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Browsing by Subject "dodatek boru"

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    Item type:Doctoral Dissertation, Access status: Open Access ,
    Wpływ mikrododatków na hartowność stali z borem
    (2003-05-26) (Data obrony: 2010) Pelczar, Marta
    Wydział Inżynierii Metali i Informatyki Przemysłowej
    The effect of microalloying elements ($V,Ti,Nb,Al$) on the hardenability, the microstructure and mechanical properties of low alloyed steel $30CrMo4$ with addition of boron in the range of $0-0.008 m.\%$ was investigated. For investigations 10 laboratory melts were used. For investigrations different methods were applied, enabling the complex analysis of the effect of the chemical composition as well as heat treatment parameters on the hardenability, microstructure and mechanical properties of investigated steel. For analysis the content of the boron dissolved in austenite and effectively decreasing the rate of its decomposition the thermodynamic model was used. The effect of dissolved boron as well as undissolved carbonitride and nitrides BN and A1N on the hardenability and austenite grain growth were investigated. The investigations of the chemical composition of steel and heat treatment on the mechanical properties of investigated steel were carried out. Results of investigations have shown, that hardenability of low alloy steel for quenching and tempering can be significantly increased by addition of $0.003\%B$ with complex addition of $0.2%\V$ and $0.04\%Ti$. Addition of V below $0.2%$ is not efficient in order to increase the efficiency of B as intensifier of hardenability especially at higher nitrogen content because the relatively low chemical affinity of vanadium to nitrogen in comparison with boron.