Abstract: A composite piston for internal combustion engines having a lower part and an upper part composed of ferrous material and joined together by a centering screw-threaded ring, is provided with the screw-threaded ring which comprises internal screw threads adjacent the lower rim thereof and an internal annular rib adjacent the upper rim thereof, the lower part of the piston has a corresponding annular recess adjacent its upper rim configured to enable the screw-threaded ring to be screwed onto the upper rim of the lower part of the piston and the upper part has an annular recess in the upper rim thereof configured to receive the internal annular rib, when the screw threaded ring is screwed onto the lower part, with the axially extending and radially extending boundary surfaces of the internal rib forced against the confronting boundary surfaces of the annular recess of the upper part.