Patent ID: 8104447

Claim:
Method for producing a piston for internal combustion engines in which a first part is pre-fabricated by hot forging and a recess which has at least one undercut is formed in the first part during pre-fabrication by forming on the first part, by means of a shaping tool, a projection which is directed substantially in an opposite direction to that in which the shaping tool acts, to which projection a lateral force which is directed in the direction of a receptacle is then applied to form the at least one undercut, a second part is pre-fabricated by hot forging and a second projection is formed on the second part whose dimensions are matched to the dimensions of the recess in such a way that the second projection can be slid freely into the recess of the first part and a volume of the second projection is at least equal to a volume of the recess, the first and second parts are joined together so that the second projection of the second part engages in the recess of the first part, and a compressive force is applied to the first and second parts which have been joined together which is sufficiently large and so aligned that material of the second projection of the second part flows into the recess in the first part and completely fills it to connect the first and second parts by positive fit.