Study Of Interface Bonding And Its Performance Of Copper Clad Steel Composite Wire

The method adopted to manufacture copper clad steel (short for CCS) wire in this study is double copper strip pressure welding and then drawing and annealing it. The grain size of a-Fe phase in cross and longitudinal section, the thickness of diffusion layer, interface bonding strength, interface hardness and its tensile strength, elongation, resistivity were test. The interface bonding and its performance were studied. The effects of drawing deformation and annealing treatment on its microscopic structure and performance were obtained.Experimental results show that the grain size in cross section of a-Fe phase is decreased with the increase of the drawing deformation. Its length diameter ratio in longitudinal section is enhanced toward the drawing direction. The grain size in cross-section of α-Fe phase is enhanced with the increase of the annealing time and annealing temperature, its length diameter ratio in longitudinal section is decreased oppositely.The grain in longitudinal section of a-Fe phase after deformation tends to be equiaxial, the recrystallization processes is thus finished at750℃for2h. The grain size in cross section and length diameter ratio in longitudinal section are almost invariant when continuing to raise the temperature. Through the experimental data analysis, the regression equation about the relation of annealing temperature and annealing time of CCS wire with the grain size in cross section and length diameter ratio in longitudinal section are obtained.According to the tensile strength of primitive pure copper and steel wire, applying the mixed rules of composite material strength, the tensile strength of the copper clad steel wire with different drawing the deformation can be calculated. Through the experimental results, they are closed to measured ones. The tensile strength of CCS wire is decreased with the increase of the drawing deformation, the elongation is increased oppositely. The tensile strength of CCS wire is decreased with the increase of the annealing temperature and time, the elongation is increased oppositely. When the annealing temperature is850℃, annealing time is2h, its tensile strength and elongation are invariable. According to the relationship of Hollomon, through the certification of experiment, the copper clad steel wire’s strain hardening exponent of drawing deformation of50%(n) is0.4.The resistivity of CCS wire is increased with the increase of the drawing deformation. According to the resistivity of primitive pure copper and steel wire, the resistivity of the copper clad steel wire with different drawing the deformation can be calculated. The resistivity of CCS wire is decreased with the increase of the annealing temperature and time. Through the experimental data analysis, the regression equation about the relation of annealing temperature and annealing time of CCS wire with the resistivity are obtained. The hardness of copper matrix, diffusion layer and steel matrix with the same deformation are decreased when continuing to increase the temperature and extend the time. Compared with the hardness in copper side, it is reduced obviously in steel side.In the foundation of traditional test methods, combined with the steel composite testing standards in Japan, this paper presents a new test method of steel composite copper wire-interface bonding strength. After the verification of test, the method in this paper is scientific and reliability. The results show that the diffusion thickness and bonding strength are increased with the increase of annealing temperature and time. Compared with annealing time, annealing temperature has more effect on it. After recrystallization temperature is reached, the interface diffusion layer thickness and bonding strength are invariable when continuing to increase the temperature and extend the time. Calculate the diffusion activation energy of Fe and Cu atoms and diffusion constant by diffusion equation, the relationship of diffusion constant and annealing temperature is conformed. According to the relation of diffusion layer thickness and bonding strength and the requirement of actual producing, the best annealing process is750℃for2h.