Initial Billet Temperature Research Articles

Prediction of Recrystallization Structure of 2A12 Aluminum Alloy Pipe Extrusion Process Based on BP Neural Network

2A12 aluminum alloy is a high-strength aerospace alloy. During its extrusion process, the extrusion process parameters have a great impact on the microstructure evolution of the extruded products. There are three extrusion process parameters controlled in the actual project, which are the initial temperature of billet, the initial temperature of die and the extrusion speed. Combined with a back propagation (BP) neural network and finite element method (FEM) simulation, based on the constitutive equation and recrystallization evolution process of 2A12 aluminum alloy, this paper establishes a prediction model for the grain size of extruded pipe by these three extrusion process parameters. This paper used a 35MN extruding machine for a production verification of 2A12 pipe. The results show that the predicted grain size is 3% smaller than the actual size.

Construction of extrusion processing window for P/M nickel-based superalloy using deep neural network and its validation

Canning extrusion is an effective way to refine grains, eliminate defects from hot isostatic pressing consolidation and enhance mechanical properties of P/M nickel-based superalloy. The present research constructed the optimized extrusion processing window for superalloy in consideration of extrusion speed, initial billet temperature, and extrusion ratio to provide guidelines for the choice of extrusion parameters. The processing window was built by integrating the results of finite element (FE) simulations, extrusion experiments, and deep neural network (DNN). The peak extrusion load and temperature under different extrusion parameters were collected as input datasets by FE simulations. The DNN was trained by optimizing the learning parameters and then predicting the load and temperature over various extrusion conditions. Finally, the extrusion processing window was established, including an optimized processing zone and two instability zones. The extrusion experiments were performed to verify the reliability of the processing window, which could be able to promote the extrusion production of nickel-based superalloys with high efficiency and quality.

Process optimization for hot forging of difficult parts by computer experiments and response surface analysis

Closed die hot forging of 304L stainless steel is difficult compared to carbon and micro-alloyed steels in terms of higher forming force and defects. An appropriate combination of design and process factors including cross-section diameter, initial billet temperature, and flash land thickness is crucial to minimize the forming force without causing any under-filling or folding defects. This paper aims to develop an optimized closed-die hot forging process for long, thin, and tubular rail body components used in gasoline direct injection systems. The effects on the forging load are investigated using computer experiments containing the finite element method under a full factorial array of three factors at three levels to obtain the main and interaction effects. Linear and quadratic surface response analyses are performed to define the relation between forging load and input factors, and finally, the simulations are validated with some limited experiments. The simulation results that fit the nonlinear regression model were in close agreement with the experiments, and an optimal set of parameters is conveniently proposed for industrial production.

FINITE ELEMENT ANALYSIS OF CHROMIUM AND MOLYBDENUM ALLOYED STEEL BILLETS FORGED ON MULTI STEP PROCESS USING SIMUFACT FORMING

ABSTRACT Simufact Forming covers the complete spectrum of working on forming technologies like rolling, forging, and sheet metal forming. In this paper, finite element comparative analysis was performed on two chromium- and molybdenum-alloyed steel billets, namely 42CrMo4 and 16CrMo4 alloyed steels, using multi-step forming process of hot closed die forging process using Simufact Forming software. 42CrMo4 alloy steel is most commonly used in making of automobile components, and 16CrMo4 alloyed steels are commonly utilised in the area of ship building, airplanes, etc. While working with these materials, with the help of forging process, lot of stresses, strains and temperatures will develop. In this paper, three state variables, namely effective plastic strain, equivalent stress and temperature, for two materials at the end of multi-step forming processes like chamfering, preforming and final forging stages are evaluated and compared. In cooling process, the initial temperature of billet is maintained at 1250°C for both materials. Finally, comparative analysis of two alloyed steel billets was done by considering three-state variables.

Coupled CA-FE simulation for dynamic recrystallization of magnesium alloy during hot extrusion

In the present research, the dynamic recrystallization (DRX) behavior of a newly-developed Mg–Al–Zn–RE alloy with abundant second-phase particles during hot extrusion is investigated by coupling finite element (FE) and cellular automaton (CA) models. A two-dimensional CA model is developed to quantitatively and topologically evaluate the DRX process during deformation with constant forming conditions. Considering the fact that second-phase particles with various sizes extensively exist in the studied Mg–Al–Zn–RE magnesium alloy, models of DRX nucleation and grain growth velocity are modified. The coefficients of the modified CA model are calibrated by isothermal compression experiments of the magnesium alloy. Subsequently, the CA model is coupled with FE analysis to investigate the DRX behavior during the hot extrusions of the Mg–Al–Zn–RE alloy. The DRX behavior of the magnesium alloy at different stages and positions of extruded plates is simulated by the established model. Finer grains near the edge than in the inner of the plates result from higher strain and strain rate. The influence of extrusion conditions on microstructural evolution is explored. Under the employed forming conditions, average grain size decreases 28–62 times from as-cast and solution-treated to as-extruded state due to grain refinement by DRX. With increasing initial billet temperature or extrusion speed, average grain size increases. The finest grains are obtained at the initial billet temperature of 623 K and the extrusion speed of 7.83 mm/s. Low initial billet temperature or high extrusion speed benefits homogeneous grain distribution. The simulated results are in good agreement with experimental ones.

Crystallographic texture development in extruded AA 2195 and AA 7075

The addition of lithium to high strength aluminum alloys significantly improves specific strength as is the case with AA 2195. However, unlike non-lithium containing alloys, such as AA 7075, lithium containing alloys display anisotropic mechanical properties in low aspect ratio extruded sections. The goal of this study is to elucidate the origins of anisotropy in AA 2195 and to investigate processing methods to control mechanical properties. To this end, both AA 2195 and AA 7075 were systematically extruded over a range of aspect ratios from 2 to 15 while maintaining a constant extrusion ratio. Through crystallographic texture component analysis and the use of a newly proposed parameter termed the “Plate-Like Number”, this study indicates that the Copper texture is primarily responsible for previously observed anisotropic properties of AA 2195. A series of rolling studies analyzed using the Plate-Like Number suggest that a higher initial billet temperature will minimize the Copper texture component and thus reduce the anisotropy in extruded AA 2195.

Construction of three-dimensional extrusion limit diagram for magnesium alloy using artificial neural network and its validation

Conventional extrusion limit diagram (ELD) involves only two extrusion process variables and as such it does not account for the combined effects of multiple process parameters on the extrusion process with respect to pressure requirement and extrudate temperature. Attempts were made in the present research to construct three-dimensional (3D) ELD for a magnesium alloy in the space of initial billet temperature, extrusion ratio and extrusion speed. A method to build 3D ELD by integrating finite element (FE) simulations, extrusion experiments and artificial neural networks (ANN) was developed. In addition to initial billet temperature, extrusion ratio and extrusion speed, the temperature difference between the extrusion tooling and billet, the size of the billet and the shape complexity of the extrudate were taken as the additional process variables and integrated into the equivalent initial billet temperature, extrusion ratio and extrusion speed. The FE simulations, verified by performing extrusion experiments to produce magnesium alloy rods, were used to generate datasets for training the ANN. The ANN then predicted the peak values of extrusion pressure and extrudate temperature over a wider range of extrusion conditions, based on which a 3D ELD for the magnesium alloy was constructed. The 3D ELD was finally validated by performing extrusion experiments to produce magnesium alloy tubes. The results demonstrated that the constructed 3D ELD was reliable and able to provide guidelines for the selection of appropriate extrusion conditions.

Investigation into the Extrudability of a New Mg-Al-Zn-RE Alloy with Large Amounts of Alloying Elements

The present study was aimed at determining the extrudability of a newly developed Mg-Al-Zn-RE magnesium alloy with large amounts of alloying elements. The experimental and numerical investigation clearly showed that the extrudate temperature was a crucial factor in deciding if a critical temperature between 754 K and 768 K (481 °C and 495 °C) was reached during extrusion, above which hot shortness occurred. Under the extrusion conditions applied, dynamic recrystallization (DRX) occurred, leading to grain refinement from a mean grain size of 165 μm in the as-solid-solution-treated billet to 8.0 to 10.9 μm in the extruded rods. Second-phase particles, such as Mg17Al12 and Al11La3, were found to distribute on grain boundaries and aid in grain refinement. The mechanical properties of the extrudate were greatly influenced by the as-extruded microstructure and extrusion condition. As the initial billet temperature decreased, the ultimate tensile strength (UTS) and elongation of the alloy increased, while yield strength (YS) remained almost unchanged. At an initial billet temperature of 523 K (250 °C), a stem speed of 3.93 mm/s, and a reduction ratio of 29.8, the extruded magnesium alloy had a mean grain size of 8 μm. Its YS, UTS, and elongation reached 217 ± 3 MPa, 397 ± 7 MPa, and 20 ± 1.3 pct, respectively.

Variations on billet gas consumption intensity of reheating furnace in different production states

To achieve variations on billet gas consumption intensity (BGCI) of reheating furnace in different production states, a simplified BGCI apportionment model, which was based on the division of production states, was put forward in this paper. Firstly, production states were divided into four different modes according to the sequences of billet loading and unloading and billet number change in reheating furnace, namely, (i) normal production state (NPS), (ii) abnormal production state (APS), (iii) stop production state (SPS), which included preserving heat and waiting rolling state (PHWRS) and baking process state (BPS), (iv) transient production state (TPS), which included abnormal transient production state (ATPS) and stop transient production state (STPS). Secondly, a simplified BGCI apportionment model, which had better practicability, was established. Case study shown that the BGCI of APS or SPS was higher than that of NPS. And the longer the billet was in APS, the greater the BGCI was. Meanwhile, the initial temperature of billet and the repair time of reheating furnace had an important impact on BGCI. The results show that increasing the time of NPS is the most basic measurement in reducing BGCI. And elevation of initial temperature and reduction of the repair time are also effective measurement. And then, some suggestions and measures, which can achieve energy lean management of reheating furnace, are put forward.

Multi-field coupling finite element analysis for determining the influence of temperature field on die service life during precision-forming process of steel synchronizer ring

Failure analysis shows that increased die temperature caused by severe plastic deformation of material and heat conduction between hot billet and cavity significantly affects the distortion of gear cavity in steel synchronizer ring forging process. The forging process of steel synchronizer ring and die temperature distribution under different forging conditions are analyzed through finite element method. Simulation results show that severe plastic deformation occurs in the gear cavity. The improvement of lubrication condition results in decreased die temperature. When the initial billet temperature is high, the die temperature is also high. Increasing forging speed in a certain range facilitates the die temperature decrease. The distribution of die temperature in synthetic forming technology is more reasonable than that of one step forging. The synthetic forming technology is adopted in production to reduce the effects of severe plastic deformation caused by die temperature. The ejection mechanism and control system of the double disc friction press are improved to reduce the contact time between the hot billet and cavity. Experimental results show that synthetic forming technology is reasonable, and that the die service life is prolonged.

Effects of Mandrel Angle on Hydrostatic Extrusion Process of Magnesium Alloy Tube

Abstract The hydrostatic extrusion process of magnesium alloy AZ80 tube with different mandrel angles (90°, 120°, 150°) was simulated by the DEFORM-3D software with different extrusion speeds and initial billet temperatures. The simulated results show that the peak load of the extrusion process with big mandrel angle is obviously higher than that of the small angle and the inhomogeneity of billet velocity field is intensified with the increase of the mandrel angle.

Effects of Process Parameters on Hot Extrusion of Hollow Tube

The control of hot extrusion process is a highly complicated task due to high deformation and high billet temperature during the process. A high-quality product can be produced by controlling the process temperature. In this present study, hot extrusion process of hollow tube is modeled by finite element method. Effects of process parameters, initial billet temperature, ram displacements, reduction of area, semi-die angle, and friction coefficients are studied. Finite element results are compared with the experimental results from previous studies. The results reveal that there is a good agreement between simulations and experiments. It is determined that reduction of area and friction coefficient have strong effects on surface temperature and extrusion force. The surface temperature is increased with increasing ram displacement and decreased gradually at the exit of the die due to heat transfer with the environment. Extrusion forces are increased up to friction coefficient of 0.35 for 13 and 25% reduction of areas. However, extrusion forces are not changed significantly after 0.2 coefficient of friction for 37 and 48% reduction of areas.

Identification of processing window for extrusion of large thick-walled Inconel 625 alloy pipes using response surface methodology

Identifying suitable processing window is necessary but difficult for achieving favorable microstructure and performance in extrusion of large thick-walled pipe with difficult-to-deform Inconel 625 alloy. In this work, a method was established for identifying the extrusion process window considering temperature control using response surface methodology. Firstly, the response surface models, which correlate temperature rise and peak temperature to key extrusion parameters, have been developed by orthogonal regression based on finite element calculated data. Secondly, the coupled effects of the key extrusion parameters on the temperature rise and peak temperature have been disclosed based on the regression models. Lastly, suitable extrusion processing windows, which are described by contour map of peak temperature in the space of extrusion speed and initial billet temperature, have been established for different extrusion ratios. Using the identified process window, a suitable combination of the key extrusion parameters can be determined conveniently and quickly.

Investigation of a moveable flash gap in hot forging

The most common method of bulk forming processes is closed die forging with flash. In these processes a surplus of material is used to ensure a complete filling of the cavity of the forging die. The surplus material is driven out of the die through the flash land, thus the design of the flash land has a major influence on the filling of the die. All dimensions of the flash land are typically fixed during the manufacturing process of the die and can not be changed within the forging process. By use of a moveable flash gap that can be actively changed during the forging process the material flow can be altered. This permits to improve the filling of the cavity. In this paper a moveable flash gap for a hot forging process is described and the influence of such a system on the filling of the die cavity is determined. This is done by a comparison to a conventional forging process with a fixed flash land. Furthermore, the results of experimental trials are compared to results of corresponding FEA simulations. Additionally, the influence of the initial billet temperature is investigated. Experimental trials showed that the moveable flash gap has a distinct influence on the material flow. The higher the flash ratio, the bigger is the influence of the moveable flash gap. The moveable flash gap is designed as a flash brake of a height of 2mm. Its usage lead to differences in height of the parts up to 4.5mm, which correspond to 16.6% of the parts volume, compared to parts forged with a fixed flash land. If the forging temperature is decreased from 1200°C to 1000°C, the influence of the moveable flash gap is reduced. The average differences in height are about 0.5mm (about 3%).

Dependence of Microstructure, Texture and Tensile Properties on Working Conditions in Indirect-Extruded Mg-6Sn Alloys

Abstract Dependence of microstructure, texture and tensile properties on working conditions (ram speed and initial billet temperature) in indirect extruded Mg-6wt%Sn alloys were investigated by optical microscope (OM), scanning electronic microscope (SEM), X-ray diffraction (XRD) and a standard universal testing machine. Results show that the grain size, the recrystallization fraction and the dynamic precipitate fraction of the alloys are greatly affected by the working conditions. Their texture intensities weaken as the ram speed and the initial billet temperature increase. Tested in the different working conditions, the ultimate tensile strengths of the Mg-6Sn alloys extruded at high working temperature (controlled by initial billet temperature and ram speed) are remarkably better than those at the medium and low temperatures. The tensile properties of the alloys extruded at the high working temperature are similar to those of a commercial AZ31 alloy extruded at the low temperature, showing the possibility of the development of high speed extruded Mg alloys based on Mg-6Sn alloy.

DRX rules during extrusion process of large-scale thick-walled Inconel 625 pipe by FE method

A thermal-mechanical and micro-macro coupled finite element (FE) model for the hot extrusion process of large-scale thick-walled Inconel 625 pipe was developed based on the DEFORM-2D platform. Then, the influence rules of the key extrusion parameters on the average grain size and grain uniformity of the extruded pipe were revealed. The results show that with the increase of initial billet temperature, extrusion speed and friction coefficient, the grain uniformity is firstly improved and then deteriorated. Larger extrusion ratio leads to more uniform grain distribution. With the increase of initial billet temperature, the average grain size of the pipe first decreases and then increases. Additionally, larger extrusion ratio can bring smaller average grain size. The extrusion speed and friction coefficient have slight effects on the average grain size of the extruded pipe.

Microstructural modeling and numerical simulation of multi-physical fields for martensitic stainless steel during hot forging process of turbine blade

The mechanical properties of forgings mainly depend on the microstructure evolution during closed-die forging process, during which the microstructure mainly undergoes dynamic recovery, dynamic recrystallization, static recovery, static recrystallization, and metadynamic recrystallization. The macroscopic factors such as deformation temperature, strain rate, and strain play a key role in the microstructure evolution when the material composition is given. This paper presents the mathematical models for the prediction of microstructure evolution for martensitic stainless steel based on the hot compression test. A coupled analysis system of flow stress field, temperature field, and microstructure evolution for hot forging was developed based on the commercial software. The forging process of martensitic stainless steel turbine blade was simulated by the developed system. The influence of initial temperature of billet and deformation velocity on the load and finial temperature of forging part was analyzed. The variation of strain, temperature, and recrystallization volume fraction and grain size has been analyzed through simulation of the forging process. Based on the simulation results, the optimum hot forging process for complex forging parts was obtained.

Porthole extrusion process design for magnesium alloy bumper back beam

Porthole extrusion is a useful process for manufacturing lightweight materials with complex cross-sectional shape. In porthole extrusion, the material flow is complex due to the complex structure of the die. Therefore, it is not easy to design an appropriate extrusion process. Magnesium alloy exhibits low deformability at temperatures below 200°C because of its hexagonal close-packed crystal structure. It also suffers from the problem of surface oxidation at temperatures above 400°C. Therefore, it is important to set the appropriate extrusion conditions. In this study, the porthole extrusion process for manufacturing automobile bumper back beams is designed. The influence of initial billet temperature, ram velocity, and nitrogen cooling system on the surface temperature of extruded magnesium alloy is investigated using FE analysis. First, the initiation temperature of surface oxidation is evaluated through extrusion test. Then, based on the FE analysis, the extrusion limit diagram is obtained considering the surface oxidation temperature and the extruder capacity. The effect of nitrogen cooling on surface temperature is investigated through coupled CFD and FE analysis. From the analyzed results and extrusion limit diagram, the initial billet temperature and ram velocity are determined. Finally, the effectiveness of the designed extrusion process is verified through an experiment.

Simulation and optimization of hot extrusion process to produce rectangular waveguides

In this study, the Taguchi method and genetic algorithm are employed to optimize the die geometry in order to obtain the minimum magnitude of extrusion force to produce the rectangular waveguides. Waveguides are hollow metal tubes for transporting electromagnetic energy from one region to another. A combination of process parameters was selected using orthogonal array Taguchi method. The results were then simulated by finite element method (FEM). By using the analysis of variance (ANOVA) method, the effective parameters and their interactions were determined. By using the FEM results, an artificial neural network (ANN) model was trained, and the effects of die factors on the extrusion force were studied for constant thermal and frictional conditions. Moreover, the optimum conditions were predicted by means of genetic algorithm (GA) method which was verified by experimental procedure. The optimum die length and billet hole diameter were obtained at L = 20 and D = 3 cm, respectively, for the initial billet temperature of 450 °C and friction coefficient of 0.1.

Initial billet temperature influence and location investigation on tool wear in cross wedge rolling

A 3D thermal–mechanical elastic–plastic FE wear model for investigating tool wear in cross wedge rolling (CWR) process was developed and validated in this paper, especially considering the influence of temperature on tool parameters under the circumstance of laboratory. Tool wear, contact stress, and contact temperature along tool wedge ridge path under different initial billet temperatures were investigated. To study the influence of initial billet temperature, the tool wear is considered as the combined effects of tool thermal softening behavior and resistance to workpiece plastic deformation. Unit wear is firstly introduced to describe the effect of the material thermal softening behaviors on tool wear. Results show that tool wear occurs severely along the wedge ridge and reaches its maximum as the workpiece is rolled at a half round. The minimum tool wear can be achieved using appropriate initial billet temperature. The proposed methodology may help CWR manufacturers to design and produce tools that exhibit less wear.