51315-5811-Centrifugally Cast 25% Cr Superduplex Steel for Solid CRA Line Pipe

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Product Number: 51315-5811-SG

ISBN: 5811 2015 CP

Author: Shankar Venkataraman

Publication Date: 2015

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Duplex stainless steel alloys are widely used by the upstream oil and gas industry for line pipe applications because of their attractive combination of mechanical and corrosion properties. Among the various duplex grades available the superduplex grades are gaining wider acceptance because of increased strength and corrosion resistance. Line pipes of duplex materials are conventionally made of seamless or longitudinally welded pipes supplied in the wrought form. An alternative process for the manufacture of a seamless pipe is the centrifugal casting process. This process allows extreme flexibility in terms of the pipes to bemanufactured on a customized basis like diameter wall thickness and alloy composition. In this contribution the development of centrifugally cast 25% Cr superduplex alloy line pipes of 25 mm wall thickness and corresponding to a modification of the UNS1 S32750 composition has been reported. Mechanical testing corrosion testing and microstructural control of these pipes has been done and the properties achieved are compared with those necessary as per currently used industry standards. Detailed microstructural studies have been also carried out on the as-cast state and the heat treated state (solution annealed condition) using high resolution scanning electron microscopy (HRSEM) coupled with energy dispersive x-ray spectroscopy (EDS) analysis to understand the structure-property relationship. It will be shown that the centrifugally cast superduplex alloy meets the property requirements in terms of microstructure mechanical properties and corrosion resistance.1 Unified Numbering System for Metals and Alloys (UNS). UNS Numbers are listed in Metals and Alloys in the Unified Numbering System 12th Edition 2012 ASTM International 100 Barr Harbor Drive PO Box C700 West Conshohocken PA.