Gear type slewing bearing with gradually-changed hardness

The utility model discloses a gear type slewing bearing with gradually-changed hardness. The gear type slewing bearing with gradually-changed hardness is composed of an outer ring (or an external tooth ring), a steel ball, an isolation piece, an internal tooth ring (or an inner ring) and a seal skin, and is characterized in that the surface hardness of a gear is gradually changed, the bearing is divided into a soft band region, a transitional region and a normal hardness region from a position which approaches to the upper part of the gear of a non-mounting surface, and the hardness is respectively 25-40 HRC,40-50 HRC and 50-56 HRC; and the width of the soft band region is 0.2-0.3 times of full tooth width, the width of the transitional region is 0.2-0.3 times of full tooth width, and the width of the normal hardness region is 0.4-0.6 times of the full tooth width. The gradual change hardness gear type slewing bearing can be used for strengthening the extrusion resisting capability of the upper part of the ge