Metal Casting Zone

Hi everyone


I am about to do another lost wax brass casting run for my model parts. I have read in one of my text books that if a melting pot has graphite crucibles no flux is required when melting the brass. Would like any feedback on this aspect of casting.
Johncast.

I had never heard that, I wonder if that's why I have trouble with Brass. It doesn't want to pour well, seems very thick. My crucible is homemade, solid graphite. Maybe I'll try a clay crucible next time.
I use a little borax for flux and actually cover the melt with powdered graphite. I've heard that using charcoal is a better cover, it uses more oxygen.

I melt aluminum in a steel crucible, I use pure heat to melt. It seems to take a HELL of a lot of heat to melt the aluminum and when it does melt, it does not pour well. Am I doing it wrong?

I use no flux with my brass and my crucible is 316 ss, I have no problems pouring brass or bronze without flux. But i do pickle my brass in sulfuric acid before I melt it so it is very clean.

Yes Aonemarine this is the area I think i need to foscus in on ,I mentioned this problem before 7 mts ago after my last casting of brass and suggestions were made just as you are saying, no flux but make sure all the brass that is to be melted is very clean.
I have cut up all the brass I require for this casting run and have boiled it in pickel acid solution and has cleaned up ok. I intend doing this again a few hours before I use it for casting.
I was thinking about this oxidation of the brass after I have boiled it in the acid and flushed it through clean water. Would there be an advantage to leave the brass completly covered with clean water in a container to reduce the oxidation on the clean surface of the brass. Removing the brass ,drying it, within a few minites of it being melted. Thanks for your help JOHNCAST

I dont know about storeing it in water, just a quick acid dip before casting should be fine.

Johncast here

So I have done my casting of the model parts, will get some pics up soon.
Another total disaster as far as colour.
Did get very good castings as far as detail and everything cast with good detail. Investment was a very good chalky colour when the flasks were taken out of the furnace after a 12 hr burnout,A better colour in somepart of the second castings as i dropped the flask temp to 580 or so but the fire scale or what ever it is is all through the castings and wouldn't clean off at all . The pour temp of the brass I used was 1005oC and flask temp on the first flask was 620oC. Didn't add any flux to either of these castings, to see if it was the flux that was the problem last time . Flux is not the problem. I feel it is the casting flask temp it much too high for brass . How would we go with a flask temp of say 550oc or 500oC. Any help would be much appreceiated

I see a reddish copper in the alloy,is this too much heat in the flask while the metal is solidifying,do the alloys seperate.????????

A picture of the two casting from the two different trees the one on the right is the casting cast at 580oc why is the brass colour not all over? why the red stain through the alloy surface. ?? Would this not happen if the flask temp was 400 oC or 500oC.?

Johncast, What are you useing for water when you make up your investment?

Investment is mixed with precise measurement of tap water which is at 22oC to 24oC in temp. Should distilled water be used??? In having read a few books and scaned the internet on some topics I still believe the casting temp of the flask is my problem, followed by the alloy I am using.

Intend to do another test run again this week to try all again. made some more waxes yesterday. JOHNCAST