Optimum rotational speed in FSW of copper canisters for nuclear waste

Ajabshiri, Mehrdad; Rezaei, Hasan; Nazari, Ezat; Nozad Golikand, Ahmad

Optimum rotational speed in FSW of copper canisters for nuclear waste

Document Type : Scientific Note

Authors

Mehrdad Ajabshiri

Hasan Rezaei

Ezat Nazari

Ahmad Nozad Golikand

Abstract

The high-level radioactive waste will be encapsulated in copper canisters and stored in a deep repository. High power electron beam welding was the only viable method available at that time for welding thick section copper. In recent years, friction stir welding has been replaced with electron beam welding because of the promotion in mechanical properties and corrosion resistance of copper canisters. FSW is used in solid state, therefore residual stresses produced in the weld is less than that of other welding processes which are performed in the molten state. To obtain optimum rotational speed, FSW was carried out in copper plates with a thickness of 4 mm at a constant speed of 25 mm/minute. The temperature distribution indicated a severe increasing of temperature upon increasing the rotational speed from 900 to 1200 rpm. Also, analysis of the metallographic images showed that the grain size in the nugget zone increases by increasing the rotational speed. Vickers hardness test was conducted on the welded samples and the maximum hardness was obtained at a rotational speed of 900 rpm. Results of tensile tests and their comparison with those of the base metal showed that the maximum strength and minimum elongation are achieved at the same rotational speed.

Keywords

Nuclear waste

FSW

Mechanical properties

Copper

[1] L. Cederqvist, T. Oberg, Reliability study of friction stir welded copper canisters containing Sweden’s nuclear waste, Reliability Engineering and System Safety, 93 (2008) 1491–1499.

[2] T. Källgren, Friction Stir Welding of Copper Canisters for Nuclear Waste, Department of Materials Science and Engineering. Licentiate Thesis, Stockholm, Sweden (2005).

[3] R.S. Mishra, Z.Y. Ma, Friction stir welding and processing, Materials Science and Engineering, R: Reports., 50 (2005) 1-78.

[4] W.M. Thomas, E.D. Nicholas, Friction stir welding for the transportation industries, Materials and Design., 18 (1997) 269-273.

[5] H.J. Liu, H. Fujii, M. Maeda, K. Nogi, Tensile properties and fracture locations of friction-stir-welded joints of 2017-T351 aluminum alloy, Journal of Materials Processing Technology., 142 (2003) 692-696.

[6] T.R. McNelley, S. Swaminathan, J.Q. Su, Recrystallization mechanisms during friction stir welding/processing of aluminum alloys, Scripta Materialia., 58 (2008) 349-354.

[7] R.E.A.C.G. Andersson, Fabrication of containment canisters for nuclear waste by friction stir welding, Proceedings of the First International Symposiumon Friction Stir Welding, (June 1999).

[8] T.T.T. Hautala, Friction stir welding method, Proceedings of the Sixth International Conference on Trendsin Welding Research, (2003) 324-328.

[9] K.T. PARK Hwa Soon, NAGANO Yoshitaka, NAKATA Kazuhiro, USHIO Masao. Friction stir welding of copper and copper alloys, Osaka University, Joining and Welding Research Institute., 32, 1 (2003) 43-46.

[10] T.M. Sakthivel, J. Microstructure and mechanical properties of friction stir welded copper, Journal of Materials Science., 42 (2007) 8126-8129.

[11] G.M. Xie, Z.Y. Ma, L. Geng, Development of a fine-grained microstructure and the properties of a nugget zone in friction stir welded pure copper, Scripta Materialia., 57 (2007) 73-76.

[12] R. Nandan, T. DebRoy, H.K.D.H. Bhadeshia, Recent advances in friction-stir welding-Process, weldment structure and properties, Progress in Materials Science., 53 (2008) 980-1023.

[13] J.J. Shen, H.J. Liu, F. Cui, Effect of welding speed on microstructure and mechanical properties of friction stir welded copper, Materials & Design. 31 (2010) 3937-3942.

[14] P. Xue, G.M. Xie, B.L. Xiao, Z.Y. Ma, L. Geng, Effect of Heat Input Conditions on Microstructure and Mechanical Properties of Friction-Stir-Welded Pure Copper, Metallurgical and Materials Transactions A., 41 (2010) 2010-2021.

[15] J.E.I. A Polar, Microstructural Assessment of Copper Friction Stir Welds, Journal of Manufacturing Science and Engineering, 131 (2009) 031012.

[16] W.B. Lee, S.B. Jung, The joint properties of copper by friction stir welding, Materials Letters., 58 (2004) 1041-1046.

[17] M. Mahoney, C. Rhodes, J. Flintoff, W. Bingel, R. Spurling, Properties of friction-stir-welded 7075 T651 aluminum, Metallurgical and Materials Transactions A., 29 (1998) 1955-1964.

[18] G. Liu, L.E. Murr, C.S. Niou, J.C. McClure, F.R. Vega, Microstructural aspects of the friction-stir welding of 6061-T6 aluminum, Scripta Materialia, 37 (1997) 355-361.

[19] Y. Sato, H. Kokawa, M. Enomoto, S. Jogan, Microstructural evolution of 6063 aluminum during friction-stir welding, Metallurgical and Materials Transactions A., 30 (1999) 2429-2437.

[20] B. Heinz, B. Skrotzki, Characterization of a friction-stir-welded aluminum alloy 6013, Metallurgical and Materials Transactions B., 33 (2002) 489-498.

[21] K. Jata, K. Sankaran, J. Ruschau, Friction-stir welding effects on microstructure and fatigue of aluminum alloy 7050-T7451, Metallurgical and Materials Transactions A., 31 (2000) 2181-2192.

[22] C.G. Rhodes, M.W. Mahoney, W.H. Bingel, R.A. Spurling, C.C. Bampton, Effects of friction stir welding on microstructure of 7075 aluminum, Scripta Materialia., 36 (1997) 69-75.

[23] Y.K. Sato, Hiroyuki, Distribution of tensile property and microstructure in friction stir weld of 6063 aluminum, Metallurgical and Materials Transactions A., 32 (2001) 3023-2031.