Wyniki wyszukiwania - BazTech

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Wpływ starzenia na mikrostrukturę i właściwości stali HR3C

Klimaszewska K., Golański G., Urbańczyk P.

Energetyka

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2018

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nr 11

622--624

PL

Badaniom metaloznawczym poddano stal HR3C w stanie dostawy oraz po procesie starzenia w temperaturze 600°C i 700°C w czasie do 10 000 godzin. Zakres przeprowadzonych badań obejmował: badania strukturalne za pomocą skaningowej mikroskopii elektronowej oraz badania mechaniczne: pomiar twardości i próbę udarności. Stal HR3C w stanie dostawy dostarczana jest po przesycaniu. Charakteryzuje się mikrostrukturą austenityczną z bliźniakami wyżarzania oraz z licznymi wydzieleniami pierwotnymi. Struktura ta zapewnia uzyskanie wysokiej ciągliwości (praca łamania na poziomie 212 J) i względnie niskiej twardości 176 HV30. Obserwacje mikroskopowe stali HR3C po procesie starzenia ujawniły istotne zmiany mikrostruktury polegające głównie na tendencji do tworzenia niekorzystnej morfologii wydzieleń faz wtórnych na granicach ziaren, wewnątrz ziaren oraz na pojedynczych granicach bliźniaczych. Procesy te przyczyniły się do spadku ciągliwości badanej stali przy jednoczesnym wzroście twardości. Bardziej zaawansowane procesy wydzieleniowe obserwowano w stali starzonej w temperaturze 700°C.

EN

The physical metallurgical tests were performed on HR3C steel in the as-received state and after the process of ageing at the temperature of 600°C and 700°C, at times up to 10 000 hours. The range of the conducted tests included: structural tests using the scanning electron microscopy and mechanical tests: measurement of hardness and impact strength tests. The HR3C steel in the as-received condition was delivered after supersaturation and was characterised by the austenitic microstructure with annealing twins and numerous primary precipitates. Such a structure ensured obtaining high ductility (notch toughness at the level of 212 J) and relatively low hardness of 176 HV30. The microscopic observations of the HR3C steel after the ageing process revealed significant changes in the microstructure consisting mostly in the tendency to form unfavourable morphology of the secondary phases precipitates on the boundaries of grains, inside the grains, as well as on single twin boundaries. These processes contributed to a decrease in ductility of the examined steel, at the concurrent growth of hardness. The more advanced precipitation processes were observed in the steel aged at the temperature of 700°C.

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Mikrostruktura i ciągliwość stali HR3C po starzeniu w 650°C

Hernas A., Bednarczyk I., Mościcki A., Fudali S., Hajdas J.

Energetyka

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2016

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nr 11

664--666

PL

Podano wyniki badań austenitycznej stali HR3C rekomendowanej do stosowania na wężownice przegrzewaczy pary kotłów na parametry nadkrytyczne pracujące w temperaturze około 650°C. Materiałem do badań był materiał rodzimy oraz złącza spawane wykonane w RAFAKO SA poddane cyklicznej obróbce cieplnej w temperaturze 650°C. Zakres badań obejmował głównie obróbkę cieplną, pomiary pracy łamania, ocenę mikro- i substruktury oraz morfologii przełomów próbek udarnościowych. Wyniki badań ujawniły znaczny spadek pracy łamania i kruchość stali po zastosowanej obróbce cieplnej spowodowane intensywnym procesem wydzieleniowym węglików M23C6 głównie po granicach ziaren i bliźniaków austenitu.

EN

The HR3C steel is recommended for long-term service under creep conditions at up to 650-660°C. The paper presents some results of microstructure analysis and fracture morphology and toughness of welded joints made of HR3C steel after cyclic heat treatment at 650°C. Results confirmed the unsatisfactory ductile properties below KV<40 J with brittle nature of cracking as a result of mainly a tendency towards the formation of unfavorable morphology of M23C6 carbides at the coarse-grain and twin boundaries of austenite.

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Microstructure and mechanical properties of HR3C austenitic steel after service

Golański G., Kolan C., Zieliński A., Klimaszewska K., Merda A., Sroka M., Kłosowicz J.

Archives of Materials Science and Engineering

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2016

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Vol. 81, nr 2

62--67

EN

Purpose: The purpose of the investigations was to determine changes in the microstructure and mechanical properties of HR3C creep resisting austenitic steel after service. Design/methodology/approach: The investigations were performed on test specimens taken from a part of the steam superheater tube. The range of the investigations included: microstructural investigations - light and SEM microscope; analysis of precipitates - carbide isolates; investigations of mechanical properties - hardness measurement, static tensile test, impact test. Findings: The precipitation processes at the grain boundaries lead to increase in intergranular corrosion of the HR3C steel resulting in loss of grains in the structure. The impact strength testing on test specimens with reduced width may result in overestimation of crack resistance of the material after service. Research limitations/implications: The comprehensive analysis of precipitation processes requires TEM examinations. Finding the correlation between the impact strength determined on standard vs. non-standard test specimens with reduced width. Practical implications: The obtained results of investigations are used in industrial practice for diagnosis of pressure parts of power boilers. Test procedures developed based on comprehensive materials testing conducted under laboratory conditions are used in upgrading and design of pressure parts of steam boilers. The results of investigations are also the element of database of the materials characteristics of steels and alloys as well as welded joints made of them working under creep conditions developed by the Institute for Ferrous Metallurgy. Originality/value: The results and analysis of the investigations of microstructure and mechanical properties of HR3C steel after service under actual boiler conditions are presented.

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Austenitic steels or boiler elements in USC power plantsAustenitic steels or boiler elements in USC power plants

Zieliński A.

Journal of Achievements in Materials and Manufacturing Engineering

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2013

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Vol. 57, nr 2

68--75

EN

Purpose: Characteristics of functional properties of austenitic- based steels used for construction of boilers with supercritical and ultra-supercritical steam parameters. Design/methodology/approach: For selected austenitic steels in as-received state and after long-term annealing microstructural investigations were carried out with scanning and transmission electron microscope. Findings: Selected characteristics of structure and functional properties of materials to be used for critical elements in the pressure selection of power boilers were summarized in a single paper. Practical implications: The steel characteristics presented in this paper are used for assessment of structural changes and changes in strength properties of material o elements after long-term service under creep conditions. Originality/value: The presented results of the mechanical properties, structure and in the precipitation processes are applied to evaluation the condition of the elements in further industrial service.