Retaining ring is the critical component of the turbine generator, is used for fixing and maintaining of rotor end windings to overcome the centrifugal force of high strength、 non magnetic、metallic ring component, in order to avoid the loss of the alternating magnetic field, the material of the retaining ring must be non-magnetic material.
 
Material of retaining ring includes 1Mn18Cr18N, 50Mn18Cr5 and 50Mn18Cr4WN, retaining ring can be used in various installed capacity power station such as 25MW, 60MW, 125WM, 300WM, 600MW, 1000MW and above .
 
NHI begins to manufacture retaining ring from 1970s, successively adopted half hot forging, spherical punch reaming, explosive forming deformation strengthening process, begins to study the hydraulic bulging strengthening production method of retaining ring from the 80's of the last century, NHI developed special press for manufacturing retaining ring in 1990. The process principle of the press is outside fluid hydraulic bulging strengthening method. In the beginning, the material of retaining ring is 50Mn18Cr5、 50Mn18Cr4WN, the specification is below 200MW, the annual output is about 300 pieces, the development of 1Mn18Cr18N material is from 2000. So far, NHI has manufactured more than 6000 retaining rings with material of 50Mn18Cr5, 50Mn18Cr4WN, 1Mn18Cr18N (referred to as the "double 18") of various specifications of retaining ring more than 6000 pieces, including more than 800 pieces "double 18" retaining rings, and 20 specifications from 3MW to 1000MW, the strength of products has reached Level 8 of ASTM A289 and the yield strength is 1430MPa. Products are widely used in various domestic generator equipment manufacturers, and are exported to Brazil, India and other countries.