Effect of Heat Treatmert Processes on Quenched Microstructure and Properties of GCrl5 Steel Bearing Outer Rings
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摘要: 对GCr15钢城轨用轴承外环进行了4种不同工艺的热处理,通过扫描电镜和透射电镜观察、硬度测试以及残余应力测试,研究了热处理工艺对该轴承外环组织和性能的影响。结果表明:淬火、淬回火以及等温淬火(210 ℃等温1h和3h)试样的硬度平均值分别为861,750,835,701HV;等温淬火组织主要为马氏体和下贝氏体混合组织,且等温3h组织中的下贝氏体含量比等温1h的要多30%左右;最佳的热处理工艺为860℃保温20min后再于210℃等温3h然后水淬;经该工艺处理后轴承外环表面残余应力平均值为-264MPa,在距离表面0~50μm 范围内外环残余压应力水平较高,在距离表面50~600μm 范围内其残余应力平均值在-15 MPa附近波动,该种应力分布有利于提高轴承外环的使用寿命。Abstract: The GCr15 steel city rail bearing outer rings were heat treated by four different processes，and the effect of heat treatment processes on microstructure and hardness of the outer rings was studied by SEM and TEM observation，hardness testing and residual stress measurement. The results show that the average hardness of the quenched，quenched and tempered， austempering (for 1 h and 3 hat 210 ℃) outer rings was 861，750，835， 701 HV. The microstructure of austempering outer rings was mannly composed of martensite and lower babrite. The lower bannite content of the outer rings aus tempered for 1 h was about 30% less than that of the outer rings aus tempered for 3 h. The best heat treatment process for GCr15 steel bearing outer rings was austempermg for 3 h at 210 ℃ after 20 min intsulation isothermal at 860 ℃. After above heat treatment， the surface average residual stress of the outer ring was -264 MPa，the compressive resddual stress was rather higher n the range of 0~50 μm from surface，and the resddual stress was about -15 MPa n the range of 50~600 μm from surface. This kind of resddual stress distribution was beneficial to improve the service life of the bearing outer rings.
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Keywords:
- bearing outer ring /
- austempering /
- microstructure /
- hardness /
- resddual stress
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