Friction-welded and designed for low weight, good cooling and linear guidance as well as excellent durability, these KS mono-bloc steel pistons have a diameter of 130 mm.
In recent years Kolbenschmidt has driven an intensive developed of mono-bloc steel pistons with numerous successful introductions into the commercial vehicle market. This was supported by a close partnership with US and European vehicle and engine builders. "With all-steel pistons, we can ensure even higher mileages than with aluminum. Especially the mono-bloc piston with interior cooling and low emissions due to reduced surface temperatures is highly popular with customers," says CEO Horst Binnig.
In simplified terms, the steel pistons for the Scania engine consist of two parts: the upper part which forms the bowl and the ring zone, and the lower part forming the pin bore and skirt. Those two parts are produced as forgings and are pre-machined individually. Friction welding is used to join the two pieces into the mono-block piston. After heat treatment, the newly formed single piece piston is finish machined. The opening of the cooling gallery on the outer diameter above the skirt is sealed using two pre-shaped metal sheets. This is accomplished by laser-welding which is integrated into the production line.
The main goals of the KS piston design are low weight, good cooling capability, good guidance, high robustness, and increased product life. When compared to aluminum pistons, very compact designs can be realized. For example, the compression height can amount to less than 55 percent of the cylinder diameter with a sufficiently shallow combustion bowl.
The characteristic design features of all KS mono-block steel pistons are a long skirt directly connected to the pin boss and the under-crown. This design allows for a transfer of high side forces and a stable guidance in the cylinder bore without compromising the robustness of the piston structure. To minimize friction and weight, an asymmetric skirt design on the thrust and anti-thrust side was implemented. An innovative asymmetric barrel skirt profile, optimized skirt surface finish and the skirt coating LofriKS are features leading to a significant reduction of friction losses.