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在DIL805L型膨胀仪上测定了55Si Mn Mo钎具钢在不同冷却速度下连续冷却时的膨胀曲线,结合金相-硬度法分析其相变规律及影响因素,获得了连续冷却转变曲线-CCT曲线。结果表明:55Si Mn Mo钢的临界点为:Ac_1=751℃,Ac_3=824℃;当冷却速度<0.15℃/s时,转变产物为铁素体、珠光体;随着冷速增加到0.15℃/s,转变产物开始出现少量贝氏体;当冷速>0.3℃/s时,有马氏体转变出现;珠光体、铁素体分别于冷速大于0.5℃/s、1℃/s时开始消失。
In the DIL805L dilatometer, the expansion curve of 55SiMnM brazing steel under continuous cooling at different cooling rates was measured. The phase transition law and influencing factors were analyzed by metallographic-hardness method, and the continuous cooling transformation curve-CCT curve was obtained . The results show that the critical points of 55Si Mn Mo steel are: Ac_1 = 751 ℃, Ac_3 = 824 ℃; when the cooling rate is less than 0.15 ℃ / s, the transformation products are ferrite and pearlite; / s, a small amount of bainite began to appear in the transformation products. When the cooling rate was> 0.3 ℃ / s, martensite transformation occurred. When pearlite and ferrite were more than 0.5 ℃ / s and 1 ℃ / s Began to disappear.