Optical microscopy(OM),scanning electron microscopy(SEM)and electron probe microanalysis(EPMA)were used to analyze the distribution,microscopic morphology and elemental composition of abnormal microstructure in GCr15 bearing steel wire rod.The effect of the change of Cr element content on the microstructure composition of the test steel at room temperature after cooling was studied by Gleeble thermal simulation experiment,and the cause of abnormal microstructure in the bearing steel wire rod was analyzed.It was found that the abnormal structure in the microstructure of GCr15 bearing steel wire rod was martensite,and there was a significant difference between the Cr content in the abnormal martensite structure and the Cr content in the normal structure of the wire rod.The Cr content in the abnormal tissues measured by EPMA was above 2.1wt％,while the Cr content in normal tissues was about 1.4 wt％.At the cooling rate of 3 ℃/s,when the Cr content in the wire rod was 1.5 wt％,2.0 wt％and 2.5 wt％,the martensite content in the cooled microstructure was 0,13％and 42％,respectively,indicating that the increase of Cr content would promote the formation of martensite structure in steel.The segregation of Cr inherited from the billet is the root cause of the appearance of martensite in the microstructure of the hot-rolled wire rod after cooling.
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