DEVICE FOR CASTING STRANDS OF METAL

DISPOSITIF CONCU POUR COULER DES BARRES DE METAL

English Abstract

The invention is directed to a device for casting strands of metal, in
particular steel,
with a material supply vessel, the liquid metal being delivered to the
carrying side of a
circulating conveyor belt by means of the pouring nozzle of the material
supply vessel. The
conveyor belt comprises a thin, heat-resistant belt which circulates between a
first deflection
roller and a second deflection roller and which is shaped after the first
deflection roller and in
the region of the outlet nozzle to form a trough for receiving the liquid
metal and resumes the
shape of a flat belt in proximity to the second deflection roller. In order to
reduce stresses on
the belt, it is proposed that at least one of the deflection rollers is
cambered in a convex
manner.

French Abstract

La présente invention concerne un dispositif conçu pour couler des barres de métal, notamment d'acier, lequel dispositif comprend un récipient d'alimentation en matière qui permet, par le biais de sa buse de coulée, de charger le métal fluide sur le brin supérieur d'une bande transporteuse en circulation. La bande transporteuse est composée d'une bande mince résistante à la chaleur qui circule entre une première poulie de renvoi et une seconde poulie de renvoi, laquelle bande est façonnée en forme d'auge après la première poulie de renvoi et dans la région de la buse de sortie afin de recevoir le métal fluide et reprend la forme d'une bande plane à proximité de la seconde poulie de renvoi. Afin de réduire les contraintes sur la bande, au moins une des poulies de renvoi est bombée de manière convexe.

Claims

-5-
CLAIMS:


1. A device for casting strands of metal, the device comprising:

an outlet nozzle configured to supply liquid metal from a material supply
vessel;

a circulating conveyor belt assembly being configured to receive the
liquid metal from the outlet nozzle on a carrying side, the conveyer belt
assembly
comprising: a first deflection roller; a second deflection roller; and

a thin, heat-resistant belt that circulates between the first deflection
roller and the second deflection roller, the belt being comprised of a belt
material and
being shaped to form a trough having a trough profile for receiving the liquid
metal
between the first deflection roller and the second deflection roller in a
region of the
outlet nozzle, the circulating conveyor belt resuming the shape of a flat belt
proximate
to the second deflection roller,

wherein at least one of the first deflection roller and the second
deflection roller is convexly cambered to form a camber, and wherein the
camber is
configured to at least partially compensate for a shortening of the belt
resulting from
the formation of the trough profile.

2. The device according to claim 1, wherein the camber resulting from the
trough profile is calculated according to the following formula:

(1) B B/2 = X B + X+ X T

(2) .DELTA.L XB = L - L V = .sqroot. L2 + X2 + Y2



-6-
wherein

B B is a width of the belt

L is a length of a final trough profile between an entry and exit,

L V is a length of a space diagonal in longitudinal direction of the trough,
X is an X coordinate for calculating L V,

X B is a distance from point C,

X T is a distance from a center of the belt or trough,
Y is a Y coordinate for calculating L V.

3. The device according to claim 1, wherein the change in length of the
belt due to varying temperature distribution over a width of the belt is taken
into
account in the camber and is calculated according to the following formula:

(3) .DELTA.1 Temp = L Trough .alpha. (T M = T R)
wherein

L Trough is a length of the trough,

T M is a temperature in a center of the belt

T R is a temperature at an edge area of the belt, and
.alpha. is a coefficient of expansion of a belt material.

4. The device according to claim 3, wherein the camber of the deflection
rollers for a homogenized tensile stress over the width of the belt is
calculated for a
given trough profile and temperature profile by superposition.




-7-

5. The device according to any one of claims 1 to 4, wherein the camber
of the first deflection roller is smaller than that of the second deflection
roller.

6. The device according to any one of claims 1 to 5, wherein the camber is
changeable by means of a pressure medium, in at least one of the deflection
rollers.
7. The device according to claim 6, wherein a profiled cavity is provided at
a roller shell for applying pressure.

8. The device according to any one of claims 1 to 7, wherein an entry
length and exit length, respectively, is greater than 500 mm.

9. The device according to any one of claims 1 to 8, wherein a maximum
entry length or exit length is selected in such a way that the camber due to
the trough
profile is not greater than 2%.

10. The device according to any one of claims 1 to 9, wherein the belt is
shaped by the deflection roller continuously over a distance to form the
trough profile
or flat belt.

11. The device according to any one of claims 1 to 10, wherein the belt
material comprises a thermal shock-resistant alloy based on CuNi, Fe.

12. Device according to any one of claims 1 to 11, wherein the belt material
comprises a single-phase or multiple-phase Cu alloy.

13. Device according to any one of claims 1 to 12, wherein the belt material
comprises a nickel-based alloy.

14. Device according to any one of claims 1 to 13, wherein the belt has a
thickness from 0.5 mm to 2.0 mm.

15. Device according to any one of claims 1 to 14, wherein the trough
profile is arc-shaped.


-8-

16. Device according to any one of claims 1 to 15, wherein the trough
profile is symmetrical.


17. Device according to any one of claims 1 to 16, wherein the trough
profile has substantially straight-line regions at both ends.


18. Device according to any one of claims 1 to 17, wherein the sides of the
trough profile are higher than a casting profile by 10 mm.


19. Device according to any one of claims 1 to 18, wherein side areas have
an angular deviation of +/- 25 degrees relative to the perpendicular.


20. Device according to any one of claims 1 to 19, wherein the trough
profile can be adapted to the shrinkage of the casting cross section by a
deliberate
adjustment of the rollers in casting direction over the length of the trough.

Description

CA 02677962 2011-10-11
20337-636

-1-
DEVICE FOR CASTING STRANDS OF METAL

The invention is directed to a device for casting strands of metal, in
particular steel,
with a material supply vessel, the liquid metal being delivered to the
carrying side of a
circulating conveyor belt by means of the pouring nozzle of the material
supply vessel,
wherein the conveyor belt comprises a thin, heat-resistant belt which
circulates between a
first deflection roller and a second deflection roller and which is shaped
after the first
deflection roller and in the region of the pouring nozzle to form a trough for
receiving the
liquid metal and resumes the shape of a flat belt in proximity to the second
deflection roller.

A device of the type mentioned above is known from Japanese Publication
59147755
A, in which the trough shape of the belt is achieved by means of vertical and
horizontal
conveying rollers which are arranged along the conveying path between the two
deflection
rollers and act on the belt.

Due to the relatively large differences in temperature along the width of the
belt
which act on the belt through the liquid-metal and because of the deformation
of the belt from
the flat shape to the trough shape and then back again into the flat belt
shape, there are widely
varying changes in length along the width of the belt resulting in critical
stresses on the belt
material, particularly in the edge area.

Although the belt - a steel belt is usually used for this purpose - has an
elasticity
corresponding to the belt material that is used, a cost-effective lifetime
cannot be achieved as
a result of the different stresses on the belt along the width.


CA 02677962 2011-10-11
20337-636

-1a-
Some embodiments of the invention may provide a device in which the
stresses on the belt are reduced and evened out. Further, new materials may be
used for the belt material because of the reduced, more uniform stress on the
belt.
Further, the entry length and exit length may be adapted to the geometry of
the
trough profile for specific adjustment of the degree of camber. This may
increase the
cost effectiveness of the casting process appreciably.

According to an aspect of the invention, at least one of the deflection
rollers is cambered in a convex manner.

According to another aspect of the invention, there is provided a device
for casting strands of metal, the device comprising: an outlet nozzle
configured to
supply liquid metal from a material supply vessel; a circulating conveyor belt
assembly being configured to receive the liquid metal from the outlet nozzle
on a
carrying side, the conveyer belt assembly comprising: a first deflection
roller; a
second deflection roller; and a thin, heat-resistant belt that circulates
between the first
deflection roller and the second deflection roller, the belt being comprised
of a belt
material and being shaped to form a trough having a trough profile for
receiving the
liquid metal between the first deflection roller and the second deflection
roller in a
region of the outlet nozzle, the circulating conveyor belt resuming the shape
of a flat
belt proximate to the second deflection roller, wherein at least one of the
first
deflection roller and the second deflection roller is convexly cambered to
form a
camber, and wherein the camber is configured to at least partially compensate
for a
shortening of the belt resulting from the formation of the trough profile.

Owing to a deliberate cambering of at least one of the deflection rollers,
by which the shortening of the belt resulting from the formation of the trough
profile is
at least partially


CA 02677962 2009-08-12
-2-
compensated and because the different temperature distribution along the width
of the belt is
also taken into consideration in the camber, the stress on the belt is made
homogeneous,
which has a positive impact on the life of the belt.

It is advantageous when the camber of at least one of the deflection rollers
can be
varied by a pressure medium to compensate for the change in length, e.g., due
to modified
casting parameters. To this end, a profiled cavity is provided in the roller
shell. In this
connection, it can also be advantageous when the camber of the first
deflection roller, for
example, is smaller than that of the second deflection roller.

The camber can be calculated based on the geometry of the trough profile. The
average trough profile is used for the calculation when the trough profile
varies over the
length of the trough to adapt to the shrinkage of the casting profile.

Details are shown in Figures 1 to 4.
The drawings show:

Figure 1 a schematic view of the belt with the deflection rollers in a side
view;
Figure 2 a cross section through the trough shape

Figure 3 the calculation model with a simplified trough shape as a rectangular
shape for the calculation and cambering of the deflection roller; and
Figure 4 the trough cross section for calculating the influence of
temperature.
The camber is a function of the respective belt length Le (entry length) and
La (exit
length) between the deflection roller and the trough profile or, conversely,
of the belt width
BB, trough width B-1, trough height HT and trough profile, where a rectangular
longitudinal
shape is assumed for purposes of the calculation.

The camber is yielded by: f(Le(a),BB,BI,Hi-, trough profile.

The calculation of the camber can be carried out for every point of the
deflection
roller between points A and B of the trough profile with coordinates X and Y
and length
Le(a) for half of the belt width BB between points C and D. The calculation of
the camber
must be carried out for the entry side and exit side.

The calculation of the different belt length owing to the varying temperature
distribution over the width of the belt can be carried out in a simplified
manner according to


CA 02677962 2009-08-12
-3-
the indicated formula. For an exact calculation, the temperature profile over
the width of the
belt is calculated corresponding to the casting parameters.

By means of the two formulas, the optimum camber of the deflection rollers for
homogenized tensile stress over the width of the belt can be calculated for a
given trough
profile (casting format) and temperature profile by superposition:

(1) BB/2 = XB+X+X'r

(2) ALXB=L-Lv = L2+X2+Y2
(3) Al temp = LTrougha (TM - TR

where BB is the width of the belt
Br- is the width of the trough
H 'r is the height of the trough
L is the length of the (final) trough profile between the entry and exit
Le is the entry length from the center of the first deflection roller to the
final
trough profile
La is the exit length from the final trough profile to the center of the
second
deflection roller
Lv is the length of the space diagonal in longitudinal direction of the trough
X is the X coordinate for calculating Lv
XB is the distance from point C
XT, is the distance from the center of the belt or trough
Y is the Y coordinate for calculating Lv
TM is the temperature in the center of the belt
TR is the temperature at the edge area of the belt
a is the coefficient of expansion of the belt material
(3 is the angular deviation from the vertical
Embodiments of the invention are indicated in the subclaims.

The camber of the first deflection roller is preferably smaller than that of
the second
deflection roller.

The camber should be changeable, e.g., by means of a pressure medium, in at
least
one of the deflection rollers. To this end, a profiled cavity can be provided
at the roller shell
for applying pressure.


CA 02677962 2009-08-12
-4-
The entry length and exit length, respectively, should preferably be greater
than 500
mm.

The maximum entry length or exit length is selected in such a way that the
camber
due to the trough profile is not greater than 2%.

The belt is preferably shaped by the deflection roller continuously over the
distance
Le(a) to form the trough profile or flat belt.

A particularly suitable belt material is a thermal shock-resistant alloy based
on CuNi,
Fe.

The belt material can be made of a single-phase or multiple-phase Cu alloy or
a
nickel-based alloy.

It should have a thickness from 0.5 mm to 2.0 mm.

The trough profile should have the shape of an arc and should preferably be
symmetrical.

Representative Drawing