Oxide distribution and microstructure in welding zones from porthole die extrusion

The oxide distribution and microstructure in longitudinal and transverse welding zones during the billet-to-billet extrusion process through porthole die were adequately investigated by means of finite element method,scanning electron microscopy and optical microscopy.The results indicate that the oxides exist at the interface between the matrix and transverse welding zone rather than longitudinal welding seam.The longitudinal welding zone reveals a darker band including the largest grain with irregular shape due to the abnormal grain growth under the heavy shear deformation and high temperature.The transverse welding zone consists of equiaxed recrystallized grains which are a little finer than those in the longitudinal welding seam.

Extrusion force analysis of aluminum pipe fabricated by CASTEX using expansion combination die

To determine the extrusion force of pipe fabricated by continuous casting and extrusion (CASTEX) using an expansion combination die, the metallic expansion combination die was divided into diversion zone, expansion zone, flow dividing zone, welding chamber, and sizing zone, and the corresponding stress formulae in various zones were established using the slab method. The deformation zones of CASTEX groove were divided into liquid and semisolid zone, solid primary gripping zone, and solid gripping zone, and the formulae of pipe extrusion forces were established. Experiments were carried out on the self-designed CASTEX machine to obtain the aluminum pipe and measure its extrusion force using the expansion combination die. The experimental results of radial extrusion force for aluminum pipe are in good agreement with the calculated ones.

FEM simulation of aluminum extrusion process in porthole die with pockets

In order to investigate the effects of pockets in the porthole die on the metal flow,temperature at the die bearing exit and the extrusion load were contrasted with the traditional die design without the pockets in the lower die.Two different multi-hole porthole dies with and without pockets in lower die were designed.And the extrusion process was simulated based on the commercial software DEFORM-3D.The simulation results show that the pockets could be used to effectively adjust the metal flow and especially benefit to the metal flow under the legs.In addition,the maximum temperature at the die bearing and the peak extrusion load decrease,which indicates the possibility of increasing the extrusion speed and productivity.

NUMERICAL DESIGN OF DIE LAND FOR SHAPE EXTRUSION

In the extrusion of shapes with flat faced die,the proper design of die land is of critical importance in avoiding the generations of geometry defects.A methodology for the design of die land,which consists of a simulation adjustment iteration,is proposed.The metal flow in extrusion is simulated by the three dimensional finite element method and the die land is adjusted according to the simulation result.Both the formulae for adjustment of the die land and the criterion for the judgment of proper die land are suggested.The extrusion of an L section shape is chosen as the computational example and the result is compared with the industrial design.

Influence of dynamic recrystallization on microstructure and mechanical properties of welding zone in Al-Mg-Si aluminum profile during porthole die extrusion

The effect of dynamic recrystallization(DRX)on the microstructure and mechanical properties of 6063 aluminum alloy profile during porthole die extrusion was studied through experiment and simulation.The grain morphology was observed by means of electron backscatter diffraction(EBSD)technology.The results show that,at low ram speeds,increasing the ram speed caused an increase in DRX fraction due to the increase of temperature and strain rate.In contrast,at high ram speeds,further increasing ram speed had much less effect on the temperature,and the DRX faction decreased due to high stain rates.The microhardness and fraction of low angle boundaries in the welding zones were lower than those in the matrix zones.The grain size in the welding zone was smaller than that in the matrix zone due to lower DRX fraction.The decrease of grain size and increase of extrudate temperature were beneficial to the improvement of microhardness.

Achieving three-layered Al/Mg/Al sheet via combining porthole die co-extrusion and hot forging

Al/Mg/Al sheet with good bonding quality and mechanical properties was fabricated based on the proposed porthole die co-extrusion and forging(PCE-F)process.There were no voids,cracks or other defects on the Al/Mg interface.A continuous diffusion zone with two-sub-layer structure was formed across the Al/Mg interface,and its width increased with higher temperature or reduction ratio.The sub-layers formed at low and high temperature were identified to be solid solutions and intermetallic compounds(IMCs)including y-MgpAl^and^-Al3Mg.In Al layer,the welding zone mainly consisted of fine equiaxed grains with several coarse elongated grains,while the majority of matrix zone is coarse elongated grains.The rolling textures were dominated in both welding and matrix zones.In Mg layer,the welding zone exhibited complete DRXed grain structure,while several unDRXed coarse grains were observed in the matrix zone.With the increasing temperature,the grain size of Al and Mg layer firstly decreased and then increased.High reduction ratio strongly refined the grain structure of Al layer,while slightly affected the Mg layer.The Al/Mg/AI sheet experienced stress-drops twice during the tensile test.The first stress-drop was determined by the IMCs and microstructure of Mg layer,while the second stress-drop was closely related to the microstructure of Al layer.Al/Mg/Al sheet forged at the lowest temperature without the formation IMCs exhibited the highest stress for the first stress-drop,and that forged under the highest reduction ratio with the smallest grain size in Al layer had the highest stress for the second stress-drop.

Analysis and FEM simulation of extrusion process of bimetal tubes through rotating conical dies

Bimetal tube extrusion process through rotating conical dies was studied analytically and numerically. A kinematically admissible velocity field was developed to evaluate the internal power and the power dissipated on frictional and velocity discontinuity surfaces. By balancing the moment applied by the rotary die with the moments caused by the circumferential frictions in the container and on the mandrel, the twisting length of the material in the container was determined. By equating the total power with the required external power, the extrusion pressure was determined by optimizing with respect to the slippage parameter between the die and the outer material. It is shown that the extrusion pressure is decreased by about 20% by the die rotation. The bimetal tube extrusion process through rotating die was also simulated using the finite element code, ABAQUS. Analytical results were compared with the results given by the finite element method. These comparisons show a good agreement.

Isothermal extrusion speed curve design for porthole die of hollow aluminium profile based on PID algorithm and finite element simulations

The isothermal extrusion process of hollow aluminium profile was investigated using incremental proportional-integral-derivative(PID)control algorithm and finite element simulations.The range of extrusion speed was determined by considering the maximum extrusion load and production efficiency.By taking the optimal solution temperature of the secondary phase as the target temperature,the extrusion speed–stroke curve for realizing the isothermal extrusion of the aluminium profile was obtained.Results show that in the traditional constant extrusion speed process,the average temperature of the cross-section of the aluminium profile at the die exit rapidly increases and then slowly rises with the increase in ram displacement.As the extrusion speed increases,the temperature difference at the die exit of the profile along the extrusion direction increases.The exit temperature difference between the front and back ends of the extrudate along the extrusion direction obtained by adopting isothermal extrusion is about 6.9℃.Furthermore,the heat generated by plastic deformation and friction during extrusion is balanced with the heat transfer from the workpiece to the container,porthole die and external environment.

Analytical design of dies for the extrusion of sheets and annular parison

Based on the method of representative values and the flow pattern, that is, the position of the isobars parallel to the die orifice （PIPDO）, the design of dies for the sheet and annular parisons was improved in the present paper. Since this pattern includes the effects of the sloped manifold and the equations for designing the circular manifold are independent of operating conditions and the material, the distribution system of a die gives better uniformity of flow. In the previous study by Winter a defect was found, that is, the calculated position of the path of the island area lagged behind actual position. This defect was eliminated, and the modified equation was obtained. Another flow pattern, in which the pressure loss on all flow path is equal （PLFPE）, was introduced. The equivalency of the above two flow patterns was proved theoretically in this paper.

Effects of process parameters and die geometry on longitudinal welds quality in aluminum porthole die extrusion process

By using the rigid-visco-plasticity finite element method, the welding process of aluminum porthole die extrusion to form a tube was simulated based on Deform-3D software. The welding chamber height （H）, back dimension of die leg （D）, process velocity and initial billet temperature were used in FE simulations so as to determine the conditions in which better longitudinal welding quality can be obtained. According to K criterion, the local welding parameters such as welding pressure, effective stress and welding path length on the welding plane are linked to longitudinal welds quality. Simulation turns out that pressure-to-effective stress ratio （ρ/σ） and welding path length （L） are the key factors affecting the welding quality, Higher welding chamber best and sharper die leg give better welding quality. When H=10 mm and D=0.4 mm, the longitudinal welds have the best quality. Higher process velocity decreases welds quality. The proper velocity is 10 mm/s for this simulation. In a certain range, higher temperature is beneficial to the longitudinal welds. It is found that both 450 and 465℃ can satisfy the requirements of the longitudinal welds.

Effects of die geometry on non-equal channel lateral extrusion(NECLE) of AZ80 magnesium alloy

Non-equal channel lateral extrusion（NECLE） is a new process that can be used to attain higher grain refinement in comparison with equal channel lateral extrusion（ECLE）. The die design for this process was numerically and experimentally studied. After finding a good correlation between the numerical and experimental results, more comprehensive FE analyses were carried out. Different die geometrical parameters were considered and their effects on the induced plastic strain, stress distribution, velocity field and forming load of the process were investigated. It was found that by this process with a suitable set of die geometrical parameters, higher induced effective strain and more homogeneous strain distribution could be achieved in comparison with ECLE operation.

THEORETICAL ANALYSES ON DESIGN OF SHEAR EXTRUSION DIE

ＴＨＥＯＲＥＴＩＣＡＬＡＮＡＬＹＳＥＳＯＮＤＥＳＩＧＮＯＦＳＨＥＡＲＥＸＴＲＵＳＩＯＮＤＩＥ①ＹｕａｎＸｉＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｒｉｎｇ，ＣｅｎｔｒａｌＳｏｕｔｈＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏ...

A APPLICATION OF ANSYS ON A SECTION EXTRUSION DIE

Porthole dies are important tools in extrusion process to produce hollow sections and the life of the dies counts for the cost of products. In this work, the finite element method was adopted to analyze a particular porthole die to produce hollow rectangle sections which are widely used in construction. The upper die was mainly studied. Because it is symmetrical, a quarter of the die was analyzed. The upper die was divided into 2199 elements with 3018 nodes. Elements were produced by four steps and the geometric shape of the die could be well simulated. The boundary condition was given according to the shape of the welding chamber and an empirical average extrusion stress was adopted, which was 210N/mm 2. Three-dimensional equivalent stresses were received. The original porthole die studied had obvious stress concentration and the stress distribution was very inhomogeneous, which would heavily affect the die life. A new design was proposed in which the portholes were rearranged and their shape and dimension were changed. According to the finite element analysis, the stress distribution of the improved die was quite homogeneous and the stress concentration was lessened.

Effect of die inlet geometry on extrusion of clover sections through curved dies:Upper bound analysis and experimental verification

The effect of die inlet and transition geometry on the extrusion loads and ~aaterial flow for extrusion of clover sections were investigated and presented both theoretically and experimentally. For this purpose, four different die geometries including straight tapered and cosine transition profile and each of them having round and clover inlet geometries were chosen. In the experimental study, commercially pure lead was used because of its hot forming characteristic at room temperature. A newly kinematical admissible velocity field to analyze different profiles of extrusion dies of clover section from round bars was proposed by upper bound analysis. It is clear that the extrusion loads obtained from the theoretical analysis for various die inlet-die transition geometry combinations are in good agreement with the experimental results. Axis deviations of the parts which define the dimensional quality of the products were also investigated.

Conformal mapping modeling of metal plastic deformation and die cavity in special-shaped extrusion

With the help of Complex Function Mapping studied results, the analysis function of Conformal Mapping is set up. Since the complicated three dimension’s deformation problems are transferred into two dimension problems, both the stream function and strain ratio field are analyzed in the metal plastic deformation. Using the upper-bound principles, the theory of metal deformation and die cavity optimized modeling is established for random special-shaped product extrusion. As a result, this enables the realization of intelligent technique target in the die cavity of CAD/CAM integration.

Non-steady FE analysis on porthole dies extrusion of aluminum harmonica-shaped tube

According to the rigid-viscoplasticity finite element method,the porthole die extrusion process of an aluminum harmonica-shaped tube was successfully simulated based on software Deform-3D. The distribution of stress field,effective strain field,velocity field and temperature field during the extrusion process were discussed and the metal flow in welding extrusion was analyzed. The simulation results show that the material flow velocities in the bearing exit are non-uniform with the originally designed die and the forepart of the profile is not neat or even. Aiming at solving this problem,the modification method of die structure was improved. The result shows that the uniform material flow velocities in the die exit and a perfect extruded are obtained by modification bearing length.

Structure optimization of porthole die based on aluminum profile extrusion process numerical simulation

Porthole die extrusion method is used to produce hollow aluminum profile. Due to the complexity of the porthole die structure and the material flow, it is very difficult to get ideal profile products with the firstly designed die structure. Finite volume numerical simulation was used to analyze the extrusion process of a hollow profile with porthole die and the problem of non-uniform material flow was found. Optimization was made to the originally designed die to solve the problem. Lower load, reasonable seaming location and even extruded forepart with uniform material flow in the optimized die extrusion were obtained. Guidelines to porthole die design were given and it is also concluded that finite volume method with Eulerian description avoids mesh regeneration and is suitable to numerical simulation of severe deformation processes, such as profile extrusion.

Mathematical model of determination of die bearing length in design of aluminum profile extrusion die

Based on the finite element simulation of profile extrusion process, the effect of local extrusion ratio, die bearing area and the distance between extrusion cylindrical center and local die orfice center on mental flow velocity was investigated. The laws of deformed metal flow on profile extrusion process were obtained. The smaller the local extrusion ratio, the faster the metal flow velocity; the smaller the area of die bearing, the faster the metal flow velocity; the smaller the distance of position of local die orifice(the closer the distance of position of local die orifice from extrusion cylindrical axis), the faster the metal flow velocity. The effect of main parameters of die structure on metal flow velocity was integrated and the mathematical model of determination of die bearing length in design of aluminum profile extrusion die was proposed. The calculated results with proposed model were well compared with the experimental results. The proposed model can be applied to determine die bearing length in design of aluminum profile extrusion die.

EXTRUSION DIE CAE OF THE STEEL REINFORCED PLASTIC PIPE

The steel reinforced plastic pipe is a new kind of pressure pipe. It is made up with steelwires and plastic. Because reinforced skeleton of the steel wire increase the complexityof plastic flow during the extrusion phase, the traditional design criteria of extrusiondie is not suitable. The study on extrusion die of the kind of pipe is very importantstep in produce development. Using finite element (FE) method in this paper, theflow rule of molten plastic inside the die has been predicted and a groap of optimalstructural parameters was obtained. These results are helpful for reducing the designcycle and improve the quality of the final product.

OPTIMUMDESIGNOFSTREAMLINEDEXTRUSIONDIESBASEDONUPPERBOUNDMETHODANALYSIS

A more universal and flexible method of constructing the streamlined die surfaces is presented. The streamlined die surfaces are interpolated by the arbitrarily cross sectional shapes of the die entrance and exit. The boundaries of the die entrance and exit are represented by Ferguson curves with tension parameters. By adjusting the tension parameter, the cross sectional shapes of the die entrance and exit with line segments can be accurately constructed. The upper bound method is used to analyze the procedure of extrusion, the pseudo independent parameters in kinematically admissible velocity and die surface are computed by minimizing the extrusion load, so the optimum die surface is obtained. The effects of frictional condition, die length, area reduction and product shaped complexity are discussed in relation to the extrusion load.