Abstract: The quality of girth gear was always the top priority in Quality Control Planning which was formed by casting and used for rotary kiln. The inner quality of girth gear was not only strictly tested by the ultrasonic nondestructive testing (UT), but also the surface quality was tested by magnetic particle nondestructive testing (MT) in the finished. UT unqualified, the girth gear failed. UT qualified, but MT unqualified, especially loose, slag and micro cracks on tooth surface caused MT unqualified, the defect could be polished cleanly. At the same time, VC unqualified, in order to solve this problem, a surface cold welding technology was applied to the teeth on the girth gear technology only for the appearance "beautifying". Repair performance of the gear ring itself did not affect.
