Title of Invention

PROCESS FOR ELECTROLYTIC COATING OF A STRAND CASTING MOULD

Abstract PROCESS FOR ELECTROLYTIC COATING OF A STRAND CASTING MOULD. Process for electrolytically coating a mould in which internal surfaces (4) thereof demarcate a mould (2) cavity (3) having a generally rectangular cross-sectional shape when viewed in an axial direction, comprising: positioning an electrode (7) in the mould cavity (3); whereby the electrode comprises an insoluble electrode having a same cross-sectional shape as the cross- sectional shape of the mould (2). sealing off the entire mould cavity (3) with a head piece and a base piece positioned externally to said mould cavity (3) with sealing elements (8, 9) on both front faces at the ends of the mould (2), whereby the head piece (5) and the base piece (6) each have at least one opening forming an intake and a discharge opening for introducing and discharging electrolyte (25), providing an electrical connection between the electrode (7) and the mould (2); pumping electrolyte (25) by a pump into the mould cavity and back to the pump (16), wherein the electrolyte (25) is a sole supply of coating material; providing a current between the electrode (7) and the mould cavity (3); and changing the current direction periodically, wherein the current-direction is changed intermittently to pulse deposit the coating material, and, Coating the mould cavity (3) over its entire length at one time with a substantially uniform thickness including the four corner regions of the mould cavity.
Full Text Process for electrolytic coating of a strand casting mould
The invention relates to a process for electrolytic coating
of a strand casting mould according to the
precharacterizing clause of claim 1.
Strand casting moulds are subject to a constant abrasive
wear during casting, so that the mould cavity and therefore
also the cross-section dimensions of the cast strands
become ever larger. After a certain number of working
cycles, the particular strand casting mould must therefore
be replaced by a new one or reworked.
Various methods for reworking the moulds for the purpose or
re-establishing the original geometry of the mould cavity
or the intended dimensions of the mould cavity are known.
Reworking can be carried out, for example, by explosion
forming of the mould on a mandrel. Not only is this method
relatively complicated, expensive and environment-
polluting, it also means a deformation of the external
shape of the mould, which in turn involves an enlargement
of a water gap present on the periphery of the mould and as
a result an adverse influence on the cooling of the mould.
Other known pressing processes for reshaping the moulds in
which the mould is first compressed from the outside and
the mould cavity is then brought to the original internal
dimensions by internal grinding or internal milling also
have the latter disadvantage.
Finally, it is known from EP-A-0 282 759 to bring the mould cavity of a strand casting mould back to the intended
dimensions by electrolytic coating of the internal surfaces
which demarcate the mould cavity. In this generic process,
the mould, which serves as the cathode, is immersed in an

electrolyte bath (Cu sulfate bath) together with a
perforated anode basket which is positioned in the mould
cavity and is filled with soluble copper pieces (cubes,
balls, discs). When a direct current is connected, the
copper is separated out of the electrolyte bath and
deposited on the mould surfaces, the copper separated out
of the electrolyte bath being replaced by the dissolved
anode copper. A relatively low current density, for
example of about 15 A/dm2, is achieved in this dipping
electrolytic process. From experience, in the case of
electrolytic dip-coating of mould cavities which are
usually polygonal in cross-section there is the risk that
the layer is of insufficient thickness in the corner
regions, that is to say the layer thickness is only about
1/4.to 1/10 of that in the other regions. This non-uniform
layer build-up can be only partly remedied with special
anode geometries. This means a further mechanical
reworking is necessary.
With the production of thick layers there is furthermore
the risk that corner bridges with enclosed cavities are
formed, as a result of which the mould becomes unusable. A
further disadvantage of electrolytic dip-coating is that
the external surfaces of the mould must be covered with a
material which is inert towards the electrolytic treatment.
The present invention is based on the object of proposing a
process of the abovementioned type with which the intended
dimensions of the mould cavity can be achieved or re-
achieved as simply as possible even in strand casting
moulds having a mould cavity of polygonal cross-section,
without problem zones arising in the corner regions of the
mould cavity. Furthermore, the strand casting moulds to be

coated should as far as possible remain unchanged in their
external dimensions.
This object is achieved according to the invention by a
process having the features of claim 1.
Preferred further embodiments of the invention form the
subject matter of the dependent claims.
With the process according to the invention, in which the
electrolyte flows in a hydrodynamically controllable manner
through the mould cavity of the strand casting mould which
forms the cathode, using an insoluble anode, the
electrolyte alone supplying the coating material, it is
possible to apply both a thin layer of the wear-resistant
material with dimensional accuracy, without reworking being
necessary, and a thick layer (with which at most minimal
reworking arises), since the layer build-up is uniform
without corner weaknesses. It is a considerable advantage
of the process according to the invention that during the
electrolytic coating only the internal surfaces of the
mould cavity come into contact with the electrolyte and the
external surfaces of the strand casting mould therefore do
not have to be covered. Furthermore, intermittent
anode/cathode pole reversal is also possible, with which a
pulsed deposition of the coating material can be achieved
and the coating influenced.
It is to be emphasized as a particular advantage that the
mechanical properties, such as, for example, the hardness,
and in particular also the structural formation of the
coating can be kept largely uniform over the entire region.
The coating can be achieved more rapidly than with the

conventional processes. Gristle formation on the coated
surfaces can also be largely prevented.
The invention is explained in more detail in the following
with the aid of the drawing.
In the drawing:
Fig. 1 shows a schematic diagram of the process according
to the invention.
Fig. 1 shows, in purely schematic form, a device 1 which is
envisaged for electrolytic coating of internal surfaces 4
which demarcate a mould cavity 3 of a strand casting
installation 2 with a wear-resistant coating material for
the purpose of achieving or re-achieving intended mould
cavity dimensions. The mould cavity 3 can have, for
example, a rectangular or square cross-section and can thus
be demarcated by 4 internal surfaces. However, the mould
could also be a mould having another mould cavity cross-
section (e.g. circular, polygonal, longitudinally angled)
or a so-called dog bone mould.
A head piece and a base piece 5, 6 which are joined to one
another via an anode 7 which extends through the mould
cavity 3 are assigned to the faces of the strand casting
mould 2. Sealing elements 8, 9 on the faces of the strand
casting mould 2 seal off the mould cavity 3. The anode 7
is also inserted in a sealing manner in the head piece and
base piece 5, 6, cf. seals 13, 14. Both the base piece 6
and the head piece 5 are provided with at least in each
case one, preferably with a number of openings 11 and 12
respectively (in fig. 1 in each case one opening 11, 12 is
indicated), which form intake and discharge openings for

introducing and discharging an electrolyte 25 envisaged for
the electrolytic coating into and out of the otherwise
tightly closed mould cavity 3, which forms a reactor space.
This is pumped from a reservoir container 15 with the aid
of a pump 16 in a hydrodynamically controllable manner into
the reactor space from the bottom through the base piece 6
and is fed with an overflow (without pressure) on the head
piece 5 back to the reservoir container 15 and to the pump
16. The coating material is metered into the electrolyte
25 as oxide from a container 18.
For the electrolytic coating, the strand casting mould 2,
as the cathode, and the anode 7 with the wings 7' indicated
can be connected to a direct current source 2 0 and thereby
form a direct current circuit. Either the sealing elements
8, 9 or the seals 13, 14 simultaneously have an
electrically insulating action. The anode matches in its
cross-section shape the cross-section shape of the mould
cavity 3. For polygonal mould cavities, corresponding
prismatic anodes are used. The anode is made in particular
from a platinum- or mixed ceramic-coated titanium material
or from lead. It can also be constructed as a multiple
anode. In principle, however, the coating material, such
as, for example, copper, nickel or chromium, can also be
contained in the anode, in which case it would be provided
in a solid or piece form.
The process according to the invention is suitable for
application of, for example, layers of copper, nickel or
chromium. The coating material is supplied by the
electrolyte 25 alone. The anode in itself is insoluble.
The anodes can be, for example, platinum-coated anodes of
titanium, anodes of Pb sheet, coated mixed ceramic and

other materials. Methanesulfonic acid, cyanide or sulfuric
acid electrolyte types can be used as the electrolytes.
Using these high-speed electrolytes, with intensive
agitation of the electrolyte a current density of 2 to
4 0 A/dm2 can be achieved. With an efficient hydrodynamic
control of the flow of the electrolyte through the reactor
space, it is possible to apply both a thin layer of the
wear-resistant material with dimensional accuracy, without
reworking being necessary, and a thick layer (with which at
most minimal reworking arises), since the layer build-up
takes place uniformly and without corner weaknesses. The
process according to the invention brings considerable
advantages in particular in coating with chromium, since
precisely in the case of chromium particularly severe
corner problems arise during conventional electrolytic
coating (layer 5 to 10 times thinner than on the surfaces)
and the chromium can be reworked only with grinding.
Pulsed deposition of the coating material can also be
achieved with the process according to the invention, in
which the electrolyte 25 alone supplies the coating
material, since in addition to the hydrodynamic control, an
intermittent anode/cathode pole reversal is possible and
can influence the coating.
A considerable advantage of the process according to the
invention is that during the electrolytic coating only the
internal surfaces of the mould cavity come into contact
with the electrolyte 25 and the external surfaces of the
strand casting mould therefore do not have to be covered.
The anode and/or the strand casting mould could in
principle be constructed rotatably about their longitudinal

axis, so that rotation during the coating and therefore an
improved coating could be rendered possible.
Before the coating, the strand casting mould 2 is cleaned
by a rinsing process, in particular a cascade rinsing,
which is not explained in more detail. It is integrated in
a closed system here for the coating and preferably for
this rinsing.
The strand casting mould is made from a metallic material
or composite material, such as copper, aluminium or nickel,
from a plastic or composite plastic or from a ceramic
material or other materials.
A rectifier device can furthermore be provided, by means of
which the current direction can be reversed for the purpose
of achieving a uniform layer application.
If copper is used as the coating material, a commercially
available copper oxide, in which the too high chlorine
content is reduced by means of a washing/dissolving
process, is furthermore used beforehand.
Alternatively, the strand casting mould 2 can be coated
only in certain regions or more thickly, i.e. with a larger
layer thickness, in these regions where a relatively higher
degree of wear occurs during operation, for example in the
region of the bath surface, where an additional wear occurs
in particular due to the covering material. An efficient
coating is thus achieved. Such a partial coating can be
achieved by partial covering of the anode or by insertion
of non-conducting screens or by similar measures.

During the coating operation, electromagnetic fields can be
generated by magnets, which are not shown in more detail,
through which the particles of the coating material can be
conducted and. led such that a layer of the same thickness
as in the other regions is deposited in certain regions,
preferably in the edge regions of the strand casting mould.
The invention is described adequately by the above
statements. It could of course also be illustrated in
other variants.

WE CLAIM
1. Process for electrolytically coating a mould in which internal surfaces (4)
thereof demarcate a mould (2) cavity (3) having a generally rectangular
cross-sectional shape when viewed in an axial direction, comprising:
a) positioning an electrode (7) in the mould cavity (3); whereby the
electrode comprises an insoluble electrode having a same cross-sectional
shape as the cross-sectional shape of the mould (2).
b) sealing off the entire mould cavity (3) with a head piece and a base piece
positioned externally to said mould cavity (3) with sealing elements (8, 9)
on both front faces at the ends of the mould (2), whereby the head piece
(5) and the base piece (6) each have at least one opening forming an
intake and a discharge opening for introducing and discharging electrolyte
(25),
c) providing an electrical connection between the electrode (7) and the
mould (2);
d) pumping electrolyte (25) by a pump into the mould cavity and back to the
pump (16), wherein the electrolyte (25) is a sole supply of coating
material;
e) providing a current between the electrode (7) and the mould cavity (3);
and
f) changing the current direction periodically, wherein the current-direction
is changed intermittently to pulse deposit the coating material, and,
g) Coating the mould cavity (3) over its entire length at one time with a
substantially uniform thickness including the four corner regions of the
mould cavity.

2. Process as claimed in claim 1, wherein copper, nickel or chromium is used as
the coating material and is in each case metered into the electrolyte (25) as
oxide.
3. Process as claimed in claim 1 or 2, wherein an electrolyte (25) containing
methanesulfonic acid, cyanide or sulfuric acid is used.

4. Process as claimed in one of claims 1 to 3, wherein the anode (7) used in
insoluble form, which can be also constructed as a multiple anode, is
constructed from a platinum- or mixed ceramic-coated titanium material or
from lead.
5. Process as claimed in one of claims 1 to 4, wherein the electrolyte (25) is
pumped by means of a pump (16) into a reactor space which is
surrounded by the internal surfaces (4) of the mould cavity (3) and is
closed off at the faces by a base piece and a head piece (6, 5), and is fed
from this back to the pump (16).
6. Process as claimed in one of claims 1-5, wherein the anode (7) and/or the
strand casting mould (2) are constructed rotatably around their longitudinal
axis, so that rotation during the coating is rendered possible.
7. Process as claimed in one of claims 1 to 6, wherein the strand casting
mould (2) is cleaned by a rinsing process, in particular a cascade rinsing,
before the coating.
8. Process as claimed in one of claims 1 to 7, wherein the strand casting
mould (2) is integrated in a closed system for the coating and preferably
for the rinsing.

9. Process as claimed in one of claims 1 to 8, wherein the strand casting
mould (2) is made from a metallic material or composite material, such as
copper, aluminium or nickel, from a plastic or composite plastic or from a
ceramic material or other materials.
10. Process as claimed in claim 1, wherein if copper is used, a commercially
available copper oxide in which the too high chlorine content is reduced by
means of a washing/dissolving process is used beforehand.
11. Process as claimed in one of claims 1 to 10, wherein the strand casting
mould (2) is coated only or more thickly in certain regions where a higher
wear occurs during operation.
12. Process as claimed in claim 1, wherein the coating material, such as, for
example, copper, nickel or chromium, is employed as the anode.

13. Process as claimed in one of claims 1 to 12, wherein during the coating
operation the particles of the coating material are conducted by
electromagnetic fields such that in certain regions, in particular in the edge
regions of the strand casting mould, a layer of the same thickness as in
the other regions is deposited.


ABSTRACT
PROCESS FOR ELECTROLYTIC COATING OF A STRAND CASTING MOULD.
Process for electrolytically coating a mould in which internal surfaces (4) thereof
demarcate a mould (2) cavity (3) having a generally rectangular cross-sectional
shape when viewed in an axial direction, comprising:
positioning an electrode (7) in the mould cavity (3); whereby the electrode
comprises an insoluble electrode having a same cross-sectional shape as the cross-
sectional shape of the mould (2).
sealing off the entire mould cavity (3) with a head piece and a base piece positioned
externally to said mould cavity (3) with sealing elements (8, 9) on both front faces
at the ends of the mould (2), whereby the head piece (5) and the base piece (6)
each have at least one opening forming an intake and a discharge opening for
introducing and discharging electrolyte (25),
providing an electrical connection between the electrode (7) and the mould (2);
pumping electrolyte (25) by a pump into the mould cavity and back to the pump
(16), wherein the electrolyte (25) is a sole supply of coating material;
providing a current between the electrode (7) and the mould cavity (3); and
changing the current direction periodically, wherein the current-direction is changed
intermittently to pulse deposit the coating material, and,
Coating the mould cavity (3) over its entire length at one time with a substantially
uniform thickness including the four corner regions of the mould cavity.

Documents:

1809-KOLNP-2004-(08-11-2011)-ABSTRACT.pdf

1809-KOLNP-2004-(08-11-2011)-AMANDED CLAIMS.pdf

1809-KOLNP-2004-(08-11-2011)-CORRESPONDENCE.pdf

1809-KOLNP-2004-(08-11-2011)-DESCRIPTION (COMPLETE).pdf

1809-KOLNP-2004-(08-11-2011)-DRAWINGS.pdf

1809-KOLNP-2004-(08-11-2011)-FORM 1.pdf

1809-KOLNP-2004-(08-11-2011)-FORM 2.pdf

1809-KOLNP-2004-(08-11-2011)-OTHERS.pdf

1809-KOLNP-2004-ABSTRACT 1.1.pdf

1809-kolnp-2004-abstract.pdf

1809-KOLNP-2004-AMANDED CLAIMS.pdf

1809-KOLNP-2004-AMANDED PAGES OF SPECIFICATION.pdf

1809-kolnp-2004-claims.pdf

1809-KOLNP-2004-CORRESPONDENCE 1.1.pdf

1809-kolnp-2004-correspondence.pdf

1809-KOLNP-2004-DESCRIPTION (COMPLETE) 1.1.pdf

1809-kolnp-2004-description (complete).pdf

1809-KOLNP-2004-DRAWINGS 1.1.pdf

1809-kolnp-2004-drawings.pdf

1809-KOLNP-2004-EXAMINATION REPORT REPLY RECIEVED.pdf

1809-KOLNP-2004-EXAMINATION REPORT.pdf

1809-KOLNP-2004-FORM 1-1.1.pdf

1809-kolnp-2004-form 1.pdf

1809-KOLNP-2004-FORM 18 1.1.pdf

1809-kolnp-2004-form 18.pdf

1809-KOLNP-2004-FORM 2-1.1.pdf

1809-kolnp-2004-form 2.pdf

1809-KOLNP-2004-FORM 26.pdf

1809-KOLNP-2004-FORM 3 1.3.pdf

1809-KOLNP-2004-FORM 3-1.1.pdf

1809-kolnp-2004-form 3.pdf

1809-KOLNP-2004-FORM 5 1.1.pdf

1809-kolnp-2004-form 5.pdf

1809-KOLNP-2004-GRANTED-ABSTRACT.pdf

1809-KOLNP-2004-GRANTED-CLAIMS.pdf

1809-KOLNP-2004-GRANTED-DESCRIPTION (COMPLETE).pdf

1809-KOLNP-2004-GRANTED-DRAWINGS.pdf

1809-KOLNP-2004-GRANTED-FORM 1.pdf

1809-KOLNP-2004-GRANTED-FORM 2.pdf

1809-KOLNP-2004-GRANTED-SPECIFICATION.pdf

1809-KOLNP-2004-OTHERS 1.1.pdf

1809-KOLNP-2004-OTHERS 1.2.pdf

1809-KOLNP-2004-PA.pdf

1809-KOLNP-2004-PETITION UNDER RULE 137.pdf

1809-KOLNP-2004-REPLY TO EXAMINATION REPORT.pdf

1809-kolnp-2004-specification.pdf

1809-kolnp-2004-translated copy of priority document.pdf


Patent Number 252719
Indian Patent Application Number 1809/KOLNP/2004
PG Journal Number 22/2012
Publication Date 01-Jun-2012
Grant Date 29-May-2012
Date of Filing 29-Nov-2004
Name of Patentee CONCAST AG
Applicant Address TODISTRASSE 9 CH-8027 ZURICH
Inventors:
# Inventor's Name Inventor's Address
1 STILLI, ADRIAN EICHENWEG 4, CH-8180 BULACH
PCT International Classification Number B22D 11/059
PCT International Application Number PCT/EP2003/05238
PCT International Filing date 2003-05-19
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 20020876/02 2002-05-27 Switzerland