Requesting Advice on Drying/Warming Green Sand Molds Prior to Pouring Cast Iron

One observation I have recently made is that adding ferrosilicon seems to increase shrinkage issues in grey cast iron. I have a casting that I have made many times over the last few months. To improve softness of the casting I have been adding ferrosilicon to my melt shortly before pouring (I have read that inoculants like FeSi produce their desired effect for only 10-20 minutes and then fade from time of addition) in amounts of 14-16 ounces for a 50 pound pour. I suspect that may be excessive as I am seeing shrinkage to a greater degree than when using only 2 ounces. To counter this, I have added risers to the runner and that seems to have solved the problem.

On the other hand my castings have been softer (good for this application) when inoculated at the higher rate (prior ratio was 2 ounces in 50 pounds). So, now I am in search of the optimal inoculation rate. I am going to try more like 8 ounces an see how that works.

I am mentioning this as a caution that too much FeSi may cause increased shrinkage defects. So, if you are seeing such defects, at least consider whether you might be adding too much silicon.

I would like to hear from anyone who has input on the subject as I am still trying to figure out optimal inoculation rates.

Denis