热变形行为与动态再结晶对低硫齿轮钢硫化锰夹杂物的影响

Effects of hot deformation behavior and dynamic recrystallization on MnS inclusions in low sulfur gear steel

利用Gleeble-1500热-力模拟试验机对齿轮钢FAS3420H进行了热压缩试验,研究变形温度、变形量等对硫化锰夹杂物尺寸和相对塑性的影响。研究发现,在变形过程中,硫化物的碎化与长大现象交替进行,变形温度与变形量对硫化锰夹杂物的尺寸影响较大,其变化规律与齿轮钢基体再结晶程度有关。变形温度较低(900℃)时,随着变形量的增加,长宽比小的硫化物数量先减少后增加,相对塑性呈降低的趋势,而动态再结晶分数逐渐增加;变形温度较高(1200℃)时,随着变形量的增加,长宽比小的硫化物数量先增加后减小,MnS相对基体变形能力呈增加的趋势,但整体比低温轧制时要低,而此时在较低变形量下已发生充分的动态再结晶。由此可见,在实际轧制过程中选择较高温度,基体在变形量较小时即发生动态再结晶,在基体变形和再结晶过程中晶界移动的共同作用下,可以得到尺寸较小、数量较多的硫化锰夹杂物。

Hot compression test for gear steel FAS3420H was conducted by Gleeble-1500 thermomechanical simulator,and the effects of hot deformation parameters such as deformation amount and deformation temperature on size and relative plasticity of MnS were studied.The results show that during the deformation process,the fragmentation and growth of sulfide occur alternately,and the deformation temperature and deformation amount have a significant impact on the size of MnS inclusions.The change rule is related to the degree of recrystallization of the gear steel matrix.When the deformation temperature is low(900℃),with the increase of deformation amount,the amount of sulfides with small aspect ratio first decreases and then increases,and the relative plasticity presents a downward trend,while the dynamic recrystallization fraction gradually increases.When the deformation temperature is high(1200℃),with the increase of deformation amount,the amount of sulfides with small aspect ratio first increases and then decreases,and the relative plasticity shows an increasing trend,however,it is generally lower than when rolling at low temperature,and at this time,sufficient dynamic recrystallization occurs at a lower deformation amount.It can be seen that in the actual rolling process,when a higher temperature is selected,the matrix is prone to dynamic recrystallization.Under the interaction of matrix deformation and grain boundary movement during the recrystallization process,smaller and more MnS inclusions can be obtained.