Lost wax bronze melting time/temp

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Sandiapaul
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Location: Princeton, NJ

Lost wax bronze melting time/temp

Post by Sandiapaul » Mon Jun 01, 2020 7:39 am

Hi,

Did my first pour yesterday...total failure. Unless you count the button and the branches with no parts attached a success!

Two things happened, I couldn't get the vacuum to pull and the metal was not liquid enough.

This is my metal specs:

95% Copper (Cu)
4% Silicon (Si)
1% Manganese (Mn)

Melting range: 1580-1789°
Pouring range: 1850-2250° F.

I had the electric furnace set to 2000 initially, then upped it to 2050. I stirred with carbon rod and then poured but it solidified on the crucible lip at the end of the pour.

I had 10 oz of the casting grain in the crucible and it sat in the furnace for about 25 mins.

How do you determine the correct time for the melt?

Thanks for any help!

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Rick
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Location: Stone Mountain, Ga.

Re: Lost wax bronze melting time/temp

Post by Rick » Mon Jun 01, 2020 10:38 am

Do you have a way to measure the temp of the melt? This is the best way to know when to pour. I do not have anyway to do this yet, I just do it by by the highly sophisticated method of "that seems about right". I have a gas furnace so temp control isn't as good as your electric and wouldn't know how to compare melt times. Most likely you will have to set you temp higher, it may be due to where the thermocouple is in your furnace, it may be reading higher that what your crucible is seeing if the thermocouple is near the heating elements.
What was you Investment/mold temp when you poured?
I have had ok results without vacuum on larger parts, not because I didn't use vacuum but because I couldn't pull vacuum (bad seal)
Rick

“We make a living by what we get, but we make a life by what we give." Sir Winston Leonard Spencer Churchill (1874-1965)
"Peace is that brief glorious moment in history when everybody stands around reloading". Unknown
Murphy's Law: " If it can go wrong it will"
O-Tool's Corollary: "Murphy was entirely too optimistic"

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Sandiapaul
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Location: Princeton, NJ

Re: Lost wax bronze melting time/temp

Post by Sandiapaul » Mon Jun 01, 2020 11:22 am

Rick,

Thanks for the reply. I forgot to mention flask temp, it was 900F. Is that about right? I see a lot of different info on what temp the flask should be at. I should mention I followed the burnout exactly as the directions indicated(It took all day!) I have a digital infrared reader, I'm not sure it goes that high. Also have a good omega reader but need to buy thermocouples for it. These were little parts...like 1.5" scale cut levers and such.

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Rick
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Location: Stone Mountain, Ga.

Re: Lost wax bronze melting time/temp

Post by Rick » Mon Jun 01, 2020 12:00 pm

Yes 900F is good for the flask. Seems like you just need to turn the temp up a bit and get your vacuum working. I would use your furnace temp reading as a reference but not rely on it to be what the exact melt temp is. Did you remove the slag and other crap that rises to the top of the melt before you poured? It can block your runner system and block flow into small areas. Removing this stuff is when I get a feel for how fluid the melt is. Also did you use any flux?

Yes if you follow the burnout that the investment manufacture wants you to use it is a long process. I have a ceramic kiln that I added a programmable temp controller to that i use for burnout. Turn it on and let it go for many hours:)
Rick

“We make a living by what we get, but we make a life by what we give." Sir Winston Leonard Spencer Churchill (1874-1965)
"Peace is that brief glorious moment in history when everybody stands around reloading". Unknown
Murphy's Law: " If it can go wrong it will"
O-Tool's Corollary: "Murphy was entirely too optimistic"

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Sandiapaul
Posts: 518
Joined: Wed Jan 07, 2004 8:04 am
Location: Princeton, NJ

Re: Lost wax bronze melting time/temp

Post by Sandiapaul » Mon Jun 01, 2020 1:19 pm

Yes I stirred with a carbon rod, but nothing actually came out with it. I bought casting grain so chalked it up to better quality metal? And, ahem...yeah the flux. I noticed the jar of flux on the bench right after I did the pour! So no on that. How much should you add?

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