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Dobrany, Czech Republic

Dzugan J.,Comtes Fht | Misek T.,Doosan Skoda Power Co.
Advanced Materials Research | Year: 2012

Increasing demand for reliable design of all kinds of structures requires materials properties evaluated under the conditions as close to real service conditions as possible. Presently resolved project dealing with development of new turbine blades geometry requires better understanding of the material behavior under service conditions. Service conditions of turbine blades are cyclic loading at high temperatures under superheated steam conditions. There are not commercially available testing systems providing such functionality and the system allowing samples loading under considered conditions is to be proposed. The paper deals with development of the testing equipment and testing procedure for high cycle fatigue tests in superheated steam corrosive environment. The system allowing cyclic loading at temperatures up to 650°C under superheated steam conditions was successfully designed, assembled and tested on series of testing samples. © (2012) Trans Tech Publications, Switzerland. Source

Hodek J.,Comtes Fht
METAL 2014 - 23rd International Conference on Metallurgy and Materials, Conference Proceedings | Year: 2014

Induction heating is today wide used technology in industry in huge range of fields. Solution of this process contains both solution of the electromagnetic field and solution of the thermal field. In the past were knowledge and experiences obtained mainly from experiments but at the present time is possible to study induction heating phenomena using modern numerical method especially the finite element method [1]. The numerical solution helps to understand induction heating more complex and points out critical issues. Big advantage is use the numerical solution for induction heating coil design. This approach can avoid of long-lasting and expensive experiments with different variants. This paper deals with FEM simulations of induction heating. There are electromagnetic and thermal field taken into the account. The material properties are obtained on the base of material chemical composition. The numerical model considers thermal dependant material properties. Different coil design is considered and variants are compared. Source

Podany P.,Comtes Fht | Martinek P.,Comtes Fht
Materiali in Tehnologije | Year: 2014

The paper deals with the thermomechanical processing of low-carbon micro-alloyed steel processed by means of a physical simulation on a unique device for simulating a real forging process. The main goal of the experiment was to assess the mechanical and microstructural properties of steel after additions of various amounts of micro-alloying elements. Heats with additions of V, Nb, Ti and Zr were prepared. Different austenitization temperatures and different deformations were applied. Their influence on the microstructure and mechanical properties was evaluated. Source

Kubina T.,Comtes Fht | Gubis J.,Comtes Fht
Materiali in Tehnologije | Year: 2015

The objective of the present work was to trial the ARB method on commercially available steels with the mass fraction of carbon 0.011 %. Specimens were prepared with great care, mainly with respect to their surfaces and shapes, to successfully achieve, at an elevated temperature, a mass reduction 50 % in a single pass. The specimens were protected against scale formation at testing temperatures of 500-600 °C. Due to the complexity of the ARB method, only two bonding cycles were completed. The initial mean grain size was (18 ± 7) μm; after the first ARB cycle, the grains had a length of (24 ± 10) μm and a width of (8 ± 3) μm. The ultrafine-grained surface layer had a thickness of approximately 150-200 μm. After the second ARB cycle, the microstructure of this type was found in the centre of the specimens. After two passes the strength reached 660 MPa, but the elongation dropped to 3.3 %. The ultimate strength of the annealed feedstock was (290 ± 3) MPa and its elongation was A50 (49 ± 2) %. Experience shows that a continuous bonding of the material would be more effectively achieved with coiling machines, preventing the problems arising from the cracks in the welded joints on the faces of the specimens. Source

Dlouhy J.,Comtes Fht | Kover M.,Comtes Fht
IOP Conference Series: Materials Science and Engineering | Year: 2015

Tool steels undergo spheroidisation or soft annealing to enhance machinability and cold formability. Conventional soft annealing takes several hours. The final microstructure is composed of globular carbides in a ferritic matrix. We present an alternative process of carbide spheroidisation and steel softening. Accelerated carbide spheroidisation and refinement (ASR) was achieved by induction heating at temperatures close to the A1 temperature. The spheroidised structure was obtained in less than 5 minutes. The carbide particles that formed during the ASR were significantly finer than for the conventional soft annealing. The hardness after ASR was higher than the hardness after soft annealing because of the dispersion strengthening by finer and more densely distributed carbide particles. On the other hand, the fine structure is favourable for hardening. It enables smaller austenite grains and martensite laths to be obtained. Source

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