Seznam abstraktů 2026: SEKCE B - TVÁŘENÍ KOVŮ

The majority of highly stressed steel components are manufactured through hot forming due to the increase in strength and toughness resulting from the formed fine-grained microstructure. Additionally, the alloying element manganese promotes high strength and hardness. Sulfur is added in order to ensure an improved machinability in the post-machining steps. However, at high temperatures present during hot forming, manganese and sulfur tend to form non-metallic inclusions consisting of manganese sulphide (MnS). These inclusions act as mechanical weak points in the steel matrix and can lead to an early failure of components.
In order to accurately model the hot forming process and predict the final properties of the component, the behaviour of the steel matrix as well as the MnS-inclusions is required. In this paper, the focus lies in the characterisation of the flow behaviour of two commonly used steel alloys containing varying contents of manganese and sulfur, 1.7139 (16MnCrS5) and 1.1303 (38MnVS6). Cylindric upsetting tests are conducted at different strain rates as well as temperatures typical for hot forming to determine the resulting flow curves which are then modelled with the Hensel-Spittel approach. These are used for the numerical simulation of the experiments based on the finite element method for validation. For this, a mesh study is conducted first, and the resulting force-displacement curves are compared to the experimental data.

This study presents new experimental results showing how strongly the surface quality of steel plates influences their cooling rate during continuous production. The investigated phenomena are directly relevant to industrial water-based cooling technologies applied to steel plates on the Run Out Table, during accelerated cooling, and in interstand cooling sections of hot rolling mills. The work focuses on solid jet nozzles operating in a low pressure system, which are commonly used in industrial cooling lines. Three types of surfaces were tested: a slightly oxidized stainless-steel surface, and once oxidized and twice oxidized surfaces on standard low carbon steel. The stainless-steel surface remained homogeneous both after heating and after cooling, forming only a thin and continuous oxide layer. In contrast, the carbon-steel surfaces sometimes developed blister-like defects during heating. When these blisters peeled off during cooling, they left behind a very rough oxide layer that completely changed the cooling behavior of the material. Our results show that this rough and uneven oxide layer can significantly slow down or accelerate cooling, depending on how water flows and breaks on the surface. This behavior is particularly important for controlling cooling uniformity and reproducibility under real operating conditions of continuous rolling and cooling lines. The contribution demonstrates the importance of controlled experimental testing for understanding real cooling behavior in production conditions. These findings are relevant for manufacturers and research organizations seeking to improve product quality, optimize cooling strategies, and increase the efficiency of continuous steel processing lines.

Strengthening the railway network is a key measure in tackling carbon emissions, as it enables low-emission travel and reduces road traffic. Maintenance plays a crucial role in this, with aluminothermic welding being the method of choice for rail repairs.

In this study, a numerical model is developed to predict the temporal and spatial evolution of the temperature field, microstructural phases and hardness during aluminothermic rail welding. The evolution of the microstructure is described using the Kirkaldy equation, incorporating the latent heat released during phase transformations. The complete framework has been implemented in an in-house C++ code.
The developed model is first validated against a well-documented reference case concerning the thermal and microstructural evolution of C45 steel. The numerically predicted temperature profiles and phase transformation behaviour show reasonable agreement with published experimental and numerical data. However, the accuracy of the predicted microstructure is found to depend strongly on the cooling rate regime.

Following validation, the model is employed to simulate the thermal and microstructural evolution of two specimens (base metal and welded section) produced from a laboratory-controlled aluminothermic welded rail steel.
The model is fitted to TTT data which was obtained trough transformation of experimental CCT diagrams for each material, respectively.
The predicted hardness distributions are compared with experimental measurement from jominy end quench tests. A good agreement is observed for the base metal. In contrast, noticeable deviations are observed in the welded specimen, particularly in regions subjected to high cooling rates.

Zirconium alloys are widely used as structural materials for nuclear fuel cladding and reactor components due to their favourable mechanical properties, good corrosion resistance, and low thermal neutron absorption cross section. This work investigates newly designed ternary zirconium alloys based on the Zr-Nb and Zr-Sn systems, with additions of Cr and Fe as intermetallic phase-forming elements. Compared to conventional zirconium alloys, the studied compositions contain increased concentrations of alloying additions in order to enhance solid-solution strengthening and promote the stabilization of secondary phases.
In contrast to conventional zirconium alloy processing, which is typically based on cold or warm deformation, the present study employs hot rotary swaging and hot rolling at temperatures specifically selected with respect to the phase transformations of each alloy. The applied processing routes resulted in dual-phase microstructures consisting of either hcp α + bcc β or hcp α + intermetallic Zr₂Cr Laves phase. In both cases, a fine submicron grain size of the α phase was achieved.
The processed alloys exhibit high strength, with selected compositions reaching ultimate tensile strengths exceeding 1200 MPa while maintaining ductility above 10% elongation at failure. These results demonstrate that controlled thermomechanical processing enables zirconium alloys with a superior strength-ductility balance, making them promising candidates for advanced nuclear applications.

Finite Element Method (FEM) simulations are essential for predicting feasibility, outcomes, and defects in hot plastic deformation processes. For small batches or single-component production, the use of a reliable model becomes crucial to minimise the number of physical trials, material waste, as well as time and energy consumption. Achieving high simulation accuracy requires setting appropriate boundary conditions, such as material properties and specific process parameters.
In hydraulic press forging, one of the main challenges lies in defining an objective relationship for the downstroke speed, which significantly influences the mechanical response of the workpiece and the overall operation time. This study presents a methodology to identify the power limit curve of a hydraulic press, correlating the maximum downstroke speed with the applicable values of the press force in an industrial context. An extensive dataset from real forging operations performed on blanks of different geometries and materials was processed to construct the power limit curve. The proposed model was validated by comparing FEM simulation results with experimental industrial data, demonstrating high reliability. In addition, the study showed that this approach can be tailored to characterise the downstroke speed of the press for specific materials and operations, even if a larger amount of significant data is required. The model offers a robust framework for enhancing the predictive capability of FEM simulations for hot forging processes.

Shear cutting operations, such as blanking, are critical in forming technology but often oversimplified in FE simulations, reducing predictive accuracy for cut edge quality. This study evaluates three failure modelling approaches for a FE model of DC04: the modified porous Gurson model and the Johnson-Cook model with element deletion and mesh separation. Experimental validation of the cutting characteristics rollover, burnish, fracture and burr showed that the JC model with mesh separation produced the most accurate results, with up to 99.86 % certainty. Based on this validated model, a factorial parameter study identified punch radius and sheet thickness as the dominant factors influencing burr height, while die radius and clearance exhibited minor effects. Numerical investigations of alternative blanking processes demonstrated that fine-blanking, counter-blanking and notch-blanking produced burr-free cuts, while hollow-blanking and two-stage blanking showed a less strong influence. These results confirm the capability of validated FE simulations for process optimisation.

By using a flexible and adaptable part design and manufacturing process, a wide range of products and product families can be produced. In sheet metal forming, particularly in the automotive sector, a large number of profiles is required which are commonly used in vehicle frames. The industry's pursuit of sustainability requires parts to be lighter while maintaining their load-bearing capacity. This in turn creates the need for secondary form elements in sheet metal components, such as beads and variable cross sections, to produce load-optimised components. Components with different profile geometries and secondary form elements can be produced by roll forming or draw bending using flexible tools. This study focuses on flexible draw bending of 1.5528 sheet metal profiles with variable cross sections under continuous tempering during forming. The variable cross sections allow for load-optimised weight distribution, whilst a secondary form element in the form of a central bead may increase the overall stiffness of the component. A segmented tool with a translational degree of freedom is used in a conventional draw bending setup. The sheet metal is inductively heated before forming and rapidly cooled after the forming zone to obtain a martensitic microstructure for high strength. After modelling and validating the forming process using the Finite Element software Simufact Forming, the tool kinematics are analysed in order to identify geometric discrepancies and their causes.

Hot forging of geometrically challenging components such as joint crosses is highly sensitive to process parameter variations, leading to geometric deviations and increased scrap rates under industrial conditions. A reliable description of the forming process, taking varying process parameters into account, is therefore essential for improving process stability and enabling model-based quality assurance. This study presents a comprehensive numerical investigation of a hot forging process of joint crosses made of 1.7225 steel. A numerical model is developed using the finite element (FE) software Simufact.Forming, consisting of an inhomogeneous inductive heating, billet transfer and single-stage forging. The predicted temperature field distribution obtained from inductive heating is validated by experimental temperature measurements and subsequently transferred to a thermo-mechanically coupled FE simulation. A reduced 90° symmetry approach is employed to ensure computational efficiency while accurately capturing material flow, contact interactions and geometric feature formation under industrially relevant forging conditions. The numerical results are validated by comparing simulated force-displacement behaviour and final component geometry with experimental reference data. The validated model provides a robust foundation for future process optimisation and systematic sensitivity-based parameter identification.

Powder metallurgy offers a promising approach to produce components with complex near-net-shape geometry after forming and excellent microstructural properties. The process chain consists of powder pressing of a green body, sintering, and sinter forging. However, the stochastic nature of powder combined with process parameter variations introduces uncertainties from the first step that propagate through the process chain and can lead to discrepancies in finished products. As a first step towards tracking and quantifying such uncertainties, this study focuses on modelling powder pressing of two aluminium belt pulley gear geometries. The geometries can be pressed using the same tooling by varying press stroke and display features commonly found in industrial applications. Numerical simulations identify key factors governing density distribution and reveal significant differences between the two geometries. Assessment of different bilateral pressing strategies demonstrates trade-offs in achieving uniform density distributions. These findings provide the foundation for understanding how initial density variations propagate through subsequent process steps and establish the basis for process chain optimization.

A Mg-3Al-0.2Ce alloy was processed through three thermo-mechanical routes: Route 1 (symmetric rolling + annealing), Route 2 (asymmetric reverse rolling + annealing), and Route 3 (extrusion + asymmetric reverse rolling + annealing). The evolution of microstructure, texture, and mechanical response was systematically evaluated. SEM-EDS analysis confirmed the presence of Al-Ce-rich intermetallic phases, while BSE imaging revealed distinct differences in particle distribution across the three processing routes. Coarse and clustered particles were observed in Route 1, elongated alignment along the rolling direction was evident in Route 2, and a more refined, homogeneous dispersion of particles was achieved in Route 3.
TEM investigations demonstrated that these particles served as potential sites for particle-stimulated nucleation (PSN), with high dislocation densities in the rolled condition giving way to recrystallized structures after annealing. The particle refinement and redistribution in Route 3 enhanced PSN activity and promoted more uniform recrystallization, leading to a weakened basal texture. Texture analysis confirmed reduced basal pole intensity in Route 3 (5.2) compared with Route 1 (5.6) and Route 2 (5.8).
Tensile testing along RD, TD, and 45° orientations revealed pronounced in-plane anisotropy in Route 1, a moderate reduction in Route 2, and nearly isotropic behavior in Route 3. The latter condition exhibited a superior balance of yield strength, tensile strength, and ductility, highlighting the role of optimized particle distribution and PSN in controlling texture and mechanical anisotropy.
This study demonstrates that combining extrusion with asymmetric rolling and annealing is an effective strategy to refine particle distribution, weaken basal texture, and improve isotropy in Mg-Al-Ce alloys