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Possibilities of biocompatible material production using conform SPD technology

Palán J., Maleček L., Hodek J., Zemko M., Dzugan J.

Archives of Materials Science and Engineering

2017

Vol. 88, nr 1

5--11

Purpose: At present, materials research in the area of SPD (severe plastic deformation) processes is very intensive. Materials processed by these techniques show better mechanical properties and have finer grain when compared to the input feedstock. The refined microstructure may be ultrafine-grained or nanostructured, where the grain size becomes less than 100 nm. One of the materials used for such processes is CP (commercially pure) titanium of various grades, which is widely used for manufacturing dental implants. The article deals with one of the technologies available for the production of ultrafine-grained titanium: Conform technology. CP titanium processed by CONFORM technology exhibits improved mechanical properties and very favourable biocompatibility, due to its fine-grained structure. The article presents the current experience in the production of ultrafine CP titanium using this technology. The main objective of this article is describing the behaviour of CP titanium during forming in the Conform device and its subsequent use in dental implantology. Design/methodology/approach: In the present study, commercially pure Grade 2 titanium was processed using the CONFORM machine. The numerical simulation of the process was done using FEM method with DEFORMTM software. The evaluation was performed by simple tensile testing and transmission electron microscopy. The first conclusions were derived from the determined mechanical properties and based on analogies in available publications on a similar topic. Findings: This study confirmed that the SPD process improves mechanical properties and does not impair the ductility of the material. The CONFORM process enables the continuous production of ultrafine-grained or nanostructured materials. Research limitations/implications: At the present work, the results show the possible way of continuous production of ultrafine-grained or nanostructured materials. Nevertheless, the further optimization is needed in order to improve the final quality of wires and stabilize the process. As these factors will be solved, the technology will be ready for the industry. Practical implications: The article gives the practical information about the continuous production of ultrafine-grained pure titanium Grade 2 and the possibility of use this material for dental implants. Originality/value: The present paper gives information about the influence of the CONFORM technology on final mechanical and structural properties with the emphasis on technological aspects.

Mathematical modeling of structure and mechanical properties of steel tubes production

Kvačkaj T., Zemko M.

Computer Methods in Materials Science

2007

Vol. 7, No. 1

17-23

Mathematical modeling of structure and mechanical properties of steel tubes production Kvačkaj T.1); Zemko M.1) 1) Department of Metal Forming, Faculty of Metallurgy, TU of Košice, Slovakia The article deals with FEM analysis, with mathematical modeling of structure evolution and with prediction of mechanical properties during hot rolling of seamless steel tubes. There is a brief description of stretch-reducing mill in the introduction. It is a forming unit that reduces diameter of the tube semi-finished product and at the same time changes the thickness of the wall without inner tool. In this unit there are achieving the final dimensions and after cooling process also the final mechanical properties of hot rolled tubes. Mathematical model of stretch-reducing mill of Železiarne Podbrezová, Inc., was created in Deform 3D software. Calibration sequence for rolling tube semi finished product diameter 144 mm and wall thickness 4,7 mm to diameter 88,9 mm and wall thickness 5 mm was chosen for creation of mathematical model of stretch-reducing mill. This calibration sequence consists of eleven rolling stands. Numerical simulation was created on mathematical model. By using the numerical simulation the values of thermo-mechanical parameters for each stand were gained. Time dependencies of strain, strain rate and rolling force were made from the obtained values. The next part presents mathematical model describing the tube production for low carbon steels grade St52 on analyzed calibration sequence. Model is valid for range of rolling start temperatures 870 – 960 °C and start rolling velocity 1,23 m.s-1. Model includes: - calculation of deformation temperature on each rolling stand in dependency on heating temperature, - calculation of kinetics of static recrystallization in conditions of continual cooling, - calculation of diameter of austenite grain after each deformation, - calculation of Ar3 and Ar1 temperatures in dependency on chemical composition, austenite grain size, amount of residual deformation and cooling rate, - calculation of austenite grain size after cooling to Ar3 temperature, - calculation of ferrite grain size in dependency on chemical composition, austenite grain size, amount of residual deformation and cooling rate, - calculation of structural fractions (ferrite, pearlite, bainite) in dependency on chemical composition, austenite grain size and cooling rate, - calculation of yield and tensile strength in dependency of structural fractions and ferrite grain size, - estimation of ductility for normalization conditions in dependency on chemical composition. Numerical simulation and process condition statistic data were used for calculation of material temperature both during tube pass through stretch-reducing mill and during cooling. Values of strain and strain rate from numerical simulation were substituted into the mathematical models. The calculated values were compared with experimental ones resulting from mechanical tests of industry rolled tubes of various chemical compositions. Good agreement of structural and mechanical properties was achieved for all chemical compositions and treatment conditions. The conclusion deals with the possibilities of increasing the accuracy of presented mathematical model as well as the possibilities of extension dimension assortment and areas of applications of mathematical modeling of seamless steel tubes production.

Symulacje numeryczne z wykorzystaniem MES w połączeniu z modelowaniem matematycznym rozwoju struktury oraz opisem własności mechanicznych podczas walcowania na gorąco rur bez szwu jest tematem niniejszej pracy. Model matematyczny reduktora pracującego z naciągiem w Żeleziarne Podbrezova, Inc. został stworzony w programie Deform 3D. Do obliczeń pola temperatur podczas przejścia rury przez reduktor oraz późniejszego chłodzenia wykorzystano modelowanie numeryczne i dane statystyczne z rzeczywistego procesu. Uzyskane z symulacji wartości odkształceń i prędkości odkształcenia przeniesiono do modelu matematycznego. W pracy porównano wyniki symulacji z wynikami doświadczalnymi otrzymanymi dla różnych składów chemicznych materiału. Porównanie to wykazało dobrą zgodności struktury oraz własności mechanicznych dla wszystkich badanych składów chemicznych i warunków procesu.