Crucibles

[Marine Man]

Hi All,
I have been lurking in the backround for a while and I must say this is a really great site - well done!

My brass scrap box is growing rather full and needs to be smelted down and recast. A couple of years ago I did the job using an old clay pot as a crucible which worked for a few times before finally cracking. I cast round stock using the inner bore of large diesel engine gudgeon pins as molds. I must say it worked a treat and the cast stock was some of the best I have ever machined! (must have had just the right mix of everything). I was wondering if there are any suggestions for more durable crucibles, short of expensive carbon ones?

Machining-wise I have just finished juniors oscilating steam engine, and am now working on a Stuart D10 kit of castings.

Look forward to hearing about crucibles. Thanks guys.

 

[Bluechip]

Welded from steel ?? No, I don't do casting, just know of this site ... so don't ask ..

http://backyardmetalcasting.com/crucibles.html

Dave BC

 

[abby]

If you are serious about casting buy a couple of plumbago crucibles, At around £25 for an A8 the cost is small and treated with care they will last for years casting brass.
Don't use flux in your melt as this will eat the crucible away in no time.
Steel is useless and can fail with dangerous consequences.

 

[doubleboost]

Hi
Steel crucibles can be used ok for aluminium
Ceramic is best for brass & bronze you also get better heat transfer in to the metal
This link should take you to how i make steel crucibles
http://www.metalworkingfun.com/showthread.php?tid=153

http://www.metalworkingfun.com/showthread.php?tid=581

I hope i am ok posting links
I will be posting alot more on hear now that certain people have gone to pastures new
John

 

[abby]

When replying to a question I try to give relevant , safe , advice always based on my own experience and not on what I have read somewhere.
The question was "what is the best crucible for melting brass" not aluminium.
Even though it is common to melt aluminium in a steel pot I would not recommend it unless a suitable internal wash has been applied.
Steel dissolves readily in molten aluminium , not only contaminating the melt but gradually weakening the container.
You would wear the correct protective clothing for any hazardous operation , why skimp on the tools ?

 

[doubleboost]

I totally agree with you ceramic crucibles are the way to go
I needed a big crucible for one pour (i could not get a bigger ceramic one in my furnace)
All i was trying to show was how to make a steel crucible as safe as possible (have you seen what some people use)
John

 

[oilmac]

I worked in the foundry trade & i can concur with Abby, that steel crucibles are an absolute No No for melting brass &bronze in, & i would go the length of saying the same goes for melting aluminium, In the case of brass &bronzes, taking aside the melt contamination, with the high temperatures one is melting at, & by and large the construction of your crucible ( it is more than likely constructed with a welded base,) One has a recipe for a serious accident, Molten metal is a very unforgiving substance, It does not take a lot of it to do serious damage to a human

I feel for what it is worth for peace of mind, the cost & use of a clay graphite crucible is very much worth considering. Saying that look after your clay/graphite crucible Keep them in a dry environment between use, Dampness & water is the mortal enemy of crucibles

Remember our hobbies are an area of our lives for relaxation and enjoyment, not to be marred by cutting corners

 

[Tin Falcon]

can you yes recommended well my gingerly book that tells one how to make them has disclaimers recommending you buy them.
so yes you can make them but it depends on your skill and knowledge of doing so . and therefore no guarantee.
tin

 

[rhitee93]

Smaller crucibles are really pretty inexpensive, and readily available. I make just about everything myself, but plan to buy a crucible when I finally get around to casting some parts.

 

[Atzerath]

Where could I buy a good crucible online In Europe??
I f*ck*d up 2 steel pots today when trying to melt aluminium....
I sure did smelt it but I'm stuck with an aluminium blob mixed with coal...

 

[Artie]

Hi all, due mainly to geographics, we often have to make, rather than buy stuff, same comes to metal stock and crucibles.

Ive made many crucibles over the years, all from steel and I can say that they work ok for aluminium, I understand the comments made here and accept them. When casting anything, care is number 1 priority.

With regards to casting brass using steel crucibles, I can say that they DO NOT last very long at all. Its for this reason that I have bought several (very expensive when freight is included) ceramic graphite crucibles.

They really are the preferred item if you can get your hands on the in the required sizes. I need a larger size unit and to that end Ive been looking into making my own and good info can be found here [ame]http://www.youtube.com/watch?v=HuM4xSNX0no[/ame]

and yeah, I finally managed to log on again....

 

[Aydelott]

ill a fire clay crucible work for aluminum bronze i just got one an is there anything special about melting chips

 

[abby]

By chips I read swarf? you will lose most of them to oxidation !
This goes for all swarf but aluminium bronze oxidizes mega.

 

[albertorc19]

Ceramic jeweler's crucibles can be useful for small quantities of metal, they are not very expensive just be sure to use the mineral that creates a glass surface on the crucible so the metal won't stick to the crucible's surface and can freely flow when poured.
Jewerlers supply stores carry several items that can be useful for a tiny foundry, up to 1 Kg of metal, they sell small furnances with graphite crucibles, temperature controller, etc. A small furnance will need 15A so it can be used at a common power outlet. The temperature limit is 1100°C which can be considered as adequate for brass.

 

[blighty]

i too have been looking for crucibles for melting Ali. i have found on Ebay some 1kg/2kg graphite crucibles.

would they be ok for Ali?

and just out of interest, what is the 1kg/2kg based on? i know its the weight of materiel it will hold, but volume wise, Ali weighs less than brass for E.g.

 

[Artie]

Its based mainly on gold or silver (different ratingsd), a 2 kilo crucible has a 50mm mouth, very small. The A series is what you are after, here is an example of a A12 Crucible, a useful size in my world. (a $150 crucible landed here in Aus).

#12 Fire Clay Crucible, See Description Below
Holds approximately 58 Lbs Red Brass,
60 lbs Copper,
101 Lbs Gold,
13 Lbs Aluminum----
½ of each with a half full crucible


Shipping Weight 10.5 Lbs

Height: 8-3/32"
Bottom Outside Diameter: 5-1/8"

Top Outside Diameter: 7-1/4"
Top Inside Diameter: 5-7/8"

Wall Thickness: 11/16"
Approx Volume in cubic inches: 146.0

Fireclay crucibles are used for temps up to 1300 deg C

 

[Artie]

and another example, an A5, a cheaper unit, about $65 landed here.

Product May Or May Not Have The Yellow/Green Sticker.
Typical Metal Casting Temperature 1562-2912°F / 850-1600°C
Performance Characteristics
Clean Melting
Good Thermal Conductivity
Good Resistance To Chemical Corrosion
High Refractoriness
Specification:
Height Overall: 5-1/2” - 141mm
Inside Depth to Center: 5” – 127mm
Top Outside Diameter: 4-1/2” – 114mm
Bottom Outside Diameter: 3”–76mm
Capacity: 12.3 Lbs. – 5.6 Kilos BRASS
Weight of Crucible: 2.25 Lbs.

 

[blighty]

Artie, what can i say. that's way more than i needed to know....thx ;D

i'll have a look on Ebay and see what i can find.

Warning!!! stupid question coming up.....

you say these Crucible are made from fire clay. as i'm only Aluminium 660c (1220f) can you use a normal clay plant pot? but obviously with out a hole in the bottom of it.

 

[Artie]

Gday mate, theoretically I say Yes, but in reality, I think that the manufactureres dont care much about quality control and you can get impurities in the clay (stone/small gravel etc) which may not be a good thing to have inside the wall of your crucible, and of course you need one (as you say) without the drain holes.

Probably find that the smaller sizes which we need are a bit thin as well. Id steer clear of that idea.

For what its worth, the graphite reduces oxidisation during the heating, fire clay is good, graphite is better.... but hard to find in a useful size for less than megabucks, hence to need to make my own....

 

[Omnimill]

Casting is not something I'll ever be doing but out of interest what would you mix with fire clay to make a durable crucible?

Vic.