Tozaltı Ark Kaynağı ile Kaynaklanmış X70M Çeliklerinin Mikro Yapı ve Mekanik Özelliklerinin İncelenmesi

Year 2025, Volume: 12 Issue: 2, 547 - 554, 30.11.2025

Kelani G. K. Elattousi , Şenol Avcı , Ozkan Kucuk

https://doi.org/10.35193/bseufbd.1665341

Abstract

Bu çalışmada, petrol boru hatlarında kullanılan X70M PSL 2 (API 5L) çeliği, tozaltı ark kaynağı yöntemiyle kaynatılmıştır. Kaynak dikişi ve ITAB, optik mikroskop, taramalı elektron mikroskobu (SEM), çekme deneyi, sertlik deneyi ve Charpy darbe deneyi yöntemleri ile karakterize edilmiştir. Optik inceleme sonucunda yapı içerisinde herhangi bir kaynak hatasının oluşmadığı görülmüştür. Kaynak bölgesi, ana metal ve ITAB olarak belirgindir ve kaynak metalinde sütunsal tane büyümesi gerçekleşmiştir. SEM çalışmasında ana malzemenin ferrit (açısal ferrit, poligonal ferrit) tanelerinden, ITAB bölgesinin daha iri tanelerden ve kaynak metalinin ise sütunsal ince ferrit plakalarından oluştuğu görülmüştür. Çekme deneyi sonucunda, ana malzemenin çekme dayanımının yaklaşık 648 MPa, kaynaklı birleştirmenin çekme dayanımının ise yaklaşık 695 MPa olduğu tespit edilmiştir. Elde edilen sonuçlar kaynaklı birleştirmede kopmanın ana malzemede gerçekleştiğini göstermektedir. En yüksek ortalama sertlik değeri 229 HV olarak kaynak metalinde ölçülmüştür. Buna karşın ana malzeme ve ITAB’daki ortalama sertlik değerleri ise sırası ile 218 HV ve 221 HV’dir. Ana malzemede elde edilen ortalama darbe enerjisi değeri 428 J’dür. En düşük darbe enerjisi ise kaynak metalinde elde edilmiştir. Kaynak metalinde elde edilen ortalama darbe enerjisi değeri yaklaşık 94 J’dür. Kaynak metalinden ana malzemeye doğru gidildikçe darbe enerjisindeki artış dikkat çekicidir.

Keywords

Boru Hattı Çelikleri , X70M , Kaynak

Investigation of Microstructure and Mechanical Properties of X70M Steels Welded by Submerged Arc Welding

Abstract

In this study, X70M PSL 2 (API 5L) steel used in oil pipelines was welded by submerged arc welding method. Weld seam and HAZ were characterized by optical microscopy, scanning electron microscopy (SEM), tensile test, hardness test and Charpy impact test methods. As a result of the optical inspection, it was observed that no welding defects had occurred within the structure. The weld zone, base metal, and HAZ are distinct, and columnar grain growth has occurred in the weld metal. In the SEM study, it was observed that the base material consists of ferrite grains (angular ferrite, polygonal ferrite), the HAZ consists of coarser grains, and the weld metal consists of fine columnar ferrite. As a result of the tensile test, it was determined that the tensile strength of the base material is approximately 648 MPa, while the tensile strength of the welded joint is approximately 695 MPa. The obtained results indicate that the fracture in the welded joint occurred in the base material. The highest average hardness value was measured as 229 HV in the weld metal. In contrast, the average hardness values in the base material and HAZ are 218 HV and 221 HV, respectively. The average impact energy value obtained in the base material is 428 J. The lowest impact energy was obtained in the weld metal. The average impact energy value obtained in the weld metal is approximately 94 J. As one moves from the weld metal towards the base material, the increase in impact energy is remarkable.

Keywords

Pipeline Steels , X70M , Welding

References

• Antaki, G. A. (2003). Piping and pipeline engineering: design, construction, maintenance, integrity, and repair. CRC Press.
• Apay, S., Gel, M., & Çil, G. (2018). Tozaltı Kaynak Yöntemi ile Farklı Kaynak Parametreleri Kullanılarak Birleştirilen API X70M PSL2 Malzemelerin Kaynak Bölgesinin İncelenmesi. Duzce University Journal of Science and Technology, 6(4), 714-723.
• Arıkan, M. M., Tütük, R., & Kayalı, E. S. (2019). Effect of Reduction Ratio below Austenite Recrystallization Stop Temperature on Mechanical Properties of an API X70M PSL2 Line Pipe Steel. Sakarya University Journal of Science, 23(5), 972-981.
• Baczynski, G J, Jonas, J J, & Collins, L E. (1999). The influence of rolling practice on notch toughness and texture development in high-strength linepipe. Metall Mater Trans A 30(12), 3045–3054.
• Bain, E. C. Alloying Elements in Steels, ASM, Cleveland, Ohio, USA, 1939. WRC Bulletin, 318.
• Black, J. T., & Kohser, R. A. (2020). DeGarmo's materials and processes in manufacturing. John Wiley & Sons. Hoboken, NJ.
• Carneiro, R. A., Ratnapuli, R. C., & Lins, V. D. F. C. (2003). The influence of chemical composition and microstructure of API linepipe steels on hydrogen induced cracking and sulfide stress corrosion cracking. Materials Science and Engineering: A, 357(1-2), 104-110.
• Çetinkaya, C., Ada, H., & Sezgin, M. (2020). API 5L X70M Çeliklerinin Özlü Telle Ark Kaynak Yöntemiyle Orbital Birleştirilmesinde Metalurjik ve Mekanik Özelliklerinin İncelenmesi. Gazi University Journal of Science Part C: Design and Technology, 8(4), 981-995.
• Chaveriat, P. F., Kim, G. S., Shah, S., & Indacochea, J. E. (1987). Low carbon steel weld metal microstructures: the role of oxygen and manganese. Journal of materials engineering, 9(3), 253-267.
• Goyal, R. K., Singh, A., & Kathayat, T. S. (2020). Solidification Cracking of Longitudinal Submerged Arc Welded Pipes. Journal of Failure Analysis and Prevention, 20(3), 627-633.
• Raoul, J. (2005). Use and application of high-performance steels for steel structures (Vol. 8). Iabse.
• Hu, J., Du, L. X., Xie, H., Dong, F. T., & Misra, R. D. K. (2014). Effect of weld peak temperature on the microstructure, hardness, and transformation kinetics of simulated heat affected zone of hot rolled ultra-low carbon high strength Ti–Mo ferritic steel. Materials & Design, 60, 302-309.
• Hwang, B., Kim, Y. G., Lee, S., Kim, Y. M., Kim, N. J., & Yoo, J. Y. (2005). Effective grain size and charpy impact properties of high-toughness X70 pipeline steels. Metallurgical and materials transactions A, 36(8), 2107-2114.
• Jiao, Z. B., Luan, J. H., Zhang, Z. W., Miller, M. K., & Liu, C. T. (2014). High-strength steels hardened mainly by nanoscale NiAl precipitates. Scripta Materialia, 87, 45-48.
• Jun, H. J., Kang, K. B., & Park, C. G. (2003). Effects of cooling rate and isothermal holding on the precipitation behavior during continuous casting of Nb–Ti bearing HSLA steels. Scripta Materialia, 49(11), 1081-1086.
• Kiefner, J. F., & Clark, E. B. (1996). History of line pipe manufacturing in North America (Vol. 43). American Society of Mechanical Engineers.
• Koo, J. Y., Luton, M. J., Bangaru, N. V., Petkovic, R. A., Fairchild, D. P., Petersen, C. W., ... & Takeuchi, I. (2004). Metallurgical design of ultra high-strength steels for gas pipelines. International Journal of Offshore and Polar Engineering, 14(01).
• Krauss, G., & Thompson, S. W. (1995). Ferritic microstructures in continuously cooled low-and ultralow-carbon steels. ISIJ international, 35(8), 937-945.
• Pande, C. S., & Imam, M. A. (2007). Nucleation and growth kinetics in high strength low carbon ferrous alloys. Materials Science and Engineering: A, 457(1-2), 69-76.
• Ricles, J. M., Sause, R., & Green, P. S. (1998). High-strength steel: implications of material and geometric characteristics on inelastic flexural behavior. Engineering Structures, 20(4-6), 323-335.
• Krasilnikov, N. A., & Sharafutdiniv, A. (2007). High strength and ductility of nanostructured Al-based alloy, prepared by high-pressure technique. Materials Science and Engineering: A, 463(1-2), 74-77.
• Kennedy, J.L. (1984). Oil and Gas Pipeline Fundamentals; U.S. Department of Energy Office of Scientific and Technical Information: OakRidge, TN, USA, 1984.
• American Petroleum Institute. (2000). Specification for Line Pipe: API Specification 5L. American Petroleum Institute.