Ductile Iron Problem

[gdodd]

Ductile Iron Problem

We have found a cast iron part containing areas of flake graphite but mostly compacted graphite and spheroidal graphite where normally it would be 100% spheroidal graphite in a ferrite matrix. Understandably the properties such as hardness and ductility have been reduced dramaticly.
The part comes from a batch which had been checked for magnesium during casting (0.45%) and all remaining elements analysed indicate cast batch conforms to specification. As yet the affected part has not been analysed.
During cast ing the molten iron is poured from a ladle into a spoon which bottom pours into the mould containing two cavities.
According to records the iron conforms to specification before it is poured into the spoon.
Is there any way the refractory lining, coke cans or other contaminant could cause magnesium depletion between exiting the pouring ladle to entering the mould?
The problem does not appear to have affected the remaining batch code of 1200 castings.

Thanks in advance

 

[arunmrao]

The desired levels ofresidual Mg should be 0.045% and not 0.45%.Any delay in pouring after the Mg treatment could lead to Mg fading phenomeno. Normally within 5 minutes of treatment the metal should be poured. I do not think the factors mentioned by you would influence Mg fading. Hope this helps.

 

[gdodd]

Thanks for the quick response
Sorry, decimal point is in the wrong position, above should read 0.045%Mg.

Regards

 

just the other day our mg was dropping at a very fast rate in our induction furnace i was a furnace tendor for about a year and i noticed that when you super heat your mag will burn off faster than normal also i am not sure how you treat your iron we treat ours in 10,000 lb batches in george fisher converters mounted on 65,000 royal trucks if the mag chambers are full of slag you will not get the mg recovery your lookin for. pay attention where your sulfer levels ar the higher your sulfer level is the more mag you will need.

 

[gdodd]

Thanks for your responses
Problem was in fact due to a time delay causing overheating a residual (less than desired) quantity of molten metal before recharging. It was confined to the few castings produced when pouring re-commenced.