Author Topic: Foundry Furnace for the Tiny Shop  (Read 35665 times)

Offline sparky961

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Re: Foundry Furnace for the Tiny Shop
« Reply #125 on: May 03, 2018, 09:47:53 PM »
Looking good.

Not that it helps you now, but pearlite (slightly crushed) is another good addition to DIY refractory. Available at garden centres.

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Re: Foundry Furnace for the Tiny Shop
« Reply #126 on: May 03, 2018, 10:11:00 PM »
Sparky I've got plenty of it on hand, and used it 17 years ago in the lid of my first furnace (see my Gingery lathe thread), but found it eroded pretty easily compared to the current lid lining, and was difficult to patch after.

The plaster of Paris mix I'm using now is, in my experience even more insulative than the perlite mix I used before. The furnace shell stays noticeably cooler after a similar melt.

If you've ever felt plaster of Paris once it's dry, it is surprisingly light in weight. That's because it is highly porous -- and therein lies the insulative quality.

There's a million ways to skin a cat -- I've worked through a few of them ...enough to know what works best for me -- others will certainly vary.  :beer:
I love it when a Plan B comes together!
Steve
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Offline awemawson

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Re: Foundry Furnace for the Tiny Shop
« Reply #127 on: May 04, 2018, 02:14:50 AM »
. . . Ah all very well BUT

. . . How did they cast the ancient Pillar of Dehli . . .?

Google it  :clap:
Andrew Mawson
East Sussex

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Re: Foundry Furnace for the Tiny Shop
« Reply #128 on: May 04, 2018, 04:12:11 PM »
Forge welded wrought iron, not cast iron, according to Wikipedia.......when I Startpaged it.   :poke:
I love it when a Plan B comes together!
Steve
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Offline awemawson

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Re: Foundry Furnace for the Tiny Shop
« Reply #129 on: May 04, 2018, 05:04:09 PM »
Well done Steve - you are the  only one to find out  :clap: :clap:

It's a myth that it is cast stemming from the Victorian era of the Raj when of course a lot WAS cast !
Andrew Mawson
East Sussex

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Re: Foundry Furnace for the Tiny Shop
« Reply #130 on: May 04, 2018, 07:58:16 PM »
It always seemed confusing to me that wrought iron and cast iron were completely different animals. Wrought iron having less carbon than steel makes sense, "iron" being the element name. But cast "iron" having  more carbon than high carbon steel doesn't. Why call it iron then? Or why steel at all? Just call it all iron, and modify the name by how much carbon it has. Aluminium alloys are always aluminium. I dunno.... there was a time, before I was casting when I thought cast iron was really just pure iron.

Uhhhhhh no.  :wack:
I love it when a Plan B comes together!
Steve
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Offline hermetic

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Re: Foundry Furnace for the Tiny Shop
« Reply #131 on: May 05, 2018, 09:26:08 AM »
Hi VTsteam, When you put iron ore in a blast furnace with coke and limestone, what you get running out of the bottom, is pure iron, but because it has been smelted with coke, it has picked up a high content of carbon. When the run off is allowed to cool it is known as cast iron. Cast iron is very strong under compression, but also very brittle. The process for producing wrought iron from cast was to remelt the cast iron in a reverbatory furnace (where the iron is heated by indirect heat, so it cannot absorb any more carbon) the furnace, known as a puddlers hearth is also charged with iron oxide, and when the iron melts the carbon reacts with the oxygen in the oxide, and boils out of the iron as carbon dioxide. This reduces the carbon content, and after a process of removing from the furnace and power hammering (and repeating) it becomes almost pure iron with fibres of slag running through it, which can be seen on a piece of fractured wrought iron. Take pure iron, minus the slag, and add to it a small amount of carbon, and you have mild steel, useful, but not hardenable other than case hardening. Add slightly more carbon, and you have a tool steel that can be worked and shaped hot in its soft state, and then hardened through and tempered so it is tough, and will also hold a sharp edge. All these metals are Iron/carbon alloys, and this is a gross simplification of metallurgy as learned in the school metalwork shop and from the excellent Hardening, tempering and heat treating by Tubal Cain, No1 in the workshop practice series. hope this helps,
Phil

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Re: Foundry Furnace for the Tiny Shop
« Reply #132 on: May 05, 2018, 10:10:40 AM »
Yup.  I've cast iron. Terry Aspin's books in that same series are some of my favorites.

I'll be tempering the furnace lining today (different kind of tempering) and I hope even casting something, if I can get my old greensand into condition, and the pattern finished.....  :beer:
I love it when a Plan B comes together!
Steve
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Re: Foundry Furnace for the Tiny Shop
« Reply #133 on: May 05, 2018, 09:51:51 PM »
Today I made first heat in the Tiny furnace -- working up gradually to drive the moisture out of the lining. I started out with some wood kindling:

I love it when a Plan B comes together!
Steve
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Re: Foundry Furnace for the Tiny Shop
« Reply #134 on: May 05, 2018, 09:57:51 PM »
I set a piece of stovepipe on top of the furnace lid for a gentle draw -- a blower would have been too much.

When the wood had burned down, I added a layer of charcoal briquettes, about 2 deep. After half an hour again, I filled the furnace up half way with charcoal, and then let it cook for most of the day.

I also conditioned my greensand, which was dry as the Sahara. All in all a rewarding Spring Saturday, with daffodils in full bloom, and my casting gear coming back into some semblance of working order.  :ddb:

I love it when a Plan B comes together!
Steve
www.sredmond.com