# Annealing Cast Iron



## fkrutzke (Jan 24, 2008)

To anneal a cast iron casting that is destroying your tools, take a soft fire brick, like the ones people are cutting alcohol wicks out of, and cut a cavity large enough to hold your casting with about 1 inch all around.

Pack the casting in the cavity totally covered and completely surrounded with black manganese and use a thin slice of the firebrick as a lid. Heat in a ceramic kiln to 1600 degrees. After it has heat soaked enough for the entire brick, manganese and casting to reached 1600 let slowly cool overnight.

I had to use this on several Stuart castings in the past, and it worked very well.

If you do not have a ceramic kiln available you can contact the local ceramics craft shop and have them put it in the next time they fire a load. Just tell them that you need a temperature of 1600 degrees or cone 10.

For small castings I have also used a torch to heat it up. Instead of a firebrick container I used a steel box ( 4 sides and a bottom ) tack welded together and a separate lid. The material was 3/32 sheet steel. Pack the item in the box in the black manganese, lay the lid on, place it on a fire brick and heat with a torch until it is all cherry red and hold it cherry red for at least 30 minutes. Remove the torch and cover it with a lot of fireplace ashes to insulate it from the air so it will cool slowly.

Torry


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## David Leech (Dec 9, 2008)

Hi Torry, 
Not that I am ever going to have to do this, but could you please enlighten me on the 'black manganese'. 
Is it a 'powder', or like 'sand', or a 'jelly'? 
and what happens to 'it' during the heating and cooling. 
Does it stay as it is, or evaporate, or what? 
As I said, I am very unlikely to have to do this, but I would like to know more. 
My brother in the UK has done similar to old wheel castings that he has picked up over the years that have hard spots, but thought that he just placed then in the oven as is. 
All the best, 
David Leech, Delta, Canada


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## Dan Rowe (Mar 8, 2009)

I have machined a few Stuart castings with out any anealing process. The first cut should not be a light one you have to remove the whole skin with the sand in one go. The way large scale cast iron as a 900mm cylinder liner for a Sulzer marine engine is the skin cut is made then the casting is set in the back lot for a year so the casting will normalize. I have been meaning to start that process with my Stuart 6A casting set. 
Dan


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## xo18thfa (Jan 2, 2008)

This is good to know. This would have saved a Stuart #8 I had years ago.


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## Gary Armitstead (Jan 2, 2008)

I have cut many cast-iron castings and I never needed to anneal them to cut them. You do need to get under the rough "skin" in the first cut and from there it's easy. I always used carbide lathe bits to do this. Then you can use high speed after the skin is removed.

I would make another suggestion to save toolbits when machining cast iron. Use a small die grinder and grind down to the virgin iron OR steel, under the skin. We actually did this to get under scale on die blocks to save the cutters (lathe or mill). These blocks were hard all the way through and heat-treated. Annealing is not an option, cut with high-speed cutters. They ranged in hardness from 42 to 50 RC (Rockwell C)


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## fkrutzke (Jan 24, 2008)

Dan and Gary: 
Annealing is not something I would use on a regular basis, but only out of desperation to save a casting. All of the Stuart casting kits that I have machined, dating from the 60's and 70's, have been wonderful Meehanite iron castings that machined like butter. The two problem castings were components of a couple of cylinder set castings, advertised as being Stuart, I bought from Cole's a few years back. The need for annealing was not to get through the skin, but to take care of significantly large hard spots. 

The use of black manganese for annealing was a trick I learned from my artist, machinist and jack of all trades uncle. He had a small foundry to support his bronze sculpture. Occasionally he would cast an item out of iron for one of his mechanical projects. The annealing process was his. 

David: 
For black manganese he used Mineral Black or Pyrolusite, which is a paint pigment and still available from artist/pigment supply houses. The last I bought was from a place in New York. 

Torry


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## Kovacjr (Jan 2, 2008)

When I machined a backplate for my lathe chuck I used only Carbide tooling and took a slow RPM heavy cut at first to remove the skin. 

One thing no one mentioned is that you need to be very careful with the iron dust, very bad to breath in.


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## llynrice (Jan 2, 2008)

I'll second Jason's caution about iron dust from machining. A number of years back, I was drilling holes in a cast iron machine leg and the dust floated through the air and into both eyes. This was in spite of wearing glasses. The opthamalogist could not flush the chips out and had to go after them with a tiny magnetic pick. I was a hurting puppy for several days after. When machining iron, you should consider using safety goggles which fit snuggly to your face all of the way around you eyes.

The voice of experience.

Llyn


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## Semper Vaporo (Jan 2, 2008)

Posted By llynrice on 23 Dec 2009 12:47 PM 
I'll second Jason's caution about iron dust from machining. A number of years back, I was drilling holes in a cast iron machine leg and the dust floated through the air and into both eyes. This was in spite of wearing glasses. The opthamalogist could not flush the chips out and had to go after them with a tiny magnetic pick. I was a hurting puppy for several days after. When machining iron, you should consider using safety goggles which fit snuggly to your face all of the way around you eyes.

The voice of experience.

Llyn


I will third those cautions! But I will extend it to dust from any operation on any material and add another procedural caution.

I have had two problems using a face shield and goggles (you'd a thunk I'd a learned from the first time!).

1st time I was drilling a hole in the ceiling. It was an awkward location and I had to be directly under where I was drilling so I put on a full face shield to keep the wood shavings out of my eyes. Worked real well until I took the face shield off. I had not dusted the top of the shield off (nor my head) when I was done, so when I took the shield off some wood shavings fell into my left eye and lodged in the back of my eyelid and scratched the cornea. Took a long time for the doctor to get the wood out of the back of my eyelid. Eye hurt for weeks like I still had something in it.

2nd time I was turning a brass disk on my lathe. The disk was an old medalion/paperweight and the brass had lots of trash (other metals and "stuff") in it and it was throwing hot chips every once in a while. I was manually turning the handwheel a little bit at a time to advance the cutter and hot chips were burning the back of my hand. So I put a pair of goggles on my face and held my full face shield over my hand to shield it from the chips. Every once in a while I'd feel chips hit my face and I was glad to have the goggles on! Then when I took the goggles off, again I did not dust myself off first and some chips fell in my left eye again. This time it scratched the cornea right through the middle of my vision. I now have a blurry spot in that eye that is very much like the line in a bifocal lens and it varies in disturbance depending on how hydrated my eye is.

So, my additional procedural caution is to dust-off the top of the eye protection and your head before you remove the eye protective device. Also, keep your eyes closed when removing the protective device and your face pointed down so that if there is something you missed falls, at least it will fall past your eyes instead of "in".


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## redbeard (Jan 2, 2008)

"So, my additional procedural caution is to dust-off the top of the eye protection and your head before you remove the eye protective device. Also, keep your eyes closed when removing the protective device and your face pointed down so that if there is something you missed falls, at least it will fall past your eyes instead of "in"." 

Thanks! That is GREAT advice! I always keep a dedicated "clean" bench brush for my shirt and it's always handy. 
Larry


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