Search Results (14)

Die design plays a critical role in achieving high-quality aluminum extrusion products with optimal efficiency. Porthole dies are widely employed to produce hollow profiles for diverse industrial applications, yet their design parameters significantly influence surface quality, geometry, and productivity. In this study, a two-hole porthole die was investigated using both numerical and experimental approaches. The 6060 aluminum alloy (produced in the foundry of Alumil SA, Kilkis, Greece) was selected as the material of focus. Finite Element Analysis was conducted with HyperXtrude™ 2022 software, while experimental trials were performed on a 35 MN extrusion press. To further enhance productivity, a liquid nitrogen cooling system was integrated into the process. The combined numerical and experimental results demonstrated that the redesigned die and the integration of liquid nitrogen cooling significantly improved process performance. Productivity increased by 8.76%, with ram speed rising from 6.8 mm/s to 9.5 mm/s while maintaining dimensional accuracy and stable extrusion conditions. Full article

Extrusion welding of AlMgSi(Cu) alloys is carried out by using porthole dies, as a result of which hollow shapes are formed with longitudinal seam welds. In the case of the inappropriate selection of the chemical composition of the aluminium alloy or improper metal welding conditions, the weld may have reduced strength in relation to that of the base material, thus weakening the strength of structures based on aluminium extrudates. The prediction of metal welding conditions, depending on the chemical composition of the alloy, the temperature and the unit welding pressures, effectively supports the design of porthole dies, thus significantly reducing the number of necessary extrusion tests and die geometry corrections needed during its implementation in industrial practice, and consequently significantly reducing production costs. In this work, an original laboratory test device simulating the behaviour of metal in a welding chamber of a porthole die was applied to examine the ability of AlMgSi(Cu) alloys to produce high-quality joints. Two different chemical compositions of AlMgSi(Cu) aluminium alloys differing in Mg, Si and Cu contents were used: alloy no. 1A (0.68% wt. Mg, 1.04% wt. Si, 0.61% wt. Cu) and alloy no. 3A (0.8% wt. Mg, 1.21% wt. Si, 1.22% wt. Cu). The weldability tests were carried out under various welding temperatures of 450, 500 and 550 °C and under various welding pressures of 150 MPa, 250 MPa and 350 MPa. The microstructural changes in the produced welds were evaluated with the use of OM and SEM/EDS with chemical analysis in micro-areas, whereas the mechanical effects were evaluated by using a static tensile test. Samples after static tensile testing were subjected to fractographic tests to determine the nature of the fractures. The highest values of relative weld strength were obtained under the highest welding temperature of 550 °C and the highest unit welding pressure of 350 MPa: 87% for alloy number 1/1A (high-strength weld), and 62% for alloy number 6/3A (medium-strength weld). Finally, the extrusion tests were performed in industrial conditions with an examination of the EBSD structure and strength of the longitudinal welds. High values of relative weld strength for extrudates from alloy no. 1/1A and alloy no. 3A, 96% and 89%, respectively, were found, which confirmed the previous weldability testing results. Full article

Extrusion welding of AlZnMg alloys encounters great technological difficulties in practice associated with high shaping forces and the low quality of longitudinal welds. Three different chemical compositions of 7021 aluminum alloy, differing in terms of Zn and Mg contents, were used in the first stage of the research. The laboratory device modelling the behavior of metal in welding chambers of the porthole die was applied to examine the ability of 7021 alloys to produce high-quality joints. The weldability tests were carried out for different welding temperatures—400, 450 and 500 °C—and for a fixed welding pressure of 300 MPa. The microstructural effects in pressure-welds were evaluated with the use of OM and SEM/EDS. The temperature–pressure parameters in the welding chambers were analyzed by using the FEM method for original porthole dies while extruding tubes with dimensions of Ø50 × 2 mm. Finally, the industrial extrusion trials were performed with examination of the structure and strength of the seam welds. It was found that it is possible to produce high-quality high-strength welds in tubes extruded from AlZnMg alloys in industrial conditions (the strength of welds in the range of 96–101% of the strength of the basic non-welded material) through properly matched alloy chemical composition of the alloy, construction of the porthole dies and temperature–speed conditions of deformation. Full article

The objectives of this study were to analyze the bonding criteria for friction stir spot welding (FSSW) using a finite element analysis (FEA) and to determine the optimal process parameters using artificial neural networks. Pressure-time and pressure-time-flow criteria are the bonding criteria used to confirm the degree of bonding in solid-state bonding processes such as porthole die extrusion and roll bonding. The FEA of the FSSW process was performed with ABAQUS-3D Explicit, with the results applied to the bonding criteria. Additionally, the coupled Eulerian–Lagrangian method used for large deformations was applied to deal with severe mesh distortions. Of the two criteria, the pressure-time-flow criterion was found to be more suitable for the FSSW process. Using artificial neural networks with the bonding criteria results, process parameters were optimized for weld zone hardness and bonding strength. Among the three process parameters used, tool rotational speed was found to have the largest effect on bonding strength and hardness. Experimental results were obtained using the process parameters, and these results were compared to the predicted results and verified. The experimental value for bonding strength was 4.0 kN and the predicted value of 4.147 kN, resulting in an error of 3.675%. For hardness, the experimental value was 62 Hv, the predicted value was 60.018 Hv, and the error was 3.197%. Full article

Hollow tubes are generally manufactured using porthole die extrusion. A finite element software QForm is used to analyze the material flow of aluminum alloy A6061 tubes inside a specially designed porthole die during tube extrusion. High welding pressure and shorter transverse seam length are required for a sound product. Various extrusion conditions and die geometries and dimensions affect the bonding strength of the products. In this paper, the effects of die geometries on the welding pressure are discussed using the Taguchi method. The simulation results show that a higher welding pressure is obtained with a larger porthole radius, a larger welding chamber height, and a larger bearing length, while a larger bridge width increases the welding pressure slightly. For transverse seam lengths, a shorter transverse seam length can be obtained with a smaller porthole radius and a smaller welding chamber height, and a shorter bridge width and bearing length decrease the transverse seam length slightly. The transverse seam region and flow patterns are observed. Tube expanding tests were also conducted. From the expanding test results, it is known that the fracture position did not occur at the welding line and the bonding strength could reach up to 160 MPa. Full article

During the porthole die extrusion, the separated metal streams are welded together in the welding chamber. The conditions under which this occurs and the integrity of weld seam in the extrudate are impacted by the design of the bridge, including features such as its shape and dimensions. In this research, the commercial finite element method (FEM) software package, DEFORM, was used to run a series of simulation experiments in order to quantitatively understand the relationship between the bridge design and the thermal mechanical history experienced by the material during welding and the impact this has on final weld seam quality. The bridge can be roughly divided into two parts: the lower part, close to the welding chamber, and the upper part, which initially split the billet into metal streams. The results showed that increasing the lower bridge angle led to slightly higher extrusion loads and higher extrudate exit temperatures. As the lower bridge angle increased, creating a streamlined profile to a blunt profile, a dead metal zone formed under the bridge that produced higher strains near the surface of the material. In contrast, changes to the geometry of the upper bridge had little effect on the porthole die extrusion process or the thermal mechanical conditions experienced by the material. Full article

In this study, porthole die extrusion was performed on a graphene-nanoplatelet-reinforced aluminum composite (0.5 wt.% GNP/Al) prepared by powder metallurgy. The microstructure, grain size, microtexture, and mechanical properties of the composite extruded by the porthole die were studied. Along the extrusion direction, the tensile strength of the extruded composite was 139.7 MPa, and the elongation was 27.1%. Along the transverse direction, which included the weld zone, the tensile strength was 126.4 MPa, and the elongation was 24.1%. These values were 6.65% and 54.63% higher than those obtained for pure aluminum, respectively. Fractography along the extrusion direction revealed obvious ductile fracture characteristics; however, these were not so obvious along the transverse direction, mainly due to the anisotropy caused by the grain orientation of the extruded composite, thereby indicating that the composite exhibited excellent weld performance, which was further verified by Optical Microscope, Electron Backscattered Diffraction, and Transmission Electron Microscopeimages. Overall, these results indicate that GNP can contribute to the strength and toughness of composites in the weld zone in porthole die extrusions. Full article

The extrusion of hollow profiles from hard-deformable AlZnMg alloys by using porthole dies encounters great technological difficulties in practice. High extrusion force accompanies the technological process, which is caused by high deformation resistance and high friction resistance in extrusion conditions. As a result of high thermo-mechanical loads affecting the die, a significant loss of dimensional accuracy of extruded profiles can be observed. The different projects of porthole dies for the extrusion of Ø50 × 2 mm tubes from the 7021 alloy were numerically calculated and then tested in industrial conditions by using a press of 25 MN capacity equipped with a container with a diameter of 7 inches (for 7021 alloy and 6082 alloy for comparison). New extrusion die 3 with modified bridge and mandrel geometry and a special radial–convex entry to the die opening was proposed. FEM was applied to analyse the metal flow during extrusion, geometrical stability of extruded tubes and the die deflection. The photogrammetric measuring method was used to evaluate dimensional accuracy of tubes extruded in different conditions and geometrical deviations in porthole dies elements, especially the bridges and the mandrels. Research revealed a high dimensional accuracy of tubes extruded from the 6082 alloy and from the 7021 alloy by using original extrusion die 3, while much higher dimensional deviations were noted for tubes extruded from the 7021 alloy by using extrusion dies 1 and 2, particularly in relation to the circularity, centricity and wall thickness. Full article

Extrusion experiments and 3D numerical modeling were conducted to investigate the dynamic recrystallization and welding quality of a 6063 aluminum alloy hollow square tube extruded by a porthole die at the ram speeds of 3 mm/s, 7 mm/s, 9 mm/s and 11 mm/s. The results showed that average grain size of hollow square tube extruded at the ram speed of 7 mm/s was the smallest. The profile extruded at the ram speed of 3 mm/s exhibited the highest expansion ratio. Dynamic recrystallization (DRX) fractions were highly variable at different ram speeds. DRX fractions in the matrix zones were higher than those in the welding zones, resulting in smaller grain sizes in the matrix zones. Mechanical properties in the welding zones and matrix zones was different. A local strain concentration would occurred during expansion, which would affect the welding quality. Finally, it was found that the uniform microstructure near the welding line would also affect the welding quality. Full article

Despite aluminum profiles, magnesium profiles have not been well developed due to the low formability. Furthermore, extruded magnesium profiles show a strong dependence on the mechanical properties, according to the loading direction. This is caused by a strong basal texture, which is directly dependent on the process parameters during the extrusion and the subsequent aging. Thus, the present paper focuses on the analysis of the microstructure and its evolution of extruded magnesium hollow profiles, which were subjected to a series of heat treatments at 475 °C up to one hour. The hollow profiles were extruded through a porthole die, thus, containing longitudinal weld seams. These were formed by material that underwent heavy shearing along the tool surface based on the friction conditions in the porthole die. Three extrusion ratios (ER = 8:1, ER = 16:1, ER = 30:1) were applied, resulting in three different wall thicknesses of the profiles. The microstructure of the profiles was analyzed using light-optical microscopy (LOM) and scanning electron microscopy (SEM) coupled with electron backscatter diffraction (EBSD). The analysis revealed no change of the microstructure of the profiles extruded at the two higher extrusion ratios within the time frame of the heat treatment. In contrast, the microstructure and, thus, the micro-texture of the profile with the lowest extrusion ratio (ER = 8:1) has been affected to a great extent. While only small changes in microstructure in the weld-free area were observed, the initial microstructure in the weld seam was transformed from fine recrystallized grains into a significantly bimodal microstructure mainly due to an abnormal grain growth (AGG). These changes were accompanied by a promotion of the rare-earth (RE) texture component for the weld-free material and a change of the overall texture from RE to a typical non-RE double fiber texture for the weld seam due to the intense AGG within the short-time heat treatments. In addition, the influence of the extrusion ratio on particle size and distribution as well as the character of the microstructure governing the behavior during heat treatments was analyzed and discussed. Full article

In this study, porthole die used for extrusion of a solid heatsink profile with wall thickness variation ratio up to 15.3 was designed using finite element (FE) simulations. To improve the flow balance in the die, a design approach was introduced to find the appropriate die structure, which includes the porthole and pocket geometry correction, the bearing length adjustment, and the port bridge structure modification. Using the proposed die, the predicted velocity relative difference (VRD) and the maximum velocity difference (ΔV) of extrudate were significantly lower than those of an initial die, which was preliminarily designed based on general design experiences. The required extrusion force and the residual stress in the product were also reduced significantly. Then, the effects of the port bridge structure and welding chamber height on the behavior of the metal flow in the die were investigated. To verify the proposed die design, experimental extrusions were conducted on a 930-ton extruder. The experiment results showed that the extruded product fulfilled the requirements for dimensional tolerances. The design approach presented in this paper can be useful for practical implementation of die design when extruding similar solid heatsink profiles with large wall thickness variation. Full article

Microchannel tube (MCT) is widely employed in industry due to its excellent efficiency in heat transfer. An MCT is commonly produced through extrusion within a porthole die, where severe plastic deformation is inevitably involved. Moreover, the plastic deformation, which dramatically affects the final property of the MCT, varies significantly from location to location. In order to understand the development of the microstructure and its effect on the final property of the MCT, the viscoplastic self-consistent (VPSC) model, together with the finite element analysis and the flow line model, is employed in the current study. The flow line model is used to reproduce the local velocity gradient within the complex porthole die, while VPSC model is employed to predict the evolution of the microstructure accordingly. In addition, electron backscatter diffraction (EBSD) measurement and mechanical tests are used to characterize the evolution of the microstructure and the property of the MCT. The simulation results agree well with the corresponding experimental ones. The influence of the material’s flow line on the evolution of the orientation and morphology of the grains, and the property of the produced MCT are discussed in detail. Full article

The design of a porthole die is one of the key technologies for producing aluminum profiles. For an aluminum profile with high length–width ratio and small cavity, it is difficult to control the metal flow through porthole die with the same velocity to ensure the die’s strength. In the present study, the porthole die extrusion process of aluminum profile with small cavity was simulated using HyperXtrude 13.0 software based on ALE formulation. The simulation results show for the traditional design scheme, the metal flow velocity in porthole die at every stage was severely not uniform. The standard deviation of the velocity (SDV) at the die exit was 19.63 mm/s. The maximum displacement in the small mandrel was 0.0925 mm. Then, aiming at achieving a uniform flow velocity and enough die strength, three kinds of die structure modifications for the porthole die were proposed. After optimization, desired optimization results with SDV of 0.448 mm/s at the die exit and small mandrel deflection were obtained. Moreover, the temperature uniformity on the cross-section of die exit, welding pressure, and die strength were improved greatly. Finally, the optimal porthole die was verified by the real extrusion experiment. A design method for porthole die for aluminum with a high length–width ratio and small cavity was proposed, including sunken port bridges to rearrange the welding chamber in upper die, increasing the entrance angle of portholes, introducing the baffle plate, and adjusting the bearing length. Full article

For the porthole hot extrusion of a thin-walled tube based on metal flow, the role of the die’s structure should be focused on to achieve precision formation, especially for multi-output extrusion and/or complex cross-sectional profiles. In order to obtain a better metal flow balance, a multi-output porthole extrusion die was developed, including some novel features such as a circular pattern of the portholes with a dart-shaped inlet bridge, a buckle angle in the inlet side of the upper die, a two-step welding chamber, and a non-uniform bearing length distribution. Through the use of thermo-mechanical modeling combined with the Taguchi method, the underlying effects of key die features were investigated, such as the billet buckle angle, the porthole bevel angle, the depth of the welding chamber, and the type of bridge on the metal flow balance. The experimental validation showed that the developed numerical model for the multi-output porthole extrusion process had high prediction accuracy, and was acceptable for use in an industrial extrusion with a complex section. Full article