Author Topic: Casting Gray Iron  (Read 14395 times)

Offline pirmin

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Re: Casting Gray Iron
« Reply #15 on: July 13, 2024, 02:40:42 PM »
Fantastic work !!!!! the little straight edge is so sweet ! but all the other things are nice too. thank you for sharing your knowledge and information. and dont worry that nobody responds, its mid summer, most people are on holidays , its typical for online forums in summer .

Keep us updated please ! this is very valuable information

Offline Kim

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Re: Casting Gray Iron
« Reply #16 on: July 13, 2024, 05:40:24 PM »
Very fascinating!   I've never been that interested in foundry work, but all your pictures and work you show here make it look pretty enticing!  :ThumbsUp: :popcorn:

Kim

Offline Casting Iron

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Re: Casting Gray Iron
« Reply #17 on: July 14, 2024, 02:16:53 AM »
I appreciate the kind comments.
I had some initial success with casting iron, but could not get consistent results.
I had a really hard time figuring out how to set the burner, how and when to skim slag, how to prevent hard spots, etc.

I gave up more than once over about a six year period, and swore I would never figure it out, and would just use aluminum.

I had several folks who encouraged me to keep trying, and that is pretty much the reason I stuck with it long enough to figure out the entire process.
I am anxious to share this information because I would like to see others in this hobby learn and use it.
Casting engine parts in gray iron is not that much more difficult than casting aluminum, if you know exactly what to do and how to do it.

Pat J
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Offline Alyn Foundry

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Re: Casting Gray Iron
« Reply #18 on: July 14, 2024, 12:18:25 PM »
It’s been a good 40+ years since I dropped my first 10 pounds of Iron.
We used Propane as the fuel for convenience and its energy density is a little greater than Oil. However enough history.

As the use of chemically bonded sand was prohibitive we favoured the traditional Green sand moulding technique. Yes, the flasks are much more bulky but one major advantage is they hold the heat . This heat retention greatly reduces the risk of chills and hard spots. Another factor is to leave the poured flask alone and break out the following day.

The choice of Iron scrap  will play a major role in the machinability of your castings. Try to avoid thin sections that have a Whitish tinge to them. Look for dark Grey.

If you can get hold of it I would recommend the addition of Ferro Silicon to the melt, just before the pour. We used around a teaspoon full per 10 Lbs melted.Thoroughly rabbled with a preheated Steel rod. A small quantity of finely crushed Limestone can be added to the progressing melt to reduce oxidation.

Home casting can be great fun. It also has its dangers.  As with every thing we do common sense should be our guide.

I will make one point stand out however. Water, even in its tiniest amount doesn’t play well with molten metal. I have the scars to prove it. Always make sure that all the tools are thoroughly dry and preferably preheated before use.

We made several engine kits before deciding it was too labour intensive to carry on, as we were all in full time employment.  Today, my kit lies idle. The advent of CAD and the 3D printer have rendered the Aluminium master pattern redundant.

 :cheers:  Graham.

Offline MJM460

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Re: Casting Gray Iron
« Reply #19 on: July 14, 2024, 12:26:12 PM »
Hi Pat, your trials with casting is most interesting, and your persistence is now paying off with such great results.

I can’t contribute to this technology, but I am keenly following your progress.

MJM460
The more I learn, the more I find that I still have to learn!

Offline Dick Morris

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Re: Casting Gray Iron
« Reply #20 on: July 16, 2024, 05:40:29 AM »
Thanks for writing this up. It was very interesting. Having cast aluminum and bronze, this looks very doable.

Online Jasonb

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Re: Casting Gray Iron
« Reply #21 on: July 16, 2024, 07:01:28 AM »

We made several engine kits before deciding it was too labour intensive to carry on, as we were all in full time employment.  Today, my kit lies idle. The advent of CAD and the 3D printer have rendered the Aluminium master pattern redundant.

 :cheers:  Graham.

That is assumming the person wanting the patterns can use CAD, there are many that have no idea how to produce a 3D model of a pattern and for those owning a 3D printer is limited to printing downloaded toys from the net. Unless they can get someone to do the CAD work for them then traditional methods may be all they can use.

When it comes to master patterns as opposed to the one off home casting there is still a need because the 3D printed pattern is not durable enough, think of the Nattie Flywheel pattern for example due to it's thin spokes I did not even want to make that from wood, a plastic print would be even weaker. An alternative to aluminium are the modern 2 part resins where a 3D print could be used to make a mould and then PU resin patterns cast from that which can be bonded to a match board, often several cast patterns of the same part on one board.

Offline Casting Iron

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Re: Casting Gray Iron
« Reply #22 on: July 16, 2024, 01:48:42 PM »
I have had some 3D printed patterns break up, especially the ones with thin infill and walls.
I use a small automotive slide hammer to pull patterns from bound sand, and if you don't exceed the strip time, then the adhesive bond between the sand mold and the pattern can be broken with a light tap of the hammer.

I forgot to pull the patterns one time, and left them in the mold overnight.
The patterns were effectively glued into the bound sand mold.
I damaged most of the patterns trying to get them out of the sand that time; destroying about half the patterns.

I have seen the resin pattern casting material, and hard resin master patterns that can be cast from that mold.
I am not really keen in stocking more resin material though, since it will have a finite shelf life.

Since I am set up to melt alumium, and have quite a few 256 ingots, it would make sense for me to cast permanent patterns, such as for the Ball Hopper Monitor.
Aluminum is easy to melt and pour, since the temperatures involved are so low compared to iron.

With cast aluminum permanent patterns, you can always use JB weld to touch up any bad spots, or to add a bit here or there to the pattern.

And you can epoxy additional pieces onto a cast aluminum pattern; I have seen that, where sometimes adjustments must be made after the pieces are adhered to the matchplate.
I am not a fan of matchplates, since they are really not required with bound sand.
I did use some matchplate arrangements for the green twin engine, and that did work well.
It is very easy to add runners, gates, risers, etc. to bound sand after it has set.
If there was a production run, it would pay to create matchplates.

Edit:
One advantage of the poured resin product to create hard plastic permanent patterns is that the resin will exactly mimic the smooth surface of the pattern.
With a permanent cast aluminum pattern, ceramic mold coat will help get a very smooth surface finish, but the aluminum casting will still probably need to be buffed out with a fine ceramic buffing disk.
I am not sure how stable the hard plastic permanent patterns would be, but I would think they would last a long time, and would never oxidize.
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« Last Edit: July 16, 2024, 02:00:23 PM by Casting Iron »

Offline bent

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Re: Casting Gray Iron
« Reply #23 on: July 16, 2024, 07:30:06 PM »
Very cool writeup CastIron, thanks!  :DrinkPint:

I am in the process of retiring (currently working half time and training a new hire to take over) from being the valve design engineer at my company, where I've been designing bronze and ductile iron castings for production, and then lately forged brass valve bodies too.  I've had the privilege of watching a large foundry here in Washington state operate their jolt-squeeze molding machine and pour our valve castings in ductile iron.  I'm always a bit in awe of real foundrymen, there is a lot of art as well as science to the trade.  We were lucky that for a time, their foundry business was slow, and so for a few years we had them use our parts as fill-in work for their production line.  Then, they got busy with their in-house products again, and we were politely asked to take our products elsewhere. 

 :-\

our local foundry:

https://www.romac.com/foundry

Offline Mcgyver

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Re: Casting Gray Iron
« Reply #24 on: July 18, 2024, 11:22:50 PM »
Good stuff!  Thanks for posting it.

Offline Casting Iron

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Re: Casting Gray Iron
« Reply #25 on: July 19, 2024, 07:43:28 AM »
Thanks to all for the kind comments.

That is a great looking foundry (Romac), with some sophisticated methods, such as the laser guided pours, etc.

I read several casting journals regularly, and there is a good market for ductile iron castings, since they often can meet or exceed the strength of steel, but with a lower cost.

Kory Anderson (150 hp Case guy) uses ductile iron for flywheels and other items, but I really only need ductile iron for crankshafts.

It is exciting to see US-based foundries with high quality products, and this on-shore capability solves the supply chain problems that we have seen in recent years, as well as provides jobs for folks located here.

I am in the wastewater renovation business (electrical side of things), and there is a lot of money involved, given the large size of many plants, and the dedicated operational and repair funding that the EPA requires.

Learning the methods of making ductile iron has been more difficult than learning to pour gray iron, and I have had to pick out bits and pieces of critical information about how to do it on a small scale from suppliers and an occasional person who has worked in iron foundries.
Some folks know ductile iron on a large scale, but can't really give helpful information about how to do it on a small scale.
I think I have it figured out, and I think I have all the materials required to do it successfully, so we shall see.

I feel like preserving the knowledge of how to pour gray iron is critcial to keeping the model engine hobby alive in the US, and pouring iron engine parts is just downright fun.

I hope to get to the point where I can make more iron castings in the near future.

Thanks for everyone's interest.

Pat J
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Online Jasonb

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Re: Casting Gray Iron
« Reply #26 on: July 19, 2024, 08:57:48 AM »
I would have thought you could use Ductile iron on more parts than just crankshafts Pat.

Any cast part that is long and slender will be far more durable and less likely to get broken than if it were made from regular grey iron. Other kit producers use it for things like valve rockers & posts and on the monitor the pivoting arm of the cam follower and the governor weight would be best done in ductile.

Offline Casting Iron

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Re: Casting Gray Iron
« Reply #27 on: July 19, 2024, 09:50:10 AM »
The ductile iron casting process is more involved than just casting plain gray iron.
The sulphur has to be controlled, and the inoculation process I will use takes place in a lined container, which will be somewhat wasteful just due to the nature of the setup.
And I have a finite amount of ferromagnesium, and don't have a supplier for that.

So there are some challenges ahead, such as verifing the exact process in a backyard setting (I have seen it done, and so I understand how to do it).

For long thin parts, it will require a lot of fluidity, and I have an additive for that too, but again, a finite amount with no supplier.

One of the biggest challenge for me, and I think one of the biggest challenges for hobby casting folks, is finding small quantities of commercial materials.
Generally, one has to know someone in the industry in order to get some of the materials.
I have done a lot of begging to get what I have.

You can purchase materials by the 55 gallon drum, or by the ton (sand), but smaller quantities are very difficult to source.

The ductile iron making process is a volatile exothermic reaction, and the exact volatility depends on the percentage of magnesium contained in the additive.
One wants enough magnesium to give good results, but not so much magnesium that it melts your entire reaction chamber.
I think I can make ductile iron, but I don't think I would want to cast it routinely, especially without finding a readily available supplier.

It is very difficult to find art-iron folks who do ductile iron, and the ones I have found don't really discuss how they do it.
It is a very secretive thing, perhaps just from a general lack of knowledge.

Here is a video of a ductile iron attempt.
It was not an explosion in the ladle, but rather just a very aggressive reaction, and way too agressive in my opionion.
I can't find anyone to even discuss this attempt, but obviously, great caution must be used with this process.

<a href="https://www.youtube.com/watch?v=SQLAdOg6V5g" target="_blank">http://www.youtube.com/watch?v=SQLAdOg6V5g</a>
« Last Edit: July 19, 2024, 10:02:30 AM by Casting Iron »

Offline Casting Iron

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Re: Casting Gray Iron
« Reply #28 on: July 19, 2024, 10:26:34 AM »
I think a typical small reaction chamber for making ductile iron can be seen in this video at 10:20.
The chamber would need to be lined with 3,800 F plastic refractory, and it must have a pocket on one side for the ferromagnesium.
The reaction is relatively mild, and would be messy without a tall vented chamber.

And if you don't control the sulphur, then you are not going to get ductile iron.

It should be noted that the IR (infrared) coming out of a hot furnace, from the crucible, and from the top of the melt, is very intense, and without wearing shaded gas welding glasses, you can have sunburn in the eyes after a single exposure.

<a href="https://www.youtube.com/watch?v=xrLkm243_-8" target="_blank">http://www.youtube.com/watch?v=xrLkm243_-8</a>
« Last Edit: July 19, 2024, 10:29:48 AM by Casting Iron »

 

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