values. In view of this consideration, the CaF2-CaO-SiO2 type electrodes should be recommended for welding 9% Ni steel. Conclusions The nickel-based alloy covered electrodes (in accordance with the ENi- CrFe-9 Standard) with two different types of flux coatings were investigated in terms of their weldability, weld quality, mass transfer, microstructure, and mechanical properties. According to the experimental results, the following conclusions could be made: 1) In comparison, the strong basic CaF2-CaO-SiO2 type exhibited a larger deposition rate, smaller spatter loss and fumes, and better slag fluidity that resulted in a wider weld bead but smaller penetration. The alkalescent TiO2-SiO2-SrO type exhibited better slag detachability. 2) The mass transfer coefficients (from the covered electrode to the deposited metal) of Ni, Cr, Fe, Mo, W, and Mn of the CaF2-CaO-SiO2 type were evidently larger than that of the TiO2-SiO2-SrO type, but that of Nb and Si were in a reverse manner. The metals exhibited the larger mass transfer coefficients in the strong basic slag system if they could form basic oxides. In contrast, the elements exhibited the smaller mass transfer coefficients in the strong basic slag system if they could form acidic oxides. In addition, the impurities S, P, and O were in the relatively lower levels in the deposited metals of the CaF2-CaO-SiO2 type electrodes because of the higher contents of CaF2 and CaO in the slag. However, the C behaved differently due to the higher contents of CaCO3 in the CaF2-CaO-SiO2 type flux coating. 3) The as-solidified microstructures of the deposited metals of the two types of electrodes were very similar. The equilibrium distribution coefficients of Ni, Fe, and Cr were larger than one, while that of Mo, Mn, and Nb were less than one. In particular, that of Nb was only 0.43 (for CaF2-CaO-SiO2 type) or 0.37 (for TiO2-SiO2-SrO type). These findings were very similar to those observed in other nickel-based alloys. 4) The tensile properties of the deposited metals of the two types of electrodes at room temperature were very close. The Charpy impact values at 77 K for the CaF2-CaO-SiO2 type were in the range of 81–83 J, but that for the TiO2-SiO2-SrO type were in the range of 66–70 J. WELDING RESEARCH This work was supported by the Ministry of Industry and Information Technology of China under the project of LNG shipbuilding. 1. Tetsuo, M. 2013. IEEI e-newsletter 16(19). 2. Abd Ei Fattah, M. K., and Mohamed, A. G. 2013. Mater. Sci. Appl. 4: 198–204. 3. Strife, J. R., and Passoja, E. 1980. Metall. Trans. A 11: 1341–1350. 4. Nippes, E. F., and Balaguer, J. P. 1986. A study of the weld heat-affected zone toughness of 9% nickel steel. Welding Journal 65(9): 237-s to 243-s. 5. Syn, C. K., Jin, S., and Morris, J. W. Jr. 1976. Metall. Trans. A 7: 1827–1832. 6. Avery, R. E., and Parsons, D. 1995. Welding stainless and 9% nickel steel cryogenic vessels. Welding Journal 74(11): 45–50. 7. Zhou, Z. 1996. Welding Metallurgy (Metal Weldability). China Machine Press, Beijing. 8. Qin, R., and He, G. 2013. Metall. Mater. Trans. A 44: 1475–1484. 9. Duan, Z., Qin, R., and He, G. 2014. Metall. Mater. Trans. A 45: 843–853. 10. Qin, R., and He, G. 2014. Inter. J. Heat Mass. Transfer 78: 1095–1104. 11. Qin, R., and He, G. 2015. Carburization phenomenon of ENiCrFe-7 nickelbased alloy covered electrode. Welding Journal 94(3): 83-s to 90-s. 12. Zhang, Q., Wu, X., and Bo, H. 2002. The Development Theory and Technology of Welding Material. Metallurgical Industry Press, Beijing. 13. Zhang, W. 1999. Welding Metallurgy (Fundamental). China Machine Press, Beijing. 14. Chen, J. H., Sun, Z. C., and Fan, D. 1996. Study on the mechanism of spatter produced by basic welding electrodes. Welding Journal 75(10): 311-s to 316-s. 15. Butler, C. A., and Jackson, C. E. 1967. Submerged arc welding characteristics of the CaO-TiO2 system. Welding Journal 46(10): 448-s to 456-s. 16. Schwemmer, D. D., Olson, D. L., and Williamson, D. L. 1979. The relationship of weld penetration to the weld flux. Welding Journal 58(5): 153-s to 160-s. 17. Baune, E., Bonnet, C., and Liu, S. 2000. Reconsidering the basicity of a FCAW consumable – Part 1: Solidified slag composition of a FCAW consumable as a basicity indicator. Welding Journal 79(3): 57-s to 65-s. 18. Sham, K., and Liu, S. 2014. Flux- DECEMBER 2016 / WELDING JOURNAL 477-s Fig. 11 — Fracture morphologies of the impact specimens: A and C — CaF2CaOSiO2 type; B and D — TiO2CaF2SiO2 type. A C B D Acknowledgments References
Welding Journal | December 2016
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