Joining of graphite to electrical pure iron using AgCuTi filler alloy and analysis of residual stress within the brazed joint

• Published in: Welding in the world 2024, Vol.68 (1), p.1-8
• Main Authors: Li, Wen-Wen, Li, Bo-Hong, Mao, Wei, Yang, Jian, Chen, Bo, Xiong, Hua-Ping, Liu, Ye
• Format: Article
• Language: English
• Subjects: Bonded joints; Brazed joints; Chemistry and Materials Science; Circumferences; Diameters; Filler metals; Finite element method; Graphite; Grooves; Iron; Magnetic coils; Materials Science; Metallic Materials; Research Paper; Residual stress; Room temperature; Shear strength; Shock resistance; Solid Mechanics; Theoretical and Applied Mechanics; Thermal resistance; Thermal shock; Thermal stress
• ISSN: 0043-2288; 1878-6669
• DOI: 10.1007/s40194-023-01591-7

In order to solve the heat dissipation of the magnetic coil, the electrical pure iron should be joined to graphite. In this paper, the dissimilar joint of graphite and electrical pure iron was obtained using AgCuTi filler alloy at the brazing temperature of 870 °C for 10 min. In order to relieve the residual thermal stress, grooves with a width of 1.0 mm and a depth of 0.5 mm were machined at the graphite brazing surface, and the grooves were fulfilled by AgCuTi filler alloy. The results showed that the dissimilar joint with a diameter of 60 mm still kept high bonding quality after 10 thermal cycles from 450 °C to room temperature. The as-brazed joint exhibited shear strength of 10.65 MPa. After thermal cycles, the joint strength of 9.44 MPa, 88.6% of the as-brazed joint strength, was retained. The residual stresses within the joint were analyzed by the finite element modeling (FEM), and the results showed that location of the maximum stress transferred to the groove bottom from boundary of circumference. With the grooves, the stress near the boundary of circumference was decreased evidently from 144.6 to 113.8 MPa. The groove played role of pinning effect and improved the thermal shock resistance of the dissimilar joint.