As engine components that are subjected to intense demands, crankshafts require endurance strength to be as high as possible while keeping wear low. For decades, Maschinenfabrik ALFING Kessler has performed pioneering work in the area of this technical challenge. The first breakthrough came as early as 1913 with case hardening of crankshafts. Today, a range of procedures are used to increase the bending and torsion endurance fatigue strength and to reduce the surface wear. We have specialist knowledge in this area concerning the microstructure, the surface finish of the radii in the area of the big end bearing journal and the bearing journal, and the application of positive compressive residual stress. In 1952, ALFING made use of this expertise to develop hardening machine construction for inductive hardening of crankshafts, which is now a separate division in its own right. Over 500 ALFING hardening machines have been supplied to renowned car and commercial vehicle manufacturers the world over.
One of the process steps for increased endurance strength is induction hardening of the bearing journal radii. The inductor heats a big end bearing journal, which is then quenched by means of showering with coolant.
Stroke peening is performed at precisely defined locations of the crankshaft radii that are subject to high stresses.
The targeted application of compressive residual stresses – stroke peening – enables us to increase the endurance strength.