grey iron

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gwrdriver
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Re: grey iron

Post by gwrdriver »

BClemens wrote: Tue Dec 04, 2018 11:03 amI would be afraid of sand - it can melt. Then you'll have a glass coated casting.
BC
Oddly enough common sand and iron melt at about the same temperature, so if you haven't melted your casting you won't melt the sand.
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BClemens
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Re: grey iron

Post by BClemens »

gwrdriver wrote: Tue Dec 04, 2018 9:54 pm
BClemens wrote: Tue Dec 04, 2018 11:03 amI would be afraid of sand - it can melt. Then you'll have a glass coated casting.
BC
Oddly enough common sand and iron melt at about the same temperature, so if you haven't melted your casting you won't melt the sand.
That depends on the sand, oddly enough.... Glass is still molten even as it hangs in a window. Many different types of 'sand' - many different melting points. The differences in melting points of different 'sands' vary far more than iron. I have used glass as a cover over molten bronze at a temperature that iron is well below melting. Pulverized green glass is a very good cover for the volatile ingredients in brass and some bronze but it is caustic to clay graphite crucibles so will dissolve the surface where it makes contact.
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Re: grey iron

Post by OddDuck »

Fwiw, I am still on the learning curve on iron casting, and I have made several batches of wheels that initially were harder than Japanese arithmetic on the rim and relatively soft in the center. I stack a set of eight of them separated by sheets of cardboard (to prevent them from sticking together) in my small propane fired foundry furnace, and let them soak at red heat for an hour or so. This furnace has a hard time getting up to bronze temps, so I know it shouldn't melt the wheels.
I then remove them from the furnace while still red hot and put them in a metal bucket and cover them with a mix of vermiculite and pearlite (nothing special, I didn't have enough of either to fill the bucket...), put the lid on the bucket and walk away overnight. When I come back the next day, they are still almost too hot to handle, but they are then machinable. So home heat treatment can help, you just have to be careful how you heat the parts. If it has spokes or something like that heat it up as slowly and evenly as possible to avoid breaking the spokes from differential expansion. Ask me how I know.
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Fred_V
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Re: grey iron

Post by Fred_V »

My wheel casting is like that. it faced off on the front and bored the axle hole with no problem. it is the tire that was hard.
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Fender
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Re: grey iron

Post by Fender »

I’m not convinced that ductile iron is inherently more wear-resistant than gray iron. I know that gray iron can be made to different specs, with some more durable than others. Certainly ductile (from my experience) is nicer to machine, and probably less likely to fracture than gray iron, but will ductile wheels really wear longer?
Back in the day, railroad car wheels were made with “chilled iron”. The tread was actually formed by a metal mold, whereas the rest of the wheel by a sand mold. This caused just the tread and flange to form “white iron”, which is exceptionally hard (and brittle!). The rest of the wheel was gray iron. I don’t think any attempt was made to machine the tread; it was run on the rail as-cast. The specs for such wheels allowed quite a bit of out-of-roundness and surface defects! Such wheels were very durable, except for when a chunk broke off! The brittleness is why they were eventually banned for interchange use.
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Re: grey iron

Post by jamesjgould »

Ductile will not "groove" at all like grey iron. It is the type of iron lathe chucks and gears are made of these days and is commonly called "semi steel" because it will not crack and break like grey. Any iron foundry worth dealing with can do ductile just as easily as grey and at a tiny increase is $/#. The higher grades of ductile can even be flame hardened directly without the case process.
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Re: grey iron

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Trainman4602
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Re: grey iron

Post by Trainman4602 »

You can use ductile iron grade 80 55 06 you can heat treat it to a 55 Rockwell . A high speed steel tool bit is around 65 rock well.
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