Slag Defects in Plates

Steel foundries producing large components often pay more attention to the solidification process and less to the gating and the filling pattern of the casting.

The foundry Voith simulated the solidification of a blade for a Kaplan turbine and poured two castings. The solidification simulation did not show any defects, but after casting, both blades had surface defects which had to be repaired. An analysis of the defects revealed oxides inside of them, which led to the conclusion that they may have originated during filling.

Kaplan blade casting (12 tons) which suffered from inclusion defects

Tracer particle analysis was used in a second simulation to check the filling. In fact, a vortex was detected at the same region where the inclusions were found. In order to change the filling pattern, and avoid the vortex and corresponding turbulence, the angle and location of the ingates were changed.

They are producing blades utilizing these findings since then without defects.

Tracer particles during the filling simulation showing vortices and turbulence in the defect area

* Courtesy of Voith Paper, Brazil