Homogeneity of microstructure and Vickers hardness in cold closed-die forged spur-bevel gear of 20Cr Mn Ti alloy

Cold closed-die forging is a suitable process to produce spur-bevel gears due to its advantages, such as saving materials and time, reducing costs, increasing die life and improving the quality of the product. The homogeneity of microstructure of cold closed-die forged gears can highly affect their service performance. The homogeneity of microstructure and Vickers hardness in cold closed-die forged gear of 20 Cr Mn Ti alloy is comprehensively studied by using optical microscopy and Vickers hardness tester. The results show that the distribution homogeneity of the aspect ratio of grain and Vickers hardness is the same. In the circumferential direction of the gear tooth, the distribution of the aspect ratio of grain and Vickers hardness is inhomogeneous and they gradually decrease from the surface to the center of the tooth. In the radial direction, the distribution of the aspect ratio of grain and Vickers hardness is inhomogeneous on the surface of the gear tooth; while it is relatively homogeneous in the center of the gear tooth. In the axial direction of the gear tooth, the distribution of the aspect ratio of grain and Vickers hardness is relatively homogeneous from the small-end to the large-end of the gear tooth.

铌对20CrMnTi钢渗碳过程中晶粒粗化行为的影响

通过模拟渗碳试验,研究了Nb对齿轮钢20Cr Mn Ti晶粒粗化行为的影响。结果表明,由于析出含Nb析出相,Nb能显著提高在模拟渗碳过程中的晶粒粗化温度。晶粒粗化温度由析出相的体积分数和析出相的尺寸决定。当模拟渗碳温度较低时,时间对析出相尺寸影响不明显;当渗碳温度较高时,延长时间析出相明显粗化。因此,对于Nb含量较低的试样,1 h和6 h模拟渗碳的晶粒粗化温度接近;而对于Nb含量较高的试样6 h模拟渗碳的晶粒粗化温度比1 h的低。

20CrMnTi渗碳蜗杆磨削裂纹分析与措施探讨

对Y38滚齿机的关键件分度蜗杆采用20CrMnTi渗碳淬火,工件在磨削中产生磨削裂纹,使成品率只有52%~58%。针对这一问题进行分析研究,找到产生裂纹的真正原因,采取了相应措施,使产品合格率达到98%。

深冷处理对20CrMnTi钢尺寸稳定性及硬度的影响

研究了不同处理工艺对20Cr Mn Ti钢尺寸稳定性及硬度的影响,同时对微观组织的变化进行了分析。结果表明,渗碳+深冷+淬火+深冷+回火处理能够显著提高20Cr Mn Ti钢的尺寸稳定性,同时能够提高硬度。渗碳后的深冷处理对于尺寸稳定性的改善作用较大,深冷处理能够使部分残留奥氏体转变为马氏体,并在马氏体基体上析出超细碳化物颗粒。

20CrMnTi钢齿面局部点磨削力实验

为研究20Cr Mn Ti钢齿面局部点磨削过程的磨削机理,建立了20Cr Mn Ti钢齿面局部点磨削实验系统,提供了一种探索磨齿机理的模拟手段,跟踪观察了齿面划痕的磨削效果和微观形貌,拟定正交试验条件,测量了不同试验条件下局部点磨削过程的磨削力变化。结果表明:磨痕显微形貌存在明显的塑性隆起、应变硬化和热软化迹象;试件磨削力随着磨削速度的增大而减小,却随着进给速度和磨削深度的增大而增大;相对于法向磨削力,进给速度对切向磨削力的作用更为显著。