TWO PARTS ARE SIMPLY BETTER
When things really heat up in the combustion chamber, the heat must be dissipated. It isn’t enough for the piston to be made of highly temperature-resistant material, the geometry of the cooling channel is just as important! The cooling channel, however, is located between the piston crown and skirt. If the piston is forged from a single block, incorporating the cooling channel is quite complex. So why not forge the piston in two parts, bore the cooling channel in both directions from the eventual center, and then join the two piston halves? A clever idea! The stability and load capacity of the joint were the only obstacles in the way of making it a reality.
THE MORE POWER, THE BETTER
How do you form joints that are just as stable, or even more stable, than the base material itself? The answer is: with friction welding. But this requires elaborate equipment: a friction welding machine with a fixed and rotating workpiece holding fixture, including a heavy-duty power supply. In order to achieve a friction-welded joint from rubbing the piston parts together, the machine requires a driving force of 750 kW—as much power as a subway railcar!
MAHLE has been using friction welding for decades in valve manufacturing—to reliably connect the valve disk and stem. We are now applying this experience to the production of the new friction-welded TopWeld® pistons. With great success: even leading commercial vehicle manufacturers are relying on our powerful technology in original equipment.