough broken bottle glass, like beer bottle glass from last nights sports game, creates a barrier to this detrimental oxide process. It melts at bronzing temps and flows out to form a thin cap over the melt, and handily floats up, over the metal, to form a semisolid cover. The few tablespoon amounts should be thin, and just sized to cover. I keep an Icecream bucket around, and smash glass beer bottles of anybrand into smaller chunk, in the bottom of a plastic garbage can, on a steel plate saved for this sole purpose. When melted, This easily pulls up with a rod or poker with a small hook, to add final shot and degass right before the final skim and lip pouring. It needs to be thin, and fairly small pieces to melt fast, but to make a complete cover. Some will stick to the vessel, but that is of little concern, so long as we preserve the metal quality. It should be noted that lip pouring allows surface trash to be poured into the gate system. Various strainers, and mica filters remove any left over dross and floaters for the pour, ostensibly only allowing clean metal into the all important cavity. There are spouted vessels, that only allow metal from under the surface, to enter the cavity, something like a water pot that will hold ice back, and only pour the water. I find these contrivances, unnecesary, as small traps in the gating before the part work just as well. This button in the leader sprue, is designed to catch any errant sand washed out of the sprue channels, and the top of the button allows any dross to float up and be trapped, such that only fairly clean metal reaches the voids of the mold. Only venting, temp and feed rates then influence the cast.

As far as Kitty litter, sand, mica, exploded mica, and something else I cant remember, its the same idea, just doesnt work as well as a coheasive glass cover, that may stick a bit to the wall of the vessel. But there it stays, while we play. Sand can bond and make a glasslike plug, but if it doesnt, it may leave a lot of drossy pieces to get into you part. Nothing is more aggrevating, than having a stone, sand, or dross float into your part, making a blemish, or ruin for the use.

I have used the commercial lid to a bilge crucible, and they can stick, making gettin one off a hairy deal. If you have ever poured brass from a bilge crucible, you must know how terrifying the first experience is, as everything flexes and wobbles around, as you try to put the glowing metal into a dark hole.

The other question seems to be about how to innoculate a heat. I use a solid rod, with a dollar store spoon cup on it, and wrap whatever powder or chems in a flat packet of aluminum foil and swish it to the bottom of the melt with a twist. The foil melts, the twist adds motion to the metal, and I am done in just two twists of the wrist. I use a solid rod for a shank, as others have told me the gassing of the materials in the vessel will cause metal to perculate to the ceiling at times with a pipe or tube. The thought of molton brass rain, rather disturbs me, so I will not temp fate. The final skimming is just before you pour, after final additions, degasser, whatever it takes to get clean metal, and pour as fast as reasonable to fill the mold cavity. Dont dally, or interupt your pour, as you need a smooth, fast, clean rate of pour to get best results.

Gassy metal is a problem for metals proven to be oxide prone. Generally speaking, the gas cannot stay in a solid metal, so it freezes out when the metal gets solid. Adding blocks of metal is unlikely to change the disolved gasses, but it is recommended that cold additions be placed wtih tongs or similar stoneage miracles, to prevent excess stirring/splashing of the melt.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

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Re: Information on metallurgy, casting and foundry work

Post by Pipescs » Tue Jun 18, 2013 7:48 pm

Where is a good place to purchase metals such as zinc?
Charlie Pipes
USMC Retired

Current Projects:

2.5 Baldwin 2-4-2/2-4-4/0-4-4 Conversion (What ever)
Little Engines American Restoration
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Re: Information on metallurgy, casting and foundry work

Post by redneckalbertan » Tue Jun 18, 2013 9:32 pm

Pipescs wrote:Where is a good place to purchase metals such as zinc?
A lot of the new wheel weights up here are now zinc. (Lead is being phased out in favour of steel or zinc.) Do you know if they would they be a pure enough zinc to use for additions to brass melts? No good for making bullets so right now they are being tossed.

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Re: Information on metallurgy, casting and foundry work

Post by Pipescs » Tue Jun 18, 2013 9:47 pm

I will talk to the local repair shop that gives me the waste oil I burn in my furnace and my local tire store.

I also found that Zinc ingots are not that cheap on line. The lowest price I found was around 2.00 per pound for ingots on line. These were four pound ingots that would have to be sawed up. The wheel weights would make more sense.

http://www.rotometals.com/product-p/zin ... QgodWDwAsw
Charlie Pipes
USMC Retired

Current Projects:

2.5 Baldwin 2-4-2/2-4-4/0-4-4 Conversion (What ever)
Little Engines American Restoration
Bobber Caboose

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