Transmission Electron Microscopy of Longitudinal Double Submerged Arc Weld (LDSAW) of X-120M Steel Line Pipe

Abstract:

This paper deals with the development of submerged arc welding wires for longitudinal double submerged arc welded (LDSAW) line pipe weld through transmission electron microscopy (TEM). The experimental procedure in the paper describes the test coupons preparation for submerged arc welding (SAW) with various combinations of wire and flux with varying level of alloying element. Microstructural characterization by transmission electron microscopy has been carried out to establish the desired microstructure in the weld of LDSAW for manufacturing the API-5L X-120M line pipes. The TEM micrographs for shows the lath type ferrite and bainitic type ferrite with high dislocation density. The lath type ferrite and bainitic type ferrite with high dislocation density also have fine precipitates in the ferrite matrix having orientation relationship. The weld metal suitable for X-120M have the microstructure of mainly bainitic and martensitic with high dislocation density and coarse precipitates in the matrix. The bainitic and martensitic microstructure have excellent fracture toughness down to -20 °C at this strength level (X-120M).

• Periodical: Advanced Materials Research (Volume 585)
• Pages: 460-464
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.585.460
• Online since: November 2012
• Authors: Jai Dev Singh Chandel, Nand Lal Singh
• Keywords: Bainite, LDSAW, TEM, X-120M

References

[1] Widgery D J; High Strength Weld Metal – Routes for Development. – IIW Document II- 1459-02 (II-A-098-02) 2000.

[2] Bhadeshia H K D H, Svensson L E; Model for Boron Effects in Steel Welds. – International Conference on Modeling and control of Joining Processes, Florida, 1993.

[3] Keehan E, Karlsson L, Andren H O, Svensson L E; New Developments with C-Mn-Ni in High Strength Steel Weld Metals-PART-B, Mechanical Properties. – Welding Journal 2006.

[4] Keehan Enda, Karlsson Leif, Murugananth Marimuthu, Andren Hans-Olof, Bhandeshia Harshad; High Strength Steel Weld Metals - Developments with Ni and Mn. – Proceedings of the International Welding Symposium, 2002.

[5] Masahiko Hamada, Shuji Okaguchi, Yu-ich Komizo, Akio Yamamoto, Nobutaki Takahashi, Tomoaki Ikeda, Izumi Takeuchi; The Effect of Boron Addition on the Toughness and Microstructure of Seam Weld Metal. - Pipeline Technology Proceedings, Conference, Ostend, Belgium 2004.

[6] J D Chandel, N L Singh; Characterization of submerged arc welding heat affected zone in X-120M line pipe steel by light microscopy. Journal of Indian Welding Society, March- 2012, Page # 25-35. India.