Hello,
I desperately need the opinion of any ductile iron metallurgists that subscribe to CR4. We took a small casting that is supposed to be annealed ASTM A395 - which requires a minimum % nodularity of 90%. The casting can be held in the palm of one's hand/weighs about 10 lbs & cross section only varies from about 3/8" to 5/8". We cut 2 specimens & sent out to 2 labs (and later sent specimen from Lab #1 to our casting supplier). Here are the results:
Specimen #1: Lab #1 says 50% nodularity based on ASTM Wall Chart.
Specimen #2 (cut about 3" away from Specimen #1): Lab #2 tried to scan with computer instead of using ASTM Wall Chart & couldn't find enough nodules to reach a conclusion (they say maybe 3% nodularity based on a glance w/naked eye).
Specimen #3 (cut right next to Specimen #2): Our casting supplier says their computer gave an average nodularity of "82.1%".
Specimen #1 was then sent back by Lab 1 & then sent to our casting supplier: Their computer scanner says overage nodularity is not 50% but is "73.2%".
The microphotograph of Specimen #1 is shown below:
So my questions are:
1. How can an annealed ASTM A395 casting have no nodularity on one specimen (#2) & 82% from an adjacently cut specimen (i.e. #3)?
2. How is the casting supplier's computer obtaining 73% nodularity from Specimen #1, when Lab 1 is only getting 50% based on using ASTM Wall Chart?
Thanks in advance for any expert opinions.
ASTM A395 Annealed Ductile Iron Casting - "wild" % Nodularity Values
