Wyniki wyszukiwania - BazTech

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Nadmiarowe fazy w wysokoazotowych stalach austenitycznych

Kaputkina L., Svjażin A., Siwka J., Prokoszkina W.

Hutnik, Wiadomości Hutnicze

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2007

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Vol. 74, nr 7

357-363

PL

Badano zmiany zawartości azotu w austenicie po nagrzewaniu próbek do różnych temperatur i ich wygrzewaniu w różnych czasach. Ustalono, że w warunkach typowego nagrzewania w celu przesycenia bazowej stali Crl8Nil0Ti w jej strukturze występują nie rozpuszczone w roztworze starym azotki, których ilość zwiększa się ze wzrostem zawartości azotu w stali. Jest możliwe prawie całkowite rozpuszczenie się azotków przez nagrzanie metalu do temperatury 1200 °C i wygrzewanie go przez czas dłuższy niż 30 min. Zawartość azotu w austenitycznych stalach wysokoazotowych powinna być zbilansowana z zawartością innych pierwiastków stopowych w zależności od pożądanej struktury: austenit lub austenit i fazy nadmiarowe.

EN

Variations in the nitrogen content of austenite after heating the specimens up to different temperatures and then soaking them for different periods of time were investigated. It has been found that, under the conditions of typical heating to supersaturate the base Cr18Ni10Ti steel, nitrides undissolved in the solid solution occur in its structure, the amount of which increases with increasing nitrogen content of steel. Almost complete dissolution of nitrides is possible by heating the metal up to a temperature of 1200 °C and then soaking it for a period of time not longer than 30 min. The nitrogen content of high-nitrogen austenitic steels should be balanced with the contents of other alloy-forming elements, depending on the desired structure: austenite or austenite and excess phases.

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Ferrous alloys cast under high pressure gas atmosphere

Pirowski Z., Olszyński J., Gwiżdż A.

Archives of Foundry Engineering

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2007

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Vol. 7, iss. 1

107-112

EN

The main objective of this paper is describing the essence of the process of introducing nitrogen to the melt of ferrous alloys by application of overpressure above the metal bath. The problem was discussed in terms of both theory (the thermodynamic aspects of the process) and practice (the technical and technological aspects, safety of the furnace stand operation, and technique of conducting the melt). The novel technique of melting under high pressure of the gas atmosphere (up to 5 MPa) has not been used so far in the domestic industry, mainly because of the lack of proper equipment satisfyng the requirements of safe operation. Owing to cooperation undertaken with a partner from Bulgaria, a more detailed investigation of this technology has become possible and melting of selected ferrous alloys was conducted under the gas atmosphere at a pressure of about 3,5 MPa.

3

Wady wykrywane w kołpakach generatorów ze stali wysokoazotowych

Jasiński J., Niewielski G.

Energetyka

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2003

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nr 6

401-406

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Crystallization, the cast structure and the formation of gas blowholes in high-nitrogen steels and alloy steels.

Svyazhin A.G., Siwka J., Skuza Z., Prokoshkina V.G., Kaputkina L.M.

Inżynieria Materiałowa

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2001

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R. XXII, nr 5

884-887

EN

In the paper, the results of experimental research concerning the precipitation of nitrogen in the form of gas blowholes during the crystallization of supersaturated Fe-N, Fe-O-S-N alloys and 1Cr13 and Cr18Ni10 steels have been described. It has been found that the precipitation of nitrogen gas blowholes is more intensive and the pressure pN2 is higher at low contents of surface active elements, i.e. oxygen and sulphur. At the concentration ([%O] + 0.5%[%S]) > or = 300 ppm, microingots exhibited a compact macrostructure without gas blowholes. The results of a kinetic analysis of the process of desorption of nitrogen and the thermodynamics of the investigated solution (including surface tension) confirm that the surface reaction plays a decisive role in the formation of gas blowholes. For this reason, it is possible to eliminate the formation of gas blowholes in ingots of ferritic and ferritic-austenitic steels by introducing such SAE admixtures, as Sb, Te or Se. Analytical expressions have been obtained, which define the amount of nitrogen releasing into gas blowholes and describe the conditions for producing ingots or casting of a compact structure at cooling rates of approximately 10 to the 3 K/s.