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Mitsubishi Heavy Industries Ltd
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Mitsubishi Heavy Industries Ltd
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Application filed by Mitsubishi Heavy Industries LtdfiledCriticalMitsubishi Heavy Industries Ltd
Priority to JP14008280ApriorityCriticalpatent/JPS5767151A/en
Publication of JPS5767151ApublicationCriticalpatent/JPS5767151A/en
PURPOSE: To obtain a low-alloy steel with improved temper brittleness by adding La to a conventional low-alloy steel.
CONSTITUTION: This low-alloy steel consists of ≤0.15% C, ≤0.5 Si, 0.3W0.6% Mn, ≤0.035% P, ≤0.035% S, 2.0W2.5% Cr, 0.9W1.1% Mo, ≤0.2% La and the balance Fe with inevitable impurities. Temper brittleness is caused because impurities such as P, S and Sn are diffused and thickened by long-time use at high temp. Accordingly, by adding La having a great affinity for said impurities and forming stable deposits in grains and on grain boundaries at about 200W600°C, the diffusion and thickening of the impurities on the grain boundaries are reduced or prevented, and deterioration impact value by long-time use at high temp. is prevented. >0.2% La lowers the impact value.