Backward Extrusion Process Research Articles

The Influence of Velocity and Pressure on Residual Stresses During The Backward and Forward Extrusion of AA6061 T6 Aluminium Alloy

The extrusion process is considered a cost-effective manufacturing method compared to alternative production techniques, offering excellent mechanical properties and high product quality. Combined extrusion further enhances efficiency by minimizing the need for additional processing steps, thereby saving time and reducing production costs. The die geometry and friction factors play a critical role in determining the success and quality of this process. In this study, AA 6061 T6 aluminium alloy was selected as the billet material to investigate a combined backward–forward extrusion process and to examine the influence of process parameters, such as velocity and pressure, on the residual stresses formed in the extruded products. Two punch types were utilized: a hexagonal punch for the backward extrusion direction and a square punch for the forward extrusion direction. For each punch type, three different cross-sectional areas (140, 130, 115 mm2) and three different forming velocities (0.25, 0.5, 1 mm/s) were tested to assess the effect of forming pressure on residual stresses. The experiments were conducted using a heat-treated H13 steel die with a hydraulic press under lubricated conditions. The findings indicate that increasing the cross-sectional area of the punch, which corresponds to a reduction in pressing pressure, results in higher residual stresses at a constant velocity. The highest residual stresses were observed in the hexagonal region (1315 MPa), corresponding to the backward extrusion process. Intermediate stress levels (

Numerical and experimental investigation of extrusion processes from coil

The use of coil material as semi-finished product in sheet-bulk metal forming (SBMF), offers the possibility to use high-speed presses and thus to achieve high output quantities. However, compared to industrially established forming of pre-cut blanks, the reduced geometric accuracy of the parts due to the asymmetrical material flow represents a challenge. Against this background, the aim of this study is to gain an in-depth knowledge on the influence of the process setup on the material flow direction and on the forming of geared functional parts. A combined numerical-experimental approach of each a lateral and a backward extrusion process of a DC04 sheet metal ( t0 = 2 mm) is applied for a fundamental process analysis. For this purpose, process-dependent causes for the asymmetric part forming are analyzed by means of material flow simulations. Subsequently, the numerical results are verified experimentally in terms of the part geometry, the process force and grain structural changes. Based on the numerical and experimental results, cause-effect relations between material flow, part accuracy and tool load are derived. In addition, the transferability of the causes of the asymmetric material flow to processes with different primary material flow directions and part geometries is verified. The findings facilitate the future counteraction of asymmetrical material flow in SBMF from coil, which in turn leads to enhanced component quality.

Effect on the physical field of the die during the backward extrusion process of magnesium alloy wheel

The eccentric placement of billets reduces the service life of the dies, and at the same time causes the scrapping of the wheel blanks. However, for axisymmetric forgings, eccentric placement is unavoidable. In this study, the mutual effects between the billet and the die during backward extrusion of magnesium (Mg) alloy wheels are analyzed by physical and numerical simulations, focusing on the effects on the physical field of the die. There were dangerous points in the design of the combined die structure and the lower mating surface of the female die and the bottom die were prone to stress concentration during the filling process of the Mg wheel, which led to the cracking of the die. The eccentric extrusion of the wheel resulted in a slope in the filling height of the rim, and it had a great effect on the physical field and microstructure distribution at the same time, which in turn affected the physical field distribution of the wheel die, resulting in uneven load distribution at the lower rim of the die and reducing the life of the combined die. The combined die structure optimization solution can process the female die into a curved surface along the fracture surface and at the same time process a hollow circular table to cooperate with the bottom die and the female die.

Influence of material in sheet-bulk metal forming from coil

AbstractSheet-bulk metal forming (SBMF) represents an innovative approach for the efficient manufacturing of functional integrated parts from sheet metal by applying bulk forming processes to sheet metal. It combines the advantages of part weight optimization and process chain shortening. In view of the increasing demand for functionally integrated components, the forming from coil offers an economical possibility to produce high output rates. Nevertheless, an underfilling of functional elements as well as an asymmetric part forming are current challenges. In order to apply SBMF from coil in industrial contexts, it is necessary to understand the causes of these process limits and to develop measures for improving the forming of functional elements and thereby push existing forming limits. In this paper, both a lateral and a backward extrusion process from coil for the forming of internal and external geared SBMF parts are investigated to develop a fundamental process understanding. In a combined numerical-experimental approach, the influence of the flow behavior of different materials as well as the impact of the main material flow direction of the process on the dimensional part accuracy is analyzed. This enables the evaluation of fundamental material-related dependencies and influences regarding the geometrical part accuracy, the mechanical component properties and the tool load for forming of the conventional deep-drawing steel DC04 (t0 = 2 mm), a high-strength steel material (HC260LA) and an aluminum alloy (AA6082 T6). Based on these findings, measures for material flow control are identified and investigated to counteract the challenges of SBMF from coil. These findings permit the identification of potential transferability of the identified cause-effect mechanisms to different processes, component geometries and materials. Thereby, in particular, an increase in coil width as well as lower a strain hardening behavior of the material offers the possibility to improve the geometrical accuracy of the components.

Physical field regulation of magnesium alloy wheel formed by backward extrusion process with multi-stage variable speed

To reduce the tonnage required during the forming process of magnesium (Mg) alloy wheels by backward extrusion (BE) and refine the grains at the wheel bottom, the multi-stage variable (MSV) speed process is proposed based on the characteristics of Mg alloy wheels formed by BE. A numerical model for the BE process of Mg alloy wheels using the Defrom-3D was constructed, and the effects of constant speed and MSV speed processes on the physical fields and DRXed grain size evolution during the forming of Mg alloy wheels were investigated. Lastly, the simulation results were indirectly verified by industrial trial production. The results show that constant speed extrusion has a small effect on the effective stress, but a large effect on the wheel temperature distribution, where the forming speed of the upper rim plays a decisive role in the final temperature distribution of the wheel. MSV speed process is used to regulate the physical field evolution during wheel forming based on the effect of constant speed on the physical field of the wheel. With the high-speed forming of the rim and low-speed forming of the upper wheel rim (9-9-1 mm/s), the temperature and effective stress distribution of the wheel blank are reasonable while reducing the forming tonnage and refining the grains at the wheel bottom.

High elongation heterostructure rare earth magnesium alloy based on rotating backward extrusion process

In this paper, Mg-9.5Gd-4Y–2Zn-0.5Zr cylindrical parts were prepared by the conventional backward extrusion (CBE) process and rotating backward extrusion (RBE) process. The effects of the two processes on the microstructure and mechanical properties of different orientation regions of rare earth magnesium alloy were analyzed and compared. The RBE process introduces a torsional shear quantity based on the CBE process. By changing the direction of plastic flow, has a positive effect on the elongation (EL) of the alloy. It was found that dynamic recrystallization (DRX) occurred in both CBE and RBE processes. With the transition of deformation, the strain continues to accumulate, and the DRX mechanism changes from discontinuous dynamic recrystallization (DDRX) to continuous dynamic recrystallization (CDRX). Compared with the CBE process, the grain refinement of the RBE process is more significant. After deformation, a more significant heterostructure is obtained in the RBE-45° region, and the average grain size reaches 24.7 μm. The ultimate tensile strength (UTS), yield strength (YS), and EL of the alloy in this region are 292.5 ± 7.7 MPa, 226.6 ± 7.4 MPa, and 21.5 ± 1.3 %, respectively. Although the strength is slightly lower than that of CBE alloy, better plasticity is obtained. The excellent strength-toughness synergy is attributed to the synergistic effect between heterogeneous regions of non-uniform microstructure. This study provides some theoretical guidance for the industrial production of large-size magnesium alloy cylindrical parts and subsequent applications.

Revealing the microstructure, texture evolution and mechanical properties along the whole wall of Mg-Gd-Y-Zn-Zr cylinders by tailoring rotary backward extrusion parameters

In this article, industrial-specification Mg-Gd-Y-Zn-Zr alloy cylinder parts were successfully prepared by rotary backward extrusion process. The microstructure distribution and mechanical properties evolution of the whole wall of different cylinder parts were investigated, and the effects of different rotation speeds on the microstructure and properties were also revealed. The results showed that the strain of the cylinder wall increased significantly with rotation speed increased, thereby generating a higher driving force for the microstructure refinement. The transformation of the inner wall progressed from the deformed zone (bulk-shaped long period stacking ordered (LPSO) phases, coarse deformed grains, and fine recrystallized grains) to the strongly affected zone (particle-shaped LPSO phases and fine recrystallized grains), with the latter expanding as rotation speed increased. Furthermore, there was a gradient distribution of strain in the cylinder walls, with the strain gradient intensifying alongside rotation speed. The transformation of the strongly affected zone into the deformed region from the inner to the outer wall suggested a diminishing effect of rotation speed on LPSO phases fragmentation and grain refinement. Notably, increasing rotation speed rendered improvements in the strength and ductility of the cylinder wall. And mechanical properties also displayed a gradient decrease from the inner wall to the outer wall. This variation in mechanical properties of different regions was closely associated with the contributions of grain boundary strengthening, texture strengthening and second phase strengthening.

Microstructure, Texture, and Mechanical Properties of Mg-Gd-Y-Zr Alloy Prepared by Rotating Backward Extrusion Process

Microstructure, Texture, and Mechanical Properties of Mg-Gd-Y-Zr Alloy Prepared by Rotating Backward Extrusion Process

Effect of long-period stacking ordered phase on dynamic recrystallization in Mg-Y-Zn-Zr alloy processed by backward extrusion

During the backward extrusion process, the impact of the long-period stacking ordered (LPSO) phase on dynamic recrystallization (DRX) in the Mg-10Y-2Zn-0.5Zr alloy was studied. The results show that DRX at the α-Mg/18R-LPSO interface belongs to the discontinuous dynamic recrystallization (DDRX) mechanism, and the DRX at the α-Mg/14H-LPSO interface belongs to the continuous dynamic recrystallization (CDRX) mechanism. Under the action of strain force, the 18R-LPSO interface migrates locally to form a “convex” structure. It was easy to produce high-density dislocations around the structure, which promoted DDRX at the α-Mg/18R-LPSO interface. The lamellar 14H-LPSO would undergo severe kink and form a large number of kink bands, providing favorable nucleation sites for CDRX grains. With the increase of the extrusion strain force, the lamellar 14H-LPSO kink angle gradually increases, which promotes the nucleation of CDRX grains at the kink band boundary. In addition, the production of 14H-LPSO kink activates prismatic <a>slip, pyramidal <a>slip and pyramidal <c+a>slip in the α-Mg matrix.

Optimization of Hot Backward Extrusion Process Parameters for Seamless Tube of Mg-8Gd-3Y Alloy by Finite Element Simulation

Optimization of Hot Backward Extrusion Process Parameters for Seamless Tube of Mg-8Gd-3Y Alloy by Finite Element Simulation

An investigation of bimetallic tube fabrication through a novel friction stir extrusion based technology for automotive applications

The bimetallic tubular component fabrication through a novel friction stir backward extrusion (FSBE) process has been proposed in this article. During the extrusion process, the bonding occurs between the substrate and cladding material due to diffusion. The frictional heat generated during the process leads to softening and extrusion of solid clad material that forms a layer on the substrate material. Different sets of materials have been used for feasibility testing. The results show that the process is capable of uniform cladding and void-free bonding for different sets of material. Energy dispersive spectroscopy (EDS) line scan and area mapping were performed at the interface to understand the diffusion pattern. At the interface, intermetallic compounds (IMCs) were confirmed via spot EDS and X-ray diffraction (XRD) analyses. Strong metallurgical bonding occurs between the substrate and the cladding material due to the interdiffusion of the materials, and the flattening test was performed to check the bonding efficacy. Thus, this process opens new opportunities for the fabrication of bimetallic tubular components, which can be used in electrical, structural, lightweight, and corrosion-resistance applications.

Simulation study on microstructure evolution during the backward extrusion process of magnesium alloy wheel

Magnesium (Mg) alloy wheels can reduce emissions in the context of environmental protection. Further study on Mg alloy wheels is required in light of the enormous automotive market since it is still unknown how the microstructure is evolving for the backward extrusion (BE) process of Mg alloy wheels. In this paper, a numerical model of the Mg alloy wheel was established based on industrial production, and the physical field and dynamic recrystallization (DRX) evolution of cylindrical billet and truncated cone billet on the forming process of Mg alloy wheels were analyzed, as well as the accuracy of the simulation results was verified by physical simulation in laboratory conditions and industrial production. The wheel bottom is in adiabatic temperature rise and the temperature is higher than that of the rim during the wheel forming process, while the effective strain distribution and uniformity are lower than that of the rim. The DRX volume fraction and grain size are consistent with the effective strain evolution. The truncated cone billet can effectively improve the DRX volume fraction and refine the grain size of the wheel compared with the cylindrical billets. This work can provide theoretical guidance for the BE process of Mg alloy wheels.

Practices in isothermal forging for 258 mm-diameter titanium VT23 alloy hemisphere blanks

The results of the backward isothermal extrusion process as to 258 mm-diameter titanium VT23 alloy hemisphere blank forgings having extended fitting adapters are presented. Using three blank sizes, the effect is studied of the two-junction isothermal forging parameters on the hemisphere blank forging qualities. The effect is shown of the strain extent and initial blank sizes at the first junction on the blank forging quality rating at the second junction. It is found that the required hemisphere blank forging qualities as to mechanical characteristics, macro- and microstructures, and geometries correspond to the initial 150 mm-diameter and 110 mm-high blanks being 35 % strained at the first junction. In so doing, the backward isothermal extrusion of the 258 mm-diameter hemisphere blank forgings increases an ultimate strength of 1079 up to 1270 MPa, an impact toughness of 20 up to 25 J/cm2 as well as decreases a blank forging of 11.5 up to 8.9 kg compared to standard similar hot die-forged blanks.

Effects of extrusion ratio and direction on extruded Au nanowires investigated using molecular dynamics simulation

The effects of the extrusion ratio (diameter of the extrusion mold inlet divided by that of its outlet) and direction on extruded Au nanowires (NWs) are studied using molecular dynamics simulations based on the embedded-atom method. The effects are investigated in terms of atomic trajectories, common neighbor analysis, flow field, system pressure, and the extruded NW length-pressing ram displacement curve. The simulation results show that for the forward extrusion process, a smaller extrusion ratio leads to a larger diameter of the extruded NW and a smoother cross-sectional profile. Extruded NWs obtained at a smaller extrusion ratio have a higher face-centered cubic fraction and a less disordered structure due to lower system pressure. The adhesion effect between extruded NWs and mold outer walls increases with increasing extrusion ratio, resulting in an uneven appearance of extruded NWs and a decrease in their length. The backward extrusion process can produce amorphous NWs from crystal NWs. The forward extrusion process can produce NWs that are longer than those produced with the backward extrusion process.

Surface modification of additively manufactured parts by forming

Additive manufacturing (AM) has many advantages compared to conventional processes. Of particular interest is the tool-less manufacturing of components, which allows one component to differ from the next completely and has the possibility of producing complex geometries. At the same time, however, AM has deficits such as long production times, low production tolerances and low surface qualities compared to conventional processes. Therefore, a finishing process using machining is often necessary, which extends the manufacturing time and produces waste. Thus, the avoidance of machining rework is of high interest, especially with expensive materials such as stainless steel or titanium. One approach to avoid machining processes is to use forming technology. By applying a forming operation, surfaces can be smoothened and geometrical aspects can be defined more sharply. Especially for functional surfaces, this procedure is favorable because of the work hardening, which in turn increases the strength of the material. Using the example of laser-based powder bed fusion (PBF-LB) followed by a cup backward extrusion process, two materials, which are frequently used in AM are investigated. On the one hand, the titanium alloy Ti-6Al-4V, as a material with low machinability and low formability at room temperature, and the stainless steel 316 L. Compared to Ti-6Al-4V, 316 L has a higher formability. Cylinders are built using PBF-LB and then formed to smoothen the surface and achieve a higher geometrical accuracy concerning edges. Formed, additively made parts have a more defined geometry, namely sharp edges and a surface roughness reduced by up to 90 %.

Paste backward extrusion process as a suitable method for fabrication of sodium beta-alumina electrolyte closed-end tubes

ABSTRACT In this study, paste backward extrusion is introduced for fabrication of sodium beta-alumina electrolyte closed-end tubes (with a wall thickness of 1 mm and external diameter of 8.0 mm). For this purpose, the two-piece extrusion die was designed and extrudable water-based paste was prepared by using sodium beta-alumina powder, polyvinyl pyrrolidone, as a binder, and ethylene glycol as a plasticizer. The effect of solvent content on the rheological parameters of the paste and the ram extrusion velocity on the liquid phase separation are investigated. The results indicate that the optimum solvent content for making the extrudable paste is in the range of 30–35 wt-%, and the liquid phase separation is obviously occurred when the ram velocity is lower than 1.2 mm s−1. It was also shown that by using backward extrusion, and by applying optimum conditions, closed-end tubes with high density (about 97%) and good surface quality could be fabricated successfully.

Simulation of the process of extruding a bar billet into a cylindrical extrusion die with active friction

Backward extrusion processes are widespread when producing various axisymmetric hollow products. This process is characterized by high values of specific pressures. The meaningful task to be achieved is to reduce loads during this process implementation. The use of active friction forces to reduce loads seems to be promising. The use of a floating die with a protrusion on a cylindrical surface, which will facilitate the billet material pushing, is proposed. For theoretical justification of the process, the provision is made to use the finite-element method. The procedure was simulated for different geometric relationships of the tool, the floating extrusion die path velocities and the billet position relative to the extrusion die. The provision is made to analyze the influence of deformation parameters and velocity parameters on the change in force of the studied procedure. Based on the research findings, the conclusions on the expediency of the studied method use for its practical implementation have been made.

Simulation of the process of isothermal backward extrusion of a thick-walled hollow billet

The processes of extrusion of bar billets are the most widely used for producing metal products in the form of a tall cylinder with thin or thick walls. The process is characterized by high hydrostatic pressure, which makes it possible to achieve high degrees of deformation. However, it is worth noting that in this case great forces and loads on the tool take place. Implementation of the processes of extrusion of billets from difficult-to-form alloys can significantly reduce the deformation forces and ensure the formation of an advantageous strain-stress state. This process is rather sophisticated, subject to the theoretical justification. It is a matter of interest to provide justification of the processes of isothermal extrusion of thick-walled hollow billets, allowing one to produce cylindrically shaped products with relatively thin walls and a thick bottom with a hole. The paper discusses the process of isothermal extrusion of thick-walled hollow billets from high-strength non-ferrous alloys. The process simulation was performed using a software package based on the finite-element method. The influence of various parameters on stresses and strains, varying during deformation in the component, was determined. The conditions of loading for the process were analyzed. The results obtained can form the basis for the development of techniques for performing the backward extrusion of hollow billets in isothermal conditions.

Effect of active action friction forces on technological parameters of backward extrusion

The parameters of deformation degree at theoretical and experimental researches of cold backward extrusion processes of hollow glasses-type products are considered. The dependences of their relationship with the relative degree of deformation and the scale of their conformity are suggested. The published results of experimental and theoretical studies on the impact of technological parameters of the backward extrusion process of hollow products in the conditions of active friction forces to reduce the deformation force and stress-strain state of the billet are analyzed. Insuffi ciently studied features of the process and the possibility for expanding of the application fi eld of the backward extrusion method with the active action of friction forces are noted. The method for calculating of the deformation rate required to determine the current stress in the implementation of the hot backward extrusion process.

Analysis of Forming Behavior in Cold Forging of AISI 1010 Steel Using Artificial Neural Network

Cold forged parts are mainly employed in automotive and aerospace assemblies, and strength plays an essential role in such applications. Backward extrusion is one such process in cold forging for the production of axisymmetrical cup-like parts, which is affected by a number of variables that influence the quality of the products. The study on the influencing parameters becomes necessary as the complexity of the part increases. The present paper focuses on the use of a multi-layered feed forward artificial neural network (ANN) model for determining the effects of process parameters such as billet size, reduction ratio, punch angle, and land height on forming behavior, namely, effective stress, strain, strain rate, and punch force in a cold forging backward extrusion process for AISI 1010 steel. Full factorial design (FFD) has been employed to plan the finite element (FE) simulations and accordingly, the input variables and response patterns are obtained for training from these FE simulations. This ANN model-based analysis reveals that the forming behavior of the cold forging backward extrusion process tends to increase with the billet size as well as the reduction ratios. However, decreases in punch angle and land height lead to the reduction of punch forces, which in turn enhances the punch life. FE simulation along with the developed ANN model scheme would benefit the cold forging industry in minimizing the process development effort in terms of cost and time.