Shrinkage in Large ductile iron casting 2

[Hercules28]

Dear all,

I have a large ductile iron casting ~250lbs with a wall thickness of 1 inch in resin bonded sand.
I got shrinkage issues that I can't seem to get rid off.

Chemistry :
C: 3.82
Si: 2.65
Mn .449
S 0.0108
Cu 0.0765
Mg 0.0319
Cr 0.0262

Pour Temp is 2590F.

Nodularity is great.

Any ideas?

 

[arunmrao]

250 lbs and 1inch wall thickness cannot be classified as heavy section castings. The C.E of the D.I casting is 4.7,you may reduce the C.E to 4.3 -4.4 . Also the pouring temperature is 1421C, you may reduce the C.E to 1390-1400C or lower. Also if the shrinkage is in thick section of the casting, you may provide chills . I hope the resin sand mold is rigid enough to withstand the graphitization pressure during solidification.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[Hercules28]

Arunmao,

I actually tried increasing the C to improve the expansion. That didn't work.
And then I tried to increase pouring T, reduce pouring t to fill it fast before graphitization starts.
I also tried pouring it slow... that didn't work either.
The casting is a pipe and there is shrink along the parting line. Looks more like interdendritic rather than large cavities.

 

[arunmrao]

Did you consider pouring the pipe vertically? Simple and uniform shapes are more challenging ?

You have tried increasing C.E ,which only increases expansion pressure. I hope the molds are rigid, and that there is no mold swell.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[Hercules28]

Actually I was thinking of the same thing. That way solidification may be somewhat directional.

It may be hard to keep the mold together though as it is impossible to move the parting line. So I am not sure.. probably I d need to strap it.

I also thought of using a copper pipe inside the core to act as a chiller..?

 

[arunmrao]

Ue a hollow core with zircon sand and let the core be made of inorganic binder. It will produce a good chilling effect. A resin core and mold generate heat delaying skin formation on the casting.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year