Wyniki wyszukiwania - BazTech

1

Zkoušení a hodnocení trubek z oceli 1.4541 (CrNiTi 18-10) se svarovými spoji proti mezikrystalové korozi

Lasek S., Schwarz D., Číhal V., Blahetová M., Kaděra B.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2009

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z. 95

25-26

2

Problematika materiálového řešení a protikorozní ochrany technologických zařízení v energetice

Číhal V., Krhutová Z., Míka J., Lasek S., Blahetová M.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2009

|

z. 95

7-8

3

Atestace odolnosti korozivzdorných austenitických ocelí proti mezikrystalové korozi

Lasek S., Číhal V., Blahetová M., Krhutová Z.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2009

|

z. 95

9-10

4

Hodnocení odolnosti supermartenzitických ocelí proti lokální korozi

Lasek S., Střílková L., Číhal V., Blahetová M.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2008

|

z. 92

47-48

5

The Metals science society during the 1990-2001 period

Číhal V., Macek K., Sedláček V., Vŕeštál J., Šíma V.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2006

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z. 88

107-112

6

Metals Science Society

Sedláček V., Číhal V., Šíma V.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2006

|

z. 88

103-106

7

Electrochemical corrosion studies of steels after plasma nitridation and oxidation

Oppelt J., Karjalajnen P., Blahetová M., Číhal V.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2006

|

z. 88

87-92

8

The EPR-test to characterize the senzitization behaviour of 02Cr21Ni33TiAl

Mikel P., Číhal V.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2005

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z. 86

165-168

EN

The Electrochemical potenciokinetic reactivation EPR (EPR) is nondestructive. No special sample preparation is required. It can be adapted to control various components during start-off or those already in service, especially the welded joints and surfaced components. The method is faster, more sensitive and more objective than the standard method, it can reliably determine the susceptibility to intergranular corrosion in heat-affected material and, as an added benefit, provide information on the overall corrosion resistance, and/or signal the danger of a selective, attack.. Criteria to assess the degree of susceptibility to intergranular corrosion using this method have not been unambiguously defined, and depend on the level of instrumentation. Measuring, of the current density peaks. - the critical passivating Jp and the reactivating Jr - and the values of the respective charges - the passivating Qp and the reactivating Qr. - is recommendable in addition to graphical plotting and observations of polarization curves at both the rising and decreasing potential. The influences of chemical analysis and sensitising are presented in terms of percent values expressing the reactivating/passivating charge ratio, or the so-called normalized reactivating charge. This method was used to measurement susceptibility to intergranular attack of the steel 02Cr21Ni33TiAl, probes from industrial oven working at 450 °C (probe A) to 650 °C (probe B) for 30.000 h. Referring to the Qr/Qp ratio, probe A exposed to a lower temperature, is highly sensitive, but probe B, exposed to higher temperature., is only slightly sensitive or insensitive, considering the fact that it is probably very heterogeneous due to considerable quantities of chromium carbides precipitated at the grain boundaries. Depletion in chromium at the grain boundaries at low temperatures, and equalisation of chromium content at the boundaries in the vicinity of carbides at higher temperature, were documented by the EPR test; these phenomena are also used to explain why probe A exhibited intergranular stress corrosion cracks.

9

Stress Corrosion Cracking Evaluation of High Alloy Steel (X2CrNiMoN 22-5-3) by DET

Lasek S., Blahetová M., Číhal V.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2004

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z. 78

17-22

EN

Stress corrosion cracking (SCC) can cause a dangerous failure of structural parts under specific combination of material, environment and loading. For testing of the resistance to SCC at higher temperatures (100-300°C) in water environments were proposed several methods. The Drop Evaporation Test (DET) is useful for comparison and evaluation of resistance of stainless steels and related alloys to SCC in chlorides containing water environments [1,2]. This test is valid in the cases, when evaporation of water environments can increase the content of anions (Cl-) and there is also possibility to form a salt deposition as a crevice on material surface. The advantage of DET is possibility of testing at higher temperature in the range 100~500°C using a lower Cl- water content (0-100 ppm) in convenient gas around the specimen. During DET there is a good possibility to observe a sample surface, initiation and propagation of pitting and corrosion cracking [3]. The process of thermal and corrosion fatigue is superposed on SCC mainly in the stage of initiation and propagation of short cracks especially in case of a higher difference of temperature between drops and heated sample. The DET simulates also the influence of heat transfer from material into environment on localized corrosion under evaporating conditions. The aim of this contribution is the study of short corrosion cracks growth on duplex steel of type X2CrNiMoN 22-5-3 (1.4462) under DET conditions by travelling microscope method.

10

Korozní poškozování zařízení z konstrukčních ocelí

Hubáčková J., Váňová P., Číhal V., Krhutová Z., Člupek O.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2004

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z. 78

89-92

11

Elektrochemické vlastnosti aluminidů železa s obsahem Ce A Zr

Kraus M., Krhutová Z., Číhal V., Kratochvíl P.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2004

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z. 78

103-108

12

Corrosion Properties of High Alloyed Steels

Číhal V.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2004

|

z. 78

11-16

EN

These last years, beside the austenitic-feritic (duplex) stainless steels grades, some high alloyed austenitic stainless steels with molybdenum contents and/or modified with nitrogen, wolfram with silicon contents have been developed. The nitrogen addition in these grades has been increased to 0.55 % in order to obtain both high mechanical properties and high corrosion resistance.

13

Korozní napadení součástí zařízení pro těžbu a úpravu zemního plynu

Hubáčková J., Blahetová M., Číhal V., Lasek S., Betáková P.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2003

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z. 76

105-109

14

Hodnocení charakteru korozního praskání vysokolegovaných materiálů s využitím metody det

Blahetová M., Lasek S., Číhal V.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2003

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z. 76

29-34

15

Corrosion resistance of steel Cr20Ni20 with variable contents of phosphorus and silicon in nitric acid

Číhal V., Krhutová Z., Lasek S., Blahetová M., Hubáčková J.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2003

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z. 76

43-49

EN

Segregation of phosphorus and silicon at the grain boundaries in austenitic stainless steels is known to make these steels susceptible to intergranular corrosion in strongly oxidizing environments. This behavior is more pronounced in steels containing phosphorus and normal contents of silicon, other conditions being equal. Considering the interrelationship between the changes in the relative free energy of the grain boundaries and the susceptibility to intergranular corrosion of high-purity austenitic stainless steels in HNO3+Cr6+ [1,2], associated with silicon, it would be of interest to evaluate the effect of phosphorus on the grain boundary energy in the steels of interest, booth with and without silicon, and to correlate this effect with the corrosion resistance of grain boundaries. The undesirable effect of phosphorus in these steels on the resistance of their grain boundaries in 27 % solution of HNO3+40 g.l-1 Cr6+ [3], can be eliminated by adding silicon in quantities ł2 % Si. The present paper shows the findings obtained during the research into the effect of the accompanying elements and silicon on the corrosion and electrochemical behavior of steel Cr20Ni20 with variable contents of phosphorus when exposed to nitric acid.

16

Selection of stainless steels for the severe environments

Číhal V., Blahetová M., Lasek S., Krhutová Z.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2002

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z. 75

15-20

EN

These last years, beside the austenitic-feritic (duplex) stainless steels grades, some high alloyed austenitic stainless steels with molybdenum contents and/or modified with nitrogen, wolfram and silicon contents have been developed. The nitrogen addition in these grades has been increased to 0,55% in order to obtain both high mechanical properties and high corrosion resistance. The steels with a very high nitrogen addition have a better microstructure stability in weld metal that those of austenitic steel with a moderated nitrogen addition. But in the heat affected zone can be the sensibility to the precipitation of fine nitrides. In the presence of both nitrogen and molybdenum and/or wolfram, significant improvements in the resistance of stainless steels to general and localized corrosion have been reported [1].

17

Studium lokální koroze austenitické oceu typu 1.4571 metodou sret

Kubečka P., Číhal V.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2001

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z. 72

45-48

18

Degradation processes in ammonia synthesis conditions

Číhal V., Stránský K.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2001

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z. 72

67-72

EN

Nitriding by ammonia synthesis gas causes a modification of the carbides, a decarburization and sensitization to hydrogen corrosion within a relatively thin metal layer near to the inner surface of the converters. Subsequently a sensitization to hydrogen attack occurs due to the reaction of diffusing hydrogen with carbon released by the carbides and a decar-burization by carbon diffusion to the surface. High local internal stresses perpendicular to the surface caused by surface nitriding lead to small inter-granular separations parallel to the surface without any significant effect on the integrity of the pressure vessel. As the nitrided layer hinders further nitriding of the steel, this phenomen is without any long-term consequence. On the other hand, if sufficiently high load and/or residual stresses apply in the axial or tangential direction to the vessel wall, cracks have to be expected propagating slowly across the wall, as crack growth is controlled by diffusion of nitrogen and carbide transformation. Consequently, the Nelson diagram for NH3-containing synthesis gas should be applied with only great care. Efforts are necessary to quantify as well the critical stress level for crack initiation, as the propagation rate of such cracks is controlled by nitrogen diffusion and the complex carbide reactions finish by chemically induced hydrogen cracking - hydrogen corrosion.

19

Corrosion problems in flue gas desulfurisation systems

Číhal V., Krhutová Z., Lásek S., Blahetová M., Hubáčková J.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2001

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z. 72

17-20

20

Příspěvek k volbě materíalů pro pračky na odsíření spalin

Číhal V., Krhutová Z.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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1999

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z. 59

71-73