>"A former Ford employee who worked in the engine foundry during the time 289
>HiPo's were produced was able to shed some light on this ground area. He
>indicated that the molten metal used for higher nodularity castings, such as
>the 289 HiPo crankshaft, had increased amounts of nickel and manganese
>added. After the casting process was completed, the 289 HiPo crankshaft rear
>counterweight was ground smooth so that the higher nodularity content could
>be verified by visual inspection under a microscope. (The grains, or
>nodules, within a specific circle were counted and the number had to meet a
>particular criteria for the metal to be considered of "high nodularity.") No
>other hardness testing was done on 289 HiPo crankshafts with the ground
>smooth counterweight."
>
>
>
I was not at this foundry in the 60's but have been on a few melt decks
before and supplied the metallurgical equipment to count nodules.
Ductile, or nodular iron is made by "inoculation" of the metal with
magnesium during the pour. This desulfurizes the iron and causes the
graphite to form in round nodules as opposed to long flakes. Mechanical
properties are superior. Here is a link to some microstructures.
http://www.metallography.com/technotes/iron/nodular.htm
When there is a pour, a test piece is sent to the lab and it is polished
and then etched to reveal the graphite nodules. The size of the nodules
and the count establish the rating of the melt. Low nodularity and the
castings go back into the ladle for remelt. Nothing you can do.
It is a lot of work to do this and I would be very suprised if Ford used
100% metallugical inspection for a production part. The Hipo crank I had
had a brinell hardness test on a counterweight. While this is a more
manual test that requires a 10x optical measurement, it is fairly quick
for an experienced operator and far more believable that the cranks were
100% brinell tested based upon my foundry experience.
Bob Melusky
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