The influences of the variable speed and internal die geometry on the performance of two commercial soluble oils in the drawing process of pure copper fine wire

The cold wiredrawing process constitutes a classical-tribological system in which a stationary tribe-element (die) is in contact with a tribe-element in relative motion (wire) and both interacting with the interfacial tribe-element (lubricant). This condition is reflected in the effect of friction as a function of the drawing speed and temperature, and directly affects the wearing of the surface into the die and the final quality on the drawn wire. The aim of this work has been to determine the best conditions to process ETP-copper using two different types of oil/water emulsion lubricants. For this purpose, six different die geometries have been proposed and a set of tests have been carried out at different speeds (between 1 and 21 m/s) to determine those combinations that give a lower value in the required drawing force (Fd). The experiments allowed to know the friction coefficient (µ), the temperature profile inside the drawing die and in the lubricant and also the mean roughness (Ra) in the drawn product. The results have shown that drawing speeds above 10 m/s significantly decrease the drawing force and, as a consequence, the friction effect on the interface. The best results have been achieved in the combinations of the lower die angle (2β = 14°) with drawing speeds between 17 and 18 m/s with both types of lubricants used, obtaining the lower values of the friction coefficient between µ = 0.10–0.15 with the lubricant type D (Agip S234-60 oil at 7% concentration). It has been found that those tests carried out with dies with a smaller approach angle have generally made it possible to obtain better qualities in the final product. Additionally, FEM simulations have been done to analyse those cases with the lower values of µ, throwing values of Fd that are consistent with those measured in the experimental setting and allowing to better understand the behavior of the material as it passes through the die.

Weakening affinity of SUS304 asperities to die surface with TiN coating for preventing delayed cracks in deep-drawn cups

SUS304 stainless steel has strong affinity to carbon tool steel surfaces. Therefore, the flow of material in the flange portion during the deep drawing process is retarded, leading to increase in amount of wall thicknening along the cup edge and rising risk for delayed cracks. In this paper, TiN coating is applied to the drawing die surface to weaken the affinity. Under elevated blank holding forces (BHF), the experimental results showed that the crack-free BHF range for the TiN coated and the uncoated dies are 5~10 kN and 12 kN, respectively. The entire BHF range for successful drawn cups formed with the coated die are crack-free. The crack-free BHF magnitude is successfully lowered and the range is enlarged with the coating. Crack-free cups having large elongated height and low amount of wall thickening along the cup edge are formed. The weak affinity is evidenced by the low estimated coefficient of friction (COF) obtained from a FE simulation model based on the Coulomb’s law of friction. In contrast, the estimated COF of the uncoated die is high even at the low BHF due to the strong affinity. Therefore, delayed cracks are observed under BHF range of 7~11 kN. At BHF of 12 kN, wear fragments are formed in the boundary layer as a result of the continuous polishing of the SUS304 asperities by the uncoated die asperities. The COF is sharpyly decreased due to the smooth relative movement of contacting surfaces facilitated by the particles and the formation of cracks is prevented. However, the segments tend to penetrate into the SUS304 surface under excessive BHF of 13kN and above. The relative motions of the segments are prohibited, resulting in the reformation of the cracks.

Shape Analysis of the Elastic Deformation Region throughout the Axi-Symmetric Wire Drawing Process of ETP Grade Copper

The wire drawing process is commonly perceived as one of the best studied metal forming processes in almost every aspect; however, when considering elastic deformation, researchers usually focus on the uniaxial tensile forces after the material exits the drawing die and not the elastic deformation region before entering the drawing die, even though it may have a significant impact on the strength parameters and the nature of metal flow inside the drawing die. The aim of this research is to theoretically and experimentally identify the deformation in the elastic region and to further link the shape of this region and the values of stress occurring in it with the geometrical parameters of the drawing process and assess its impact on its strength parameters. In order to achieve the assumed goals, numerical analyses using the finite element method and experimental research on the drawing process in laboratory conditions were carried out using Vickers hardness tests and resistance strain gauges measuring deformation in stationary and non-stationary conditions. The obtained results indicate that the shape and the extent of the region of elastic deformations generated in the material before the plastic deformation region during the drawing process depends on the applied deformation coefficient and stationarity of the process.

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.

Study of stress-strain state of cold-drawn hexagonal steel rods

The results of the stress-strain state during drawing of hexagonal steel rods are presented. The effect of the drawing die angle and the degree of reduction on the distribution of the stress-strain state parameters and the elastic aftereffect of the deformed metal is studied.

PERANCANGAN DAN PEMBUATAN COMBINATION DIES PRODUK WALL BRACKET UNTUK TOWEL BAR

Untuk pemenuhan kebutuhan proyek bangunan skala apapun, target waktu yang relative cepat maka diperlukan kerja sama pada subcont penyedia pelengkap proyek bangunan. Bagian sanitasi merupakan kelengkapan interior bangunan, salah satu komponen bagian sanitasi adalah towel bar. Wall bracket yang menjadi bagian towel bar selama ini metode pembuatannya menggunakan mesin bubut manual 1 pcs wall bracket membutuhkan waktu 2 jam. Agar ketersediaan produk towel bar terutama wall bracket dapat tepat waktu, bentuk produk konsisten maka diperlukan inovasi dalam metode pembuatannya yaitu salah satunya menggunakan metode combination dies untuk meningkatkan produksi dan memenuhi permintaan 200 pcs/bulan. Agar mendapatkan produk wall bracket dengan dimensi diameter luar 33.1 mm, tinggi, diameter dalam 3.5 mm, tinggi 8 mm, sudut 82odengan ketebalan 2 mm dengan metode pengerjaan combination dies pada mesin Nagao 110 Ton ditentukan oleh ukuran punch atau drawing die yang tepat, sistem knock out, perhitungan stroke yang tepat sehingga produk tidak menempel pada dies. Pembuatan produk wall bracket pada towel bar dengan metode dies combination dapat mempersingkat waktu proses permesinan dan setiap produk yang dihasilkan dapat lebih dari satu produk disesuaikan dengan kapasitas mesin stamping.

Investigation on the Wear Behavior of Coatings for Lubricant-Free Deep Drawing Processes with a Novel Application-Oriented Test Rig

Lubricant-free deep drawing is motivated by the avoidance of using environmentally harmful lubricants as well as the potential for shortening the process chain by eliminating lubricant application and component cleaning. Central challenges of dry deep drawing are a significant increase in friction as well as in adhesive tool wear due to a lack of a separating lubricant layer between tool and workpiece. An approach to meet these challenges is the modification of the tools through diamond-like coatings. Based on findings from laboratory tests, a-C:H and ta-C coatings were selected and their effectiveness in overcoming these challenges was demonstrated in single stroke tests in previous research. In order to use the process-specific advantages of forming technology, high tool life is required. In this context, this research aims at investigating the application behavior of a-C:H and ta-C coatings during lubricant-free deep drawing of a high number of components made of the aluminum alloy AA5182. For this purpose, a new wear test rig is applied, which enables the time and material efficient production of high quantities. Numerical methods are utilized to identify the drawing die radius as well as the blank holder as the highest loaded areas. Based on these findings, the wear of the coatings as well as that of an uncoated tool as a reference is analyzed in these areas by optical and tactile measurements. In addition, the influence of tool wear on the component surface quality is determined. It is proven that the ta-C coating increases the tool life from 10 components in uncoated condition up to 3,000 components.

Achievements of Nearly Zero Earing Defects on SPCC Cylindrical Drawn Cup Using Multi Draw Radius Die

In recent years, the old-fashioned cylindrical cup shapes are still widely used, and there are many defects which could not be solved yet. In the present research, the classical earing defects, which are mainly caused by the material mechanical property of the anisotropic property of the material (R-value), are focused on. The multi draw radius (MDR) deep drawing die is applied and investigated to achieve nearly zero earing defects by encountering the R-value during the deep drawing process. Based on the experiments, in different directions in the sheet plane, the somewhat concurrent plastic deformation could be controlled, and the uniform elongated grain microstructure and uniform strain distributions on the cup wall could be achieved. Therefore, on the basis of these characteristics, the earing defects could be prevented, and the nearly zero earing defects could be achieved. However, to achieve the nearly zero earing defects, the suitable MDR die design relating to the R-value should be strictly considered. In the present research, to apply the MDR die for the medium carbon steel sheet grade SPCC cylindrical drawn cup, the following was recommended: the large draw radius positioned at 45° to the rolling direction and the small draw radius positioned along the plane and at 90° to the rolling direction. Therefore, in the present research, it was originally revealed that the nearly zero earing defects could be successfully performed on the process by using the MDR die application.

Recovery of Diamond and Cobalt Powders from Polycrystalline Drawing Die Blanks via Ultrasound Assisted Leaching Process—Part 2: Kinetics and Mechanisms

The leaching of industrial polycrystalline diamond (PCD) blanks in aqua regia at atmospheric pressure between 60 °C and 80 °C was performed using an ultrasound to improve the rate of cobalt removal in order to be able to reuse very expensive polycrystalline diamond. Because cobalt (20 wt.%) is used as a solvent catalyst in the production of PCD, its recovery is very important. The cleaned PCD are returned to the production process. Kinetic models were used in the study of cobalt dissolution from polycrystalline diamond blanks by measuring the declining ferromagnetic properties over time. For a better understanding of this leaching process, thermochemical aspects are included in this work. The lowest free Gibbs energy value was obtained with a low solid/liquid ratio and the full use of an ultrasound. A transition from a reaction-controlled to a diffusion-controlled shrinking core model was observed for PCD with a thickness greater than 2.8–3.4 mm. Intermittent ultrasound doubles the reaction rate constant, and the full use of ultrasound provides a 1.5-fold further increase. The obtained maximum activation energy between 60 °C and 80 °C is 20 kJ/mol, for a leaching of diamond blank with grain size of 5 µm.