Metal Casting Zone

Here is a first attempt to cast a sprue former for my spin casting moulds made the pattern out of timber then cast metal at around 840oC from alluminium Scrap car parts. Filled the cavity ok but needed a lot of clean up and had a little pitting in some parts.
Metal may of been a little too cool. Or I have to refine my sand a little more.
Any ideas????

It actually looks pretty good, what are your concerns with it? I does look like it may have been a bit cool, hard to say. Where would you like to improve it?

Hi

Thanks for your high approvial Aone, I was very surprised with it when I broke open the mould to see the result. I had to fill several pit holes in many areas on both sides once I sandered and fine finished it. I expected a better surface maybe. I haven't mixed my sand with any kitty litter yet so expect a better finish on my next project of brass house numbers.. we will see. I first have to fix my lost wax casting woes first.

hi john pretty good. by the looks of things..... may i suggest you "pig" your metal as i can see some impurities. plus i think your sand was just a little too damp. a bit dryer and you could have rammed a bit harder. pits are usually either impurities in the metal or loose sand has entered the cavity. i always "blowout" my moulds by either just blowing them or use a blowgun and compressor. another point... you said the pattern was wood??? did you paint it??? if you didnt its advised to do so ...this makes a cleaner mould and hense better finish.

H i XL
Thanks for the advice, To pig means to melt metal and pour into an ingot???By doing this impurities are removed?
I am use to brass casting and some have said not to pig brass,so I hadn't thought of doing this to the alluminium before casting. Had to spend a lot of time to cut up the pieces of metal to fit my melting pot. Then I cleaned all of them in a ultrasonic before melting. Yes my timber master was painted before use. sandered down smooth before and after painting. Thank again for the help

ps Have just added some kitty litter to the mix of sand crushed up and mixed 10 sand to 1 litter should I get a better surface on future castings????and is 840oc right for aluminium alloy castings???

were pit holes of equal quanity on both sides or just one?
was the aluminum you melted from an extruded shape?
the recommended clay content for aluminum can be as high as 15-20%

Hi A One
Some pit holes on both sides just small
The Aluminium was off a car part some engine componet and I gess die cast Al
not extruded Al. Maybe I try to do this part again and compare results. Still I was pretty pleased I got what I did ,for my first try.

those little pits can be a bugger sometimes, try drying your mold in the sun a few hours before you pour (helped me out alot) and maybe a deeper sprue to get some more head pressure. If that doesnt work try the petrobond sand (very fine surface finish can be obtained) Yes more clay does give a finr finish but also can increase moisture.

pigging your scrap helps clean the metal. aluminium is "self cleaning" in the molten state and one becomes very skilled with skimming.some of my castings have been melted several times over and i get my finest castings from this "scrap"