Note: Descriptions are shown in the official language in which they were submitted.
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4506-196
The present invention relates to making a mold for con~
tinuous casting using a tube made of copper or a copper alloy by
shaping the tube upon a mandrel having dimensions corresponding to
the dimensions of the mold to be macle, whereby the forming process
usually involves exertion of force upon the tube being thus press
worked onto the mandrel~ The mandrel of course has to be removed
subsequently.
German printed patent 1,809,633 proposes the manufacture
of a curved mold to be used in a machine for continuous casting
wherein the casting strand is run along a circular withdrawl path.
The method as proposed in this patent begins with a straight tube
into which a curved mandrel is forced having outer dimensions as
well as a shape which corresponds to the shape and dimensions of
the mold to be made. Subsequently the tube with the mandrel is
forced through a die so as to force the interior surface of the
tube into a tight contact, by press working onto the surface of
the mandrel. Subsequently the mandrel is forced out of the tube.
German printed patent application, laid open to the
public inspection on February 19, 1976 in the name of Concast Inc.,
2,533,528 proposes the utilization of a sizing mandrel wherein the
force by means of which the tubular blank is forced upon the
mandrel is produced by explosion of a particular charge. The so-
called explosion shaping has also been applied for improving the
quality of used molds; see for example German patent 2,425,573. In
all these instances of explosion shaping the mold walls are shaped
by discharge of an explosive forcing the wall of a blank or of
a mold upon the shaping and sizing mandrel which has been placed
into the interior of that tube. Independently from the manner of
applying the shaping force, emp oyment of a sizing and/or shaping
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4506-196
mandrel as a basic implement ensures that the interior walls and
surfaces of the mold thus made assume a high degree of accuracy;
moreover the interior surface of the mold has a very high quality.
Molds made or improved for example as described above are
used for example for continuous casting of steel. They have round,
rectangular or square shaped cross section. These are the basic
cross sections and further working has to use the thus shaped cast-
ing as a blank. For example, certain sections such as T or double
T, i.e. I sections, U or L sections may have to be made for
example by way of rolling. Clearly, a large number of rolling
steps is required in order to shape a simple cross sectional con-
tour (rectangle, circle, square) of a casting into a complex con-
tour for purposes of making the final product.
German printed patent application 1,282,861 which was
published on November 14, 1968 in the name of The British Iron and
Steel Research Association discloses molds for continuous casting
in which the interior shape deviates from a rectangular or cir-
cular configuration. Elowever, the mold here is a so-called parti-
tioned mold with variable wall thickness and has, therefore,
different cooling conditions for various portions of the casting.
Tubular molds for continuous casting with a cross section that
deviates from a rectangular or circular one but also having uniform
thickness of the wallS bounding the mold cavity are also known
through Zak-Fab "Welded Molds", Mold Bulletin Nr. 410 of November
21, 1968. However, as far as tubular molds are concerned these
welded mold configurations have not yet gained any significance
because, possibly, the quality does not always meet standard
requirements.
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4506-196
It is an object of the present invention to provide a
new and improved method for making or restoring tubular molds for
continuous casting having any kind of interior shape but including
also conventional
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rectangles, whereby, however high demands on the mold itself is made.
In accordance with the preferred embodiment of the present
invention it is suggested to apply a method for making or improving
molds for contimlous casting by forcing a tube or a mold made of copper
or a copper alloy upon a mandrel, having a contour and dimensions
corresponding to the mold to be made. The mandrel is of a shape other
than a rectangular or square or round cross section and is removed
subsequent to the process of shaping. The resulting product therefore
is a mold for continuous casting which at least approximates the shape
of the parts made by continuous casting and subsequent rolling and
other finishing and shaping process. Therefore the mold is made so that
casting is carried out by making a casting ingot having a cross section
which matches in a favourable manner the subsequent occurring of a
rolling process particularly towards minimizing material displacement
and reshaping corresponding to the desired quality of the final
e.g. steel product.
For example in the case of rail road track like rails to be
made the mold for continuous casting will have a double T like cross
section. A rail road track like rail can be made rather easily from such
a double T casting by way of rolling with little material displacement.
This means that the rolling process does not have to include a large
plurality of passes. Aside from these advantages the quality of the
product is improved simply by the minimizing of the amount of deformation
the casting is to experience by the subsequent rolling.
The invention therefore relates to molds of the so-called
profiled section type, i.e. profiles or cross sections that deviate from
rectangular, square shaped or circular round cross sections. A particular
advantageous filed of employment are envisioned with sections of the
double T, T, U, or L shape. It is essential for the invention to use a
suitable mandrel which is forced into the tubular blank or a previously
used mold to be refinished. This mandrel may for example have a conical
contour or a doubl~ conical contour in order to make sure that the conicity
that may be required for the mold is established in reality. The mandrel
can be straight or curved in order to match the mold more favourable to
the withdrawal path configuration for the ingot and casting beillg made.
In cases, undercut portions may be provided in the sizing mandrel.
After a tubular blank generally has been forced upon such a mandrel the
particular sizing of the interior space and its boundary is directly
established therewith. In order to make sure that the mandrel can
subsequently be forced out of the finished mold, it may be of advantage to
size the mold or the tube subsequently from the outside. The tube, i.e.
mold made by forcing the blank or the previously used tube onto the mandrel
may to some extent be outwardly deformed during removal of the sizing
mandrel. Subsequent reshaping of the mold from the outside can therefore
be used to restore the internal contour of the mold. Another possibility
for overcoming the problem of cross section modifications of undercut
sections occurring during removal of the mandrel, can be seen in providing
the mandrel in a bi - or multiple part manner, wherein the dividing line
or planes of partition run longitudinally, transversely or both with regard
to the axis of the product, i.e., of the mold to be made.
Decisive for the invention is the utilization of a sizing mandrel
for making a non-round, non-square shaped, and non-rectangular mold for
continuous casting under exertion of force from the outside. This force
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can be produced in -various ways. As it is known for example for making
rectangular molds, the mandrel where carrying the mold may be forced
through an appropriately shaped die. Alternatively explosion shaping can
also be used. Still alternatively, the force for sizing may be exerted
through drop forging; rolling; or hydrostatic pressure.
A completely new method of making a mold or improving the quality
thereof is the so-called electro hydraulical shaping. Herein energy is
provided by means of an electric arc acting in the pressure medium, such
as water, and the resulting shock wave is transferred through the water
upon the part to be made. The requisite electrical energy is provided
by a pulse source.
A method for shaping work pieces through particular application
of energy is the so-called electro magnetic shaping. This method uses
the electrical energy stored in a capacitor and being discharged through a coil.
The coil is arranged around the mandrel and tube configuration. The
current flowing through this coil produces a magnetic field which induces
an opposing current in the mold wall. The magnetic field exerts a force
upon the tube which forces that tube or blank onto the surface of the
mandrel. By means of so-called field shapers one can control the spatial
distribution of force and, therefore, the pressure distribution as it is
effective on the mold wall being made. The last two particular tube methods
just mentioned are suitable for making molds of any cross section, including
complex cross sections, as we]l as rectangular or round sections.
For practicing the invention, one can begin with any kind of
initial shape, because after insertion of the sizing mandrel and upon
appropri~te distribution of the exerted forces the blank is forced to adapt
to the dimensions of the mandrel whatever its shape. In cases however it may
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be of advantage to use already near T shaped blanks or near double T blanks
or U or L shaped blanks, as far as the respective cross section is concerned,
and the appropriately contoured mandrel is then inserted into the interior
of such a tube.
By way of example these initial blank sections may be made for
example by means of extrusion of the copper or copper alloy in order to
obtain a blank at a suitable contour into which the mandrel with the final
shape is subsequently inserted. The shaping with the aid of additional
mandrel could therefore be limited to about a 15 to 25~ cross sectional
modification as compared with the initial cross section made through an
extrusion process. This particular and relatively low degree of shaping
improves the quality of the mold, for example, by increasing the so-called
Brinell hardness.
A profiled blank within the meaning established here may
alternatively be made from an initially extruded round or ovally shaped
tube which is subjected subsequently to drawing or rolling to obtain the
overall outline of the final shape, and the finislling work is then carried
out in accordance with the invention through insertion of the appropriately
contoured mandrel.
It was mentioned above with reference to the prior art that certain
tubular molds are known to have been made of welded sheets. Beginning
with this kind of state of the art one may use the welding technique for
making T, double T, U, or L shaped molds in form of blanks, and subsequently
these blanks are then reshaped in accordance with the method of the
invention. Moreover, welded molds made and deemed completed as per the
state of the art may be further improved by practicing the invention, namely
through the insertion oE a mandrel and exerting force from the outside to
thereby obtain a considerable improvement in quality and surface finish.
While the specification concludes with claims particularly
pointing out and distinctly claiming the subject matter which is regarded
as the invention, it is believed that the invention, the objects and features
of the invention, and further objects, features and advantages thereof will be
better understood from the following description taken in connection with
the accompanying drawings in which:
Figure 1 is a perspective view illustrating a copper blank from
which a mold is to be made;
Figure Z is a perspective view of the blank of Figure 1 subsequent to
a preliminary operation having been carried out;
Figures 3 through 3d are perspective views showing five different
alternative mandrels;
Figure 4 is a perspective view showing a mandrel being inserted into
the blank of Figure 2; and
Figure 5 is a perspective view of the finished mold.
Proceeding now to the detailed description of the drawings,
Figure 1 illustrates a blank in the form of a straight copper pipe or tube with
a Brinell hardness of about l-IB50 to 60. This copper pipe 1 was made
originally by extrusion, possibly followed by drawing. This more or less
endless extruded tube is then cut into length to the desired mold length.
In accordance with the next process and working step, the tube or
tubular blank 1 made and as shown in Figure 1 is subsequently drawn by
means of an appropriately contoured die and appropriately contoured mandrel,
or it may be rolled by means of appropriately contoured roll. The end
result here is the particular produc-t 2 shown in Figure 2. This is a kind of
distorted rectangle and cons-titutes the blank for subsequent working. In
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particular this blank shown in Figure 2 has to come extent a con-tour which
approximates the final contour that is desired, namely a double T cross
section. This blank 2 must now be brought into the final shape.
To obtain the final mold shape one needs a mandrel 3 as shown in
Figure 3. This mandrel 3 is hard and chromium plated and it is provided
with a double T shape cross section. Tlle cross section therefore will
resemble the cross section of the product (e.g. a steel rail) that is
later being made by continuous casting. As shown in Figure 4 this mandrel
3 is forced into the blank 2. There is of course a deviation of cross
section between the internal outlining of blank 2 and the outer contour
of mandrel 3. This may necessitate forcing the mandrel 3 into the blank 2.
Subsequently and through some exertion of force from the outside
blank 2 is brought into intimate, surface to surface contact with the
entire periphery of the mandrel 3 requiring of course a sufficient amount of
force and sufficiently oriented and directed application of force. This
forcing of the blank 2 into intimate contact with the mandrel 3 may for
example be carried out by means of a pressure die-like element so as to
force the blank 2 into intimate contact with the entire periphery of the
mandrel 3. The presently considered final shaping process of the copper
blank 2 is basically a cold working process and it was found that the si~e
and dimensions thus obtained of the final product 4, are extremely accurate.
Following th;s working step the mandrel is removed from the
blank 2 which in fact has now the shape and contour of the final product
namely the mold 4 as depicted separately in Figure 5. The Brinell hardness
is increased by this procedure to about 80 to 120 HB.
Instead of described above the shaping of the blank 2 onto the
mandrel 3 may be carried out differently. For example one can use the
earlier described method of discharging an e~plosive; alternatively the
blank may assume final shape 5 by means of drop forging or rolling iTI
which case mandrel and blank are run through one or several working stages
in step like fashion.
Another possibility of forcing the blank tightly onto the mandrel
is to be seen in sizing througll electrical discharge or by means of a
magnetic field or by means of hydrostatic pressure.
the particular blank 1 could also be made through welding from
metal sheets or an earlier made mold such as 4 may have been made by welding
together metal sheets. In any event the mold may be subjected subsequently
to the steps as described with reference to Figure 4.
The mandrel 3 to be used may be curved as shown in Figure 3a so
as to match the mold to be produced to a circularly shaped casting withdrawal
path of the machine for continuous casting in whic}l the mold is going to be
used. Also the mandrel 3 may fully or partially be provided with a
conical or tapered contour from one end to the other. Upon forcing such a
tapered mandrel into a straight blank a certain preshaping is obtained
therewith. Of course the blank may be provided in curved configuration
already prior to mandrel insertion.
The examples demonstrate and illustrate the manufacture of a mold
or a quality improvement of the mold particularly with regard to cross
sections in the double T contour. Other sections and type of cross sections
can be made, for e~ample, T, L or U shaped cross sections. The respective
mandrels are shown in Figures 3b, 3c and 3d and have to be appropriately
contoured. The preshaped blanks may respectively match, in an overall
geometric sense but with larger cross-section, the particular blank so as to
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limit the degree of plastic deformation which the blank must undergo when
shaped on the mandrel into a mold.
lndependently from the section and cross section envisioned
here, the invention guarantees high quality tubular molds with uniform wall
thickness and therefore a better and more uniform cooling process during
operation oE the mold than was heretofore possible with known molds.
Herein is decisive that the mandrels are in fact shaped corresponding to the
desired mold and casting cross section. The par-ticular geometrically
corresponding blank is then placed on the mandrel and shaped
thereon whereby particularly the deforming forces act upon the blank from
all sides, including particularly the edge portions. During shaping by
means of a pressure ring or a die or by means of rolls one needs tooling
whose operating surfaces match the contour to be made.
The figures (except Figure 3a) illustrate the blank, the mandrel
and/or the completed mold in a straight configuration. The straight
configuration was chosen for purposes of illustration and particularly for
purposes of facili-tating description of the invention. Ilowever the
invention is not to be limited to straight molds. Particularly one will
use generally a curved sizing mandrel such as shown for a double T contour
in Figure 3a because most continuous casting machines for steel are provided
with a curved i.e. circularly curved withdrawal path so that the mold
itself is matched to the curve. A curved mandrel with the cross section
of a T, double T, U, or 1. will then analogously either be forced into a
precurved blank or the blank remains straight until being forced to undergo
curving as a mandrel is forced into it. The same is true of course with
regard to operations involving the mandrel shown in Figure 3a.
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