Note: Descriptions are shown in the official language in which they were submitted.
11(~(~279
Background of the Invention
The present invention relates to the generation of a rotating
electromagnetic field in the withdrawal and support track for a continuous
casting.
It is known generally to generate rotating electromagnetic fields
for moving (stirring) the content of still liquid metal (steel) inside the
solidifying ingot or casting, as it is withdrawn from the mold during con-
tinuous casting. The stirring field is generated by means of a suitable
coil or coil arrangement; see for example German printed Patent Application
No. 25 59 511. Figure 3 of this patent shows the pole arrangement used in
this case. The German printed Patent Application No. 24 01 1~5, Figures 23
and 24, illustrates how three poles can be arranged in a construction part
of parallelepiped configuration, having dimensions, in millimeters, of 800
by 300 by 400. The long dimension runs parallel to the withdrawal axis of
the casting.
Upon installing this electromagnetic device, one must interrupt
locally the support of the casting by rolls of the track. For a width di-
mension of the support device of 300 mm, the ingot will have no support for
at least 500 mm. This lack in support is highly detrimental. The ingot may
readily form a bulge on account of the ferrostatic pressure, whereupon the
ingot may crack. Moreover, the bulging portion of the ingot may slide across
the electromagnetic device and damage it.
It can readily be seen that the known device for electromagnetic
stirring is disadvantaged on account of two opposing constraints. A short
length dimension of the device is necessary to minimize the area of the in-
got not being supported by rolls of the track; a long extension of the de-
vice is needed to act on a significantly long ingot portion. These opposing
constraints are compounded by the fact that the supporting rollers must be
- 1 - ~
279
more closely spaced adjacent to those portions of the ingot which are still
predominantly or extensively liquidous. Downstream, more material has solid-
ified and the support rollers may be farther spaced. Stirrine, however, is
desired in the more liquidous portions, i.e. upstream from the portions that
require lesser support.
Description of the Invention
It is an object of the present invention to provide a new and im-
proved device for generating an electromagnetic field for stirring liquid
metal inside of a continuous casting, which device does not interfere with
the support function of the roller track, but permits stirring over a great-
er length in the casting.
Summary of the Invention
In accordance with the invention, there is provided apparatus for
electromagnetically stirring liquid metal in a solidifying continuous cast-
ing being withdrawn from a mold by means of a roller track comprised of
spaced rollers, comprising: a common yoke having a plurality of electro-
magnetic pole defining legs for carrying coils and mounted so that the legs
each extend between adjacent pairs of the rolls of the track; and an anti-
magnetic hood confining the yoke and said adjacent pairs of rolls.
In a preferred embodiment, the legs are provided with a cooling
jacket and are made of antimagnetic material. In a further preferred embod-
iment, the apparatus includes means for adjustably mounting the yoke to ad-
just the distance of the legs from the ingot.
Description of the Drawings
In drawings which illustrate an embodiment of the invention, given
by way of example only,
- Figure 1 is a side view of a portion of a roller track for with-
drawing an ingot or casting and includes equipment in accordance with the
- 2 -
- `
`' -
Z79
preferred embodiment; and
Figure 2 is a view taken along line A-A in Figure 1.
Proceeding now to the detailed description of the drawings, the
Figures show an upper roller track portion which includes rolls or rollers
2, 2', and a lower track 10. The two track portions are provided for moving
and supporting an ingot or casting 11. The rolls are spaced from each other
in the direction of movement, commensurate with their supporting function.
Rolls are spaced and have dimensions (in millimeters) in accord-
ance with the following table.
Support length Roll SpacingRoll Resulting
% (axis-to-axis)Diameter Gap
.
240 200 40
290 240 50
330 290 60
360 310 50
10 40 400 450 5o
The Figures show a track portion in the narrower gap region, but
the track portions related and covered have uniform gap width.
The stirring equipment includes an E-shaped yoke 1 having three
poles R, S, T, commensurate with the usual three phase designation. The
coils on each pole (not shown) are connected to a three phase electrical
power supply system. The poles, carrying the usual coils, are sufficiently
narrow to fit in between respective two adjacent rolls, whereby particularly
the two rolls 2' are straddled by yoke structure. Each pole includes a cool-
ing jacket 3.
Reference numeral 14 refers to a portion of the frame and stand of
the casting machine and the roller track, and this frame supports hydraulic
drives 4 to which the core or yoke 1 is mounted. Particularly, the hydrau-
-- 3 --
li~zqg
lic drives place the yoke into operating position and remove it therefrom.
Additionally, the yoke 1 may be laterally positioned as indicated by the
double arrow in Figure 2.
The operating position is defined by a particular distance "x" be-
tween the cooling ~acket 3 at the respective end face of the poles and the
surface of the casting. Typically, that distance x is about 3 cm. Also,
the yoke is to have normally a central lateral position between the rolls.
All of the particular rolls, having a position adjacent to the
yoke structure (2, 2'), are made of antimagnetic steel to prevent field short
circuiting which would bypass the steel in the ingot. The particular four
rolls facing yoke parts are confined in a hood 5, which is also made of anti-
magnetic steel, to avoid interference with the electromagnetic stirring
field.
Figure 2 shows additionally (dotted lines) that the poles can be
laterally offset. One will also see that preferably the stirring device is
arranged at a portion of the track having the same roller gap width for at
least three gaps.
The inventive device is of such construction that bulging of the
ingot or casting 11 is prevented. The support is, in fact, not interfered
with at all. On the other hand, the electromagnetic device provides stir-
ring in a larger length of the ingot, covering an area which in the past re-
quired at least two conventional stirring devices.
The invention is not limited to the embodiments described above
but all changes and modifications thereof not constituting departures from
the spirit and scope of the invention are intended to be included.
