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Microstructure evolution during metal forming processes
Abstract
Recrystallization and grain growth evolutions during metal forming processes are considered. Coupling between the thermo-mechanical and microstructure processes is realized. Die forging of a rear-axle flange is simulated numerically on the base of the finite element method. Material parameters of the models are obtained experimentally. The influence of interpass and holding times on grain size distributions in the end product is shown.
... However, in the case of ingots with larger diameter and thickness exceeding 800 mm, it is common to encounter inhomogeneity in grain size distribution. These variations frequently give rise to irregularities in mechanical properties, which may lead to rejection of parts [15]. ...
... It takes into account both material strengthening and softening phenomena that occur during the hot deformation process [42]. Equation (15) provides the mathematical expression for the Hansel-Spittel model, which highlights the relation between flow stress and the inherent material parameters. Fig. 6 Flow stress curves measured (dashed) and corrected (solid) for both adiabatic heating and friction Here, = stress (MPa), ̇= strain rate (s −1 ), = strain, T = hot deformation temperature (°C), and A, m 1 to m 8 are the material parameters. ...
... Hence, considering the AARE and R 2 values, the predictions of the Arrhenius model demonstrated a higher level (15) = A o e m 1 T m 2̇m3 e m 4 (1 + ) m 5 T e m 6̇m7 T m 8 ...
The inhomogeneity present in the deformation and microstructure during the open die forging of large size ingot significantly influences the mechanical properties of the final part. This study aims to develop a microstructure-based finite element (FE) model and investigate the influence of deformation path on microstructure evolution during the upsetting process of large size ingot of a high strength steel. The difference in deformation path is achieved by modification in anvil shape such as flat, v shape, convex, and concave die. To achieve this goal, hot compression tests were carried out using the Gleeble 3800 thermomechanical simulator. Utilizing the acquired and corrected flow stress data, a material model and a microstructure model were established, and both formulated models were then integrated into the Forge NxT 3.2 finite element simulation software through the inclusion of a dedicated user subroutine. The predictions from the FE analysis were validated with experimental results on standard size hot compression specimens, which allowed for the accurate prediction of the dynamic recrystallized average grain size at the end of hot deformation. Afterwards, the validated FE model was scaled up to simulate the industrial upsetting process, making it possible to investigate the effect of deformation path on inhomogeneity of strain and microstructure evolution at the end of upsetting process for large sized forged ingots. An evaluative analysis of four die geometries, aimed at identifying the optimal die shape for minimizing inhomogeneity in strain and grain size across a large size forged ingot, was conducted. It was found that the convex die provokes the lowest deformation, while the concave die induces the highest deformation values at the center of the ingot. Utilizing the coefficient of variation as an indicator of heterogeneity, it was determined that the v-die and concave die resulted in a more consistent grain size distribution compared to the flat and convex dies.
... Therefore, to obtain the desired properties, it is necessary to carefully design the process to yield the required microstructure distribution in the final product. Traditionally, process design in the context of hot forging has majorly been limited to address issues such as die designing [1,2], reducing underfill [3], avoiding possible defects [4][5][6], flash design [7][8][9], forging load [10][11][12] and more recently microstructure evolution [13][14][15][16][17]. Often, these approaches focus primarily on the deformation sub-step design without paying much attention on the role of the process in the larger product development workflow which includes material selection, other upstream and downstream processes and final property requirement. ...
... A volume average of the size of dynamically recrystallized grains as well as un-recrystallized pancaked grains is used to predict the final average grain size ( D f ). Equation (15) shows the expression used for calculation of D f , where D RX ,i denotes the value of D RX for the ith simulation increment with corresponding recrystallization fraction increment ΔX i , and X denotes the total DRX fraction. ...
One of the key aspects of integrated computational materials engineering approach is the integrated modelling of process chains that capture the essential microstructure physics and predict the final properties. In the current work, such an integrated modelling approach is attempted for analyzing the hot forging process for low-alloyed steels. Traditionally, hot forging process is designed with primary focus on the deformation step, with less attention paid to the incorporation of microstructure information flow between its sub-steps of heating, deformation and cooling. Such a siloed approach restricts its integration with other manufacturing processes, and also with design and material selection stages. To address the issue, in this work, a FEM based thermo-mechanical modelling framework, integrating composition dependent microstructure evolution models for heating, deformation and cooling sub-steps, is implemented for hot forging of low-alloyed steels. The evolution of key microstructural features at each sub-step is tracked and fed to the following step. The integrated modelling framework is then used to study the effect of process parameters and macrosegregation in the billet on the distribution of final microstructure and properties obtained for a sample steel upsetting process. Key observations made in the studies are discussed. Ways of representation of the distribution of microstructure and properties across the forged part, that can enable better decision making in the larger perspective of downstream processing and final use, are highlighted. Consequently, the utility of the integrated modelling approach to aid the development of improved process and product design capabilities for hot forged products is established.
... Besides the dimensional accuracy, another purpose of hot forging is to improve the microstructure and mechanical properties of the components [15]. During hot forming process, the work hardening caused by material deformation can be eliminated by the occurrence of dynamic recovery (DRV) and dynamic recrystallization (DRX) [16][17][18]. ...
... Meanwhile, the highest strain appears at the inner cavity of the cupulate part. It has been reported that the DRX behavior during forging was strongly affected by the accumulated strain energy [15]. The non-uniform strain might lead to the inhomogeneous grain size of the forging. ...
Precision forging process of a half axle flange was studied based on numerical simulation and experiment. The preform shape was optimized to avoid the forging defects, and the microstructure of initial billet and obtained forging was also examined. The results showed that the unreasonable material flow behavior can cause the defects of laps and under-filling during final forging process. Through increasing the load surface and adding transition chamfer in the joint having dramatic variation of cross section, the preform shape was optimized and the forging defects were avoided. Moreover, the forging load was reduced to one third of the initial process after optimization. Both the grain growth and the recrystallization were observed during hot forging. However, due to the non-uniform distribution of strain, stress, and flowing velocity, the grain size and precipitation of cementite varied significantly in different positions of the obtained forging part.
... The development of finite element methods together with the availability of high speed computers make the analysis of metal flow behaviour easier and more reliable for complex metal working processes such as hot forging, extrusion and rolling etc. [61,62]. This approach is usually coupled with geometric modelling, and pre and post processor tools are required to solve the most complex problems during metal working [63]. ...
... The hot deformation process has been successfully simulated using the numerical methods such as finite element (FE) [61,62], to understand the behaviour. ...
The need for improved mechanical properties and reduced trials during bulk metallic forging of Ti6Al4V alloy led to this advanced research. The experimental outcomes and the developed FEM based model was considered as most powerful for the industrial applications during hot working of Ti6Al4V alloy.
... The model for phase transformation, based on the equations given in [2] is used. The relations concerning grain size evolution and phase transformation are involved into the FEM code MSC MARC [3]. This enables evolution of grain size distribution and phase transformation in the entire deformed body to be obtained. ...
... Closed die forging under high temperature is considered [3,4,5]. The process consists of two passes ( Fig.1) with interpass and holding times. ...
Grain size evolution and phase transformation during metal forming processes is investigated numerically by means of the Finite element method. Appropriate microstructure models are involved into the FEM code MSC.MARC. Material characteristics obtained by means of own experiments are used. Hot closed die forging and rod rolling are considered. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
... In this context, the selection of the open die forging parameters, namely, strain, strain rate, and temperature, is of paramount importance [3,4]. Indeed, while it is possible to obtain a uniform grain size distribution in small to medium size bars, when it comes to larger diameters measuring more than 50 cm, [5], a non-uniform grain size distribution is commonplace. Such variations often result in non-conformities, and even part rejection. ...
The microstructure evolution, plastic deformation, and damage severity during the open die hot forging of a martensitic stainless steel were investigated using finite element (FE) simulation. A microstructure evolution model was developed and combined with a visco-elastoplastic model to predict the strain, the strain rate, and the temperature distribution, as well as the volume fraction and the size of dynamically recrystallized grains over the entire volume of an industrial size forging. The propensity to damage during hot forging was also evaluated using the Cockcroft & Latham model. The three models were implemented in the FE code and the results analyzed in terms of microstructure inhomogeneity and stress levels in different regions of the forging. A good agreement was obtained between the predicted and the experimental results, demonstrating that the simulation provided a realistic representation of the forging process at the industrial scale.
... In order to be able to handle a forming process of a particular material, it is necessary to have a certain comprehension of microstructural changes. In general, extensive material parameter studies are indispensable for predicting the final microstructure resulting from the forming process, such as anisotropy and the resulting grain size or grain size distributions, as well as possible material damage influencing variables [69]. ...
Smart factories are an integral element of the manufacturing infrastructure in the context of the fourth industrial revolution. Nevertheless, there is frequently a deficiency of adequate training facilities for future engineering experts in the academic environment. For this reason, this paper describes the development and implementation of two different layer architectures for the metal processing environment. The first architecture is based on low-cost but resilient devices, allowing interested parties to work with mostly open-source interfaces and standard back-end programming environments. Additionally, one proprietary and two open-source graphical user interfaces (GUIs) were developed. Those interfaces can be adapted front-end as well as back-end, ensuring a holistic comprehension of their capabilities and limits. As a result, a six-layer architecture, from digitization to an interactive project management tool, was designed and implemented in the practical workflow at the academic institution. To take the complexity of thermo-mechanical processing in the metal processing field into account, an alternative layer, connected with the thermo-mechanical treatment simulator Gleeble 3800, was designed. This framework is capable of transferring sensor data with high frequency, enabling data collection for the numerical simulation of complex material behavior under high temperature processing. Finally, the possibility of connecting both systems by using open-source software packages is demonstrated.
... При этом новые подходы в совершенствовании технологических процессов деформирования основываются, как правило, на изменении напряженного состояния заготовки с целью более полного использования пластических свойств металла. Управление напряженным состоянием при этом достигается как за счет существенного изменения граничных и контактных условий, так и в результате дополнительного силового воздействия на заготовку или часть ее, что приводит к изменению напряженно-деформированного состояния в очаге деформации [8][9][10][11][12][13][14]. ...
The paper provides the results of simulating the hot die forging of porous powder preforms with active friction forces applied along the lateral surface of the deformable blank by means of internal cohesion in the die-material system. The study covers the evolution of relative density distribution over the blank cross section at different stages of deformation, stress-strain state and total strain force while varying the loading boundary conditions by changing the initial compression force applied to elastic elements that prevent the die from displacement. It is shown that active friction forces acting on the periphery of the forging adjacent to the die inner side result in areas with a significantly higher deformation intensity compared to deformations in the center of the blank volume. At the same time, the volume of the high deformation intensity area and maximum values of deformation increase with a decrease in the spring initial compression force and, accordingly, with an increase in the die displacement value during deformation. Automatic die displacement due to internal cohesion in the die-deformable material system leads to a decrease in the total deformation force, and with a decrease in the die displacement value during deformation, the deformation force increases.
... When the temperature grows, the mobility of grain boundaries increases with the rise of forging temperature. Thus, the small dynamic recrystallization grain can grow rapidly and replace previous large grains [25][26][27][28]. However, with the further increase in temperature, the grains grow larger and larger, leading to larger average grain size. ...
In this study, we proposed a screening strategy of processing conditions for hot forging based on high-throughput experiment equipment, numerical simulation, and machine learning to obtain the optimal conditions for the forging process. Nikle based superalloy IN718 was selected as an application case. We designed high-throughput experiment equipment for hot forging. Numerical simulation of the forging process on the equipment was studied, and a database of 625 examples was obtained. Two BP NN models for average grain size and maximum principal stress predictions, respectively, were trained. These two BP NN models were used to search different processing conditions in searching space consisting of 1 206 000 processing conditions, and an algorithm was designed to screen the processing conditions comprehensively considering the average grain size and the maximum principal stress in the bulge zone. The optimal conditions for different forging displacements were obtained. Compared with the traditional high-cost and time-consuming trial-and-error methods, the method proposed in this paper to optimize the processing technology has significant advantages. This method can be applied to pre-screening for material design and process optimization.
... 42CrMo is selected as the materials of the simulation model [22][23][24][25]. At 0.01 s −1 strain rate, the true stress-strain curves of 42CrMo at different temperatures are shown in Figure 4, and the curve is subjected to multivariate nonlinear fitting. ...
Due to the instable conditions caused by the wear of rollers, macro voids inevitably occur in skew rolling steel balls. Macro voids in rolled balls greatly weakens the mechanical properties, resulting in the scrapping of about 23% of all skew rolling balls. This paper adopts the floating-pressure method (FPM) to eliminate macro voids in rolled steel balls, and mainly focuses on the investigation of the influencing factor void closure in skew-rolled balls. The research contents are listed as follows: Firstly, the mechanical model of FPM eliminating void in rolled steel balls is established, and the theoretical relationship between influencing factors of void closure is obtained. Then, the metal flow behaviors, the stress distribution and the effect of process parameters on void closure are revealed by numerical analysis. Subsequently, based on the uniform design method, the prediction equation of the required temperature and air pressure for compacting various inferior rolled balls with different diameter by FPM is deduced. Finally, the FPM experiment is carried out to verify the results of numerical analysis. The research results provide theoretical guidance for eliminating macro voids in skew-rolled steel balls.
... The predictability of the FE models is primarily depending on the accuracy of the constitutive models used. Bontcheva and Petzov, [1], used the experimentally obtained material parameters in FE method to simulate the die forging of the rear axle flange. Grass et al. [2] simulated the hot forming and microstructure evolution using FE method. ...
As one of the most mature titanium alloys, Ti6Al4V is widely used in many critical aerospace applications. However, the flow behavior of this alloy cannot be easily predicted using general computational models, mainly due to the existence of various microstructural morphology in titanium alloys and relatively complex deformation
mechanisms during hot deformation. Principally, the variation in initial grain morphology and grain size/plate thickness significantly influences microstructural evolution during hot working, thus leading to dissimilar work hardening and related softening behaviors. In the current study, a microstructural based Estrin Mecking (EM)+Avrami model was developed and used to model the deformation behavior of Ti6Al4V alloy with different initial grain morphologies (i.e. equiaxed vs martensitic) during simulative hot compression testing in the α+β phase region. Herein, the effect of initial grain size was considered as a function of Hall-Petch strengthening, where experimental validation revealed very good accuracy on predicting the work hardening behavior, peak stress, peak strain and flow softening with varying grain morphologies. In addition, the current model was extended to predict the material flow behavior of Ti6Al4V alloy during bulk metallic deformation (i.e. forging) in 3D as an FEM based simulation tool.
... This model is also referred to as friction factor model or Siebel friction law[92,[94][95][96][97][98][99]. However, this model was not found by the author in Siebel's article[100].2 ...
Aluminium forged parts play a significant role as components of light weight constructions
in the automotive and aerospace industry. The fundamental knowledge of the friction be-
haviour at the tool-workpiece interface is necessary due to the fact, that it influences
material flow, die filling, wear and workpiece quality.
In order to understand the tribological processes and interactions in the tool-workpiece
interface systematically, basic experiments that allow an independent variation of influ-
encing parameters are necessary. This thesis presents an investigation of friction in hot
forging of aluminium by employing a modified ring-on-disc test. The experiments were
performed with commercial graphite-based lubricants and at various loads, sliding veloc-
ities and specimen surface conditions. In addition, some tests were performed without
lubrication. It was found, that dry sliding conditions result in sticking and – at low
normal loads – in galling at the die-workpiece interface. Micrographs confirmed that at
dry friction (most of) the relative motion was done by shearing in subsurface layers of
the workpiece. When employing lubricants, the shearing was restricted to the graphite
layer. In dependence on the used product and the normal load, the friction coefficients
varied within narrow limits from 0.01 to 0.11. Generally, the friction coefficient decreased
with increasing normal pressure at all investigated lubricants. In the observed range, the
sliding velocity had no significant influence on the tests. However, the scatter of the fric-
tion coefficients at various velocities got smaller with increasing normal pressures. The
results were compared to the results of a study employing a pin-on-disc test for lubricant
evaluation, and good qualitative agreement was found in terms of friction coefficient and
friction evolution during the tests.
In accurate finite element analysis, friction has to be faced by numerical models that
consider the real conditions at the die-workpiece interface. In this context, physical ap-
proaches based on a contact model (for the determination of the real contact area) and a
local friction law (applied to the real contact spots) allow the formulation of friction mod-
els that take the complexity of the tribosystem into consideration. This thesis presents
a new contact model that takes the material properties and real asperity shapes into
consideration, and simplification is achieved by making use of the statistical character of
real surfaces. The main idea of the new concept was to obtain the real contact area-load
relation by combining the bearing area curve and a model asperity with correct repre-
sentation of the mean asperity slope. Experiments with aluminium specimens showed
excellent correspondence with the numerical results.
... Manufacturing of high-performance and defect-free parts by the use of hot deformation processes such as hot forging and rolling depends significantly on the applied thermomechanical parameters during the production process. Deformation with high-temperature metal forming techniques not only changes the shape of the part to a desirable form, but also alters the microstructure of material and therefore leads to the substantial change in the flow stress during deformation [1]. So, in order to produce defect-free parts with the proper microstructure, deformation temperature and strain rate must be selected with care [2]. ...
In the present study, the variation of the critical ductile damage during hot deformation was investigated using hot compression testing and finite element simulation. Based on the obtained results, the critical ductile damage diagram was developed for AISI321 austenitic stainless steel. Results showed that the value of critical damage is not constant during deformation in the temperature range of 800-1200˚C. It is also concluded that the critical ductile damage value is varied between 0.24 and 0.41 depending on hot deformation conditions. This means that, the critical ductile damage value is increased with increasing deformation temperature and decreased by increasing strain rate.
... Most likely, intensive plastic deformation also causes a significant change in microstructure of material in a narrow layer near frictional and bi-material interfaces in metal-forming processes [18][19][20][21][22][23][24]. The equivalent strain rate is usually involved in evolution equations for parameters characterizing the microstructure of material in such a manner that high gradients of the equivalent strain rate predict high gradients of material properties (see, for example [25][26][27][28]). Since (1) predicts intensive plastic deformation in a narrow layer near frictional interfaces, this theoretical result is in qualitative agreement with the experimental results reported in [18][19][20][21][22][23][24]. ...
This chapter is concerned with a numerical method for calculating the strain rate intensity factor in plane strain deformation of rigid perfectly plastic material.
... The visual inspection, which is more utilized in the industry, presents a high subjectivity degree, as it depends on the operator experience, and also is very slow and exhaustive [3][4] [5]. Otherwise, the image analysis inspection, which is becoming more and more used, has greater operator independence, usually greater accuracy and high productivity time analysis [6]. ...
The properties of materials are identified as the results of its microstructures characteristics. Consequently the task of analysis of microstructure is very important in engineering. There are several methods such as the visual inspection and the semi-automatic inspection by image analysis. Visual inspection by an operator is subject to human error and can take important time. The semiautomatic method using specific algorithm and technique improves performance of the work, however still needs specific knowledge concerning image filters and image analysis technique. This research’s objectives are to present automatic image analysis algorithm to measure grains in microstructure images.
... Weronski [7] used the finite element method to analyze structural changes after forging an aluminum alloy. Bontcheva and Petzov [8] presented an approach for numerical simulation of die forging on the basis of the FEM. Hartley and Pillinger [9] provided a short overview of recent research in the numerical simulation of forging, including Process Modelling, Tool and Die Design, Interface Phenomena, Material Phenomena and Computational Aspects. ...
Forging is simple and inexpensive in mass production. Metallic materials are processed through plastic deformation. This not only changes the appearance but also changes the internal organization of materials that improve mechanical properties. However, regarding manufacturing of plastic products, many processing factors must be controlled to obtain the required plastic strain and desired tolerance values. In this paper, we employed rigid-plastic finite element (FE) DEFORMTM software to investigate the plastic deformation behavior of an aluminum alloy (A7075) workpiece as it used to forge bicycle pedals. First we use Solid works 2010 3D graphics software to design the bicycle pedal of the mold and appearance, moreover import finite element (FE) DEFORMTM 3D software for analysis. The paper used rigid-plastic model analytical methods, and assuming mode to be rigid body. A series of simulation analyses in which the variables depend on different temperatures of the forging billet, round radius size of ram, punch speed, and mold temperature were revealed to confirm the predicted aluminum grain structure, effective stress, effective strain, and die radial load distribution for forging a bicycle pedal. The analysis results can provide references for forming bicycle pedal molds. Finally, this study identified the finite element results for high-strength design suitability of a 7075 aluminum alloy bicycle pedal.
... Most likely, intensive plastic deformation also causes a significant change in microstructure of material in a narrow layer near frictional and bi-material interfaces in metal-forming processes [18][19][20][21][22][23][24]. The equivalent strain rate is usually involved in evolution equations for parameters characterizing the microstructure of material in such a manner that high gradients of the equivalent strain rate predict high gradients of material properties (see, for example [25][26][27][28]). Since (1) predicts intensive plastic deformation in a narrow layer near frictional interfaces, this theoretical result is in qualitative agreement with the experimental results reported in [18][19][20][21][22][23][24]. ...
Using the classical model of rigid perfectly plastic solids, the strain rate intensity factor has been previously introduced as the coefficient of the leading singular term in a series expansion of the equivalent strain rate in the vicinity of maximum friction surfaces. Since then, many strain rate intensity factors have been determined by means of analytical and semi-analytical solutions. However, no attempt has been made to develop a numerical method for calculating the strain rate intensity factor. This paper presents such a method for planar flow. The method is based on the theory of characteristics. First, the strain rate intensity factor is derived in characteristic coordinates. Then, a standard numerical slip-line technique is supplemented with a procedure to calculate the strain rate intensity factor. The distribution of the strain rate intensity factor along the friction surface in compression of a layer between two parallel plates is determined. A high accuracy of this numerical solution for the strain rate intensity factor is confirmed by comparison with an analytic solution. It is shown that the distribution of the strain rate intensity factor is in general discontinuous.
... References [3,4] analyzed the interaction between inside and the outside wedge of multi-wedge rolling on the influence of the microstructure. N. Bontcheva and G. Petzov [5] combined the recrystallization with grain growth in the process of metal forming, and took a numerical simulation of the flange shaft by using the finite element method. In addition to the date of austenitic grain growth process which was good in optimization of process parameters, they achieved the deformation and recrystallization kinetics model for metal in the rolling process, providing the theoretical foundation for predicting the microstructure and mechanical properties of the formed parts. ...
To investigate the distribution law of microstructure during stretching stage for cross wedge rolling of asymmetric shaft parts, so as to achieve a coordinated forming control of shape and quality in cross wedge rolling of asymmetric shaft parts, we employed the finite element method in this paper to simulate the process of cross wedge rolling of asymmetric shaft parts. By studying the dynamic recrystallization volume fraction and the average grain size distribution in stretching stage as well as comparing the average grain size of asymmetric rolling and symmetric rolling, we achieved the high temperature austenitic grain size distribution during stretching stage for cross wedge rolling of asymmetric shaft parts, then conducted the corresponding experimental verification. The study results have important scientific significance and engineering application value for the rolling technology innovation of cross wedge rolling shaft parts by enriching and improving the theory of cross wedge rolling of asymmetric shaft parts, reducing the production cost and improving the quality of rolled products.
... The traditional production of rings was alloy smelting, steel ingot casting, steel ingot cogging and forging, initial forging, punching, cutting, hot rolling forming, heat treatment process was generally taken to improve the material mechanical properties. Then, machining made the ring size meet the requirements of the manufacturer [1]. The production process was lengthy, combined with repeated heating in this process, it cause the wasting of material and energy, oxide coating was taken in this process simultaneously that would reduce the quality of the rings [2,3]. ...
The traditional production process of large seamless rings brought the serious waste of material and energy. 42 CrMo alloy steel was taken as material of the rings. The research of Casting-Rolling Continuously Forming process was Smelting Casting→ Ring blank→ Concurrent heating and heat holding →Hot rolling forming. The work reported here concentrates on resolving the energy consumption, consumables, low production efficiency of ring production, provided some reference for the rings production.
... Over the decades, Finite Element Method (FEM) has been successfully used to simulate and optimize the thermo-mechanical processes [14][15][16] like rolling, forging and extrusion. FEM can be used to study effect of different process parameters like friction, temperature, and speed on the product quality and to predict and prevent occurrence of defects without carrying out actual trials that saves lot of time and money. ...
Stainless steels of different types and grades are being developed world over to meet ever increasing demand for enhanced materials performance. Advanced stainless steel products have applications in a variety of industries including nuclear, defence, space, chemical, oil and gas, medical and appliance. It is understood that the properties of the alloys strongly depend not only on the chemical composition but also on their microstructure, which in turn depends on parameters in the manufacturing process. Therefore, the challenge to the manufacturing industry is not only selection of optimum composition but also relevant manufacturing processes to meet the requirements. Designing a manufacturing process and optimum process schedules using experimental trials is both time consuming and expensive. Modeling and simulation play an important role to reduce these times effectively. This paper presents important points to be considered to produce clean steels and highlights the applicability of modeling techniques that can be effectively applied in a manufacturing industry. Some of the case studies that are included in the paper are Computational Fluid Dynamics model to understand gas atomisation Finite element modeling of compound tube extrusion In conclusion, the power of modeling and simulation to understand manufacturing processes is highlighted.
... Because in the deformation process,the outer surface contact the outside air, its temperature drops fairly rapidly, the incidence of recrystallization is lower. But the process of cooling in the center is relatively slow, the temperature is still high [8]. The recrystallization incidence is not the same in different extrusion. ...
The subject of study is the vertical extrusion of P91 large diameter thick-walled seamless steel tube, simulate the variation of microstructure during the abbreviated ratio test. Compare the simulation results and the results of Steel pipe specimens metallographic which were in different extrusion ratio, research the influence of extrusion ratio on microstructure and properties from micro-organizational level, and verify the accuracy of the microstructure evolution of the mathematical model.
... Research on the high temperature flow stress of metals undergoing deformation is significant in the study of the hot working process and theories of plastic deformation [1] [2] [3]. Therefore, research test data is used to build constitutive equations of materials to predict high temperature flow stress [4] [5] [6] [7]. 20CrMo alloy steel is widely used in oil field equipment. ...
The experimental true strain–true stress data from isothermal hot compression tests on a Gleeble-1500D thermal simulation machine, across a wide range of temperatures (1173–1373 K) and strain rates (1.5 Â 10 À3 –1.5 Â 10 À2 s À1), were employed to study the deformation behavior and develop constitutive equations of 20CrMo alloy continuous casting billet steel. The objective was to obtain the relational expression for deformation activation energy and material constants as a function of true strain and the constitutive equation for high temperature deformation of 20CrMo based on the hyperbolic sine form model. A correlation coefficient of 0.988 and an average absolute relative error between the experimental and the calculated flow stress of 8.40% have been obtained. This indicates that the constitutive equations can be used to accurately predict the flow behavior of 20CrMo alloy steel continuous casting billet during high temperature deformation.
... Some researchers investigated grain growth during hot deformation [11][12][13][14][15][16] and a few models were also proposed to predict grain growth [14,15,[17][18][19]. These models have been numerously used in simulations of superplastic forming [20][21][22][23]. ...
Constitutive models for dominant mechanisms in hot forming are proposed. These models consider inter-granular deformation, grain boundary sliding, grain boundary diffusion and grain growth. New stress-strain rate relationships are proposed to predict deformation due to grain boundary sliding and grain boundary diffusion. Besides a Taylor type polycrystalline constitutive model, a visco-plastic relation in conjunction with two different yield functions is used to predict inter-granular deformation. Step strain rate tests and bulge forming test are simulated with the proposed models. Results are compared with experimental data to verify the constitutive models. It is concluded that the visco-plastic models can predict material behavior in hot deformations as accurately as the polycrystalline model but with much less computational costs. To examine the hardening effects, the model is calibrated with tensile test data of AA5083 at 550 °C, where hardening is remarkable. Then, as an example, it is used to simulate a tray forming experiment. Dome heights and tray thicknesses at various positions during forming process are very close to experimental observations.
... Pietrzyk (2002) describes a complex thermal-mechanical microstructural model, which simulates all aspects of interest arising from a hot metal bulk forming process. A similar approach is taken by Bontcheva and Petzov (2003). General reviews on simulation based prediction of the microstructure in metal forming are given by Yanagimoto (2002) or Bariani, Dal Negro and Bruschi (2004). ...
A simplified approach for the simulation based estimation of the phase distribution in a thermo-mechanically treated steel component is presented. A key aspect of the approach is the time-temperature relation for each volume element. Based on a forming simulation with a commercial tool the numerically calculated temperature evolution in the component is analyzed with an in-house code. The code allows estimating the local phase distribution after the forming process with the help of the continuous-cooling-diagram of the material used. A first validation fits well with the existing phase distribution in the component, even though the phase transition in the component is critical in terms of time, deformation and local chemical composition of the material used.
Im vorliegenden Artikel wird ein vereinfachter Ansatz zur simulationsbasierten Abschätzung der Phasenverteilung in einem thermo-mechanisch umgeformten Stahlbauteil vorgestellt. Grundlegende Idee des Ansatzes ist die Betrachtung der Zeit-Temperatur-Entwicklung jedes Volumenelementes im Bauteil über den Verlauf des Umformprozesses. Dazu wird die numerisch ermittelte Temperaturentwicklung im Bauteil, die mit einem kommerziellen Programm berechnet wird, in einem selbst entwickelten Postprozessor analysiert. Der Postprozessor ermöglicht die Abschätzung der sich nach dem Umformprozess im Bauteil einstellenden Phasenverteilung auf Basis des kontinuierlichen Zeit-Temperatur-Umwandlungs-Schaubildes des verwendeten Werkstoffes. Eine erste Validierung der Postprozessorergebnisse zeigt gute Übereinstimmungen mit der realen Phasenverteilung im Bauteil, obwohl das Phasenumwandlungsverhalten des Werkstoffes empfindlich auf überlagerte Dehnungen und die lokale chemische Zusammensetzung reagiert.
... Among these parameters, the constitutive relation is one of the most important parameters that affect the solution accuracy, and it is represented in a wide range of working conditions in mathematics for the relationship between the flow behavior of materials and the strain, strain rate and the deformation temperature. Meanwhile, numerical methods such as finite element (FE) simulation have recently been successfully applied for the analysis of various metal-forming processes (Ref [13][14][15]. A constitutive equation is used as the FE input code for simulating the response of materials in specified loading conditions ( Ref 16,17). ...
In this paper, the constitutive relationship of an aluminum alloy reinforced by silicon carbide particles is investigated using a new method of double multivariate nonlinear regression (DMNR) in which the strain, strain rate, deformation temperature, and the interaction effect among the strain, strain rate, and deformation temperature are considered. The experimental true stress-strain data were obtained by isothermal hot compression tests on a Gleeble-3500 thermo-mechanical simulator in the temperature range of 623-773 K and the strain rate range of 0.001-10 s−1. The experiments showed that the material-softening behavior changed with the strain rate, and it changed from dynamic recovery to dynamic recrystallization with an increase in the strain rate. A new constitutive equation has been established by the DMNR; the correlation coefficient (R) and average absolute relative error (AARE) of this model are 0.98 and 7.8%, respectively. To improve the accuracy of the model, separate constitutive relationships were obtained according to the softening behavior. At strain rates of 0.001, 0.01, 0.1, and 1 s−1, the R and AARE are 0.9865 and 6.0%, respectively; at strain rates of 5 and 10 s−1, the R and AARE are 0.9860 and 3.0%, respectively. The DMNR gives an accurate and precise evaluation of the flow stress for the aluminum alloy reinforced by silicon carbide particles.
... After this, the grain size of dynamic recrystallization did not change with strain and have no relationship with the initial grain size. The equation of the grain size of dynamic recrystallization to the Zener-Hollomon parameter were deduced [11][12]: ...
Single pass compression tests were conducted on Gleeble1500 thermal simulator. The effect of different deformation parameters on the grain size of dynamically recrystallized austenite was analyzed. A mathematical model of dynamic recrystallization and a material database of JB800 steel, whose tensile strength is above 800 MPa, were set up. A subprogram was compiled using Fortran language and called by Marc finite element software. A thermal coupled elastoplastic finite element model was established to simulate the compression process. The grain size of recrystallized austenite obtained by different recrystallization models was simulated. The results show that the optimized dynamic recrystallization model of JB800 bainitic steel has a higher precision and yields good agreement with metallographic observations.
... Modeling microstructure and its effects in hot rolling field were reported234 . Simulation of microstructures for hot forging processes was carried out by Bontcheva and Petzov [5] of forging, rolling or extrusion the strain rate varies during the deformation process and heat transfer leads to the development of temperature gradients and changes in the mean temperature of the workpiece. Constant and varying strain-rate deformation conditions have been applied to an Al–1% Mg alloy using plane strain compression (PSC) testing [7]. ...
The microstructure evolution during hot forming and sequential heat treatment was simulated to guide the process design by using the finite element method (FEM). The microstructure change under varying deformation conditions during hot forming was investigated. These formulations were implemented into a commercial finite element code to analyze microstructure evolution during hot forming and heat treatment. Static recrystallization, dynamic recrystallization and meta-dynamic recrystallization were taken into account. The FE module was applied to analyze the microstructure change of Al–1% Mg alloy. Al–1% Mg is very different to the steels since it does not appear to undergo dynamic (or, therefore, metadynamic) recrystallization because of the high rate of dynamic recovery. Static recrystallization was considered in the paper. The influence of transient strain rate deformation conditions on the deformed microstructure of Al–1% Mg was studied by using numerically analytical method and FEM. The simulated stress and microstructure change were compared with published experimental and analytical results. The evolution of grain structure for Al–1% Mg steering link forging (1999 German Forging Industry Association Benchmark) and sequential heat treatment was simulated using the 3D FE simulator combined with a microstructure module. The forging with finer grain structure is obtained by annealing for 2h at 400°C.
Based on the true stress–strain data obtained from dynamic compression experiments using split Hopkinson pressure bar, constitutive models including the Johnson–Cook model, modified Johnson–Cook model, Mechanical Threshold Stress model, and modified Arrhenius-type constitutive model are developed to describe the plastic flow behavior of GCr15 steel over a temperature range of 298 to 873 K and strain rates from 460 to 3940 s−1. The material parameters for the models are optimized using the Grey Wolf Optimizer, and the predictive performance is evaluated based on the correlation coefficient and average absolute relative error. Furthermore, the micromorphology of the specimen after impact is observed using a scanning electron microscope. The results indicate that all four constitutive models effectively reflect the plastic flow behavior of GCr15 steel. The modified Johnson–Cook model is more effective and accurate than the Johnson–Cook model, Mechanical Threshold Stress model, and modified Arrhenius-type constitutive model for predicting the dynamic compression behavior of GCr15 steel, with a correlation coefficient of 0.9711, an average absolute relative error of 2.6501% and a mean relative error of −0.2899%.
Taking the given S43CMnV non‐quenched and tempered steel multi‐cylinder (3‐cylinder and 4‐cylinder) crankshaft as the research object, the intrinsic relationship between the forging process, temperature controlled cooling process of 3‐cylinder crankshaft and the global‐local grain evolution process was analyzed by Deform‐3D software. Meanwhile, the influence relationship between average grain sizes and comprehensive mechanical properties of the 3‐cylinder and 4‐cylinder crankshaft was compared and analyzed in details. The results show that for the 3‐cylinder crankshaft, the larger cooling rates can achieve the smaller grain sizes. When the temperature controlled cooling rate is 60 °C/min, the average grain sizes of the crankshaft pin bearing, main bearing and flange end are 61.5 μm, 96.9 μm and 70.7 μm respectively, which meets the requirements of production process (approximately 127 μm). Wherein, the grain sizes and mechanical properties of the 4‐cylinder crankshaft are better than those of the 3‐cylinder crankshaft, and the after‐forging elongation of the 4‐cylinder crankshaft can reach at approximately 16.6 %. Furthermore, the grain sizes evolution of 3‐cylinder crankshaft obtained by numerical simulations are basically consistent with the experimental grain size results, and it is feasible to predict and control the grain sizes’ evolution and mechanical properties of the crankshaft hot forging by using Deform‐3D.
This paper presents the use of mathematical modeling for developing a multi-stage manufacturing process of producing a blank for a bellows unit reinforcement ring made of VT6 (Ti-6Al-4V) alloy. The paper studies the influence of the main process parameters on the formation and distribution of the proportion of globular microstructure over the blank cross-section. The change of form was determined using a finite element model of plastic deformation. The phase transformation kinetics was determined using the Johnson-Mehl-Avrami-Kolmogorov equation.
This paper developed high-temperature deformation constitutive models for a Ti6Al4V alloy using an empirical-based Arrhenius equation and an enhanced version of the authors’ physical-based EM + Avrami equations. The initial microstructure was a partially equiaxed α + β grain structure. A wide range of experimental data was obtained from hot compression of the Ti6Al4 V alloy at deformation temperatures ranging from 720 to 970 °C, and at strain rates varying from 0.01 to 10 s⁻¹. The friction- and adiabatic-corrected flow curves were used to identify the parameter values of the constitutive models. Both models provided good overall accuracy of the flow stress. The generalized modified Arrhenius model was better at predicting the flow stress at lower strain rates. However, the model was inaccurate in predicting the peak strain. In contrast, the enhanced physical-based EM + Avrami model revealed very good accuracy at intermediate and high strain rates, but it was also better at predicting the peak strain. Blind sample tests revealed that the EM + Avrami maintained good predictions on new (unseen) data. Thus, the enhanced EM + Avrami model may be preferred over the Arrhenius model to predict the flow behavior of Ti6Al4V alloy during industrial forgings, when the initial microstructure is partially equiaxed.
Microstructure determines the comprehensive mechanical properties and service life of ring parts. In this study, ring rolling process is considered as a multi-pass process which is parted into four phases, and the microstructure evolution model is then established based on the characteristics of this multi-pass process by combining with a 3D coupled thermo-mechanical FE model. By contrasting with experiment results, the microstructure evolution model is actually proven can be competently applied to predict the microstructure of the formed ring. Also through comprehensive analysis on distribution of recrystallization fractions based on the microstructure evolution model, conclusions can be summarized as following. (1) It is inaccurate to predict the microstructure by regarding the ring rolling as a single-pass deformation. The ring rolling process should be parted into different phases, and for each phase, the singlepass microstructure evolution model is adapted. (2) Different with single-pass deformation, due to the high temperature dwelling phase during ring rolling process, meta-dynamic recrystallization (MDR) is another important grain refinement mechanism besides dynamic recrystallization (DR). (3) MDR has different distribution trends with DR, which is benefit not only for grains refinement but also for microstructure uniformity. (4) Rolling penetration is obviously improved with feed rate increases, whereas, unduly high feed rate leads to recrystallization fraction decrease in outer layer area, which is adverse to microstructure uniformity.
This work investigates the effects of turning process parameters on recrystallization behavior in Al alloy 7075. To realize this purpose, samples were machined under different cutting speeds and material feed rates at two extreme levels. Microscopy imaging reveals that activation of dynamic recrystallization or grain growth depends on the combination of applied cutting parameters. Increasing the cutting speed intensifies recrystallization, while the feed rate governs the grain growth. Adjusting the cutting parameters enables one to obtain a desired average grain size below the machined surface, up to a ∼180μm depth. The average grain size of the initial material was 31.6μm. The imposed processing parameters successfully yielded average grain sizes in the range from 19 to 44 μm. Additionally, a computational framework work consisting of finite-element analysis (FEA) coupled with kinetic-based modeling of recrystallization was developed, which is capable of following the trend of change in the average grain size and acceptably predicts the evolved average grain size.
Integration of material composition, microstructure, and mechanical properties with geometry information enables many product development activities, including design, analysis, and manufacturing. In this paper, we investigate the application of image processing methods for constructing models of material microstructure. These microstructure models can be integrated into CAD models to enable the utilization of material process-structure-property relationships during CAD modeling. Engineering design is enabled by integration of computational materials design methods with these relationships. Using 2D images and 3D voxel datasets, the image processing methods can be used to find microstructure features, such as grain boundaries or particle or fiber reinforcements, by finding edges and extracting features from those edges. This paper will focus on three different image processing methods, which will be applied to microstructure images of materials fabricated by additive manufacturing.
The evolution of micro-texture below the machined surface is computationally modeled and experimentally verified. The orientation distribution functions of the grains below the surface were represented in spectral form. The microstructure descriptor coefficients were derived, and their change with respect to the change in the cutting feed rate was computationally calculated and monitored. Micro-texture experimental observations conducted by electron back-scatter diffraction technique verify the modeling outputs. Continuation of changing the process parameter was done by finite element method, and the evolution in texture was investigated by computational modeling. The process path function which correlates micro-texture evolution and cutting feed rate, was obtained by applying the principle of orientation conservation in the Euler space. As a result of the major finding of this work, i.e., derivation of process path functions, the evolution of texture as a function of the material feed rate is numerically determined without any need to texture modeling or finite element analyses.
The flow behavior of delta-processed Inconel 718 was studied in temperature range of 900-1060 °C and strain rate range of 0.0.01-0.5 s-1. The effects of friction and temperature on the compressive deformation behavior were investigated, and the flow stress-strain error caused by friction was revised. The results showed that the effect of the friction was obvious with increasing strain rate and decreasing deformation temperature. The revised flow stress is decreased by increasing temperature and decreasing strain rate and exhibits a typical dynamic recrystallization behavior. The constitutive model has been developed through a hyperbolic-sine Arrhenius type equation to relate the flow stress, strain rate and temperature. The influence of strain has also been incorporated by considering the variation of material constants as a function of strain. The prediction accuracy of developed constitutive model has been assessed using standard statistical formulae. According to the analysis results, the proposed deformation constitutive equation gives an accurate and precise estimate of flow stress of delta-processed Inconel 718 alloy.
The isothermal hot compression tests were carried out on Gleeble-3500 thermo mechanical simulator in the temperature range of 1323-1473 K and strain rates of 0.01 s(-1), 0.1 s(-1), 1 s(-1) and 10 s(-1). Based on the experimental results, a modified Johnson Cook model is proposed to describe the flow behavior of 124 steel. The modified model considers not only the yield and strain hardening portion of the original model but also the coupled effects of strain and temperature, and of strain rate and temperature on the flow behaviors. The high temperature deformation behavior of 124 steel was characterized based on the analysis of the stress-strain curves. The results showed that the flow stress predicted by the proposed model agrees well with the experimental stress, which validates the efficiency of the modified model in describing the deformation behavior of the steel. The true stress-true strain curves exhibit a peak stress at a very small strain, after which the flow stresses decrease until high strains, showing a typical dynamic recrystallization (DRX) behavior of the steel under the deformation conditions of lower strain rates.
Microstructural evolution, which is governed by temperature, strain and strain rate during hot forging, is a key factor influencing mechanical properties. Understanding the microstructural evolution of metals and alloys in hot forging has a great importance for the designers of metal forming processes. The principal objective of this paper is to provide an overview of the models for the prediction of microstructural evolution for metals and alloys during the hot forging process. In this review paper, the models are divided into four categories, including the phenomenological, physically-based, mesoscale and artificial-neural-network models, to introduce their developments, prediction capabilities and application scopes. Additionally, some limitations and objective suggestions for the further development of the modelling of microstructural evolution during hot forging are proposed.
Finite element method was used to analyze the effects of deformation temperatures on the strain/stress distribution and microstructure evolution of aluminium alloy during hot upsetting process. The results show that the deformation of the workpiece and dynamic recrystallization are
inhomogeneous. The deformation temperature has little influence on the value of average strain. The maximum volume fraction of dynamic recrystallization lies in the centre of the workpiece and at the edges of contact surfaces between the dies and the workpiece which is the same with strain
distribution. High temperature can decrease stress, die load and grain size, increase dynamic recrystallization volume fraction and the uniformity of strain and dynamic recrystallization. The desired deformation temperatures for aluminium alloy are from 400 to 450 °C. The internal structure
of alloy becomes fine with the increase of deformation temperature.
A set of mechanism-based constitutive equations was developed to model the effects of microstructure evolution on elastic–plastic flow of Q235 steel. This set of equations is implemented into the finite element (FE) solver ABAQUS for multi-pass shape rolling process simulation. The procedure for multi-pass rolling simulation was developed, a scheduled multi-pass rough rolling process of H-shape steel was carried out and the accuracy of the equations was validated by comparisons between the calculated mill load and measured ones. A numerical orthogonal experiment was designed to investigate the effects of rolling parameters on the microstructure evolution.
The true stress–strain data from isothermal hot compression tests on Gleeble-3500 thermo mechanical simulator, in a wide range of temperatures (1323–1473 K) and strain rates (0.01–10 s−1), were employed to establish the constitutive equations based on modified Zerilli–Armstrong and strain-compensated Arrhenius-type models respectively, and develop the artificial neural network model to predict the high-temperature flow stress of T24 steel. Furthermore, a comparative study has been made on the capability of the three models to represent the elevated temperature flow behavior of this steel. Suitability of the three models were evaluated by comparing the accuracy of prediction of deformation behavior, correlation coefficient and average absolute relative error of prediction, the number of material constants, and the time needed to evaluate these constants. The results showed that the predicted values by the modified Zerilli–Armstrong model could agree well with the experimental values except under the strain rate of 0.01 s−1. The predicted flow stress of the other two models shows good agreement with the experimental data. However, the artificial neural network model could track the deformation behavior more accurately throughout the entire temperature and strain rate range though it is strongly dependent on extensive high quality data and characteristic variables and offers no physical insight.
Manufacturing process modeling is gaining importance in view of stiff global competition to produce the goods of specified design in an optimal way. In particular, metal forming and machining (both traditional and non-traditional) have been extensively modeled using numerical techniques. Three basic steps of modeling of manufacturing processes are analytical representation of working principle of the process, modeling of material behavior and method of solution. In this paper, a comprehensive review of various approaches of material behavior modeling has been presented. The material behavior modeling has great influence on the design of process, tools and the final product. This aspect is highlighted in the present review. Metal forming processes, traditional machining processes and non-traditional machining processes are considered for the study. Different material models are compared with respect to their suitability for the design of process, tooling and product. Finally, the paper suggests the directions for further research in this area.
The deformation behavior of 1Cr12Ni3Mo2VNbN martensitic steel in the temperature range of 1253 and 1453K and the strain rate range of 0.01 and 10s−1 are investigated by isothermal compression tests on a Gleeble 1500 thermal–mechanics simulator. Most of the stress–strain curves exhibit a single peak stress, after which the stress gradually decreases until a steady state stress occurs, indicating a typical dynamic recrystallization (DRX) behavior of the steel under the deformation conditions. The experimental data are employed to develop constitutive equations on the basis of the Arrhenius-type equation. In the constitutive equations, the effect of the strain on the deformation behavior is incorporated and the effects of the deformation temperature and strain rate are represented by the Zener–Holloman parameter. The flow stress predicted by the constitutive equations shows good agreement with the experimental stress, which validates the efficiency of the constitutive equations in describing the deformation behavior of the material.
The true stress–strain data from isothermal hot compression tests, in a wide range of temperatures (1173–1473K) and strain rates (0.01–10s−1), were employed to study the deformation behavior and develop constitutive equation of V150 grade oil casing steel based on an Arrhenius-type equation. The flow stress increases with the decrease of deformation temperature and the increase of strain rate, which can be represented by Zener–Hollomon parameter in an exponential equation. The influence of strain was incorporated in the developed constitutive equation by considering the effect of strain on material constants. The flow stress predicted by the constitutive equation shows good agreement with the experimental value through the whole experimental temperature and strain rate range except a slight deviation for predicting the stress deformed at 1173K under 0.01s−1, and the average relative error is 4.21%.
In automotive industries, components have replaced steel with aluminum alloys since the automotive parts that used aluminum alloys have the ability to improve the environment by lower weights and recycling of waste materials. In this study, experiments were carried out to investigate the characteristics of the developed aluminum alloys according to the forming temperature and speed. The microstructure of forged product in hot forging process was also investigate. The results revealed that the grain size of aluminum alloys was grown according to the forming temperature and speed. Three-dimensional finite element analyses were also carried out to investigate the forming load, deformed shape, and the stress distribution of the workpiece in the hot forging process. The deformed shape of the workpiece was consistent with the trend of experimental results.
The interaction between thermomechanical parameters and microstructure evolution is so intense that it must be considered during the finite element method (FEM) simulation of the hot plastic working process, for materials that are difficult to deform. Taking the microstructure evolution into account, a novel type of constitutive relationship has been put forward for the IN718 alloy. The microstructure evolution model was first established for the dominant microstructure evolution processes. Then the microstructure evolution models and the method to determine the local flow stress of the corresponding microstructure for current thermomechanical parameters and deformation history were presented. Once the local flow stresses of different structures and their volume contributions were defined, the apparent flow stress of the material could be determined as the weighted sum of the local flow stresses and volume contributions. To validate the proposed method, a thermoviscoplastics and microstructure evolution coupled analysis for a forging process of a critical IN718 disk forging was performed. The predicting results were in close agreement with the experimental data.
Metal undergoes complicated microstructural evolution during hot ring rolling (HRR), which determines the quality, mechanical properties and life span of the ring formed. In this paper, a three-dimensional rigid–plastic and coupled thermomechanical finite element model for HRR was developed and combined with a microstructural evolution model of AISI 5140 steel, on the basis of a DEFORM 3D software platform. The material’s microstructural evolution in the HRR process was thoroughly studied, and the effects of forming parameters (rotational speed of the driving roll, feed rate of the idle roll, initial temperature of the ring and friction factor) on the volume fraction of dynamic recrystallization (DRX), DRX grain size, the volume fraction of recrystallization and average grain size were investigated. The results obtained provide a guide for the quality and process control of HRR.
In order to control microstructure of heavy forgings, a robust parameters control methodology based on Taguchi method and numerical simulation was proposed. Uniform and small microstructure of final forging was considered into the objective function. Optimal parameters were acquired through S/N analysis. The analysis of variance indicates that, for cylinder two-step upsetting, the most significant parameters affecting the microstructure are forging temperature and ingot height to diameter ratio. The virtual experimental result agrees with the predictive value well. This method avoids large number of simulations and can be used to control the microstructure of heavy forgings.
The effects of hot working variables on the microstructural changes during and after deformation of C-Mn, low-alloy, and niobium-treated HSLA steels are critically examined. Relationships describing the onset of dynamic recrystallization, the kinetics of static recrystallizatio9n, and the grain size developed by static recrystallization and grain growth in terms of the initial microstructure and the conditions of hot working are derived from available laboratory observations. These relationships are used to predict the evolution of microstructure during plate and strip rolling operations and to estimate the ferrite grain size expected after transformation during cooling.
Introduction Metal forming process Analysis and technology in metal forming Plasticity and viscoplasticity Methods of analysis The finite element method (1) The finite element method (2) Plane-strain problems Axisymmetric isothermal forging Steady state processes of extrusion and drawing Sheet metal forming Thermo-viscoplastic analysis Compaction and forging of porous metals Three dimensional problems Preform design in metal forming Solid formulation, comparison of two formulations, and concluding remarks Index.
An automatic remeshing scheme has been developed to enable finite element simulation of complicated forming processes. In order to avoid the tedious procedures of interrupting the analysis, performing rediscretization, mapping of current state variables and preparing the new set of boundary conditions, a fully automatic remeshing method is described. The different steps of this method are presented with the help of one industrial example.
The objective of this study is to demonstrate the ability of a computer simulation of the microstructure evolution in the hot forging of C–Mn steel. The development of the microstructure is strongly dependent on process and material parameters that affect the time history of thermomechanical variables such as temperature, strain, and strain-rate during deformation. A model to predict the development of the microstructure has been suggested by many researchers but has usually been applied to the hot rolling process, where dynamic recrystallization can be ignored due to the small deformation involved. In this study, the analysis program combined with a recrystallization model and the rigid–thermoviscoplastic finite element method is developed in order to investigate the microstructure evolution during a hot forging process with large deformation. To show the validity and effectiveness of the developed program, the experiment of hot upsetting is performed, the results of the experiment being compared with those of simulation.
Improving the properties of medium carbon steels with modified post forging treatment The Miner-als
- R Kaspar
- I Gonzalez-Baquet
- J Richter
- G Nußbaum
- A K€
R. Kaspar, I. Gonzalez-Baquet, J. Richter, G. Nußbaum, A. K€ o othe, Improving the properties of medium carbon steels with modified post forging treatment, in: Ch.J. Van Tyne, G. Krauss, D.K. Matlock (Eds.), Fundamentals and Applications of Microalloying Forging Steels, The Miner-als, Metals and Materials Society, Warendale, USA, 1996, pp. 45–59.
Application of a coupled thermo-mechanical model to the numerical analysis of the microstructure development during rolling and cooling of rails
- M Glowacki
- R Kuziak
M. Glowacki, R. Kuziak, Application of a coupled thermo-mechanical model to the numerical analysis of the microstructure development during rolling and cooling of rails, in: Proc. ComplasÕ97, Barcelona, Spain, 1997, pp. 1313–1316.
Development of mathematical models to predict the microstructure evolution during the hot rolling of long products
- P D Hodgson
- R E Gloss
- L O Hazelden
- D Matthews
P.D. Hodgson, R.E. Gloss, L.O. Hazelden, D. Matthews, Development of mathematical models to predict the microstructure evolution during the hot rolling of long products, in: Proc. MicroalloyingÕ95, 1995.
Structural changes in steel during hot rolling
- Hansen
S.S. Hansen, Structural changes in steel during hot rolling, in: G. Krauss, S.M. Baneriji (Eds.), Microalloyed Plate and Bar Product, TMS of AIME, 1987, pp. 439–453.
Optimization of the ferrite-pearlite microstructure of vanadium treated medi-um-carbon steels by means of mathematical modelling of forging processes
- R Kuziak
- M Pietrzyk
- Y Cheng
R. Kuziak, M. Pietrzyk, Y. Cheng, Optimization of the ferrite-pearlite microstructure of vanadium treated medi-um-carbon steels by means of mathematical modelling of forging processes, in: Proc. Symp. Microalloying Forging Steels, Golden, TMS, 1996, pp. 241–253.
Computer simulation of metal flow in die forging
- G Petzov
- N Bontcheva
G. Petzov, N. Bontcheva, Computer simulation of metal flow in die forging, in: E. Manoach, Ya. Ivanov, A. Baltov (Eds.), Proc. IX Congress on Theoretical and Applied Mechanics, vol. 1, Varna, 19–22 September 2001, Bulg. Academy of Sciences, Demetra Ltd, pp. 575–580.
Grain size evolution model of microalloyed austenite under high-temperature deformation
- G Petzov
G. Petzov, Grain size evolution model of microalloyed austenite under high-temperature deformation, J. Mat. Sci. Tech., 2003, in press.
Optimization of the ferrite-pearlite microstructure of vanadium treated medium-carbon steels by means of mathematical modelling of forging processes
- Kuziak
Modeling of Thermomechanical Metal Forming Processes
- G Petzov
Improving the properties of medium carbon steels with modified post forging treatment
- Kaspar