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1

Effects of the thermomechanical treatment on the microstructure and mechanical properties of ferrite–martensite dual phase steel

Ha M. T., Pham M. K., Nguyen H. H.

Archives of Materials Science and Engineering

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2023

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Vol. 124, nr 2

49--55

EN

Purpose: The study aims to investigate the effects of thermomechanical treatment, including tempering and hot–rolling, on the microstructure and mechanical properties of ferrite–martensite dual phase steel. Design/methodology/approach: The initial steel billet was a hypoeutectoid steel, which was annealed at 1000ºC, then hot–rolled at 920ºC, followed by austenitisation at various temperatures (730, 770, 800, and 830ºC), and finally quenched to obtain ferrite–martensite dual phase steel. X-ray diffractometer and optical microscopy investigated the microstructure and grain size of the dual-phase steel. Mechanical properties such as hardness, elongation, and tensile strength were also examined. Findings: The grain size decreased with increasing elongation percentage and remained constant after an elongation of 30%. The martensite/ferrite phase ratio increased with higher tempering temperatures. The hardness, elongation, and tensile strength reached a maximum when the tempering temperature was 800ºC. Research limitations/implications: Future studies could consider the effect of hot–rolling temperature or cold-rolling. Practical implications: The study proposes a straightforward and efficient thermomechanical treatment process to transform hypereutectoid steel into ferrite-martensite dual-phase dual- phase steel with improved mechanical properties. Originality/value: The study reveals the contributions of grain size and the martensite/ferrite ratio to the mechanical properties of ferrite–martensite dual steel through thermomechanical treatment.

2

Achieving high strength and large ductility of an ultrafine‑grained 211ZX aluminium alloy processed by improved thermomechanical processing

Luo Tao, Lei Lei, Feng Ke, Yang Ming, Jiang Yun

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e127, 2023

EN

Simultaneously achieving high strength and ductility has been a long-standing goal in aluminum alloys, while the increase in strength usually leads to ductility loss. In this study, a novel thermomechanical treatment (TMT) method, i.e., pre-existing precipitation in coarse grain (CG) and cryogenic rolling plus warm rolling followed by peak aging, is developed to achieve high strength and good ductility in 211ZX aluminum alloy. As a result, a composite nanostructure including ultrafine-grained (UFG) and nanoprecipitation is obtained. Compared to a conventional T6 sample, the multi-step TMT sample has a finer grain (205 nm), while numerous GP zones and θ" phases are dispersed inside the grain. The precipitation characteristics are similar to the T6 sample. The yield strength (635 MPa) and ultimate tensile strength (690 MPa) are about 81% and 53% higher than the T6 sample, respectively, with only a slight decrease in plasticity. Microstructural characterization and thermodynamic analysis confirmed that pre-existing precipitates and cryogenic temperatures facilitate the formation of the composite nanostructure. Quantitatively strengthening calculations demonstrate that the high strength is attributed to the ultra-fine grain strengthening and precipitation strengthening, while the high plasticity is mainly due to the reduction of dislocation density caused by recovery and recrystallization during the aging process as well as the massive production of nano-GIPs (interior grain precipitates).

3

Effect of Friction Machining on Low Carbon Steel with Titanium Traces in terms of Surface Hardening

Sheikh Ali R.

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 4

41--46

EN

This work is an experimental study of thermo-mechanical surface hardening of mild steel with trace elements like titanium in negligible concentrations. This is somewhat an advanced technique used to harden steel surface which can be hardened in many typical ways. The concept is combining the thermal as well as mechanical technique to attain better results. It is quite obvious that mechanical refers to the compressive loading during machining and thermal refers to producing heat on the surface of work piece. The ideal conditions are when the heat produced is enough to achieve austenite and then subsequent quick cooling helps in the formation of marten site, which is metallurgically the most highly strong phase of steel, in terms of hardness. The coolant used preferably is the emulsified oil which flows on the surface during machining with variable rate of flow as the optimum effect is. This process hardens the surface of steel and increases its resistance against wear and abrasion. Preference is to achieve surface hardening using the conventional equipment so that operational cost is kept low and better results are attained. This technique has been quite successful in the laboratory. It can be termed as friction hardening. Some improvements in the process scheme and working environment can be made to get better results.

4

A review of recent progress in mechanical and corrosion properties of dual phase steels

Kalhor Alireza, Soleimani Maryam, Mirzadeh Hamed, Uthaisangsuk Vitoon

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

309--322

EN

New concepts proposed for processing of dual phase (DP) steels as one of the main classes of advanced high-strength steels (AHSSs) to enhance their mechanical properties (strength–ductility combination) and corrosion resistance were introduced. The current review covers (I) the processing routes to obtain the ferritic–martensitic microstructures, (II) parameters of intercritical annealing (IA) treatment, (III) primary thermomechanical treatments, and (IV) post processing. First, the principal heat treatment methods, i.e., step quenching, intermediate quenching, and intercritical annealing of ferritic–pearlitic steel, as well as the partitioning of manganese were critically discussed. Then, the effects of holding time at the intercritical annealing temperature on the austenitization, grain coarsening kinetics, abnormal grain growth, and volume fraction of martensite were summarized. Next, the importance of cold deformation (notably rolling) and heating rate for the development of fine-grained DP microstructures (with chain-networked martensitic islands) through recrystallization and modification of the preferred nucleation sites for the austenite phase was discussed. Moreover, the applications of severe plastic deformation techniques (such as constrained groove pressing), thermal cycling (multi-step or repetitive intercritical annealing), and spheroidization heat treatment were discussed. Finally, the impacts of tempering, quench aging, and bake hardening on the properties of DP steel were reviewed. This short overview shows the opportunities that the conventional and innovative processing routes can offer for the potential industrial applications of DP steels, especially in the lightweight car body for the automotive industry to address the safety, fuel consumption, and air pollution issues.

5

Effect of forging sequence on evolution of parameters controlling microstructure in multistage drop forging process

Skubisz Piotr, Lisiecki Łukasz, Majta Janusz, Krzysztof Muszka

Computer Methods in Materials Science

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2019

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Vol. 19, No. 3

81--88

EN

The study presents the comparative analysis of competitive techniques of forging and its effect on microstructure. Numerical modeling of temperature and strain fields let theoretical prediction of the microstructure development in multi-stage drop forging process consisting of progressive sequence of multiple blows in preforming and die-impression forging operations. The aim of the modeling was prediction of the parameters of austenite in as-forged condition, prior to direct cooling and microstructure parameters of transformation products. Dynamic recrystallization kinetics were analyzed with use of Johnson-Mehl-Avrami-Kolmogorov (JMAK) model, taking advantage of numerically calculated of temperature, strain and strain-rate in selected location in the volume of the part. The obtained results show the possibility of look-ahead microstructure prediction in multi-stage hammer-forging process and form the basis for comprehensive selection of the forging process parameters aimed at producing required microstructure and its uniformity in the bulk.

PL

W pracy przedstawiono analizę porównawczą trzech sposobów kucia wielowykrojowego, która obejmuje dwa aspekty: 1) wpływ technologii na wskaźniki techniczno-ekonomiczne i siłowo-energetyczne oraz 2) rozkład w objętości i zmiany w czasie parametrów termo-mechanicznych, wpływających na kinetykę zjawisk dynamicznych w odkształcanym materiale oraz jakość odkuwki. Na podstawie wyników modelowania numerycznego oceniono wpływ zmian w technologii kucia na rozkład odkształceń, prędkość odkształcenia oraz temperatury w reprezentatywnych przekrojach odkuwki. Na ich podstawie wykonano modelowanie rozwoju mikrostruktury, oparte o klasyczne modele zarodkowania i rozrostu ziarna podczas rekrystalizacji dynamicznej i przemiany dyfuzyjnej przechłodzonego austenitu w oparciu o model JMAK. Jak wskazują wyniki modelowania, zmiany sposobu lub warunków kucia matrycowego stwarzają możliwości istotnego oddziaływania na rozkład odkształceń i silnie wpływają na temperaturę w objętości okuwki. To z kolei, może być wykorzystane do zniwelowania niekorzystnego wpływu warunków odkształcania na mikrostrukturę lub jej poprawy. Przedstawione wykresy pokazują istotne zmiany wielkości ziarna wraz z progresją odkształcenia w analizowanych punktach odkuwki. Jak widać, kształt odkuwki nie sprzyja uzyskaniu jednorodnego odkształcenia. Relatywnie małe odkształcenie podczas wstępnego spłaszczania pręta poprzedzający kilkunastosekundowy okres działania wysokiej temperatury, do momentu matrycowania, sprawia, że w obszarze zgrubienia prognozowane jest największe ziarno. Największe odkształcenie występuje w obszarze trzonu, jednakże sposób wstępnego kształtowania przedkuwki tego fragmentu odkuwki skutkuje przesunięciem w czasie odkształceń cząstkowych, przez co nawet na długości trzonu mogą wystąpić zmiany mikrostruktury. Zróżnicowanemu odkształceniu w zgrubieniu oraz trzonie odkuwki towarzyszą duże różnice prędkości odkształcenia, co przekłada się na kumulację odkształcenia w czasie. Analiza rozwoju mikrostruktury pozwala na odpowiednią korektę warunków kontrolowanego chłodzenia dla charakterystycznych fragmentów odkuwki, jak również odpowiednią korektę sekwencji i warunków realizacji kolejnych operacji kucia.

6

Assessment of compressive strength and compressive modulus parallel to the grain of oak and tauari wood after thermo-mechanical modification

Laskowska A.

Annals of Warsaw University of Life Sciences - SGGW. Forestry and Wood Technology

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2018

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No. 103

70--76

EN

European oak and tauari wood were subjected to thermomechanical modification. One treatment cycle consisted of three stages: heating the wood in a hydraulic press; wood densification; and cooling the wood samples in unheated hydraulic press without exerting pressure. The treatment temperature was 100 °C or 150 °C. The modification temperature significantly affected the compressive strength parallel to the grain of oak and tauari wood. Such dependencies were not found in the case of compressive modulus of elasticity parallel to the grain of tested wood species. The compressive strength of tauari wood modified at 100 oC and 150 oC was, respectively, 16% and 20% greater than the compressive strength of oak wood modified at the same temperatures. The compressive strength parallel to the grain of the oak and tauari wood depended linearly on wood density and load.

PL

Drewno dębu i tauari poddano obróbce termo-mechanicznej. W pierwszym etapie drewno ogrzewano kontaktowo w prasie hydraulicznej, następnie zagęszczano, po czym poddawano chłodzeniu w nieogrzewanej prasie hydraulicznej bez użycia ciśnienia. Temperatura półek prasy, przy której prowadzono proces zagęszczania drewna wynosiła 100°C lub 150°C. Temperatura obróbki wykazała istotny wpływ na wytrzymałość na ściskanie wzdłuż włókien drewna dębu i tauari. Zależności tych nie stwierdzono w przypadku modułu przy ściskaniu wzdłuż włókien badanych gatunków drewna. Wytrzymałość na ściskanie drewna tauari zagęszczanego w temperaturze 100°C i 150°C była odpowiednio o 16% i 20% wyższa niż wytrzymałość na ściskanie drewna dębu modyfikowanego w tych samych temperaturach. Wytrzymałość na ściskanie wzdłuż włókien drewna dębu i tauari zależała liniowo od gęstości drewna i obciążenia wywieranego na próbkę.

7

Design of Controlled Processing Conditions for Drop Forgings Made of Microalloy Steel Grades for Mining Industry

Skubisz P., Żak A., Burdek M., Lisiecki Ł., Micek P.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 1

445--453

EN

Effect of plastic processing and controlled cooling on microstructure and mechanical properties of experimental steel grades with microalloyed with Ti, V and/or Nb, varying in the content of Mo is presented as an offer for mining industry for replacement traditionally heat-treatable hardenability grades. The goal of the work is producing microstructure condition, which after controlled hot forging and direct heat treatment, involving quenching and self-tempering, are meant to provide good combination of mechanical properties, such as TYS 800 MPa, UTS 1050 MPa, elongation to fracture at least A5 15% and/or impact strength at room temperature KCV 60 J/cm2. Hardenability assessment and dilatometric examination allowed formulation of direct heat treatment guidelines, taking into consideration fields of temperature and strain in a typical hot forging process, estimated numerically, with the use of plastometric tests results, as well as the use of unique cooling cycles after forging. On the basis of numerical analysis of thermomechanical parameters and temperature progression, hot forging and direct cooling conditions were selected to achieve assumed structural components, morphology and dispersion of both grain and precipitates. For established heat transfer model and experimentally plotted cooling curves numerical analysis of direct cooling, enabled by definition of characteristic points of austenite transformation and CCT diagrams was conducted. The modeling aided with dilatometric characterization enabled prediction of transformation products distribution. The formulated conclusions were verified in the experimental sampling of forging, evaluating the applicability of designed combinations of chemical composition and cooling cycle for selected forged part for mining industry.

PL

Przedstawiono badania wpływu warunków odkształcania na gorąco i kontrolowanego chłodzenia na efektywność umocnienia eksperymentalnych stali z mikrododatkami Nb, Ti oraz V o zmiennej zawartości Mo. Pierwszym etapem pracy było zaprojektowanie składów chemicznych stali mikrostopowych, które po kontrolowanym kuciu na gorąco oraz obróbce cieplnej, polegającej na zahartowaniu i samoodpuszczeniu odkuwki bezpośrednio po kuciu, pozwolą na uzyskanie właściwości mechanicznych, tj.: granicy plastyczności 800 MPa, wytrzymałości na rozciąganie 1050 MPa, wydłużeniu A 5 15% i udarności w temperaturze otoczenia KCV 60 J/cm2. W oparciu o wyniki badań hartowności i analizę dylatometryczną opracowano wytyczne bezpośredniej obróbki cieplnej, uwzględniając obliczenia równowagi faz i wpływ temperatury na udział wydzieleń w wybranych wytopach oraz wyznaczone numerycznie pola temperatur dla typowego procesu kucia na gorąco, oparte o próby plastometryczne na symulatorze Gleeble 3800, oraz kontrolowane chłodzenie po kuciu. W oparciu numeryczną analizę parametrów termo-mechanicznych i zmian temperatury odkuwki modelowej dobrano warunki procesu kształtowania oraz schematy chłodzenia mgłą oraz przyspieszonym powietrzem, mające zapewnić założony skład strukturalny, morfologię oraz rozdrobnienie ziarna i cząstek umacniających. Na podstawie wyznaczonych punktów charakterystycznych i wykresów CTPc dla opracowanego modelu wymiany ciepła oraz uzyskanych krzywych chłodzenia wykonano analizę numeryczną bezpośredniej obróbki cieplnej, określając udział produktów przemian, podczas anizotermicznego chłodzenia bezpośrednio po kuciu. Wyniki modelowania zweryfikowano w doświadczalnych próbach kucia przeprowadzonych dla wybranych wariantów składu chemicznego i warunków chłodzenia, określając stosowalność opracowanych kombinacji składu chemicznego i obróbki dla wybranej odkuwki dla górnictwa.

8

Elaboration of Thermomechanical Treatment Conditions of Ti-V and Ti-Nb-V Microalloyed Forging Steels

Opiela M.

Archives of Metallurgy and Materials

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2014

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Vol. 59, iss. 3

1181--1188

EN

The goal of the work was to describe the forging conditions of thermomechanical treatment for Ti-V and Ti-Nb-V microalloyed steels. Conditions of hot-working allowing to obtain both the desired microstructure and mechanical properties of forgings were selected taking into consideration: precipitation analysis of MX-type (M – Nb, Ti, V; X – N, C) interstitial phases in austenite; research on the influence of the austenitizing temperature on the g-phase grain size; investigation of the continuous compression of specimens; and examination of the kinetics of recrystallization of plastically deformed austenite. The precipitation analysis of MX-type interstitial phases in austenite was conducted on the basis of a simplified thermodynamic model for equilibrium conditions as proposed by Adrian, assuming that individual MX phases are soluble in austenite. The effect of the austenitizing temperature in a range from 900 to 1200°C on the prior austenite grain size was investigated to verify the precipitation analysis of MX-type phases. The work also presents the results of the effect of Nb, Ti and V microadditions on flow stress, recrystallization kinetics and microstructure. Plastometric tests were carried out using the Gleeble 3800 thermomechanical test simulator. The studies provide the basis for a proper design of the manufacturing process for thermomechanical treatment of forged machine parts obtained from high-strength microalloyed steels.

PL

Celem pracy było opracowanie warunków kucia metodą obróbki cieplno-plastycznej stali mikrostopowych typu Ti-V i Ti-Nb-V. Warunkiobróbki plastycznej na gorąco, zapewniające pożądaną mikrostrukturę i własności mechaniczne odkuwek, dobrano z uwzględnieniem: analizy wydzielania się w austenicie faz międzywęzłowych typu MX (M – Nb, Ti, V; X – N, C), badań wpływu temperatury austenityzowania na wielkość ziarn fazy g, badań ciągłego ściskania próbek oraz badań kinetyki rekrystalizacji austenitu odkształconego plastycznie. Analizę wydzielania faz międzywęzłowych typu MX w austenicie przeprowadzono na podstawie modelu zaproponowanego przez Adriana, zakładającego rozpuszczalność w warunkach równowagi termodynamicznej, indywidualnych faz MX w austenicie. Badania wpływu temperatury austenityzowania w zakresie od 900 do 1200°C na wielkość ziarn austenitu pierwotnego przeprowadzono w celu weryfikacji analizy wydzielania faz typu MX. Wpracyprzedstawiono także wyniki badań wpływu mikrododatków Nb, Ti i V na krzywe płynięcia, kinetykę rekrystalizacji i mikrostrukturę. Badania plastometryczne przeprowadzono przy użyciu symulatora termomechanicznego Gleeble 3800. Przeprowadzone badania stanowią podstawę prawidłowego projektowania procesu technologicznego obróbki cieplno-plastycznej kutych elementów maszyn o wysokiej wytrzymałości ze stali mikrostopowych.

9

Effect of Technical Quality of Thermomechanical Die Forging of AA2099 Alloy

Łukaszek-Sołek A.

Archives of Metallurgy and Materials

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2014

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Vol. 59, iss. 3

997--1003

EN

The paper presents the results of investigations of a multicomponent third-generation aluminium alloy, classified as AA2099. The actual forging conditions were determined basing on the assessment of the quality of side surface of specimens subjected to compression in Gleeble 3800 simulator and on flow curves of the alloy, as well as numerical modelling of forging process performed with application of QForm 3D v.7 software. Compression tests were realized at temperatures 400-500°C, with a strain rate of 0.001-100 s-1 , up to a specified constant true strain value of 0.9. Microstructure examination in as-delivered state was performed with application of Leica DM 4000M optical microscope. The obtained results of isothermal deformation of specimens were correlated with the analysis of a characteristic layered pancake-type microstructure. The simulation of die forging of a complex-shape forging (high-current contact tip used in power engineering) at the temperature 500°C, was performed. The shape of a forging makes it possible to fully analyse the influence of thermomechanical process conditions on technical quality of a product. The simulation of forging process showed full correctness of material flow, with no signs of instability. At the same time, the analysis of investigations allowed to prepare and realize the industrial forging trials for a forging of a very complex shape, in a single step, at the temperature 500°C, with application of thermomechanical treatment. The forging attained high quality of shape and surface. Directional specimens were taken, in order to be subjected to microstructure examination and hardness testing. The data obtained from industrial tests, combined with the results of testing using Gleeble simulator as well as from numerical modelling, make up the guidelines for mechanical processing of AA2099 alloy at the temperatures 470-500°C.

PL

W pracy analizowano wyniki badań wykonanych na wieloskładnikowym, trzeciej generacji stopie aluminium, klasyfikowanym jako AA2099. na podstawie oceny stanu powierzchni pobocznicy próbek ściskanych w symulatorze odkształceń rzeczywistych Gleeble 3800 i krzywych płynięcia stopu, modelowania numerycznego procesu kucia w programie QForm 3D v. 7 ustalono warunki przemysłowej próby kucia stopu. Badania ściskania przeprowadzono w temperaturze 400-500°C z szybkością odkształcania 0.001 – 100 s-1 do stałej wartości odkształcenia rzeczywistego 0.9. Wykonano badania mikrostruktury w stanie dostawy na mikroskopie świetlnym Leica DM 4000M. Uzyskane wyniki odkształcenia izotermicznego próbek skorelowano z badaniami charakterystycznej warstwowej mikrostruktury typu „naleśnik”. Dokonano symulacji procesu kucia matrycowego odkuwki o bardzo złozonym kształcie (nakładka wysokoprądowa dla energetyki) w temperaturze 500°C. Kształt odkuwki umożliwia pełną ocenę wpływu warunków termomechanicznych procesu na jakość techniczną wyrobu. Symulacja procesu kucia wykazała pełną poprawność płynięcia stopu bez żadnych efektów niestabilności. Jednocześnie analiza badań pozwoliła na opracowanie i przeprowadzenie prób kucia przemysłowego odkuwki o bardzo złożonym kształcie w jednym wykroju w temperaturze 500°C z zastosowaniem obróbki cieplnoplastycznej. Odkuwka uzyskała wysoką jakość kształtu i powierzchni. Pobrano próbki kierunkowe do badań mikrostruktury i twardości. Uzyskane dane z prób przemysłowych w połączeniu z wynikami uzyskanymi z symulatora Gleeble i modelowania numerycznego stanowią wytyczne do kształtowania plastycznego stopu AA 2099 w zakresie 470 – 500°C.

10

Carbide spheroidisation in 100CrMnSi6-4 bearing steel by controlled rolling

Dlouhy J., Hauserova D., Novy Z.

Archives of Materials Science and Engineering

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2014

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Vol. 68, nr 2

87--92

EN

Purpose: This article describes influence of thermomechanical treatment parameters on microstructure and mechanical properties of 100CrMnSi6-4 bearing steel. Design/methodology/approach: Steel properties after accelerated carbide spheroidisation enables machining and cold forming as well as after conventional soft annealing. Apparently, structure after accelerated carbide spheroidisation is significantly finer than after long duration soft annealing – in terms of carbide particles and grain size. That enhances steel hardness and homogeneity of the structure in final state after hardening. Findings: Presented experiment deals with accelerated carbide spheroidisation of 100CrMnSi6-4 bearing steel during final stage of hot rolling. Main purpose is to achieve microstructure consisting of globular carbides and ferritic matrix directly after hot forming. Research limitations/implications: The combination of a suitable forming temperature, an appropriate amount of deformation and a possible reheating lead to globular carbide formation during austenite decomposition instead of cementite lamellae. Originality/value: Experiment results are promising for quenching and tempering in comparison with structure after conventional soft annealing with coarser. Finer ASR structure retains finer austenite grain at quenching temperature and higher dispersion strengthening.

11

Wpływ maksymalnej temperatury cyklu cieplnego na właściwości symulowanej SWC stali obrabianej termomechanicznie S700MC

Górka J.

Przegląd Spawalnictwa

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2013

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R. 85, nr 10

46--53

PL

W pracy przedstawiono wyniki badań wpływu maksymalnej temperatury cyklu cieplnego na właściwości symulowanej SWC stali obrabianej termomechanicznie o wysokiej granicy plastyczności S700MC. Badania przeprowadzono na specjalnie zbudowanym stanowisku badawczym wyposażonym w rezystancyjne źródło nagrzewania, kamerę termowizyjną Variocam Head HR i stanowisko komputerowe. Badania symulacji cykli cieplnych polegały na nagrzewaniu rezystancyjnym próbek przygotowanych do badania udarności oraz rejestracji cyklu cieplnego nagrzewania i chłodzenia. Symulowano pojedyncze cykle cieplne w zakresie temperatury od 400 do 1300ºC, co 100ºC, oraz cykle złożone. W czasie badania rejestrowano przebieg temperatury w funkcji czasu oraz wyznaczono następujące parametry: – Tmax – maksymalną temperaturę cyklu, – tn – czas nagrzewania próbki od temp. 50ºC do Tmax, – t8 – czas, po jakim temp. obniżyła się do 800ºC, – t5 – czas, po jakim temp. obniżyła się do 500ºC, – t8/5 – czas stygnięcia w zakresie temp. 800÷500ºC. Uzyskane próbki po procesie symulacji zostały poddane badaniom udarności, pomiarowi twardości oraz badaniom metalograficznym mikroskopowym. W celu określenia właściwości wytrzymałościowych i plastycznych symulowanej strefy wpływu ciepła stali S700MC przeprowadzono próbę rozciągania materiału na próbkach okrągłych.

EN

In this paper an influence of simulated thermal cycle on properties and HAZ structure of thermomechanically treated steel S700MC. The simulation of thermal cycles was carried out on a specially built test stand equipped with resistive heating source infrared camera VarioCam Head HR with 50 mm lens and a computer with software IRBIS 3 plus. Simulation was prepared for simple and complex thermal cycle. Simulation studies of thermal cycles consisted of resistive heating of samples prepared for the impact test. Single thermal cycles were simulated at temperatures ranging from 400 to 1300ºC, 100ºC and the cycle complex. For each temperature three repeats were carried out. During the course of the study, the temperature was recorded as a function of time and the following parameters were established: – Tmax – specimen max. temperature, – tn – specimen heating time from 50ºC up to Tmax, – t8 – time for temperature decreasing below 800ºC, – t5 – time for temperature decreasing below 500ºC, – t8/5 – specimen cooling time (temperatures range 800÷500ºC). The resulting sample, the simulation process, have been tested toughness, hardness measurement and metallurgical research microscope. In order to determine the strength and plastic properties of simulated heat-affected zone S700MC steel tensile test was carried out on samples of material round.

12

The influence of hot-working conditions on the structure and mechanical properties of forged products of microalloyed steel

Opiela M., Grajcar A., Gołombek K.

Archives of Materials Science and Engineering

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2013

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Vol. 59, nr 1

28--39

EN

Purpose: Results of the effect of thermomechanical processing conditions on the microstructure, mechanical properties and crack resistance are included in the present work. Conditions of forging with the method of thermo-mechanical treatment were developed basing on the analysis of precipitation kinetics of MX interstitial phases in a solid solution, plastometric examinations and investigations of the kinetics of undercooled austenite phase transformations. Design/methodology/approach: Light microscopy and transmission electron microscopy techniques were used to reveal the microstructure of samples obtained as a result of the thermomechanical forging. Mechanical properties and hardness tests as well as resistance to cracking using Charpy V samples at room and lowered temperature were carried out. Findings: Applied thermo-mechanical treatment allows obtaining fine-grained microstructure of austenite during hot-working and production of forged parts, which acquire advantageous set of mechanical properties and guaranteed crack resistance after controlled cooling from finishing plastic deformation temperature and successive tempering. Forgings produced with the method of thermo-mechanical treatment, consecutively subjected to tempering in the temperature range from 550 to 650°C, reveal the values of YS0.2

13

Tendencje rozwojowe stali konstrukcyjnej o specjalnych właściwościach (HPS)

Łagoda M., Wierzbicki T.

Materiały Budowlane

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2012

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nr 4

76-76

PL

W artykule zaprezentowano najważniejsze osiągnięcia metalurgii światowej, mogące znaleźć zastosowanie w budownictwie mostowym, a zwłaszcza stale o wysokiej granicy plastyczności, stale trudno rdzewiejące o podwyższonej odporności na korozję i inne.

EN

In the article is presented the major world metallurgy achievements. These attainments including steels with high yield point or weathering steels with improved corrosion resistance might be easily employed in bridge engineering.

14

Kształtowanie supersprężystych sprężyn NiTi do plastyki czaszki

Lekston Z.

Engineering of Biomaterials

|

2012

|

Vol. 15, no. 116-117 spec. iss.

33--36

PL

W pracy pokazano sposób przygotowania sprężyn NiTi w postaci prostych drutów, które po zamocowaniu w kształcie łuków na sklepieniu czaszki, w czasie leczenia kraniostenoz u dzieci działają ze stałą siłą w pożądanym zakresie odkształceń. Druty wykazujące supersprężystość uzyskano po przeciąganiu lub walcowaniu na zimno i wyżarzaniu w zakresie temperatur 400-500°C. Własności supersprężyste drutów sprawdzono w próbach rozciągania i trójpunktowego zginania. Z najlepszych drutów supersprężystych wykonano, prototypowe sprężynki do badań klinicznych i dobrano optymalne warunki kształtowania ich własności. Zarejestrowane w próbach trójpunktowego zginania krzywe zależności siły w funkcji ugięcia wykazują pożądane plateau podczas odciążania. Wykonane sprężyny podczas odciążania w pożądanym zakresie odkształceń 20-30 mm działają ze stałą siłą. Przygotowano typoszeregi sprężyn o różnych siłach oddziaływań w zakresie od kilku do około 10 N.

EN

The study shows how to prepare the NiTi springs in the form of straight wires which when attached in the shape of arcs to the vault of the skull operate with a constant force in the desired range of deformations during treatment of craniostenosis in children. Wires with superelastic properties were obtained after drawing or cold rolling and annealing in the temperature range of 400-500°C. Superelastic properties of the wires were tested in the tensile and three-point bending tests. The best superelastic wire was used to manufacture the prototype springs for clinical tests. Optimal conditions for developing their properties were selected. Force curves as a function of deflection registered during three-point bending tests show the desired plateau during unloading. During unloading in the desired range of deformations, i.e. 20-30 mm, the manufactured springs operate with a constant force. Series of types of springs with different interaction forces ranging from several to about 10 N were prepared.

15

Właściwości spoin stali obrabianych termomechanicznie o wysokiej granicy plastyczności

Górka J.

Przegląd Spawalnictwa

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2011

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R. 83, nr 12

31-35

PL

W artykule przedstawiono właściwości spoin stali obrabianej termomechanicznie S700 MC o grubości 10 mm wykonanych różnymi metodami spawania, przy różnych energiach liniowych. Badania metalograficzne, wytrzymałościowe oraz pomiar twardości pozwoliły na ocenę struktury i właściwości spoin oraz określenie wpływu ilości ciepła dostarczonego do obszaru spawania na wytrzymałość na rozciąganie, udarność i twardość spoin.

EN

The article presents the properties of thermomechanically treated welds of S700 MC 10 mm thick steel. Weldsare made with various methods of welding, and with different welding energies. The metallographic study, tensile test results and hardness measurement show the structure and properties of the welds. Moreover, it is obtained the effect of heat input to the welding area on the tensile strength, toughness and hardness of welds.

16

Morphological features of retained austenite in thermo-mechanically processed C-Mn-Si-Al-Nb-Ti multiphase steel

Grajcar A.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

|

Vol. 39, nr 1

7-18

EN

Purpose: The aim of the paper is to determine the influence of isothermal bainitic transformation temperature on morphological features and a fraction of retained austenite in a new-developed thermo-mechanically processed C-Mn-Si-Al-Nb-Ti multiphase steel. Design/methodology/approach: The thermo-mechanical processing was realized in a multi-stage compression test by the use of the Gleeble thermomechanical simulator. The steel was isothermally held for 600 s in a bainitic transformation temperature range of 250 to 500°C. A fraction and stereological parameters of retained austenite were determined by a computer image analyser using an optical microscope. The details of the retained austenite morphology were revealed in a scanning electron microscope and using EBSD technique. Findings: The maximum fraction of retained austenite (above 14%) was obtained for the temperatures of isothermal bainitic transformation from 400 to 450°C. Below 350°C, the largest grains of retained austenite located in a ferritic matrix transform to martensite and its fraction estimated by the use of computer image analysis is too high compared to X-ray investigations. Blocky, irregular grains located in a ferritic matrix are a main structural constituent of retained austenite in a temperature range up to 350°C. Increasing the isothermal holding temperature to a range of 400-450°C results in increasing a fraction of fine blocky and layer regions of the ă phase. Research limitations/implications: To describe in detail morphological features of retained austenite in fine-grained multiphase structures, a combination of different methods characterized by various resolution is necessary. Practical implications: The revealed morphological features of retained austenite are of great importance for mechanical stability of this phase during cold straining, affecting mechanical properties of advanced TRIP-assisted steels. Originality/value: Combined colour etching, scanning electron microscopy and EBSD (Electron Backscattered Diffraction) methods were applied to characterize retained austenite in a modern group of thermomechanically processed TRIP steels with Nb and Ti microadditions.

17

Microstructure forming processes of the 26Mn-3Si-3Al-Nb-Ti steel during hot-working conditions

Dobrzański L. A., Borek W.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

|

Vol. 40, nr 1

25-32

EN

Purpose: The influence of hot-working conditions on microstructure evolution of new-developed 26Mn-3Si-3Al-Nb-Ti high-manganese steel was investigated. Design/methodology/approach: The force-energetic parameters of hot-working were determined in continuous and multi-stage compression test performed in temperature range of 850 to 1100°C using the Gleeble 3800 thermomechanical simulator. Evaluation of processes controlling work-hardening were identified by microstructure observations of the specimens compresses to the various amount of deformation (4x0.29, 4x0.23 and 4x0.19). Findings: The investigated steel is characterized by high values of flow stresses from 250 to 430 MPa. Increase of flow stress along with decrease of compression temperature is accompanied by translation of ĺmax strain in the direction of higher deformation. Results of the multi-stage compression proved that applying the true strain 4x0.29 gives the possibility to refine the austenite microstructure as a result of dynamic recrystallization. In case of applying the lower deformations 4x0.23 and 4x0.19, the process controlling work hardening is dynamic recovery and a deciding influence on a gradual microstructure refinement has statical recrystallization. Research limitations/implications: To determine in detail the microstructure evolution during industrial rolling, the hot-working schedule should take into account real number of passes and higher strain rates. Practical implications: The obtained microstructure – hot-working relationships can be useful in the determination of power-force parameters of hot-rolling and to design a rolling schedule for high-manganese steel sheets with fine-grained austenitic structures. Originality/value: The hot-deformation resistance and microstructure evolution in various conditions of hot-working for the new-developed high-manganese 26Mn-3Si-3Al-Nb-Ti austenitic steel were investigated.

18

Wpływ parametrów wyżarzania ujednorodniającego i składu chemicznego na plastyczność stopów z układu Fe-Al z fazami międzymetalicznymi

Jabłońska M., Bernstock-Kopaczyńska E.

Hutnik, Wiadomości Hutnicze

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2010

|

Vol. 77, nr 8

397-400

PL

W artykule przedstawiono badania prowadzone pod kątem zdolności kształtowania stopów z układu Fe-Al na drodze obróbki cieplno-plastycznej. Analizowano wpływ wyżarzania ujednorodniającego i składu chemicznego na plastyczność. Po odlaniu i wyżarzaniu stopy poddano próbie osiowosymetrycznego ściskania na symulatorze Gleeble w temperaturze 900 i 1000 °C z prędkością odkształcenia 0,1 s-1 do wartości odkształcenia 1,0. Analizowano procesy zachodzące podczas odkształcenia.

EN

The alloys based from the Fe-Al system with intermetallic phases belong to materials for high-temperature applications with good creep resisting and mechanical properties. Limitation on the capacity for a broad their application as an alternative to expensive alloy steels of specific properties, is their insufficient plasticity, which is a factor inhibiting further their development as constructional materials. In this paper research has been conducted on the capacity for forming alloys from the Fe-Al system, via thermomechanical processing. The influence of homogenizing parameters and chemical composition on the plasticity of this materials was analyzed. After casting and annealing, alloys were subjected to axial-symmetric compression in the Gleeble simulator in the 900 °C and 1000 °C at 0.1 s-1 strain rates. The processes which take place during deformation have been analyzed.

19

Effect of isothermal bainitic transformation temperature on retained austenite fraction in C-Mn-Si-Al-Nb-Ti TRIP-type steel

Grajcar A., Krztoń H.

Journal of Achievements in Materials and Manufacturing Engineering

|

2009

|

Vol. 35, nr 2

169-176

EN

Purpose: The aim of the paper is to determine the influence of isothermal bainitic transformation temperature on a fraction of retained austenite for a new-developed C-Mn-Si-Al-Nb-Ti TRIP-type steel. Design/methodology/approach: The thermo-mechanical processing was realized in a multi-stage compression test by the use of the Gleeble 3800 thermomechanical simulator. The steel was subjected to six variants of processing with an isothermal bainitic transformation temperature in a range from 250 to 500°C. Identification of phase composition was achieved using microstructure observations and X-ray diffraction. To determine the fraction of retained austenite the Rietveld method was applied. Findings: The maximum fraction of retained austenite equal up to 16% can be obtained for the temperatures of isothermal bainitic transformation from 400 to 450°C, while the maximum carbon content in the ă phase equal 1.5 wt.% is present at the temperature of 350°C. Below 350°C due to high Ms temperature, the largest grains of retained austenite located in the ferritic matrix transform to marteniste. In a temperature range from 350 to 450°C, the Msă temperature has a negative value, stabilizing the retained austenite. Research limitations/implications: To determine in detail the influence of isothermal bainitic transformation conditions on a fraction of retained austenite, the knowledge of the effect of isothermal holding time is also important. Practical implications: The obtained microstructures and especially retained austenite fraction dependent on an isothermal bainitic transformation temperature can be useful in optimization of thermo-mechanical processing conditions of C-Mn-Si-Al TRIP-type steels. Originality/value: Combined colour etching and X-ray diffraction methods were applied for microstructure identification of modern group of TRIP steels predicted to use in the automotive industry.

20

Corrosion behaviour of Fe-Mn-Si-Al austenitic steel in chloride solution

Opiela M., Grajcar A., Krukiewicz W.

Journal of Achievements in Materials and Manufacturing Engineering

|

2009

|

Vol. 33, nr 2

159-165

EN

Purpose: The aim of the paper is to investigate the corrosion behaviour of the new-developed high-manganese austenitic steel in 0.5n NaCl solution. Design/methodology/approach: The steel used for the investigation was thermomechanically rolled and solution heat-treated from a temperature of 850°C. Corrosion resistance of investigated steel was examined using weight and potentiodynamic methods. In the weight method, the specimens were immersed in the prepared solution for 24h. In the potentiodynamic method, anodic polarization curves with a rate of potential changes of 1 mV/s in the anodic direction were registered. After the current density being equal 1 mA/cm2 was achieved, the direction of polarization has been changed. Basing on the registered curves, the pitting potential, repassivation potential, polarization resistance and corrosion current were determined. Findings: It was found that the steel is characterized by a partially recrystallized austenitic microstructure with numerous annealing twins and slip bands. According to the results of potentiodynamic analyses it was found that the samples of examined steel show poor corrosion resistance in the NaCl solution. The observed corrosion pits are related to the chemical composition. It is connected with the high dissolution rate of Mn and Fe atoms in NaCl solution. Fractographic analyses of samples revealed corrosion products on their surface in a form of pits with diversified size. Research limitations/implications: To investigate in more detail the corrosion behaviour of high-manganese steel, the investigations should include steels with a wider Al concentration. Practical implications: The obtained results can be used for searching the appropriate way of improving the corrosion resistance of a modern group of high-manganese austenitic steels. Originality/value: The corrosion behaviour in chloride solution of a new-developed Fe-Mn-Si-Al steel was investigated.