U.S. patent application number 11/630633 was filed with the patent office on 2007-09-13 for stopper rod for delivering gas into a molten metal.
This patent application is currently assigned to Vesuvius Creucible Company. Invention is credited to Philippe Guillo.
Application Number | 20070210494 11/630633 |
Document ID | / |
Family ID | 34933070 |
Filed Date | 2007-09-13 |
United States Patent
Application |
20070210494 |
Kind Code |
A1 |
Guillo; Philippe |
September 13, 2007 |
Stopper Rod for Delivering Gas Into a Molten Metal
Abstract
The invention relates to a stopper rod adapted to deliver gas
during pouring of molten metal comprising a stopper body having an
internal chamber and a gas discharge port, a bore connecting the
internal chamber to the gas discharge port, the internal chamber
and the bore defining a gas passageway. According to the invention,
the walls of the gas passageway are provided with a layer of a
material which will not produce carbon monoxide at the temperature
of use. The stopper rod of the invention does not contaminate the
gas passing therethrough.
Inventors: |
Guillo; Philippe; (Paris,
FR) |
Correspondence
Address: |
VESUVIUS CRUCIBLE COMPANY
27 NOBLESTOWN RD
CARNEGIE
PA
15106-1632
US
|
Assignee: |
Vesuvius Creucible Company
103 Foulk Road, Suite 32
Wilmington
DE
19803
|
Family ID: |
34933070 |
Appl. No.: |
11/630633 |
Filed: |
July 15, 2005 |
PCT Filed: |
July 15, 2005 |
PCT NO: |
PCT/BE05/00116 |
371 Date: |
December 22, 2006 |
Current U.S.
Class: |
266/217 |
Current CPC
Class: |
B22D 41/186
20130101 |
Class at
Publication: |
266/217 |
International
Class: |
C21C 7/00 20060101
C21C007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 20, 2004 |
EE |
P04447179.5 |
Claims
1-9. (canceled)
10. A stopper rod adapted to deliver gas during pouring of molten
metal comprising a stopper body including walls defining a gas
passageway fluidly connected to a gas discharge port, the walls
comprising a layer that will not produce carbon monoxide at use
temperature.
11. The stopper rod of claim 10, wherein the layer comprises a
liner copressed with the body.
12. The stopper rod of claim 10, wherein the layer comprises a
coating applied on the walls of the gas passageway.
13. The stopper rod of claim 10, wherein the walls include a
thickness and the layer extends through essentially the thickness
of the walls.
14. The stopper rod of claim 1, wherein the layer extends beyond a
lowest point reached by a metal rod that attaches the stopper to a
rigging device.
15. The stopper rod of claim 1, wherein the layer comprises a
material selected from a group consisting of materials that do not
contain carbon; materials consisting essentially of non-reducible
refractory oxides; materials that react with carbon monoxide, and
mixtures thereof.
16. The stopper rod of claim 1, wherein the layer comprises 60-88
wt. % alumina, 10-20 wt. % graphite, and 2-10 wt. % silicon
carbide.
17. A stopper rod assembly adapted to deliver gas during pouring of
molten metal, the assembly comprising a stopper rod including a
stopper body and walls defining a gas passageway fluidly connected
to a gas discharge port, the walls comprising a layer that will not
produce carbon monoxide at use temperature; a metal rod attaching
the stopper rod to a rigging device, the metal rod extending into
the gas passageway beyond a highest point of the layer.
18. The assembly of claim 17, wherein a sealing gasket extends
around a lower end of the metal rod.
19. A stopper rod adapted to deliver gas during pouring of molten
metal comprising a stopper body having an internal chamber and a
gas discharge port, a bore fluidly connecting the internal chamber
to the gas discharge port, the internal chamber and the bore
defining a gas passageway including walls comprising a layer that
will not produce carbon monoxide at the temperature of use.
Description
[0001] This invention relates to a mono-block stopper rod used to
control the flow of molten metal from a discharge nozzle in a
holding vessel during metal teeming.
[0002] In continuous casting processes, the use of gases injected
down the stopper has been shown to have significant benefits on the
quality of metal being cast. For example, inert gases such as argon
or nitrogen can be injected to reduce the problems due to alumina
build-up and clogging or to assist in removing solidification
products from the vicinity of the discharge nozzle. Reactive gases
may also be employed when the melt composition needs modifying.
Conventionally, the stopper--generally made from an alumina carbon
refractory composition--is provided with an internal chamber
connected to gas supply means on the one end and to a gas discharge
port at the other end.
[0003] Various systems have been developed to ensure an accurately
measured flow of gas is supplied to the stopper. Problems have been
encountered with sealing such systems and ensuring that the gas
follows its intended path and is not wasted. Stoppers which have
proved to be successful in meeting many of these requirements are
disclosed in EP-A2-358,535, WO-A1-00/30785 and WO-A1-00/30786 and
more recently in WO-A1-02/100579.
[0004] Pursuing its development work in this field, the applicant
has now realized that the gas injected into the molten metal
through the stopper could be contaminated when passing through the
stopper.
[0005] In particular, it is suspected that the carbon present in
the composition constituting the stopper body could reduce some of
the metal oxides also present in the composition; this reduction is
accompanied by the generation of carbon monoxide. The carbon
monoxide injected into the molten metal will in turn oxidize the
aluminum which has been added to calm the steel producing thereby
important quantities of alumina contributing thus to the alumina
build-up and clogging.
[0006] It would therefore be advantageous to provide a stopper rod
which would not contaminate the gas passing therethrough.
[0007] According to the invention, this problem is solved for a
stopper rod adapted to deliver gas during pouring of molten metal
comprising a stopper body having an internal chamber and a gas
discharge port, a bore connecting the internal chamber to the gas
discharge port, the internal chamber and the bore defining a gas
passageway. According to the invention, the walls of the gas
passageway are provided with a layer of a material which will not
produce carbon monoxide at the temperature of use.
[0008] It must be noted that it is, to the applicant's knowledge,
the first time that it is proposed to provide a refractory article
with such a layer on a portion of said article that will never
contact the molten metal. On the contrary, in the prior art as
exemplified for example by the document U.S. Pat. No. 5,691,061 or
U.S. Pat. No. 5,681,499, such a layer is only provided on portions
that are always in contact with the metal.
[0009] The layer can be formed as a coating applied on the walls of
the gas passageway after the manufacture of the stopper rod. Such a
coating can be applied by spraying a liquid, wet or semi-wet
composition or simply by filling the inner chamber with the
appropriate composition. Once the coating is dried, the stopper rod
can then be cured. Alternatively, the curing of the stopper can
take place before the coating step. Advantageously, the layer is a
liner pressed simultaneously with the stopper rod body. In this
case, it is indeed possible to reduce the number of manufacturing
steps. According to another variant, the layer extends through
essentially the whole thickness of the walls of the gas
passageway.
[0010] The material constituting the a layer which will not produce
carbon monoxide at the temperature of use can be selected from
three different categories of materials:
a) materials which do not contain carbon;
b) materials essentially constituted of non reducible refractory
oxides; or
c) materials comprising elements which will react with the
generated carbon monoxide.
[0011] Preferably, the selected material will present two or three
of the above properties.
[0012] Examples of suitable material of the first category are
silica (for example vitreous silica), alumina, mullite or magnesia
based material (spinel). In certain cases, these materials can
however be somehow difficult to apply as a liner or coating (the
lack of carbon in the layer can cause some thermal shock problems)
and do not constitute the preferred embodiment of the
invention.
[0013] Suitable materials of the second category are for example
pure alumina carbon compositions. In particular, these compositions
should contain very low amount of silica or of conventional
impurities which are usually found in silica (sodium or potassium
oxide). In particular, the silica and its conventional impurities
should be kept under 2 wt. %, preferably under 1 wt. %.
[0014] Suitable materials of the third category comprises for
example free metal able to combine with carbon monoxide to form a
metal oxide and free carbon. Silicon and aluminum are suitable for
this application. These materials can also or alternatively
comprise carbides or nitrides able to react with carbon monoxide
(for example silicon or boron carbides).
[0015] Preferably the selected material will belong to the second
or third categories, even preferably, it will belong to the second
and third category.
[0016] A suitable material constituting the layer which will not
produce carbon monoxide at the temperature of use can comprise 60
to 88 wt. % of alumina, 10 to 20 wt. % graphite and 2 to 10 wt. %
of silicon carbide. Such a material is essentially constituted of
non-oxides species or non-reducible oxides and comprises silicon
carbide which can react with the carbon monoxide if some is
generated in working condition.
[0017] The invention will now be described with reference to the
attached drawing in which
[0018] FIG. 1 shows a cross-section of a stopper rod according to
the invention.
[0019] Reference 1 depicts respectively the internal chamber and a
gas discharge port of the stopper rod. A bore 3 connects the
internal chamber 1 to the gas discharge port 2. The bore 3 and the
internal chamber 1 define a passageway for the gas. FIG. 1
represents an embodiment wherein the layer 4 has been copressed as
a liner with the stopper body. Very conveniently, the liner 4 can
be constituted of several pre-formed tubular portions (41, 42, 43)
which are all copressed with the stopper body. A portion of the
metal rod 5 connecting the stopper rod to the rigging device (not
shown) is depicted in working position. Preferably, the metal rod 5
extends beyond the highest point of the layer 4. Even more
preferably, a sealing gasket 6 is inserted around the lower end of
the metal rod 5.
* * * * *