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采用DIL805淬火膨胀仪、金相显微镜及显微硬度计,研究了ES355Al钢连续冷却过程的相变及组织转变规律,分析了冷却速率对ES355Al钢相变及组织演变的影响。结果表明:过冷奥氏体在冷却过程中发生铁素体转变、珠光体转变、贝氏体转变和马氏体转变。在冷速为0.2~1℃/s时,发生铁素体析出和珠光体转变;在冷速为2~7℃/s时,发生铁素体析出、珠光体转变和贝氏体转变,其中7℃/s为珠光体转变结束的临界冷速;,2℃/s、15℃/s分别为贝氏体、马氏体开始转变的临界冷速。ES355Al钢的显微硬度随着冷速增加而增加,由冷速0.2℃/s时的170 HV5增加到20℃/s时的350 HV5。
The phase transformation and microstructure transformation of ES355Al steel during continuous cooling were studied by using DIL805 quench dilatometer, optical microscope and microhardness tester. The effects of cooling rate on the phase transformation and microstructure evolution of ES355Al steel were analyzed. The results show that the ferrite transformation, pearlite transformation, bainite transformation and martensite transformation occur in the subcooled austenite during cooling. When the cooling rate is 0.2 ~ 1 ℃ / s, ferrite precipitation and pearlite transformation occur; when the cooling rate is 2 ~ 7 ℃ / s, ferrite precipitation, pearlite transformation and bainite transformation occur, among them 7 ℃ / s is the critical cooling rate at the end of pearlite transformation; and 2 ℃ / s and 15 ℃ / s are the critical cooling rates at which bainite and martensite begin to change. The microhardness of ES355Al steel increased with the cooling rate increasing from 170 HV5 at a cooling rate of 0.2 ℃ / s to 350 HV5 at 20 ℃ / s.