<論文>高温浸炭した2mass%Si低合金2相鋼の組織

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The carburizing time is expected to be short at high temperatures, wheregrains of the dual-phase steel are fine and hardly grow. If it can be used forthe elevated temperature case hardening steel,the processing time might becomeshort by reducing carburizing time and by skipping the first step quenching forgrain refinement of the un-carburized core. In the present study, the applicabilityof the dual-phase steel for the elevated temperature case hardening steelhas been investigated.The 2.0 mass% Si- (0.01-0.08) mass% C- (0.1 mass% V, 0.05 mass% Nb and0.05 mass% Ti) steel were carburized at 1323 K for 10.8 ks, quenched from varioustemperatures and then tempered at 423 K. The microstructural observation,hardness measurement and tensile test of the core were carried out. When themicrostructure was controlled to be dual-phase with a + r at the carburizingtemperature, the grains were fine and no grain growth was observed during thecarburizing process. Therefore, the first step quenching for grain refinementmight be skipped. The core showed the excellent strength-ductility combinationcompared with the conventional case hardening steel. The distribution of hardnessin the carburized layer showed a gentle gradient due to the elevated temperaturecarburizing. The carburizing time was reduced to be 1/ 3 compared withthe conventional carburizing. The grains in the carburized layer were also refinedby additions of V, Nb and Ti.
秋田大学の論文