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1

The evaluation of suitability for operation of repair low-alloy steel welded joints

Dziuba-Kałuża M., Zieliński A., Jasiński A., Sroka M., Dobrzański J., Linek T.

Archives of Materials Science and Engineering

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2016

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Vol. 78, nr 2

78--86

EN

Purpose: The purpose of the work was to evaluate the material condition of repair welded joints of steam pipelines with regard to their suitability for operation including determination of the time of their further safe operation. Design/methodology/approach: The following was carried out: microstructure investigations using scanning electron microscopy, investigations on mechanical properties at room and elevated temperatures, determination of the fracture appearance transition temperature based on impact tests. The abridged creep tests without measurement of elongation during test were carried out to determine the material’s residual life. Findings: The time of safe operation was determined for welded joints made in 14MoV63 steel after long-term service and 14MoV63 steel after long-term service and in the as-received condition. Practical implications: The applied methodology and the adopted procedures are used in evaluating the condition and forecasting further operation of new repair welded joints for the pressure part components of power equipment working under creep conditions. Originality/value: The obtained results of investigations will be the elements of materials characteristics worked out by the Institute for Ferrous Metallurgy for the steels and welded joints made in them to work under creep conditions.

2

Trwałość eksploatacyjna materiału elementów pracujących w warunkach pełzania w energetycznych urządzeniach wysokociśnieniowych

Dobrzański J., Zieliński A., Purzyńska H., Dziuba-Kałuża M., Matusik M.

Prace Instytutu Metalurgii Żelaza

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2015

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T. 67, nr 2

158--167

PL

Przedstawiono dobór rodzaju badań w zależności od czasu eksploatacji i rodzaju elementu dla oceny stanu materiału i prognozy trwałości eksploatacyjnej w energetycznych urządzeniach wysokociśnieniowych. Określono względne udziały procesów powodujących zmiany w strukturze materiału podczas pełzania w zależności od stopnia wyczerpania. Dokonano klasyfikacji zmian w strukturze w zależności od dostępności materiału z uszkodzeniami i bez uszkodzeń wewnętrznych. Badano zmiany w strukturze stali pracujących w warunkach pełzania, w tym klasę rozpadu perlitu / bainitu i/lub martenzytu, rozwoju procesów wydzieleniowych i rozwoju wewnętrznych uszkodzeń w zależności od stopnia wyczerpania. Metodologię oceny stanu badanych stali po eksploatacji w warunkach pełzania na podstawie oceny zmian w strukturze procesów składowych tzn.: zmian w strukturze perlitu, bainitu lub martenzytu, zmian w zakresie rozwoju procesów wydzieleniowych oraz zmian w zakresie rozwoju uszkodzeń wewnętrznych odniesionych do stopnia wyczerpania przedstawiono na przykładzie stali niskostopowych i stali X20CrMoV12-1. Poziom wybranych właściwości mechanicznych, twardość, temperaturę przejścia w stan kruchy w zależności od klasy struktury i odpowiadającego jej stopnia wyczerpania przedstawiono na przykładzie stali 14MoV6-3 i X20CrMoV12 -1 po długotrwałej eksploatacji w warunkach pełzania. Sporządzono wykresy resztkowej wytrzymałości na pełzanie w postaci zależności σb = f(LM) w zależności od klasy struktury i stanu rozwoju procesów wydzieleniowych węglików na przykładzie stali 13CrMo4-5. Wyznaczoną trwałość resztkową w zależności od czasu do zerwania w próbie pełzania od temperatury badania przy stałym poziomie naprężenia odpowiadającym eksploatacyjnemu przedstawiono w postaci zależności tr =f(T) dla σ = const na przykładzie stali X20CrMoV12-1. Zależność prędkości pełzania od naprężenia σ dla temperatury dalszej eksploatacji w zależności od klasy struktury i stanu rozwoju procesów wydzieleniowych węglików przedstawiono na przykładzie stali 13CrMo4 -5. Rodzaj i udział występujących węglików w zależności od klasy struktury i stopnia wyczerpania przestawiono na przykładzie stali 13CrMo4-5. Ocenę stanu materiału na podstawie badań mikrostruktury z zastosowaniem metody replik matrycowych przedstawiono na przykładzie materiału odcinka rurociągu pary świeżej ze stali 14MoV6-3 po 216 000 godzinach eksploatacji w warunkach pełzania.

EN

Selection of the type of investigations depending on service duration and type of element for the evaluation of material condition and forecasting the life time in high-pressure power units was presented. Relative shares of processes causing changes in structure of material during creep depending on the exhaustion degree were determined. Changes in structure depending on availability of the material with and without internal damages were classified. Changes in structure of the examined steels working under creep conditions, including the pearlite/bainite and martensite decomposition class, development of precipitation processes and development of internal damages depending on the exhaustion degree, were examined. Methodology for the evaluation of condition of the tested steels after service under creep conditions based on the assessment of structure changes in constituent processes, the so-called: changes in pearlite, bainite or martensite structure, changes in development of precipitation processes and changes in development of internal damages related to the exhaustion extent, was presented on the example of low-alloy steels and X20CrMoV12-1 steel. The level of selected mechanical properties, hardness, brittle fracture appearance transition temperature depending on the structure class and corresponding exhaustion degree was presented on the example of 14MoV6-3 and X20CrMoV12-1 steels after long-term service under creep conditions. The disposable creep strength diagrams were made in the form of relationship σb = f(LM) depending on the structure class and state of development of the carbide precipitation processes on the example of 13CrMo4-5 steel. The residual life determined as a relationship between time to rupture in the creep test and test temperature at constant stress level corresponding to the operating one is presented in the form of relationship tr = f(T) for σ = const on the example of X20CrMoV12-1 steel. The relationship between creep rate and stress σ for temperature of further service depending on the structure class and state of development of carbide precipitation processes was presented on the example of 13CrMo4-5 steel. The type and share of the occurring carbides depending on the structure class and exhaustion degree was presented on the example of 13CrMo4-5 steel. The evaluation of material condition based on investigations of microstructure using the matrix replica method was presented on the example of the material of 14MoV6-3 steel primary steam pipeline section after 216 000 h service under creep conditions.

3

Assessment of loss in life time of the primary steam pipeline materiał after long-term service under creep conditions

Zieliński A., Dobrzański J., Jóźwik T.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 54, nr 1

67--74

EN

Design/methodology/approach: For material of the pipeline after long-term service the microstructure investigations in a scanning electron microscope, phase composition analysis of precipitations, hardness measurement at the point where structure was observed and mechanical testing at room temperature were carried out. In addition, the magnetic particle inspections and ultrasonic testing were carried out over the entire volume of the pipeline sample. Findings: The life exhaustion extent of the investigated steel 14MoV6-3 estimated based on the metallographic tests is much higher than the expected one for the investigated steel at the current working parameters of the pipeline. Correct evaluation of the pipeline material condition during the periodic diagnostic testing, including but not limited to that performed by the matrix replica method, allows the excessive loss in life time of the material to be revealed and the reason for premature destruction of the pipeline components to be diagnosed and removed early enough. Practical implications: The presented method can be used for evaluation and qualification of structural changes in power station boiler components operating under creep conditions. Originality/value: The presented results of changes in the mechanical properties, structure and in the precipitation processes are applied to evaluate the condition of the elements in further industrial service.

4

Matrix replica method and artificial neural networks as a component of condition assessment of materials for the power industry

Sroka M., Zieliński A.

Archives of Materials Science and Engineering

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2012

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Vol. 58, nr 2

130--136

EN

Purpose: use of matrix replica method and artificial neural networks in condition assessment of materials working under creep conditions. Demonstration of scanning electron microscopy usefulness for correct assessment of the occurrence of internal damages. Design/methodology/approach: For material after long-term service the microstructural investigations were carried out on metallographic specimens and matrix replicas using light and scanning electron microscope. A computer program was used for material condition assessment. Findings: The way of material condition assessment by matrix replica method using a computer program as an example of the application of computer materials science methods was presented. The correct development of methodology for assessment of the degree of internal damages in steel working under creep conditions was found a result of verification. Critical comments on condition assessment of structure observed using light microscopy were presented. Practical implications: The presented method can be used for evaluation and qualification of structural changes in power station boiler components operating in creep conditions. Originality/value: The presented results of changes in the mechanical properties, structure and in the precipitation processes are applied to evaluation the condition of the elements in further industrial service.