Papers by Author: Ladislav Kander

Abstract: The paper deals with research, development and verification of production technology of selected welded joints for pressure vessels located in primary circuit of nuclear power plants type MIR 1200. Effects of various welding technologies on mechanical and fracture properties were studied. Four types of weld joints made of 10GN2MFA steel grade were prepared for experimental programme consisted of testing of conventional mechanical (tensile and impact tests) as well as fracture toughness and low-cycle fatigue tests and also stress corrosion cracking test in water environment. Effect of elevated operating temperature on material properties was evaluated, too.

Abstract: The Paper Deals with Microstructural and Mechanical Properties Changes during Severe Plastic Deformation Process in Beta Titanium Alloy Used for Hip Implants. Effect of Various Numbers of Passes through ECAP (Equal Chanel Angular Pressing) Die on Microstructure and Properties Have been Evaluated. Comparison between Virgin State Cast Alloy and Alloy after Several Steps of Severe Plastic Deformation Induced by ECAP Technology Have been Carried out. Mechanical Properties Have been Evaluated Using Miniaturized Specimens. from Experimental Work can Be Concluded Positive Effect of ECAP Technology both on Mechanical Properties (yield Stress as well as Tensile Strength) Including Grain Size.

Abstract: The paper deals with research, development and verification of production technology of selected welded joints for pressure vessels of primary circuits of nuclear power plants of type MIR 1200. Effect of various welding technology including simulation heat treatment on mechanical and fracture properties have been studied. Four type of homogenous 10GN2MFA – 10GN2MFA type of welded joints have been prepared for experimental programme. Conventional mechanical properties (tensile and impact test) as well as unconventional mechanical properties (fracture mechanics, low-cycle fatigue and stress corrosion cracking in water environment) have been studied. Effect of elevated working temperature on structure and material properties has been evaluated. Temperature dependencies of shear fracture have been plotted and effect of welding procedure on transition temperature shift has been evaluated. Experimental data have been compared with numerical simulation using FEM.

Abstract: The paper deals with the change of the structure and mechanical properties of the austenitic steels after the exposure at the critical temperature. The effects of the bend radius of tubes including effect of solution annealing on the mechanical properties and the structure were studied. The mechanical properties were studied using small punch test (SPT) and miniaturized tensile tests. From the results can be concluded that the mechanical properties and the structure have been influenced due to one year exposure at the working temperature significantly. Various amounts of σ-phase were found in the pulled part of the bend side of the tubes even after only thermal exposure without any loading. The effect of the heat treatment and the bend radius on the mechanical properties and the structure was also evident. Drop in fracture energy due to the presence of the σ-phase in the structure was clearly detected from force - displacement record of the small punch test. Keywords: Austenitic steels, bends, σ-phase, small punch test

Abstract: This paper is focused on evaluation of the plastic deformation effect, after the cold bending process for new austenitic material Super 304H designed for supercritical conditions. The aim of the project was to qualify the process of cold bending and then verify the properties of these bends in conditions approaching application. This paper presents the results of the plastic deformation effect on changes in the structure and mechanical properties at operating temperatures in corrosive environments coal combustion products and comparison to results before degradation. The tests were carried out on bends in two dimensions of tubes which are the most common sizes used in super-heaters for supercritical power plant boiler. The bends were produced by the method of cold bending on several bending radii in order to obtain information about the structure and behaviour of materials at various stages of deformation. To obtain reliable information tensile test, hardness test and metallographic examination were used on material from straight tubes of the bends and drawn parts before degradation and after degradation.

Abstract: This article is focused on optimization of fundamental utility properties and technological process of advanced low alloy steel 15NiCuMoNb5 used for power engineering mainly for production of large capacity steam boilers. Consequently problem critical locality in weld after post weld heat treatment is studied. Optimization of welding technology is proposed. Fracture behaviour of welded joint made from boiler plates 80 mm in thickness of 15NiCuMoNb5 type steel after N + T PWHT regime after welding procedure were studied. Stable crack growth measurement and evaluation of fracture toughness of base material as well as weld metal in temperature region from 0 up 350°C were carried out. Unstable cleavage fracture and fracture toughness KJc of both parts of welded joint at test temperatures cover the transition region were evaluated. The reference temperature T0 approach was used for evaluation of temperature dependence of fracture toughness in transition range.

Abstract: The effect of intercritical annealing of 10GN2MFA grade steel on mechanical properties and impact notch toughness is studied in this paper. This type of low alloy banitic steel is used for production of collector bodies of steam generators for nuclear power station of VVER type. This article is focused on optimalization of fundamental utility properties and heat treatment process of the steel under investigation to increase toughness and critical temperature of brittleness. An intecritical annealing has been chosen as a useful tool for such improvement. Mechanical properties and impact notch toughness values after the intercritical annealing and conventional heat treatment regimes are compared. Effect of simulation of stress relieving including minimum and maximum allowable heating regimes are studied too. Intercritical annealing was added to the conventional quality heat treatment process, between quenching (normalizing) and tempering. The application of intercritical annealing improved the impact toughness significantly, an increase in the upper shelf energy and a decrease in transition temperature of steel under investigation.