Note: Descriptions are shown in the official language in which they were submitted.
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Steel STRIP ElEATIltl~; FURNAC13
AC~RG~)IJ~ OF_q~lE INVENTION
The present invention relates generally to a
steel strip heating furnace for heating steel strip
conveyed along a preset course. More particularly, the
invention relates to a steel strip heating furnace
which can eliminate the adverse influence of heat
radiation.
0 The structure of a typical furnace 10 is
shown in Fig 1 in transverse section The furnace 10
has a furnace body comprising a ceiling 12, a floor 14
and side walls 16 extending between the ceiling and the
floor. The course for the steel strips 20 is defined
within the furnace body by a skid beam 22 supported us
the floor 14. A plurality of the steel strips 20 are
mounted on the skid beam 22 transversely across the
course, and forcibly transported along the course.
As they travel along the course the steel
strips 20 are heated by radiation from the furnace
body. Therefore, the central section AYE of each steel
strip 20 generally receives heat radiated by the
ceiling 12 and the floor 14. On the other hand, the
ends 20B of the steel strips are subject not only to
heat from the ceiling 12 and floor 14 but also from the
opposing side wall 16. Therefore, the end sections 20B
receive more heat than the central section. This
generates a thermal gradient between the central
section AYE and the end sections 20B, and, as a result
30 tends to heat the end sections 20B excessively. These
thermal gradients generate deformation stresses between
the end sections and the central section.
In view of the above defect, an improvement
to this furnace, shown in Fig. 2 has been proposed. In
the proposed improvement, an attempt has been made to
reduce the effective heat radiation area by forming a
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recess in the side wall of the furnace opposite the
transverse edges of the steel strip. The recess 18 is
of depth a cud and width (be) which are
significantly smaller than the depth ABED and width
(BY) of the corresponding area of the furnace of
Fig. 1. Since the heating at the transverse ends of
the steel strip is determined by effective heat
radiation area a x be x furnace length), the end
heating can be moderated by reducing the effective heat
radiation area JAB x BY x furnace length) of the
furnace of Fig. 1.
However, even the improvement of Fig. 2 is
not fully satisfactory in that it does not actually
control the heat radiation applied to the transverse
- 15 ends of the steel strip, but rather relies solely on
geometry for even heating.
SMEAR OF TOE I~V~TIO~
Therefore, it is an object of the present
invention to provide a heating furnace for steel strips
or plate which can uniformly heat the entire surface of
the steel.
Another and more specific object of the
invention is to provide a heating furnace which can
adjust the heat applied to the transverse ends or edges
of the steel in order to achieve even heating over the
entire surface of the steel.
In order to accomplish the above-mentioned
and other objects, a steel strip heating furnace,
according to the invention, has a movable wall which
can be positioned closer or farther away from the
transverse edges of the steel in order to adjust the
heat radiation applied to the opposing edges of the
steel. The movable wall extends parallel to the
longitudinal axis of a course along which the steel is
transported through the furnace.
Preferably, the movable wall constitutes part
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of a ceiling of a furnace body and can be shifted
vertically toward and away from the transverse edges of
the steel so as to adjust the high-temperature heat
radiation transmission area about the opposing
transverse edge and thus control the heat applied to
the corresponding section of the steel. Also, it is
especially advantageous to provide means for cooling the
movable wall so as to adjust the heat radiation
then from.
0 Therefore, the heating furnace, according to
the present invention, can control the heat applied to
the transverse edges of the steel so that the entire
surface of the steel can be heated uniformly.
According to one aspect of the invention, a
heating furnace for heating steel strip comprises a
furnace body defining an enclosed heating space
therein, the furnace body including a longitudinal side
wall, means for conveying the steel along a preset
course through the furnace body, a movable wall
extending along at least part of the longitudinal
length of the course and having a section interfering
with heat radiation from furnace body toward an end
section of the steel nearest the side wall and an
actuator associated with the movable wall for moving
I the latter toward and away from the end section of the
steel strip
According to another aspect of the invention,
a process for heating steel strips comprises the steps
of:
feeding a plurality of steel strips along a
preset course;
heating walls of a furnace surrounding the
course so as to heat the steel strips by radiation from
the walls;
I providing a movable wall opposing the
transverse end sections of the steel strips on opposite
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sides of the axis of travel thereof, which movable wall
extends essentially parallel to and overlapping at
least a part of the entire length of the course; and
positioning the movable wall relative to the
transverse end section of the steel strips so as to
control heat transmission from the walls of the furnace
to the transverse end section of the steel strip.
BRIEF DESCRIPTION OF TOE DRYNESS
The present invention will be understood more
fully from the detailed description given horribly and
from the accompanying drawings of the preferred
embodiment of the invention, which, however, should not
be taken to limit the invention to the specific
embodiment, but are for explanation and understanding
only.
In the drawings:
Figs. 1 and 2, as explained above, are
cross-sections through major parts of conventional
furnaces;
Fig 3 is a longitudinal section through a
heating furnace in accordance with the preferred
embodiment of the present invention;
Fig. 4 is a cross-section through the heating
furnace taken along line IV-IV of Fig. 3;
Fig. 5 is an enlarged section through a
movable wall employed in the preferred embodiment of
the heating furnace of Fig. 3; and
Fig. 6 is a graph of the relationship between
the temperature gradient and distance across the steel
wrap.
DE:SCRIPq~IO~ OF lye: PREFERRED E~!lBODIlqENT
Referring now to the drawings, particularly
to Figs. 3 and 4, a furnace body 30 generally comprises
the ceiling 32, the floor 34 and side walls 36
I extending between the ceiling and the floor. The
furnace body 30 defines a heating chamber AYE for
heating a plurality of steel strips 20 transported or
conveyed along a preset course A. A plurality of skid
beams 37 supported by the floor 34 extend
longitudinally along the furnace body 30. The skid
beams 37 define the course through the furnace. As in
the prior art, the steel strips are mounted sideways on
the skid beams so that their longitudinal ends 20C
oppose the side walls 36, which longitudinal ends will
be referred to hereafter as transverse edges. The
0 sections 20B of the steel strips surrounding the
transverse edges 20C will be referred to hereafter as
"transverse end sections.
Vertically extending end walls 35 also
extends between the ceiling 32 and the floor 34 and
form part of the furnace body 30. The vertical wall 35
located at the downstream of the course A is formed with
an outlet 68 through which the heated metal strips 20
are taken out. The outlet 68 can be closed by a
closure aye.
A movable wall 40 opposes each of the
transverse end sections 20B. The movable wall 40
extends along the side wall 36 parallel to the
transverse end section 20B of the step strip 20, as
shown in Fig. 4. The movable wall 40 is suspended from
the ceiling 32 by means of a hanger mechanism 50. The
hanger mechanism 50 comprises vertical hanger pipes AYE
and 52B at the opposite longitudinal ends AYE and 40B
of the movable heating wall 40. The hanger pipes AYE
and 52B pass through openings 38 in the ceiling 32 of
30 the furnace body 30 and are connected to each other by
a horizontal beam 54. The horizontal beam 54 is
connected to a pair of actuators 56 such as hydraulic
cylinders which can be operated manually or
automatically to raise and lower the horizontal beam 54
35 and the movable wall 40 toward and away from the
transverse end section 20B of the steel strip 20.
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If necessary, the actuators 56 may be
associated with a controller to be controlled the
operation thereof. The controller may control the
actuator operation and whereby control the height of
the movable wall 40. The controller may also
associated with a heating condition sensor for
detecting heating condition of the steel strips in the
furnace on the basis of the condition detecting by the
sensor. This may ensure uniformity of heating over the
entire surrounding of the steel strip.
The hanger pipes AYE and 52B are hollow
cylindrical pipes serving as cooling water conduits
with passages AYE and 53B. The cooling water passages
AYE and 53B communicate with cooling water passages
1 formed in the movable wall 40. As shown in Fig. 5, the
cooling passage in the movable wall 40, which is
generally referred to by the reference numeral ~41",
comprises a plurality of, e.g. six, hollow pipes 45
each connected to the cooling passages AYE and 53B
through galleries (not shown). The cooling water
passages AYE, 53B and 41 form a complete cooling water
circuit 44.
Flow control valves AYE and 58B installed in
the cooling water passages AYE and 53B control the
cooling water flow rate through the cooling water
circuit. the flow control valves AYE and 58B can be
controlled manually or automatically so as to adjust
the cooling water flow through the cooling water
circuit in accordance with the heating conditions of
the movable wall.
The cooling water passage AYE is connected to
a fluid pump 55 which draws cooling water from a
cooling water reservoir 59 for circulation through the
cooling water circuit 44. The cooling water passage 44
is connected to the cooling water reservoir 59 at one
end and to a return line (not shown) at the other end
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via flexible hoses AYE.
The pipes aye forming the cooling water
passages 45 within the movable wall 40 are anchored
within a matrix of fireproof material 62 forming the
movable wall 40. Also, the lower section of the hanger
pipes AYE and 52B are anchored within the fireproof
material 62 surrounding the lower ends of the hanger
pipes .
The flow control valve and the fluid pump may
be controlled the operations manually or automatically
in per so well known manner in accordance with the
heating condition in the furnace. By controlling the
flow control valves and the fluid pump, flow rate of
the cooling water can be varied for varying cooling
effect for the movable wall 40.
Water-tight traps 64 with metal water seals
66 encircle both openings 38 in the ceiling 12 through
which the hanger pipes AYE and 52B pass. The
water-tight traps 64 and metal water seals 66 seal the
furnace against water leakage.
With the furnace construction according to
the preferred embodiment as set forth above.
The steel strips 20 enter the heating furnace
from the upstream end of the course A. The steel
strips are lazed across the skid beams 37 so that their
longitudinal end sections 20B oppose the side walls 36.
The actuators 56 are operated to place the
movable wall 40 near the transverse end section 20B of
the steel strip. At the same time, the fluid pump 55
starts to circulate the cooling water trough the
cooling water circuit 44.
The steel strips 20 are heated by radiation
from the ceiling 32, the floor 34 and the side walls
36. The movable wall 40 interferes with transmission
of heat radiated toward the transverse end sections 20B
of the steel, Therefore, the effective heat
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transmission area adjoining the transverse end sections
20B is smaller than in conventional furnaces.
Fig. 6 shows the results of experiments
designed to measure the temperature difference between
the transverse end section 20B and the central section
AYE. As is apparent wherefrom, in conventional furnaces
(as shown in solid line), the temperature difference
between the end section 20B and the central section AYE
can be as high as approximately 80C. This contrasts
0 sharply with the results for the inventive furnace
shown in broken line in Fig. 6. In this case, there is
almost no temperature difference between the end
section 208 and the central section AYE. In other
words, the steel strip can be heated evenly over its
entire surface.
According to the shown embodiment, since the
movable wall can be cooled by circulating cooling water
through the cooling water circuit 44, the surface
temperature of the movable wall can be held low enough
7 to significantly influence the heating conditions at
the transverse end section 20B.
In addition, according to the shown
embodiment, the thickened lower section of the side
wall AYE narrows the clearance between the transverse
edge 20C of the steel strip 20 and the inner periphery
of the side wall 36. This suppresses convection of
gaseous combustion products between the lower
combustion zone and the upper combustion zone in order
to reduce convection heating.
It should be noted that although the thicker
side wall AYE will help reduce convection of combustion
product and thus reduce convection heating, it is not a
necessary aspect of the invention. In cases where the
heat isolation due to the movable wall 40 is
sufficient, the side wall can be of sheer
configuration. On the other hand, the fluid
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circulating through the cooling water circuit 44 need
not necessarily be water. It can be replaced with any
suitable cooling fluid. Further, it is not always
necessary to build the cooling system into the movable
5 wall.
Furthermore, although hydraulic cylinders
have been shown for actuating the movable wall relative
to the transverse end section 20B of the steel strip
20, they may be replaced by any suitable actuating
0 system.
As will be appreciated wherefrom, according to
the present invention, heat can be applied uniformly
over the entire surface of the steel strips for even
hefting. This prevents the generation of uneven
5 deformation stresses across the steel strip. As a
result, tube steel strip can be rolled andtor forged to
an even thickness and width.
Therefore, the present invention
satisfactorily and successfully fulfills all of the
20 objects and advantages sought therefore
