51312-01547-Material behavior in extreme conditions: X65 corrosion resistance strength and toughness variation

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Product Number: 51312-01547-SG

ISBN: 01547 2012 CP

Author: Roberto Morana

Publication Date: 2012

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Oil and natural gas transporting plants in arctic field (i.e. north America Kashagan Karachaganak) normally operate at temperatures up to 100°C or even more. During the shut down operations in winter time pipelines materials reach very low temperatures (-40°C) and are subjected to a severe environment with high concentration of hydrogen sulphides (5-20%) and to an important step in pressure in the subsequent re-starting operations. Furthermore there is a lack of knowledge assessing material performances in presence of H2S partial pressure up to 20 bar or more. The present work assessed the following issues for X65 linepipe steels: analyze the effect of hydrogen on material strength and toughness at low temperatures. investigate the general corrosion and stress corrosion cracking resistance in extreme conditions with high pressure of H2S looking for a window of applicability. Ductile-brittle transition curve and mechanical properties were evaluated by means of Charpy-V tensile and Crack Tip Opening Displacement (CTOD) methods for as received materials and after exposure to H2S containing environment. Furthermore autoclave exposures of coupons and stressed samples (Four Point Bent Beam FPB) in environment containing elevated values of H2S partial pressure (10 and 16 bars) at different pH (3.5 4.5) were carried out. Key words: linepipes carbon steels mechanical properties pH H2S arctic environments SSC SCC Charpy-V CTOD.