Billet Temperature Research Articles

The effects of billet temperature on compound extrusion of magnesium alloy by three-dimensional finite element modeling and experiments

Extrusion–shearing of magnesium billets is associated with large deformations, high strain rates and high temperatures, which could result in many difficulties in process. Thermo-mechanically coupled three-dimensional finite element simulations of extrusion–shearing wrought magnesium alloy AZ31 into small rods at certain speed have been performed, and computed parameters including workpiece material characteristics and process conditions (billet preheated temperature, extrusion ratio, ram speed, friction factors and heat transfer coefficients) have been taken into consideration. The temperatures and stress and strain rates of extrudates with different billet preheated temperature have been calculated by finite element method software DEFORM-3D. A series of extrusion–shearing experiments and microstructure observations have been done to perform tests in order to validate the finite element method simulation results at different preheated temperatures of billets. Surface defects of rods for magnesium alloys extruded by the extrusion–shearing extrusion have been observed and analyzed. The influences of preheated temperature on the microstructures and the causes have been given. Finite element method software DEFORM-3D has been used successfully to simulate the temperatures and stress and strain rates under three different extrusion conditions. The results of these simulations helped to understand the formation of surface defects in the surface of extrusion–shearing rods. These results could assist in improving quality of extrusion–shearing extrusion.

Prediction of grain size and yield strength of Mg-7Sn-1Al-1Zn alloys extruded at various temperatures and speeds

This paper analyzed the relationships between the extrusion conditions, grain size, and yield strength of an Mg-7Sn-1Al-1Zn alloy, which was extruded at different initial billet temperatures and ram speeds, and developed empirical models to predict the grain size and yield strengths. The results revealed that grain size increases as the extrusion temperature and ram speed increase, resulting in a decrease of the tensile and compressive yield strengths due to reduced effect of grain boundary strengthening. It was also found that the exit temperature is a key determinant of grain size and yield strength, i.e. as the exit temperature decreases, the grain size decreases while the tensile and compressive yield strengths increase. The grain size and yield strength prediction models, which provide results as a function of temperature and strain rate, were developed by considering the extrusion temperature and speed dependencies of the exit temperature, and the predicted results showed a good agreement with the experimental data.

A Grey-based Taguchi Method to Optimize Hot Forging Process

In this study, Three dimensional finite element analysis has been carried out using FEM based DEFORMTM 3D software on hot forging of spring saddle. The influence of design parameter viz. flash thickness and process parameters viz. billet temperature, die temperature and friction coefficient along with their interactions are investigated for the responses forging load and billet temperature loss during hot forging operation using Taguchi's L27 orthogonal array. Analysis of variance (ANOVA) is employed to determine significant parameters. It has been observed that optimal factor settings for each performance characteristic are different. Flash thickness and Billet temperature and interaction of flash with billet temperature are observed as the most significant parameters affecting the responses. In order to minimize two responses simultaneously, Grey Taguchi method is adopted and optimum factor levels have been reported. Optimization of the process parameters simultaneously leading to a low billet temperature loss along with a low forging load and it is also verified through a confirmation experiment for validation of these results. Confirmatory results prove the potential of Taguchi design of experiments, ANOVA analysis and Grey Taguchi method in Multi-objective optimization of process parameters.

The Temperature Field Measurement of Billet Based on Multi-Information Fusion

In the continuous casting process, the internal temperature of billet is difficult to be measured and the surface temperature of billet is also difficult to be measured accurately. The steady-state heat transfer models can only be used for simulating the steady-state casting operations in off-line. For better control over the whole continuous casting cycle, recently more attention have been paid to developing real-time heat transfer models which are valid under casting condition varying frequently. Considering the heat transfer coefficient is the precondition of solving the model, and it is difficult to be measured directly. An identification method of heat transfer coefficient based on genetic algorithm was developed. According to the measured temperature and shell thickness, the heat transfer coefficient of each spray zone was determined. In order to test the dynamic performance of the real-time heat transfer model, the surface temperature was measured using the CCD (charge coupled device) temperature measurement system, which can effectively eliminate the impact of the scales on the billet surface and keep the fluctuation of the measured surface temperature within the range of ±10°C. The temperature field measurement of billet was realized by the multi-information fusion of CCD temperature measurement system, measured shell thickness and data acquisition system. This provides the possibility to improve the existing cooling system based on the feed-back control considering the measured surface temperature.

NON-UNIFORM WATER FLUX DENSITY APPROACH APPLIED ON A MATHEMATICAL MODEL OF HEAT TRANSFER AND SOLIDIFICATION FOR A CONTINUOUS CASTING OF ROUND BILLETS

In the present work, the water flux densities of nozzles with flat jet and full cone jet were experimentally measured using an apparatus in industrial scale that reproduces the secondary cooling of the continuous casting of round billets of Vallourec Tubos do Brasil. A mathematical model for heat transfer and solidification for the continuous casting of round billets was developed applying the experimental water flux density profile, establishing a non-uniform water distribution approach. The mathematical model was validated by experimental measurements of the billet superficial temperature, performed at the industrial plant. The results of the mathematical model using both uniform and non-uniform water flux density approaches were compared. The non-uniform water distribution approach enabled to identify important variations of the heat transfer coefficients and the billet temperatures, especially in the first cooling zone, and to assess more accurately the local effects of the water distribution on the thermal behavior of the strand. The non-uniform water flux density approach applied to the mathematical model was a useful and more accurate tool to improve the comprehension of the thermal behavior of the steel along the secondary cooling

Design and application of dynamic secondary cooling control based on real time heat transfer model for continuous casting

The control of secondary cooling is extremely important for the quality of billet in the continuous casting. In order to minimise the variation in surface temperature and excessive reheating of billet, which have a considerable influence on the formation of cracks and other defects, a real time heat transfer model that can be used for simulation of varying casting operations was developed. In order to verify the dynamic performance of this model, a charge coupled device temperature measurement system that can eliminate the impact of the scales was presented. The actual shell thickness profile and billet temperature were calculated in real time by this model online and were taken into account to feedback control the casting process based on the desired target cooling pattern to improve the existing cooling system. The dynamic control system based on this model was developed and implemented on some caster, and the billet quality was obviously improved.

Using Soft Material as Die during Hot Forging

This study introduces a new forming concept for hot forging by using soft die. The soft die (AISI1050) was employed not only to heating the billet, but also to forming the billet. In this proposed method, the soft die can be used as the electrode to raise the temperature of billet directly by resistance heating. The temperature of the billet is higher; the flow stress of the billet is become lower. Then the billet is easier to press into the cavity of the soft die. In addition, the soft die itself could not be heated by the electrifying and the temperature raise of soft die was occurred by the heat transfer from the heated billet. Therefore, the soft die can be carried out on hot forging process, and to achieve the purpose of forming. The result of experiments shows that the billet could be heated quickly to 1000°C in about 5 seconds, and a spur gear was successfully formed. With the proposed method, it was simple enough to hot forging high-alloy metals with poor workability.

Heating characteristics of billet in a walking hearth type reheating furnace

The heating characteristics of billet in a walking hearth type reheating furnace were studied by developing a mathematical heat transfer model. Radiation calculations were conducted by means of zone method and considering all radiation exchange paths. The weighted-sum-of-gray-gas-model was used for better accuracy of gas radiation prediction. Convective heat flux was calculated by considering suitable value of convective heat transfer coefficient at any location of the furnace. The model was substantiated through its comparison to experimental data. A comparison was drawn to evaluate the effect of constant and variable convective coefficient on convective flux distribution and billet thermal behavior. The effect of furnace wall's emissivity of each zone and whole of the furnace on the billet thermal behavior was investigated. The obtained results revealed that by increasing furnace wall's emissivity for a determined residence time, billet's temperature in primary zones rises but it has no significant effect on its final temperature. However, by increasing wall's emissivity from 0.7 to 0.95, the residence time can be declined by about 5%. Moreover, emissivity increase in non-firing and preheating zones as compared to heating and soaking zones has greater impact on the billet thermal behavior.

Effects of Extrusion Parameters by KoBo Method on the Mechanical Properties and Microstructure of Aluminum

Abstract Commercial purity aluminum was extruded by means of KoBo method at varied processing parameters. Received extrudates, with different mechanical and electrical properties and work hardening behavior, were obtained. It was found, that some conditions of KoBo extrusion process such as low initial billet temperature, low extrusion rate and low frequency of oscillating die lead to extremely high strength and high electrical resistivity of the material. The absence of work hardening (up to 40% strain) during subsequent groove rolling is also a specific feature of received materials. It was suggested that mentioned features are related to the development of overbalance concentration of point defects (clusters) generated during the extrusion process. During following cold rolling of the extrudate, mentioned defects annihilate at gliding dislocations and make the dislocation climbing and their rearrangement easier. Therefore, until the exhaustion of this mechanism, the hardening of material during cold rolling is very limited. Following increase of the material strengthening at higher rolling strains point to the return of the material to its typical behavior observed for cold deformed aluminum produced by conventional hot extrusion.

Steel Billet Continuous Induction Heating – Numerical Model and Advanced Control

Nowadays, the achievement of proper steel billets temperature profile is not the only design priority of induction heaters for hot forming applications. Due to its high operating costs, its design is constantly improving in terms of electrical and thermal efficiency. Therefore the more efficient multi-coil design starts to be more used in industrial practice. Numerical model of mentioned heater based on partial differential equations were solved by finite element method in virtual software environment. Primary goal of computer modeling was to investigate the thermal dynamics of four-module heater working in steady-state operation regime. Obtained data were applied to design an advanced control circuit based on distributed parameter systems theory. This may open up the opportunity to make further progress in induction heaters design.

Application of ANOVA and Taguchi-based Mutation Particle Swarm Algorithm for Parameters Design of Multi-hole Extrusion Process

This study presents the Taguchi method and the Particle Swarm Optimization (PSO) technique which uses mutation (MPSO) and dynamic inertia weight to determine the best ranges of process parameters (extrusion velocity, eccentricity ratio, billet temperature and friction coefficient at the die interface) for a multi-hole extrusion process. A L 18(2 1 ×3 7 ) array, signal-to-noise (S/N) ratios and analysis of variance (ANOVA) at 99% confidence level were used to indicate the optimum levels and the effect of the process parameters with consideration of mandrel eccentricity angle and exit tube bending angle. As per the Taguchi-based MPSO algorithm using DEFORM TM 3D Finite Element Analysis (FEA) software, the minimum mandrel eccentricity and exit tube bending angles were respectively calculated to be 0.03°, which are significantly less than those based on Genetic Algorithm (GA) and the Taguchi method, respectively. This indicates that the Taguchi-based MPSO algorithm can effectively and remarkably reduce the warp angles of Ti-6Al-4V extruded products and the billet temperature is the most influencing parameter. The results of this study can be extended to multi-hole extrusion beyond four holes and employed as a predictive tool to forecast the optimal parameters of the multi-hole extrusion process.

Non-contact charge temperature measurement on industrial continuous furnaces and steel charge emissivity analysis

Continuous furnaces are commonly used for steel billet reheating before a rolling operation. It is necessary to perform a number of measurements to set-up and operate the optimization system of the furnaces correctly. A charge temperature measurement using infrared detectors can be one of the usable measurement techniques. This non-contact measurement method is based on the detection of infrared radiation emitted from a measured surface. The radiation intensity depends on the surface temperature and emissivity, which is one of the most important parameters for infrared measurements. Advantages of the non-contact temperature measurement, as well as some problems regarding the surface emissivity, are presented. The direct steel billet temperature measurement procedure using infra-red detectors, emissivity determination procedures, and example results are introduced. It is shown that steel emissivity can vary from approx. 0.17 to 0.8, depending on the surface state, scale formation, and wavelength interval. These problems are critical for the charge temperature measurement using the infra-red detectors, and are discussed in this paper.

Die Stress Optimization Using Finite Element and Taguchi Method

In this study, finite element simulation and the Taguchi method are employed to optimize the die stress in hot closed die forging process. Investigations are carried out for forging of automotive spring saddle by including all realistic process parameters. The research involved analyzing the effects of flash thickness, billet temperature, die temperature and friction coefficient on effective die stress by means of computer simulation. To obtain the result the forging process was modeled in CATIA V5, 3D Solid Modeling Software, simulated in DEFORMTM 3D Software, and statistically setup and examined using Taguchis orthogonal array. Analysis of variance (ANOVA) is employed to determine significant parameters.

Microstructural Evolution in Multiway Loading-Forming Process of AISI 5140 Steel Triple Valve Body

The microstructural evolution and distribution rules, such as dynamic recrystallization (DRX) volume fraction, dynamically recrystallized grain size, and average grain size, in multiway loading-forming process of AISI 5140 steel triple valve body have been investigated using numerical simulation, combined with the analytic method by considering the influences of process parameters including loading speed of punch, initial temperature of billet, and friction. The results show that the DRX volume fraction increased, and its distribution became more uniform with the increases of punch loading speed and billet initial temperature, or the decrease of friction factor; the dynamically recrystallized grain size decreased, and its distribution was more uniform, with the increases of punch loading speed and friction factor, or the decrease of billet initial temperature; the average grain size decreased, and its distribution became more uniform with the increases of punch loading speed and billet initial temperature, or decrease of friction factor.

Study of seamless tube extrusion of SiCp-reinforced AZ61 magnesium alloy composites

This study involves the investigation of the mechanical properties of the extruded tube products with reinforced silicon carbide particulates (SiCp). Finite element analyses are firstly conducted to analyze the plastic flow of the magnesium alloy AZ61 within the die and to investigate the effects of initial billet temperatures on the extrusion loads and final product temperatures. AZ61/SiCp composite ingots reinforced with different weight fractions of SiCp are fabricated by a melt stirring technique. A specially designed die set is used in the extrusion experiments to obtain tubes with uniform thickness distribution in the circumferential direction. The extruded tubes are also heat treated to obtain even better mechanical properties. Finally, tensile tests, Vickers microhardness, tests and microstructure observation are performed on the billets and extruded tubes of AZ61 monolithic alloys and AZ61/SiCp composites. A much smaller grain size and higher tensile strength and hardness are achieved for the extruded AZ61/SiCp composite tubes.

Evaluating the effects of process parameters on maximum extrusion pressure using a new artificial neural network-based (ANN-based) partial-modeling technique

Metal extrusion process accounts for the production of the majority of industrial and domestic aluminum sections. A major limitation to the success of any extrusion operation is the capability of the particular extrusion press to meet the maximum pressure requirements for that operation. In the present work, the effects of industrial extrusion process parameters and their interactions on the resulting maximum extrusion pressure, of an industrially extruded aluminum alloy, have been studied using a newly devised ANN-based partial modeling technique. 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. The main objective for developing this modeling technique is to overcome the limitations of presently available statistical modeling tools, as foreseen by the modeling needs for a complex thermo-mechanical process such as extrusion. The main present limitations are accounting for non-linearity in the process behavior, incorporating interaction effects and a meaningful determination of the highly significant process parameters and/or interactions. These three features have been, collectively, incorporated into the present model by means of combining statistical analysis of variance into ANN and by using a partial sum of squares analysis, which we propose to call the “present factor analysis.” Normal linear regression has been also employed for comparison purposes. According to the present model, maximum extrusion pressure has shown various degree of non-linearity in behavior with respect to the different process parameters and their significant interactions. It has been found that variations in the maximum extrusion pressure are mainly a function of initial billet temperature and its interactions with other process parameters, especially the ram speed. The present ANN-based model has shown superior prediction capabilities compared to the linear model with a marginal overall prediction error value of ±2.5 %.

Effect of Process Parameters on Die Wear Behavior of Aluminum Alloy Rod Extrusion

In this article, a subroutine that calculates die wear depth based on modified Archard's wear model was developed and then embedded into DEFORM-3D, with which the extrusion process of an aluminum alloy 7075 rod was simulated. Useful information was obtained from the numerical simulation, including interface pressure, distribution of instantaneous temperature, required extrusion force, die wear depth, etc. The numerical result shows that extrusion parameters have multiple effects on die wear behavior. The severest die wear occurs at the bearing entrance due to the greatest deformation, highest pressure, and temperature in this area. It is found that ram speed has no single tendency on die wear, while die wear depth rises with the elevated initial temperatures of billet and extrusion tooling. In addition, the required extrusion force has strong dependence on extrusion parameters. The extrusion force rises clearly with an increase of ram speed and a decrease of initial temperatures of billet and extrusion tooling, which is totally accordant to practical observation. Therefore, the study in this work could provide useful and helpful guides for selecting reasonable extrusion variables, predicting die life and reducing production cost.

Microstructure and mechanical properties evolution of 6061 aluminum alloy formed by forward thixoextrusion process

Thixoforming process is a semisolid metal processing route, which involves forming of alloys in the semisolid state to near net shaped products. To investigate the effects of thixoextrusion parameters on microstructure and mechanical properties of commercial 6061 aluminum alloy, forward extrusion experiments were carried out in the semisolid state. The results showed that fine and globular microstructure can be achieved using semisolid forming. SEM micrographs and mechanical tests results showed that the tensile behavior of thixoformed specimens at billet temperatures below 620°C is relatively elastic and brittle. With increasing die temperature up to 620°C more elongation value and ductility were obtained in the thixoformed specimens.

The Effect of Temperature Condition on Material Deformation and Die Wear

The characteristics of temperature change on die and billet are very complex during the deformation process because of the interaction between them and some unstable external factors. In this paper, the numerical simulation model for the crank shaft die forging was established by means of the rigid-plastic FEM method. The model was validated by optical non-contact 3D measurement—ATOS. Based on available research results, this paper explored the effect of temperature conditions on material deformation and die wear. Three parameters, press velocity and initial temperature of billet and die, were chosen to illustrate the effects. From the experimental results, the effect of process parameters on deformation ability of the material is simple, while the effect on die wear is relatively complicated. The press velocity plays an important role on die wear when the initial temperature of the billet has larger influence on material deformation. A conclusion can be drawn that when the initial temperature of the billet is 1100 °C, the initial temperature of the die is 250 °C, and the velocity is kept in the range of 200-300 mm/s, the optimum solution for deformation ability of the material and die wear can be obtained. It is possible for the conclusion to be extended further for the control of temperature condition to optimize die life and material deformation.

Three Dimensional Transient Explicit Finite Difference Heat Transfer Modeling of Billet Transport

In steel industries the billets are heated in reheat furnace. The billets coming out from reheat furnace are transported to the rolling mill. Prediction of billet temperature during transport is vital for several reasons, like energy optimization studies, process simulation, roll force calculation and quality of the final product. Inadequate temperature measuring instruments demands suitable model for billet temperature predictions. In the present work, conduction heat transfer within the billet is modeled using the explicit finite difference method. To solve three dimensional transient discretization equations, code has been developed and implemented in MATLAB ® . Validation of the proposed numerical model has been done using analytical solutions. The model predictions of billet temperature are shown to be in good concurrence with analytical results. The model is capable of predicting temperature distribution within the billet. The model is used to examine the effect of billet transport velocity on the temperature field of the billet. The objective of this work to apply simple simulation technique to high temperature industrial process for temperature field measurements. This type of simulation may be useful for temperature predictions, design and study of new or existing transport system for hot billet transport.