Search Results (8)

Iron-based superconductors have strong potential for magnet applications through their very high upper critical field, low anisotropy and manufacturability through the powder-in-tube (PIT) route. The engineering critical current density (J_e) is a key parameter for measuring the maximum current density that superconducting materials can withstand in practical applications. It serves as a bridge between theoretical research and practical applications of superconductors and has great significance in promoting the development and application of superconducting technology. In this study, Ag sheathed Ba_0.6K_0.4Fe₂As₂ (Ba-122) iron-based superconducting tapes were prepared by using the process of drawing, flat rolling and heat treatment by hot pressing (HP). For the first time, the filling factor of the tapes increased to about 40%, leading to a reduction in the volume fraction of Ag, consequently lowering the overall cost. The optimal parameters for achieving high transport J_e were obtained by comparing the effects of different HP pressures on the properties and micro-morphology of the tapes. The prepared mono-filament tapes are capable of carrying the transport J_e of 4.1 × 10⁴ A/cm² (I_c = 350 A) at 4.2 K, 10 T, marking the highest J_e reported for Ba-122 wires and tapes to date. Our results show that high transport J_e can be obtained in Ba-122 superconducting tapes, and iron-based superconductors have a promising future in practical applications. Full article

Damage due to a shortage or excess of or the pollution of lubricating oil is often cited as one of the most significant issues confronted by the rolling mill sectors. Lubrication can be provided by either central lubrication systems or individual lubrication systems. In this study, the wear characteristics of the mono-block rolling plain bearing material that is utilized in wire rod rolling mills were evaluated under conditions where the lubricating oil medium included either 2.5% of scale, 5% of scale, or no scale at all. In this experimental study, a unique ball-on-flat experimental setup similar to the one used in the ASTM G133-05 standards was used. Bronze was used as the bearing material and 100Cr6 roller-bearing steel was used as a steel ball of 6 mm in diameter. The experiments were carried out at room temperature, at three different sliding speeds of 5 mm/s, 10 mm/s, and 15 mm/s, and with three different loads of 10 N, 20 N, and 30 N. The wear mechanisms were analyzed visually and elementally using Scanning Electron Microscope (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX) methods. An Analysis of Variance (ANOVA) and the Response Surface Method (RSM) were used to analyze the test results, such as volumetric material loss, the coefficient of friction, and the surface profile. In this study, which was carried out in a lubricant environment containing solid particles, the most effective parameter was the environmental parameter. The increase in the number of solid particles caused an increase in volume loss and friction coefficient. Full article

The influence of roll diameter on the strain distribution, shape change, contact pressure, and damage value of a workpiece was investigated during wire flat rolling to control the material properties of the flattened wire. The flattened wires fabricated by the four different rolls were compared using finite element analysis. The strain inhomogeneity of the flat-rolled wire increased with the roll diameter; thus, the macroscopic shear bands were strengthened as the roll diameter increased during wire flat rolling. The contact width and lateral spreading of the flattened wire increased with the roll diameter; therefore, the reduction in area decreased with the roll diameter. The contour of the normal contact pressure on the wire surface exhibited a similar pattern regardless of the roll diameter. The contact pressure showed higher values at the entry, edge, and exit zones in the contact area. The distribution of the damage value varied with the roll diameter. The free surface region tended to have the peak damage value during the process; however, the center region exhibited the maximum damage value with the roll diameter. From the perspective of the damage value, the optimum roll diameter was in existence during wire flat rolling. The underlying cause of the different strain distributions, shape changes, and damage values of the flat-rolled wire was the different contact lengths originating from the different roll diameters during wire flat rolling. Full article

Roll-to-roll extrusion coated films were bonded onto polymer parts by back injection molding (BIM). The polypropylene (PP) coated polyethylene terephthalate (PET) films were pre-patterned with microstructured V-shaped grooves with 3.2 µm and 53 µm width, and other geometries. Bonding on PET and poly(methyl methacrylate) (PMMA) parts was facilitated by either higher tool or melt temperatures but was particularly enhanced by applying a mild oxygen plasma to the backside of the PET film prior to injection of the polymer melt. Silver wires from conductive nanoparticle ink were embedded into the PP coating during the BIM process by controlled collapse of the V-grooves. Thus, the feasibility of combining standard carrier film materials for printed flexible electronics and packaging into a non-flat polymer part was demonstrated, which could be a helpful step towards the fabrication of polymer parts with surface functionality. Full article

Making “digital twins” for rolling processes and mill equipment should begin with the development of mathematical models of the deformation zone. The deformation zone of two-high flat mill rolling have been studied in detail, relevant models are available in many academic papers. However, the same cannot be said about the most complex deformation zones in stands with multi-roll gauge. Therefore, the task of their reliable mathematical description is of immediate interest. The development of mathematical models is necessary for the design of new wire mills and rolling-drawing units. The combination of rolling in stands with multi-roll gauge and drawing is a promising direction in the production of wire from difficult-to-form steels and alloys. Digital models for pressure-based metal treatment are also necessary for calculating the rolling-mill power parameters during the development of new assortments at the operating mills. The models of deformation zones present the basis for developing the multivariable control systems of process conditions of continuous mills. This research is devoted to the study of the deformation zone and the development of a procedure for calculating the power parameters of rolling in a stand with four-roll passes. The solution of these challenges is given using the example of an operating five-stand wire mill. The authors analysed the known analytical dependencies for calculating the rolling mill force and torque. A mathematical model of the deformation zone and a program for calculating the power parameters have been developed. The paper compares the results obtained from calculations based on analytical dependence and on modelling. A comparison with the experimental parameters obtained at the mill is given. The authors assess the feasibility of using the known formulas and analyse the impact of the front and rear tensions on the power parameters of rolling mill. The problem of developing an automatic tension control system for continuous mills with multi-roll groove is substantiated. Full article

The effect of the roll design on the strain distribution of the flat surface, lateral spreading, and the strain inhomogeneity of a flat-rolled wire were investigated during the flat rolling process. Oval-grooved and cambered rolls with various radii were applied to the flat rolling process based on a numerical simulation. The effective strain on the flat surface of the wire increased when using a cambered roll due to the highly intensified contact pressure on the flat surface, while the effective strain on the flat surface of the wire decreased when using an oval-grooved roll. Lateral spreading decreased when using an oval-grooved roll because the spread in the free surface area of the wire was highly restricted by the oval-grooved roll shape. In contrast, the spread in the surface area increased when using a cambered roll due to the less-restricted metal flow at the free surface. Accordingly, a cambered roll with a small radius is highly recommended in order to improve the surface quality of flat-rolled wires. This is beneficial for industrial plants because the cambered roll can be easily applied in flat rolling plants. Full article

A comprehensive research on the flat rolling deformation characterization of microwire has been conducted systematically through finite element simulation and testified by the results from the experimental analysis. The obtained results are compared in terms of lateral spread, geometrical characteristic, contact area width and surface roughness considering the effects of pass reduction and initial wire diameter. The size effect has been identified and surface layer modeling has been set up based on surface grain share and grain size distribution. The numerical method combined with varied flow stress has been verified by experimental value with a maximum difference of 3.7% for the 1.5 mm wire. With the increase of the height reduction, the curvature radius is decreased while the lateral spread and contact area width are increased. Surface roughness evolution in the range of 0.52–0.85 µm for the rolled wire has also been investigated. Full article

The thermal behavior of a rod during the hot shape rolling process was investigated using the off-line hot rolling simulator and numerical simulation. Additionally, it was compared with a plate during the flat rolling process to understand the thermal behavior of the rod during the hot rolling process in more detail. The temperature of the rod and plate during the hot rolling process was measured at several points with thermocouples using the rolling simulator, and then the measured temperature of each region of a workpiece was analyzed with numerical simulation. During hot rolling process, the temperature distribution of the rod was very different from the plate. The temperature deviation of the rod with area was much higher than that of the plate. The variation in effective stress of the rod along the circumferential direction can induce the temperature difference with area of the rod, whereas the plate had a relatively lower temperature deviation with area due to the uniform effective stress on the surface area. The heat generation by plastic deformation during the forming process also increased the temperature deviation of the rod with area, whereas strain distribution of the plate during flat rolling contributed to the uniformity of temperature of the plate with area. The higher temperature deviation of the rod along the circumferential and radial directions during the shape rolling process can increase the possibility of occurrence in surface defects compared to the plate during flat rolling. Full article