Patent ID: 8317938

Claim:
Piston ring which comprises as a main body a nitride steel obtained by nitriding a steel composition which contains the following elements in the proportions given, expressed with respect to 100 weight % of the steel composition: Al: 1.1 weight % C: 0.7 weight % Fe: remainder Mn: 0.45 weight % Si: 3.0 weight % B: 0.001 weight % Cr: 2.0 weight % Cu: 0.05 weight % Mo: 0.5 weight % Nb: 0.002 weight % P: 0.03 weight % S: 0.009 weight % Sn: 0.001 weight % Ti: 0.003 weight % V: 0.11 weight % W: 0.003 weight %.