Speaker
Description
The internal quality of large steel ingots is an important target when designing and conducting the casting and solidification process.
In bottom-poured ingots, exogenous inclusions must be minimized through proper filling system design and optimized casting practice, including suitable casting rates and correct distribution of casting powder on the liquid metal. This is often achieved by placing powder bags at different heights inside the mould or at its bottom; as they burn upon contact with hot steel, they release powder. However, bags can ignite prematurely due to radiative heat: in this case the powder falls from height onto the steel surface, causing disturbances.
The metal jet from the ingot bottom can also disturb the free surface, especially at the beginning of filling.
Even with state-of-the-art practices, these aspects can contribute to powder entrainment, leading to inclusions, as observed by NLMK Verona in some cases after hot forging.
Numerical simulation allows to identify the causes of inclusions and their final position in the solid material, to assess whether they may lead to rejection.
This work presents a joint study by NLMK Verona and Transvalor on the simulation of a 115 ton ingot casting, where particles were introduced to model slag entrainment; their trajectories and final positions in the solid ingot were computed, with results consistent with NLMK Verona’s experience.
Particle behaviour in liquid metal was simulated in Thercast® using a Discrete Particle Model with a Eulerian–Lagrangian approach: liquid steel flow is computed by fluid dynamics (Eulerian), while inclusion transport is obtained from the force balance on each particle (Lagrangian).
| Speaker Company/University | Transvalor Italia |
|---|