Patent ID: 7472674

Claim:
Method of manufacture of a piston for an internal combustion engine, the said piston being formed from a steel part cast in one piece, wherein heating of a billet is carried out so as to bring it to an intermediate temperature between its solidus temperature and its liquidus temperature, and that shaping thereof by thixoforging is carried out, wherein the steel piston has a composition, in percentages by weight, of: 0.35%≦C≦1.2% 0.10%≦Mn≦2.00% 0.10%≦Is≦1.0% traces≦Cr≦4.5% traces≦Mo≦2.0% traces≦Ni≦4.5% traces≦V≦0.5% traces≦Cu≦3.5% traces≦Al≦0.060% traces≦Ca≦0.050% traces≦B≦100 ppm traces≦Ti≦0.050% traces≦Nb≦0.050% the other elements being iron and conventional impurities resulting from the manufacture.