What is the price of scrap cast iron?
You have two options. One is to sell them to an architectural reclamation dealer and the other is to sell them to a scrap metal dealer. You will find both of them in the yellow pages. 70kgs is not a huge amount for iron so you may need to take it to a scrap metal dealer yourself. If you ask them to collect it, their charges for such a small quantity will seriously reduce the amount that they pay you.