Roman KUZIAK, Valeriy PIDVYSOTSK’YY, Krzysztof RADWAŃSKI, Artur MAZUR
Sieć Badawcza Łukasiewicz – Instytut Metalurgii Żelaza im. Stanisława Staszica
Tomasz ZYGMUNT
ArcelorMittal Poland
Maciej PIETRZYK, Łukasz RAUCH, Daniel BACHNIAK
AGH – University of Science and Technology
OPTIMIZATION OF THE HEAT TREATMENT PROCESS TO OBTAIN THE REQUIRED DISTRIBUTION OF MECHANICAL PROPERTIES IN THE RAIL HEAD OF PEARLITIC RAILS
The paper presents metallurgically based approach allowing the design of the parameters of the pearlitic rail head heat treatment to obtain the targeted mechanical properties. The described solutions enable predicting the progress of phase transformations, final microstructure and mechanical properties distribution in the pearlitic rail subject to heat treatment. It also allows the optimization of the cooling conditions to obtain a strictly defined distribution of mechanical properties in the rail head. The program is developed as a result of research activities performed in the HyPremRail R&D project. The core of the program consists of the phase transformations model which is implemented in the numerical code based on the FEM for heat transfer calculations. The model predicts the pearlite nodule and colony size as well as cementite interlamellar spacing. Using these parameters, strength properties distribution in the rail can be predicted, since the phase transformations model is combined with the Fourier heat transfer equation. To perform the numerical simulations, the boundary conditions for heat treatment should be defined. On the contrary, using inverse analysis, the program can provide the cooling conditions allowing obtaining defined mechanical properties distribution in rail head.
Keywords: pearlitic microstructure, phase transformations, mechanical properties, heat treatment of rails, numerical modelling
Mirosław MICHAŁOWSKI, Stanisław KLUSEK, Piotr DUDKIEWICZ, Paweł KAMIŃSKI, Sylwia MANDZIAK
Celsa Huta Ostrowiec Sp. z o.o.
Mariusz ADAMCZYK, Piotr RÓŻAŃSKI, Ireneusz SZYPUŁA, Bogdan ZDONEK, Artur ŻAK
Sieć Badawcza Łukasiewicz – Instytut Metalurgii Żelaza im. Stanisława Staszica
OPTIMISATION OF THE TECHNOLOGY OF SMELTING AND REFINING OF STEEL INTO HOT ROLLED SECTIONS ON AN INNOVATIVE PRODUCTION LINE
Experimental investigations have been carried out to optimise the secondary steel treatment technology in a ladle in order to ensure the required quality of steel intended for hot rolling of sections on an innovative line, with a reduced number of rolling stands characterised by a higher intensity of plastic processing. Experimental heats were made according to various steel deoxidation variants during secondary treatment and continuous casting of two steel grades. Continuous ingots were used to hot roll sections of various cross-sectional sizes. Based on the results of metallurgical, microscopic and mechanical tests of the sections, guidelines for the optimal continuous ingot production technology for hot rolling of sections on an innovative production line were developed.
Keywords: low alloy steel, deoxidation, secondary metallurgy, mechanical properties, surface defects
Grażyna STANKIEWICZ, Marta KUBICZEK, Waldemar SPIEWOK
Sieć Badawcza Łukasiewicz – Instytut Metalurgii Żelaza im. Stanisława Staszica
A NEW SET OF CERTIFIED REFERENCE MATERIALS OF THE CHEMICAL COMPOSITION OF THE IRON ORES
The study assumed the production of ten certified reference materials of the chemical composition of raw ores, magnetite and hematite concentrates and pellets. The raw materials were obtained from Ukraine, Russia, Liberia, Brazil, Canada, and Norway. Their chemical composition was confirmed by the WD XRF method, and the mineral composition was analyzed with the use of X-ray diffraction. Radioactivity studies were also carried out. Dried, ground and mixed materials were subjected to homogeneity tests, which were carried out on samples melted in a mixture of lithium borates, using a ZSX Primus 2 X-ray spectrometer. Based on the results of the homogeneity test and the use of analysis of variance (ANOVA) for the results of individual determinations, the contribution of homogeneity in the uncertainty of the certified value was calculated. International certification round-robin program of tests with fourteen laboratories was organized and carried out. The results of the analyses were developed statistically in accordance with ISO Guide 35:2017. Certificates, data sheets and labels were developed. The production was carried out in accordance with the requirements of PN-EN ISO 17034.
Keywords: certified reference materials, chemical composition, iron ores, concentrates, pellets
Grzegorz GOLAŃSKI, Agata MERDA, Klaudia KLIMASZEWSKA
Czestochowa University of Technology, Faculty of Production Engineering and Materials Technology
Institute of Materials Engineering
MICROSTRUCTURAL ASPECTS OF LONG-TERM AGEING OF MARTENSITIC 9% Cr STEEL WITH AND WITHOUT BORON ADDITION
The study covered 9% Cr martensitic steels – X10CrMoVNb9-1 (P91) and X13CrMoCoVNbNB9-2-1 (PB2) after long-term ageing at the temperature of 620°C and soaking time up to 50,000 hours. The microstructural investigations of the tested steels were carried out using a TITAN 80–300 transmission electron microscope. The analysis of the changes in the microstructure included the identification of precipitates and computer image analysis: the measurement of dislocation density and mean diameter of the precipitates. The tests showed that the analysed steels still retained the lath martensitic microstructure, but also the processes of matrix softening were observed. The microstructure of the examined steels also showed numerous precipitates with various morphologies. The
micro-addition of boron in the PB2 steel, compared with the P91 steel, influenced the retardation of the microstructure degradation processes through the limitation of the growth of M23C6 precipitates and Laves phase. This resulted in a slowdown in the processes of recovery and polygonisation of the matrix of the tested steel.
Keywords: martensitic steel, PB2 steel, P91 steel, degradation of microstructure
RESEARCH PROJECTS FUNDED FROM THE INSTITUTE’S OWN FUNDS – ABSTRACTS