Just changed the front brake rotors on my 18 year old Toyota pickup: The iron grooves easily with a grinder and will break up after a few belts with a large 2 kilo hammer. It has a grey appearance with visible grains, files very easily: softness on a par with mild steel and I notice it dented a few times when hit with a hammer. Does this sound like ideal scrap for casting?. Keep in mind it's got to be better for furnace experiments than the mystery iron weights that are some sort of remelted scrap. What do you people think of it?. I could add some silicon carbide as a substitute for ferrosilicon to improve it. Edit: From the limited information the web it looks like iron rotors are commonly made from nodular/ductile iron.
I read something about them recently, but have forgotten what I read, or where. I will try and remember where I saw something. Here is ironside's slant on using brake rotors. He seems to have good luck with them.
That guy has forgotten more about cast iron than most of us know combined. HT1 is another cast iron guru, I bet he'll chime in soon.
Brake rotors are reputed to be too hard to be machined without cerametal tooling yet these particular rotors seem to have good properties. Ironside's video using rotors with ferrosilicon additive proves it can be used to get a good grey iron. If rotors end up being a source of ductile iron that would be awesome. Edit: After watching Ironsides video again, it looks like ferrosilicon will be key to getting a good result.
As I recall from the iron foundry I used to work at, scrap rotors were considered good 'virgin' iron. I was told they were usually made from new iron because recycled scrap wasn't consistent for rotor use. Our charges consisted of scrap steel, pig iron, 'virgin' scrap (mostly rotors) and foundry scrap/returns. Granted, this was all chucked into a cupola which does change the chemistry, and then treated/alloyed before pouring for whatever grade we needed.
That makes sense, rotors have to be consistent from batch to batch and using random of scrap isn't going to work. Rotors seem to be ductile iron rather than grey iron for improved mechanical properties, I'm not sure if remelting ductile keeps those properties: I think that's one of Ironside's videos where he reuses some.
I don't think they are ductile, I think they are normal grey iron. I've broken some up before, ductile bends way more, has a different ring to it. We had to be very careful with our ductile returns in the Cupola, the alloys in them do not burn off and will throw off the melt if we added too much. Ductile requires a pretty stringent heat treat process so melting & re-casting it will lose it's properties
Isn't there two types of ductile iron?, one made with heat treating normal grey iron and the nodular iron one made by adding magnesium or cerium in small amounts?. These particular rotors just dent a bit before breaking after a few blows but don't really bend much. I guess if I was casting iron, grey iron or ductile iron is fine either way.
