齿轮钢晶粒尺寸对淬透性的影响

Effect of grain size on hardenability of gear steel

以20CrNiMoH齿轮钢为实验对象,研究了齿轮钢不同晶粒尺寸对其淬透性的影响。在同一棒料上截取端淬试样,经925、950、980、1 000和1 050℃等不同奥氏体化温度处理后开展末端淬火实验,结果发现经不同奥氏体化温度处理的试样淬透性能差距较大。进一步研究发现,20CrNiMoH齿轮钢试样淬透性能的不一致主要源自于不同试样晶粒尺寸的差别。20CrNiMoH齿轮钢试样经不同奥氏体化温度处理后,晶粒尺寸和长大趋势不同,晶粒尺寸长大会推迟过冷奥氏体相变发生,从而保持奥氏体的稳定性,提高齿轮钢的淬透性。此外还定量研究了20CrNiMoH齿轮钢晶粒度等级同淬透性硬度的关系,发现20CrNiMoH钢晶粒度级别提高1级,J5、J9和J15处端淬硬度值分别下降约1.9HRC、4.0HRC和1.3HRC,J9处端淬硬度受晶粒度的影响最为显著。

The effect of different grain sizes of gear steels on hardenability was researched based on the 20 CrNiMoH experimental steel.The quenching samples cut from one same bar were quenched after austenitizing treatment by different austenitizing temperature（925,950,980,1 000 and 1 050℃）.The results show that their hardenability are very different.By further study,it＇s found that the inconsistency of hardenability of 20 CrNiMoH gear steel specimens is mainly due to the difference of grain sizes.The grain sizes and their growth trend of 20 CrNiMoH gear steel specimens are different when their austenitizing temperatures are different,and the growth of grain sizes will delay the transformation of subcooled austenite,which can maintain stability of austenite and improve the hardenability of gear steel.The relationship between grain sizes and hardenability of 20 CrNiMoH gear steel is also studied quantitatively.It＇s found when the grain size level of 20 CrNiMoH steel increases by one grade,the hardness of J5,J9 and J15 decrease by 1.9 HRC,4.0 HRC and 1.3 HRC,respectively,and the hardness of J9 is most affected.