Development of High Fatigue Strength Fine Grained Stainless Steel and Suitable Fatigue Test for Cylinder Head Gasket

Abstract

High fatigue strength stainless steel was developed for cylinder head gasket. Bead is press formed on the stainless steel gasket to prevent the leak of combustion gases and cooling water. However, fatigue failure is initiated from micro crack on the bead foot induced by press forming. On the developed steel, the micro crack was suppressed by refining the grain size to 1.5∼2.0μm. In addition, suitable fatigue test method for gasket was invented. It was difficult to properly evaluate the fatigue strength of stainless steel for gasket by traditional fatigue test because the test piece had neither bead nor the micro crack on the bead foot. On this invented test, cyclic compressive load is applied to test piece with bead. It was clarified that the developed steel exhibited higher fatigue strength than the conventional steel.