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Aš, Czech Republic
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Martinek P.,Comtes Fht | Miskova J.,Comtes Fht | Dlouhy J.,Comtes Fht | Podany P.,Comtes Fht | Balcar M.,ZDAS
METAL 2016 - 25th Anniversary International Conference on Metallurgy and Materials, Conference Proceedings | Year: 2016

This paper deals with the impact of solution annealing on the properties of X2CrNiMoN2253 duplex steel. Experimental specimens were 100×100×150 mm forged and air-cooled pieces, which were solution-annealed at several temperatures changed in 20 °C steps between 1020 and 1120 °C. Mechanical tests conducted on these processed specimens included tension tests and Charpy impact tests at room temperature and at -46 °C. The results were compared with the requirements stipulated in the EN 10088-3 standard and with the minimum requirements for X2CrNiMoN2253 forgings for coastal oil and gas extraction set out in technical delivery conditions. Microstructures of the specimens were explored using optical and electron microscopes and EBSD analysis. EBSD measurement showed significant ferrite texture in some specimens, whereas no signs of texture were detected in austenite in any of the samples. The causes of the ferrite texture were investigated and its impact on properties of the duplex steel was explored.


Balazova M.,Welding Research Institute | Brziak P.,Welding Research Institute | Balcar M.,ZDAS | Junker M.,Benteler Steel Tube GmbH | Domovec M.,Zeleziarne Podbrezova
METAL 2015 - 24th International Conference on Metallurgy and Materials, Conference Proceedings | Year: 2015

Subject of this article are the results of gradient tubes analysis (material of the shell: 347H, material of the body: 11CrMo9-10) based on Amec Foster Wheele specifications requirement. The aim of the analysis was the determination of mechanical and technological properties of gradient tubes in order to install the gradient tubes in a commercial boiler. The NDT, outer shell thickness measurement, chemical analysis, tensile testing at 20°C and at elevated temperatures, flattening test, leak tightness test and metallographic examination of longitudinal and cross sections were used to prove the quality of gradient tubes. For this contribution, the gradient tubes (38mm outer diameter, 5mm wall thickness which austenitic shell is ~ 0,8mm thick) made by BENTELER were used. The work was done within the project GRAMAT supported by EU Research Fund for Coal and steel (www.gramat.org). The projects main aim is to acquire knowledge necessary to develop new cost-effective manufacturing technology of boiler tubes made from semi products with through thickness gradient chemical composition, tailored to carry both creep loading (low alloyed body) and fireside corrosion (high alloyed shell). Gradient tubes for the project are manufacturing in production facilities in BENTELER - Germany and PODBREZOVA IRONWORKS - Slovak Republic from semi products manufactured by unique casting technique (ŽDAS - Czech Republic); and to be tested by Amec Foster Wheeler - Finland in selected biomass boiler.


Balcar M.,ZDAS | Martinek L.,ZDAS | Fila P.,ZDAS | Novak J.,ZDAS | And 4 more authors.
Materiali in Tehnologije | Year: 2012

The production of Super-Clean Steels for the rotor forgings of compressors and generators for gas-turbine units started at ZDAS with the use of secondary metallurgy processes, a ladle furnace and vacuum degassing. The development and optimization of Super-Clean Steel production technology enables effective molten metal manufacture, conforming to the requirements for chemical composition and micro-cleanness. According to the results of the current production, the effective production of rotor forgings requires new technological steps in ingot casting.


Skobir D.A.,Slovenian Institute of Metals And Technology | Godec M.,Slovenian Institute of Metals And Technology | Balcar M.,ZDAS | Jenko M.,Slovenian Institute of Metals And Technology
Materiali in Tehnologije | Year: 2010

In this work, hot-forged, high-strength, low-alloy (HSLA) steels based on the chemical composition 34CrNiMo6 were investigated in order to determine the type of precipitates forming and their effect on the mechanical properties. The individual steels were microalloyed with one of the following elements or a combination of elements: niobium, titanium or zirconium and vanadium. The compositional changes in the microstructure and the various kinds of precipitates observed in the microalloyed steels were examined using energy-dispersive spectroscopy (EDS). Optical and scanning electron microscopy studies revealed that the addition of microalloying elements did not change very much the main microstructural features due to the fact that all the microstructures consisted of tempered martensite and finely dispersed carbide precipitates along martensite laths. In all the microstructures relatively large precipitates of the microalloyed elements were observed. This could be a possible reason for observing no significant improvement in the mechanical properties.


Martinek P.,Comtes Fht | Polakova I.,Comtes Fht | Balcar M.,ZDAS | Sochor L.,ZDAS
AIST Steel Properties and Applications Conference Proceedings - Combined with MS and T'11, Materials Science and Technology 2011 | Year: 2011

This paper describes the production of heat-resistant 1.4922 steel and the challenges in open-die forging of this material. It presents a numerical simulation of forging an 8K-type ingot into a stepped bar. The numerical simulation should lead to finding optimum forming conditions, using tracking of points selected in the initial ingot to their final positions in the forging. The final product contains defects. By tracking paths of points associated with them throughout the forming process, it should be possible to identify their initial locations within the ingot. At the beginning of the simulation, the points were set along the axis of the top and bottom of the ingot and on the surface of the anticipated cone of sedimentation within the ingot. The simulation should lead to optimization of the forming process and to adapting the initial stock in such a way, as to either completely eliminate the defects or to ensure that they are forced outside the final product shape by the forging process.


Podany P.,Comtes Fht | Balcar M.,ZDAS
AIST Steel Properties and Applications Conference Proceedings - Combined with MS and T'11, Materials Science and Technology 2011 | Year: 2011

The article deals with production of the micro alloyed steel forged products for oil industry. Customer requires high toughness in lowered temperatures, guaranteed weldability and also relatively high yield strength. Applied heat of steel has 0.1 of carbon content and 1.5 percent of manganese. Conventional alloying with conventional heat treatment not always lead to consistency in mechanical properties. Application of usual heat treatment (quenching and subsequent tempering) ensures only close compliance of requirements in yield strength. It is also complicated to meet adequate toughness at -46°C by applying conventional heat treatment. New heats with combination of several microalloying elements (Ti, V, Nb, Zr) were prepared. Physical simulation of forging on real specimens was done on unique device with possibilities of temperature and deformation controlling. The main goal of this experiment was to assess mechanical and microstructural properties of steel after addition of various amounts of various microalloying elements.


Podany P.,Comtes Fht | Balcar M.,ZDAS
Materials Science and Technology Conference and Exhibition 2011, MS and T'11 | Year: 2011

The article deals with production of the micro alloyed steel forged products for oil industry. Customer requires high toughness in lowered temperatures, guaranteed weldability and also relatively high yield strength. Applied heat of steel has 0,1 of carbon content and 1,5 percent of manganese. Conventional alloying with conventional heat treatment not always lead to consistency in mechanical properties. Application of usual heat treatment (quenching and subsequent tempering) ensures only close compliance of requirements in yield strength. It is also complicated to meet adequate toughness at -46°C by applying conventional heat treatment. New heats with combination of several microalloying elements (Ti, V, Nb, Zr) were prepared. Physical simulation of forging on real specimens was done on unique device with possibilities of temperature and deformation controlling. The main goal of this experiment was to assess mechanical and microstructural properties of steel after addition of various amounts of various microalloying elements. Copyright © 2011 MS&T'11®.


Martinek P.,Comtes Fht | Polakova I.,Comtes Fht | Balcar M.,ZDAS | Sochor L.,ZDAS
Materials Science and Technology Conference and Exhibition 2011, MS and T'11 | Year: 2011

This paper describes the production of heat-resistant 1.4922 steel and the challenges in open-die forging of this material. It presents a numerical simulation of forging an 8K-type ingot into a stepped bar. The numerical simulation should lead to finding optimum forming conditions, using tracking of points selected in the initial ingot to their final positions in the forging. The final product contains defects. By tracking paths of points associated with them throughout the forming process, it should be possible to identify their initial locations within the ingot. At the beginning of the simulation, the points were set along the axis of the top and bottom of the ingot and on the surface of the anticipated cone of sedimentation within the ingot. The simulation should lead to optimization of the forming process and to adapting the initial stock in such a way, as to either completely eliminate the defects or to ensure that they are torced outside the final product shape by the forging process. Copyright © 2011 MS&T'11®.

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