Note: Descriptions are shown in the official language in which they were submitted.
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METAL MAKING LANCE TIP ASSEMBLY
CROSS REFERENCE TO RELATED APPLICATION
The present application claims the benefit of U.S.
Provisional Patent Application No. 60/794,258, filed April
21, 2006, which is incorporated herein by reference in its
entirety_
FIELD OF THE INVENTION
The present invention relates in general to metal
making equipment and in particular to metal making lances.
BACKGROUND OF THE INVENTION
In many metal making processes, water-cooled lances are
inserted into a furnace vessel to perform desired metal
processing functions. For instance, in steelmaking processes
a water-cooled lance is inserted into a steelmaking vessel
(e.g., a basic oxygen furnace (BOF), electric arc furnace
(EAF), etc.), to promote melting, decarburization, refining
and other processes useful in converting iron-containing
scrap material within the vessel into steel. A typical lance
may inject gaseous materials such as oxygen, hydrocarbon gas
and/or inert gas at high velocity at various times to
achieve desired treatment of the charged material (scrap and
hot metal) and/or maintenance of the interior of the vessel.
Some lances may also inject particulate carbon'and/or lime
(or other. substances) to achieve desired properties in the
steel ultimately produced.
Water-cooled lances generally comprise an adapter
portion, an elongated barrel portion connected at a first
end thereof to the adapter portion and a lance tip portion
connected to a second end of the barrel portion.
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The adapter portion comprises at least one inlet for
receiving the gaseous and/or particulate matter to be
injected into the furnace vessel, which matter will
hereinafter be generally referred to as "active material."
The adapter portion also includes a water inlet and a water
outlet for circulating pressurized cooling water throughout
the lance.
The barrel portion comprises at least three
substantially concentrically arranged metal, typically
steel, pipes for communicating the cooling water and/or
active material(s) between the adapter portion and the lance
tip portion. The outermost and first innermost pipes
normally define an annular water return passageway for
conveying coolant water from the lance tip portion to the
adapter portion. The first and second innermost pipes
normally define an annular water delivery passageway for
conveying coolant water to the lance tip portion from the
adapter portion. And, the interior of the second innermost
pipe (and any additional pipes arranged interiorly thereof)
defines at least one passageway for conveying active
material from the adapter portion to the lance tip for
injection into the furnace vessel.
The lance tip portion usually comprises an assembly
having one or more parts which may be secured by welding,
soldering or the like to the concentric pipes of the barrel
portion. The lance tip assembly comprises at least one
nozzle in communication with the at least one active
material passageway of the barrel portion for injecting or
discharging the active material into the furnace vessel. The
tip assembly further comprises passage means for connecting
the water delivery and return passageways of the barrel
portion to one another. So constructed, water or other
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coolant fluid may be continuously circulated through the
lance to cool the lance, especially the lance tip assembly
which is exposed to the greatest temperatures during lance
operation. Indeed, if coolant water is not effectively
conveyed through the lance tip portion then the assembly may
become non-uniformly heated. This, in turn, may lead to so-
called "hot-spots" or "burn-through" sites which often
result in premature failure of the lance tip.
A common practice by which the steelmaking lance
manufacturing industry has sought to impart cooling to the
lance tip assembly is to provide a generally centrally
disposed protrusion or dimple at the inner surface of the
tip face member of the tip assembly. The object of such
protrusion is to direct coolant water radially outwardly
through the interior space of the lance tip to cool all
areas of the outer working surface face of the lance tip.
The water-diverting protrusions have assumed an assortment
of sizes and shapes and have met with varying degrees of
success for their intended purposes. Examples of such
protrusions may be found in U.S. Pat. Nos. 3,224,749;
3,525,508; 3,525,509; 3,823,929; 3,827,632; 4,083,539;
4,083,541; 4,083,542; 4,083,543; 4,083,544; 4,106,756;
4,322,033; 4,432,534; 4,702,462; 4,951,928; 6,234,406 and
U.S. Reissue Pat. No. 28,769, as well as United Kingdom Pat.
Nos. 1,190,137 and 1,255,082.
U.S Patent No. 4,417,721 proposes an alternative means
for improving coolant water flow across the inner surface of
a lance tip. In particular, a plurality of intricately
configured radial water flow passages are provided between a
lower surface of a coolant water baffle member and the inner
surface of the lance tip face member. The radial flow
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passages are defined by and located between flow vanes of
uniform thickness.
U.S. Patent Nos. 3,322,419 and 3,337,203 and United
Kingdom Pat. No. 1,255,082 combine a centrally disposed
protrusion and a plurality of radially arranged coolant flow
vanes at the inner surface of the lance tip face member.
However, in each of these designs the vanes do not extend
either (1) essentially the entire axial distance or height
between the inner surface of the lance tip face member and
the lower surface of a coolant flow baffle member or (2)
essentially the entire radial distance from the central
protrusion to the annular coolant fluid return passageway.
The considerable radial or axial coolant flow gaps in these
designs permit cross flow between adjacent coolant flow
passages at the inner surface of the lance tip face member.
It is believed that such cross flow produces eddy currents
and dead spaces in coolant water flow which could result in
the formation of hot spots at the outer working surface of
the lance tip face member.
An advantage exists, therefore, for a metal making
lance tip assembly which is comparatively easy to assemble
and durable in operation and which provides substantially
uniform cooling of the working face of the lance tip via
structural features that promote high coolant water flow and
velocity throughout the tip.
A further advantage exists for a metal making lance tip
assembly having a structurally reinforced face for improved
operating performance and service life.
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SUMMARY OF THE..INVENTION
The present invention provides a lance tip assembly for
a water-cooled lance. In general, the assembly includes a
tip face member having a plurality of outlets, a plurality
of nozzles corresponding in number and in communication with
the tip face member outlets and with a corresponding number
of inlets provided in an active material well member, a
coolant baffle member for directing coolant flow around the
nozzles, and a tip face member support post connecting the
tip face member and the active material well member for
providing structural support to the tip face member during
lance operation.
Unlike other lance tip assemblies, the lance tip
assembly of the present invention further includes both a
generally centrally disposed coolant fluid diverting
protrusion and a plurality of radial vanes at the inner
surface of the tip face member, which vanes extend
essentially the entire axial distance between the inner
surface of the lance tip face member and the lower surface
of the coolant fluid flow baffle member and essentially the
entire radial distance from the central protrusion to the
annular coolant fluid return passageway. The resultant
construction provides high velocity and essentially eddy and
void free coolant fluid flow across the inner surface of the
lance tip face member which, in turn, uniformly cools the
lance tip face member and greatly enhances the service life
of the lance tip assembly.
Other details, objects and advantages of the present
invention will become apparent as the following description
of the presently preferred embodiments and presently
preferred methods of practicing the invention proceeds.
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BRIEF DESCRIPTION OF THE DRAWINGS
The invention will become more readily apparent from
the following description of preferred embodiments thereof
shown, by way of example only, in the accompanying drawings
wherein:
FIG. 1 is an elevational cross-section view of a lance
tip assembly according to the present invention taken along
line I-I of FIG. 2;
FIG. 2 is a view the working face of the lance tip
assembly of FIG. 1;
FIG. 3 is an elevational cross-section view of the
lance tip assembly shown attached to the lower end of the
barrel portion of a metal making lance;
FIG. 4 is a plan view of the inner surface of the tip
face member of the lance tip assembly;
FIG. 5 is an elevational cross-section view of the tip
face member taken along line V-V of FIG. 4;
FIG. 6 is an elevational cross-section view of the tip
face member taken along line VI-VI of FIG. 5 and
illustrating a preferred cooling reinforcement ratio for
coolant vanes constructed according to the present
invention; and
FIG. 7 is an elevational cross-section view of a
central portion of the tip face member according to the
present invention illustrating a preferred dimple profile
ratio for a central recess provided therein.
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DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings wherein like or similar
references indicate like or similar elements throughout the
several views, there is shown FIGS. 1-3, collectively, a
metal making lance tip assembly according to the present
invention which is identified generally by reference numeral
10. Assembly 10 preferably comprises: a tip face member 12
having a plurality of outlets 14, a plurality of outwardly
divergent nozzles 16 corresponding in number and in
communication with the tip face member outlets 14 and with a
corresponding number of inlets 18 provided in an active
material well member 20, a coolant baffle member 22 for
directing coolant flow around the nozzles 16, and a tip face
member support post 24 connecting the tip face member 12 and
the active material well member 20 for providing structural
support to the tip face member during lance operation. The
illustrated example in FIG. 2 depicts four nozzles
equiangularly disposed about the central longitudinal axis
26 of assembly 10. However, any desired number of nozzles in
any desired orientation may be provided in the assembly. As
is known, nozzles 16 permit gaseous and/or particulate
active material to pass from an active material flow space,
described below, through corresponding outlets 14 and into a
unillustrated furnace vessel such as, for example, a
steelmaking vessel.
An exemplary, although not limitative, procedure for
assembling lance tip assembly 10 is as follows. The various
components of assembly 10 may be formed of metal or metal
alloys including, without limitation, copper, brass, steel,
stainless steel and the like, as may be appropriate for the
intended function(s) or desired characteristic(s) of the
components (e.g., structural strength, thermal conductivity,
etc.). One end of support post 24 is welded to the uppermost
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portion of a centrally located protrusion 28 provided on
inner surface 30 of tip face member 12. Protrusion 28 is
described in detail in connection with the discussion of
FIG. 5. Tip face member is desirably made of highly
thermally conductive metal such as, for example, solid cast
or forged copper or brass. Thereafter, the tip face member
12 and nozzles 16 are cleaned and prepared for brazing,
including cutting and inserting unillustrated brazing rings
into the lower ends of the nozzles. The coolant fluid baffle
member 22 is then placed into mating recesses, described
hereinafter, provided on radially extending coolant flow
directing vanes 32 that extend upwardly from the inner
surface 30 of tip face member 12. Nozzles 16 are then
inserted into corresponding openings in coolant baffle
member 22 in alignment with tip face member outlets 14.
Lastly, the active material well member 20 is placed atop
the upper ends of nozzles such that its inlets 18 are in
alignment with the upper ends of nozzles 16. The assembly is
then clamped together, the lower ends of the nozzles are
brazed to upper ends of the outlets of the tip face member,
the coolant fluid baffle member is welded to the nozzles,
the upper ends of the nozzles are welded the inlets of the
active material well member, and the upper end of the
support post is welded to the active material well member.
Although shown and described as separate components
assembled into a collective whole, it is also contemplated
that nozzles 16, active material well member 20 and baffle
member 22 may be a single component. For example, they may
be formed as a unitary casting of copper or brass in a
manner similar to that described in U. S. Patent No.
6,217,824, the disclosure of which is incorporated herein by
reference thereto. It will be appreciated that by forming
nozzles 16, active material well member 20 and baffle member
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22 as a single component, several of the above-described
assembly steps may be eliminated.
FIG. 3 illustrates how tip assembly 10 is secured to a
the lower end of the barrel portion of a water cooled metal
making lance. Typically, a water cooled metal making lance
includes a plurality of concentrically arranged metal, e.g.,
steel, pipes. As shown in FIG. 3, the lance barrel has a
central pipe 34 welded or otherwise suitably affixed to the
active material well member 20. Central pipe 34 defines a
central passageway 36 for delivering pressurized active
material to nozzles 16. An annular space.formed between pipe
34 and a second, pipe 37 defines a coolant fluid inlet
passageway 38 which is connected to an unillustrated supply
of cooling water and delivers water to the lance tip
assembly. Preferably, although not necessarily, coolant
fluid baffle member 22 includes at least one internally
formed bypass passageway 40 desirably corresponding in
number and disposition to nozzles 16 to enable cooling of
the radially outermost areas thereof. During lance
operation, coolant water continuously flows through coolant
fluid delivery passageway 38 into passage means defined by
lower surface of the active material well member 20, the
coolant fluid baffle member 22 and the inner surface 30 of
the tip face member 12 and then into a coolant fluid return
passageway 42. More particularly, coolant water flows
downwardly through passageway 38 into a first coolant fluid
flow space defined by lower surface of the active material
well member 20 and the coolant fluid baffle member 22 and
bypass passageway(s) 40 (if present), around the exterior
surfaces of nozzles 16, and through a central opening 44 in
coolant fluid baffle member 22. As -coolant water passes
through central opening 44, its direction of travel is
changed. Specifically, the generally conical profile of
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protrusion 28 redirects the coolant water flow from
substantially parallel to substantially perpendicular to the
longitudinal axis 26 of the lance as it flows through a
second coolant fluid flow space defined by the coolant fluid
baffle member 22 and the inner surface 30 of the tip face
member 12. While in the second coolant fluid flow space, the
coolant water flows radially outwardly and around the
exterior surfaces of the tip face member outlets 14 and
between a plurality of radially arranged vanes 32, described
below. Upon exiting the second coolant fluid flow space, the
coolant water combines with the coolant water exiting bypass
passageway(s) 40, if present, and enters a coolant fluid
return passageway 42 formed between second pipe 37 and
third, and outermost pipe 46 whereupon the water is returned
from the lance tip to the coolant water supply and is again
recirculated through the lance. Coolant water flow volumes
may be expected to range from about 100 to about 2000
gallons per minute (gpm) through a typical water cooled
lance, although greater and lesser flows may be accommodated
by the present invention as may be desired or necessary.
As seen in several of the figures, protrusion 28 is
preferably located coaxially with the central longitudinal
axis 26 of the lance tip assembly. The contour of the
protrusion 28 is preferably substantially conical, although
it may have a somewhat convex or concave profile in relation
to the central longitudinal axis 26. According to a
presently preferred embodiment, the profile of protrusion 28
is substantially conical whereby the circumferential wall of
the protrusion diverges from the central longitudinal axis
26 at an angle a(FIG. 5) of between about 200-500, more
preferably about 35 .
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Additionally, the outside or working face of tip face
member 12 is preferably formed, either during or after
manufacture, with a recess 48 (FIGS. 1, 2 and 5) generally
corresponding in shape to protrusion 28. Recess 48 is
desirable in that it substantially equalizes the working
face thickness of the tip face member 12 in the region of
protrusion 28 which promotes substantially uniform thermal
characteristics therethrough. Moreover, as discussed below
in connection with FIG. 7, the contour of recess 48 may be
optimized to achieve a preferred "dimple profile ratio."
FIGS. 4 and 5 reveal a presently preferred
configuration of coolant flow directing vanes 32. Unlike
those disclosed in U.S. Patent Nos. 3,322,419 and 3,337,203
and United Kingdom Pat. No. 1,255,082, vanes 32 extend
essentially the entire axial distance or height between the
inner surface 30 of the lance tip face member 12 and the
lower surface of the coolant flow baffle member 22, and
essentially the entire radial distance from the central
protrusion 28 to the annular coolant fluid return passageway
42. A first set of vanes, identified by reference numeral
32a, intersect and are in contact with outlets 14 and
nozzles 16, whereby vanes 32a provide structural support to
the outlets and nozzles which serves to minimize distortion
of the tip face member 12 during lance operation. In
unreinforced lance tip assemblies the working face distorts
under normal operating conditions. This typically results in
internal nozzle distortion approximately two inches from the
nozzle exit. This nozzle distortion causes the oxygen jet to
act non-symmetrically which, in turn, reduces jet
efficiency, increases slag FeO and reduces metallic yield.
By making them an integral part of the nozzles 16, vanes 32a
function as reinforcing ribs that minimize nozzle
distortion.
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A second set of vanes, identified by reference numeral
32b, are preferably circumferentially spaced midway between
adjacent vanes 32a. As best seen in FIG. 5, each of vanes
32b are preferably formed, such as by machining, or the
like, with a depression 50 having a contour which is adapted
receive the lower surface of the coolant flow baffle member
22. A preferred, although non-limitative, shape of
depression is a generally lobe-shaped concavity. It is
preferred that the lower surface of the coolant flow baffle
member also be formed or machined to produce a shape that
essentially mates with depression 50. In this way, coolant
cross-flow between vanes is effectively prevented whereby
coolant flow control is optimized during lance operation.
The provision of vanes, 32a and 32b radiating from
protrusion 28 establishes highly controlled coolant water
flow paths that enhance the ability of the lance tip
assembly to convey water at high velocity and more uniformly
cool the lance tip. Additionally, the vanes provide
structural reinforcement for the lance tip face and nozzles,
thereby resulting in enhanced lance tip performance and
service life.
FIG. 6 shows a presently preferred elevational cross-
section configuration of vanes 32. According to the present
invention, each vane has a height "H" and an average
thickness "T" (measured at approximately H/2) at any point
along the radial extent of the vane. H is the axial distance
between the inner surface 30 of the lance tip face member 12
and the lower surface of the coolant flow baffle member 22.
As seen in FIG. 5, since the inner surface 30 the tip face
member 12 is preferably defined by a convex, preferably
frustoconical shape, the height "H" of the vanes varies from
protrusion 28 throughout the radial extent of the vanes. It
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is likewise preferable that the working face have a shape
corresponding to that of inner face 30 so as to present a
tip of substantially uniform thickness at its distal end,
thereby minimizing the potential for "hot spots" and uneven
cooling of the working face. That is, according to the
present invention, vanes 32 have thicknesses which vary as a
function of radial distance from protrusion 28 to the
perimeter of the lance tip face member. This thickness is
represented by the variable "T" in FIG. 6 and be can
observed most clearly in FIG. 4. It will be understood,
however, that the working face of the lance tip face member
12 may be essentially flat, in which case the height "H" and
thickness "T" of vanes 32 would be essentially constant
throughout the radial extent of the vanes beyond central
protrusion 28.
As part of the present invention, a "coolant
reinforcement ratio" or "CRR" with respect to the vanes is
defined as T/H. Without intending to be bound by theory, it
is believed that a CRR of approximately 0.3 contributes to
the superior cooling characteristics of the lance tip
assembly . according to the present invention versus
conventional lance tip assemblies known in the art.
Turning to FIG. 7, there is shown a limited cross-
section of the central region of lance tip face member 12.
That figure illustrates the flow path of coolant water as it
passes through coolant flow baffle member 22 and becomes
radially outwardly deflected by internal protrusion 28. Also
shown in FIG. 7 are certain dimensional variables defining
the general size and shape of recess 48 formed at the
working face of the tip. As depicted in FIG. 7, dimension
"D" is the diameter of a circle defined by the foremost
projection of the working face of the lance tip
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circumscribing recess 48. As also depicted in that figure,
"d" is the depth of recess 48 from the foremost projection
of the outer surface or working face of the lance tip to the
deepest point of the recess as measured along the central
longitudinal axis 26 of assembly 10. The aforementioned
"dimple profile ratio" or "DPR" is defined as D/d and a
beneficial DPR has been observed to be approximately equal
to 2.7.
A known failure mechanism in a typical BOF lance tip is
center face wear caused by slag and/or metal entrained in
the furnace gasses. In the present invention, a recess 48 of
appropriate depth "d" in relation to dimension "D" may
substantially reduce the exposed area of the tip working
face which reduces face wear. In contrast, a relatively flat
tip face would have a high DPR ratio. In any design,
however, the final recess profile is dependent on a
compromise between the requirements of the internal water
distribution profile, nozzle leg spacing and face thickness.
Similar to a beneficial CRR (and, again, without
intending to be bound by theory) it is believed that a
beneficial DPR contributes to the superior cooling
characteristics of the lance tip assembly according to the
present invention versus conventionally constructed lance
tip assemblies known in the prior art (as observed by the
inventors through empirical comparative experimentation).
The following are among the many advantages of a lance
tip assembly constructed according to the present invention:
1. higher momentum oxygen jets resulting in
increased height or distance of the lance from the metal
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bath (which, in turn, translates to reduced potential for
damage to the lance during operation);
2. reduced nozzle exit erosion;
3. less decay of the oxygen jets resulting in
improved bath mixing and lower slag FeO;
4. less decay of the oxygen jets resulting in lower
oxygen consumption per ton of steel produced;
5. extended lance service life without increasing
slag FeO;
6. increased cooling water flow (by reducing eddy
currents and other flow disturbances);
7. lower temperature differentials in the lance tip;
8. improved cooling water efficiency (through
convection) by virtue of the radial vanes;
9. improved cooling water distribution and velocity
by virtue of the flow-redirecting central protrusion;
10. increased cooling water volume via a less
restrictive design that results in lower friction (more
specifically, a metal making mill water cooling system is
rated at a given output for a given pressure drop across the
lance (a/k/a "pump curve"); by reducing the tip pressure
.drop, pump output increases without any additional energy
requirements;
11. reinforced tip face by virtue of the radial vanes
and the support post, thereby resulting in reduced tip face
distortion;
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12. reinforced nozzles by virtue of the radial vanes,
thereby resulting in reduced tip distortion;
13. reduced exposed area at the center of the tip face
by virtue of the central recess generally corresponding in
shape to the central protrusion; and
14. reduced exposed area for steel/slag adherence to
the center of the tip face (which may result in localized
burning) by virtue of the central recess generally
corresponding in shape to the central protrusion.
Although the invention has been described in detail for
the purpose of illustration, it is to be understood that
such detail is solely for that purpose and that variations
can be made therein by those skilled in the art without
departing from the spirit and scope of the invention as
claimed herein. For example, although the illustrated lance
assembly is constructed with a single centrally located
active material delivery conduit, it is possible that the
lance may contain more than one such passageway for
delivering similar or dissimilar active materials. Likewise,
it is also possible that the coolant water inlet passageway
may disposed interiorly rather than exteriorly of one or
more of the active material passageway(s).
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