Papers by Keyword: Forging

Abstract: This study examines the forging process of an aluminum upper control arm for automotive applications. To address the geometric complexity and forming challenges, a multi-step forging route, comprising of roll forging, two-stage bending, pre-forging, and final forging, is developed. Finite element analysis (FEA) using DEFORM-3D software is employed to optimize key forming process parameters in the pre‑forging stage. The response surface methodology (RSM), combined with the Box–Behnken design, is utilized to construct predictive models and identify optimal parameter combinations. A successful forged upper control arm is subsequently produced using these optimized forming parameters. The findings demonstrate that integrating FEA with statistical process optimization strengthens the predictive accuracy of the process design and supports defect‑free forging of AA6082 upper control arms.

Abstract: Predicting the microstructural state during manufacturing is critical, as it directly governs the material's final mechanical properties. Accurate prediction of microstructure evolution in multi-stage industrial hot deformation processes, such as rolling, is limited by the lack of experimental data at intermediate stages, where direct measurement is impractical. To address this, an integrated methodology combining finite element (FE) simulation in QForm UK® software, physical simulation using the Thermo-Mechanical Treatment Simulator (TMTS), and artificial intelligence (AI) is proposed and investigated. The methodology is demonstrated for the 11-pass hot rolling of a 41Cr4 steel bar. Thermomechanical loading histories from an FE model of the industrial process were used to design and simulate a targeted TMTS experiment, generating a synthetic dataset via an analytical JMAK model that combines multiple recrystallisation mechanisms. This data was used to train a recurrent neural network (RNN) with an augmented physics-informed Long Short-Term Memory (LSTM) cell to predict the totally recrystallised fraction (RX) solely from loading history data. The AI model achieved high accuracy when validated within the TMTS simulation domain, successfully capturing different recrystallisation regimes. Implementation within commercial FE software enabled direct prediction in the rolling process simulation, yielding promising predictive capability, particularly in regions with thermal histories similar to the training data, highlighting the critical importance of training data diversity. This work establishes a proof of concept for a novel calibration methodology, where targeted physical simulation bridges the gap between industrial process complexity and data-driven AI model development, offering a practical solution for modelling scenarios where traditional experimental calibration is infeasible.

Abstract: Open-die forging is an incremental bulk metal forming process for producing large, safety-relevant components such as turbine and generator shafts. Besides achieving the target geometry, the process improves mechanical properties through grain refinement and the elimination of casting-related defects. With the increasing use of high-alloy steels, precise process control is required to prevent surface and internal cracking caused by material damage. However, predictive models for damage evolution under the thermo-mechanical conditions of open-die forging remain limited, particularly with respect to high-temperature recrystallization and the incremental process character with inherent pause times. In this work, a recrystallization-sensitive damage model was developed and validated for open-die forging. The parameters of the Lemaitre damage formulation were determined for the cold work tool steel D2 (1.2379, X155CrVMo12-1) using hot tensile tests over the relevant forging temperature range. Dynamic recrystallization kinetics were characterized by hot compression tests and described using an Avrami-type JMAK formulation, while static recrystallization behavior was analyzed by stress relaxation experiments and also modeled with JMAK kinetics. These results enabled the quantification of recrystallized fractions as functions of strain, temperature, strain rate, and dwell time. To link microstructural evolution with damage development, tailored recrystallization states were generated in dilatometer experiments and examined metallographically with respect to void formation and healing. The extended model was implemented in a finite element framework and validated through open-die forging experiments on demonstrator geometries, showing its capability to predict damage initiation under industrially relevant conditions.

Abstract: The lubricant thickness in cold forging was estimated by machine learning of the in situ captured images of the die–workpiece contact interface. The images were in situ captured by a high-speed camera from the backside of the transparent glass die during forging of commercially pure aluminum workpiece. On the other hand, the images of the lubricated workpiece were individually captured as training images for random forest with classification. The classification accuracy of the lubricant thickness was confirmed to be approximately 75% (classification ability: 5–10 μm in lubricant thickness) in the training images with 22,500 px (50 px/mm). The in situ captured images of the die–workpiece contact interface during forging were classified by random forest using the training images. The estimated lubricant thickness of the in situ captured image almost agreed with the lubricant thickness estimated from the mean brightness value of the in situ captured image.

Abstract: Wire arc additive manufacturing (WAAM) has gained significant attention in recent years as a cost-effective and efficient method for fabricating complex geometries. This study investigates the effects of cold forging and annealing on mechanical properties of AISI 308LSi wall fabricated using an automatically controlled gas metal arc welding on a CNC machine. The multilayer WAAM wall manufactured at an optimized parameters was first machined to a fairly smooth surface. Thereafter, the wall samples were differently subjected to annealing at 930°C and cold forging processes to improve the mechanical properties. Microstructural characterization of the post-processed and as-deposited samples were performed using optical and scanning electron microscopy while the tensile and hardness properties were investigated using Instron universal testing machine and Vickers hardness tester respectively. Annealing process was found to improve the tensile properties while the cold forging improved hardness of the deposited WAAM wall. These findings offer valuable insights into optimizing post-processing techniques for WAAM parts, especially 308LSi stainless steel and contribute to the advancement of this technology for industrial applications.

Abstract: The piston connecting rod is an indispensable in the internal structure of the automobile. As one of the important components in the internal combustion engine system, the piston connecting rod needs to meet the requirements of high fatigue and impact load resistance. Forged piston connecting rod can obtain high strength and fatigue resistance. In this study, the parting line, draft angle, forging tolerance, die fillet radius, shrinkage and scrap are considered in the design of forging die. The process parameters and die dimensions of the forging process of aluminum alloy piston rod are simulated by finite element analysis. The aluminum alloy piston rod with high dimensional accuracy is then forged according to the finite element simulation results.

Abstract: The term San Mai is used for the manufacture of knife blades consisting of three layered steel composites. The middle layer, which forms the cutting edge, consists of hard steel and on the outside a soft stainless steel is forged. Mr. Benjamin Kamon, an Austrian blacksmith, provided the examined sample. Three different steels and a thin Ni layer are symmetrically connected (1.4301/1.3520/Ni/1.2519/Ni/1.3520/1.4301). The middle layer is a cold work steel (1.2519) and the Ni layer is to prevent diffusion processes. 1.3520 is a heat treatable steel for rolling bearings, followed by an austenitic stainless steel (1.4301). Metallography and SEM-EDX were used to study the microstructure, the interfaces between the different steels as well as diffusion zones. It can be stated that all layers are well connected and no defects are evident.

Abstract: Forging tools must be able to withstand very strong mechanical, thermal, tribological, and chemical stresses. The extent to which a tool can withstand these stresses depends on the material used and its pre-treatment as well as the heat and surface treatment, i.e. the load capacity. The ratio of stress to load capacity determines how high the tool life of a forging tool is. This paper deals with the variations in the tool life of forging tools using the example of a specific industrial stage sequence and production conditions. Due to a large number of influencing variables that have an effect on the tool during the entire tool life history, the focus of this work is placed on influencing variables of the forming process. Based on real production parameters of a forging company, which are recorded during a period for the investigation, the process data are analyzed about an influence on the tool life. The investigation focuses on four influencing variables, namely the subjective assessment of the end of the tool life, the interaction between the forming stages, production interruptions, and the cooling and lubrication of the forming tools. For the parameters that are not yet recorded during the trials, promising available measurement methods are identified and tested under laboratory conditions. One example of this is the recording of the actual spray quantities that are sprayed onto the tool surface before the forming process. The results of the investigations show that the tool life fluctuations can be reduced by about 16% and as a consequence, the average tool life can be increased by about 13%.

Abstract: Diffusion treatments offer possibilities to enhance the performance and the service lifetime of hot forging tools. In combination with coating after nitriding, the surface layer hardness can be further increased. Within the scope of this study, a surface layer hardness above 2,000 HV0.005 was determined for borided or DLC (diamond-like carbon) coated surface layers. An increased surface layer hardness improves the abrasive wear resistance of forging dies. Furthermore, the plastic deformation of thermally softened forging die areas can be reduced. Beside these desirable effects, the ductility of diffusion treated or coated near surface layers is reduced and thermomechanical cracks are promoted. Therefore, additional approaches were developed to improve the thermomechanical crack behaviour of forging dies. Patterned plasmanitriding by the use of coverages to prevent areas from nitrogen diffusion, new combination processes of plasmanitrocarburizing (PNC) followed by plasmanitriding (PN) and the innovative boriding were investigated on different abstraction levels. A system of several testing rigs was set up to enable the abstraction of the thermal shock conditions in different stages. The patterned nitriding, boriding and combination plasma process (PN + PNC) were evaluated in a series of industrial field tests to derive recommendations for suitable tool treatments.

Abstract: The carbon supersaturated SKD11 punch and core-die were prepared by the plasma carburizing at 673 K for 14.4 ks. The upsetting experiment was performed by using this punch to describe the plastic flow of pure titanium and β-titanium works in higher reduction of thickness than 50%. The measured load – stroke relationship was utilized to describe the frictional behavior on the contact interface of punch to work materials and their work hardening process. The contact interface of carbon supersaturated punch to work was analyzed to investigate the formation of isolated carbon tribofilms from punch material and to describe the in situ solid lubrication on the contact interface. The micro-hardness mapping technique was also utilized to investigate how to suppress the work-hardening behavior by this in-situ solid lubrication. Free near-net forging experiments were performed to shape the circular β-titanium alloy wires to triangular bars.