Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a lance head for puddling
lances, having a plurality of expansion nozzles diverging from
the longitudinal axis towards the bath surface, at least one
cooling medium supply duct and at least one cooling medium
return duct, the ducts being arranged parallel to the longitudinal
axis, and a flow conducting means between the ducts for cooling
the lance head.
Lance heads for oxygen blowing lances'o~ this kind
have been found in practice to be very suitable for various
metallurgical processes, such as the LD, LDAC, LDS, SM and
electric oven processes. However, a problem for the pu'd'dling
operation~which gives rise to considerable repair costs
for the provision and installation of replacement heads~has
not yet been satisfactorily overcome, which problem is that
of extending, to an acceptable period, the more or less
short operational life of the lance heads previously employed.
The majority are damaged by being burnt out in the
middle between the nozzles after only a short period of
utilization. These center defects are dangerous, since the
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cooling water, which is at high pressure, sprays ~5 the
resulting openings into the fluid steel bath and can cause
oxyhydrogen explosions in the bath.
It is known that, during the puddling process,
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temperatures up to 22~3 K (2000 C) ~ccur in the va~R~y~
of the lance head. The melting temperature of copper, on
the other hand, is 1356 K (1083 C).
The heat energy occurr~ng at the outer surfaces of
the lance head must be conducted inwardly and withdrawn by
means of a cooling medium, e.g. cooling water. Technical
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proposals have been published, by means of ~a~te~ , patent
applications and the like, for solving the difficult problem
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of providing a suitable cooling medium supply in the lance
head for achieving an optimum cooling effect.
Practical experience in steel works has, however,
shown that the state of -the art achieved thereby is unsatisfactory
and none of the previously published proposals has led to a
sufficient durability of the lance heads.
It has been determined that, with the previously
known puddling lances of the above-described type, the
previously employed devices for conducting the cooling medium
into the lance head do not fully satisfy the flow requirements
in order to provide a sufEicient cooling at the parts of the
lance head which are subjected to the highest thermal stresses,
~; Although a cooling medium supply to the center of
the lance head would, in principle, be sufficient, the desired
cooling effect cannot be obtained due, among other reasons,
to eddy formation and dead water space formation, because
the duct elements for the water supply are not constructed
in accordance with requirements. Consequently, duct rings
for the cooling medium in the lanee head have been proposed, which
extend around the nozzles, without taking into account the alter-
ations in the cross-sectional surfaces between the individual,
adjacent nozzles with respect to the hydrodynamic effects.
In other previously proposed lance heads, the duct
rings terminate before an outer circle around the nozzles or
they are arranged with annular elements of different shapes
or the like within the lance head, which do not prevent an
undesired damaging eddy formation, but on the contrary promote
the same.
This automatically leads to insufficient cooling,
particularly of the central, highly thermally stressed region
of the lance head, so that after a relatively short time,
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damage of the lance head occurs by fusing of the copper.
The lance head therefore prematurely becomes unusable,
; which results in frequent interruption of the process and
of production. Furthermore, there is an increased risk of
danger by possible oxyhydrogen formation (H2O dissasso-
eiation), as mentioned hereinbefore.
It is accordingly an object of the present invention
to substantially mitigate the above-described disadvantages
of previously proposed lance heads of this kind and to
provide improved cooling of the thermally highly stressed
regions of the lance heads, and furthermore to achieve
greater durability and operational safety by a construe-
tion of the eooling region whieh is optimally adapted to
hydrodynamie requirements for lance head eooling.
Aeeording to the present invention, there is provided
a lanee head for puddling lanees, having a plurality of
expansion nozzles diverging from the longitudinal axis
towards a bottom plate of the lanee head, at least one
eooling medium supply duet and at least one eooling medium
return duet, said duets being arranged eoneentrieally with
the longitudinal axis, and flow conducting means, having
eoneave portions on the side facing the bottom plate of
the lanee head, between said duets for eooling said lanee
head and for eontrolling the direction of flow of the
cooling medium, the flow conducting means comprising a
flow defleetor member on a pipe delimiting the supply
and return duets, said flow deflector member extending
in a direction towards the longitudinal axis and being
arranged at a spaeing from said bottom plate and sealingly
eneireling said nozzles, said eoneave portions being
formed in said flow defleetor member on the side facing
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the bottom plate in the radial regions of narrow cross
section between neighbouring nozzles, the dimensions of
said concave portions being such that, as the distance
between saied nozzles decreases in a horizontal plane,
the distance between the flow deflector member and bottom
plate increases proportionally in a vertical plane to
maintain a constant cross-sectional area for the flow of
cooling medium.
Due to the concave formation of the flow deflector
member, as the flow cross-section between two adjacent
expansion
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n~zzles increasingly narrows in the horizontal plane, this is
compensated proportiona-tely in the vertical plane in order to
maintain a constant flow cross-section. The curvature o~ the
concavity can thus be exactly calculated.
Preferably, over the entire free inner surface of
the bottom of the lance head, there is a uniformly high flow
speed of the cooling medium, which ensures that a film
evaporation-reduction of the solid/liquid heat transfer,
which, as has been found, is in causative relationshlp to
the previous fusing of the copper in the central region of
the lance head bottom, is substantially prevented.
This function may be assisted, in particular, by
a formation of the flow deflector member in which an edge
inwardly limiting the flow deflector member extends at least
as far as a circle inwardly delimiting the expansion nozzles
and is arranged inclined towards a central front face in
accordance with the concave formation, whereby the cooling
medium flow is intensively deflected onto the thermally highly
stressed central region of the bottom of the lance head.
The advantageous function of the lance head is
closely connected with a low resistance return flow of the
cooling medium, which is also important for the optimum cooling
effect. For this purpose, the flow deflector member preferably
has a convex upper surface which defines the cooling medium
return and which is formed substantially congruent corresponding
to the concave surface of a flow divider member.
Moreover, the flow cross-section between the
concavely formed divider member and the conve~ upper surface
of the flow deflector member is preferably as large as the
flow cross-section beneath the flow deflector member. It
has been found that, if the above relationships
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are exactly maintained, the flow spaces of
the cooling medium can be so ideally formed that the cooling
~` medium supply and return can be effected in opposite directions
with a full cooling effect.
The invention will be more readily understood from
the following description of a preferred embodiment thereof
given, by way of example, with reference to the accompanying
drawing, which shows a view taken in section through a lance
head of a puddling lance.
The lance head illustrated in the drawing has four
expansion nozzles 9 arranged diverging from a longitudinal
axis 7. A flow deflector member 1 is conneated to a pipe or
pipe section 5 which separates a cooling medium supply duct 3
and a cooling medium return duct 4 from one another.
The flow deflector member 1 can be fixed, in known
manner, by any means, e.g. by welding, soldering, clamping,
adhesion or the like or by means of resilient connecting elements
fixed to the pipe 5.
The flow deflector member 1 is formed, at its
underside, facing towards a bottom plate 6, in the radial
vicinity 8 of the expansion nozzles 9, with a concave shape cor-
responding to the cross-sectional narrowing in the region 8
between the expansion nozzles 9, for maintaining the constant
cross-sectional area in the region 8, as described hereinbefore.
An edge 10 inwardly delimiting the flow deflector
member 1 extends beyond the circle 11 inwardly delimiting the
expansion nozzles 9 and deflects the cooling medium to the
central area 12 of the lance head bottom 6. A convex
surface 13 of the flow deflector member 1 is substantially
congruent with a concave surfàce 14 of a divider member
2, which ensures a damage-free, low resistance return of the
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cooling medium.
To achieve satisfactory flow of the cooling medium,
it is necessary carefully to seal the flow deflector member 1
with respect to the expansion nozzles 9. The sealing can be
produced, e.g., by an unreleasabl~ connection, such as by
soldering, welding or the like, or by releasable seals, for
example of a long lasting resilient material, such as
elastomers in the form of thermoplastics or thermo~ëtting
plastics.
Practical testing of the present lance head has
shown that the durability of the present puddling lances can
be considerably increased with respect to that of prior art
lances, so that, in addition to a measurable economic improvement,
the danger associated with ¢entral defects is substantially
avoided.
