Effect of finish rolling and quench stop temperatures on impact-abrasive wear resistance of 0.35 % carbon direct-quenched steel
Novel high-hardness medium-carbon martensitic laboratory steel has been produced and tested for abrasive wear resistance. Different finish rolling temperatures (FRT) combined with either direct quenching (DQ) or interrupted quenching to 250 °C was applied to vary the content of retained austenite and hardness. The steel carbon content was set to 0.35 % to obtain a surface hardness of approximately 600 HB. Lowering the finish rolling temperature in the range 920–780 °C, i.e. into the non-recrystallization regime resulted in a more elongated prior austenite grain structure, which increased the hardness of the DQ variants without any significant loss of Charpy-V impact toughness. Although increasing the degree of autotempering by raising the quench stop temperature reduces the hardness of the martensitic microstructure, it was found that proper quenching stop temperature could be utilized to achieve balanced toughness and hardness properties. Impact-abrasive wear resistance as measured in impeller-tumbler tests with natural granite as the abrasive demonstrated that wear resistance increased with increasing surface hardness.