... ,Zinc coat,bitumen layer 4.Pull strength: >420MPa Ductile iron pipe Material:Ductile iron (1) The standard:ISO2531-1998,EN545-2006/EN598 ... easy connection.(7) High strength,lighter than gray iron,good corrosion resistance,small flow resistance,easy fixing,long ... . Production Procedure:(I) Smelting and Nodulizing(II) Centrifugal Casting(III) Annealing Treatment(IV) Zinc Spraying for Corrosion Resistance ...