Building Furnace

I'm just getting started in casting, got supplies & parts on order. Planing on building an oven type furnace
using fire bricks with an angle iron frame. Should I do anything other than just enclosing the bricks or do I
need to coat the interior with something ? The cavity will be appx. 9" long by 5" wide by 5" tall.

Thanks for any suggestions,
John ,,,,

 

Is this an electric or fuel fired furnace, like propane?.

 

Coating would depend on what kind of bricks your using. Are they insulating bricks (soft), or dense bricks? Your fuel source might matter too. From your dimensions it sounds more like a forge than a typical furnace.

Pete

 

They are the solid high temp bricks,,,, fuel will be propane burner.

 

Propane

 

1 kg clay graffite

 

This what I have in mind, the bricks are same as I will be using ,,,




This burner, regulator is 30 psig, don't know the burner tip size.

 

One of the reasons for having a vertical cylinder shaped furnace (or octagonal) is that the hot flames can form a tornado like spiral around the crucible which evens out the heating and allows high rates of burn for melting of brasses, bronzes and maybe even iron. That propane forge in the video is ideal for achieving higher temps simply by reducing heat loss with the brick insulation.

 

Thanks Mark for your reply. By just starting out I thought this might be the best way, I'm fairly
handy with metal work so it seemed simple enough to start. After I get a bit of experience I want
to build a vertical type. I have an old propane tank, the 20 lb I think, circa 1976 I'm thinking of using.
Quick question, I have a lot of brass valves, mostly water, that I plan on casting with, are most pure brass
or alloy of some type ? I'd like a fairly hard alloy for the bronze age axe I'm going to try. I have copper
if that would work to harden the mix.
Again thanks,,,,

 

Yep plumbing fittings like larger valves etc. are 85 copper, 5 tin, 5 zinc, 5 lead with modern stuff having bismuth instead of lead. Brass and bronze fitting can be filed or sanded and let tarnish a bit for a few days and you will see pink tints for bronze and yellow tints for brass. You don't want any zinc in your axe head if you plan to braze some stellite or similar to get a hard edge. For comparison the top container is red brass/LG2/85-5-5-5 bronze swarf and the bottom bag is plain old brass like household taps are made from. The bronze has a distinct copper/pink colour compared to the yellow brass.

Your hardest bronzes are going to be manganese bronze or aluminium bronze but stellite hard facing filler rod TIG brazed on is still harder again (like tool steel).

 

as Mark said Manganese bronze is a very good choice for tools, axes, knives pliers (explosion proof or spark resisstant)
its also easy to spot by use, gears and anything made for wear resistance is VERY likely to be Manganese bronze , it will be slightly magnetic it has 1-3% fe , but it looks more like brass, its often called Mag Brass,

for an axe, you want as close to lead free as possible , so plumbing fittings are a NoGo, unless you are going to do something like he recommends , though i don think that would work well on an impact tool, I would expect the hardface to chip off as the bronze behind it deforms under normal use, on a Knife it Might be awesome, ( I also dont know how well Stellite holds an edge)

V/r HT

 

Thanks guys for all info ! After reading and the videos I decided to just use the valve metal as is. The axe
will probably just be a wall hanger anyway. As this will be my first try it's mostly going to be practice. I'll have the
wax pattern done soon, probably put to much effort into it but I'm learning on it too.
Another question, how's the best way to melt out wax after mold has cured ? I was thinking
use a hand held propane torch just prior to casting to also preheat mold.

Thanks again to all,
John ,,,,

 

Well, got the pattern and mold done, I forgot to photo the pattern after I put the little side ring on.
Cleaned up the mold a bit, don't want no ugly first time mold. It should be well cured before
I get the furnace built. Thinking about making a dagger mold too, might as well, have it ready.

 

Say John, what is that material you’ve coated your wax model with?
Pete

 

Pete, no coating, I just got it as smooth as I could then slightly heated the surface
with a hair dryer and smoothed with my fingers. Got all my stuff delivered except
the bricks. Working on some tongs as I wait.

 

Oh, I thought that center photo was the wax coated in some sort of investment.
Nice work on the wax by the way.

 

The mold looks like the pattern invested in plaster. If your planning on burning that out with a torch and pouring into it I would think again.

I'm in a rush but the other experts can explain. (If I've got that wrong my apologies)