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Butt Resistance Welding of Copper to Aluminum Wires

Shamsian, Mahdi | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49360 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kokabi, Amir Hossein; Movahedi, Mojtaba
  7. Abstract:
  8. In this study, Butt resistance welding of copper to aluminum wires was studied. In this regard, the effect of current, pressure, post weld heat treatment and using intermediate layer of tin on the microstructure, strength and special electrical resistance of welds were examined. Based on a series of initial tests to establish the connection with the appropriate strength, the diameter of the aluminum and copper wires respectively 3 and 3.5 mm and their length 9 and 3.5 cm were selected. In order to weld samples, currents 4.4 to 4.7 KA and pressures 0.3 and 0.5 MPa were used. Then post weld heat treatment at currents 0.5, 1 and 1.5 KA on the welded sample in the pressure 0.3 MPa and the current 4.7 KA was carried out. Finally, the tin interface layer with a thickness of 300 Micrometer in welding the aluminum and copper wire at a pressure 0.3 MPa was used. In order to view connection interface and identify reaction layer, scanning electron microscopy was used. Tensile, electrical conductivity and micro hardness tests in order to evaluate the strength and special electrical resistance of welds and changes of hardness at the junction was performed. The results showed at pressure 0.3 and 0.5 MPa, strength of welds steadily improved by increasing the current and the maximum strength values at current 4.7 KA were obtained. In addition, at the same current, bond strength with reduced pressure from 0.5 to 0.3 MPa increased. It also increasing current and reduced pressure was causing increasing reaction layer thickness and electrical resistance of the junction and in terms of welding 0.3-4.7, reactive layer thickness reach 37 micrometer. By doing post weld heat treatment on weld 0.3-4.7, by increasing current of post weld, the reaction layer thickness and interface electrical resistance increased and at current 1.5 KA, its thickness reach 42 micrometer. But by doing post weld heat treatment, strength of welds fell slightly. Increasing strength for samples were related to form a reaction layer with thickness less than the critical layer. According to this, the optimal thickness of this layer at the joining interface of welded samples in pressure 0.3 MPa, 37 micrometer was obtained. In smaller amounts, strength increased and in higher amounts, strength reduced. So maximum strength in welds without the middle layer about 110 MPa(36% strength of aluminum base) in terms of welding under pressure 0.3 MPa and current 4.7 KA was obtained. Finally, by using an intermediate layer of tin in welding samples, copper-tin intermetallic compound Cu3Sn formed at the joining interface and welds with higher strength than the connections without using an intermediate layer and about 120 MPa(40% strength of aluminum base) was obtained. But the electrical resistance of the intersection increased. As a result, optimum conditions in terms of strength and electrical resistance respectively in welding by using the intermediate layer of tin and welding conditions of 0.5-4.7 was obtained
  9. Keywords:
  10. Mechanical Properties ; Copper ; Aluminum ; Butt Welding ; Resistance Spot Welding ; Reaction Layer ; Specific Electrical Resistivity

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