Trans- Granular Stress Corrosion in partially fabricated austenitic stainless steel items and their re-conditioning to make them suitable for balance fabrication

摘要

Fabrication of some of the items using austenitic stainless steel material as per ASME SA 240 type - 304L was started and was to be stopped due to unavoidable circumstances. Many of these Items were in machined, formed and welded condition. These partially fabricated items were stored after applying peelable paint coating on entire surface of on all items and were covered with tarpaulin and were stored in open yard store. These items were kept in store for 5 to 6 years. The storage yard was near to the sea as well as next to petrochemical industry. Sub assemblies and items had seen different extreme weathers conditions, saline and corrosive atmosphere for all these years of storage time and were subjected to contamination. To assess the health of material, preliminary cleaning, investigations by various NDEs like Visible Dye Penetrant & Fluorescent Dye Penetrant tests, in-situ metallographic examinations and weld-ability tests, were conducted on these items. Linear and branch type indications were observed in dye penetrant tests in base material / HAZ / Weld seams. Upon further investigation it was observed that some of the areas are attacked by TGSCC as well. After thorough investigation and discussion with team of metallurgists, reconditioning plans were chalked out to remove these indications to ensure that material is free from contamination and becomes suitable for use. Re-conditioning plan was successfully implemented and items could be made suitable for balance fabrication work.