FCAW Prosesi ile Yapısal Çeliklerin Birleştirilmesinde Isı Girdisinin Mikro Yapı ve Mekanik Özelliklere Etkisi

Özlü kaynak telleri, yapısal ve boru hattı kaynağı, gemi yapımı, açık deniz inşaatları, petrokimya ve enerji üretim endüstrilerinde oldukça yaygın bir şekilde kullanılmaktadır. Çok pasolu kaynaklarda yüksek ısı girdileri, daha kısa üretim sürelerine neden olurken, kaynaklı birleştirmenin özelliklerini de önemli ölçüde değiştirmektedir. Bu çalışmada, yapısal çeliklerin kaynaklı birleştirmelerde ısı girdisinin kaynak mikroyapısı, sertlik, çekme özellikleri ve darbe tokluğu üzerindeki etkisini belirlemek için değişen ısı girdileriyle (0,56-2,52 kJ/mm arasında) robotik özlü özlü ark kaynağı yapılmıştır. Sonuçlar, ısı girdisinin 2.52’den 0.56 kJ/mm’e düşmesi ile mikro yapının genelinin poligonal ferritten asiküler ferrite dönüştüğünü göstermiştir. Bu da akma mukavemeti, çekme mukavemeti ve sertlik değerlerinde sırasıyla %56, %37 ve %47'lik bir artışa neden olurken, uzama ve Charpy darbe testi sonuçlarında sırasıyla %30 ve %15'lik bir düşüşe neden olmuştur. Ayrıca, kaynaklı birleştirmelerin tümünde -50 °C'lik test sıcaklığında bile istenen 47 J değerinden oldukça yüksek tokluk değerleri elde edilmiştir. Son olarak, AWS A5.20 standardının minimum gereksinimleri ve uygulamalardaki beklentiler dikkate alındığında optimum sonuçların 1,26 kJ/mm ısı girdisi ile elde edildiği sonucuna varılmıştır.

Anahtar Kelimeler:

Robotik MAG kaynağı, Özlü kaynak teli, Yapısal çelik birleştirmeleri, Mikro yapı karakterizasyonu, Mekanik özellikler, Isı girdisi

HEAT INPUT EFFECT OF THE FCAW PROCESS ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF STRUCTURAL STEEL JOINTS

Flux-cored wires are commonly used in structural and pipeline welding, shipbuilding, offshore constructions, and petrochemical and power generation industries. The higher heat inputs in the multipass welding result in shorter production time while considerably changing the properties of the welded joint. In this study, robotic flux cored arc welding with varying heat inputs (between 0.56-2.52 kJ/mm) was performed to determine the effect of heat input on weld microstructure, hardness, tensile properties, and impact toughness in the structural steel joints. Results exhibited that decrease in heat input from 2.52 to 0.56 kJ/mm changed the majority of the microstructure from polygonal ferrite to acicular ferrite. Furthermore, this increased by 56%, 37%, and 47% in yield strength, tensile strength, and hardness values, respectively, while decreasing by 30% and 15% in elongation and Charpy impact test results, respectively. Moreover, all welded joints displayed a satisfying toughness value higher than the requested value of 47 J, even at the test temperature of -50 °C. Finally, it can be concluded that the optimum results were obtained with a heat input of 1.26 kJ/mm, considering the minimum requirements of the AWS A5.20 standard and the expectations in applications.

Keywords:

Robotic MAG welding, Flux-cored welding wire, Stuctural steel joints, Microstructural characterization, Mechanical properties, Heat input,

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1. Bang, K., Park, C., Jeong, H. (2014) Low heat input welding to improve impact toughness of multipass FCAW-S weld metal, Journal of Ocean Engineering and Technology, 28(6), 540-545. Doi: 10.5574/KSOE.2014.28.6.540
2. Chinakhov, D. A., Chinakhova, E. D., Sapozhkov, A. S. (2016) Manganese content control in weld metal during MAG welding, IOP Conf. Series: Materials Science and Engineering, 142, 012026. Doi: 10.1088/1757-899X/142/1/012026
3. Evans, G. M. (1982) The effect of heat-input on the microstructure and properties of C-Mn all-weld-metal deposits, Welding Journal, 61(04), 125-132, 1982.
4. Evans, G. M. (1991) The Effect of aluminium in shielded metal arc C-Mn steel multipass deposits, Welding Research Supplement, 32–40, 1991.
5. Gürol, U., Dilibal, S., Turgut, B., Koçak, M. (2022a) Characterization of a low-alloy steel component produced with wire arc additive manufacturing process using metal-cored wire, Materials Testing, 64(6), 755–767. Doi: 10.1515/mt-2021-2155
6. Gürol, U., Çoban, O., Coşar, İ., Koçak, M. (2022b) Effect of the notch location on the Charpy-V toughness results for robotic flux-cored arc welded multipass joints, Materials Testing, Doi: 10.1515/mt- 2022-0113
7. İpekoğlu, G., Küçükömeroğlu, T., Aktarer S. M., Sekban, D. M., Çam, G. (2018) Microstructural characterization and mechanical properties of St37/St52 plates joined by friction stir welding, Journal of Science and Engineering, 20(59), 471-480, Doi: 10.21205/deufmd. 2018205937
8. Jorge J. C. F., Souza L. F. G., Araújo L. S., Bott I. S., Mendes, M. C., Evans, G. M. (2019) Microstructure and toughness of C-Mn steel submerged-arc weld deposits, with and without titanium addition, IIW Annual Assembly, Bratislava, Chech Republica, IIW Doc. IX-2674-19.
9. Küçükömeroğlu, T., Aktarer, S. M., İpekoğlu, G, Çam, G. (2018) Mechanical properties of friction stir welded St 37 and St 44 steel joints, Materials Testing, 60 (12), 1163-1170. Doi: 10.3139/120.111266
10. Ling, K. H., Fuh, Y. K., Kuo, T. C., Xun-Tu, S. (2015) Effect of welding sequence of a multi-pass temper bead in gas-shielded flux-cored arc welding process: hardness, microstructure, and impact toughness analysis, International Journal of Advanced Manufacturing Technology, 81, 1033–1046. Doi: 10.1007/s00170-015-7277-x
11. Muda, W. S. H., Nasir, N. S. M, Mamat, S., Jamian, S. (2015) Effect of welding heat input on microstructure and mechanical properties at coarse grain heat affected zone of ABS grade a steel, ARPN Journal of Engineering and Applied Sciences, 10(20), 9487-9495
12. Pitrun, M., Nolan, D., Dunne, D. (2004) Diffusible hydrogen content in rutile flux-cored arc welds as a function of the welding parameters, Welding in the World, 48, 2–13. Doi:10.1007/BF03266408
13. Schönmaier, H., Krein, R., Schmitz-Niederau, M., Schnitzer R. (2021) Influence of the heat input on the dendritic solidification structure and the mechanical properties of 2.25Cr-1Mo-0.25V submerged-arc weld metal. Journal of Materials Engineering and Performance, 30, 7138–7151. Doi: 10.1007/s11665-021-05922-x
14. Viano, D. M., Ahmet, N. U., Schumann, G. O. (2000) Influence of heat input and travel speed on microstructure and mechanical properties of double tandem submerged arc high strength low alloy steel weldments, Science and Technology of Welding and Joining, 5(1), 26-34. Doi: 10.1179/stw.2000.5.1.26
15. Wang, H. H., Tong, Z., Evans, G. M. (2018) Systematic role of Mn and Ti in microstructure and impact toughness of reheated C-Mn weld metals, Proc. of the Intermediate Meeting of the IIW Sub. Commission 2C, Genoa, IIW Doc. II-549-18.
16. Weman, K. and Linden, G. (2006) MIG Welding Guide, Woodhead Publishing Limited, Cambridge
17. Yang, L., Wang, Y., Sun, T., Huang, Y., Zhai, Y., He, T. (2020) Microstructure and mechanical properties of FCTIG-welded DH36 steel with rutile-type and basic-type flux cored wires, Journal of Materials Processing Technology, 275, 116363. Doi: 10.1016/j.jmatprotec.2019.116363
18. Zhang, Y., Jia, C., Zhao, B., Hu, J., Wu, C. (2016) Heat input and metal transfer influences on the weld geometry and microstructure during underwater wet FCAW, Journal of Materials Processing Technology, 238, 373-382, Doi: 10.1016/j.jmatprotec.2016.07.024
19. Zhou, P., Wang, B., Wang, L., Hu, Y., Zhou, L. (2018) Effect of welding heat input on grain boundary evolution and toughness properties in CGHAZ of X90 pipeline steel, Materials Science and Engineering: A, 722, 112-121. Doi: 10.1016/j.msea.2018.03.029