Author Topic: Oil fired crucible furnace  (Read 66975 times)

Offline awemawson

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Re: Oil fired crucible furnace
« Reply #150 on: August 05, 2013, 04:45:20 PM »
OK Steve, confess, which professional foundry did you get to do that  :clap:
Andrew Mawson
East Sussex

Offline RussellT

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Re: Oil fired crucible furnace
« Reply #151 on: August 05, 2013, 05:14:20 PM »
Great work.  Persistence pays off.

 :bow: :clap: :bow: :clap: :bow: :clap: :bow: :clap:

Russell
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #152 on: August 05, 2013, 09:28:31 PM »
Wow, thank you all! That just feels great!   :bow: :bow: :bow: :bow:  :beer:

 :mmr:
I love it when a Plan B comes together!
Steve
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Offline ironman

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Re: Oil fired crucible furnace
« Reply #153 on: August 06, 2013, 08:30:11 PM »
That looks really great.

What did you do to make this one a success?

Offline tom osselton

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Re: Oil fired crucible furnace
« Reply #154 on: August 06, 2013, 09:05:24 PM »
Well done definetly a keeper!!  :beer:

Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #155 on: August 06, 2013, 09:20:28 PM »
Tom, Ironman, thank you.  :bow:

Ironman, to answer your question:

1.) I made a new pattern, reversing the draft, so I could place a riser on the non-channeled side. I could not put a riser on the old pattern because it would mess up the channel. Previously the riser was beside the pattern -- the only place it could be with the pattern draft the way it was oriented.

By altering the draft orientation and placing the riser on top of the pattern, any buoyant slag could go up the riser rather than get trapped in the channel section of the casting. Also the channel section now faced downwards, so it would naturally be protected.

While these changes would help deal with any slag in the mold, I have been on a concerted effort to eliminate slag coming into it in the first place. So:

2.) I altered my melt method to add iron later in the furnace cycle -- after the crucible and furnace walls had reached a red heat. My furnace has more mass than a blanket insulation furnace, so it has a longer warm up period. There is no reason to put iron in during this period and allow it to oxidize. I started with an empty crucible.

And to save fuel, there is no reason to run the warm-up at full throttle. 1/4 throttle works fine to bring the furnace walls and crucible to red heat. Time is more important than burner temperature for this. Once it is at red heat, metal can be added, and the furnace run at full throttle.  At this point the furnace will melt at an average rate of 1 pound per 5 minutes.  Gradually accelerating to 1 pound per 3 minutes.

3.) I gave it a longer post melt heating period to try to get the pouring temperature as high as I had patience for. That was about 15 minutes after all the iron was melted. I wanted any slag to come to the top and amalgamate, and for the casting to be fluid enough to give any slag time to come up the riser.

4.) I altered the mix ratio of the flame -- I had been running slightly richer on previous melts -- I went almost neutral -- ie. a couple almost imperceptible whisps of black smoke from the lid edges (not the glory hole). I believe this created hotter furnace temps.

5.) I increased the pressure of the burner to 60 PSI. This burner is an atomizing burner. There are two air sources, the blower (a vacuum cleaner) and the atomizing air nozzle fed by a compressor. That last one is what was increased to 60 PSI. This fed more fuel at a smaller droplet size. The flame was naturally bigger.

6.) The new better quality larger capacity crucible did not add slag to the melt, and its larger size (with more metal) retained heat better when bringing to the pour.

In other words, a lot of variables were adjusted. Apparently for the positive.



I love it when a Plan B comes together!
Steve
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Offline Meldonmech

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Re: Oil fired crucible furnace
« Reply #156 on: August 07, 2013, 04:20:18 AM »
Hi VT,
           Well you got there in the end, and what a nice result.

                                           Well done   David

Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #157 on: August 07, 2013, 07:36:59 AM »
Thanks so much David!  :beer: :beer: :beer:

I'm going to cast some new flasks in aluminum today, iron is tough on wood ones.  :dremel:

Well, I'll need a new wooden flask to cast the aluminum ones, so I guess I'll be making that, too!  :)
I love it when a Plan B comes together!
Steve
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Offline Mayhem

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Re: Oil fired crucible furnace
« Reply #158 on: August 07, 2013, 07:45:49 AM »
Excellent job there Steve - I'm glad you stuck with it and took us along for the ride.

Offline tekfab

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Re: Oil fired crucible furnace
« Reply #159 on: August 07, 2013, 08:33:48 AM »
Well done Steve, for my own reference what crucible have you ended up using ? I'm about to build my own furnace and i may as well utilise your experience. I'll be starting of with Aluminium but would like to progress to iron so what would you recommend.

Mike

Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #160 on: August 07, 2013, 09:20:09 AM »
Thanks tekfab!  :beer:

I'm hardly in a position to recommend crucibles since my experience before was poor, and my current crucible has only been used for 3 iron melts. So I can't say long term if it will hold up for me, under my conditions of use.

But it looks good so far and is far better than the "3000 degree" (advertised) clay-graphite crucibles I started with, so I have hope for it.

Personally, I would try to get the same brand crucible that Ironman uses, which is Vesuvius. And I believe more specifically it is the "Diamond" hard variety -- though not sure about that exact term.

The crucible I have now is an A6 MorganMM Salamander Super and the label said A&0130H0165&-SUX4-3GN-IL, and made in INDIA. It was close to $75 delivered.

But whether that is good or bad, I don't know yet. Let's get 20 more castings under our belt and see how it does!

But for casting aluminum, I would never use an expensive crucible. I would just continue to use a cast iron plumbers pot, or a made up one from steel, lined with a little fireclay and sand mix.
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #161 on: August 07, 2013, 10:05:00 AM »
Mayhem, thanks, man!  :beer: I may be building a forge like you did soon. How is your lathe doing?
I love it when a Plan B comes together!
Steve
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Offline awemawson

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Re: Oil fired crucible furnace
« Reply #162 on: August 07, 2013, 12:04:58 PM »
I've always been concerned with iron dissolving into molten aluminium when using a steel or iron crucible. So I always used a clay/graphite one. Even small quantities of iron in aluminium make significant alterations to it's mechanical properties. Though I am aware very many home casters do use steel.


http://www.aomevents.com/conferences/afi/papers/Taylor.pdf
Andrew Mawson
East Sussex

Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #163 on: August 07, 2013, 01:31:40 PM »
Andrew, good to mention.  The cheapskate high quality alternative to both schools of thought is a clay lining in a homemade steel pot.

I suppose the ingots could be poured in a greensand mold instead of a steel one -- but the last seems almost universal on the casting forums.
I love it when a Plan B comes together!
Steve
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Offline awemawson

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Re: Oil fired crucible furnace
« Reply #164 on: August 07, 2013, 02:05:16 PM »
I suppose it really depends on what you are doing with the castings. If they are only ornamental, or so generously proportioned that strength isn't an issue it could be said that it doesn't matter. But if you want to be able to heat treat the casting and get particular machining qualities especially, then iron anywhere near it is a no no. As that article says, once the iron is in the aluminium effectively it's staying there for good!

I always avoided use  of steel crucible, and used a dip wash coat on the various tools I used such as stirrers and skimmers. Problem is that the over metal that is poured to ingot may be used for something more fussy than the current one, but you've already contaminated your stock
Andrew Mawson
East Sussex

Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #165 on: August 07, 2013, 03:04:55 PM »
I'm really don't see myself doing that kind of thing with aluminum castings, Andrew, but if other people are, please don't follow my example!   :) 

I work with old pistons, bell housings, marine engine castings, old sprues and an occasional extrusions combined as melting stock, so heat treating this bastad mix probably wouldn't turn it into a silk purse! Those steel clips in the pistons don't guarantee iron-free aluminum either -- they were cast in place, so I'm sunk by GM and Ford from the start!

Spent the day making handle loose pieces for the pattern for the new flasks. And then making an even bigger wooden flask to make the flasks in. Kinda like a fish eating a smaller fish, eating a smaller fish, etc.
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #166 on: August 12, 2013, 11:12:51 PM »
Back to iron....I should update this thread. . .

I ended up building steel flasks rather than aluminum, though I did make an aluminum flask casting pattern in case I get a lot more aluminum some day. The construction of the simple steel flasks is located in a separate thread by that name. I also cast a new iron piece for my steam conversion in the new flasks and it went very well. I'm definitely liking the new gear. I also poured a second melt -- just some ingots made from scrap radiator material to clean the metal for future pours. I figured once the furnace was hot from the first pour, it made sense to do a little more melting.

So far the new crucible has held up very well. I haven't used any flux with it however. The last pour of ingots from radiator scrap does appear to have left some of the old pasty slag in the crucible -- I'm thinking of adding a little flux, cautiously, toward the end of the next pour to see whether I can liquify the pasty stuff, clean up the metal better and leave a cleaner crucible.
I love it when a Plan B comes together!
Steve
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Offline Meldonmech

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Re: Oil fired crucible furnace
« Reply #167 on: August 13, 2013, 12:15:05 AM »
Hi VT,
           That is a an amazing result, and justifies all your hard work and determination

                                         Well Done    Cheers David

Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #168 on: August 13, 2013, 09:11:22 AM »
Thanks David!  :beer:
I love it when a Plan B comes together!
Steve
www.sredmond.com

Offline DMIOM

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Re: Oil fired crucible furnace
« Reply #169 on: August 14, 2013, 04:52:37 AM »
Steve,

I've just seen the photo below of your new carbide mill cleaning up one of your castings. Not only is the mill working well but very impressed how clean & homogeneous the casting looks.

Dave  :clap: :thumbup: :clap: :thumbup: :clap: :thumbup: :clap:

Does a nice job, too. This was what it did to a back yard casting.



« Last Edit: January 14, 2018, 11:39:34 AM by vtsteam »

Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #170 on: August 14, 2013, 07:26:19 PM »
A pretty sight -- an evening pour beginning to cool.


« Last Edit: January 14, 2018, 11:40:12 AM by vtsteam »
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #171 on: August 14, 2013, 07:32:16 PM »
Thank you Dave! :bow: :beer:

When I think about it, it is kind of amazing to take some old rusty radiators and some waste oil and have it turn into something that looks like that.
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #172 on: August 15, 2013, 04:17:00 PM »
This is yesterday's casting. I decided to try pure (rusty) radiator scrap -- not refined ingots, sprues, prior castings or thicker iron. I did the opposite of what I've been doing recently, and added the metal to the crucible before bringing to a red heat, added charcoal to cover, and added a tablespoon of sodium carbonate (fingers crossed the crucible wouldn't get messed up).

Then I continuously added more Iron as the stuff in the crucible melted. Finally just before the pour, I added about a tablespoon more of the sodium carbonate, stirred and waited another ten minutes. Finally lifted the crucible set it in the shank, scraped the slag off quickly and poured.

Looks as good as the last one -- the little spot is just where a vent wire hit the pattern, but not a structural flaw. This face will be machined and the bore widened.

« Last Edit: January 14, 2018, 11:40:54 AM by vtsteam »
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #173 on: August 15, 2013, 04:20:35 PM »
Here is the top of the casting. No shrink depression or slag inclusions. Just goes to show you don't need pristine metal to get a pristine casting.


« Last Edit: January 14, 2018, 11:41:57 AM by vtsteam »
I love it when a Plan B comes together!
Steve
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Offline NeoTech

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Re: Oil fired crucible furnace
« Reply #174 on: August 15, 2013, 04:31:13 PM »
Sweet looking casting.. You seem to have boiled out all the impurities of the process...  =)
Machinery: Optimum D320x920, Optimum BF20L, Aciera F3. -- I have not failed. I've just found 10,000 ways that won't work. http://www.roughedge.se/blogg/