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Material-technological modelling is based on thermo-mechanical treatment of a small amount of real material using a thermomechanical simulator. This is a procedure allowing quick and accurate changes to selected parameters of the thermomechanical treatment. Due to the high dynamics of the process, material-technological models and forming technologies with high strain rates and with steep gradients in temperature changes can be designed using this method. The current state of technology also allows the use of this method for die forging. The paper is focused on the issues of material-technological modelling of die forgings made from C45 and the possibility of its application to designing changes and optimization of forming and heat treatment technology. The first phase of the solution is the creation of a material-technological model for a real forging. The objective of this phase was to achieve the desired agreement between the model and the real forging. In the second phase, this model was used to replace the conventionally processed material C45 by thermomechanical micro-alloyed steel 30MnVS6. The aim of the controlled cooling from the forging temperature was to achieve structures without heat treatment, which is currently a necessary part of the manufacturing process. Replacing conventional technology with controlled cooling results in a significant saving of production costs.

The article describes the effect of input material structure on the structure development during the subsequent processing by mini-thixoforming technology. Two different initial states were prepared from X210Cr12 tool steel for the experiment. The first semi-product was used in the soft-annealed state with ferritic-carbidic microstructure and coarse primary chromium carbides. Ferritic grain size 13,7 μm and the hardness was 210 HV30. The second state was prepared by high temperature annealing at 1200 °C for 1 hour. The microstructure then consisted of austenite and carbides. The grain size was in the range of cca 37 to 50 μm, hardness was 300 HV30. Treatment consisted of heating to a semi-solid state at the temperature 1265 °C in 9 s. That was followed by direct cooling to room temperature in 2 s. The grain size and distribution of eutectic in the volume of the processed material were selected as the attributes for microstructure evaluation after mini-thixoforming. The structure after processing in a semi-solid state consists of polyhedral austenite with a grain size of 43-59 μm, compared to the initial range 37-50 μm. This compares to the soft annealed state when, after semi-solid processing, the grain size was only 10 to 13 microns.

A fast, cost effective and simple methodology and testing apparatus was developed for testing basic material properties of thin (up to 0.05 mm) metal sheets during production. The method is based on the bulge test method. Air is used as a pressurizing medium and specimen deformations are measured using a 2D laser scanner. Test control and software for evaluating results was programmed in MATLAB using the GUI feature. The testing procedure and test assembly were developed with the accent on simplicity and obtaining fast results, which are both necessary for fast product testing during the manufacturing process.

In connection with increasing needs of different branches of industry for steels with excellent mechanical properties, like high strength combined with high ductility on one hand and low or at least moderate costs on the other hand, an experimental low alloy 42SiCr steel has been developed. If a conventional heat treatment is applied to this material, a very high strength can be reached, however with an unacceptable low ductility. Well balanced properties, i.e. strength about 2000 MPa and ductility more than 10 – 15%, can be achieved by an application of advanced heat treatment methods like Q-P (quenching and partitioning) process, consisting in quenching at intervals between martensite start and martensite finish temperatures resulting in stabilization of untransformed austenite by partitioning carbon. In service, numerous engineering components are exposed to variable, fatigue loading, whereas resistance to fatigue is usually particularly affected by different heat treatment methods or parameters and fatigue damage mechanisms have strong connections to material type, strength and microstructure. The aim of this study was to investigate fatigue properties of the 42SiCr steel treated using the Q-P process. Results of fatigue experiments are presented with respect to the basic material state and after traditional heat treatment – quenching and tempering. Fatigue damage initiation mechanisms, analysed particularly from fracture surfaces, and connections between fatigue properties and microstructure are discussed.

Testing device and testing method for determination of material properties of very thin metal foils (up to 0.05 mm of thickness) using modified bulge test method were introduces in previous works. The paper describes recent development of both the device and the methodology which further improve given concept. The design of the whole device was all remade, pressure measurement was significantly improved, new control and evaluation software was introduced. The method for laser measurement on glossy surfaces is presented. The method is an outcome of problems we faced during measurement using a laser system on glossy surfaces as it is almost impossible to obtain proper data on highly glossy surfaces for further post-processing. Our measurement outcomes are presented and discussed on specimens made of several different materials - Al, Cu, FeNi alloy. Finally we recognize specific limitations of the presented methodology.