... state-owned enterprises 1.The pipes standard in accordance with ISO2531,Class K9, L=6000mm,2.T ... 140After annealing,the microstructure of ductile cast iron pipes is ferrite and a little pearlite,possessing ... properties.Production process flow of ductile cast iron pipes Pipe hoisting Take precaution of handling pipe ... on the space between two layers of pipes, at last pipes are fixed up with steel cable ...