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Abstract

The influence of high-temperature austenitization on the isothermal transformation kinetics of a superhardenability treated steel has been studied by comparing the isothermal transformation diagrams. It is shown that the superhardenability effect is more pronounced in bainite than in ferrite–pearlite transformations. The critical transformation temperatures M_s, M_f, Ac₁ and Ac₃ are unchanged. The superhardenability effect is completely suppressed by austenitization above 1200°C and recovered by reaustenitization at typical (880°C) temperatures. It is also shown that this effect is related to a low oxygen content. From comparison of the transformation kinetics of a superhardenability treated steel and boron containing steels after high-temperature and grain refining treatments it is suggested that the superhardenability effect is possibly related to the boron effect by which boron increases the hardenability of low- and medium-carbon alloy steels.

MST/397

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Transformation kinetics of a superhardenability treated steel

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