Features of Mechanical Treatment of Zirconia Crystals when Manufacturing Dies

Materials based on partially stabilized zirconia (ceramics and crystals) are distinguished by high values of mechanical strength, crack resistance, hardness, corrosion resistance, low coefficient of friction when operating in tandem with most metals, which makes them promising materials for a wide tribotechnical application in highly loaded friction units. An example of such a unit is the die mechanism, which is an integral part of the drawing die tool in the cable industry. These hard precision tools (drawing dies or wire dies) actually determine the ultimate success in the wire drawing process.

Improving the Tribological Properties of Ceramic Dies

The article is devoted to tribological studies of a ceramic composite with a zirconia-based die in order to replace carbide wire drawing dies with ceramic. Sliding friction was done according to the scheme finger-disk without lubrication and with lubrication. The wear rate and friction coefficients were determined, on the basis of which it is proposed to produce portage dies-blanks from zirconium ceramics. The influence of sintering temperature on the mechanical properties of ceramics, especially cracking resistance, was studied. The optimum sintering temperature was determined by the criterion of fracture toughness. The formation of defects after the final firing was investigated. It was found that sintering at a temperature of 1600 ° C is more promising. An trial batch of zirconium ceramic dies showed positive results in the process of drawing copper wire in industrial situations.

MASS PRODUCTION OF HFCVD DIAMOND-COATED WIRE-DRAWING DIES WITHOUT FILAMENT THROUGH THE HOLE

Hot filament chemical vapor deposition (HFCVD) diamond-coated small aperture wire-drawing dies from [Formula: see text] to [Formula: see text][Formula: see text]mm are in high demand. A new deposition technique without filaments through the inner hole of wire-drawing dies is proposed, accompanied with the specially designed fixtures. Temperature distribution on the deposition surfaces is studied by computational fluid dynamics (CFD) simulation based on the finite volume method (FVM); both case study and mass production simulations are accomplished. Excellent performance and uniform multilayer MCD/NCD/MCD/NCD films are successfully deposited on the inner-hole surfaces of total 16 cemented carbide (WC-6wt.%Co) wire-drawing dies with an aperture of [Formula: see text][Formula: see text]mm in one batch. Drawing results of gas shield welding wires show that the lifespan of the multilayer diamond coated wire-drawing dies is about 20 times of the uncoated cemented carbide dies and 2 times of the monolayer MCD coated dies.

Prediction of Effective Strain Distribution in Two-Pass Drawn Wire

In the multi-pass wire drawing process, the diameter of a wire is decreased by continuously passing it through progressively smaller drawing dies. Although the deformation depends on the process variables, in most wire drawing processes, the wire deformation is concentrated on the surface by its direct contact with the drawing dies, causing a nonlinear distribution of radial direction effective strain from the center to the surface. In this study, a new model for predicting this effective strain in two-pass drawn wire was derived based on the upper bound method, and a finite element analysis and drawing experiment were conducted to validate its effectiveness. The proposed model offers a promising approach to determining and thus controlling the strain in multi-pass drawn wire.

Prediction of Hardness in Drawn Copper Wire by Effective Strain from Finite Element Simulation

The study developed a hardness-strain reference curve to be used with the finite element simulation for the prediction of the hardness in the drawn copper wire. The hardness values of the deformed copper specimens from tensile tests were analyzed to construct a relationship between hardness and strain. By using an industrial wire drawing machine, a copper wire was drawn by 5 passes to reduce its diameter from 8 to 4.64 mm. All drawing dies used the same configurations which include an area reduction ratio of 20 percent, an approach angle of 7°, and a bearing length of 0.5 times the feeding wire diameter. The finite element simulations of the wire drawing processes were also performed to predict the effective strains in the drawn copper wires. With the use of the developed hardness-strain curve, the hardness of the drawn wires can be estimated. The results show that the difference between the predicted and measured hardness values is about 10 percent lower in the early stage of the wire drawing process, and the difference increases with the number of passes to about 30 percent higher in the later stage of the process.

Studies of Influence of Process Parameters on the Strain Rate at High-Speed Wire Drawing

This article presents the results of the effect of drawing speed on the strain rate and resistance to plastic deformation. The wire drawing on modern high speed wire drawing machines significantly increases the required amount of drawing dies. The influence of the technological parameters: speed drawing, half-angle of the die, wire diameter and a single strain on the rate of deformation of the metal. The influence of the technological parameters: speed drawing, half-angle of the die, wire diameter and a single strain on the rate of deformation of the metal. It is found that increasing the resistance to drawing dies and achieve passport velocities drawing, when selecting process parameters drawing guided by the principle of uniform strain over the cross section of the wire by matching the single strain with half-angle dies and friction coefficient on the formula given in the article.

Investigating Tungsten Carbide Micro-Hole Drilling Characteristics by Desktop Micro-ECM with NaOH Solution

Due to their hardness and low tool wear, tungsten carbides are widely used in industrial applications, such as spray nozzles, wire drawing dies and spinning nozzles. However, there is no conventional machining process that is capable of fabricating micro-holes, slots and complicated shapes in tungsten carbide. In this study, a low-cost desktop micro electro-chemical machining (ECM) was developed to investigate the characteristics of tungsten carbide micro-hole drilling. The performance parameters of the machining conditions by desktop micro-ECM, such as the machining time, material removal rate, relative tool wear rate, surface quality and dimensional accuracy, were also investigated in this study. The experimental results demonstrate that the low-cost desktop micro-ECM could fabricate micro-holes in the tungsten cemented carbide (WC-Co) workpiece.