EN-GJS-600-3 | 5.3201 Tensile specimen with shrinkage cavity

A shrinkage cavity, which made up around a third of the cross-section of the tensile specimen, resulted in poor tensile strength values (400 MPa tensile strength, 2% elongation at break). In contrast, the specifications for the GJS-600-3 grade were easily achieved in the separately cast sample. The fracture surface shows quasi-splitting fracture (splitting fracture with honeycomb fracture components). The shrinkage cavity is lined with a graphite layer. During cooling, the austenite or ferrite dissolves less and less carbon. This normally diffuses to the existing graphite (spheres) and precipitates there. However, it can also precipitate on free surfaces, such as the blowhole surface in this case.

The matrix is pearlitic with ferrite seams around the graphite spheres.

Graphite classification according to EN ISO 945-1:2019

• Graphite form VI
• Guide number for the size range: 5