Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~16~6~0
The invention relates to ~n eJectromagnetic stirrer in a
continuous steel casting plant, in which the stirrer is
installed at a distance rom the casting path.
In the continuous cas-ting of steel, electromagnetic
stirrers in the secondary cooling zone are intended to effect
an accelerated dissipation o overheating by producing a flow
in the liquid casting core, produce a globulitic (equiaxed)
solidification structure in the middle of the casting, and pro-
duce a uniform distribution over the casting cross-section of
steel companion elements tending to form segregations. In
order to keep electrical losses as low as possible, the stirrer
must be mounted with its working face as far as possible in the
immediate vicinity of the casting surface, as is the case in
plants having a suficiently large distance between successive
support guidest and the stirrer front plate and surrounding
parts of the plant must be manufactured from a non-magnetic
material.
In order for the stirrer front plate to be as close as
possible to the casting surace in the case of relatively
small distances between the guide rollers, it is known to make
the upper and lower parts of the stirrer bevelled or tapered
in the casting direction so that additional rollers oE relatively
small radius can be mounted in the free space between the
bevelling and the next largest guide roller. These small rollers
produce equally large guide roller interspacings in the stirrer
region as well, whereby comparatively large, unsupported hot
casting sections can be avoided. However, it has been found in
practice that the guidance in the stirrer region is not suf-
ficient when introducing a flexible dummy bar having a relatively
short head and short chain links. The very small thickness of
the dummy bar and the resultant degree of play between
'$~$'
-- 1 --
6~0
oppositely located guide rollers may result, in the region
of the small rollers in the immediate vicinity of the stirrer,
in deflections or drifting of the dummy bar and in particular
may result in a tipping of the dummy bar head onto the stlrrer.
The result is that the dummy bar strikes against or becomes
wedged on the small rollers, leading to breakdowns and damage,
and also rubs against and strikes the stirrer from plate,
resulting in damage to the stirrer.
The ob~ect of the present invention is, when introducing
a flexible dummy bar from above or below into the casting
guide of a continuous steel casting plant, to protect on the
one hand an electromagnetic stirrer and on the other hand
rollers of the casting guide possibly present in the immediate
vicinity of the stirrer against chemical damage leading to
interruptions in the casting operation.
According to the present invention, there is provided
an electromagnetic stirrer in a continuous steel casting plant,
in which the stirrer is installed at a distance from the
casting path, one side of the stirrer facing the casting path,
and wherein a dummy bar is introduced into a casting guide,
characterized in that the side of the stirrer facing the
casting path is provided with a guide device for the dummy bar,
arranged at a distance from the casting path.
In this way a dummy bar, which on account of its degree
i of play in the casting guide may possibly swing into the stir-
rer, is kept away from direct access to the structurally rela-
tively weak front plate, which could result in damage. The
dummy bar is guided so that an undesirable collision between
the dummy bar and the guide rollers is largely a~oided.Because
the guide device is designed in such a way that it is arranged
at a distance from the casting path,i.e. does not normally
contact the casting surface during casting, non-uniform
--2--
!
6~
cooling of the casting surface is avoided and a metallurgi-
cally uniform casting product is guaranteed.
In one preferred embodiment the guide device consists
of at least one rail. This runs in the cas-ting path direction.
The embodiment is structurally inexpensive, results in only a
slight additional weight, and can easily be combined with the
front plate to form a single unit. This solution may prefe-
rably be employed with relatively light dummy bars in the
case of billet plants and fairly small cogged ingot plants
having widely spaced apart guide elements. With wider dummy
bars, a plurality of guide rails may also be employed as
required.
In another preferred embodiment of the invention the
guide device may consist of a reinforced stirrer front plate.
Preferably, the guide device has in the running direction of
the introduced dummy bar, end pieces directed towards the
casting path. By means of this robust embodiment heavier
dummy bars of fairly large cogged ingot sizes and also fairly
large slab sizes, should they be inadvertently deflected or
20 drift, can also be guided in the stirrer region, and damage
to the stirrer coils arranged immediately behind the front
plate or to adjacent casting guide rollers, caused by external
forces, is avoided.
The invention is described, with the aid of examples, in
the diagrammatically drawings, in which:
Fig.l shows in partial side view the introduction of a
dummy bar from below into a cogged ingot plant
with an installed stirrer with a reinforced front
¦ plate, and
Fig.2 shows in partial plan view a stirrer with a front
plate having guide rails.
~16:~6~)0
Fig. 1 shows, in partial side vlew, a sec-tion of a
secondary cooling zone of a continuous casting plant for
cogged ingots. For the sake of clarity, details of the plant
that are unimportant for the understanding of the invention,
such as the mould, spray nozzles, drive unit, arc radius,etc.,
- /
- /
f
. ~ -3a-
~6;;26~0
have been omi~t~d. An arrow 2 in~ic~tes the casting direction
in the plant. Pairs of oppositely situated guide rollers 1,
1' define the intended casting paths 3, 3', shown by the chain-
dotted lines. The rollers 1 guide the outer curved surface
and the rollers 1' the inner curved surace of a hot casting,
not illustrated. A partially illustrated electromagnetic
stirrer 4, whose side 23 faces the casting path 3, is installed
between the successive inner curved guide rollers 1' in the
casting direction 2. The reinforced front plate 5 of the
stirrer 4 is formed as a guide device for the dummy bar 9, and
is secured to the stirrer housing 7 by means of countersunk
bolts 6. The front plate is made of a non-magnetic material,
e.g. austenitic steel; and is of such a thickness and strength
that it prevents bending and denting, and thus damage, to the
sensitive stirrer coil 8 situated therebehind, caused by a
drifting flexible dummy bar 9 during its introduction. The
dummy bar 9 is introduced in this example from below, as
illustrated by the arrow ~0, against the casting direction 2.
The dummy bar head 11 is movably hinged on the dummy bar 9,
whereby a tipping ef~ect away from the casting path 3, in par- -
ticular as shown here, may occur in the case of casting guides
with widely spaced apart guide elements 1, 1'. In order to
prevent too great a deflection, in the region between the guide
rollers 1' and lower and upper edges of the stirrer, of the
- dummy bar 9 guided in the casting path with a degree of play 14,
the front plate 5 has at the top and bottom outwardly and
inwardly bent end pieces 12, serving as a guide for the dummy
bar. In this way there is prevented any tipping or canting of
the dummy bar chain and in addition any collision of the dummy
bar head with the stirrer or the roller 1' situated above and
below. In plants in which the dummy bar is introduced from
~16;Z6~10
above, these end pi~ces 12 are o~ course bent in the opposite
direction. As can be seen from the diagramf the stirrer fron~
plate is at a certain distance 13 from the inner curved,
intended casting path 3 or casting path boundary, with the
result that a sufficient degree of cooling is ensured over the
whole hot casting region facing the stirrer 4, during the
casting procedure. The stirrer 4 can of course also be mounted
on the outer curved side or on two opposite sides of the casting.
Fig. 2 shows another embodiment of the invention in a par-
tial plan view. An electromagnetic stirrer 15 acts over a dis-
tance 16 on a casting billet 17, shown partially in cross-
section. A front plate l9 of non-magnetic steel is welded to
the stirrer housing 18 on the working side of the stirrer 15.
The stirrer coil 20 is situated behind this front plate l9.
Guide devices for the dummy bar in the form of rails 21 are
mounted on the front plate l9 f which orm a rigid unit with the
latter and are at a distance 22 ~rom the billet surface.
These rails 21 may also be extended along the casting path
above and below the stirrer housing 18 to the vicinity of the
next casting guide element in order to ensure a satisfactory
guidance of the dummy bar. The rails 21 may be bent at their
ends so as to prevent the dummy bar becoming wedged.
