GCr15SiAlMo贝氏体轴承钢球化退火工艺研究

Study on Spheroidizing Annealing of GCr15Si Al Mo Bainitic Bearing Steels

通过对新型无碳化物贝氏体轴承钢-GCr15Si Al Mo的球化试验研究,优化出一种适于轴承钢的循环球化退火新工艺。利用扫描电镜对球化后的显微组织进行观察,用X射线衍射仪对碳化物类型进行分析。结果表明,GCr15Si Al Mo无碳化物贝氏体轴承钢具有优良的碳化物球化特性。试样通过四周期的循环球化退火(大约6 h)后,组织中的碳化物基本球化完全,但是在700℃等温10 h的普通球化退火处理试样中仍存在大量的片状碳化物,由此证明,循环球化退火工艺比普通球化退火工艺的球化速度更快,球化更完全。球化处理后钢中碳化物的平均直径均达到了0.55μm以下,直径在1μm以下的碳化物百分比在93%以上,甚至达到99%。同时研究表明,Al可有效提高轴承钢的A1点,抑制球化过程中网状渗碳体的生成,并且适量的Al还能够改善轴承钢的球化特性,抑制碳化物的长大。

Through the spheroidization experiment of a novel kind of carbide-free bainitic bearing steel-GCr15SiAlMo, a new cyclic spheroidization annealing process, suitable for bearing steel, is optimized. The microstructures of the steels spheroidized are observed by the scanning electron microscopy （SEM） and the X-ray diffraction （XRD）. The results show that the GCr15SiAlMo bearing steels with the microstructures of carbide free bainite has satisfactory properties on the carbide spheroidization. After 4 cycles, the microstructure mostly contains spheroidized carbide, but there are a lot of lamellar carbides in the microstructures spheroidized at 700℃for 10 h. Consequently, compared with the conventional spheroidization process, the cyclic spheroidization process is more rapid and fully. By the spheroidization annealing, the average diameter of the carbides is less than 0.55 μm. The diameter of the carbides less than 1μm is more than 93%, and some even reach 99%. Meanwhile, these results show that Al can enhance the A1 point of the bearing steels and suppress the precipitation of the network carbides. Besides, adding moderate Aluminium will improve the annealing process and restrain the carbide growth in the steels.