What is in brake rotors?

[CI]

The problem for me is translating numbers on an analysis chart into something finite and measurable, like hardness, ductility, machineability, etc.

The guy out west purchased a hardness tester, and he actually got some good usable results out of testing the hardness of his castings across the entire casting, which was I think 36" long.

It seems like it is quite tricky to make something meaningful from the number.
Perhaps measuring sulphur content would be helpful, but I will be using the same treatment regardless of what iron scrap I use to make ductile iron.

I do notice machineability, and can tell if the metal is overly hard, since my carbide bit starts to struggle a bit.
Very machineable gray iron produces a hissing sound with a carbide bit, with no vibration, oscillation, very consistently small chips, and with a very good surface finish.
Cutting through the mill scale on cast iron is noticeably more difficult, louder, and a rougher more uneven cutting process.
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[vtsteam]

So, does copper also evaporate while melting?

Copper is not a volatile metal like magnesuim so there will be low loses adding it and will persist when remelted. As for melting loses when remelting it can be a guessing game but I found over the years melting cast iron is no problem provided you melt the same known scrap that has given a good result in the past.

@airmodel okay, good to know copper will stay. I haven't had a consistent source of scrap iron in the past. I've switched to rotors because they are easy to find in my rural area and that seems like the closest I'll get to a consistent type.

@CI for pouring temp I go by whether a 1/4" round steel stir rod comes out shiny pointed, vs. clumped with melt.

[CI]

@CI for pouring temp I go by whether a 1/4" round steel stir rod comes out shiny pointed, vs. clumped with melt.


Some have noted that the surface becomes different at pour temperature, or perhaps the melt starts to roll.
The steel stiring rod is an interesting method.
Typically I run the burner for about an hour with a #10 crucible, at 2.7 gal/hr diesel.
Normally I assume anything before 1 hour is too cold, but that is just a guess.

The ferrosilicon definitely gives the metal surface sort of a rainbow sheen, and seems to improve fluidity.

I have an optical iron pyrometer, but it is tricky to use, and I am not sure if I am getting accurate readings.
Bottom line is that it does not matter what a pyrometer reads, the oil burner seems to reach a peak temperature, and then does not seem to add any additonal superheat, so what you get at the end of an hour is probably the maximum achievable temperature with an oil burnrer, and is the best one can get without resorting to induction melting.

I do notice a significant amount of sparks flying out of the lid opening if I continue to operate the burner after one hour.
I presume the metal is starting to burn off, or something.

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[vtsteam]

@CI for pouring temp I go by whether a 1/4" round steel stir rod comes out shiny pointed, vs. clumped with melt.

The steel stiring rod is an interesting method.

One of many tips from Terry Aspin's two little paperback books.

[CI]

When melting aluminum, one can watch for the meniscus to disappear, and that is a good pour temperature that produces an excellent surface finish.

With iron, you are basically trying to look into a 2,500 F (+) output from a leaf blower, and I can only look into the lid opening by using a refrigerator shelf.
Even then, it is a very hot affair.
I can open the furnace and see the melt better, but then one is exposed to the full radiance of the furnace walls and the crucible, and that gets really hot, really fast.

I have photographed cupola/cupolet pours, and the local folks use a synthetic ladle, which really keeps the iron temperature high for a very long time.
The colors/swirls/patterns in the pouring melt are interesting, as is all the action that takes place as the metal is in the process of solidifying, such as the "marching ants", which is some sort of little particles on the surface that seem to swim around in circles just before the metal solidifies.

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[airmodel]

Perhaps measuring sulphur content would be helpful, but I will be using the same treatment regardless of what iron scrap I use to make ductile iron.

I found a link as to how much sulphur should be in cast iron when making ductile iron, it is super low.
https://www.google.com/search?client=firefox-b-d&sca_esv=e3694993e1cbb5c3&sxsrf=AE3TifPOECOYVJ6-FnKuhjo-iWio_6-vdw:1756428215244&q=Nodular+cast+iron+composition&sa=X&ved=2ahUKEwj7iN_-5K6PAxVq-zgGHUnyE6kQ1QJ6BAhHEAE&biw=1920&bih=947&dpr=1#vhid=oSVpF9m9MWQh6M&vssid=_U_iwaN6NPJ-hseMP1bal6Q8_38

[airmodel]

Click onto the images below to see how much sulphur is in ductile iron.

[CI]

This website mentions a very low amount of sulphur.
That is what a supplier told me, "The amount of sulphur must be very low to make ductile iron".

https://www.sciencedirect.com/topics/materials-science/nodular-iron

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[CI]

Info from another website:

https://lobenhofer.com/Tensile%20Properties/effect_of_elements_in_gray.htm

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[crueby]

I'm always amazed at the chemistry/physics of alloys, and how they figured out recipes over the years! Probably a lot of genius mixed with some happy accidents in melting.

[airmodel]

In the second site it mentions that copper is a STRENGTHENER for cast iron so that is the reason why copper is in all the rotors samples that were analysed.