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Strain ageing in fusion-bonded epoxy coated pipeline steel

Grant


Scheme


  • R&D Fund

Abstract


  • The most common corrosion protection coating used for natural gas transmission pipelines is fusion bonded epoxy (FBE) which is applied to induction heated pipe at about 250oC. The heating process causes strain ageing, a metallurgical phenomenon whereby the yield strength and the yield strength to ultimate tensile strength ratio (Y/T) are increased as a result of thermally activated diffusion of interstitial elements carbon (C) and nitrogen (N) to dislocation sites resulting from cold forming of the pipe. In a current order of line pipe manufactured by Baosteel for the largest Australian pipeline owner APA Group, the specified maximum value of Y/T in the as-manufactured condition before coating is 0.90, and the average actual value is 0.85, well within the acceptable limit. However, after coating, the average value is 0.95 and the maximum value is 0.99, and this is causing concern to APA Group and other Australian customers of Baosteel. This project aims to conduct novel research to understand and optimise strain ageing effects and their structural consequences in pipeline steels, and to further Baosteel¿s longer term, strategic development and business activities by conducting the research in collaboration with Baosteel's Australian customers within the ambit of the Energy Pipelines CRC.

Sponsor Award Id


  • BA14002

Local Award Id


  • 117943

Scheme


  • R&D Fund

Abstract


  • The most common corrosion protection coating used for natural gas transmission pipelines is fusion bonded epoxy (FBE) which is applied to induction heated pipe at about 250oC. The heating process causes strain ageing, a metallurgical phenomenon whereby the yield strength and the yield strength to ultimate tensile strength ratio (Y/T) are increased as a result of thermally activated diffusion of interstitial elements carbon (C) and nitrogen (N) to dislocation sites resulting from cold forming of the pipe. In a current order of line pipe manufactured by Baosteel for the largest Australian pipeline owner APA Group, the specified maximum value of Y/T in the as-manufactured condition before coating is 0.90, and the average actual value is 0.85, well within the acceptable limit. However, after coating, the average value is 0.95 and the maximum value is 0.99, and this is causing concern to APA Group and other Australian customers of Baosteel. This project aims to conduct novel research to understand and optimise strain ageing effects and their structural consequences in pipeline steels, and to further Baosteel¿s longer term, strategic development and business activities by conducting the research in collaboration with Baosteel's Australian customers within the ambit of the Energy Pipelines CRC.

Sponsor Award Id


  • BA14002

Local Award Id


  • 117943