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The article presents a comprehensive review of key issues and challenges related to enhancing the durability of hot forging tools. It discusses modern strategies aimed at increasing tool life, including modifications to tool materials, heat treatment, surface engineering, tool and die design, die geometry, tribological conditions, and lubrication. The review is based on extensive literature data, including recent publications and the authors’ own research, which has been implemented under industrial conditions at the modern forging facility in Forge Plant “Glinik” (Poland). The study introduces original design and technological solutions, such as an innovative concept for manufacturing forging dies from alloy structural steels with welded impressions, replacing traditional hot-work tool steel dies. It also proposes a zonal hardfacing approach, which involves applying welds with different chemical compositions to specific surface zones of the die impressions, selected according to the dominant wear mechanisms in each zone. General guidelines for selecting hardfacing material compositions are also provided. Additionally, the article presents technological processes for die production and regeneration. The importance and application of computer simulations of forging processes are emphasized, particularly in predicting wear mechanisms and intensity, as well as in optimizing tool and forging geometry.

In this paper, an automatic WAAM technology is proposed to realize the gradient additive remanufacturing of ultra-large hot forging dies. Firstly, a vertical additive manufacturing strategy and a normal additive manufacturing strategy are proposed to meet different additive manufacturing demands. Secondly, the basic principle of layering design of ultra-large hot forging dies is developed, and the wear resistance of Ni-based, Co-based, and Fe-based alloys at room temperature and high temperature is analyzed. The Co-based alloy has the best high-temperature wear resistance, which can be used on the surface of the hot forging die to strengthen the die. In order to control the forming quality of additive manufacturing, the relationship between welding parameters and weld shape was discussed, and the reverse system of welding process parameters was built. Finally, a typical aviation ultra-large hot forging die is selected as the research object. According to different stress and temperature distribution in different regions of the ultra-large hot forging die in service, materials with different properties are used in corresponding regions to improve the service life of the die, reduce the remanufacturing costs, and improve the remanufacturing efficiency. The experimental results show that the service life of the hot forging dies repaired by the automatic gradient function WAAM technology is significantly increased, the material is reduced by more than 50%, and the production efficiency is increased by more than 50%.

Wire and arc additive remanufacturing (WAAR) technology has become a new solution for hot forging dies repair and remanufacturing. In this study, a path generation method is proposed for WAAR of hot forging dies. At first, a WAAR process of the hot forging die is presented, and considering the characteristics of large welding heat input and complex 3D digital model, the hybrid path planning strategy is confirmed as an appropriate strategy for WAAR. The developed hybrid path generation method for WAAR consists of three main steps: determine the direction of the scan line; divide and fill the internal area; and connect the sub-paths. The relatively optimal scanning direction is determined by calculating the length and inclination angle of each line segment in the contour lines, which reduces the possibility of sharp angles. The internal region is divided according to the position of the selected extreme points, and the path space is adjusted to avoid the occurrence of the unfilled phenomenon. At the stage of sub-path connection, some criteria are proposed to reduce the number of sub-paths. At last, the effectiveness and robustness of the proposed method are validated through the planar deposition experiment and the WAAR process of four damaged hot forging dies.

Traditional fatigue fracture theory and practice focus principally on structural design. It is thus too conservative and inappropriate when used to predict the high-cycle fatigue life of dies used for metal forming, especially cold forging. We propose a novel mean stress correction model and diagram to predict the high-cycle fatigue lives of cold forging dies, which focuses on the upper part of the equivalent fatigue strength curve. Considering the features of die materials characterized by high yield strength and low ductility, a straight line is assumed for the tensile yield line. To the contrary, a general curve is used to represent the fatigue strength. They are interpolated, based on the distance ratio, when finding an appropriate equivalent fatigue strength curve at the mean stress and stress amplitude between the line and curve. The approach is applied to a well-defined literature example to verify its validity and shed light on the characteristics of die fatigue life. The approach is also applied to practical forging and useful qualitative results are obtained.

The article presents the results of a complex analysis referring to the possibilities of applying different types of construction of forging dies used on a hydraulic hammer Lasco HO-U 160 in order to select the optimal solution in the aspect of obtaining the required dimension-shape accuracy. The analysis involved the use of the numerical simulation software FORGE 3.0 NxT. 12 different variants were analyzed, of both different tool constructions and detail arrangements on the die (in a quadruple and sixfold system). The effect of the forces as well as the way of material flow and degree of the forging tool seat’s filling were verified. The most ergonomic and technologically justified detail arrangement on the die was described. The results of the numerical simulation analyses were presented with the indication of the pros and cons of the particular solutions. The selected solution of the forging tool construction, implemented in a mass production, was especially discussed to verify of obtained FEM results and improvement actual technology.

Forging dies, which are crucial for manufacturing automobile tripod housings, are frequently replaced owing to their extensive use under challenging conditions, leading to the disposal of many components and increasing manufacturing costs. The development of repair and remanufacturing technologies for high-hardness forging dies is a challenging. This study explores the on-site repair of tripod forging dies using wire arc directed energy deposition (arc-DED), assesses the hardness and tensile properties of remanufactured components, and compares them with the specified forging die requirements for on-site usability. A validated novel slicer is employed in remanufacturing experiments on a 9.8 % Cr die steel tripod-forging die. Results show the effectiveness of arc-DED in remanufacturing, surpassing the specified requirements by at least 111 HV and 61 MPa in hardness and tensile strength, respectively. Thus, this study presents a promising approach to reduce the manufacturing costs and environmental impact associated with the forging-die-component disposal.

Hot forging dies are subjected to periodic thermal stress and often fail in the forms of thermal fatigue, wear, plastic deformation, and fracture. A gradient multi-material wire arc additive remanufacturing method for hot forging dies was proposed to extend the service life of hot forging dies and reduce total production costs. The properties of multi-material gradient interfaces play a critical role in determining the overall performance of the final products. In this study, the remanufacturing zone of a hot forging die was divided into three deposition layers: the transition layer, the intermediate layer, and the strengthening layer. Experiments of wire arc additive manufacturing with gradient material were conducted on a 5CrNiMo hot forging die steel. The microstructure, microhardness, bonding strength, and impact property of gradient interfaces were characterized and analyzed. The results revealed that the gradient additive layers and their interfaces were defect-free and that the gradient interfaces had obtained a high-strength metallurgical bonding. The microstructure of the gradient additive layers presented a gradient transformation process of bainite-to-martensite from the bottom to the top layer. The microhardness gradually increased from the substrate layer to the surface-strengthening layer, forming a three-level gradient in the range of 100 HV. The impact toughness values of the three interfaces were 46.15 J/cm2, 54.96 J/cm2, and 22.53 J/cm2, and the impact fracture morphology ranged from ductile fracture to quasi-cleavage fracture. The mechanical properties of the gradient interfaces showed a gradient increase in hardness and strength, and a gradient decrease in toughness. The practical application of hot forging die remanufactured by the proposed method had an increase of 37.5% in average lifespan, which provided scientific support for the engineering application of the gradient multi-material wire arc additive remanufacturing of hot forging dies.

This article presents research results regarding the development of a new manufacturing technology for an element assigned to belt conveyor flights in the extractive industry through hot die forging (of a forging with a double-sided flange) instead of the currently realized process of producing such an element by welding two flanges onto a sleeve or one flange onto a flange forging. The studies were conducted to design an innovative and low-waste technology, mainly with the use of numerical modelling and simulations, partially based on the current technology of producing a flange forging. Additionally, during the development of the forging process, the aspect of robotization was considered, both in respect of the forging tools and the process of transportation and relocation of forging between the impressions and the forging aggregates. A thermo-mechanical model of the process of producing a belt conveyor flight forging with deformable tools was elaborated by means of the Forge 3NxT program. The results of the conducted numerical modelling made it possible, among other things, to develop models of forging tools ensuring the proper manner of material flow and filling of the impressions, as well as temperature and plastic deformation distributions in the forging and also the detection of possible forging defects. For the technology elaborated this way, the tools were built together with a special instrument for flanging in the metal, and technological tests were performed under industrial conditions. The produced forgings were verified through a measurement of the geometry, by way of 3D scanning, as well as the hardness, which definitively confirmed the properness of the developed technology. The obtained technological test results made it possible to confirm that the elaborated construction, as well as the tool impressions, ensure the possibility of implementing the designed technology with the use of robotization and automatization of the forging process.

To improve the radial forging quality of hollow shaft, the entrance surface is constructed using a radial forging die with a cycloid as the generatrix, and the effects of structural parameters of the die forging surface, such as the radius of the cycloid base circle (R), the length of the sizing zone (L), and the radius of the sizing zone (r), are investigated. The orthogonal experimental design L25 results were numerically simulated, and an artificial neural network approach (ANN) was utilized to construct a mathematical prediction model and used to the genetic algorithm (GA) optimization process. The results show that the compromise solution’s optimal structural parameters are R=68.27 mm, L=49.36 mm, r=11.01 mm, εσ andCσ are 0.2113 and 0.02562, respectively. When compared to the original structural scheme, εσ is lowered by 21.83% and Cσ is reduced by 31.58%, indicating that plastic deformation is more uniform and material damage is reduced during the hollow shaft forging process.

This study focuses on optimizing the forming process of gas turbine blades using the hot forging method. Initially, the parameters that influence the strength, dimensional accuracy, and production cost of a Ti-6Al-4 V compressor blade for gas turbines are identified. These parameters are assessed through a two-level isothermal forging process and evaluated using the DFORM-3D software, a forging process simulator. After analyzing the preliminary findings, the parameters with the greatest impact on objectives are pinpointed and subjected to further testing within a narrower range. Once the optimal parameter range is determined, the blade forging dies are designed and fabricated based on the latest insights. Post-production, the blade undergoes relevant tests, and its performance is compared against the desired range. The alignment between real-world conditions and optimization results validates the initial assumptions. The study highlights the significant influence of forging temperature, pressing velocity, preform shape, and final die separation line on the optimization process, as evidenced by the results.