Billet Deformation Research Articles

Disembarkation of a bar titanium billet in the mode of slow flow of the material

The results of CAE modeling of the process of forming an element of a titanium bar billet under hot die forging conditions are presented. Calculations of deformation of bar billets with different sections at different tool rates are presented. The upsetting forces, the stressed state in critical areas of the billet, and the parameters of the deformation process are analyzed. The dependences of the indicators of the stress-strain state of the billet on the rate and force of deformation are obtained. Keywords:upsetting, force, deformation, forming, stress, modeling sulee@mail.ru

Improving the quality of cold-rolled deformable aluminum alloy billets

A mode of high-speed recrystallization annealing has been developed to increase technological plasticity while maintaining the strength of sheet cold-rolled blanks made of deformable aluminum alloys that are not strengthened by heat treatment. Problem. Cold deformation of cold-rolled plates is achieved by recrystallization annealing in hooded furnaces. However, such annealing often does not provide the technological plasticity for defect-free stamping of products and, as a result, has significant rejects. Hooded furnaces are not suitable for improving the deformation of individual billets. In addition, for products with complex configurations that operate in harsh environments, the requirements for rolled aluminum are increased, which is also not possible to realize in open hearth furnaces. These problems can be solved by high-speed continuous parting heat treatment. Goal. The aim is development of a high-speed recrystallization annealing regime for increasing technological plasticity while maintaining the strength of cold-rolled sheet billets from deformable aluminum alloys. Methodology. The object of the study was thin-sheet (1 mm) billets from cold-rolled aluminum alloys AD1, AMts, AMg3. Strip blanks were subjected to high-speed continuous recrystallization annealing using contact heating. The metal was heated at a rate of 5 ºC/c to temperatures from 250 to 400 ºC with an interval of 50 ºC with a holding time of 5 - 15 min at the heating temperature and cooling in air. The quality of the annealing was judged by the nature of the obtained structure and indicators of mechanical properties. The ability to extract metal in different states was evaluated by the Eriksen method. Result. The least energy-consuming modes of continuous high-speed annealing of workpieces from the studied alloys were developed to obtain increased plasticity indicators (while maintaining strength) and improve cold pressure processing in the manufacture of products of complex configuration. Practical value. High-speed recrystallization annealing provides reduction of defects, saving of metal, improvement of productivity in the production of thin-sheet items by the method of cold deformation with deep and complex drawing.

Simulation of continuous local bending-forming process by elastic composite tool

A continuous process of local bending-forming using an elastic composite tool is considered. The basic mathematical dependencies necessary to determine the shapes of the resulting workpiece and tool, as well as the law of tool movement, are given. The parameters of the Mooney-Rivlin model are calculated based on the conducted experiment on the elastic composite material upsetting. The results of modeling the aluminium AMg6 alloy billet deformation by shells made of the SKU-7L polyurethane and composite material are presented.

Numerical simulation of the nickel alloy microstructure formed in the process of hot fogging

The paper presents a comprehensive analysis of the deformation and thermal states of the Waspaloy alloy billet heated to different initial temperatures of 1100°C and 1150°C and subjected to free upsetting to an average diameter of ~1060 mm at the deformation rate of 100 mm/s. The thermodynamic forces acting on the billet trigger the process of dynamic recrystallization, which is associated with the appearance and growth of low-defect nuclei of new grains instead of the deformed ones. To describe the material microstructure evolution, the phenomenological approach implemented in the DEFORM-2D/3D software package was applied. The simulation was based on the modified Johnson - Mehl - Avrami - Kolmogorov (JMAK) model, whose equations allow calculating the volume fraction of recrystallized material and describing the grain structure transformation of metal alloys. The results of solution of the non-stationary temperature problem are used to construct the temperature fields in the Waspaloy alloy billet during its transportation through air from the furnace to the deforming equipment within 45 seconds and during the subsequent upsetting process. For the latter, the force and strain characteristics, including the force required to complete this process, are determined in the framework of the plastic flow theory, and the characteristics of the grain structure of the nickel alloy, such as the average size of recrystallized grains and their volume fraction, are determined in the framework of the JMAK model. The results obtained by numerical simulation make it possible to substantiate an optimal selection of parameters of billet deformation ensuring the formation of the required material structure.

Modernization of screw rolling technology in a multi-roll mill

Analysis of the screw rolling process showed that change in axial speed of the roll along the length of the roll groove of cross rolling mill does not correspond to the required character of change in the speed of deformed billet. The process proceeds under intense axial compression, as a result of which a significant part of the metal crimped in the contact zone is displaced into the inter-roll area. It is shown that direction of the axial force in the corresponding zone of the roll groove depends on the value of inclination angle of the considered roll section generatrix to the rolling axis. The proposed modernization of screw rolling technology makes it possible to carry out deformation of the billet under the influence of intra-focal axial tension. The task is accomplished by rolls calibration when at the beginning there is a ridge section of the roll on which the axial force is directed against rolling direction; and behind it, a pulling one, on which the direction of the axial force coincides with rolling direction. Such a scheme of the axial forces action in the zone of intensive billet reduction creates the most favorable conditions for the metal flow in axial direction. A technical solution is proposed for the implementation of the stage of the billet gripping by rolls, and description of this stage and the process stationary phase is given. The cardinal change in the billet deformation condition after modernization makes it possible to reduce the power load on the work rolls, increase their efficiency and reduce energy costs during rolling. This will ensure the rolling of a solid billet in a roughing mill with a higher stretch, create the preconditions for expanding the size and grade assortment when obtaining rods in radial-displacement rolling mills and at production of pipes in rolling lines with the Assel mill. The range of finished products can be significantly expanded due to the production of thin-walled highprecision pipes.

Study of stress-strain state of thin-sheet billet during its deformation by new composite working tool

The results for solving of the finite element problem of thin-sheet billet deformation by composite and simple elastic working tool based on SKU-7L polyurethane are presented. Comparative analysis of the obtained results is performed. The technological improvement for obtaining process of the thin-sheet products— elements of flat heat exchangers, decorative panels and similar thin-sheet products is presented.

Research of technology of manufacturing of steeply curved bends

Purpose of work. Investigation of the features of the technological process of manufacturing curvilinear sections of the pipeline – steeply curved bends.
 Research methods. Three-dimensional modeling of a design of equipment and a finished product; experimental studies of the technology of manufacturing steeply curved bends by pushing through a curved hole of the assembly matrix without using fillers; estimation of deformation by the method of dividing grids.
 Obtained results. Literary sources are analyzed and the main problems arising in the manufacture of steeply curved bends for each method are identified. To study the features of the manufacturing technology, a three-dimen­sional model of the assembly matrix was modeled using the investigated method, the design, dimensions and material of the tooling were selected. Equipment was made. Sizes and material of pipe billets were selected. The operations of the technology for the manufacture of steeply curved bends by pushing through a curved hole of the assembly matrix without the use of fillers were determined.
 Experimental studies of the technology have been carried out. For this, the manufactured stamp was installed on a PG-100A hydraulic press. Pipe billets were placed in a guide sleeve, which was screwed to the assembly die when the press rod was placed in the upper position. The punch pushed the pipe billet along the curved hole of the assembly matrix while moving the rod down. Upon completion of the pushing process, the press rod was in the upper position. For unimpeded removal of the finished product, the guide sleeve was removed, the matrix was unscrewed and removed from the clamps.
 Several samples were obtained, the presence of defects and problems that arose during the formation of steeply curved bends were revealed. To assess the deformation, the method of dividing grids was used.
 Scientific novelty. The method of manufacturing steeply curved bends by pushing an assembly matrix through a curved hole was further developed. The peculiarity of the investigated technology - rejection of the use of expensive filler or rigid mandrels, reduction of technological operations and time for manufacturing a unit of a finished product. As a result of the study, dangerous zones of pipe billets in the process of manufacturing steeply curved bends were identified: the place of bending (crushing, corrugation, rupture) and the ends of the finished product at the exit (ovalization, distortion, breaks).
 Practical value. To prevent the occurrence of dangerous zones during deformation of pipe billets and improve the quality of the finished products obtained, requirements were formulated for the design of the working elements of the developed stamp, the choice of optimal modes of the shaping process, the material and the optimal shape of the pipe billet.

Numerical investigation of thermo-mechanical behaviour and microstructure evolution of a nickel alloy workpiece during its upsetting

The use of science-based technologies in commercial production makes it possible to obtain high-quality, competitive finished products. The development of new techniques or optimization of existing technological processes involving the in-depth experimental research requires large time and material costs. In this regard, numerical simulation of the technological process under study can be used as an alternative to a physical experiment. The results obtained by numerical methods will make it possible to substantiate the most appropriate regime of billet deformation, providing the required changes in the structure of the material. This paper considers a specific technological process of hot forming of massive billet consisting of two stages: air cooling of the billet while transporting it from the furnace to deforming tools and forming operation - free upsetting of a billet with the aid of a moving upper flat plate and a stationary cutting lower plate. Computer simulation of upsetting of a large billet with the aim to define a change in its shape, temperature distribution over the surface and throughout the billet, and deformation inhomogeneity arising in the process of got forming was carried out using the Deform-2D/3D software package. The initial temperature distribution of material during pressure forming is determined by modeling air cooling of the billet for 45 seconds during its transportation from the furnace to the deforming equipment. For the obtained inhomogeneous temperature distribution, the calculations were performed to evaluate the force required for billet upsetting to the technology specified average diameter of about 1060 mm at the velocity of the die movement of 100 mm/s. Thee Johnson-Mehl-Avrami-Kolmogorov (JMAK) model was used to investigate the evolution of the microstructure (average grain size and recrystallized volume fraction) of the Waspalloy nickel alloy generated as a result of dynamic recrystallization in the process of hot forming of a billet at the strain rate of 100 mm/s.

Critical Degree of Billet Deformation in Closed Gauges of a Tube-Forming Mill

A comprehensive stress-strain analysis of a tube billet during the forming on modern tube-forming mills of different types is performed using the finite element simulation. The main forming issues are highlighted and a complex approach to their solution is proposed. The rationality criteria of a deformation mode are established. The mode which allows reducing the metal consumption and increasing the product yield of electrowelded tubes of general and oil-gas purposes is developed. This mode also enables expanding the dimensional range towards thin-walled tubes and the steel-type range towards high-strength steels.

Improving Efficiency of the Surface Plastic Covering Deformation of Billets from Aluminum Alloys

Improving Efficiency of the Surface Plastic Covering Deformation of Billets from Aluminum Alloys

Billet flow formation of discontinuous carbon fiber ribbed square panels from continuous carbon fibers

This paper presents a newly-developed billet flow formation method, which produces discontinuous carbon fiber thermoplastic ribbed panels by using the die cushion motion of a press. Billets of discontinuous fiber reinforced thermoplastic were extruded into rib cavities by die cushion motion while press-forming a panel of continuous fiber reinforced thermoplastic. Using billet flow formation, 200 mm long, 46 mm high, 1.4 mm thick ribs comprised of 30 mm long discontinuous fibers were formed on 400 mm wide, 300 mm depth, 50 mm high panels. The rigidity of a ribbed panel was five times greater than a panel without ribs. The tensile strength of the formed ribs was approximately 250 MPa, the same strength of the material before forming. Material behavior such as fiber flow and billet deformation during formation is discussed. This study has shown that the billet flow formation can create ribs with high mechanical strength using only a press with a die cushion.

Heat Transfer Characteristics of Billet/Die Interface and Measures to Relieve Thermal Stress for Hot Forging Die

The interfacial heat transfer coefficient (IHTC) shows the heat transfer capacity at the billet/die interface during the hot forming process, which affects the temperature gradient in the die that may potentially induce high thermal stress. Consequently, this determines the service life of the die. In this paper, a set of experimental equipments were used to identify the IHTC and the upsetting test of superalloy Inconel718 (GH4169) was carried out on the hot flat die to evaluate the IHTC characteristics after the billet heating and die preheating temperature, holding time, and billet deformation rate. The results indicated that the billet heating temperature has a minimal role in IHTC but the other components have a great impact on IHTC. Among them, the billet deformation rate has influenced the IHTC the most. In the die preheating temperature ranging from $$150\,^{\circ }\hbox {C}~\hbox {to}~400\,^{\circ }\hbox {C}$$ , it was found that the preheating temperature was proportional to IHTC. A high preheating temperature that leads to a high IHTC was found unfavorable in relieving the die surface thermal stress, and also weakened the die hardness and strength. The IHTC declined with the increase in the holding time as a result of the billet oxidation. Based on these findings, the composite ceramic and polymetallic heat-resistant coatings on the die surface were prepared, respectively, to relieve the thermal stress of die surface by reducing IHTC. It showed that both of the treated dies could effectively reduce the IHTC, blocking the transferred heat from the hot billet and making it applicable to the different hot forging events.

Determination of interfacial heat transfer coefficient for TC11 titanium alloy hot forging

In this paper, based on self-developed experimental apparatus, the upsetting test of TC11 titanium alloy on the hot flat die was conducted and Beck’s nonlinear inverse estimation method was adopted to calculate the interfacial heat transfer coefficient (IHTC) and the change rules of IHTC following billet deformation rate, average interfacial temperature and holding time were investigated respectively. Experimental results indicate that IHTC increases with the increase of deformation rate as a whole, and the billet deformation heat and interfacial friction heat during forming that remarkably contribute to IHTC and the contributions by heat conduction to IHTC is differ from that by friction; the glass lubricant coated on the billet surface that weakens the heat transfer situation in the early stage of forging, however, this blocking effect of lubricant on IHTC soon vanishes with increasing deformation rate and it enhances the interface heat transfer later; the average interfacial temperature impacts on IHTC in many aspects and a high average interfacial temperature IHTC corresponds to a high IHTC when the deformation rate is certain, but this changing trend is not monotonous; the IHTC decreases with the increase of holding time due to oxidation. After certain holding time, the IHTC is only related to temperature and pressure in the absence of deformation rate, and the influence of pressure on IHTC is larger than that of temperature on it.

Effect of deformation rate on interfacial heat transfer coefficient in the superalloy GH4169 hot forging process

To evaluate the effect of billet deformation rate on the interfacial heat transfer coefficient (IHTC) during hot forging process, the upsetting test of wrought superalloy GH4169 on the hot flat die was conducted. The inside temperature field data of the billet and lower die under the deformation rate of 0s−1, 0.04s−1, 0.08s−1, 0.1s−1, 0.2s−1, 0.4s−1 were respectively collected through using a multi – channel data acquisition system. Besides, Beck’s nonlinear inverse estimation method was adopted to calculate IHTC and analyze the effect of GH4169 deformation rate on IHTC. According to the research results, the deformation rate had a distinctive influence on IHTC. When the deformation rate φ̇z⩽0.08s-1, the IHTC is small due to the blocking effect of the oxide scale on heat transfer; but when φ̇z>0.1s-1, the oxide scale was exfoliated in layers under the action of shearing force and a great deal of deformation heat and friction heat have been generated in short time, which has made the heat transfer condition improve greatly. Finally, the peak value of IHTC correlates approximately with deformation rate by a Boltzmann function, and tends to be saturated when the deformation rate φ̇z>0.2s-1.

An Investigation on the Deformation Heating in Billet and Die During Equal-Channel Angular Pressing and High-Pressure Torsion

This work aims to investigate the temperature rise in Aluminum alloy 6061 due to deformation heating in equal channel angular pressing (ECAP) and high-pressure torsion (HPT) processes using finite element method. The roles of various parameters are investigated and the heating of ECAP die due to billet deformation is included in the simulations. The results show that while the work-piece moves in the exit channel, the generated heat is transferred to die via conduction and therefore the temperature isosurfaces in die are extended in the direction of inlet and exit channels. The dependency of maximum work-piece temperature to velocity is more than its dependency to friction. Increasing the plunger velocity increases the difference between maximum and minimum temperatures. Additionally, the maximum work-piece temperature is attained at the deformation zone. The temperature rise in HPT is less than ECAP due to the small size of the HPT work-piece compared to ECAP. Not only the work-piece size, but also the good heat conduction of aluminum makes the temperature distribution roughly uniform in HPT.

A New Cold Rotary Forging Technology for Automotive Starter Guiding Cylinder with Internal Helical Involute Spline

A new cold rotary forging technology of the internal helical involute spline was presented based on an analysis of the structure of automotive starter guide cylinder. 3D rigid-plastic finite element model was employed. Billet deformation, Billet equivalent stress and forming load were investigated under the DEFORM 3D software environment, then the forming process parameters were applied in the forming trials, and the simulation results are conformed with the experimental results. The validity of 3D finite element simulation model has been verified. The research results show that the proposed cold rotary forging technology can be efficient in handling of the forming manufacturing problems of automobile starter guide cylinder with internal helical involute spline.

Analysis of Aluminum Extrusion in a 90<sup>o</sup> Die by Finite Volume Method

Nowadays, the finite element method is still the first choice of researchers in metal extrusion analysis. However, recent published papers have also supported that metal plastic flow can be modelled by the flow formulation, employing the finite volume method. In this work, the numerical scheme presented by Martins et al. [16] based on finite volume method together with the explicit MacCormack numerical method, was used to analyse aluminum axisymmetric direct extrusion in a 90° die. A structured, fixed and collocated mesh and numerical convergence based on the SIMPLE method were employed to attain pressure-velocity coupling. The main goal of present numerical scheme was to obtain the axial and radial velocities and pressure distributions. From these results, it was possible to obtain and identify the dead zone inside the billet deformation region in direct extrusion of aluminum in a 90° die. The field variables results shown in present work had good agreement when compared with those from literature.

Deformation Characteristics and Mechanism of Martensitic Stainless Steel during Thixoforming

Semi-solid billet of 9Cr18 martensitic stainless steel with globular grains was made by a wavelike sloping plate experimental device, and hot compression tests were carried out in the semi-solid state of 9Cr18 semi-solid billet on Gleeble-1500 thermal simulation testing machine at the temperatures of 1250°C ~1300°C and the strain rates of 0.1 s-1~5.0 s-1to investigate the effects of thixoforming parameters on its deformation characteristics and mechanism. According to the true stress-strain curves obtained from the test, the influence of deformation temperature and strain rate on 9Cr18 semi-solid billet deformation resistance was investigated, and the deformation resistance model of specimen with coexistence of solid and liquid phases was established. In this paper, it was found that deformation mechanism changed because of different deformation temperature and strain rate. Dynamic recrystallization occured at 1250°C in different phases separately. So that big fine recrystallized grains were achieved at the soft primary austenite region while small recrystallized grains were achieved at the hard solidified liquid region. The melted metal would be extruded from the centre of the specimen to the free surface completely when the temperature was higher than 1275°C. And then specimen became FGM (functionally graded materials), with phases and properties graded distribution perpendicular to the stress direction. When thixoforming temperature reached 1300 °C, martensitic transformation occurred after rapid cooling. The mathematics models of the relation between stress and temperatures, fraction of solid, deformation rates and deformation degree of 9Cr18 semi-solid billet were regressed and established based on the dates attained from the compression deformation experiments. The R value was 0.991, and the RMSE value was 3.57.

Local plastic deformation of hollow billets

The plastic deformation of the segment of a hollow billet the sizes of which are small as compared to the total billet size is considered. The deformation force and power are determined.

A Combined Radial Forging-Forward Extrusion Forming Process of Alternator Poles

A combined radial forging-forward extrusion forming process of alternator poles is proposed based on an analysis of the structure of alternator poles as well as the forming die sets. First, a thick-bottom base of the alternator poles is obtained through radial forging. The middle boss and claw teeth are then formed through forward extrusion. A 3D coupled thermomechanical finite element model is employed. Billet deformation, metal flow, and forming load are obtained. The results show that the middle boss cavity is filled earlier and the process is no longer simultaneous extrusion during the second forming step. Then, the forming load increases sharply. An improved process that controls the metal flow in the middle boss cavity and aids in pushing the metal into the corners of the claw teeth cavity is proposed. The middle boss and claw teeth cavities can be filled simultaneously. The sharp increase of the forming load in the final forming stage is avoided. Simulative and experimental results show that the improved process can considerably reduce the final forming load to form a well-shaped product.