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Effect of Nb and Ti micro-additives and thermo-mechanical treatment of high-manganese steels with aluminium and silicon on their microstructure and mechanical properties

Sozańska-Jędrasik L., Mazurkiewicz J., Borek W., Matus K., Chmiela B., Zubko M.

Archives of Metallurgy and Materials

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2019

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Vol. 64, iss. 1

133--142

EN

The results are based on two experimental high-manganese X98MnAlSiNbTi24-11 and X105MnAlSi24-11 steels subjected to thermo-mechanical treatment by hot-rolling on a semi-industrial processing line. The paper presents the results of diffraction and structural studies using scanning and transmission electron microscopy showing the role of Nb and Ti micro-additives in shaping high strength properties of high-manganese austenitic-ferritic steels with complex carbides. The performed investigations of two experimental steels allow to explain how the change cooling conditions after thermo-mechanical treatment of the analysed steels affects the change of their microstructure and mechanical properties. The obtained results allow assessing the impact of both the chemical composition and the applied thermo-mechanical treatment technology on the structural effects of strengthening of the newly developed steels.

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Wpływ parametrów próby ściskania na gorąco na właściwości i strukturę stali wysokomanganowej dla motoryzacji

Tomaszewska A.

Hutnik, Wiadomości Hutnicze

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2015

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Vol. 82, nr 6

393--397

PL

Obecnie obiecującymi materiałami konstrukcyjnymi do zastosowań w przemyśle motoryzacyjnym są nowe stale z grupy Advanced High Strenght Steels (AHSS). Można do tej grupy zaliczyć stale wysokomanganowe, w których ujawnia się szczególny efekt pochłaniania energii w trakcie odkształcenia. Może on przebiegać poprzez tworzenie w strukturze odkształconego materiału mechanicznych bliźniaków w austenicie bądź poprzez przemianę fazową. Od takich materiałów wymaga się korzystnego połączenia właściwości zarówno mechanicznych, jak i plastycznych. W przyszłości materiały te będą mogły zastąpić stosowane obecnie konwencjonalne stale. W artykule zaprezentowano wyniki badań właściwości i mikrostruktury stali wysokomanganowej, poddanej próbie ściskania na gorąco. Przeprowadzono analizę wpływu parametrów odkształcania plastycznego, takich jak temperatura i prędkość, na maksymalne naprężenie uplastyczniające i odpowiadające mu odkształcenie. Badano mikrostrukturę i substrukturę stali. Wykazano zależność maksymalnego naprężenia uplastyczniającego od prędkości i temperatury odkształcania. W mikrostrukturze ujawniono efekty charakterystyczne dla procesów dynamicznej rekrystalizacji w trakcie odkształcania na gorąco.

EN

Currently promising construction materials for applications in the automotive industry are new steels from Advanced High Strength Steels named AHSS. To this group can be included high manganese steels, which disclose the specific effects of energy absorption during deformation. It can take place through the creation of mechanical twins or through phase transformation in deformed austenite. Of such materials a favorable combination of both mechanical and plastic properties are required. In the future, these materials will be able to replace the currently used conventional steels. The article presents the results of investigation of properties and microstructure of one grade of high manganese steel subjected to hot compression test. The influence of plastic deformation parameters such as temperature and deformation rate, on maximum yield stress and strain equivalent were analyzed. The microstructure as well as the substructure were examined. The microstructure revealed the effects characteristic of the dynamic recrystallisation during hot deformation.

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Kształtowanie plastyczne prętów ze stali wysokomanganowych w procesie walcowania na gorąco

Jabłońska M., Tomaszewska A., Kuc D.

Hutnik, Wiadomości Hutnicze

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2013

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Vol. 80, nr 7

486--489

PL

W pracy przedstawiono wyniki badań dotyczące wytwarzania prętów z nowych gatunków stali wysokomanganowych technologią walcowania na gorąco. Proces walcowania prętów o końcowej średnicy 12 mm prowadzono w TU Bergakademie Freiberg w zakresie temperatury 1150÷950°C w walcarce duo. Analizowano rozkłady temperatury oraz sił w trakcie procesu walcowania oraz dokonano oceny właściwości mechanicznych prętów. W wyniku walcowania, przy określonych parametrach kalibrowania, dla badanych stali otrzymano dobrej jakości pręty o korzystnych właściwościach wytrzymałościowych i plastycznych.

EN

The paper presents results of investigations on the forming of new species bars high manganese steel hot rolling technology. The rolling process was carried out on the final dimension ∅ 12 mm in the temperature range 1150 ÷ 950°C at the rolling mill duo at TU Bergakademie Freiberg. Were analyzed the temperature distribution and the forces during the rolling process as well as an assessment of mechanical properties of the steels. As a result of rolling the specific calibration parameters obtained for all quality steel bars of the assumed section. The study of the mechanical properties of the obtained bars proved very favorable combination of mechanical properties and plasticity of tested steels.

4

Report on the main areas of the materials science and surface engineering own research

Dobrzański L. A.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 49, nr 2

514--549

EN

Purpose: The purpose of the paper is to present the representative examples for the own scientific research in the area of the forming of the structure and properties of engineering materials including biomaterials, their properties testing and microstructure characterisation and modelling, simulation and prediction of the properties and structure of these materials after selected materials processing technologies. Design/methodology/approach: The main areas of the scientific interests reported in this paper on the basis of the own original research include forming of structure and properties of engineering materials including biomaterials using advanced synthesis and materials processing technologies and nanotechnologies, engineering materials including biomaterials properties testing and microstructure characterisation using very advanced contemporary research methodologies including electron microscopy, modelling, simulation and prediction of properties and structure of engineering materials including biomaterials using advanced methods of computational materials science including artificial intelligence methods. Findings: A general character of the paper concerning many aspects of material science research enabled a detailed description of research methodology and details concerning research results. Detailed information is included in many detailed cited works. Practical implications: Presented research results can be used in practice. Originality/value: The paper presents numerous research results which Has been made during last years generalising the achievements of the research team directed by the author.

5

Modyfikacja wtrąceń niemetalicznych pierwiastkami ziem rzadkich w wysokomanganowych stalach austenitycznych typu C-Mn-Si-Al

Grajcar A., Galisz U., Bułkowski L.

Hutnik, Wiadomości Hutnicze

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2011

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Vol. 78, nr 2

178-187

PL

W artykule opisano modyfikację składu chemicznego wtrąceń niemetalicznych pierwiastkami ziem rzadkich w nowoczesnej grupie stali austenitycznych wysokomanganowych typu C-Mn-Si-Al z mikrododatkami Nb i Ti. Wytopy trzech stali o różnej zawartości Si, Al i Ti wykonano w indukcyjnym piecu próżniowym, a modyfikację wtrąceń niemetalicznych przeprowadzono miszmetalem w ilości 0,87 g lub 1,74 g na 1 kg stali. Stwierdzono, że stale cechuje duża czystość metalurgiczna związana z małym stężeniem fosforu i gazów oraz nieco większa zawartość S, wprowadzanej do kąpieli wraz z manganem elektrolitycznym. Stale zawierają w większości drobne wtrącenia siarczkowe o wielkości od 21 do 25 mm2, a ich udział wynosi od 0,047 do 0,09 %, zależnie od zawartości w stali siarki. Oprócz siarczków duży udział stanowią węglikoazotki tytanu. Korzystny wpływ na ograniczenie udziału wtrąceń niemetalicznych i ich podatności do wydłużania w kierunku walcowania wywiera większy dodatek miszmetalu oraz mikrododatku tytanu. Środkową część zmodyfikowanych wtrąceń niemetalicznych stanowi zazwyczaj (Mn,Ti)S, a Ce, La i Nd zlokalizowane są na obrzeżach wtrąceń.

EN

Modification of chemical composition of non-metallic inclusions by rare-earth elements in an advanced group of high-manganese austenitic C-Mn-Si-Al-type steels with Nb and Ti microadditions was presented in the paper. Heats of three new-developed steels of a various content of Si, Al and Ti were melted in a vacuum induction furnace and a modification of non-metallic inclusions was carried out by the mischmetal in the amount of 0.87g or 1.74g per 1kg of steel. It was found that the steels are characterized by high metallurgical cleanness connected with low concentrations of phosphorus and gases at a slightly higher sulphur content, introduced to a melt together with electrolytic manganese. The steels contain fine sulfide inclusions with a mean size from 21 to 25 ?m2 in a majority and their fraction equals from 0.047 to 0.09 %, depending on sulphur and titanium content as well as mischmetal addition. Besides the sulfides, a large fraction of titanium carbonitrides was identified. The beneficial influence in decreasing a fraction of non-metallic inclusions and their susceptibility to elongate in a rolling direction has a higher addition of mischmetal and titanium microaddition. Usually, a middle part of modified non-metallic inclusions consists of (Mn,Ti) S, whereas Ce, La and Nd are localized in boundary regions of inclusions.

6

Microstructure evolution and phase composition of high-manganese austenitic steels

Dobrzański L., Grajcar A., Borek W.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 31, nr 2

218-225

EN

Purpose: The aim of the paper is to determine the influence of hot-working conditions on microstructure evolution and phase composition of new-developed high-manganese austenitic steels. Design/methodology/approach: Determination of processes controlling strain hardening was carried out in continuous compression test using Gleeble 3800 thermo-mechanical simulator. Evaluation of processes controlling work hardening and occurring after deformation at 900°C were identified by microstructure observations of the specimens solution heat-treated after plastic deformation to a true strain equal 0.23, 0.50 and 0.91. Phase composition of steels was confirmed by X-ray diffraction analysis. Findings: The steels have a fine-grained austenite microstructure with many annealing twins to a temperature of about 1000°C. The initiation of dynamic recrystallization occurs already after true deformation equal 0.29. Participation of fine grains arranged in a matrix of dynamically recovered grains essentially increases after increasing true strain to 0.5. Fully dynamically recrystallized microstructure of steel can be obtained after the true strain equal 0.9. The conditions of hot-working influence phase state of investigated steels. Steel no. 1 keeps stable austenite microstructure independently from conditions of plastic deformation. Steel with initial bi-phase microstructure keeps a certain portion of ε martensite, yet dependant on conditions of hot-working. Research limitations/implications: To determine in detail the hot-working behaviour of developed steels, a progress of microstructure evolution in subsequent stages of multi-stage compression test should be investigated. Practical implications: The obtained microstructure- hot-working conditions relationships and stress-strain curves can be useful in determination of power-force parameters of hot-rolling for sheets with fine-grained austenitic structures. Originality/value: The hot-working behaviour and microstructure evolution in various conditions of plastic deformation for new-developed high-manganese austenitic steels with Nb and Ti microadditions were investigated.

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Influence of hot-working conditions on a structure of high-manganese austenitic steels

Dobrzański L., Grajcar A., Borek W.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 29, nr 2

139-142

EN

Purpose: The aim of the paper is to determine the influence of hot deformation conditions on σ - ε curves and structure changes of new-developed high-manganese austenitic steels. Design/methodology/approach: The force-energetic parameters of hot-working were determined in hot-compression tests performed in a temperature range of 850 to 1050° C by the use of the Gleeble 3800 thermomechanical simulator. Evaluation of processes controlling work hardening at 850° C were identified by microstructure observations of the specimens water-quenched after plastic deformation to a true strain equal 0.22, 0.51 and 0.92. Findings: At initial state the steel containing 3% of Si and Al possesses homogeneous austenite structure with many annealing twins. Increased up to 4% Si concentration and decreased to 2% Al concentration result in a presence of some fraction of ε martensite plates. For applied deformation conditions, the values of flow stress vary from 250 to 450MPa - increasing with decreasing deformation temperature. A relatively small values of ε max deformation at temperatures of 1050 and 950° C allow to suppose that in this range of temperature, to form a fine-grained microstructure of steels, dynamic recrystallization can be used. At a temperature of 850° C, the dynamic recrystallization leads to structure refinement after true strain of about 0.51. Research limitations/implications: To determine in detail the hot-working behaviour of developed steels, a progress of recrystallization as a function of time at deformation temperature should be investigated. Practical implications: The obtained stress-strain curves can be useful in determination of power-force parameters of hot-rolling of high-manganese austenitic steels. Originality/value: The hot-working behaviour of new-devoloped high-manganese austenitic steels containing Nb and Ti microadditions was investigated.