MOULE A REFROIDISSEMENT CONTINU, ELECTROMAGNETIQUE

ELECTROMAGNETIC CONTINUOUS CHILL CASTING MOULD

Abrégé anglais

Abstract
In an electromagnetic continuous chill casting mould
(10) for vertically casting bars or billets, with an
inductor (18), an internally cooled electromagnetic shield
(24) and a cooling device (12, 34) with a coolant outlet
opening (26, 36) directed onto the surface of the bar (32),
the tubular shield (24) has a round or oval cross-section,
wherein in case of an oval cross-section the large diameter
(d1) thereof lies parallel to the longitudinal axis (x) of
the bar and the ratio of large (d1) to small (d2) diameter
is 1:1 to 3:1.
The shield of round or oval cross-section is easy and
cheap to make and subject to hardly any plastic deformation
in operation, so that even after prolonged casting
operation, no elaborate straightening operations are
necessary.
(Fig. 1)

Revendications

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. Electromagnetic continuous chill casting mould for
vertically casting bars or billets, with an inductor (18),
an internally cooled electromagnetic shield (24) and a
cooling device (12, 34) with a coolant outlet opening (26,
36) directed onto the surface of the bar (32), character-
ised in that the shield (24) is tubular with a round or
oval cross-section, wherein in case of an oval cross-
section the large diameter (d1) thereof lies parallel to the
longitudinal axis (x) of the bar and the ratio of large (d1)
to small (d2) diameter is 1:1 to 3:1.
2. Chill mould according to claim 1, characterised in that
the ratio of large (d1) to small (d2) diameter is not more
than 2:1.
3. Chill mould according to claim 1 or 2, characterised in
that the shield (24) can be adjusted in height parallel to
the longitudinal axis (x) of the bar in relation to the
position of the inductor (18).
4. Chill mould according to any of claims 1 to 3,
characterised in that the shield (24) is arranged at least
partially inside a guide panel (22) of electrically
insulating material which is a poor heat conductor.
5. Chill mould according to any of claims 1 to 4,
characterised in that the coolant outlet opening (26) of
the cooling device (12) is arranged above the shield (24)
and directed onto a coolant guide surface (28) of a mould
body (30) arranged on the side of the shield (24) facing
away from the bar (32).
6. Chill mould according to claim 5, characterised in that
the mould body (30) with the coolant guide surface (28) can
be adjusted in height in relation to the position of the

inductor (18).
7. Chill mould according to any of claims 1 to 4,
characterised in that the coolant outlet opening (36) of
the cooling device (34) is arranged below the shield (24).

Description

2 ~ 8 8 0 r~
The invention concerns an electromagnetic continuous
chill casting mould for vertically casting bars or billets,
with an inductor, an internally cooled electromagnetic
shield and a cooling device with a coolant outlet opening
directed onto the surface of the bar.
It is known from US-A-3 985 179 that in electromagnet-
ic continuous chill casting moulds the electromagnetic
shield can be provided with a cooling system independent of
the bar cooling system. Hence it is possible to adjust the
shield in height in relation to the position of the
inductor without simultaneously altering the line or
surface of coolant impingement.
The shield serves to weaken the electromagnetic field
and hence reduce the electromagnetic force in the upper
region of the inductor directed towards the interior of the
bar at the bar surface, to maintain equilibrium with the
metallostatic pressure of the liquid bar portion, which
decreases upwardly. In practice, as vertical as possible
a position of the surface of the liquid bar portion and
also as small as possible a meniscus radius at the
transition from the vertical bar surface to the horizontal
metal bath level in the chill mould is to be ensured in
this way. The outer form of the shield usually has in
cross-section the shape of a triangle with the apex
pointing downwardly and the thickness increasing upwardly.
The designs of electromagnetic shields known from the
state of the art are fraught with the disadvantage that
they are plastically deformed after a certain number of
castings and have to be restraightened each time.
In view of the circumstances, the inventors set
themselves the aim of improving an electromagnetic chill
mould of the kind mentioned hereinbefore in such a way
that, while maintaining proven chill mould frame and
inductor configurations, the electromagnetic shield is
easier and cheaper to make as well as less maintenance-
intensive.
The object is achieved according to the invention by

7.~
the fact that the shield is tubular with a round or oval
cross-section, wherein in case of an oval cross-section the
large diameter thereof lies parallel to the longitudinal
axis of the bar and the ratio of large to small diameter is
1:1 to 3:1, preferably not more than 2:1.
The cross-sectional shape of the shield according to
the invention was calculated on the basis of calculations
with a simulation model of a casting apparatus, wherein
maintenance of the meniscus shape arising with proven
configurations of electromagnetic chill moulds as well as
of the velocity ield in the liquid bar portion was
established as a boundary condition.
For fine adjustment of shielding of the electro-
magnetic field in the upper region of the inductor, the
shield appropriately can be adjusted in height parallel to
the longitudinal axis of the bar in relation to the
position of the inductor. Here, the shield is preferably
arranged at least partially inside a guide panel of
electrically insulating material which is a poor heat
conductor.
In a first possible arrangement of the coolant outlet
opening of the cooling device, this is arranged above the
shield and directed onto a coolant guide surface of a mould
body arranged on the side of the shield facing away from
the bar. The coolant jet is here directed through between
the inductor and shield onto the bar surface, wherein for
fine adjustment of the line or surface of coolant impinge-
ment on the bar surface the mould body with the coolant
guide surface can be adjusted in height in relation to the
position of the inductor.
In a second possible arrangement of the coolant outlet
opening of the cooling device, this is arranged below the
shield and in general also below the inductor.
Further advantages, characteristics and details of the
invention follow from the description below of preferred
embodiments as well as with reference to the drawings.
These show:
,

2o~g(~r~3
ig. 1: a schematised cross-section through a chill
mould;ig. 2: a schematised cross-section through another
embodiment of a chill mould.
A chill mould 10 comprises according to Fig. 1 a
coolant box 12 for a coolant 14. A cooled inductor 18 is
fixed to the c.oolant box 12 by an intermediate layer 16 of
electrically insulating material. On a supporting body 20
attached to the coolant box 12 is mounted a guide panel 22
of electrically insulating material which is a poor heat
conductor, which is slidable in a vertical direction and in
which is inserted a tubular shield 24 of oval cross-
section. This shield 24 which is internally cooled with a
through-flowing coolant can for example be made of copper
or brass with a large outside diameter d1 in a vertical
direction of 18 mm, a small out ide diameter d2 in a
horizontal direction of 10 mm, as well as a wall thickness
of l mm.
The coolant box 12 comprises a coolant outlet opening
26 which is located above the shield 24 and which is
directed onto a coolant guide surface 28 of a mould body 30
which is adjustable in height also in relation to the
inductor 18, but independently of the guide panel 22. The
coolant 14 leaving the coolant outlet opening 26 is guided
over the coolant guide surface 28 onto the surface of the
bar 32.
In the design according to Fig. 2, the guide panel 22
with the integrated shield 24 is attached to the supporting
body 20 so as to be adjustable in height. The guide panel
22 extends vertically downwards over the inductor 18 and
thus simultaneously serves as a heat shield 22a. Cooling
of the bar takes place here below the inductor 18 via
nozzles 34 with nozzle opening 36 arranged around the bar
32, in which the coolant is atomised to a spray mist 38 and
directed onto the bar surface.

Dessin représentatif