Crucible question

[woodnut]

Hi All

I have a possible bronze casting job. Before I say "yes" I can do it, I need to know if I use a mild steel crucible or should I make one out of refractory? My concern with the refractory crucible is it crumbling or breaking if it not made right or dried out right.

I did a quick search and found that mild steel will melt at around 2800 F and Bronze is about 2100 F. But I don't want to have to post in the Mistakes, Blunders and Boo Boos form when I am done.

Thanks in advance

John.

 

[doubleboost]

It is possible to use mild steel but not ideal
It needs to be thick mine was 6 mm wall tube with a 8 mm bottom welded in place
A propper silicon carbide or graphite crucible is much better at transferring the heat
[ame]http://www.youtube.com/watch?v=NH2GrHW4mQE[/ame]
This is a steel crucible
John

 

[dalem9]

That was a really good viedo Thanks for sharing Dale

 

[woodnut]

Thanks Dale

Great Video! I am sure I seen this before when looking through the posts before I jointed. I watched it again anyway. I think a steel crucible would the easiest and cheapest route to go for now. The job is a small run of tile inserts, just not sure on the size of them yet.
Just have to find someone to weld it for me? There should a welding place around here somewhere. Off to Google.

Thanks

John

 

[JorgensenSteam]

I have seen some bronze alloys melt in the 1600-1800 F range, so you may not need 2100 F for the melt.

I made this crucible out of heavy steel pipe and plate.
Stick welded.

I like the steel crucibles because they will not break, and are easier to lift out without worrying about a crucible fracture.

They do get very hot, and you may want to consider a heat shield on the end of your pouring shank.

The fumes can be very bad too, so watch out for that.

I use a small hook on one side of my pouring shank to secure the crucible when I rotate it. The first time without the hook, the crucible tried to slide off the end of the shank.

I made the bottom plate the same size as the ID of the pipe, and then welded in the 90 degree gap, using about 3 passes, cleaning the weld between passes.
Welded the inside bottom edge as a final pass.

Edit:
John has a much better method with the T-studs on the side of his crucible, which make for a simple lifting shank with J-hooks.
I am going to cut off the handles on the sides of my crucible and change to the T-studs like John has.

Edit 02:
Or I may just add a set of T-studs and leave the loops I have, since the loops allow me to use a pouring shank, which gets me away from the very hot crucible, and gets the crucible away from the top of my feet.

 

[JorgensenSteam]

I added a tab on the end of the bracket of this pouring shank to keep the crucible from slipping off.

I also added a handle straight down, which makes pour control easy once the crucible is tilted.

If you are pouring brass/bronze using a pouring shank, you may want to experiment with a dummy load on the end of a stick, and make sure you can actually lift that much on the end of a shank. My pours have been aluminum so far, and it is not that heavy of a lift.

 

[Lakc]

I try to make everything possible myself, but when it comes to crucibles, I buy them for the safety factor, as well as not adding any steel contaminants into the melt. IMHO YMMV and all the standard disclaimers.

 

[woodnut]

Thanks everyone.

It's great getting really useful information for a change rather then the blank stares I am used to.

Thanks again

John.

 

[ShedBoy]

Just found this post have you seen this shop on fleabay?
http://www.ebay.com.au/sch/jetstool...&_odkw=&_osacat=0&_trksid=p3911.c0.m270.l1313

Seems to have some reasonable looking crucibles at decent prices. Alot of work goes into making a refractory crucible so it seems from what I have read.
Brock

 

[JorgensenSteam]

You can purchase crucibles for non-ferrous metals in the US from here:
http://www.budgetcastingsupply.com/Crucibles.php

There is a guy on YouTube doing some very advanced engine work with aluminum melted in a steel crucible, and I see no sign of contamination problems (although I would not know what to look for).

Myfordboy is here:
[ame]http://www.youtube.com/watch?v=IYZOTt9zTv0[/ame]
[ame]http://www.youtube.com/watch?v=B5wCVI7jCyQ&feature=mfu_in_order&list=UL[/ame]

So my question is, if you can produce castings like Myfordboy using a steel crucible, then why use anything else?

You have to be very careful with non-steel crucibles, and if you drop it, or lift/pour without the proper shanks then you will damage and rupture it.
The best non-steel crucibles will eventually wear out and rupture, which is extremely dangerous.

If you just want to kick around some melted aluminum, why not use a heavy walled crucible like John has above?
You can abuse the heck out of a steel crucible, drop it, use it for a hammer, etc., and it just keeps on going, no problems.

If you are really going to get into castings, you can always upgrade to a non-metal crucilbe, but be sure to use the correct lifting and pouring shanks, don't drop or abuse the crucible, and don't store the crucible where it can absorb water.
Non-metal crucibles have to be tempered to set the outer coating, and then brought up to full heat for 30 minutes or so before you first use them.
You never want any moisture to get near a non-metal crucible.

Steel crucibles are very hardy and durable, and will take almost any abuse, including dropping it when red hot on concrete (don't ask me how I know).
If you get the technique down with steel, then think about non-metal crucibles.

If you use petrobond sand, you can avoid a lot of moisture/gassing issues, but you still have to know what you are doing.

 

[ShedBoy]

I have a steel pipe crucible, a cast iron pot and have not noticed any issues with it. There is a bloke who works at the same place as me who uses a cast iron pot the same as me and fires it to red hot before adding ali to it, this removes the oxide from the surface so he says, don't know if it is true or not. Personally I have never used any flux or degassing yet, just skim crap off the top and pour away. Usually get a skin of crap left which the melt leaves behind. I also have a purchased crucible which has not been used yet along with two other clay types which were given to me by a fellow forum member, his Mum was using them for flower pots in her garden!
Brock

 

[Omnimill]

Any use?: http://www.lindsaybks.com/dgjp/djgbk/cruc/index.html

Vic.

 

[woodnut]

Thanks Vic

I remember buying that book, but can't find it to save my life.
It was cheap enough, will have to buy it again.

John

 

[tel]

A steel crucible will be seriously weakened at molten bronze temps - it can be done, but take extreme, extra care AND be sure you use a crucible wash on the pot - inside and out

 

[ShedBoy]

Tel, is crucible wash the same as refractory wash? I have no idea what either of them are, read it before though. Can you make your own? do you need it with clay graphite crucibles?

Brock

 

[doubleboost]

Steel crucibles are fine for aluminium
Bronze is pushing things look at the colour of mine steel is not strong at these temperatures
I would not like to have dropped it
After using graphite / silicon carbide i will never use steel again for bronze
If you are prepared to build a furnace crucible tongs and a pouring shank take very little making
Don't forget molten metal will go straight through your skin flesh and bones
Use propper safety gear and common sense
John

 

[steamer]

You may want to look at these too.

http://www.homemodelenginemachinist.com/index.php?topic=15199.msg157079;boardseen#new

Dave

 

[woodnut]

Well it looks like this possible casting job is a dead end.

But I did learn a lot about crucibles and if I do temp brass or bronze in the future I think I will spend the money and order proper one. The links you guys provided are great and they not as pricey as I thought.
My current steel crucible is fine for aluminum and I don't have any brass right now to melt.

Again thanks for all of your insight. Hopefully others can use this info as well.

John

 

[Lakc]

Well it looks like this possible casting job is a dead end.

But I did learn a lot about crucibles and if I do temp brass or bronze in the future I think I will spend the money and order proper one. The links you guys provided are great and they not as pricey as I thought.
My current steel crucible is fine for aluminum and I don't have any brass right now to melt.

Again thanks for all of your insight. Hopefully others can use this info as well.

John

Common #6 or #8 graphite crucibles for the home shop can be found for $20-30 usd. Thats very reasonable, and you still get to put some homebrew effort into a nice set of tongs.

 

[tel]

Common #6 or #8 graphite crucibles for the home shop can be found for $20-30 usd. Thats very reasonable, and you still get to put some homebrew effort into a nice set of tongs. Smiley

You won't get a lot of change out of $100 here in Oz