gadget

first furnace, first melt

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i have a 30 hour osha card and a lot of the stuff i had to learn made very good sense. even if it seemed over the top ,its better to assume the worst than to not. i guess what i meant by my statement wasnt that silica fibers werent important, but the immediate threat to me was the lack of awareness of surroundings, and of the proper PPE and also piping safety. that was all i meant, im very sorry i didnt say that well, and in no way was i downplaying the threat of silicosis or of silica fibers. its my biggest fear persoanlly, since i work around silica in at least five forms daily. from fumed silica, silica flour, caobo-sil, colloidal silica, to crushed glass, lead crystal powder, etc. i deal with it on a daily basis ten to twelve hours a day. therefore its way more of a risk for someone who is working in that capacity, than it is for someone who is having occasional exposure, and since its cumulative it seems to make sense that it is dealt with in order of threat, but i realize now that i am in the minority in the sense that not everyone posting here is that involved daily. i stand corrected.

 

looking at what others have posted they are suggesting that check valves arent important, this is incorrect. the purpose of a check valve is two fold, it allows the gas to flow in one direction only, and it stops combustion from entering a flammable gas ,such as acetylene for example. with propane set ups like this the real concern isnt the tank blowing up, its teh gas line being melted, stepped on and cut, or wearing out from time becoming brittle etc. so when i see an uncovered rubber hose carrying 5 psi of LP i get nervous XXXXX just one drop of molten aluminum can weaken it to bursting temps, or even radiant heat formt eh body of the furnace. now thats all well and good if youre in a foundry with a sand floor and are wearing safety gear, but wearing shorts in a backyard next to a wood pile and im going to focus on that as the most likely thing to go wrong here. thats more what im saying. flashbacks and checkvalves are never installed on propane lines for gas grills, stoves etc. thats becasue they have flame safety for in home use and for camping gear its assumed that youre outdoors where gas has no chance to build up uncombusted like it woudl inside. I use fluid power valves that are normally closed for my furnace lines and i at least cover the hoses (if im not hard plumbed) with a flame resistant sleeve like i use on my TIG lines.

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2 hours ago, gwynlaredogranger said:

it seems to make sense that it is

The watchwords of the opinion of 30hr, text book experts. 

I suppose you know what OSHA says the safe exposure level to radiation is? ZERO, living underground isn't safe.  

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are you saying that i'm completely wrong in my suggestions? or are you saying that if something seems to make sense, that it doesnt actually make sense? or are you saying that because you dont like me that youre trying to find something to disagree with me about? or are you totally discounting my experiences of the past because i have osha certification ? im not sure i follow what youre posting about, can you clarify? also id like to get back on topic since the person who posted this thread is looking for good input on their set up and melts, not listening to two old guys yammer back and forth ;)

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Please realign your anvils to north and get back on topic.

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On 10/11/2019 at 5:45 PM, BIGGUNDOCTOR said:

The easiest way I spot magnesium is the color. It oxidizes quickly and turns a gray coloration.

That's very cool. I look forward to working with it. Thank you.

On 10/12/2019 at 10:22 AM, Phil K. said:

All this about Silicosis and unnecessary flash arrestors and nothing about his PPE? He has some good PPE but it still casting with a T-shirt, short pants and canvas shoes. He should have at least blue jeans and leather shoes, along with some type of arm covering. 

please see my earlier reply to biggundoctor...I agree with you...

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Just to be clear folks,

I am a 55 year old senior engineer that works for a Defence Contractor.

I have had a career in the Coast Guard as a Fire Control Technician (radar and weapon systems).

I am a firm believer of common sense safety and I have been reading this site since April because not all sense is common.

If you give me an opinion or suggestion, regardless of your resume, you should expect me to ask why.

I appreciate these discussion because you never know when someone is going to say something that saves your life.

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With your face shield on you look much younger in the pics you posted. I never would have guessed your age. B)

Pnut

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Sorry Gadget, I did miss that. I have some pictures of my son trying to help me. I usually had to get on him about his shoes. :D

 

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On 10/11/2019 at 10:33 AM, gwynlaredogranger said:

buy ingot for your aluminum use 356 alcoa its good stuff, you dont need any fluxes or degassing with it either , at least not yet for a backyard rig. good luck and always wear your safety gear.

whole other game than cans.

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It's all good.

I did buy 99.9% copper ingots but wanted to feel righteously green by recycling aluminum.

My rudimentary knowledge suggests it is harder to find and recycle pure copper to recycle than aluminum.

I imagine if I did the calculations I would find that the propane etc required to reduce cans was less efficient than buying it.

Phil - Mine's is a buckeye grad student...small world...

pnut - ;) don't tell the wife, she'll make me wear one all the time.

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gadget-

copper is a challenge to melt, requires a decent temp of around  2000º f -2100º . that gets it hot enough to flow but not too hot as to cause porosity and other defects. its a lot trickier to melt than bronzes that is for sure, but you will love the way it pours out, it will fill in a similar way to aluminum, but its heavier and has better head pressure when poured. be sure to not disturb the melt surface and to skim all slag thoroughly. it is MUCH hotter than aluminum when you are pouring so you wont even be able to stand near the crucible without trousers on. i prefer pouring Al because its lighter and lower temp, and still fills really well. but i mostly pour non ferrous alloys.

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Cool, I have aluminum leggings to go over my jeans and under the apron. Boots, a welding jacket, gloves and facemask will finish off my outfit.

I plan on casting Aluminum Bronze using a lost wax process. I'll post photos of the flasks that I have prepped. I still need to burn them out

I have a fair bit of experience of small castings (jewelry) in silver and gold. Which is the process I plan on using, sand casting next year.

I am glad it is finally cooling off in New England. Wearing all this xxxx xx xxxx in August.

The leaves are in peak color.

 

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investment casting, cool, i have a shell department. they sell that stuff that doesnt need to be in a slurry tank nowadays. how will you be dewaxing? i have burnout oven that i can reclaim my waxes with. Aluminum bronze is tough to weld and super hard, harder than some steels even. great for wear plates. i have large opinions about dewaxing, it can get sketchy. plus the shell needs to be cured a certain way...aw man so much to cover! yeah the peeping is great out here too, ive come to feel fine wearing tons of safety gear all day in the heat, that way when you take it off ,it actually gets cooler, even if its 95 out, it feels cool ,compared hahah!

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OK, different valves: flow check valves and backflash/arrestor valves.  Propane does profit from a flow check valve as long as it doesn't prevent the burner from working---when they first started using flowcheck valves in the smaller propane tanks they had a tendency to lock up for devices that used high flow rates like burners may.  It helped to open the valve slowly too so the first fill all the low pressure area didn't lock the valve.  (These issues were part of why commercial tanks didn't require the flowcheck valve modification while consumer tanks did.)  Newer versions seem to be doing better in my experience.

I've been around an incident where someone unhooked a propane tank from a cooking surface WITHOUT CHECKING THAT THE TANK WAS TURNED OFF.  Vented the tank contents in a public area.  Definite brown pants situation.  Armouring your propane line can be a good thing too.

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yeah, a friend of mine is a retired Marine cook that collects a disability pension because an idiot blew the doors off the cooking tent he was working in. The scaring goes right up to the point where his cotton t-shirt sleeve starts interestingly enough. Like I said before, I take safety seriously. If I was working with someone else or couldn't control access to my work area, I would order it today. I'll probably order an armored line and a flow check valve in the near future though... not because I fear a failure, mostly because I like playing with gadgets

I use an electric kiln with a drain for jewelry burnouts (pretty small flasks) but I think I'll try something more old school for the flasks I have now (much bigger). I'll post the pictures regardless of my success. Hopefully I'll have some time this coming weekend.

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If I'm not mistaken "flow check valves" are internal to smaller propane tanks to prevent blow out leaks like a cut hose.  While they can be inconvenient they aren't onerous to work around feeding a forge burner or four. If you open the draw gradually they aren't a problem, I've run my 4 burner shop forge from a 20lb. tank with a flow check valve, without problem. Just not for very long before it started to freeze up.

I've been doing inherently dangerous things since I can remember I just do them carefully. I was metal spinning when I was 10 or 11 I'm a firm believer in safety and am a frequent clarion on IFI. Warnings and precautions can be taken too far though they desensitize the people who need a warning. Unfortunately the boy's been crying wolf so long they ignore him and warnings. 

A couple casters I know dewax with steam. No, they don't use a steam cleaner but they introduce water into the burnout kiln. Neither of them know each other, one lives here in the Mat Su Valley, the other on the east coast but there is a lot of similarity in their methods. About the only thing I remember about one method was to soak the mold before putting it in the kiln. I think another method was to put a pan of water in the kiln but I'm really fuzzy on that one. 

Frosty The Lucky. 

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yeah i wouldnt do any of that steam stuff ,especially without an autoclave, and even that is usually in large process ceramic shell facilities where youre dewaxing 150 lbs or more of wax. most foundries stopped doing that since the breakage is much higher with uncured shells or green investment mixture. jewelers usually use a small fired kiln. if your investment mixture is silica flour and plaster it stands a better chance, but still the steam breaks down ceramic shell before it's cured (it gets vitreous at 1000º). you want a fast hot kiln that can get to 1000º in under ten minutes if possible. if youre using investment mixture then you want to get through the 212º range long enough to drive out steam but not so long that the plaster calcifies easier. i usually cook investment mixture for a few hours, whereas with shell, they can burn in under a half hour...

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not going to use steam.

I share your enthusiasm for living closer to the edge.

 

My electric kiln burn out schedule for jewelry is usually:
300F for 2 hours

700F for 2 hours

1350F for 4 hours

900F until cast

remove flask from the kiln and place on the vacuum table

molten silver or gold in a ceramic crucible is kept under the torch to keep O2 away, right up until it is poured into the flask.

as soon as the metal fades from cherry red and solidifies (about a minute) drop the flask into a metal bucket full of water

the investment dissolves out of the flask like alka seltzer

retrieve casting from warm water after a few minutes cooling

The casting I plan to use the Aluminum Bronze for has a lot more wax and a lot less detail....so I'll use build a fire pit outside for the burn out...

With a little forced air from a shop vac and some lump charcoal, I should be able to hit the right temps.

I've also got to order some flux to protect the heel since I'm not using a torch to keep H and O2 out of the melt.

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We used an autoclave at the foundry I worked at. They said they had less breakage with the autoclave due to the pressurized chamber. When they tried just heating the wax it expanded and cracked the shells. The autoclave didn't expand the wax like the oven did. We were pouring 25kg of nickel based , alternative gold, and chrome cobalt alloy ingots into two molds for the dental industry. We poured at 1450 and 3200 for the chrome cobalt. We burned out at 1600F and 2100F. We ran an old induction furnace that was probably out of the 60's.

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Most wax patterns need to be hollow. Also the runners and gates are hollow core. Nobody can make a statement about casting that applies to all castings. Most foundries that are burning more than 150 pounds of wax at a time need to use an autoclave . That I’m no way means that you should always use an autoclave. Plus most people aren’t going to have a device like that. The best way to burnout shells is the right way for each shell/pattern. If you’re casting the same part over and over and over you tailor the burn to that . If you’re burning a large solid piece , then you need an entirely different approach. There’s no one size fits all really. Plus no matter what shells break from time to time, doesn’t mean it’s from the heat. The manufacturer recommends dewax at 1000 degrees and for anything above 150 lbs you’ll need a lot more gas and an afterburner ( I built a dewax that is 8ft x8ft x 5 ft for my shop and it has an afterburner and internal plumbing that is sealed from air so the wax doesn’t flame up) . It’s piped into a rubber mold with ingots so I can remelt. When you use an autoclave you’ve also got to reclaim your wax and separate the water back out in another melt operation. I could on and on but you get the idea . The thing about casting that’s tough is knowing when to do what for each individual shape, they all have different rules but at the end of the day they all are the same rules. 

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The cool thing about jewelry casting is that most if not all waxes are solid and not large. Not to say that jewelers haven’t cast big pieces , but not usually. I dig the set up for your burn out schedule , I’m sure you have that dialed in. When I started casting I first learned large investments . These would be 2-5 ft tall range moulds made from ludo, pottery plaster, #200 mesh silica flour. After setting up we would load a hand built soft brick kiln around them and face it with hard brick, rig up a burner and camp out for a three day burn. Taking them out of course was also surgical because they’re friable. When the moulds get big the flasks get heavy , be sure to seal the bottom to its coddle board.We used hardware cloth around the interior of the flask so that it was about a half inch beneath the exterior of the mould. That protects the galvanized from direct flame exposure ,also pre burn any metal reinforcements so they don’t create vapor that will hurt the moulds.When the scale increases so does the amount of weight the investment has to bear so structure becomes important . Careful for leaks while pouring ( we bedded the moulds under loose sand when pouring) take care not to get sand In the cup;) 

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They just tossed the wax from the autoclave. We would fill up a 55 gallon poly drum and at the end of the day it went into the dumpster. I remember the wax was red for the mold, and green in the cup. They were making so much profit they did not worry about wax costs.  The non precious gold alternative cost them $2.80 a package to make and they sold it for $28. Those were continuous cast then stamped with a logo, polished, and packaged. Yes, ingots were polished before shipping. We had dental labs complain if they were not polished enough, or the logo was not fully cast in..... and people wonder why dental work is expensive.

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I don't plan on casting anything much more than stuff that will fit in a 5 in diameter flask. That is the largest I feel comfortable handling and will fit properly on the vacuum table. Also, I use 100% investment plaster. Kerr's Satin 20 is what I have right now. For my smaller pieces it is much easier to clean out.

I saw a really cool CNC machine making crowns at my last dental visit. The processes they use have really evolved. No more developing film, just a buzz and the x-ray appears on a PC and few minutes with a CAD app and then send it to the CNC machine.

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