Effect of weld metal ferrite content on mechanical properties and stress corrosion cracking resistance in 22 Cr 5 Ni duplex stainless steel
Abstract
Welded 22 Cr 5 Ni duplex stainless steel is often used for chloride-containing environments and sour service applications. Chloride stress corrosion cracking (CSCC) during service poses a threat to the service life of the weldment. Yield strength and resistance to CSCC are considered to depend on the weld metal ferrite content, which is variously required to be 30 to 60%, 30 to 70 ferrite number, 35 to 75%, etc. Accordingly, the present work has been carried out in collaboration with a filler metal manufacturer to investigate the research gap pertaining to minimum ferrite content to obtain the required minimum weld metal yield strength and resistance to CSCC. In this study, 22 Cr 5 Ni weldments with weld metal ferrite content in the range of 14% to 30%, or 20 to 40 ferrite number, obtained by increasing the filler metal nickel content above the normal 9%, have been prepared and investigated. It was found that yield strength and tensile strength requirements of base metal and filler metal classifications were exceeded at all ferrite levels investigated and that no CSCC was observed after 1000-h exposure in the ASTM G 123 boiling 25% sodium chloride test.
Keywords
Duplex stainless steel Shielded metal arc welding Ferrite content Ferrite number Chloride stress corrosion cracking Weld metal yield strengthNotes
Acknowledgments
Sincere thanks are extended to Mr. Umesh Agarwal, CEO, Ms. GEE Ltd., Kalyan (West) Thane Mumbai, India, for providing especially formulated SMAW electrodes, on complimentary basis, to achieve the objectives of this research program. Also, sincere thanks are extended to Mr. Fredrik Prabhu, Sr. Manager, ITW India Pvt. Ltd. for giving permission for utilizing welding equipment and for technical guidance and resource support by his welding engineer, Mr. Subhash Das, for arranging the resource facility of the weld test coupons preparation.
Funding information
The authors would like to express their appreciation for financial support provided by GUJCOST-DST under Minor Research Project Scheme award of Research grant (2014-15.) Ref. GUJCOST Letter Dated 30th March 2015.
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