Failure Analysis of AISI-304 Stainless Steel Styrene Storage Tank |
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Authors: | Muhammad Sajid Ali Asghar Fawad Tariq Ashraf Ali |
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Affiliation: | (1) Department of Materials Engineering, NED University of Engineering and Technology, Karachi, 75270, Pakistan |
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Abstract: | This paper presents the failure analysis of AISI-304 stainless steel tank that was fabricated by welding and used for the
storage of styrene monomers. After about 13 years of satisfactory operation, significant cracking was observed adjacent to
the weld joints and in base plate near tank foundation. Weld repair was by shielded gas arc welding using AISI 308 stainless
steel filler wire. The failed base plate was replaced with the new AISI 304 base plate of same thickness. After a short period
of time, seepage was observed along the weld bead. Upon nondestructive testing cracks were found in the heat-affected zone
and in the base plate. The failure investigation was carried out on welded and base plate samples using spectroscopy, optical
and scanning electron microscopy, fractography, SEM–EDS analysis, microhardness measurements, tensile and impact testing.
The results revealed transgranular cracks in the HAZ and base plate, and the failure was attributed due to stress corrosion
cracking. Cracks initiated as a result of combined action of stresses developed during welding and the presence of a chloride
containing environment due to seawater. It was further observed that improper welding parameters were employed for weld repair
which resulted in sensitization of the structure and postweld heat treatment to remove weld sensitization and minimize the
residual stresses was not done. |
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