Árbók VFÍ/TFÍ - 01.06.2000, Side 336

334 Árbók VFÍ/TFÍ1999/2000
impossible to reach a homogeneous initial temperature in the mould. It is nevertheless
tempting to propose that the mould core should be heated to its quasi-stationary temperature
before it is introduced to the casting process. This would decrease temperature gradients in
the mould during the fírst casting cycles and thus the thermal impact. It is also important
that during a long casting wheel stop care should be taken not to let the moulds cool down
too much. If the moulds are allowed to cool down they should bc submitted to the same heat
treatment process as new moulds.
In order to avoid water cooling of mould edges during FeSi water cooling a redesign of
the water spray system is needed. The current system sprays the moulds continuously as
they progress through the spray system. Thc side walls perpendicular to the rotating direction
are thcrefore always subject to water spraying. The side walls parallel to the rotating direction
could on the other hand be protected from the water by directing the water stream more
towards the center of the mould and away from the parallel side walls.
In order to protect the side walls from water spraying a complete redesign of the casting
wheel is necessary. The mould can not be allowed to pass through a continuous water stream
so the water can only be turned on when the moulds are in the correct position on the cast-
ing wheel. This will probably complicate the operation of the casting wheel so much that the
casting process will have to be automated. Automation of the casting process will on the
other hand make process supcrvision and data collection much simpler. This will for example
allow process changes to be made and monitored to see if they have the proposed effect on
mould life.
In order to verify the model developed and to learn more about the casting process further
development work is needed. Process parameters should be investigated in greater detail and
the value of boundary parameters could perhaps be modeled with the help of temperature
measurements. A heat camera could be used to establish the temperature of the mould and
FeSi surface during the casting process.
This study suggests that by determining, changing and controlling important casting
process parameters mould stress can bc reduced. It also implies that improvements in the
mould stress-state can be attained by changing physical boundary conditions.
The overall implication is that by decreasing temperature gradients in the mould, i.e. the
rate at which the temperature changes, mould stress-state can be improved.
Whether the proposed changes, if implementcd, will enhance mould life remains to be
seen. The effect of other process factors, such as the mould mechanical load, are out of the
scope of tliis study but should be investigated. The information gained by modeling and
analysis of the thermal load on the casting process and the casting mould nevertheless sug-
gest that steps can be taken in the right direction to improve the mould stress-state during
the process.
Tliis study has wider application for foundries that cast metal in simple moulds because
the mcthodology presented here is applicable to almost any casting process. After analyzing
the process in 1D a 3D model of the given mould can be constructed and the casting mould
analyzed. The methodology presented can therefore benefít foundries seeking information
about their own casting process and aiming to enhance mould life.