Study On Cold Extrusion Connection Of Automotive Cable And Heat Treatment Of Steel Ending Fitting

Abstract:Automotive cables are key parts for driving safety to transmit force in control system of cars. In this paper, the geometry parameters of steel ending fitting of an automotive cable for braking were optimized. Meanwhile, the condition of cold extrusion connection and microstructures, mechanical properties of ending fitting, which was kept at low temperature for different times, were studied. Based on this work, the cold extrusion process of an automobile cable was improved and the bonding strength of the connection was enhanced.As shown in the results of numerical simulation, it has a positive correlation between the radial pressure on the interface of the cold extrusion connection and the diameter of ending fitting D, but has an inversely relationship between the radial pressure and chamfer dimension C, while the other geometry factors are constant. Moreover, with the increase of internal thread pitch P, the radial pressure is increased before P≥0.5mm, then decreased.Analysis indicates that bonding mechanism of cold extrusion connection is mechanical effect, which is consisted of friction and shear resistance on the interface between ending fitting and wire rope. And the interface is mainly located in the upper of ending fitting while the tail of ending fitting is separate with the wire rope. The orthogonal experiment for simulation shows that D is the most significant factor affecting the bonding strength, and C is the secondary factor, while the most unimportant factor is P. The maximum bonding strength can be obtained with D of11mm, C of0.8×45°and P of0.5mm. The optimized structure has been applied in the producing.In addition, the results of low-temperature heat treatment indicate that with the holding time prolonging at250℃, the pearlite in the microstructure is changed from lamellar to spheroidal gradually, which decreases the hardness and enhances plastic deformation capacity of the steel end fitting, increases the area of interface between ending fitting and wire rope, then promoted the pull-out force and reliability of the cold extrusion connected cable.