Effect of Si on grain boundary carbides in high carbon chromium bearing steel
To investigate the effect of Si content on grain boundary carbides at different positions on the cross-section of high carbon chromium bearing steel continuous casting slab,laser confocal microscope was used to simulate the cooling rates(20.0,2.0,0.2 ℃/s)at corresponding positions on the cross-section of continuous casting slab,and high carbon chromium bearing steel with different Si content was treated at this cooling rate.The precipitation amount and size distribution of grain boundary carbide were detected and analyzed through scanning electron micros-copy and X-ray diffraction.The results show that the increase of Si mass fraction(0.29％-1.48％)leads to the de-crease of segregation degree for C,Mo and Mn elements at grain boundaries,and then inhibits the precipitation of carbide at grain boundaries.At the same time,Si increases the Gibbs free energy of grain boundary carbide M23C6,resulting in the delay of precipitation time for carbide and shortening the growth time of grain boundary carbide.Thus,increasing Si content also has effect of refining grain boundary carbides.In addition,at a lower cooling rate(0.2-2.0 ℃/s),the Si content has a significant impact on the precipitation amount and size of grain boundary car-bides.Therefore,it can be inferred that the influence of Si content on grain boundary carbides in high carbon chro-mium bearing steel continuous casting slab is mainly manifested in the core and mushy region with a low cooling rate.An appropriate increase in Si mass fraction(≤0.71％)helps to reduce the precipitation amount and size of grain boundary carbides.The study can further contribute to the fine regulation of carbides in high-quality bearing steels.
high carbon chromium bearing steelgrain boundary carbidesSi contentcooling ratemicroscopic seg-regation
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