Additive technologies are now widely used for the production of complex precise parts and have high potential for the production of forming dies. In this work, hot-forming dies optimized for additive manufacturing were developed and produced with wire arc direct energy deposition (WA-DED) and laser powder bed fusion (L-PBF) technologies. The concept of lightweight hot-forming dies with a 2D-lattice structure was developed, which reduced the weight of each die by 56%, from 14.2 kg to 6.1 kg, in production using L-PBF. Maraging/precipitation-hardened steel 17-4PH was used as an alternative to traditional hot-working steels with slightly lower mechanical properties and a much higher processability in the additive manufacturing process. The workability of the manufactured dies was confirmed by forging tests on an industrial screw press.

Aktuelle Trends in der Umformtechnik zeigen einen zunehmenden Automatisierungsgrad und eine steigende Anforderung an die Genauigkeit der Schmiedestücke. Während des Umformprozesses treten hohe Kräfte auf, die zu einer deutlichen Verformung der Umformmaschine führen. Dies wird in der Regel bei der Prozessauslegung nicht berücksichtigt. Dieser Beitrag widmet sich der Untersuchung des Einflusses der elastischen Verformung der energiegebundenen Umformmaschine auf Prozessparameter und Defektbildung beim Warmschmieden. Recent trends in metalforming show an increasing degree of automation and demand for accurate forgings. High forces occuring during the forming process lead to a significant deflection of the forming machine, which is usually not considered in process development. The paper examines how elastic deformation of the energy-bound forming machine affects process parameters and defect formation during hot forging.

At present, finite element simulation and inverse analysis are widely used for the design and analysis of metal forming processes, allowing the identification of possible defects at the pre-production stage and realizing the “First Part - Good Part” strategy. However, the forging process is generally considered in FEM simulations as a deterministic process without taking into account variations in material properties and process parameters, which leads to reduced forgings quality and process reliability. Considering uncertainties and stochastic effects is one of the major challenges in FEM simulations. Inverse analysis can be used to identify, characterize and integrate the uncertainties and stochastic effects into forging process analysis. Several works have attempted to include stochastic effects into sheet metal forming simulation as well as simulation of hot forging of turbine blades. However, issues of automating and utilizing inverse analysis in this field remain open and require further development. This paper develops an approach for analyzing uncertainties and stochastic effects based on automated API-driven finite element simulations. A control code that automatically varies the dimensions, position and orientation of the workpiece as well as process parameters, starts the simulation and performs automatic evaluation of the simulation results has been developed. Based on the obtained dataset, a parameter sensitivity analysis was performed and the relative importance of each parameter on the formation of defects such as folding or underfilling was determined. The developed approach is further verified through experimental trials on an industrial screw press equipped with a data acquisition system.

The model of dynamic recrystallization of Ti-6Al-3.5Mo-1.5Zr-0.3Sihas been developed based on experimental data and implemented in QForm FEM code. Kinetics of dynamic recrystallization was simulated by Johnson-Mehl-Avrami-Kolmogorov equation. Effect of aging time (1-6 h) and temperature (450-650 °C) on mechanical properties has been experimentally studied. The model of heat treatment of Ti-6Al-3.5Mo-1.5Zr-0.3Si has been developed and implemented in QForm FEM code. The model is capable to predict phase compositionand hardness during and after arbitrary heat treatment within studied range.It was found that the highest hardness of Ti-6Al-3.5Mo-1.5Zr-0.3Si can be obtained by aging during 4-6 hours at 550 °C after solution treatment at 960 °C.

Press hardening is extensively used in the automotive, agricultural and other branches of industry to efficiently produce high-strength parts by integrating a heat treatment into the hot forming process. One of the major challenges in press hardening is the die wear due to high cyclic thermomechanical loading. The wear leads to die geometry changes and thus to unacceptable tolerances of components and deviations from intended mechanical properties due to the lower cooling rates in these areas. The most promising approach for extending the die lifetime is the application of additive technologies for their repair. Some examples of die repair using L-DED and WA-DED additive technologies are presented in the literature, but no guidelines were provided. This paper proposes a methodology for the additive repair of an arbitrarily shaped die surface using generic segments. The main approach is to decompose the die geometry into elementary geometric segment shapes and to develop an optimal repair strategy for each segment shape. The targeted deposition strategy proposed in the paper also helps to control the metal flow during hot stamping and increases the fatigue life of the repaired tool. The proposed approach has been validated on a specific die insert utilizing the L-DED process.

Additive manufacturing (AM) technologies are widely used for the production of individual complex precise parts and small-scale production. AM has been used in many applications for the manufacturing of sheet metal forming dies. The production of hot bulk forming dies by additive manufacturing technology has not been extensively studied in the literature. Traditional hot working steels exhibit many problems during the AM process, such as crack formation due to complex thermal processing cycles. Maraging/precipitation-hardened (PH) steels may be a good alternative because of their ability to undergo additive manufacturing. One of the main causes of hot forming die failures is thermomechanical fatigue. The fatigue performance of 17-4PH was investigated primarily during high-cycle fatigue (HCF) and low-cycle fatigue (LCF) modes without heat treatment as well as with H1100 heat treatment. The LCF of dies with the heat treatment designation H900, which is most appropriate for die production, has not been intensively investigated. In this work, the mechanical properties and fatigue life of 17-4PH precipitation-hardened steel produced by laser powder bed fusion (L-PBF) and wire arc direct energy deposition (WA-DED) additive technologies were experimentally investigated, and numerical models for high-temperature low cycle fatigue life were developed for 17-4PH steel. Based on the FEM simulation in the commercial program QForm UK, the fatigue life of the produced dies was predicted.