Hi I just melted some scrap brass, only my 3rd melt so far with the electric furnace. I notices in the air small whitish particals floating around and in the crucible white cob web / candy floss which i scraped out and it was like fluff cotton wool, the ingot i poured looks very grubby and not as nice as other pours. Did i over cook it and what i saw was the zink burning off??
+1. It's common for the zinc to come out of solution and additions are sometimes required. As David said, don't breath it which is good advice for just about everything we use. It will cause "metal fever" and cause flu like symptoms. It's very well known amongst brass and zinc casters. Best, Kelly
When you say additions do you mean if this happens again i should add zinc powder??i can get that off ebay but its quite expensive so is it correct? I just remelted the ingot and added a whole load more brass for a large ingot and it seems to have gone well at a lower temp. i will polish and finish tomorrow. its around 2kg. my furnace is in my shed but it is well ventilated and i use a £50 breathing mask,
HT1 casts a lot of brass and will probably weigh in on what's usual and customary for additions, but if you ad zinc, I don't think you need to buy the high grade dust, just scrap like marine anodes should be good enough. I was just thinking when you commented about it's appearance I was thinking cast copper oxidizes, and low zinc. Best, Kelly
Right, but if i buy scrap zinc, is it pure, alot on ebay is zinc galvanised flower buckets. Is that worth it??
A very thick galvanized coating is at most few thousandth of an inch thick so if you're looking for zinc, galvanized stuff is a waste of time and money.
When I say scrap zinc, I'm not talking about zinc plated on steel. Zinc marine anodes are relatively pure zinc and usually a kilo or so. You can buy them new but the take offs are recycled and very inexpensive. Search eBay for zinc ingot, marine ingot, zinc anode and you'll see. Or if you're near a small marina that does boat work for ocean going marine pleasure craft, stop in and ask for a couple. Best, Kelly
You need to add Back what you lose ( I know that is obvious ) What I dont know is how much you loose in an electric furnace, So ask your self this question: how long did you hold the metal over 1950°F or 1065 C ??? should not be very long unless your furnace sucks, your pouring temp top is 1100C the standard is to add back 1% I run an A16 so 23Kg of Brass at the brim (For the sake of all that is holy never fill a crucible more then 2/3 full) I need to add about half a pound of make up zinc ( That is actually too much, but I think I loose more zinc because a fuel fired furnace agitated the Metal alot , and that adds to the melt loss) if you are running a Similiar sized crucible as I do (A16), I would recommend adding a roll of modern(1983 or newer ) U.S. pennies to the heat, just before pouring , I use Zinc anodes (Be careful you dont get aluminum or magnesium anodes ) but you may not have access to them at a reasonable price, if you are not too worried about your alloy, you can use diecast Zinc ( Do the vinager test, it will be 90-96% zinc ) the zinc has to be plunged to the bottom of the heat I use a 3inch length of pipe welded perpendicularly to the end of a piece of 1/4 inch rebar put your make up zinc into the piece of 3 inch pipe. preheat it this must be dry before it goes in the furnace or you will get a heavy boil or even an EXPLOSION , if you are woried about the zinc falling out of the pipe wrap it with some aluminum foil, if all that is a little scary , you can triple the amount and add it at the bottom of the heat before you start melting, this of course will increase the flare, but will leave behind the makeup zinc you need BTW this all applies to Yellow brass, if you got a zinc flare, unless you WAY overheated the metal that is what you where working with, by the time you get a zinc flare from a red brass of bronze you have way over heated it, several hundred degrees Finally if you are just melting scrap, and not trying to hit any particular alloy , and your only concern is color of the metal , dont worry about it , anything from 20-40% zinc will be yellow , the addition of a little aluminum 4% also helps keep you yellow, but you cannot use any Phosper-copper once you add aluminum of you will get gas issues Most scra pmade in india brass art pieces are 40% zinc, brass shell casings are 30%, c360 Free machining brass is 35% zinc But has Lead so be careful Most brass scrap will have lead so just be ware V/r HT1
You can also cut a small block of hardwood board to float on the top of the brass in the crucible, as it burns the CO2 keeps the air away and the carbon has a slight fluxing effect. It just has to be big enough not obstruct the pouring metal, say 3" square. This helps if you have large thin castings and the metal had to be hot or the crucible is smaller and cools fast.
I asked about this elsewhere from a foundry man with way more experience than I... one of you college educated fellows will probably have to explain this to me. Because it goes over my head. Especially in the case of yellow brass that requires no degassing Yet another degassing method with the use of natural properties of Cellulose that is going through a Process of Hydrolysis , as you know with aluminum the cellulose in wood still is holding on to oxygen and in the process of breaking down the cell walls as in hi temp or fire and when the cell walls get inveloped it will release the imbibed oxygen & in that process of Hydrolysis as Its in motion draws to through & mixes in the process of oxygen being put through a Crude form of a photosynthetically ( as in what makes a plant turn green in sunlight and I doing so gives off Oxygen this process reacting to the release of oxygen in every stage of life wood has until it's demise in fire when it releases it's final burst of energy releasing oxygen draws gasses already being released and flowing up to the least resistance out of the crucible The hardwood is used instead of the pine used in aluminum , you have noticed how fast gas escapes when the process of release of oxygen in the saw dust draws gasses out now with brasses gases released or are still in the Development while molten your block of hardwood on top of the melt but not on slag As the molten metal is heading out the crucible lip going past the hardwood the gasses are drawn to the wood side of the molten metal and what does not get completely involved in the Hydrolysis's total process this remaining gas has been in. Movement That puts remaining gas & gases still being formed while running down the gating system has been moved or is in movement vertical in the direction of the Cope side of the metal flow which escapes more readily continues to & through the vented cope of the mold, & you have a question On why your block of hardwood doesn't disinagrate upon contact , well your not going to be tossing it in, or letting it get in any way submerged . it is to be placed on the surface tention with it slagged off now your not going to get the Hang all at once you'll have to play with the size of your crucible and the wood block size & length to have enough Clarence for the molten passing under without restrictions that would slow the action of the free flowout of the crucible . And your still wondering why there would be a best way to place your wood it will start the process of turning the piece of wood into a piece of Masquite the masquite burns slower it has a slower release action of oxygen The wood as in fire wood burns on its own because it has oxygen in it's cells and The constant cell wall degradation releases the oxygen that wood fibers (Cell walls) need to burn that is why when you add wind to fire it enhazes and goes wilde wood that is burning off its self. Or NOT ! V/r HT1
Wow!, I just thought it helped keep the air off the brass or bronze when the wood burnt and sort of acted as a dam for the oxides on the surface of the crucible. Pine would have a fair bit of rosins that are used as fluxes for stuff like solders, aluminium may be too hot for rosin to flux it.
When the molten brass is hotter than the boiling point of zinc (906 C) which it is, a steam explosion might occur. And the steam is not water vapor, but zinc vapor. Not a real explosion, but droplets of brass might shoot away quickly due to the flash evaporation.
explosion or not here is the results of not preheating Zinc or anything before it goes into a crucible with molten metal in it here is what the hand inside that glove looks like, I'm good now, but the ER was so sure I was going to loose a finger or two they sent me 60 miles down the road to the nearest burn ward Preheat everything going in your furnace, your instinct will be to go easy on Zinc (so it doesnot melt early) Dont get it HOT before it goes in , and wear your PPE V/r HT1
So is the vapor pressure caused by exceeding the boiling point of alloying metals what causes them to come out of solution and loss at the surface from the melt? Seems like that could affect a lot of alloys. Seems like that is written more in the style of an academic than a practicing foundry man. Hydrolysis is just how something breaks down when exposed to water, and that source of water is wood, but all he talks about is the reaction with oxygen, presumably liberated from the water....maybe. I'm going to go out on a limb here and say the reason you don't commonly see this practiced is because it doesn't work, at least well, or maybe in some instances better than absolutely nothing depending upon what metal, but in most cases I suspect all you would accomplish is turning the wood to carbon ash. I mean all this time, industry and foundry men have worked to condition their melts and that whole time, all they needed to do is chuck some wood on the surface of their melt........my BS flag has been risen. Charcoal as an O2 barrier on the melt or "getter" like heat treating steel in a metal pouch is more common, but charcoal aint wet wood! For amusement, ask wiki....LoL How to Melt Brass (with Pictures) - wikiHow Best, Kelly
I had shot some video of some bronze condenser end cap castings. The bronze gets skimmed, then fluxed (8:10), then a coagulant is used to form a sticky lump easily skimmed off the bronze, only when ready to pour, does the hard wood get thrown on top of the crucible. The bronze is hot enough that the zinc is burning with a blue-white flame because we had a smaller crucible than normally used, we were getting casting flow defects in the larger castings so it had to be hot to allow for rapid cooling. I'm holding the small skimmer in the video and you can see Peter admonish me (13:20) to let the wood stay near the pouring spout not push it away (my job was to stop the wood from falling out). So from what I can see from re-watching the footage, the wood is simply a physical barrier for surface contaminants going down the mould after the metal is fluxed and skimmed. Pete is pushing the dross away (12:50) from the crucible spout before throwing the wood on top.
I think Billy mayhave misspoken if you read the pyrolysis of wood ( Do the google search) , what he is saying makes more sense , But again yellow brass requires no degassing , no fluxing so I really think we are getting off target ! But it's still darn interesting and I love hearing all you college edjumicated people Thank you V/r HT1
