不同形变条件下非调质钢45MnSiVSQ的连续冷却转变

在Gleeble-3500热模拟机及热膨胀试验仪上测定了45MnSiVSQ钢动态及静态膨胀曲线,并采用切线法结合组织及硬度,测定了试验钢的静态和动态连续冷却转变(CCT)曲线,研究分析了形变温度和冷却速度对非调质钢45MnSiVSQ相变及珠光体片层间距的影响。结果表明:在0.1~3 ℃/s冷却速度范围内,珠光体片层间距随着冷却速度的增大而减小;对比950 ℃的动、静态CCT曲线可知,形变使试验钢相变起始温度有所升高,即相变孕育期缩短,其中对铁素体和珠光体相变区间影响尤为明显,而对贝氏体和马氏体相变区间孕育期的影响较小,表现为动态CCT曲线相比静态CCT曲线向左上方移动;对比不同形变温度下的动态CCT曲线可知,形变温度950 ℃时,贝氏体相变冷速区间为0.5~20 ℃/s,850 ℃形变时的贝氏体相变冷速区间为0.8~10 ℃/s。低温形变更利于铁素体和珠光体相变发生,减少了贝氏体、马氏体等非理想组织出现的机率。

Continuous cooling transformation of non-quenched and tempered 45MnSiVSQ steel under different deformation conditions

Dynamic and static dilatometric curves of non-quenched and tempered steel 45MnSiVSQ were measured on Gleeble-3500 thermal simulator and thermal dilatometer. The dynamic and static continuous cooling transformation (CCT) curves of the 45MnSiVSQ steel were measured by the tangent method combining with microstructure and hardness analysis, and the effects of deformation temperature and cooling rate on the phase transformation and the interlamellar spacing of the 45MnSiVSQ steel were investigated. The results show that as the cooling rate increases, the pearlite interlamellar spacing gradually decreases when the cooling rate is in the range of 0.1-3 ℃/s. Compared with the static and dynamic CCT curves of the 45 MnSiVSQ steel at 950 ℃, it can be seen that the deformation shortens the phase transformation incubation period especially in the ferrite and pearlite phase transformation range, but it has little effect on the incubation period in the bainite and martensite phase transformation zone, so that the dynamic CCT curves move to the upper left compared to the static CCT curves. By comparing the CCT curves at different deformation temperatures, it is found that bainite phase transformation occurs at 0.5-20 ℃/s when deformed at 950 ℃, while at 0.8-10 ℃/s when deformed at 850 ℃. Low temperature deformation is more conducive to the occurrence of ferrite and pearlite phase transformation, and reduces the probability of occurrence of non-ideal structures such as bainite and martensite.