Initial Billet Temperature Research Articles

Effects of temperature and effective strain on the flow behavior of Ti–6Al–4V

In this study, the hot backward extrusion of Ti–6Al–4V alloy is considered by finite element analysis and experiments. The effects of reduction and initial billet temperature on the force required for extrusion, on the maximum strain produced and on the formation of surface cracks are discussed. The simulation results show that the increase of temperature at high reduction is considerable and that can be reached 150 °C in the billet and punch interface. Moreover, the maximum strain is predicted at the interface of billet and punch. The study shows that the temperature rise and plastic deformation may induce surface cracks.

Numerical Simulation of the Auto Claw-Pole Thixoforming Process

Thixoforming is an effective near-net-shape forming process to produce components with complex geometry and in fewer forming steps. In this study, thixoforming was used to replace the conventional hot forging to form the auto claw-pole. The finite element code Forge2008Ó was used to simulate the auto claw-pole thixoforming process. The results show that initial billet temperature, punch speed, die temperature and friction have strong impact on the forming process. Finally, the reasonable process parameters for the auto claw-pole thixoforming were obtained: initial billet temperature 1430~1440°C, punch speed 100~200mm/s and die temperature 300~400°C.

Impact of Process Parameters on the Auto Claw-Pole Thixoforming Process

Thixoforming of steel is a potential forming technology, which can realize near-net-shape forming process with good quality in one forming step. In this paper, thixoforming process was used to replace the conventional hot forging process to form the auto claw-pole. The finite element code Forge2008Ó was used to simulate the auto claw-pole thixoforming process. The impact of three main process parameters such as initial billet temperature, punch speed and die temperature on the forming process were investigated. The reasonable process parameters for the auto claw-pole thixoforming were obtained: initial billet temperature 1430~1440°C, punch speed 100~200mm/s and die temperature 300~400°C.

A Comprehensive Model for Predicting Profile Exit Temperature of Industrially Extruded 6063 Aluminum Alloy

The effects of extrusion parameters on the resulting profile exit temperature of industrially extruded 6063 aluminum alloy have been studied using statistical design of experiments (DOE). Two operating parameters (initial billet temperature and ram speed) and three geometrical parameters (extrusion ratio, profile average thickness, and number of die cavities) were investigated. A statistical model was obtained for predicting profile exit temperature with very close agreement between predicted and measured values. Present results indicated that the main contribution towards profile exit temperature comes from plastic work promoted by high extrusion ratios, high initial billet temperatures, and high ram speeds. Further contributions are promoted by parameters affecting friction and redundant work components. In addition to single-factor effects, profile exit temperature was revealed to be affected by a set of complex two-factor and three-factor interactions between the different operating and geometrical parameters. The most remarkable two-factor interactions were shown to exist between extrusion ratio and number of die cavities and between initial billet temperature and ram speed. Complex three-factor interactions have been shown to exist between extrusion ratio, initial billet temperature, and ram speed. These interaction effects are quantified in the present model and are further qualitatively discussed in terms of their effects on the resulting profile exit temperature.

Damage prediction for magnesium matrix composites formed by liquid-solid extrusion process based on finite element simulation

A damage prediction method based on FE simulation was proposed to predict the occurrence of hot shortness cracks and surface cracks in liquid-solid extrusion process. This method integrated the critical temperature criterion and Cockcroft & Latham ductile damage model, which were used to predict the initiation of hot shortness cracks and surface cracks of products, respectively. A coupling simulation of deformation with heat transfer as well as ductile damage was carried out to investigate the effect of extrusion temperature and extrusion speed on the damage behavior of C sf/AZ91D composites. It is concluded that the semisolid zone moves gradually toward deformation zone with the punch descending. The amplitude of the temperature rise at the exit of die from the initial billet temperature increases with the increase of extrusion speed during steady-state extrusion at a given punch displacement. In order to prevent the surface temperature of products beyond the incipient melting temperature of composites, the critical extrusion speed is decreased with the increase of extrusion temperature, otherwise the hot shortness cracks will occur. The maximum damage values increase with increasing extrusion speed or extrusion temperature. Theoretical results obtained by the Deform™-2D simulation agree well with the experiments.

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 (p/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 °C can satisfy the requirements of the longitudinal welds.

Analyses of Plastic Flow and Die Design during Hot Extrusion of Magnesium Alloy Strips

This study involves analyses and experiments of hot extrusion of magnesium alloy strips. Hot compression tests were firstly conducted to obtain the magnesium alloy’s plastic flow stresses at high temperatures. These data are used in the finite element simulations of the thin strip extrusion process. Using the FE simulations, the flow pattern of the magnesium alloy billet within the die, the temperature variation and the thickness distribution at the die exit were analyzed. The effects of different die bearing height design, initial billet temperatures and ram speed on the extrusion load, the temperature at the die exit and the product thickness distribution were also discussed. Finally, hot extrusion experiments were conducted and the experimental values of the extrusion load and dimensions of the products were compared with the analytical values to validate the analytical model. Sound products were obtained using the best designed bearing heights and other appropriate extrusion conditions.

Study of isothermal extrusion of aluminum using finite element simulations

The focus in this work is isothermal extrusion of aluminum. Transient finite element simulations of the extrusion process have been performed over 20 press cycles using the 3D finite element software Altair HyperXtrude 9.0 and the 2D finite element software ALMA2π. The process parameters considered are front billet temperature, initial billet temperature gradient (taper), ram speed and container cooling rate. The press cycle has been divided into three phases: start, middle and the end of the ram stroke. The best combinations of process parameters for isothermal extrusion has been found and represented as so called “isothermal maps” for each phase of the press cycle.

Effect of the extrusion conditions on the texture and mechanical properties of indirect-extruded Mg–3Al–1Zn alloy

The effects of the processing conditions on the texture and mechanical properties of indirect-extruded Mg–3Al–1Zn alloy are investigated. During the extrusion process, the alloy was subjected to various initial billet temperatures and ram speeds, exhibiting different extrudate exit temperatures depending on the extrusion conditions. The Zener-Hollomon parameter acquired from the exit temperature of the extrudate and the ram speed was found to have a significant effect on the grain size, texture, and yield asymmetry of the extruded alloy. Among the processing conditions investigated, a higher Zener-Hollomon parameter resulted in a finer grain size and weaker fiber texture, thereby decreasing the yield asymmetry of the extruded Mg alloy.

Predicting the variation of the exit temperature with the initial billet temperature during extrusion to produce an AZ31 profile

The extrusion process to produce a cross-shaped profile of a wrought magnesium alloy AZ31 was simulated to predict the exit temperature as a function of the initial billet temperature. Three-dimensional FE simulation revealed the evolutions of temperature and extrusion pressure during the process. The initial billet temperature was found to have a stronger influence on the breakthrough pressure than ram speed. It also played an important role in determining the exit temperature and the temperature rise during the process, especially when ram speed was high. At a given ram speed, the relationship between the temperature rise and the initial billet temperature was found to be linear. Such a relationship could be used as guidelines to optimize the extrusion process and to maximize its throughput.

Artificial neural networks to optimize the extrusion of an aluminium alloy

Extrusion of aluminium alloys is a complex process which depends on the characteristics of the material and on the process parameters (initial billet temperature, extrusion ratio, friction at the interfaces, die geometry etc.). The temperature profile at the die exit, largely influences microstructure, mechanical properties, and surface quality of an extruded product, consequently it is the most important parameter for controlling the process. In turn the temperature profile depends on other process variables whose right choice is fundamental to avoid surface damage of the extruded product. In the present work, two neural networks were implemented to optimize the aluminium extrusion process determining the temperature profile of an Al 6060 alloy (UNI 9006/1) at the exit of induction heater (ANN1) and at the exit of the die (ANN2). The three-layer neural networks with Levemberg Marquardt algorithm were trained with the experimental data from the industrial process. The temperature profiles, predicted by the neural network, closely agree with experimental values.

가스터빈용 Alloy718 커플링볼트의 열간 헤딩 공정설계 및 기계적 특성 평가

Alloy718 is the nickel-base super alloy well used as gas turbine components under severe operating conditions because of its high strength at high temperature and excellent creep resistance. In this study, a coupling bolt for the gas turbine component is manufactured by hot heading process instead of whole machining in order to improve the mechanical properties. Die shape for the hot heading has been designed by general design rule of hot forging and also optimal process condition has been investigated by finite element method. The initial billet temperature and the punch speed have been determined by <TEX>$1150^{\circ}C$</TEX> and 600mm/s on the basis of finite element analysis, respectively. The coupling bolt has been manufactured by 200ton screw press and evaluated by experiment in order to investigate the mechanical properties. As a result of experiment, the mechanical properties such as hardness, tensile strength and creep behavior have been superior to those manufactured by machining.

Extrusion Processing of High-Strength Al Alloy 7055

The effects of a combination of extrusion processing parameters and aging schedules on the microstructure and mechanical properties of the 7055 Al alloy were investigated. A safe extrusion processing zone is determined through a limit diagram constructed over the experimental initial billet temperature ranging from 380° to 420°C, extrusion ratio from 10:1 to 40:1, and the ram speed ranging from 1 to 15 mm s−1. Microstructural characterization of as-extruded, solution-treated, and artificially-aged materials was carried out using polarized light microscopy (for grain structure) and transmission electron microscopy (for precipitate morphology). A combination of hardness and tensile tests was used to evaluate mechanical properties. It is shown that in 7055 Al alloy, the optimization of alloy composition, extrusion processing parameters, and peak aging treatment results in reproducible tensile properties of 0.2% P.S. = 725 MPa, UTS = 750 MPa, and % elongation = 12.9. In order to improve the stress-corrosion resistance of peak aged material, retrogression and reaging (RRA) temper was established. A strength-electrical conductivity relationship has been established for the RRA temper between 36% and 37% International Annealed Copper Standard (IACS) electrical conductivity to enable selection of suitable combination of properties.

The Microstructure of AZ 31 Magnesium Alloy by Forward Extrusion with Various Extrusion Parameters

Samples of AZ31 wrought magnesium alloy are hot extruded into forward direction with various initial billet temperatures and extrusion ratios (ERs). Usually the insufficient room temperature formability of magnesium wrought alloys makes processing steps like rolling, extrusion etc. difficult, thus limiting their use for rolled or wrought parts. However, in this paper experiment is preformed under the hot forward extrusion process for AZ31 wrought magnesium alloy with different important parameters. Major process parameters such as punch speed, billet temperatures and ERs are considered and applied to the hot extrusion process with a constant value of the die land. The influence of different billet temperatures and ERs on the hot forward extrusion process is investigated and analyzed in terms of the grain flow, microstructure, grain size and hardness distribution of formed part for magnesium and Mg alloy. Maximum forming loads for various main parameters is tackled and checked to know the optimum forming load for hot forward extrusion process. Also finest grain sizes and an inhomogeneous microstructure of extruded parts seem to occur near the die land of tool-set due to the anisotropic plastic behavior during the hot extrusion process. Extrusion properties such as extrusion load, grain size, micro hardness and surface quality are compared between the main parameters during the hot forward extrusion process. In addition it is easily disclosed from the experiment results that the die land designed for safe tool-set plays a key role in improving the mechanical properties of formed product during hot forward extrusion process for AZ31 magnesium alloy.

Finite Element Simulation of Magnesium Extrusion to Manufacture a Cross-Shaped Profile

At present, a fundamental knowledge of the thermal and mechanical interactions occurring during the extrusion of magnesium is lacking. This acts as a serious technological barrier to the cost-effective manufacturing of lightweight magnesium alloy profiles. In the present research, a three-dimensional finite element (FE) simulation of extrusion to produce a magnesium alloy profile with a cross shape was carried out as an efficient means to gain this understanding. It revealed the redistribution of temperatures in the billet throughout the process from the transient state to the steady state, the formation of the deformation zone and dead metal zone, and varying fields of effective stress, effective strain, effective strain rate, and temperature close to the die orifice. The predicted extrudate temperature and extrusion pressure were compared with experimental measurements. The key to controlling the extrudate temperature and extrusion process was found to lie in the capabilities of predicting the temperature evolution during transient extrusion, as affected by extrusion conditions. The relationship between ram speed and the extrudate temperature increase from the initial billet temperature was established and experimentally validated.

Prediction and verification of temperature evolution as a function of ram speed during the extrusion of AZ31 alloy into a rectangular section

3D computer simulations of extruding a wrought magnesium alloy AZ31 into a rectangular section at various ram speeds were performed and the results verified in extrusion experiments under identical conditions. It has been found that during upsetting and transient-state extrusion, the temperature in the billet is redistributed all over; it increases in the deformation zone close the die orifice and decreases in the rear part of the billet. The maximum temperature is located at the centre of the outer surface of the extruded section where more heat is generated and less heat lost. The minimum temperature occurs at the edge of the billet in contact with the container and the die face where the dead metal zone is situated. During upsetting and transient-state extrusion, the maximum temperature increases significantly, while during steady-state extrusion it only changes slightly. The amplitude of the extrudate temperature increase from the initial billet temperature during steady-state extrusion at a given ram displacement decreases as ram speed increases. Thus, the higher ram speed, the smaller the effect of ram speed on temperature increase. The increase of the extrudate temperature varies linearly with logarithmic ram speed. With this relationship established, the extrudate temperature at different ram speeds can conveniently be predicted.

A non-steady state FE analysis of Al tubes hot extrusion by a porthole die

Porthole die extrusion has a great advantage in the forming of hollow sections of Al alloy tubes that are difficult to produce by conventional extrusion with a mandrel fixed at the stem. In general, the porthole die extrusion process consists of three stages (dividing, welding, and forming stage) through the complex die structure composed of container, porthole, mandrel, welding chamber and bearing part. Thus, in order to obtain the detailed mechanics, to assist in the design of proper die shapes and sizes, and to improve the quality of products with high welding strength, porthole die extrusion should be analyzed in as non-steady state as possible. This paper analyzed porthole die extrusion processes through 3D FE simulation in the non-steady state during the entire process for following process variables: initial billet temperature, bearing length, tube thickness, and extrusion ratio. The extrusion load for each stage, the welding pressure, and the dead metal zone in the welding chamber were examined through a numerical analysis. Extrusion loads found by FE simulation were compared with experimental results. The surface state of extruded products was also examined. Whole investigations were made for Al7003.

均一加熱ビレットを用いた等温押出し

Isothermal extrusion is a method of maintaining constant temperature of an extruded section in the bearing zone of the die in order to get a high steady qualities in mechanical properties. Isopressure extrusion is a method of maintaining the load on the die constant throughout the ram stroke in order to get a high steady qualities in dimensions of extruded sections. In this study, an equation for calculating the initial billet temperature that performs isothermal and isopressure extrusion is proposed and confirmed. The idea is derived from the concept that the heat flow from the billet to the container is made to be equal to the heat generation by the shearing deformation of metal close to the container wall. Applying an adequate initial billet temperature obtained from the simple equation, constant temperature and constant die load have been achieved and excellent steady dimensions and mechanical properties have been obtained from the isothermal and isopressure extrusion.

The hot extrusion reaction synthesis of nickel aluminide alloys

Elemental powder compacts of Ni–13.3 wt.% Al, the composition that corresponds to stoichiometric Ni3Al, have been processed by hot extrusion reaction synthesis (HERS) to form a dense rod. A narrow processing window has been determined for the experimental scale rig used. The success of the processing route has been shown to be highly dependent on the initial billet temperature, the heating time of the billet, and the extrusion speed. HERS has been successful at relatively low processing temperatures (less than 600 °C) and offers a highly economical method of producing aluminide extrusions. The extruded microstructure consisted of a mixture of ordered gamma prime precipitates in a Ni-rich matrix and grains of twinned martensite. Both a {200} texture and a weaker {111} texture were observed along the extrusion direction. The Vickers hardness of the extruded material was 340 kgf /mm2. The 0.2% compressive yield stress at room temperature at a constant strain rate of 10−3 s−1 was 600 MPa.

Nature of friction in extrusion process and its effect on material flow

This investigation focuses on simulation of the extrusion process and in particular the effect of the initial billet temperature on friction and its consequences on material flow. The simulation is compared with data obtained from an experimental extrusion press. All the simulations are performed with the implicit finite element codes FORGE2 and FORGE3. The effect of the initial billettemperature on the deformation zone pattern and its consequent effect onfriction using bothnumerical simulationandexperimentalworkare presented.A comparison withexperimentsis made to assess the relative importance ofsome extrusion parameters in the extrusion process and to ensure that the numerical discretisation provided a true simulation of the process. A specific functional relationship to directly measure interfacial friction under conditions approaching those encountered in the quasi-static deformation process is described. The results revealed that the friction factor increases with increase in initial billet temperature and varies from 0.65 at 300 ° C to a 0.91 at 450 ° C after reaching the peak pressure. The dead metal zone is observed to vary in form and has a greater volume at high temperatures. The increase in friction results in an increase of initial extrusion load. The finite element program appears to predict all the major characteristics of the flow observed macroscopically.