The barium ferrite BaFe12O19 with c-plane anisotropy, which possessed relative high saturation magnetization and low coercivity, had been synthesized by hydrothermal method with different reaction time of 5 h, 8 h,11 h,14 h, and 17 h. The X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM) were used to study the phase composition, microstructure and magnetic properties of barium ferrite, respectively. The results showed the intensities of the peak were enhanced and there was no impurity phase. With the prolonging of the reaction time to 11 h, 14 h and 17 h, the grain size increased, and the equivalent diameter was about 1 μm, and the thickness was about 100 nm. When the reaction time was 17 h,the coercivity of barium ferrite was 1104 Oe. The reduction of coercivity was ascribed to the increase of particle size and the reduction in magnetic anisotropy.
This article selects GCr18Mo steel to make an inner ring of rolling bearing. After isothermal quenching heat treatment, microstructure and mechanical properties are tested. The results show that microstructure and hardness from the surface to the core is uniform. The compositions are lower bainite and carbide, and both of them are small. The length-width ratio of lower bainite needle is about 10, and the average diameter of carbide in is 0.33μm. The hardness ranges from the surface to the core is between 715 HV and 755 HV, the average hardness of the inside and outside surface is 59.9HRC. Stress state of the surface is compressive stress and axial compressive stress is greater than the one of the hoop. Compressive stress in axial direction is about 588MPa, which is about 390MPa in the direction of the ring. After polishing, compressive stress in axial direction is about 483MPa, which is about 231MPa in the direction of the ring.
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