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This work aims at studying the change in constituent phases of High Manganese High Aluminum content steel through isothermal ageing and their effect on the plastic behavior of the produced steels. Optical and scanning electron microscope were employed for observing the significant change in microstructure at different heat treatment regime. XRD was applied to detect the major phases after isothermal process. Three samples with different phase consitituents were subjected to compression test. The results refer to the decomposition of γ-austenite into β-phase (B2, DO3), β-Mn, K-carbide is widely changed as a result of isothermal ageing process. The plastic behavior and strain-hardening property are improved linearly with k-carbide fraction. A bit enhancement of hardness has been observed with increasing k-carbide fraction after isothermal ageing process.

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In virtual design of hot stamping, the reliable description of the material flow behaviour is an important input to ensure accurate estimations of the final shapes of parts. Currently, to characterise the hot stamping material’s flow behaviour at elevated temperatures, tensile and upsetting tests are available. The focus of this article is on the determination of the flow curves of manganese-boron steel at elevated temperatures based on upsetting tests. The measurement of material flow properties directly out of the upsetting tests still remains a complex task due to its non-uniaxial nature. Therefore, traditional methods to calculate flow curves out of such measurements are not necessarily appropriate. It requires a method which considers multi-axial stress states as well as non-uniform strain evolution. In that way the calculation of the flow curves is appropriate and it can provide reliable input for simulations of hot stamping. In order to interpret measurements and deduce flow properties more precisely, simulations using Finite Element Method (FEM) of the tests themselves are executed. Indeed in FE-models it is possible to account for complex boundary conditions such as non-uniform temperature fields, non-uniaxial stress states and friction between upsetting die and the specimen during the deformation. With use of inverse optimisation, based on the final geometry of the deformed specimen, Coulomb’s friction coefficient is estimated. It is demonstrated that an almost constant value of the friction coefficient is achieved, even after using many different types of strain hardening to describe the material behaviour in the FE-models. Finally, it is demonstrated that the deduced material flow curves with use of inverse optimisation are more accurate than that of the directly calculated out of experimental results.

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As part of its long-term growth strategy Klöckner & Co aims to digitalize its entire supply chain. Thereby, EDI connections with suppliers for the exchange of standardized business data are one important step. With Tata Steel, Klöckner & Co now gained commitment from Europe’s second largest steel producer for a comprehensive EDI connection.

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The H2/CO ratio in the reducing gas is one of the most important factors that affect the reduction rate of iron ore pellets in the direct reduction processes. The present study is focusing on the effect of H2/CO gas ratio on kinetics of direct reduction of iron ore pellets. The H2/CO ratio was in the range of 1.0-2.6 which simulates the reducing gas composition in different direct reduction technologies (Midrex, HyL, and Syngas based direct reduction). The reaction rate constants and the apparent activation energy of the reduction process were calculated for both of the experimental and mathematical regression model. The unreacted core shrinkage mathematical formulations are applied to determine the rate controlling mechanism. The highest regressions and the lowest deviations from straight lines were obtained by the application of the mathematical formulations that corresponded to the interfacial chemical reaction mechanism and mixed control of chemical reaction with gaseous diffusion mechanism. The comparison between the calculated apparent activation energy and the standard ranges indicated that the rate controlling mechanism is mixed of the interfacial chemical reaction and gaseous diffusion. The contribution of chemical reaction in the rate controlling mechanism increased as the H2/CO ratio increased. The reaction rate constants and the apparent activation energy values were found to increase as H2/CO ratio increased due to the higher diffusivity of H2 compared to that of CO gas.

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