The purity of a steel material is defined by the presence of non-metallic inclusions. Inclusions such as oxides or sulfides represent a material separation due to their phase boundary. Depending on their formation, they can also taper and thus cause a notch effect. This can have a negative effect on the fatigue strength, especially in components subject to high stresses such as gear teeth or rolling bearings.
The DIN 50602 standard describes a microscopic test that can be carried out manually or fully automatically using image series tables. A defined sample area is systematically scanned and evaluated in terms of inclusion type, size and frequency. A subsequent mathematical calculation produces a characteristic value that indicates the purity of the steel material.
Standards: DIN 50602, SEP 1570
