wgbiii,
I would guess that it is at least closer ( properties of the metal )to cast iron than cast steel. It looks like it broke without bending first, which is why I would assume that. As you know and as radman1 said, it is going to be somewhat expensive to buy new. I think that it is also going to be quite expensive to have welded especially if it's cast iron. When you weld cast iron, you have to either heat up the part around 300-350 degrees ( if I remember correctly ) and weld it before it cools off too much. Obviously the part would have to be removed from the tractor to do it without hurting anything in the process.The other way you have to weld cast iron is by " cold welding" which means to weld a VERY small bead and stop and take a little break, then small bead and stop again etc. until it's done. The more I think about it, I think that it would be cheaper to buy a new part, due to high labor costs at the welding shop. It isn't a five minute job as you probably already know. Good luck on whatever you decide!
Daryle.