# Gas furnace melted iron



## kjavanb123 (Aug 12, 2020)

Hi

I have modified the gas furnace so crucible can be fixed inside the furnace and I am able to tilt to pour off the slag and metal.

I had used four screws and nuts to keep the crucible in place, after running the furnace, noticed the crucible sinked to the buttom of furnace and sparks flied out.

I noticed that two of the iron screws were melted ! 

Here are some photos



Here are the screws that melted



And this



This furnace is based on venturi torch so n air blower needed just a gas tank and u can smelt


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## butcher (Aug 12, 2020)

Make a small pad for the crucible to sit on out of castable refractory, or you could use another old broken crucible, or a fire brick, cement it into the bottom of the furnace to sit your good crucible on top of...

I would look into getting some castable refractory clay and some refractory mortor, to improve the furnaces ability to retain heat...


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## philddreamer (Aug 12, 2020)

Were the screws mild steel?
If so, next time try stainless steel... they seem to hold better under fire! :mrgreen: 

Phil


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## kjavanb123 (Aug 13, 2020)

butcher said:


> Make a small pad for the crucible to sit on out of castable refractory, or you could use another old broken crucible, or a fire brick, cement it into the bottom of the furnace to sit your good crucible on top of...
> 
> I would look into getting some castable refractory clay and some refractory mortor, to improve the furnaces ability to retain heat...



Thanks butcher I make sure to add that into my next design which is progressing now.


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## kjavanb123 (Aug 13, 2020)

philddreamer said:


> Were the screws mild steel?
> If so, next time try stainless steel... they seem to hold better under fire! :mrgreen:
> 
> Phil



I didn't know gas furnace like that can reach those range of temperature. I am planning to insulate those escrows using kaewool. 

Thanks and best regards
KJ


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## philddreamer (Aug 13, 2020)

I found more detailed info:
" The effects high temperatures have on steel depend entirely on the amount of carbon and other alloys the steel contains. A higher carbon content brings the melting temperature down, but since mild steel has a carbon content of up to 0.3%, it has a relatively high melting temperature.

A high melting temperature means that mild steel becomes more ductile when heated, and it is therefore suitable for forging. This makes mild steel a very versatile material which is suited to a huge range of applications – including in structural projects, a good example of which being the use of reinforcing bar in cast concrete.

Typically, mild steel has a melting point of 1350oC-1530oC (2462oF-2786oF) depending on the grade of the steel as dictated by the amount of carbon it contains."

And for Stainless Steel:
"Here is a list of different stainless steel alloys and the temperatures at which they melt (data based on figures from the BSSA):

Grade 304. 1400-1450°C (2552-2642°F)
Grade 316. 1375-1400°C (2507-2552°F)
Grade 430. 1425-1510°C (2597-2750°F)
Grade 434. 1426-1510°C (2600-2750°F)
Grade 420. 1450-1510°C (2642-2750°F)
Grade 410. 1480-1530°C (2696-2786°F)"

I hope this helps! 8) 

Take care!
phil


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## kjavanb123 (Aug 13, 2020)

Thanks Phil for your info on steel.


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## kjavanb123 (Aug 15, 2020)

Hi

Per advice suggestion by Phil I replaced the screws with stainless steel ones and it worked.

Now this gas furnace with crucible in it can function like induction furnaces that crucible can be tilted.

Thanks and best regards
KJ


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## Smack (Aug 19, 2020)

If you can get them, B7 bolts perform well under high heat and just for information, L7 bolts perform well under extreme cold.


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