논문 : AISI 51B20 보론첨가강의 경화능에 미치는 오스테나이트화 온도의 영향

Effect of hardenability, grain size and microstructural change according to the change of austenitizing temperature was analyzed in Jominy hardenability test of AISI 51B20 steel. Grain growth was small, 7㎛ and 12㎛ austenite grain sizes at austenitizing temperature of 900℃ and 1000℃, respectively, while rapid grain growth was observed up to 30㎛ austenite grain size at austenitizing temperature of 1100℃. As austenitizing temperature increased from 900℃ to 1100℃, hardenability in the region within 15 mm from end-quenched surface decreased due to the grains growth of bainite and martensite mixture, on the other hand the hardenability in the region exceeding 15 mm from end-quenched surface increased. Increased hardenability was attributed to different microstructures; pearlite, fine pearlite and bainite, and bainite and martensite structures at austenitizing temperature of 900℃, 1000℃ and 1100℃, respectively.