SPHEROIDAL GRAPHITE CAST IRON PIPE, PREPARATION PROCESS OF SPHEROIDAL GRAPHITE CAST IRON PIPE FOR URBAN HIGH-PRESSURE GAS PIPELINE, AND SPHEROIDAL GRAPHITE CAST IRON PIPE FOR URBAN HIGH-PRESSURE GAS PIPELINE

摘要

Disclosed is a preparation process of a spheroidal graphite cast iron pipe, comprising the steps of molten iron preparation, nodulizing treatment, centrifugal casting by a hot die coating method, etc. The matrix structure of the spheroidal graphite cast iron pipe consists mainly of ferrite, contains no free cementite, and has low pearlescent content; the elongation rate of the matrix structure is greater than 18% and the tensile strength thereof is high; there are no casting defects, such as slag holes and sand holes, and the structure is airtight. Further provided is a spheroidal graphite cast iron pipe for urban high-pressure gas pipelines and a preparation process thereof. The spheroidal graphite cast iron pipe for urban high-pressure gas pipelines has no casting defects, such as slag holes, subsurface porosity, sand holes, short run, cold shut and lamination, shrinkage cavities, shrinkage porosity, etc., and has uniform wall thickness, a high density of pipe body structure, and is air tight. The invention satisfies the quality requirements for laying urban gas pipelines, is suitable for laying high-pressure and sub-high-pressure urban gas pipelines with a transporting pressure of 0.4-4.0 MPa, and if required, can also be used for gas pipelines of no more than 6.0 MPa.