| The smart grid, as one of the seven strategic emerging industries ofthe12th Five-Year Plan, will lead to the rapid development of wire andcable industry in China. Shaped wires are widely used in concentric layoverhead wires, as they have advantages of increasing the utilization ofconductor section, lower wire sag rate, good corrosion resistance, littlebreak damage, strong self-damping properties, reducing the wind load,reducing dancing occurrence probability, comparing with the round wires.Shaped magnet wires are manufactured as coils or windings of theelectrical products, and widely used in generators, motors, transformers,electronic instruments, electromagnets and so on. It must satisfy a numberof requirements of the utilities and manufacturing processes. The quality ofshaped dies is the guarantee of high quality shaped wire. Their materialand structure directly affect the quality of drawing wire, lifetime of die andeconomic efficiency of enterprises. Currently, the main material of thedrawing dies is the cemented carbide. Its material properties lead to seriouswear and great consumption of dies, low accuracy and poor quality of thedrawing products and the waste of raw copper materials, which result inlow production efficiency and great labor intensity, also greatly hamper theimprovement of product quality and production efficiency of drawingindustry. In addition, both of tungsten and cobalt, the raw material ofcemented carbide drawing die, are important national strategic resources.The cemented carbide material mold consumption directly lead to a wasteof resources of the national strategy. CVD diamond film has manyexcellent properties close to natural diamond, such as high hardness andwear resistance, high elastic modulus, good thermal conductivity, lowfriction coefficient, and good chemical stability. Therefore, research and development of novel CVD diamond coated drawing dies with excellentperformance can greatly improve die lifetime, reduce production costs,improve processing quality, production efficiency and product quality.Besides, it is of vital significance to reduce the consumption of thestrategic resource, build a resource-saving society and achieve sustainableeconomic development strategy.This article designed the structure of shaped drawing dies with thetechnology of CAD/CAE according to the flow deformation law of theplastic matal.The drawing process of the diamond coated shaped drawingdie was simulated with utility of nonlinear finite element analysis softwarebased on the elastic-plastic finite element method. And obtained the stressand strain distribution law in the drawing process, as well as the optimalstructure parameters of the CVD diamond coated shaped dies under acertain condition. The shaped drawing dies were manufactured on the lowspeed wire electrical discharging machine (LSWEDM) according to theoptimal interior-hole parameter. Besides, orthogonal design experimentwas applied to improve the processing quality of interior-hole surfaces andthe processing efficiency. And then, CVD diamond films were depositedon the interior-hole surfaces of the shaped drawing dies. The scanningelectron microscopy (SEM), surface profiler and Raman spectroscopy areadopted to present the characterization of both as-deposited CVD diamondfilms before and after polishing. Furthermore, the performance ofas-fabricated CVD diamond coated drawing dies is examined in thepractical production process.The specific contents are as follows:（1） Designed the structures of single-pass shaped drawing dies inCAD/CAE software, whose cross-section was gradually transited from acircular to the required shaped section. So that it was not only in line withthe laws of metal deformation, but met the required speed of the drawingmachine. Non-linear finite element analysis software was adopted tosimulate the drawing process of the shaped copper wires. The axial and radial stress distributions of the copper and shaped dies were obtained. Andthen, the influence of diamond coated shaped drawing die parameters (thesemi-angle of the reduction area, the length of bearing area L, drawingspeed v) on the drawing process was researched by orthogonal experimentmethod, under the condition of a certain compression ratio. The optimalparameters of the drawing dies as well as the influence of the parameterson axial residual stress of the copper and the maximum equivalent stress ofthe drawing dies were obtained.(2) The structure of multi-pass shaped drawing dies was designed,according to the law of plastic deformation, in CAD/CAE software inaccordance with the required gear ratio. And the influence of themulti-passes on the axial, radial stress distribution and the reaction forceunder the same condition in finite element software were studied. Then, weanalyzed the influence of drawing passes and the semi-angle of reductionzone of the last pass on the drawing process.(3) The influence of the processing parameters (including currentpeak, pulse-on time, pulse-off time, main power supply voltage, servovoltage and electrolyte water flow rate) of LSWEDM on manufacturingefficiency and surface roughness was researched by orthogonal test whenmanufacturing cemented carbide dies. And we analyzed the main factorsaffecting the above two performance indictors with the range analysis andvariance analysis, then got the optimal parameter configuration. Finally,we verified the optimization parameters on the low speed wire electricaldischarging machine.(4) The CVD diamond film was deposited on the interior-hole surfaceof the shaped drawing dies. And it was analyzed, before and after polishing,by surface profiler, scanning electron microscopy (SEM) and Ramanspectroscopy. Furthermore, the performance of as-fabricated CVDdiamond coated drawing dies was examined in the practical productionprocess. Comparing with the conventional shaped drawing dies, theworking lifetime of the diamond coated shaped drawing dies could be increased by a factor of above10, and the shaped wires with higher surfacequality were obtained. |
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