It may not be just lack of proper pre-heat. It might also be due to rapid cooling of the weld. Different metals/alloys dissipate heat at different rates. Cast Iron verses Aluminum verses A992 Steel. The Cast Iron must be allowed to cool very slowly compared to the other two. Although I have not worked with your particular alloy, it would not suprise me to find out that it required post-heat treatment or controlled cooling. I'm interested to find out the answer to your question as well.

Norm