Wyniki wyszukiwania - Biblioteka Nauki

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CARBIDES ANALYSIS OF THE HIGH STRENGTH AND LOW DENSITY Fe-Mn-Al-Si STEELS

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Matus K. , Borek W. , Sozańska-Jędrasik L. , Mazurkiewicz J.

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nr 1

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Carbides Analysis of the High Strength and Low Density Fe-Mn-Al-Si Steel

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Sozańska-Jędrasik L. , Mazurkiewicz J. , Borek W. , Matus K.

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tom Vol. 63, iss. 1

265--276

EN

The work presents the results of investigations into the structure and phase composition of newly developed high manganese steels of the X98MnAlSiNbTi24-11 and X105MnAlSi24-11 type. The average density of such steels is 6.67 g/cm3, which is 15% lower as compared to typical structural steels. An analysis of phase composition and structure allows to conclude that the investigated steels feature an austenitic γ-Fe(Mn,Al,C) structure with uniformly distributed and elongated α-Fe(Mn,Al) ferrite grains on the boundaries of austenite grains and carbides. Examinations by diffraction of back scattered electrons (EBSD) allow to conclude that high-angle boundaries dominate in such steels, having significant influence on mechanical properties. Three types of carbides with differentiated chemical composition and size were identified in steel X98MnAlSiNbTi24-11 with scanning and transmission electron microscopy. κ-(Fe,Mn)3AlC carbides, having a regular, face-centered cubic lattice (fcc), were identified in austenite. Transmission electron microscopy examinations have enabled to identify M7C3-type carbide in ferrite. Nb- and Ti-based complex carbides were identified in steel X98MnAlSiNbTi24-11, both, in ferrite and austenite. (NbTi)C2 carbide precipitates were confirmed in an X-ray qualitative phase analysis. The size of the above-mentioned carbides is within several to several dozens of μm. An X-ray qualitative phase analysis has confirmed the precipitates of M7C3 carbides in both steels.

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Influence of Isothermal Heating Time on the Disappearance of Strain Hardening in High-Manganese TRIPLEX Type Steels

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Sozańska-Jędrasik L. , Mazurkiewicz J. , Borek W.

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tom Vol. 63, iss. 4

2023--2030

EN

The paper presents the results of the effect of isothermal heating time on the disappearance of strain hardening (the softening degree) of the studied high-manganese TRIPLEX type steels at a temperature of 900 and 1000°C. In order to determine the kinetics of recrystallization of austenite plastically deformed for selected steels, hot compression tests with draft ε = 0.2 were made. The presented results reveal that the complete recrystallization of austenite needs long isothermal heating times. In industrial conditions, such long times are not used, therefore in the initial rolling passages, the time required for half recrystallization of austenite t0.5 is often used. The total disappearance of the strain hardening, completion of the recrystallization of austenite tested high-manganese X98 and X105 TRIPLEX type steels isothermal heating time requires far more than 200 s. The increase of the deformation temperature is a factor influencing the acceleration of the disappearance of strain hardening.

4

Influence of Isothermal Heating Time on the Disappearance of Strain Hardeningin High-Manganese TRIPLEX Type Steels

100%

Sozańska-Jędrasik L. , Mazurkiewicz J. , Borek W.

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5

Structure and mechanical properties of newly-developed high-strength TRIPLEX type steels

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Sozańska-Jędrasik L. , Mazurkiewicz J. , Borek W. , Dobrzański L. A.

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2018

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tom Vol. 39, nr 5

184--191

EN

The paper presents the results of mechanical properties research, fractographic investigations of fractures and microstructure of experimental high-strength high-manganese X98MnAlSiNbTi24–11 and X105MnAlSi24–11 TRIPLEX type steels. In order to determine the mechanical properties of the tested steels, microhardness tests and a static tensile test were performed, and yield stress, tensile strength and elongation of the tested steels were determined. The performed microstructure tests of the analysed steels using light microscopy allowed for the identification of austenitic-ferritic structure with the participation of carbides. It was found that the structure of both tested steels, which have undergone hot rolling followed by water cooling, consist of austenite grains with numerous annealing and deformation twins along with ferrite bands. The investigated steels are characterized by the mixed fractures of formed after a static tensile test after forging where there are areas of ductile fracture with small areas of transcrystalline and intergranular brittle fractures. The fractures after a static tensile test and after hot rolling and cooling in water have a dimple morphology characteristic of plastic fractures. The increase in hardness after thermomechanical treatment and after a static tensile test is caused by strain hardening affecting the achieved values of strength, yield point and hardness. The obtained research results allow to assess the impact of both the chemical composition and the applied thermomechanical treatment technology on the properties of newly developed steels.

PL

Celem pracy było określenie właściwości mechanicznych oraz plastycznych w powiązaniu z mikrostrukturą nowoopracowanych stali wysokomanganowych X98MnAlSiNbTi24–11 i X105MnAl- Si24–11 typu TRIPLEX po walcowaniu na gorąco w skali półprzemysłowej i chłodzeniu w wodzie. Uzyskane wyniki badań pozwolą na ocenę wpływu zarówno składu chemicznego, jak i zastosowanej technologii obróbki cieplno-mechanicznej na właściwości badanych stali.