Initial Billet Temperature Research Articles

Microstructure Responses to Key Extrusion Parameters of Large-Scale Thick-Walled 304 Stainless Steel Pipes Extrusion

Abstract A finite element (FE) model for the extrusion process of large-scale thick-walled 304 stainless steel pipes was firstly developed based on DEFORM-2D platform, which can predict the DRX evolution behavior by coupling with a DRX model of 304 stainless steel. Secondly, the influence of the above key extrusion parameters on the average grain size and the grain uniformity of the extruded pipe were investigated by a liner orthogonal regression method. Finally, the influence laws of the key parameters on the average grain size and the grain uniformity were analyzed by a single factor method. The results show that extrusion speed V, initial billet temperature Tb and extrusion ratio λ have more obvious effects on the average grain size and the grain uniformity than other ones, and the influence sequences of these parameters to the average grain size and the grain uniformity are Tb>λ>V and Tb>V>λ, respectively. And the average grain size becomes smaller and the grain uniformity gets enhanced with the decrease of V and the increase of Tb and λ.

Study on exit temperature evolution during extrusion for large-scale thick-walled Inconel 625 pipe by FE simulation

The extruded large-scale thick-walled pipes made from Inconel 625 alloy are widely used in many fields such as in the oil and chemical industry, thermal power generation, nuclear power plant, aerospace, and defense industry. However, the nonuniform distribution of grain size along the thickness and length directions of the extruded pipe always appears, which has a great influence on the mechanical property and uniformity of the pipe. The inhomogeneous distribution of the exit temperature in the entire extrusion process is the decisive factor leading to the grain nonuniformity of the extruded pipe. Therefore, it is necessary but difficult to reveal the evolution of the exit temperature under some key extrusion parameters in order to effectively control the exit temperature uniformity. In this paper, a thermomechanical coupled finite element (TMC-FE) model, which can precisely predict the hot deformation behavior of the extrusion process for large-scale thick-walled Inconel 625 pipe, has been firstly developed based on the DEFORM-2D platform. And then, the influence of key extrusion parameters, namely extrusion speed (V), initial billet temperature (T b), extrusion ratio (λ), and friction (μ), on the exit temperature was revealed by comprehensive simulations. In addition, using the standard deviation of exit temperature (SDexit) as the measure indicator of the exit temperature uniformity, we also disclosed the influence of the key process parameters on the exit temperature uniformity in detail. The results show that with the increase of V, T b, and μ, the uniformity of exit temperature in the entire process firstly becomes better and then gets worse. The larger λ can result in a more uniform exit temperature. In consideration of the obtained results, within the feasible window of the key extrusion parameters defined in this paper, the conditions of T b = 1,100–1,150 °C, V = 125–150 mm/s, μ = 0.015–0.02, and a larger extrusion ratio (λ) are suggested for the extrusion of large-scale thick-walled Inconel 625 pipe in order to get more uniform exit temperature.

Lüders effect in Al 99.7% extruded via the KoBo method

Abstract The aim was to determine the effect of extrusion process parameters of the KoBo method (initial billet temperature, extrusion rate and die oscillation frequency) on the Lüders phenomenon occurrence in aluminum wires. The material used in the experiment was 99.7% pure Al billet. The extrusion was carried out with the following parameters: extrusion ratio λ = 100, initial billet temperature in the range of 293–493 K, extrusion rate of 0.1–0.5 mm · s−1 and frequencies of 3, 5 and 8 Hz (the die oscillation angle was a constant ± 8°). Output materials were mechanically tested and examined microscopically. Based on the results it was found that: the Lüders phenomenon in aluminum wires extruded by the KoBo method appears only i) in a specific range of the extrusion force, namely 450–650 kN, ii) a specific range of, yielding strength (100–140 MPa), iii) dependent on the combination of process parameters its extent and position can vary over a product's length, iv) tests have also shown that this phenomenon has a continuous propagation nature only at the initial stage of the tensile test.

Extrusion-shear of AZ31 alloy billets with low temperature and high speed by using three-dimensional finite element modeling and experiments

A new kind of compound extrusion technology including direct extrusion and shears for AZ31 magnesium billets can cause plastic large deformations and high strain rates. A series of compressive tests have been done to obtain the stress-strain curves of AZ31 magnesium alloy. Three-dimensional (3D) thermo-mechanical coupled finite element modeling of forming magnesium alloy AZ31billets into small rods at certain high ram speed and low temperature by extrusion-shears have been carried out. The simulation model has been established and meshed based on symmetrical characteristic. Computed parameters including material characteristics for workpiece and die and process conditions consisting of initial billet temperature, extrusion ratio, channel angle and ram speed have been list. The evolution of temperature during extrusion-shear process, there are hardly any temperature gradients within the workpiece, but temperature in severe plastic deformation zone increase rapidly. Strain evolutions for inner billet are larger than those of border positions. The flow velocity distribution is uniform basically which avoid the extrusion cracks to a certain degree. Experiments show that the rods with good surface smoothness can be obtained by low temperature and high speed extrusion-shear, and the alloy grains are effectively refined by dynamic recrystallization (DRX).

Computer Aided Design of Wires Extrusion from Biocompatible Mg-Ca Magnesium Alloy

Abstract Mathematical model of small-diameter wires extrusion from biocompatible MgCa08 (Mg - 0.8% Ca) magnesium alloy was developed in the current paper in order to determine window of allowable technological parameters. Compression and tensile tests were carried out within temperature range 250-400°C and with different strain rates to determine the fracture conditions for the studied alloy. Finite element (FE) analysis was used to predict the billet temperature evolution and material damage during processing. The extrusion model takes into account two independent fracture mechanisms: a) surface cracking due to exceeding of the incipient melting temperature and b) utilization of material formability. FE simulations with different initial billet temperatures and pressing speeds were performed in order to determine the extrusion limit diagram (ELD) for MgCa08 magnesium alloy. The developed ELD was used to select the parameters for the direct extrusion of wires with diameter of 1 mm. Then, the extrusion of twelve wires was conducted at 400°C with pressing speed 0.25 mm/s. It was reported that the obtained wires were free from defects, which confirmed the good agreement between numerical and experimental results.

Research on rolling–extrusion forming of variable wall thickness cylinder parts

The rolling–extrusion technique for the mass production of variable wall thickness cylinder parts is put forward to reduce the machining time and increase the material utilisation. In this process, material is formed by means of three passive rotational tools. The charge is provided by means of a pusher pushing the billet in a working space between the profiled rolls. A coupled thermal-mechanical rigid viscoplasticity FEM model for rolling–extrusion of variable wall thickness cylinder parts is developed based on the DEFORM-3D software. Then the distribution of effective strain field, temperature filed and the load during the rolling–extrusion forming process are discussed. Moreover, the influence of process parameters on the deformation uniformity is analysed, and the results show that the deformation non-uniformity of billet increases with increasing punch speed and friction factor or decreasing initial temperature of billet. In physical experiment, the press machine and a simple machine for rolling–extrusion are used to work out the parts .The results of these tests show the parts can be produced accurately by using rolling–extrusion technique. Compared with the traditional method, the material utilisation is increased by 19% with the machining time greatly reduced.

Radial forging force prediction through MR, ANN, and ANFIS models

The application of finite element method and intelligent systems techniques to predict the applied force during the radial forging process is studied. Radial forging is a unique process used for the precision forging of round and tubular components, with or without an internal profile. More than 800 radial forging machines are currently operating worldwide. Since the maximum forging force per die is constant, determining the die force before the process can prevent die damage and material wastage. Then, the results of the FE simulation are applied for two intelligent forecasting systems in artificial neural network and adaptive neuro-fuzzy inference system. Initial billet temperature, die inlet angle, feed rate, and reduction in cross-section are applied as input parameters, and radial forging force is applied as the output parameter. Finally, the results of these two intelligent systems are compared with the multiple regressions method. A sensitivity analysis is carried out to determine how the radial forging force is influenced by the input parameters.

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.

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.

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 %.

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.

銅合金の押出し加工におけるビレット表層流れの FEM 解析

The flow of a billet surface inserted into the profile during the extrusion of Cu alloy has been investigated by the finite element method under several extrusion conditions. The billet surface material is inserted into the profile in two ways. We have defined the forward flow into the profile surface as Flow type 1, and the flow into the inner parts of the profile as Flow type 2. These lengths of insertion into the profile have been estimated. In the initial billet temperature range of 500-800℃, the higher the temperature, the larger is the insertion length of Flow type 1, and the shorter that of Flow type 2. The insertion length of Flow type 1 increases because the deformation resistance of the billet surface increases when the initial billet temperature is higher than the container temperature. For extrusion ratios of 11-42, the higher the extrusion ratio, the larger is the insertion length of Flow type 1, and the shorter that of Flow type 2. The insertion length of Flow type 1 decreases because the length between the billet surface and the profile is large when the extrusion ratio is high.

The effects of special extrusion on the grain refinements of magnesium alloy

To research the effects of extrusion process and its process parameters on evolutions of microstructures for magnesium alloy, and the process includes initial extrusion and subsequent shearing process and is shorten for 'ES'. The simulation models have been built by using the DEFORM software. Temperature and strain evolution for deformation varying with initial billet temperatures has been explored. An experimental extrusion with installed container and ES die has been constructed. The maximum temperature rises in the billets are not increasing with billet temperature rise. The temperatures of rod surface increase continuously with development of ES extrusion. ES processes can improve microstructure refinement of AZ31 magnesium alloy. The simulation results and microstructure observation show that ES process can introduce compressive and accumulated shear strains into the magnesium alloy and improve the dynamic recrystallisation during ES extrusion. The research results show that ES is an efficient and inexpensive grain refinement method for magnesium alloys.

Dynamic recrystallization rules in needle piercing extrusion for AISI304 stainless steel pipe

The dynamic recrystallization (DRX) rules are the significant foundation for the effective control of DRX behavior, consequently achieving fine grains and qualified microstructure in the needle piercing extrusion for AISI304 stainless steel pipe. A reliable multi-scale FE model was developed for the extrusion process of seamless AISI304 stainless steel pipe (d29 mm×4.5 mm) under the DEFORM-2D software environment, and then the influence rules of the key extrusion parameters were numerically unfolded, namely the initial billet temperature and extrusion speed, on the DRX volume fraction, average grain size and their distributions by comprehensive simulations. The outcome establishes the basis and guidelines for the optimal design and steady control of the extrusion process in terms of the microstructure of the extruded pipe.

Temperature Field and Extrusion Load in Needle Piercing Extrusion Process Based on Ingot Billet for Large 7075 Aluminum Alloy Tube

Abstract. The change rules of the billet temperature field and extrusion load are the significant basis for the optimal design of the needle piercing extrusion process based on ingot billet for the manufacture of large-diameter thick-walled tube. Taking the needle piercing extrusion process of a 7075 aluminum alloy tube with sizes of Φ500mmx400mm/6000mm as study object, we developed a precise FE model for the process under DEFORM-2D environment, then numerically revealed the distributions and evolution rules of the billet temperature field, and obtained the effects of the extrusion speed and initial billet temperature on the billet temperature filed and extrusion load. The results show that the peak extrusion load decreases linearly with the increase of initial billet temperature but is insensitive to the extrusion speed, and that the peak temperature rises with the increase of the extrusion speed and initial billet temperature, and always locates on the surface of the initially extruded tube close to the exit of the cavity die.

Study on the Formability and Friction of Hot Forging Process of a Spur Gear Shaft for Manufacturing Engineering

Hot forging processes of a spur gear shaft with three billet sizes are simulated using FEM. The billet with size of φ36*60 has the best formability in hot forging the spur gear shaft. The effects of the initial billet temperature and the friction coefficient on the hot forging formability of the spur gear shaft are obtained respectively through simulation. Hot forging experiments are carried out and experimental results show good agreement with those in simulation. At last, the reasonable hot forging parameters of the spur gear shaft for manufacturing engineering are suggested as follows: billet size of φ36*60, billet initial temperature of 1050°C and friction coefficient of 0.3.

FE analysis on Deformation and Temperature Nonuniformity in Forming of AISI-5140 Triple Valve by Multi-Way Loading

In triple valve forming process by multi-way loading severely nonuniform deformation and temperature distributions are prone to occur, which may lead to poor forming quality and macro-micro defects. A 3D coupled thermo-mechanical rigid-viscoplastic finite element (FE) model for multi-way loading forming of AISI-5140 steel equal diameter triple valve was developed based on DEFORM-3D. Through comprehensive simulation and analysis, the influences of main process parameters on the forming process and nonuniformity of deformation and temperature were studied. The results showed that: (1) the degree of deformation nonuniformity decreased with the increase of the punch loading speed, initial temperature of billet, or the decrease of the friction factor; (2) the average temperature of forming body increased as the punch loading speed, initial temperature of billet and the friction increased, while the degree of temperature nonuniformity decreased with the increase of punch loading speed or decrease of initial billet temperature.

Numerical Simulation on Thixocasting Process of Auto Box-Like

Semi-solid metal processing (thixoforming) is a potential forming technology, which can realize near-net-shape forming process with good quality in one forming step. In this study, semi-solid casting (thixocasting) was used to form the auto box-like. Based on Power Law Cut-Off (PLCO) model and finite element code Procast software, the thixocasting process was modeled and simulated. The impact of main process parameters such as initial billet temperature, ram speed as well as die temperature on the thixocasting process was studied. The results show that thixocasting process can be used in forming auto box-like.