Papers by Władysław Zalecki
Journal of Materials Research and Technology
Journal of Aerospace Engineering
Głównym celem pracy było zbadanie wpływu morfologii bainitu na wybrane właściwości stali AHSS, w ... more Głównym celem pracy było zbadanie wpływu morfologii bainitu na wybrane właściwości stali AHSS, w tym odporności na ścieranie. Motywacją do podjęcia pracy była potrzeba zbadania przemiany bainitycznej zachodzącej w badanych stalach w warunkach izotermicznych, co ma szczególne znaczenie w technologii wytwarzania np. stali TRIP. Zbadano przebieg przemiany bainitycznej wybranych stali w warunkach izotermicznych. Na podstawie wyników badań dylatometrycznych i mikrostruktury opracowano wykresy TTT dla przemiany bainitycznej. Przeprowadzone badania ścieralności wykazały, że doświadczalna, bainityczna stal na szyny charakteryzuje się półtora raza większą odpornością na ścieranie w porównaniu do konwencjonalnej stali szynowej 900A. Zbadanie wysokotemperaturowych właściwości stali pozwoliło określić skłonność do tworzenia pęknięć, a tym samych określić podatność tych stali do spawania. Słowa kluczowe: stal bainityczna, przemiana fazowa, dylatometria, odporność na ścieranie INFLUENCE OF MICROSTRUCTURE ON SOME PROPERTIES OF AHSS STEELS The main aim of the work was to investigate the in&uence of bainite morphology on some properties of AHSS steels, including wear resistance. The motivation for the work was the need to study bainitic transformation under isothermal conditions, what is of particular importance in the manufacturing technology of e.g. TRIP steels. The bainitic transformation in some steels under isothermal conditions was investigated. The data obtained from dilatometric tests analysis and metallographic investigations were used to create TTT diagrams for bainitic transformation. The performed wear resistance tests have shown that experimental bainitic rail steel has revealed one and a half better wear resistance in comparison to conventional 900A steel for rails. Investigation of high temperature properties made it possible to determine the steel's tendency to cracking, i.e. their sensibility to welding.
Metallurgical Research & Technology
The paper demonstrates the capability of the developed phase transformation model to design the c... more The paper demonstrates the capability of the developed phase transformation model to design the cooling conditions in the Stelmor process allowing for obtaining different types of microstructures in wire rod of 32CrB4 steel. The model based on modified JMAK equation was developed using the results of the tests conducted in a DIL 805 A/D/T dilatometer. The model is composed of sub-models of ferritic, pearlitic, bainitic and martensitic transformations. Its predictive capability was confirmed in industrial conditions by performing trials with different settings of fans involved in the cooling process on the Stelmor line of CMC Poland. Excellent performance of the model was achieved through the modification of commonly used equations which allows accurate predictions of the phase transformations start and finish temperatures, as well as volume fraction of microstructural constituents, in a wide range of cooling rates. It was demonstrated that the model can effectively be applied to des...
Materials
The aim of this work was to develop a novel bainitic steel that will be specifically dedicated to... more The aim of this work was to develop a novel bainitic steel that will be specifically dedicated to achieving a high degree of refinement (nano- or submicron scale) along with increased thermal stability of the structure at elevated temperatures. The material was characterized by improved in-use properties, expressed as the thermal stability of the structure, compared to nanocrystalline bainitic steels with a limited fraction of carbide precipitations. Assumed criteria for the expected low martensite start temperature, bainitic hardenability level, and thermal stability are specified. The steel design process and complete characteristics of the novel steel including continuous cooling transformation and time–temperature–transformation diagrams based on dilatometry are presented. Moreover, the influence of bainite transformation temperature on the degree of structure refinement and dimensions of austenite blocks was also determined. It was assessed whether, in medium-carbon steels, it ...
steel research international
steel research international
Materials
The paper describes physical and numerical simulations of a manufacturing process composed of hot... more The paper describes physical and numerical simulations of a manufacturing process composed of hot forging and controlled cooling, which replace the conventional heat treatment technology. The objective was to investigate possibilities and limitations of the heat treatment with the use of the heat of forging. Three steels used to manufacture automotive parts were investigated. Experiments were composed of two sets of tests. The first were isothermal (TTT) and constant cooling rate (CCT) dilatometric tests, which supplied data for the identification of the numerical phase transformation model. The second was a physical simulation of the sequence forging-cooling on Gleeble 3800, which supplied data for the validation of the models. In the numerical part, a finite element (FE) thermal-mechanical code was combined with metallurgical models describing recrystallization and grain growth during forging and phase transformations during cooling. The FE model predicted distributions of the tem...
Computer Methods in Material Science
Several C-(3-5)Mn-Al-Mo steels with and without Nb microaddition, that can be classified as AHSS,... more Several C-(3-5)Mn-Al-Mo steels with and without Nb microaddition, that can be classified as AHSS, were developed in the present study. To design a thermomechanical treatment for AHSS steels with required multiphase structures a knowledge of their hot deformation resistance is of primary importance. The paper presents the results of the compression tests carried out at various temperatures and strain rates using the Gleeble simulator. A great potential of the investigated steels for the stabilization of retained austenite was observed even without a multi-stage heat treatment typical for TRIP steels. It was found that the steels are characterized by high deformation resistance dependent on Mn and Nb contents and hot deformation conditions. Niobium has a higher influence on the flow stresses and peak strain compared to manganese.
The article presents the results of studies on the impact of accelerated cooling after the austen... more The article presents the results of studies on the impact of accelerated cooling after the austenitisation of bars with a diameter of 180 mm made of structural steel S355J2 on the microstructure and mechanical properties. The aim of the research was to develop basic parameters of heat treatment technology using the heat remaining in the bars after hot rolling. Tests of heating and cooling of the bars were carried out in devices included in the line for semi-industrial hot rolling simulation, controlled cooling and heat treatment (LPS-B) at Łukasiewicz – IMŻ. The following cooling operations were performed after bar austenitisation: cooling in still air, controlled cooling with air blow, water-air mixture, water spraying and immersion cooling in water. Based on the research and analyses, it was found that the use of optimised variants of accelerated cooling leads to the modification of the microstructure and to grain refinement, without the formation of undesirable phase components. ...
Journal of Metallic Materials
The article contains results of research and analyses concerning application of nanostructured ba... more The article contains results of research and analyses concerning application of nanostructured bainitic steel in the form of plates for manufacturing of armour components. The presented results of examination of microstructure and properties include a wide range of laboratory experiments and industrial tests, which resulted in the achievement of the assumed functional properties. In the period of 2017-2021, a scientific and industrial consortium consisting of Łukasiewicz – Institute of Ferrous Metallurgy (leader); WITPiS, Tarnów Mechanical Works, Alchemia and Heatmasters Poland carried out a project funded by the POIR 04.01.04 programme aimed to develop the design and to manufacture an observation and protective container with a specified resistance to penetration by armour-piercing projectiles and with a lower mass of steel armouring in relation to that currently produced. The aim of the project was achieved by using armour plates made of nanostructured bainitic steel (nanobainitic...
Metals
The aim of the present study is to assess the effects of hot deformation and cooling paths on the... more The aim of the present study is to assess the effects of hot deformation and cooling paths on the phase transformation kinetics in a precipitation-strengthened automotive 0.2C–1.5Mn–0.5Si steel with Nb and Ti microadditions. The analysis of the precipitation processes was performed while taking into account equilibrium calculations and phase transitions resulting from calculated time–temperature–transformation (TTT) and continuous cooling transformation (CCT) diagrams. The austenite decomposition was monitored based on thermodynamic calculations of the volume fraction evolution of individual phases as a function of temperature. The calculations were compared to real CCT and DCCT (deformation continuous cooling transformation) diagrams produced using dilatometric tests. The research included the identification of the microstructure of the nondeformed and thermomechanically processed supercooled austenite products formed at various cooling rates. The complex interactions between the p...
Materiali in tehnologije, 2016
The article presents hot deformation and controlled direct cooling of hardened medium-carbon HSLA... more The article presents hot deformation and controlled direct cooling of hardened medium-carbon HSLA steel with micro-additions of alloying elements Ti and/or V. It also contains a study of the effect of thermomechanical-processing conditions on grain refinement and precipitation kinetics in the replacement of the conventional reheating-requiring heat treatment with a cost-effective technology. Controlled cooling with accelerated air and mist adjusted to lower carbon and hardenability-related alloying elements by means of employing experimentally designed heats, varying in the Mo content, was designed to meet the mining-industry requirements for mechanical properties. Besides microstructural-property relations, the vital problem of non-uniformity of the obtained properties is addressed with regard to within-part variances in the cooling rate of the as-forged, undeformed and dynamically recrystallized material. The strength and plasticity versus the microstructure of the produced fine pearlite/bainite structure with grain-boundary ferrite were evaluated. Microstructure-property relations allowed the formulation of the conclusions on the effect of direct-cooling conditions on the microstructure and grain substructure, their mutual synergic effect in controlling the microstructure, as well as guidelines for the transfer of the locally established process parameters into technological conditions. Keywords: thermomechanical processing, drop forging, accelerated cooling, grain refinement, tempered martensitê lanek predstavlja vro~o deformacijo in kontrolirano ohlajanje srednjeoglji~nega HSLA jekla z mikrododatkom legirnih elementov Ti in/ali V. Vsebuje tudi {tudijo vpliva pogojev termomehanske obdelave na udrobnjenje zrn in kinetiko izlo~anja pri nadome{~anju obi~ajnega re`ima ogrevanja za toplotno obdelavo s cenej{o tehnologijo. Da bi dosegli zahteve rudarske industrije in mikrostrukturne lastnosti, je bilo vzpostavljeno kontrolirano ohlajanje s tokom zraka in me{anice zraka ter vode, prilagojeno ni`jemu ogljiku in drugim elementom. Ti vplivajo na prekaljivost z uporabo eksperimentalnih talin, v katerih se je spreminjala vsebnost Mo. Poleg odvisnosti lastnosti od mikrostrukture, je glavni problem neenakost dobljenih lastnosti, kar je delno povezano z razlikami pri ohlajanju v kosu kovanega, nedeformiranega ali dinami~no rekristaliziranega materiala. Ocenjeni sta bili trdnost in plasti~nost v odvisnosti od nastale drobnozrnate perlitno/bainitne mikrostrukture s feritom po mejah zrn. Odvisnost mikrostrukture od lastnosti omogo~a postavitev zaklju~kov o vplivu pogojev pri neposrednem ohlajanju na mikrostrukturo in zrna substrukture ter njihov medsebojni vpliv pri kontroli mikrostrukture, kot tudi navodila za prenos lokalno ugotovljenih procesnih parametrov v tehnolo{ke pogoje. Klju~ne besede: termomehanska obdelava, kovanje s padalnim kladivom, pospe{eno ohlajanje, zmanj{anje zrn, popu{~en martenzit
Metals
The phase composition of nanobainitic steel 0.56–0.60%C, 1.68–1.95%Mn, 1.58–1.80%Si, 1.30–1.47%Cr... more The phase composition of nanobainitic steel 0.56–0.60%C, 1.68–1.95%Mn, 1.58–1.80%Si, 1.30–1.47%Cr, 0.57–0.75%Mo is described in this paper. The phase composition is controlled in order to obtain diversified mechanical properties for specific applications, such as armor plates. The effect of temperature and time of isothermal heat treatment on both the microstructure and the mechanical properties of the steel were determined. Dilatometric studies, as well as measurements of volume fraction and size distribution of retained austenite were carried out. Analysis of the kinetics of isothermal transformation in the temperature range of 200–225 °C for times of up to 144 h were also carried out, and the parameters of the production process of the steel were determined. A microstructure consisting of nanolathy carbideless bainite and blocky and lathy retained austenite, providing tensile strength of at least 2000 MPa, yield strength of at least 1300 MPa, and total elongation of at least 10% ...
Archives of Civil and Mechanical Engineering
Computer system for the design of technology of the manufacturing of pearlitic and bainitic rails... more Computer system for the design of technology of the manufacturing of pearlitic and bainitic rails was presented in this paper. The system consists of the FEM simulation module of thermal–mechanical phenomena and microstructure evolution during hot rolling integrated with the module of phase transformation occurring during cooling. Model parameters were identified based on dilatometric tests. Physical simulations, including Gleeble tests, were used for validation and verification of the models. In the case of pearlitic steels, the process of subsequent immersions of the rail head in the polymer solution was numerically simulated. The objective function in the optimization procedure was composed of minimum interlamellar spacing and maximum hardness. Cooling in the air at a cooling bed was simulated for the bainitic steel rails and mechanical properties were predicted. The obtained results allowed us to formulate technological guidelines for the process of accelerated cooling of rails.
Materials
The work presents results of phase transformation kinetics of hot-rolled 5% Mn steel subjected to... more The work presents results of phase transformation kinetics of hot-rolled 5% Mn steel subjected to different heat treatments. Three different schedules were introduced: isothermal holding in a bainite region, coiling simulation and intercritical annealing. The evolution of microstructure components was investigated using dilatometric and metallographic analyses. According to obtained results, the medium-Mn steel exhibits high resistance for γ/α transformation during the bainite transformation and coiling simulation (upon cooling from the austenite region). During 5 h isothermal holding, no bainite and/or ferrite formation was detected. This results in the formation of martensite upon cooling to room temperature. Differently, when the steel was subjected to the intercritical annealing at 720 and 700 °C (upon heating from room temperature), a final microstructure consisted of ferrite, martensite and retained austenite. At 700 °C, no fresh martensite formation was detected upon cooling ...
PROBLEMY TECHNIKI UZBROJENIA
: An innovative armour system containing plates made of nanostructured bainite steel is under dev... more : An innovative armour system containing plates made of nanostructured bainite steel is under development to improve operating properties of a light armoured observation-protective container (LAOC) providing the 2nd protection level according to STANAG 4569. Armour system solution of the container has been modified because the new plates have different mechanical and technological properties than currently used armour plates. The paper presents results of investigation of material characteristics and firing tests of plates made of nanostructured steel in the semi-industrial scale. To optimise parameters of heat treatment of the plates the kinetics of phase transformation was examined, and mechanical properties were measured, and changes in microstructure in the area of projectile interaction at firing tests were analysed for different variants of treatment. The reported investigations precede the industrial scale production process for plates made of the new grade steel designed for the armour system of LAOC. Optimisation of mechanical properties of the plates has been carried out by selection of such production parameters as chemical composition of the steel, hot working, interprocess heat treatment and temperature and time of final heat treatment (isothermal annealing). Effect of primary segregation of alloying and residual elements on protective properties of the plates is indicated. As a result of applying the annealing temperature in the range of 210-225°C (Ms temperature is ca. 200°C at cooling rate 1-2°C/s) and time in the range of 120-70 hours respectively, the following properties have been achieved: YS0.2 (yield strength) 1400-1500 MPa; UTS (ultimate tensile strength) 2000-2150 MPa; TE (total elongation) 10-13%, impact toughness KV at room temperature 10-16 J and hardness 590-610 HV (53-54 HRC). Microstructure of the plates consists of carbide free lathy nanobainite and 10-21% (volume fraction) of retained austenite. Plates of thickness 6.3 and 7.5 mm and ammunition type of 5.56x45 mm M193 and 7.62x51 mm API BZ have been used in the firing tests. Based on results of firing tests and microstructure examination in the area of projectile interaction the phenomena have been identified indicating high efficiency of ballistic protection of investigated plates, manifested by high ability to absorption and dissipation of projectile energy without susceptibility to cracking. Based on the results of mechanical properties measurements and firing tests a chemical composition of the nanostructured bainitic steel adjusted for industrial production of plates of thickness in the range of 6-8 mm has been developed. An analysis of container armour system mass reduction possibility, basing on results of investigation of the nano-structured bainite steel plates made in the semi-industrial scale, has been carried out. Basing on the analysis of the container construction and operational conditions some sensitive areas of ballistic protection have been specified to be subjected to firing tests. Ballistic examination will be carried out using the container segments representing the selected sensitive areas.
Metals, 2016
The work addresses the phase equilibrium analysis and austenite decomposition of two Nb-microallo... more The work addresses the phase equilibrium analysis and austenite decomposition of two Nb-microalloyed medium-Mn steels containing 3% and 5% Mn. The pseudobinary Fe-C diagrams of the steels were calculated using Thermo-Calc. Thermodynamic calculations of the volume fraction evolution of microstructural constituents vs. temperature were carried out. The study comprised the determination of the time-temperature-transformation (TTT) diagrams and continuous cooling transformation (CCT) diagrams of the investigated steels. The diagrams were used to determine continuous and isothermal cooling paths suitable for production of bainite-based steels. It was found that the various Mn content strongly influences the hardenability of the steels and hence the austenite decomposition during cooling. The knowledge of CCT diagrams and the analysis of experimental dilatometric curves enabled to produce bainite-austenite mixtures in the thermomechanical simulator. Light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to assess the effect of heat treatment on morphological details of produced multiphase microstructures.
The paper reports the results of theoretical and experimental work leading to the construction of... more The paper reports the results of theoretical and experimental work leading to the construction of a FEM (Finite Element Method) oriented code allowing the computer simulation of physical phenomena accompanying the steel deformation at temperatures which are characteristic for direct rolling of continuously cast charge, as well as the graphical and database oriented pre-and post-processing modules completing the system and making it user-friendly. A coupled thermo-mechanical model including inverse analysis technique was adopted for the solver. The advantage of the solution was the analytical form of both incompressibility and mass conservation conditions. This can prevent usual FEM variational solution problems concerning unintentional specimen volume loss caused by the numerical errors. It is very important for the discussed modeling because the deformation process is running in temperature range that is characteristic for the last stage of transformation of steel aggregation state. The well known machine allowing tests in the discussed temperature range is the Gleeble ® 3800 thermo-mechanical simulator. However, carrying out experiments with steel deformation in semi-solid state using this machine are very expensive. Therefore application of a dedicated computer simulation system is strictly required. Inverse analysis and appropriate modeling of the testing procedure makes tests possible, first of all, but it also results in lowering testing cost. The newest version of the Def_Semi_Solid v.5.0 is a unique FEM system supporting aided extra high temperature tests.
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Papers by Władysław Zalecki