A method for the production of a piston made of steel, for an internal combustion engine, in which the upper piston part is produced using the forging method, and the lower piston part is produced using the forging or casting method, and they are subsequently welded to one another. To simplify the production method and make it cheaper, the upper piston part is forged using the method of hot forming and of cold calibration, to finish it to such an extent that further processing of the combustion bowl and of the upper cooling channel regions can be eliminated.

A monobloc piston body for an internal combustion engine is provided. The piston body includes a first piece which includes a pair of skirt portions and a pair of pin bosses and a second piece which includes a crown portion with an upper combustion surface and an at least partially enclosed oil gallery. The first and second pieces are joined together at a joint that is located on a side of the oil gallery opposite of the upper combustion surface. The first piece is made through casting or forging, and the second piece is made through an additive manufacturing process, such as direct metal laser sintering.

A steel piston for an internal combustion including a cooling gallery containing a solid coolant, such as an aluminum-based material, is provided. The solid coolant has a thermal conductivity which is greater than the thermal conductivity of the steel material and fills at least 15 volume percent (vol. %) of the cooling gallery. The solid coolant provides for exceptional cooling along a crown of the piston, reduces corrosion and erosion along the crown, and avoids the problem of oil coking.

A method of constructing a piston, piston formed thereby, and piston body portions are provided. The method includes providing an upper crown portion at least one annular upper rib depending from the upper combustion wall to a free end having a tapered peak. The method further includes providing a lower crown portion having at least one annular lower rib extending to a free end having a tapered peak. Then, moving the upper crown portion and the lower crown portion toward one another and initiating contact between the upper crown portion and the lower crown portion at their respective tapered peaks. Then, continuing moving the upper crown and the lower crown further toward one another after making initial contact at their respective tapered peaks and forming a friction weld joint between the free ends of the at least one upper rib and the at least one lower rib free end.

Exemplary piston assemblies and methods of making the same are disclosed. An exemplary piston assembly may include a piston crown and a piston skirt that is received in a central opening of the crown. The piston crown may include a ring belt portion defining, at least in part, a cooling gallery. The crown and skirt may each further include corresponding mating surfaces that extend about a periphery of the crown and skirt. The skirt mating surface and crown mating surface may generally be secured to each other that the crown and the skirt cooperate to form a continuous upper combustion bowl surface. The skirt and crown may cooperate to define a radially outer gap about a periphery of the piston crown.