TITLE OF INVENTION
Refractory lining repairing method
TECHNICAL FIELD
[0001]
The present invention relates to a method of repairing a refractory lining on the inner side of
a shell of a ladle or a trough.
It should be noted that the term "refractory lining repairing method" in the present invention
has a concept which includes a removal work of removing a part of a refractory lining on the inner
side of a shell of a ladle or a trough, and a repair work after the removal.
BACKGROUND ART
[0002]
A refractory lining on the inner side of a shell of a ladle or a trough undergoes wear due to
molten metal (metal) such as molten steel or molten pig iron, or slag, received in the ladle or the
trough. Thus, a method is generally employed which comprises: removing a worn part of a
refractory lining; and then casting a repairing material (castable refractory material) which is the
same as the refractory lining in terms of material composition, thereby repairing this refractory
lining.
Heretofore, as a removal technique for a refractory lining, there has been known a removal
technique using a striking force (striking removal), as disclosed in the following Patent Document
1.
CITATION LIST
[Patent Document]
[0003]
Patent Document 1: JP-A H09-273867

SUMMARY OF INVENTION
[Technical Problem]
[0004]
In the striking removal, it is often the case that an unworn part of the refractory lining is also
destroyed and removed, and as a result, the amount of the repairing material used becomes larger,
resulting in an increase in repair costs. Moreover, it is likely that unintended irregularities are
formed in the refractory lining after being subjected to the removal, and thus air or slag flows
around among the irregularities during the casting of the repairing material, so that the refractory
lining after being subjected to the repairing becomes more likely to wear. Further, due to
mechanical shock during the striking removal, internal defects are likely to be developed in the
refractory lining after being subjected to the removal, and in this regard, the refractory lining after
being subjected to the repairing becomes more likely to wear.
[0005]
Therefore, a technical problem to be solved by the present invention is to provide a refractory
lining repairing method capable of allowing a refractory lining after being subjected to repairing
to become less likely to wear.
[Solution to Technical Problem]
[0006]
According to a first aspect of the present invention, there is described a method of repairing
a refractory lining on an inner side of a shell of a ladle or a trough. The method comprises: a first
laser radiation step of using a laser cutter to radiate a laser to the refractory lining, thereby cutting
off a part of the refractory lining; and a repair work conducting step of conducting a repair work
of placing a mold form inside the ladle or the trough, and then casting a repairing material into an
interspace between the mold form and a cutout surface of the refractory lining after being subjected
to the cutting-off in the first laser radiation step, thereby repairing said refractory lining.
According to a second aspect of the present invention, there is described a method of repairing
a refractory lining on an inner side of a shell of a ladle or a trough. The method comprises: a
second laser radiation step of using a laser cutter to radiate a laser to the refractory lining, thereby
melting a part of the refractory lining; a striking step of applying a striking force to a region of the
refractory lining influenced by the laser radiation in the second laser radiation step, thereby causing

the region to break away; and a repair work conducting step of conducting a repair work of placing
a mold form inside the ladle or the trough, and then casting a repairing material into an interspace
between the mold form and a cutout surface of the refractory lining after being subjected to the
breaking-away in the striking step, thereby repairing said refractory lining.
According to a third aspect of the present invention, there is described a method of repairing
a refractory lining on an inner side of a shell of a ladle or a trough. The method comprises: a
third laser radiation step of using a laser cutter to radiate a laser to the refractory lining, from one
direction in a vertical section orthogonal to a lateral wall of the shell, thereby melting a part of the
refractory lining; a fourth laser radiation step of using a laser cutter to radiate a laser to the
refractory lining, from another direction in the vertical section orthogonal to the lateral wall of the
shell, thereby causing a region of the refractory lining influenced by the laser radiation in the third
laser radiation step to break away; and a repair work conducting step of conducting a repair work
of placing a mold form inside the ladle or the trough, and then casting a repairing material into an
interspace between the mold form and a cutout surface of the refractory lining after being subjected
to the breaking-away in the fourth laser radiation step, thereby repairing said refractory lining.
[Effect of Invention]
[0007]
The present invention makes it possible to minimize a part of the refractory lining to be
removed to allow the refractory lining after being subjected to repairing to become less likely to
wear.
BRIEF DESCRIPTION OF DRAWINGS
[0008]
FIG. 1 is a diagram conceptually showing a refractory lining repairing method according to
a first embodiment of the present invention.
FIG. 2 is a vertical sectional view of a blast furnace trough to be repaired by the method
according to the first embodiment, taking along a vertical plane intersecting orthogonally with a
lateral wall of a shell of the trough and including a maximum wear point in each of a pair of lateral
walls of a refractory lining of the trough.
FIG. 3 is a conceptual diagram showing a procedure of a repair work (repairing material

casting work) after removal of a part of the refractory lining in the method according to the first
embodiment.
FIG. 4 is a conceptual diagram showing a state after completion of the repair work in FIG. 3.
FIG. 5 is a diagram conceptually showing a refractory lining repairing method according to
a second embodiment of the present invention.
FIG. 6 is a diagram conceptually showing a refractory lining repairing method according to
a third embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
[0009]
< First Embodiment >
FIG. 1 conceptually illustrates a refractory lining repairing method according to a first
embodiment of the present invention. In the first embodiment, after removing a part of a
refractory lining 2 on an inner side of a shell 11 of a blast furnace trough 1, a repair work is carried
out.
Generally, the refractory lining 2 on the inner side of the shell 11 of the blast furnace trough
1 comprises, in a vertical section of the refractory lining 2, a slag-resistant material in a surficial
layer on an upper side of the blast furnace trough 1, and a metal-resistant material in a deep layer
provided on a lower side with respect to the slag material. However, in this specification, the
refractory lining 2 will be described as an integral structure without distinguishing between the
slag-resistant material and the metal-resistant material, as shown in FIG. 1. The same is also
applied to FIGS. 2 to 6.
Here, as the slag-resistant material, it is possible to use a material excellent in slag resistance
and thermal spalling resistance, such as an alumina-silicon carbide-carbon based refractory
material containing a large amount of silicon carbide. As the metal-resistant material, it is
possible to use a material excellent in molten pig iron resistance and FeO resistance, such as an
alumina-spinel-silicon carbide-carbon based refractory material comprising a primary component
consisting of alumina-magnesia based spinal.
[0010]
The method according to the first embodiment comprises: a first laser radiation step of using
a laser cutter 3 to radiate a laser (laser beam) to the refractory lining 2, thereby cutting off a part

of the refractory lining 2; and a repair work conducting step of conducting a repair work of placing
a mold form 6 inside a ladle or the blast furnace trough 1, and then casting a repairing material 7
into an interspace between the mold form 6, and a cutout surface 24 of the refractory lining 2 after
being subjected to the cutting-off in the first laser radiation step, thereby repairing this refractory
lining 2.
The laser cutter 3 may be composed of a fiber laser which extends from a control unit 5, and
attached along a robot arm 4 such that a radiation part 3a thereof is located at a distal end of the
robot arm 4. The robot arm 4 is composed of, e.g., a six-axis vertical articulated robot arm, and
is configured to, based on control information from the control unit 5, freely move the posture and
position of the radiation part 3a attached at the distal end thereof, thereby changing a laser radiation
position and direction.
It should be noted that the type, laser power, etc., of a laser source in the laser cutter 3 may
be appropriately determined according to a material, etc., of the refractory lining 2 to be cut. In
other words, the type, laser power, etc., of the laser source in the laser cutter 3 may be appropriately
determined to allow the laser cutter 3 to cut a part of the refractory lining 2.
[0011]
In the first laser radiation step, a cutting start point is determined in a top end surface 21 of
the refractory lining 2. FIG. 2 conceptually illustrates one example of a step of determining the
cutting start point.
First of all, a maximum wear point B (B1) is determined which is a point at which wear of a
lateral wall 22 of the refractory lining 2 on one lateral wall 12 of the shell 11 reaches a position
closest to the lateral wall 12 of the shell 11. The shell 11 of the blast furnace trough 1 has a pair
of opposed lateral walls 12. Thus, a maximum wear point B (B2) is also determined in a lateral
wall 22 of the refractory lining 2 on the other lateral wall 12 of the shell 11.
The maximum wear point B (B1, B2) can be determined, for example, by scanning a laser
beam along the surface of the lateral wall 22 to measure the height dimension of the surface of the
lateral wall 22.
It is known that wear of the lateral wall 22 of the refractory lining 2 in the blast furnace trough
1 tends to become larger on the upper side of the blast furnace trough 1 (on the side of the top end
surface 21 of the refractory lining 2) than on the lower side of the blast furnace trough 1 (on the
side of an inner bottom surface 23 of the refractory lining 2).

It is also known that a ladle for receiving molten metal such as molten pig iron or molten steel
has a similar tendency. Further, it is known that, when molten pig iron or molten steel is filled in
the blast furnace trough 1 or the ladle, the blast furnace trough 1 or the ladle is likely to wear,
particularly, at a position corresponding to a boundary between molten metal (metal) and slag
(hereinafter referred to as "boundary position") and a region just below the boundary position (the
boundary position and the region just below the boundary position will hereinafter be referred to
collectively as "metal-slag boundary zone"). Thus, the maximum wear point B in FIG. 2
corresponds to the metal-slag boundary zone.
[0012]
FIG. 2 is a vertical sectional view of the blast furnace trough 1, taking along a vertical plane
intersecting orthogonally with the lateral wall 12 of the shell and including the maximum wear
point B in each of the pair of lateral walls 22 of the refractory lining 2. In this vertical section,
assuming that an intersection point between the inner bottom surface 23 of the refractory lining 2,
and an inner lateral surface 22a of the (wear-damaged) refractory lining 2 on the lateral wall 12 of
the shell 11 is represented as a point C, a point at which a straight line D passing through the
maximum wear point B and the point C intersects the top end surface 21 of the refractory lining 2
is set as a cutting point E. Then, in the first embodiment, a point at which the cutting point E is
located after it is moved to a longitudinal end of the blast furnace trough 1 along the lateral wall
12 of the shell 11 is set as a cutting start point F (see FIG. 1).
[0013]
Further, in the first embodiment, an intersection point between the bottom surface 23 of the
refractory lining 2 and the inner lateral surface 22a of the (wear-damaged) refractory lining 2 in
the vertical section including the cutting start point F and intersecting orthogonally with the lateral
wall 12 of the shell 11 is set as a cutting end point G, as shown in FIG. 1. That is, in the first
laser radiation step of the method according to the first embodiment, a laser beam is radiated from
the laser cutter 3 in a direction from the cutting start point F toward the cutting end point G. Then,
the radiation part 3a of the laser cutter 3 is moved in an approximately horizontal direction along
the lateral wall 12 of the shell 11 so as to allow a laser beam to be moved from the cutting start
point F along the lateral wall 12 of the shell 11 (to be moved in a direction indicated by the arrowed
line A in FIG. 1), thereby cutting off a part of the refractory lining 2 along the lateral wall 12 of
the shell 11.

[0014]
When cutting off a part of the refractory lining 2 while moving the radiation part 3a of the
laser cutter 3, a molten refractory material arises in an area of the refractory lining 2 through which
a laser beam has just passed (generated between a cut-off (disconnected) part of the lateral wall 22
and the cutout surface 24. This molten refractory material is likely to remain between the cut-off
part of the lateral wall 22 and the cutout surface 24. In this case, when the molten refractory
material is cooled and solidified again, it bonds the cut-off part of the lateral wall 22 and the cutout
surface 24 together. For this reason, when cutting off a part of the refractory lining 2 while
moving the laser cutter 3, the refractory lining 2 may be cut while gas is blown against an area of
the refractory lining 2 through which a laser beam has just passed, thereby removing a molten
refractory material interposed between the cut-off part of the lateral wall 22 and the cutout surface
24. Examples of the gas may include air, argon and nitrogen.
[0015]
Alternatively, in order to remove a molten refractory material arising when cutting off a part
of the refractory lining 2 by using the laser cutter 3, a plurality of holes each extending from the
inner lateral surface 22a of the refractory lining 2 toward the straight line D (toward the shell 11)
may be provided before cutting off a part of the refractory lining 2 by using the laser cutter 3. In
this case, the molten refractory material can be discharged and removed from the holes. Although
the positions and the number of the holes are not particularly limited, it is particularly preferable
that the holes are provided in a lower portion of the lateral wall 22.
Further, after providing the plurality of holes and, when cutting off a part of the refractory
lining 2 by using the laser cutter 3, the part of the refractory lining 2 may be cut off while gas is
blown against an area of the refractory lining 2 through which a laser beam has just passed. This
makes it possible to effectively discharge and remove the molten refractory material from the holes.
[0016]
The method according to this embodiment comprises the repair work conducting step,
following the first laser radiation step. In the repair work conducting step, after completion of
the first laser radiation step, the mold form 6 is placed inside the blast furnace trough 1, as shown
in FIG. 3, and then the repairing material 7 is cast into an interspace between an outer lateral
surface 61 of the mold form 6 and the cutout surface 24 of the refractory lining 2 after being
subjected to the cutting-off by using the laser cutter 3, thereby repairing this refractory lining 2.

Here, the repairing material 7 is the same as the refractory lining 2 in terms of material
composition.
Further, in the first embodiment, the work of casting the repairing material 7 is performed by
inserting a material supply member such as a hose 8 into an interspace between an upper end of
the mold form 6 and the cutout surface 24 of the refractory lining 2. For this reason, in the first
embodiment, the mold form 6 is placed such that the width of the interspace between the upper
end of the mold form 6 and the cutout surface 24 of the refractory lining 2 on one side where the
hose 8 is inserted becomes greater than the outside diameter of the hose 8.
It should be understood that the casting of the repairing material can be performed without
using the hose 8. For example, a distal end of a funnel or hopper serving as the material supply
member may be inserted into the interspace between the upper end of the mold form 6 and the
cutout surface 24 of the refractory lining 2, to cast the repairing material 7 through this material
supply member.
[0017]
After the casting, the repairing material 7 is cured and dried by heating. Subsequently, the
mold form 6 is extracted (removed) to complete the repair work of repairing the refractory lining
2 on the inner side of the shell 11 of the blast furnace trough 1, as shown in FIG. 4.
[0018]
As above, in the first embodiment, the first laser radiation step and the repair work conducting
step are performed with respect to each of the pair of lateral walls 22 of the refractory lining 2.
This makes it possible to remove a part of each of the pair of lateral walls 22 of the refractory
lining 2 on the inner side of the shell 11 of the blast furnace trough 1, and recover the refractory
lining 2 to its original state.
In the first embodiment, the refractory lining 2 is partly cut off and removed by using the
laser cutter 3 (this removal technique will hereinafter referred to as "laser removal"), so that the
resulting cutout surface 24 is formed as a less-uneven smooth surface, as shown in FIG. 3. Thus,
air or slag becomes less likely to flow around among irregularities during the casting of the
repairing material 7, so that the refractory lining after being subjected to the repairing becomes
less likely to wear. In the laser removal as in the first embodiment, as compared to the striking
removal as disclosed in the Patent Document 1, internal defects due to mechanical shock are less
likely to be developed in the refractory lining after being subjected to the removal, and in this

regard, the refractory lining after being subjected to the repairing becomes less likely to wear. In
the first embodiment, the laser removal is performed along the straight line passing through the
maximum wear point B, as described in connection with FIG. 2, so that it is possible to minimize
a removal region of the refractory lining 2. This makes it possible to minimize the amount of the
repairing material 7 to be used, and keep repair costs down
[0019]
In the first embodiment, the straight line D is drawn such that it passes through the maximum
wear point B, and the point C at which the inner bottom surface 23 of the refractory lining 2
intersects the inner lateral surface 22a of the (wear-damaged) refractory lining 2 on the lateral wall
12 of the shell 11, as shown in FIG. 2. Alternatively, the straight line D may be drawn such that
it passes through the point C, and a point located inside the refractory lining 2 at a position closer
to the shell 11 than the maximum wear point B, in FIG. 2. In this case, although the removal
region of the refractory lining 2 becomes slightly larger as compared to the first embodiment, the
removal region can be narrowed, as compared to the striking removal as disclosed in the Patent
Document 1. Further, the cutout surface of the refractory lining 2 is also formed as a less-uneven
smoother surface, as compared to the striking removal as disclosed in the Patent Document 1.
Thus, the refractory lining after being subjected to repairing becomes less likely to wear.
[0020]
In the first embodiment, the point at which the cutting point E is located after it is moved
from the position illustrated in FIG. 2 to the longitudinal end of the blast furnace trough 1 along
the lateral wall 12 of the shell 11 is set as the cutting start point F (see FIG. 1). Alternatively, the
cutting point E may be set directly as a cutting start point. In a case where a target to be repaired
is a ladle, it is more effective to use the cutting point E directly as a cutting start point.
[0021]
< Second Embodiment >
FIG. 5 conceptually illustrates a refractory lining repairing method according to a second
embodiment of the present invention.
It should be noted that, in the following embodiments, an element or component similar to
that in the first embodiment is assigned with the same reference sign, and duplicated description
thereof will be omitted.

The method according to the second embodiment comprises: a second laser radiation step of
using a laser cutter 3 to radiate a laser (laser beam) to a refractory lining 2, thereby melting a part
of the refractory lining 2; a striking step of applying a striking force to a region of the refractory
lining 2 influenced by the laser radiation in the second laser radiation step, thereby causing the
region to break away; and a repair work conducting step of conducting a repair work of placing a
mold form 6 inside a ladle or a blast furnace trough 1, and then casting a repairing material 7 into
an interspace between the mold form 6 and a cutout surface 24 of the refractory lining 2 after being
subjected to the breaking-away in the striking step, thereby repairing this refractory lining 2.
[0022]
In the second laser radiation step of the method according to the second embodiment, a laser
beam is radiated from the laser cutter 3 in a direction from a laser radiation start point F on a top
end surface 21 of the refractory lining 2 toward a point H located inside the refractory lining 2 and
on a vertical section including the point F and orthogonally intersecting with a pair of opposed
lateral walls 12 of a shell 11 of the blast furnace trough 1, as shown in FIG. 5(a). In this process,
a laser power is preliminarily set to have an intensity enough to melt the refractory lining 2 up to
the point H located inside the refractory lining 2.
[0023]
Here, the laser radiation start point F in the second embodiment is the same as the cutting
start point F in the first embodiment. Specifically, in the second embodiment, the cutting point
E illustrated in FIG. 2 is set as a laser radiation point, and a point at which the laser radiation point
E is located after it is moved to a longitudinal end of the blast furnace trough 1 along the lateral
wall 12 of the shell 11 is set as the laser radiation start point F. Further, the point H located inside
the refractory lining 2 is an upper limit position of a depth-directional range in which melting by
a laser beam is effectively exerted.
Alternatively, the laser radiation point E illustrated in FIG. 2 may be set as a laser radiation
start point, and a point located inside the refractory lining 2 and on the straight line D illustrated
in FIG. 2 may be set as a laser radiation end point. Further, as mentioned in the first embodiment,
the straight line D may be drawn such that it passes through the point C, and a point located inside
the refractory lining 2 at a position closer to the shell 11 than the maximum wear point B, in FIG.
2.
[0024]

As shown in FIG. 1, the refractory lining 2 is partly melted linearly from the laser radiation
start point F along the lateral wall 12 of the shell 11, while the laser cutter 3 is moved from the
laser radiation start point F along the lateral wall 12 of the shell 11.
[0025]
In this way, in the second embodiment, a slit (void area) reaching the point H is formed in a
lateral wall 22 of the refractory lining 2 through the second laser radiation step. Alternatively, a
melted part of the refractory lining 2 is re-solidified, so that a part of the lateral wall 22 extending
from the laser radiation start point F to the point H is vitrified. Thus, a breaking-away barrier
(weakened area) I is formed in the lateral wall 22, as shown in FIG. 5(b).
In the case where the void area is formed as the breaking-away barrier I, the refractory lining
2 may be melted while gas is blown against an area of the refractory lining 2 through which a laser
beam has just passed, in the same manner as that in the first embodiment. Alternatively or
additionally, a plurality of holes each extending from an inner lateral surface 22a of the lateral wall
22 of the refractory lining 2 toward the shell 11 may be provided before cutting off a part of the
refractory lining 2 by using the laser cutter 3.
[0026]
In the second embodiment, the striking step comprises using a striking device 9 to apply a
striking force from the side of the inner lateral surface 22a of the refractory lining 2 to a region of
the refractory lining 2 influenced by the laser radiation in the second laser radiation step, i.e., a
region of the lateral wall 22 of the refractory lining 2 ranging from the inner lateral surface 22a to
the breaking-away barrier I, as shown in FIG. 5(b), thereby causing the region to break away, as
shown in FIG. 5(c). In the case where the vitrified area is formed as the breaking-away barrier I,
the vitrified area having a higher strength than the void area and brittleness can suppress the
transmission of the striking force applied to the refractory lining 2 by the striking device 9, so that
a region of the lateral wall 22 of the refractory lining 2 on the side of the shell 11 with respect to
the breaking-away barrier I is not damaged. This makes it possible to suppress damage of the
lateral wall 22.
[0027]
In the second embodiment, as shown in FIGS. 5 (d) to (g), the process from the second laser
radiation step to the striking step will be repeatedly performed over a range from the top end

surface 21 to an inner bottom surface 23. In this way, the lateral wall 22 of the refractory lining
2 is partly removed.
In the second embodiment, after completion of the striking step, the repair work conducting
step is performed in the same manner as that in the first embodiment. In the repair work
conducting step, after completion of the striking step, the mold form 6 is placed inside the blast
furnace trough 1, as shown in FIG. 3, and then the repairing material 7 is cast into an interspace
between an outer lateral surface 61 of the mold form 6 and the cutout surface 24 of the refractory
lining 2 after being subjected to the breaking-away in the striking step, thereby repairing this
refractory lining 2. Here, the repairing material 7 is the same as the refractory lining 2 in terms
of material composition.
As above, in the second embodiment, the second laser radiation step, the striking step and the
repair work conducting step are performed with respect to each of the pair of lateral walls 22 of
the refractory lining 2. This makes it possible to remove a part of each of the pair of lateral walls
22 of the refractory lining 2 on the inner side of the shell 11 of the blast furnace trough 1, and
recover the refractory lining 2 to its original state.
In the second embodiment, an area capable of triggering breaking-away of a part of the
refractory lining 2 can be formed by using the laser cutter 3 to melt a part of the refractory lining
2, and a striking force is applied toward the melted area having such a triggering feature, thereby
removing a part of the refractory lining 2, so that it becomes possible to remove a part of the
refractory lining 2 easily and quickly. In the second embodiment, an area to be melted is limited
to a part of the refractory lining 2, and thus a region of the refractory lining 2 in which a destruction
force is exerted upon striking is limited to a relatively narrow range, so that it becomes possible to
minimize a removal region of the refractory lining 2. This makes it possible to minimize the
amount of the repairing material 7 to be used, and keep repair costs down. In the second
embodiment, there is no need to set a melting range to reach the bottom surface 23, so that it
becomes possible to lower the laser power of the laser cutter 3.
[0028]
< Third Embodiment >
FIG. 6 conceptually illustrates a refractory lining repairing method according to a third
embodiment of the present invention.
The method according to the third embodiment comprises: a third laser radiation step of using

a laser cutter 3 to radiate a laser (laser beam) to a refractory lining 2, from one, or first, direction
in a vertical section orthogonal to each of a pair of opposed lateral walls 12 of a shell of a blast
furnace trough 1 (or a ladle), thereby melting a part of the refractory lining 2; a fourth laser
radiation step of using the laser cutter 3 to radiate a laser (laser beam) to the refractory lining 2,
from another, or second, direction in the vertical section orthogonal to the lateral wall 12 of the
shell 11, so as to cause a region of the refractory lining 2 influenced by the laser radiation in the
third laser radiation step to break away; and a repair work conducting step of conducting a repair
work of placing a mold form 6 inside the blast furnace trough 1 (or the ladle), and then casting a
repairing material 7 into an interspace between the mold form 6 and a cutout surface of the
refractory lining 2 after being subjected to the breaking-away in the fourth laser radiation step,
thereby repairing this refractory lining.
[0029]
In the third laser radiation step of the method according to the third embodiment, a laser beam
is radiated to the refractory lining 2 in a downward direction which is the first direction, in the
vertical section orthogonal to the lateral wall 12 of the shell 11, as shown in FIG. 6(a). More
specifically, a laser beam is irradiated from the laser cutter 3 in a direction from a laser radiation
start point F on a top end surface 21 of the refractory lining 2 toward a point H located inside the
refractory lining 2 and on a vertical section including the point F and orthogonally intersecting
with the lateral wall 12 of the shell 11. In this process, a laser power is preliminarily set to have
an intensity enough to melt the refractory lining 2 up to the point H located inside the refractory
lining 2.
As shown in FIG. 1, the refractory lining 2 is partly melted linearly from the laser radiation
start point F along the lateral wall 12 of the shell 11, while the laser cutter 3 is moved from the
laser radiation start point F along the lateral wall 12 of the shell 11.
In this way, in the third embodiment, a slit (void area) reaching the point H is formed in a
lateral wall 22 of the refractory lining 2 through the third laser radiation step. Alternatively, a
melted part of the refractory lining 2 is re-solidified, so that a part of the lateral wall 22 extending
from the laser radiation start point F to the point H is vitrified. Thus, a breaking-away barrier
(weakened area) I is formed in the lateral wall 22.
[0030]
Subsequently, in the fourth laser radiation step of the method according to the third

embodiment, a laser beam is radiated to the refractory lining 2 in an upward direction (more
specifically in an obliquely upward direction) which is the second direction, in the vertical section
orthogonal to the lateral wall 12 of the shell 11, as shown in FIG. 6(b). More specifically, a laser
beam is irradiated in an upward direction from a position below the breaking-away barrier I formed
in the refractory lining 2 in the third laser radiation step toward the breaking-away barrier I to melt
a part of the refractory lining 2, thereby causing a region of the lateral wall 22 of the refractory
lining 2 ranging from an inner lateral surface 22a of the lateral wall 22 to the breaking-away barrier
I to break away. Since a part of the lateral wall 22 of the refractory lining 2 facing the breaking-
away barrier I and only partially connecting to the remaining part of the lateral wall 22 due to the
melting in the third laser radiation step is already in an easily breakable state, the refractory lining
2 can be partly broken away in conformity to the breaking-away barrier I by the laser radiation in
the fourth laser radiation step, as shown in FIG. 6(c), without being unnecessarily damaged. This
makes it possible to suppress damage of the lateral wall 22.
[0031]
In the third embodiment, as shown in FIGS. 6 (a) to (c), the process from the third laser
radiation step to the fourth laser radiation step will be repeatedly performed over a range from the
top end surface 21 to an inner bottom surface 23. In this way, the lateral wall 22 of the refractory
lining 2 is partly removed.
In the third embodiment, after completion of the fourth laser radiation step, the repair work
conducting step is performed in the same manner as that in the first embodiment. In the repair
work conducting step, after completion of the fourth laser radiation step, the mold form 6 is placed
inside the blast furnace trough 1, as shown in FIG. 3, and then the repairing material 7 is cast into
an interspace between an outer lateral surface 61 of the mold form 6 and the cutout surface 24 of
the refractory lining 2 after being subjected to the breaking-away in the fourth laser radiation step,
thereby repairing this refractory lining 2. Here, the repairing material 7 is the same as the
refractory lining 2 in terms of material composition.
As above, in the third embodiment, the third laser radiation step, the fourth laser radiation
step and the repair work conducting step are performed with respect to each of the pair of lateral
walls 22 of the refractory lining 2. This makes it possible to remove a part of each of the pair of
lateral walls 22 of the refractory lining 2 on the inner side of the shell 11 of the blast furnace trough
1, and recover the refractory lining 2 to its original state.

In the third embodiment, an area capable of triggering breaking-away of a part of the
refractory lining 2 can be formed by using the laser cutter 3 to melt a part of the refractory lining
2 in the downward direction, and then a laser beam is radiated in the upward direction toward the
melted area having such a triggering feature, thereby removing a part of the refractory lining 2, so
that it becomes possible to remove a part of the refractory lining 2 easily and quickly. In the third
embodiment, an area to be melted is limited to a part of the refractory lining 2, and thus a region
of the refractory lining 2 in which a destruction force is exerted upon laser radiation is limited to
a relatively narrow range, so that it becomes possible to minimize a removal region of the
refractory lining 2. This makes it possible to minimize the amount of the repairing material 7 to
be used, and keep repair costs down. In the third embodiment, there is no need to set a melting
range to reach the bottom surface 23, so that it becomes possible to lower the laser power of the
laser cutter 3.
In the third embodiment, the first direction is set to the downward direction, and the first
direction is set to the upward direction. However, the present invention is not limited thereto, but
the downward and upward directions may be interchanged. In other words, in the third
embodiment, the fourth laser radiation step may be performed prior to the third laser radiation step.
LIST OF REFERENCE SIGNS
[0032]
1: blast furnace trough
11: shell
12: lateral wall of shell
2: refractory lining
21: top end surface of refractory lining
22: lateral wall of refractory lining
22a: inner lateral surface of refractory lining
23: inner bottom surface of refractory lining
24: cutout surface
3: laser cutter
3a: radiation part of laser cutter
4: robot arm

5: control unit
6: mold form
7: repairing material
8: hose
9: striking device

1. A method of repairing a refractory lining on an inner side of a shell of a ladle or a trough,
comprising:
a first laser radiation step of using a laser cutter to radiate a laser to the refractory lining,
thereby cutting off a part of the refractory lining; and
a repair work conducting step of conducting a repair work of placing a mold form inside the
ladle or the trough, and then casting a repairing material into an interspace between the mold form
and a cutout surface of the refractory lining after being subjected to the cutting-off in the first laser
radiation step, thereby repairing said refractory lining.
2. A method of repairing a refractory lining on an inner side of a shell of a ladle or a trough,
comprising:
a second laser radiation step of using a laser cutter to radiate a laser to the refractory lining,
thereby melting a part of the refractory lining;
a striking step of applying a striking force to a region of the refractory lining influenced by
the laser radiation in the second laser radiation step, thereby causing the region to break away; and
a repair work conducting step of conducting a repair work of placing a mold form inside the
ladle or the trough, and then casting a repairing material into an interspace between the mold form
and a cutout surface of the refractory lining after being subjected to the breaking-away in the
striking step, thereby repairing said refractory lining.
3. A method of repairing a refractory lining on an inner side of a shell of a ladle or a trough,
comprising:
a third laser radiation step of using a laser cutter to radiate a laser to the refractory lining,
from one direction in a vertical section orthogonal to a lateral wall of the shell, thereby melting a
part of the refractory lining;
a fourth laser radiation step of using a laser cutter to radiate a laser to the refractory lining,
from another direction in the vertical section orthogonal to the lateral wall of the shell, so as to

cause a region of the refractory lining influenced by the laser radiation in the third laser radiation
step to break away; and
a repair work conducting step of conducting a repair work of placing a mold form inside the
ladle or the trough, and then casting a repairing material into an interspace between the mold form
and a cutout surface of the refractory lining after being subjected to the breaking-away in the fourth
laser radiation step, thereby repairing said refractory lining.
4. The method as claimed in any one of claims 1 to 3, wherein the laser radiation by the laser cutter
is performed in a direction along a straight line D connecting a point B where wear of the refractory
lining on the lateral wall of the shell reaches a position closest to the lateral wall of the shell, and
a point C where a bottom surface of the refractory lining intersects an inner lateral surface of the
refractory lining on the lateral wall of the shell, in the vertical section orthogonal to the lateral wall
of the shell.
5. The method as claimed in claim 4, wherein the laser radiation by the laser cutter is performed
after providing a plurality of holes each extending from the inner lateral surface of the refractory
lining toward the straight line D.
6. The method as claimed in any one of claims 1 to 3, wherein a laser is radiated to the refractory lining, while gas is blown against an area of the refractory lining through which the laser has just
passed.