Cooling duct piston for a direct-injection diesel engine

A cooling channel piston for a direct injection diesel engine, the piston having a piston head and comprising:

• a first piston part comprising a piston base body forged from steel, a skirt, a pair of pin boss portions and a ring part;
• a second piston part soldered to the first piston part and consisting of steel or a nickel-based material and having an axially outside surface and an inside surface, the outside surface conspiring a combustion bowl with a border area and a central region and at least a part of a piston crown,
• wherein the first and the second piston parts together form a cooling channel that can be filled with oil,
• wherein the second piston part includes a circumferential contact surface which is arranged parallel to the piston crown and opposite the combustion bowl so that the contact surface can engage in a mating groove arranged in a contact web of the first piston part for soldering the two parts to one another;
• wherein the contact web runs from the skirt or from the ring part radially inwardly, and a circumferential surface of the web in a pressure/counter-pressure direction and in a pin direction lies in a same mechanical machined plane;
• and
• wherein a central region of the combustion bowl comprises a radial inside distance between the pin boss portions, and the central region of the combustion bowl is formed in an axial piston direction in such away that the central region is arranged closer to the piston crown than the border areas of the combustion bowl.