JP7501683B2 - Dummy bar for continuous casting machine and method for changing thickness of dummy bar for continuous casting machine - Google Patents

Description

The present invention relates to a dummy bar for a continuous casting machine that is used when starting casting in the continuous casting machine and a method for changing the thickness of the dummy bar for a continuous casting machine.

In the continuous steel casting process, a dummy bar (guide rod) is used to keep the poured molten steel in the mold internal space when pouring begins. There are two types of dummy bars: one is called a solid dummy bar, and the other is called a link dummy bar. A solid dummy bar is a rigid body with a fixed shape and is used in small continuous casting machines such as billet continuous casting machines. On the other hand, a link dummy bar is used in large continuous casting machines such as slab continuous casting machines and bloom continuous casting machines.

The structure of this link-type dummy bar (hereinafter also referred to simply as "dummy bar") is shown in Figure 1 (Figure 1(A) is a schematic plan view, and Figure 1(B) is a schematic side view). The dummy bar 51 is configured so that many steel links 54 are connected by link pins 55, and each link 54 is bent around the link pin 55 as an axis to form an arc or straight line along the strand of the continuous casting machine (the part with many links is called the "dummy bar body"). A dummy bar head 53, which is inserted into the mold to form the temporary bottom of the mold, is connected to the upper side of the dummy bar body 52 by a connecting pin 56, thereby forming the dummy bar 51 for the continuous casting machine.

When casting begins, the dummy bar advances through the strand of the continuous casting machine while being held in place by the pressing force of multiple pinch rolls installed on the strand. Therefore, when the dummy bar is used repeatedly, the pressing force of the pinch rolls causes the links in the dummy bar to deform and become thinner. When the thickness of the links falls below the stroke of the pinch rolls, it becomes difficult for the pinch rolls to hold the dummy bar, so the thickness of each link of the dummy bar is measured periodically, and any links that are thicker than the specified value are removed and replaced.

However, depending on the deformation of a link, it may interfere with adjacent links (contact state of deformed burrs caused by deformation, etc.), making it difficult to remove only the deformed link. In such cases, links that do not need to be replaced may also be replaced, resulting in problems such as longer work hours and higher repair costs. Furthermore, with the demand for thick slab cast pieces increasing in recent years, there is often consideration of modifying continuous casting machines to increase the casting thickness. In this case, it is necessary to manufacture a new dummy bar in its entirety to match the increased casting thickness.

To solve these problems, Patent Document 1 proposes a dummy bar in which a thickness adjustment member is replaceably attached to the dummy bar body so that the thickness of the dummy bar head and the dummy bar body can be made the same. Patent Document 2 also proposes a dummy bar in which a mating groove is provided in each link, and a liner is inserted into this mating groove so that it protrudes above the link surface to adjust the thickness, and if the thickness becomes insufficient due to the pressing force of the pinch rolls, only that liner is replaced.

Japanese Utility Model Application Publication No. 48-57513 JP 2013-754 A

However, the above conventional technology has the following problems:

In other words, with the dummy bar proposed in Patent Document 1, if the thickness adjustment member is deformed and burrs or the like are generated, the burrs or the like can eliminate the gaps between adjacent links, causing the links to interfere with each other, making it impossible to replace the thickness adjustment member as intended without removing the links.

The problem with the dummy bar proposed in Patent Document 2 is that the cost of machining the mating grooves into the links of the dummy bar is very expensive.

The present invention was made in consideration of the above circumstances, and its purpose is to provide a dummy bar for a continuous casting machine and a method for changing the thickness of a dummy bar for a continuous casting machine that can change the thickness of the dummy bar without causing interference with adjacent links when the dummy bar body is no longer able to maintain the specified thickness due to deformation caused by the pressing force of the pinch rolls, and that can realize a configuration that allows the thickness to be changed at low cost.

The gist of the present invention to solve the above problems is as follows:

[1] A dummy bar for a continuous casting machine, comprising a dummy bar body having multiple links and a dummy bar head connected to the upper part of the dummy bar body, the links being provided with keyways on the side parallel to the casting direction of the continuous casting machine and with bolt screw holes on the top surface on the side where the pinch rolls are located, and an L-shaped attachment having a connection key inserted into the keyway and a bolt insertion hole through which a bolt fitted into the bolt screw hole is inserted passes through the bolt insertion hole and is removably attached to the link by a bolt that fits into the bolt screw hole, surrounding the side surface on which the keyway is provided and the top surface on which the bolt screw hole is provided.

[2] A method for changing the thickness of a dummy bar for a continuous casting machine as described in [1], which involves preparing two or more types of attachments with different upper piece thicknesses of the upper piece portion in which the bolt insertion holes are provided, loosening the bolts to remove the attachments attached to the link, and attaching an attachment with an upper piece portion in which the bolt insertion holes are provided and a different upper piece thickness from the removed attachment to the link by fitting the bolts, thereby changing the thickness of the dummy bar for a continuous casting machine.

The present invention makes it possible to change the thickness of the dummy bar without causing interference with adjacent links, and to realize a configuration that allows the thickness to be changed at low cost.

1A and 1B are schematic diagrams of a conventional dummy bar, in which FIG. 1A is a schematic plan view and FIG. 1B is a schematic side view. 2A and 2B are schematic diagrams showing an example of a dummy bar for a continuous casting machine according to the present invention, in which FIG. 2A is a schematic plan view and FIG. 2B is a schematic side view. 3A is a schematic plan view of an attachment used in a dummy bar for a continuous casting machine according to the present invention, FIG. 3B is a schematic front view, and FIG. 3C is a schematic side view. 4A is a schematic plan view showing a state in which an attachment is attached to a link on a dummy bar body, FIG. 4B is a schematic front view, and FIG. 4C is a schematic side view. FIG. 4 is a schematic plan view showing another example of a dummy bar for a continuous casting machine according to the present invention. FIG. 4 is a schematic plan view showing another example of an attachment used in the dummy bar for a continuous casting machine according to the present invention.

An example of an embodiment of the present invention will be described in detail below with reference to the drawings. Figure 2 is a schematic diagram showing an example of a dummy bar for a continuous casting machine according to the present invention. Figure 2(A) shows a schematic plan view of a dummy bar for a continuous casting machine. Figure 2(B) shows a schematic side view of a dummy bar for a continuous casting machine.

As shown in FIG. 2, the dummy bar 1 for a continuous casting machine according to the present invention has a dummy bar body 2 having a plurality of steel links 4, and a steel dummy bar head 3 connected to the upper part of the dummy bar body 2. Each link 4 is connected by a steel link pin 5, and is configured to bend freely around the link pin 5 as an axis. The dummy bar body 2 and the dummy bar head 3 are connected by a steel connecting pin 6, and are configured to bend freely around the connecting pin 6 as an axis.

Before the start of continuous casting, the upper side of the dummy bar head 3 of the dummy bar 1 for a continuous casting machine (hereinafter referred to as the "dummy bar 1") is inserted into the bottom of the mold (not shown) of the continuous casting machine. Then, the dummy bar body 2 is inserted into the strand of the continuous casting machine so that it is located within the strand of the continuous casting machine. At this time, the dummy bar body 2 is held by at least a pair of pinch rolls (not shown) installed in the continuous casting machine. After that, molten metal such as molten steel is poured into the mold, and when a predetermined amount of molten metal has accumulated in the mold, the pinch rolls are driven to pull the dummy bar 1 below the mold (the casting direction K of the continuous casting machine), and continuous casting of the molten metal begins. Note that FIG. 2 shows only a portion of the dummy bar body 2.

An attachment 7 is attached to the link 4. Specifically, in this embodiment, as shown in FIG. 2(A), the attachment 7 is attached to the link 4 located on the outermost side of the dummy bar body 2 in the dummy bar width direction L perpendicular to the casting direction K.

Here, a pair of pinch rolls that hold the dummy bar 1 and are driven to pull the dummy bar 1 along the casting direction K are positioned at the front and rear of the drawing in FIG. 2(A) so as to sandwich the dummy bar 1. In other words, the attachment 7 attached to the link 4 is directly subjected to the rolling force of the pinch rolls.

Next, the attachment 7 attached to the link 4 of the dummy bar 1 according to the present invention will be described with reference to Figure 3. Figure 3 shows a schematic diagram of the attachment 7 used in the dummy bar 1 according to the present invention. Regarding the configuration of the attachment 7, Figure 3(A) shows a schematic plan view, Figure 3(B) shows a schematic front view, and Figure 3(C) shows a schematic side view.

The attachment 7 has an upper piece 7a and a side piece 7s. The upper piece 7a has a bolt insertion hole 7b. The side piece 7s has a connection key 7t. As shown in FIG. 3(B), the attachment 7 is configured so that the upper piece 7a and the side piece 7s form an L-shape when viewed from the front. The attachment 7 may be configured to be L-shaped by connecting the steel material that constitutes the upper piece 7a and the side piece 7s by welding or the like. The attachment 7 may also be configured so that the upper piece 7a and the side piece 7s are integrally formed by forging or the like. The attachment 7 may be made of steel.

Here, the "upper piece thickness" in the present invention corresponds to the upper piece thickness M shown in FIG. 3(B). The direction of the dimension of the upper piece thickness M is the same as the direction in which the attachment 7 is sandwiched between the pair of pinch rolls described above.

Next, the state in which the attachment 7 is attached to the link 4 will be described using FIG. 4. FIG. 4 shows a schematic diagram of the state in which the attachment 7 is attached to the link 4. With respect to the state in which the attachment 7 is attached to the link 4, FIG. 4(A) shows a schematic plan view, FIG. 4(B) shows a schematic front view, and FIG. 4(C) shows a schematic side view. Here, FIG. 4(A) corresponds to an enlarged view of the configuration in which the attachment 7 is attached to the link 4, included in FIG. 2(A).

As shown in FIG. 4, the link 4 has a key groove 4a and a bolt screw hole 4b. The key groove 4a is provided on the side surface 4d of the link 4. The bolt screw hole 4b is provided on the top surface 4c of the link 4. That is, the link 4 has the key groove 4a provided on the side surface 4d parallel to the casting direction K, and the bolt screw hole 4b provided on the top surface 4c on the side where the pinch roll is located.

When attaching the attachment 7 to the link 4, first, the connection key 7t on the side piece 7s of the attachment 7 is inserted into the key groove 4a on the side surface 4d of the link 4. In other words, the side surface 4d of the link 4 comes into contact with the side piece inner surface 7u of the side piece 7s of the attachment 7. At this time, as shown in FIG. 4(B), the upper surface 4c of the link 4 comes into contact with the upper piece lower surface 7c of the upper piece 7a of the attachment 7. Then, the attachment 7 is attached to the link 4 by fitting the bolt 8, which has been inserted through the bolt insertion hole 7b, into the bolt screw hole 4b of the link 4 and tightening it.

For this reason, the attachment 7 is attached in contact with the top surface 4c (the top surface on which the pinch roll is located) and side surface 4d (the side surface parallel to the casting direction K and perpendicular to the dummy bar width direction L) of the link 4 on the dummy bar body 2. In other words, the attachment 7 is removably attached so as to surround the top surface 4c and side surface 4d of the link 4.

Here, the link 4 has a link thickness N, as shown in FIG. 4(B). The direction of the dimension of the link thickness N is the direction in which the attachment 7 is pinched by the pair of pinch rolls described above, and the same direction as the dimension of the upper piece thickness M of the attachment 7. In other words, by attaching the attachment 7 to the link 4, the thickness P of the dummy bar main body 2 becomes the sum of the upper piece thickness M and the link thickness N.

As shown in the schematic plan view of FIG. 4(A), the area of the upper arm portion 7a of the attachment 7 is smaller than the area of the upper surface 4c of the link 4. Therefore, even if deformation burrs or the like occur on the upper arm portion 7a of the attachment 7 due to repeated contact of the pinch roll with the upper arm portion 7a, the deformation burrs or the like can be prevented from protruding outside the upper surface 4c of the link 4.

As shown in FIG. 2, the attachments 7 are attached to the links 4 at both ends of the dummy bar body 2 in the dummy bar width direction L, which is a direction perpendicular to the casting direction K. In other words, the attachments 7 are removably attached to the outermost edge of the dummy bar body 2 extending in the casting direction K in the dummy bar width direction L. This allows workers to easily and quickly replace the attachments.

As shown in FIG. 2(A), the links 4 in the dummy bar body 2 are arranged in a staggered pattern in the casting direction K. Therefore, the links 4 at the outermost edges in the width direction L of the dummy bar are arranged at intervals from each other along the casting direction K. Therefore, by attaching the attachments 7 to the links 4 arranged at intervals from each other, even if a deformed burr occurs on the attachment 7 due to the rolling force of the pinch roll, it is possible to prevent contact between adjacent attachments 7 due to the deformed burr.

The only machining required for the dummy bar body 2 is to create key grooves 4a and bolt screw holes 4b in the links 4. Therefore, compared to the method of Patent Document 2, which creates mating grooves, machining can be done at a lower cost, and the required initial investment can be reduced.

As shown in Figure 2, the attachments 7 are attached to the links 4 at the extreme ends on both sides of the dummy bar width direction L, over the entire length of the dummy bar body 2 along the casting direction K. The attachments 7 are attached to the extreme ends on both sides of the dummy bar body 2 in order to maintain balance so that the rolling force from the pinch rolls is symmetrical (even) in the dummy bar width direction L.

The frictional force generated by contact with the pinch roll does not depend on the area of the contact surface. Therefore, even if the attachments 7 are attached only to the links 4 at the extreme ends on both sides of the dummy bar in the width direction L, that is, the attachments 7 are not attached to the links 4 in the center of the dummy bar in the width direction L, the frictional force from the pinch roll acting on the dummy bar 1 does not change.

Conventionally, it has been thought that the dummy bar 1 is mainly subjected to a pull-out force, but when the pull-out resistance due to the ferrostatic pressure of the molten steel is calculated, it is found that the falling force due to the weight of the dummy bar 1 is greater, and the force actually acting on the dummy bar 1 is the holding force that supports the dummy bar 1 so that it does not fall. Calculating this force, it was found that the connection key 7t and bolt 8 are sufficient for attaching the attachment 7 to the link 4.

For example, consider the case where, in a continuous slab casting machine equipped with a mold 0.8 m long, the dummy bar head 3 approaches the mold outlet after the start of casting. The ferrostatic pressure of the molten steel γ is 0.7 kg/ ^cm2 /m, the coefficient of friction inside the mold μ[-] (dimensionless number) is 0.4, and the length L, thickness H, and width B of the mold are 0.8 m, 0.22 m, and 1.9 m, respectively. The mold withdrawal resistance R due to the ferrostatic pressure in an infinitesimal section Δx, a distance x from the upper end of the mold, can be expressed as R = μ x [{2 x (H + B) x Δx} x (γ x)]. By integrating this over the mold length with respect to the distance x, the mold withdrawal resistance R becomes approximately 4 tons.

On the other hand, the weight of the dummy bar 1 is about 10 tons, and if the weight of the slab (molten steel) itself in the mold is added to this, the total weight of the dummy bar 1 and the slab is about 12 tons. Therefore, the total weight is about 8 tons greater than the mold withdrawal resistance of about 4 tons.

In other words, the force acting on the dummy bar 1 is the holding force required to withstand a drop force of approximately 8 tons. Considering the worst case scenario, if the dummy bar 1 is supported by only a pair of pinch rolls, the two attachments 7 will support a load of approximately 8 tons, meaning that each attachment will be subjected to a load of approximately 4 tons. To withstand this load, if the connection key 7t is made of SS400, it will require a connection key 7t that is 15 mm thick, 20 mm wide, and 25 mm long (thickness is the dimension in the thickness direction of the dummy bar, width is the dimension in the depth direction of the groove, and length is the dimension in the casting direction). Since the load is basically received by the connection key 7t, the bolt 8 only needs to have a strength sufficient to prevent it from coming loose. For example, it would be sufficient to use an M16 bolt 8 with a strength classification of 4.6.

The attachments 7 can be replaced individually, so that only the attachments 7 for which the upper piece thickness M has been found to be insufficient due to the pressing force of the pinch rolls can be replaced. In addition, each attachment 7 is sufficiently distant from the adjacent attachments 7, so that a situation does not occur in which an attachment 7 that does not need to be replaced due to interference with the adjacent attachment 7 due to deformation. Naturally, there is no need to remove the link pins 5 and disassemble each link 4.

In addition, when it becomes necessary to increase the thickness P of the dummy bar 1 in conjunction with the modification to increase the casting thickness of the continuous casting machine, there is no need to completely replace the link 4 or perform new processing, and it is possible to deal with this by simply replacing the upper piece portion 7a of the attachment 7 with an attachment having a thicker upper piece portion thickness M. In addition, if there are two or more types of attachments with different upper piece portion thicknesses M of the upper piece portion 7a, when increasing or decreasing the casting thickness of the continuous casting machine, it is possible to deal with the increase or decrease in the casting thickness of the continuous casting machine by loosening the bolt 8 to remove the attached attachment, attaching an attachment with a different upper piece portion thickness M of the upper piece portion 7a by tightening the bolt 8, and simply replacing the attachment. In this method of changing the thickness of the dummy bar, two or more types of dummy bar heads 3 with thicknesses corresponding to the casting thickness are prepared, and a dummy bar head having a thickness corresponding to the thickness of the dummy bar body 2 is attached to the dummy bar body 2 by the connecting pin 6.

In the embodiment shown in FIG. 2, the attachments 7 are not attached to the central link 4 of the dummy bar body 2 and to the links 4 between the central link 4 and the links 4 at the extreme edges on both sides in the dummy bar width direction L. Furthermore, as described above, the links 4 in the dummy bar body 2 are arranged in a staggered pattern in the casting direction K. In other words, there are intermittent sections in the casting direction K where the attachments 7 are not attached. As a result, the thickness of the dummy bar body 2 is thinner in some sections of the casting direction K of the dummy bar body 2.

In addition, multiple pairs of pinch rolls are provided, and the installation position of the pinch rolls varies depending on each continuous casting machine. Depending on the installation position conditions of the pinch rolls, in such cases, there may be concerns about the holding force of the pinch rolls to the dummy bar 1. For example, this may be the case when the pitch of the casting direction K in the range where the attachment 7 is not attached matches the pitch of the casting direction K at the installation position of the pinch rolls.

Therefore, as shown in FIG. 5, the attachment 7 can also be attached to the link 4 between the center of the width and the outermost part on both sides in the width direction L of the dummy bar. In this case, the thickness of the dummy bar body 2 is the same in the casting direction K, and the holding force of the pinch roll on the dummy bar 1A for the continuous casting machine is constant across the casting direction K. FIG. 5 is a schematic plan view showing another example of a dummy bar for a continuous casting machine according to the present invention.

Here, the configuration of attachment 7A, which is another example of attachment 7, with a recess 7e provided on the surface of upper piece 7a will be described with reference to FIG. 6. FIG. 6 is a diagram showing a schematic diagram of attachment 7A with a recess 7e provided on the surface of upper piece 7a. FIG. 6 shows a schematic plan view of attachment 7A.

As shown in FIG. 6, the attachment 7A may be configured with a recess 7e on the surface of the upper piece upper surface 7d, which is the contact surface of the upper piece portion 7a with the pinch roll. By providing the recess 7e on the surface of the upper piece upper surface 7d, it is possible to increase the frictional force generated by contact between the attachment 7A and the pinch roll. The increase in the frictional force between the attachment 7A and the pinch roll leads to improved holding force of the dummy bar 1 in the strand of the continuous casting machine and improved movement control in the casting direction K.

The recess 7e may be a circular depression cut in a direction perpendicular to the casting direction K. The recess 7e may have a depth of 0.1 to 10.0 mm and a diameter of 0.1 to 20.0 mm. It is more preferable that the recess 7e has a depth of 1.0 to 5.0 mm and a diameter of 1.0 to 10.0 mm. The recess 7e may be provided at multiple locations on the surface of the upper piece upper surface 7d. The multiple recesses 7e on the surface of the upper piece upper surface 7d may be provided at intervals of 0.0 to 20.0 mm from each other, and preferably at intervals of 1.0 to 10.0 mm. The recess 7e may be provided on the entire surface of the upper piece upper surface 7d, or may be provided on a portion of the upper piece upper surface 7d. The recesses 7e provided at multiple locations on the surface of the upper piece upper surface 7d do not need to be provided at multiple locations in a fixed arrangement pattern, and multiple recesses 7e may be provided overlapping each other. The recesses 7e shown in FIG. 6 are provided in a number of places on the surface of the upper piece upper surface 7d in a certain arrangement pattern, and are an example of a configuration provided on the entire surface of the upper piece upper surface 7d. The recesses 7e may be provided on the surface of the upper piece upper surface 7d by processing using a tool such as a hammer, and as long as it is possible to provide the recesses 7e on the surface of the upper piece upper surface 7d, there is no need to be limited to any particular processing method. In addition, when casting is performed in a continuous casting machine, if the attachment 7A is not attached to the link 4, the link 4 and the dummy bar head 3 can also be processed to provide recesses 7e, thereby improving the holding force of the dummy bar 1 in the strand and the movement control in the casting direction K.

As described above, according to the present invention, the connection key 7t of the attachment 7 is inserted into the key groove 4a of the link 4 of the dummy bar body 2, and the attachment 7 and the link 4 are connected with the bolt 8 passing through the bolt insertion hole 7b, so that the attachment 7 can be easily attached to the link 4 and easily removed. If the attachment 7 is deformed and the thickness of the dummy bar body 2 is reduced, the thickness of the dummy bar body 2 can be restored to its original thickness simply by replacing the attachment 7. In addition, if multiple types of attachments 7 with different upper piece thicknesses M of the upper piece parts 7a of the attachments 7 are prepared, the thickness of the dummy bar body 2 can be quickly changed by replacing the attachments 7 with attachments 7 with different upper piece thicknesses M of the upper piece parts 7a of the attachments 7. Furthermore, since the machining of the links 4 of the dummy bar body 2 is only the machining of the key grooves 4a and the bolt screw holes 4b, the thickness of the dummy bar body 2 can be restored or changed inexpensively.

A dummy bar with an attachment, as shown in Figure 2, was manufactured by machining each link of a dummy bar of an existing continuous slab casting machine to provide bolt screw holes and keyways. A comparison was then made with a dummy bar with an attachment, as shown in Figure 2, in which each link was machined to provide mating grooves as disclosed in Patent Document 2. In both cases, the links and attachments were made of structural carbon steel (S45C).

The cost of modifying each link to provide bolt screw holes and keyways was half the cost of machining to provide mating grooves. In other words, by applying this invention, we were able to significantly reduce initial investment.

The manufactured dummy bar shown in Figure 2 was used for one year in a continuous slab caster that uses dummy bars once a day on average. As a result, the upper part of the attachment lost 0.6 mm in thickness due to the rolling force of the pinch rolls. Calculating the change in the amount of loss over time based on this loss, it was found that the upper part of the attachment would lose its thickness below the specified value in about 14 years.

When using this value to predict the repair costs per year, it was estimated that the repair costs required for the dummy bar when this invention is applied will be about 1/4 of the cost required when machining is performed to provide mating grooves in each link as disclosed in Patent Document 2.

REFERENCE SIGNS LIST 1, 1A Dummy bar for continuous casting machine 2 Dummy bar body 3 Dummy bar head 4 Link 4a Key groove 4b Bolt screw hole 4c Top surface 4d Side surface 5 Link pin 6 Connecting pin 7, 7A Attachment 7a Upper piece 7b Bolt insertion hole 7c Lower surface of upper piece 7d Upper surface of upper piece 7e Recess 7s Side piece 7t Connecting key 7u Inner surface of side piece 8 Bolt K Casting direction L Dummy bar width direction M Upper piece thickness N Link thickness P Thickness

Claims (2)

A dummy bar for a continuous casting machine, comprising: a dummy bar body having a plurality of links; and a dummy bar head connected to an upper portion of the dummy bar body,
The link has a key groove on a side surface parallel to the casting direction of the continuous casting machine, and a bolt screw hole on an upper surface on the side where the pinch rolls are located,
a dummy bar for a continuous casting machine, the dummy bar having an L-shaped attachment having a connection key that is inserted into the key groove and a bolt insertion hole through which a bolt that fits into the bolt screw hole is inserted, the L-shaped attachment passing through the bolt insertion hole and being removably attached to the link so as to surround the side surface on which the key groove is provided and the top surface on which the bolt screw hole is provided by a bolt that fits into the bolt screw hole. A method for changing the thickness of a dummy bar for a continuous casting machine according to claim 1,
Two or more types of the attachments are prepared, each having an upper piece portion having a different thickness, the upper piece portion having the bolt insertion hole provided therein;
Loosen the bolt to remove the attachment attached to the link;
A method for changing the thickness of a dummy bar for a continuous casting machine, in which an attachment having a thickness different from the removed attachment is attached to the link by fitting the bolt, the attachment having a thickness of an upper piece portion in which the bolt insertion hole is provided, thereby changing the thickness of the dummy bar for a continuous casting machine.

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