Large Size Forgings Research Articles

Improving the Accuracy of Die Impression Milling for Large-Size Forgings of Heavy-Duty Vehicle Parts

Improving the Accuracy of Die Impression Milling for Large-Size Forgings of Heavy-Duty Vehicle Parts

Improving the accuracy of milling engravings of dies of large-sized forgings of heavy-duty vehicle parts

The methodic of experiments and construction of a model for control of the geometric accuracy indicators of forgings of massive parts of complex shapes is considered based on an experimental study of the wear of spherical end mills when processing of samples from dies material. The resulting models were used to adjust the tool path. Keywords:milling, die, geometric accuracy, modeling, spherical end mill, wear Safarov-dt@mail.ru, Kpfu.ktomp@yandex.ru

I solution of the heat conduction problem for computational modeling of the hydrogen content reduction in large-size forgings during antiflocken heat processing

The paper investigates problems of flocken formation in large-sized billets during heat treatment increasing hydrogen degassing. The solution of thermal conductivity problem is given, the estimation of thermal cycles at preliminary heat treatment for the subsequent solution of hydrogen diffusion problem is carried out on the example of medium-alloyed steels of 5KhNM and 20Kh3NMFA grades.

Influence of Spacers and Skid Sizes on Heat Treatment of Large Forgings within an Industrial Electric Furnace

The influence of stacking patterns, through the different spacer and skid sizes, on the transient temperature distribution uniformity of large-size forgings in a 112-m3 electrical heat treatment furnace was investigated by conducting CFD simulations and real-scale experimental validation. A 3D CFD model of the electrical furnace was generated, including a heat-treating chamber, axial flow fans, large size blocks, skids, and spacers. Real-scale temperature measurements on instrumented test blocks during the heat treatment process were carried out to validate the CFD simulations. Results indicated that the CFD model was capable enough to determine the transient temperature evolution of the blocks with a maximum average deviation of about 6.62% compared to the experimental measurements. It was found that significant temperature non-uniformities of up to 379 K on the surfaces of the blocks due to the non-optimum stacking pattern were experienced by the blocks. Such non-uniformities could be reduced between 24% to 32% if well-adapted spacer and skid sizes were used in the stacking configurations. Based on simulation results and experimental validation work, optimum spacer and skid sizes for uniform temperature distribution were proposed for different stacking patterns.

Elaboration of Parameters of Large-Size Rings Production Process Taking into Account the Evolution of Material Relative Density

The paper presents the selected problems in production chain of large-size rings for the offshore industry. There are two goals of the technology: 1) to obtain the correct shape of the rings, 2) to achieve required properties. A significant problem in the processes of large size forgings production is a proper prediction of the as-cast structure defects and their behaviour during deformation (forging). This study examines a method of prediction of relative density changes of the material during forging. Experimental procedure includes a forging test at the laboratory scale and numerical modelling. These results as well as boundary conditions were used as input data for the computer simulations of the large rings production processes. The presented procedure allows for a comprehensive analysis of the production process of large-size rings, taking into account areas with insufficient material compaction. The analysis allows for changes in the production chain at the design stage, which significantly reduces the costs associated with pre-implementation tests.

Optimization of furnace residence time and loading pattern during heat treatment of large size forgings

A combination of unsteady 3D CFD simulations and experimental temperature measurements was employed to determine the effect of loading patterns on the temperature distribution within steel forgings inside a gas-fired heat treatment furnace. This was aimed to obtain a more homogenous temperature distribution. Besides, a hybrid methodology using 3D numerical simulations and a high-resolution dilatometer allowed improving residence time of forgings inside the heat treatment furnace. The influence of the loading patterns and skids on temperature distribution and residence time of forgings was examined using thermal analysis four different loading patterns. Comprehensive unsteady thermal analysis of the products heating allowed quantifying the impact of skids usage and their dimensions on the extent of the uniformity of temperature distribution. The results were interpreted in terms of the inter-relationship between the skids usage, their geometry, absorbed radiation, and convective heat fluxes. The analysis showed that temperature non-uniformities of up to 331 K could be produced for non-optimum loading patterns. Using the developed CFD approach, it was possible to reduce the temperature non-uniformity of different sizes of blocks up to 32% via changing the loading pattern inside the furnace. Further, the slab’s residence time was improved by almost 15.5% when employing the proposed hybrid approach. This approach could directly be applied to the optimization of different heat treatment cycles of forged blocks in different grades of steels.

Development of technique for determining of stamping hammer blow efficiency

The multiple-stage process of large-sized turbine blade blanks on steam-air die-forging hammer is considered. Mathematical modelling of the stamping process of large-sized turbine blade on falling parts 25 t mass stamping hammer is carried out. Measurements of the number of hammer blows and the under-stamping of blade blanks at each stage of the technological process are performed. Method for determining of the hammer blow efficiency is developed. Diagram of the force—displacement of falling parts 25 t mass hammer is constructed. The dependence of the blow efficiency of falling parts 25 t mass hammer is obtained, with can be used in mathematical modelling of the stamping processes of large-sized forgings on this hammer.

ПРИМЕНЕНИЕ КОМПЬЮТЕРНОГО МОДЕЛИРОВАНИЯ ДЛЯ ОПРЕДЕЛЕНИЯ ВЛИЯНИЯ ПАРАМЕТРОВ ЗАКАЛКИ НА ГЕОМЕТРИЮ ШТАМПОВОК ИЗ АЛЮМИНИЕВОГО СПЛАВА АК6

The article presents the results of a study, the purpose of which is to optimize the technology of manufacturing large-sized forgings with high and thin longitudinal and transverse ribs from the AK6 aluminum alloy. Simulation of the process of quenching of these stampings was carried out in the QForm VX software package. The influence of the hardening parameters (the method of placing the stampings on quenching, the absence / presence of false ribs, the water temperature during quenching) on the final geometry of the stampings has been established. Recommendations are formulated for optimizing the manufacturing technology of this type of stampings and useful information is obtained for further experimental research.

Study of the properties of large-sized blanks of turbine blades made of 15Kh11MF-Sh steel depending on the method of obtaining the initial metal

We consider the manufacturing process of forgings for turbine blades of extra-large dimensions (length >2 m) from electroslag remelting steel 15H11MF-Sh. With an increase of the workpiece dimensions (weight >450 kg), we face the problem of choosing the technology for obtaining the original billet. The production technology is known to affect the structure of the material and, as a consequence, the final properties of the product. We present the results of studying the influence of the method of obtaining the original metal blanks (hot-rolled steel bars and forged billets) on the properties of large-sized forgings of turbine blades. The mechanical characteristics, microstructure properties, chemical composition and content of δ -ferrite were determined by examining the initial samples of long products and forged rods. It is shown that billet in the forged state exhibit higher strength characteristics. However, after the stamping process, the properties of the blades equalize, i.e., after stamping and heat treatment, the same structure is formed, regardless of the method of obtaining the original workpiece. The results obtained can be used in the serial production of large-sized turbine blades of a new profile.

Forecasting Increase of Quality of Large-Sized Forgings Used for Stamping, Piercing, and Rolling of High-Duty Products

When utilizing current combined systems of manufacturing large-sized shaft forgings, there is a tendency towards using an integrated approach, which consists in optimizing the shape of forged ingots and methods of their forging, intensifying shear strains in the axial zone of the ingots during their plastic deformation, and eliminating asymmetry of external forces at various points along the cross section of the ingot being deformed. This paper presents the results of the comparative analysis of quality of shaft forgings when forging ingots with a three-beam symmetric and asymmetric cross-section, as well as with the traditional octahedral cross-section, are used for the manufacture of shaft forgings. It has been shown that the use of forging ingots with a three-beam symmetrical and asymmetrical cross section provided an increase of KCU by an average of 4.3% and 13.1%, and of density by 17.5% and 21.0%, respectively, in the absence and presence of inert gas (argon) blowdown of the melt in the casting ladle before casting it into ingot molds. Their use also contributes to an increase in the number of forgings, suitable for ultrasonic testing, according to the C/c class with a permissible equivalent discontinuity diameter of ≤ 3 mm.

ИССЛЕДОВАНИЕ МЕХАНИЧЕСКИХ СВОЙСТВ И СТРУКТУРЫ КРУПНОГАБАРИТНЫХ ПОЛУФАБРИКАТОВ ИЗ ТИТАНОВОГО СПЛАВА ВТ6ч

The article presents the results of a complex of studies (analysis of microstructure, as well as determination of mechanical properties under tension, impact strength (KCU), low-cycle fatigue (LCF), fracture toughness (K1с)) of large-sized forgings made of titanium alloy Vt6сh, providing for the final deformation in the (α+β)-region, as well as large-sized profiles and stamping made of titanium alloy Vt6сh, providing for the final deformation in the β-region. A comparative analysis of the data obtained during the research shows the dependence of the mechanical properties of semi-finished products with plate-like structure on the size of the structural components – of primary β-grains and colonies of α-plates. This is especially noticeable for the characteristics of plasticity.

Development of a new process for expanding stepped tapered rings

A new method for expanding large-size tapered rings with a stepped profile has been considered. The proposed method consists in expanding the blank with the help of a stepped die. A procedure for conducting studies by the method of finite elements was proposed. The procedure is intended to determine dependences of the stress-strain state and shape change during the expanding process by means of a stepped die. Variable parameters included relative height of the stepped blank protrusion which varied in the range of 2.2...2.5. Based on the finite-element modeling, distribution of deformation rate in the forging section after expanding with the help of a stepped die was established. The forging taper formed by expanding in this way was determined. Results of finite-element modeling were verified by experimental studies with lead and steel specimens. A procedure for conducting experimental studies was proposed. The finite-element modeling has allowed us to establish that expanding with the help of a stepped die results in a tapered forging shape. This is explained by the fact that when the wall is reduced, tangential deformation of the annular blank in the wall zone is larger than that in the protrusion zone because of different height of the stepped blank. The results of finite-element modeling were confirmed by experiments in laboratory conditions with lead and steel specimens. Increase in diameter of the blank protrusion leads to an increase in rate of the protrusion deformation which causes an increase in diameter of the protrusion bore. Analysis of macrostructure of the annular forging with a tapered stepped profile has made it possible to establish that when the stepped blank is shaped with the help of a stepped die, metal fibers repeat the target part contour which prevents their cutting during machining. The study has established that expanding of stepped tapered blanks is realizable. It expands technological potentials of the process of expanding large-sized forgings

Experimental and unsteady CFD analyses of the heating process of large size forgings in a gas-fired furnace

Comprehensive unsteady analysis of large size forged blocks heating characteristics in a gas-fired heat treatment furnace was carried out employing experimentally measured temperatures and computational fluid dynamics (CFD) simulations. Heat and fluid flow interactions, consisting of turbulence, radiation and combustion, were simultaneously considered using k-ε, DO and EDM models in a three dimensional CFD model of the furnace, respectively. Applicability of the S2S radiation model was also evaluated to quantify the effect of participating medium and radiation view factor in the radiation heat transfer. Temperature measurements at several locations of an instrumented large size forged block and the furnace chamber were performed. A maximum deviation of about 7% was obtained between the model predictions and the experimental measurements. Results showed that despite the unloaded furnace had uniform temperature distribution, after loading, product surfaces experienced different heating rates, resulting in temperature differences up to 200 K. Findings were correlated with furnace geometry, vortical structures and flow circulations around the workpiece. Besides, S2S model demonstrating reliable results highlighted the importance of radiation view factor optimization in this application. The study could directly be employed for optimization of the heat treatment process of large size steel components.

Influence of initial microstructure and grain size on transformation of bainite to austenite in large size forgings

The kinetics of austenite formation in the surface and center regions of a 40 t forged ingot of a high-strength medium-carbon low-alloy steel was studied using high-resolution dilatometry. The starting microstructures from the surface or center regions had different proportions of bainite and residual austenite as well as different prior austenite grain sizes. Two heating rates representing the actual heating rates in the surface (5 °C s−1) and center regions (0.5 °C s−1) of large size forged blocks were utilized. Dilatometric curves revealed only one transformation step of austenite formation at both heating rates independent of grain size or proportion of phases. Optical microscopy, field emission gun scanning electron microscopy and X-ray diffraction were used to study microstructure evolution and confirm the results obtained by dilatometry. The kinetic parameters for austenite formation were determined from the dilatometry data by Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation. The JMAK coefficients were determined for each condition of the investigated steels. The calculations indicated that the nucleation and growth of austenite in the surface region were accelerated more than 10,000 times due to a significantly smaller average prior austenite grain size, stability of initial retained austenite, and accumulation of coarse carbides at the surface. The results were discussed in the framework of classical nucleation and growth theories using the kinetic parameters for austenite formation.

Effect of Semisolid Metal Casting of Large Forging Ingots on Quality of Large-Sized Forgings Produced

The paper reports the findings on the effect of various casting methods on the quality and development of primary dendritic structure in large-sized forging ingots of steel 38ХН3МФА. One ingot was teemed as per a conventional teeming method while the other was teemed with an inoculated metal stream. It was established that the dendritic parameter value in the inoculated ingot is much smaller than that in the conventional ingot. Consequently, the solidification process occurs at a higher rate in the inoculated ingot compared with that in the conventional ingot, and this assumption is supported by a more homogeneous dendritic structure. It is demonstrated that disperse inoculants positively affect the structure, physical and chemical homogeneity as well as the mechanical properties of cast metal. This finding is clearly supported by the examination of the forgings made of the conventionally teemed ingot and the one teemed with an inoculated stream. When inoculants were introduced in the metal stream, total chemical heterogeneity increased on the average by 1.2-2 times. It is established that the best results for the inoculation casting method are achieved when 2.4-2.6% inoculants are introduced in the stream. Such quantity of inoculants forms at a distance of 5 meters between the guiding pipe and the hot top.

ВЛИЯНИЕ РЕЖИМОВ ОТЖИГА НА СКЛОННОСТЬ К ХРУПКИМ РАЗРУШЕНИЯМ КРУПНОГАБАРИТНЫХ ПОКОВОК ИЗ ВЫСОКОПРОЧНОЙ КОРРОЗИОННОСТОЙКОЙ СТАЛИ 18Х13Н4К4С2АМ3

ВЛИЯНИЕ РЕЖИМОВ ОТЖИГА НА СКЛОННОСТЬ К ХРУПКИМ РАЗРУШЕНИЯМ КРУПНОГАБАРИТНЫХ ПОКОВОК ИЗ ВЫСОКОПРОЧНОЙ КОРРОЗИОННОСТОЙКОЙ СТАЛИ 18Х13Н4К4С2АМ3

Modelling of transient temperature field and phase transformation change a way for residual stress management in large size forgings

The paper is devoted to development of the modelling approach based on 3D finite-element (FE) analysis of the transient temperature fields and the thermally induced phase transformations as a way towards residual stress management in large size forgings. Heating, holding and cooling stages are under consideration and modelling of both the austenite formation and decomposition are taken into account. The thermal-mechanical FE model capable of taking into account changes in the specific volume during ferrite/austenite transformation is coupled with the relevant phase transformation model in order to allow simulation of the transient stresses due to both thermal contraction and the dilatometric effect. The model is capable of taking into account different boundary conditions for the heat transfer problem based on the available data. To improve the predictive abilities, the following two commercial FE codes, such as MSC Marc 2013.1.0 and Abaqus/Standard6.12, are used for solving the non-steady state 3D problem of the metal expansion/contraction during consecutive heating, holding and cooling stages. Although all the mentioned process steps are considered, the model is dedicated to be used for modelling the cooling stages of large forgings and castings.

Optimization of control methods for the structure of large-size forgings of austenite steels for the equipment of nuclear power plants

The effect of the chemical composition and temperature-deformation modes of hammering on the structural state of grade 08Kh18N10T steel is investigated. The obtained data are the base for the development of a complex of technological measures directed toward the production of a homogeneous finegrained structure (no coarser than 3 points on a scale of 3 of GOST (State Standard) 5639) in large-size forgings for parts of nuclear power plants.

Adaptive compliance control of a hydraulic manipulator in free forging

The increased demand for large size forgings has led to developments and innovations of heavy-duty forging manipulators. Besides the huge carrying capacity, forging manipulators should possess robot features, such as force perception, delicacy, and flexibility. The aim of this work is to develop a practical compliance control method for hydraulic forging manipulators. A hybrid force–position control method is proposed and performed on a novel serial–parallel forging manipulator designed by the author’s institute. A specific study is carried on a hybrid pressure–position control system. The simulated and experimental results show the control method is feasible. The experiment on hybrid control is executed on a programmable logic controller considering industrial applications.

Intelligent Control of a Novel Hydraulic Forging Manipulator

The increased demand for large-size forgings has led to developments and innovations of heavy-duty forging manipulators. Besides the huge carrying capacity, some robot features such as force perception, delicacy and flexibility, forging manipulators should also possess. The aim of the work is to develop a heavy-duty forging manipulator with robot features by means of combination of methods in mechanical, hydraulic, and control field. In this paper, through kinematic analysis of a novel forging manipulator, control strategy of the manipulator is proposed considering the function and motion of forging manipulators. Hybrid pressure/position control of hydraulic actuators in forging manipulator is realized. The feasibility of the control method has been verified by the experiments on a real prototype of the novel hydraulic forging manipulator in our institute. The intelligent control of the forging manipulator is performed with programmable logic controller which is suitable for industrial applications.