CERAMIC LINED CHANNEL INDUCTOR
The present invention relates to channel inductors of
channel induction furnaces .
In particular, the present invention relates to
channel liners of channel inductors .
The present invention also relates to channel
inductor furnaces.
Channel induction furnaces are used in industries for
melting a metal (which term includes metal alloys) and
maintaining the metal in a molten state. For example,
channel induction furnaces are used in galvanising and
foundry industries for melting Zn-containing alloys and
Al-containing alloys, including Al/Zn-containing alloys,
and maintaining the alloys in a molten state.
A known channel induction furnace comprises (a) a
steel shell, (b) a lining of a refractory material, such
as an aluminosilicate, internally of the shell, (c) a pot
for containing a bath of molten metal that is defined by
the refractory-lined shell, and (d) one or more than one
channel inductor for heating metal that is connected to
the shell and in fluid communication with the pot via a
throat that extends through the refractory-lined shell to
an inlet in the channel inductor.
The channel inductor comprises (i) a steel shell,
(ii) a lining of a refractory material, such as an
aluminosilicate, (either castable or dry-vibratable
refractory) , (iii) a channel defined by the refractorylined
shell that forms a path for molten metal to flow
from the pot through the channel and back into the pot,
and (iv) an electromagnetic coil which generates an
electromagnetic field. The molten metal in the channel at
any given time becomes a secondary circuit of a
transformer and is heated and kept molten by currents
induced by the electromagnetic field. The channel
inductor is a bolt-on assembly on the shell. The
refractory material that forms the lining is selected to
accommodate a range of specific mechanical requirements ,
thermal insulation requirements, and resistance to
chemical attack by Al and/or Zn requirements. These
requirements are competing requirements to a certain
extent in the sense of needing different material
properties and hence the selection of the refractory
material tends to be a compromise.
Channel inductors have a limited life in Zncontaining
and Al-containing alloys and typically fail in
the following modes :
Cracking of the refractory material, particularly along
central planes of channel inductors , during heat-up ,
dry-out, or operation, and subsequent penetration of Zn
and/or Al metal or Zn vapours into the cracks which
extend the cracks , ultimately resulting in a metal leak
from the channel inductors .
· Additionally, in the case of Al-containing alloys, by
reduction of S1O 2 in the refractory material by Al,
thereby forming A I2O3 and Si, with an associated
reduction in the volume of the refractory material and
penetration and/or spalling of the refractory material.
Typically, the life of channel inductors in Al
containing alloys is 6-24 months and is one of the main
reasons for metal coating line shut-downs .
The above discussion is not intended to be a
statement of the common general knowledge in Australia and
elsewhere .
The present invention provides a channel inductor of
a channel induction furnace, the channel inductor
comprising a channel liner that defines a channel for a
molten metal to flow through the channel inductor, the
channel liner comprising an inlet and an outlet for the
molten metal and a flange for mounting the channel liner
to a refractory material lining of a pot of the channel
inductor furnace, and the channel liner being formed from
a ceramic material that is resistant to chemical attack by
the molten metal in the channel, whereby in use of the
channel induction furnace direct contact between the
molten metal and the channel inductor is limited to
contact with the channel liner (including the flange) only
and molten metal does not contact other parts of the
channel inductor .
The term "chemical attack" is understood herein to
mean thermodynamic reduction of refractory oxides (in this
case by contact with molten metal, such as Al, in the
furnace) or penetration of refractory by molten metal
(such as Zn or Al or Zn-Al alloy) or vapours (such as Zn) .
The above-described construction of the channel liner
makes it possible for different parts of the channel
inductor to be made from different materials, each of
which is selected to be optimum in terms of required
properties for that part of the channel inductor.
Specifically :
• The channel liner may be formed from a material that is
chemically resistant to attack by the molten metal (such
as Al and/or Zn containing alloys) in the pot.
Consequently, in the case of molten metal in the form of
Zn-containing and Al-containing alloys, there is reduced
risk of Zn vapour or Zn-containing or Al-containing
molten alloy penetration through the liner into the
refractory material that forms a support for the channel
liner. This is particularly the case in situations
where the liner is made as a single-piece unit.
· The refractory material that forms a channel liner
support of the channel inductor, which could be a
castable or dry-vibratable material, can be optimised
for thermal insulation material properties and
mechanical strength properties, such that the integrity
of the channel liner is not compromised during heat-up,
dry-out, or operation of the channel induction furnace.
The channel liner may be made as a single piece unit.
The channel liner may be any suitable shape.
The channel liner may be made from any suitable
material .
The channel liner may be an elongate unit with the
channel being in the shape of a single U ("single loop
inductor") . More particularly, the channel may comprise
two arms extending from a base of the channel, with a
molten metal inlet in an end of one arm of the channel and
a molten metal outlet in an end of the other arm of the
channel, whereby molten metal can flow through one arm to
the base and through the base to the other arm and along
the other arm.
The channel liner may be an elongate unit with the
channel being in the shape of a double U . More
particularly, the channel may comprise three arms
extending from a base of the channel that interconnects
the arms , with a molten metal inlet in an end of a central
arm of the channel and molten metal outlets in the ends of
the outer arms of the channel, whereby molten metal can
flow through the inner arm to the base and outwardly
through the base to the outer arms and along the outer
arms .
The channel liner may have a top wall, with the inlet
and the outlet (s) formed in the top wall, and with the
mounting flange extending outwardly from the top wall .
The channel liner may comprise a side wall that
extends from a perimeter of the top wall, with the
mounting flange extending outwardly from an upper edge of
the side wall. This arrangement defines a vestibule or a
forebay .
The channel liner may be made from any suitable
ceramic material in terms of chemical resistance to the
molten metal .
The channel inductor may comprise a support for the
channel liner, with the support comprising a refractory
material.
The refractory material of the channel liner support
may be selected to have optimal thermal insulation
material properties and mechanical strength properties for
the channel inductor.
The channel liner support may further comprise an
outer steel shell.
The present invention also provides a channel liner
for a channel inductor that defines a channel for a molten
metal to flow through the channel inductor, the channel
liner comprising an inlet and an outlet for the molten
metal and a flange for mounting the channel liner to a
refractory material lining of a pot of the channel
inductor furnace, and the channel liner being formed from
a ceramic material that is resistant to chemical attack by
the molten metal in the channel, whereby in use of the
channel induction furnace direct contact between the
molten metal and the channel inductor is limited to
contact with the channel liner (including the flange) only
and molten metal does not contact other parts of the
channel inductor .
The channel liner may be made as a single piece unit.
The channel liner may be any suitable shape.
The channel liner may be made from any suitable
material .
The channel liner may be an elongate unit with the
channel being in the form of a single U , with the channel
comprising two arms extending from a base of the channel,
and with a molten metal inlet in an end of one arm of the
channel and a molten metal outlet in an end of the other
arm of the channel, whereby molten metal can flow through
one arm to the base and through the base to the other arm
and along the other arm.
The channel liner may be an elongate unit with the
channel being in the form of a double U , with the channel
comprising three arms extending from a base of the channel
that interconnects the arms , and with a molten metal inlet
in an end of a central arm of the channel and molten metal
outlets in the ends of the outer arms of the channel,
whereby molten metal can flow through the inner arm to the
base and outwardly through the base to the outer arms and
along the outer arms .
The channel liner may have a top wall, with the inlet
and the outlet (s) being formed in the top wall, and with
the mounting flange extending outwardly from the top wall .
The channel liner may comprise a side wall that
extends from a perimeter of the top wall, with the
mounting flange extending outwardly from an upper edge
the side wall. This arrangement defines a vestibule or
forebay .
The channel liner may be made from any suitable
ceramic material in terms of chemical resistance to the
molten metal .
The present invention also provides a channel
inductor furnace that comprises :
(a) a steel shell,
(b) a lining of a refractory material internally
the shell ,
(c) a pot for containing a pool of molten metal that
is defined by the refractory-lined shell, and
(d) one or more than one of the above-described
channel inductor for heating a metal that is
connected to the shell and in fluid
communication with the pot via a throat that
extends through the shell and the refractory
lining to the inlet in the channel inductor.
The present invention is described further by way of
example with reference to the accompanying drawings , of
which :
Figure 1 is a vertical cross-section through one
embodiment of a channel inductor furnace in accordance
with the present invention that includes one embodiment of
a channel inductor in accordance with the present
invention ; and
Figure 2 is a vertical cross-section through one
embodiment of a channel inductor in accordance with the
present invention .
Figure 1 is a cross-section of the main components of
a channel inductor furnace 3 for pre-melting an Al/Zn
alloy for use in a metal coating line for steel strip. It
is noted that the present invention is not limited to this
end-use and may be used as part of any suitable channel
induction furnace and for any suitable end-use
application .
The channel inductor furnace 3 shown in Figure 1
comprises a pot defined by an outer steel shell 27 and an
inner lining 29 of a refractory material, such as an
aluminosilicate . In use, the pot contains a bath of Al/Zn
alloy. The furnace 3 also includes two channel inductors
31 that are connected to opposed side walls of the steel
shell 27 and are in fluid communication with the bath via
respective throats 33. In use, molten Al/Zn alloy flows
from the bath and into and through the channel inductors
31 and is heated by the channel inductors 31 .
The drawing of the channel inductor 33 in Figure 2 is
a vertical cross -section in order to show the components
of the inductor that are particularly relevant to the
present invention. In addition, in order to make these
components as clear as possible, the electromagnetic coil
of the inductor 33 is not included in the openings 1 in
the drawing.
The channel inductor 33 comprises :
(a) a channel liner, generally identified by the
numeral 5 , and
(b) a support for the channel liner.
The channel liner 5 is moulded from a material that
is a chemically resistant material with respect to molten
Al/Zn alloy and Zn vapour. The channel liner 5 is a
single piece elongate unit that defines the abovementioned
openings 1 and a double "U" shaped channel for
molten Al/Zn alloy to flow through the channel inductor.
The channel comprises a base and three parallel arms 9
extending from the base. The upper end of the central arm
of the channel is an inlet 15 for molten Al/Zn alloy and
the upper ends of the outer arms of the channel are
outlets 17 for molten Al/Zn alloy. The base of the
channel is defined by a base section 7 of the channel
liner 5 and the arms of the channel are defined by
upstanding sections 9 of the channel liner 5 . These
sections 7 , 9 are thin-walled, hollow sections. The
channel liner 5 has a top wall 11, and the inlet 15 and
the outlets 17 for molten Al/Zn alloy flow are formed in
the top wall 11. The channel liner 5 also comprises a
side wall 21 that extends around the perimeter of the top
wall 11 and a flange 19 that extends outwardly from the
side wall 21. The top wall 11 and the side wall 21 define
a vestibule or forebay. The flange 19 is provided to
mount the channel liner 5 to a refractory material lining
(not shown) that defines a pot throat (not shown) of a pot
(not shown) of the channel inductor furnace, whereby
direct contact between molten Al/Zn alloy and the channel
inductor is limited to contact with the channel liner 5
only.
The channel liner support comprises an outer steel
shell 23 and an inner lining 25 of a refractory material .
The refractory material fills the space between the shell
23 and the channel liner 5 . Because contact between
molten Al/Zn alloy and the channel inductor is confined to
contact with the channel liner 5 , the refractory material
can be selected from a refractory material that is optimal
for thermal insulation and mechanical strength for the
channel inductor and without taking into account chemical
resistance properties.
The above described channel inductor minimises
chemical attack and cracking as failure modes for the
channel inductor .
Many modifications may be made to the embodiment of
the present invention described above without departing
from the spirit and scope of the invention.
By way of example, the present invention is not
confined to the particular shape of the channel inductor 3
shown in the drawing.
By way of further example, the present invention is
not confined to a double "U" channel liner 5 and, by way
of example, also extends to single "U" channel liners 5 .
By way of further example, the present invention is
not confined to a channel liner 5 that is formed as a
single piece unit.

CLAIMS
1. A channel inductor of a channel induction furnace ,
the channel inductor comprising a channel liner that
defines a channel for a molten metal to flow through the
channel inductor, the channel liner comprising an inlet
and an outlet for the molten metal and a flange for
mounting the channel liner to a refractory material lining
of a pot of the channel inductor furnace, and the channel
liner being formed from a ceramic material that is
resistant to chemical attack by the molten metal in the
channel , whereby in use of the channel induction furnace
direct contact between the molten metal and the channel
inductor is limited to contact with the channel liner
(including the flange) only and molten metal does not
contact other parts of the channel inductor.
2 . The channel inductor defined in claim 1 wherein the
channel liner is an elongate unit with the channel being
in the form of a single U .
3 . The channel inductor defined in claim 1 wherein the
channel liner is an elongate unit with the channel being
in the form of a double U .
. The channel inductor defined in any one of the
preceding claims wherein the channel liner comprises a top
wall, with the inlet and the outlet (s) formed in the top
wall, and with the mounting flange extending outwardly
from the top wall .
5 . The channel inductor defined in claim 1 wherein the
channel liner comprises a side wall that extends from a
perimeter of the top wall, with the mounting flange
extending outwardly from an upper edge of the side wall,
thereby defining a vestibule or a forebay.
6 . The channel inductor defined in any one of the
preceding claims comprises a support for the channel
liner, with the support comprising a refractory material.
7. A channel liner for a channel inductor that defines a
channel for a molten metal to flow through the channel
inductor, the channel liner comprising an inlet and an
outlet for the molten metal and a flange for mounting the
channel liner to a refractory material lining of a pot of
the channel inductor furnace, and the channel liner being
formed from a ceramic material that is resistant to
chemical attack by the molten metal in the channel,
whereby in use of the channel induction furnace direct
contact between the molten metal and the channel inductor
is limited to contact with the channel liner (including
the flange) only and molten metal does not contact other
parts of the channel inductor.
8. A channel inductor furnace that comprises :
(a) a steel shell,
(b) a lining of a refractory material internally
the shell ,
(C) pot for containing a pool of molten metal that
s defined by the refractory-lined shell, and
( ) one or more than one of the channel inductor for
heating a metal defined in any one of the
preceding claims that is connected to the shell
and in fluid communication with the pot via a
throat that extends through the shell and the
refractory lining to the inlet in the channel
inductor .