[TheForge] To ring or not to ring - chilled face

[Demon Buddha]

Hochewa at aol.com wrote:
>  
> To All,
> When melting iron to make a gray iron casting, you keep the silicon up a  
> little to make sure that the carbon comes out as flakes when the casting cools  
> slowly.  If you keep the silicon low in the iron and essentially cast it  
> against another block of iron, the cooling rate at the iron-iron interface is  very 
> fast.  The combination of low silicon and rapid cooling creates a  columnar 
> layer of iron carbide crystals perpendicular to the surface of the  casting.  
> The resultant material is VERY hard and wear resistant.  It  is not very 
> ductile but you have the rest of the casting to support it.  A  lot of big mill 
> rolls are "duplex" cast with a chilled shell for the working  surface and a 
> relatively ductile core.

	Some of the cast iron bar that I have dug from the water (round 
section), when proken, reveals a perfect radially oriented grain.  Would 
these have been cast, say, in an iron mold?