JP7004085B2 - Mold for continuous steel casting and continuous steel casting method - Google Patents

Description

The present invention relates to a mold for continuous casting in which the number of times the mold is used is improved as compared with the prior art while preventing cracks on the surface of the slab due to non-uniform cooling of the solidified shell, and the steel using the mold for continuous casting. Regarding the continuous casting method.

In continuous steel casting, the molten steel injected into the mold is cooled by a water-cooled mold, and the molten steel solidifies at the contact surface with the mold to form a solidified layer (referred to as a "solidified shell"). A slab having this solidified shell as an outer shell and an unsolidified molten steel inside is continuously supported by a slab support roll provided below the mold and continuously cooled by a water spray or an air-water spray to the lower part of the mold. Steel slabs are manufactured by drawing and solidifying to the center.

When the cooling of the solidified shell in the mold becomes non-uniform, the thickness of the solidified shell becomes non-uniform in the slab drawing direction and the mold width direction. Stress caused by shrinkage and deformation of the solidified shell itself acts on the solidified shell. This stress is concentrated on the thin part of the solidified shell, and the concentrated stress causes cracks on the surface of the solidified shell at the initial stage of solidification. This crack expands due to external forces such as subsequent thermal stress, bending stress of the continuous casting machine, and straightening stress, and becomes a large surface crack. Surface cracks in the slab become surface defects in the steel product in the hot rolling process of the next step. Therefore, in order to prevent the occurrence of surface defects in steel products, it is necessary to melt or grind the surface of the slab to remove the surface cracks at the slab stage.

Non-uniform solidification in the mold is particularly likely to occur in steels with a carbon content of 0.08 to 0.17% by mass (referred to as "medium carbon steel"). In medium carbon steel, a peritectic reaction occurs during solidification. The non-uniform solidification in the mold is considered to be caused by the transformation stress due to the volume shrinkage during the transformation from δ iron (ferrite) to γ iron (austenite) due to the peritectic reaction. That is, the solidified shell is deformed by the strain caused by the transformation stress during the peritectic reaction, and this deformation causes the solidified shell to separate from the inner wall surface of the mold. Cooling by the mold is reduced at the portion away from the inner wall surface of the mold, and the thickness of the solidified shell at the portion away from the inner wall surface of the mold is reduced. It is considered that when the solidified shell thickness becomes thin, the above stress is concentrated on this portion and surface cracking occurs.

Therefore, many proposals have been made for the purpose of preventing cracks on the surface of steel slabs accompanied by a peritectic reaction. For example, in Patent Document 1, a plurality of parts having different thermal conductivity from the copper alloy constituting the mold plate (also referred to as “mold copper plate”) are independently formed on the inner wall surface of the mold. A mold for continuous casting having a dissimilar material filling part has been proposed. Patent Document 1 describes that by using this mold, surface cracking of the slab due to non-uniform cooling of the solidified shell at the initial stage of solidification can be effectively prevented. In particular, it is described that surface cracking of slabs due to non-uniform solidification shell thickness due to transformation from δ iron to γ iron in medium carbon steel accompanied by austenite reaction can be effectively prevented. There is.

Japanese Unexamined Patent Publication No. 2017-39165

In the mold for continuous casting of steel described in Patent Document 1, since a dissimilar substance filling portion, which is a material different from that of the mold plate, is formed on the mold plate, the thermal expansion rate is different between the mold plate and the dissimilar substance filling portion. Unlike these boundaries, thermal stress tends to concentrate. As a result, the mold surface is prone to cracking. Further, Patent Document 1 states that it is preferable to provide a plating layer on the inner wall surface of the mold for covering the dissimilar substance-filled portion for the purpose of suppressing cracking of the mold surface due to thermal history, thereby extending the life of the mold. It is possible to plan. However, even if a plating layer is provided on the inner wall surface of the mold, there is still a difference in thermal stress between the mold plate and the dissimilar substance filling portion, and the mold on which the dissimilar substance filling portion is formed tends to have a short service life. It is in. That is, there is a demand for a technique for extending the service life of the mold described in Patent Document 1.

The present invention has been made in view of the above circumstances, and an object thereof is to significantly reduce the number of times the mold is used in a mold for continuous casting of steel in which a dissimilar substance filling portion is formed as compared with the prior art. It is to provide a mold for continuous casting which can be extended. Another object of the present invention is to provide a method for continuously casting steel using the continuous casting mold.

The present inventors have diligently studied to solve the above-mentioned problems. As a result, it is possible to increase the heat transfer coefficient between the cooling water channel corresponding to the region where the dissimilar substance filling portion is formed and the water flow passing through the cooling flow path, and effectively remove heat from the mold plate in the region. We obtained the finding that it is effective. This is because the temperature of the dissimilar substance filling part and the mold plate is lowered by effectively removing heat from the mold plate in the region where the dissimilar substance filling part is formed, whereby the boundary portion between the mold plate and the dissimilar substance filling part is formed. By reducing the thermal stress of.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] A copper alloy mold plate having a mold inner wall surface formed on the front surface and a cooling water channel formed on the back surface.
A mold for continuous casting of steel comprising a backup plate attached to the mold plate so as to cover the cooling water channel.
In the recess formed on the surface of the mold plate at least in the region containing the meniscus, a heterogeneous substance filling portion filled with a heterogeneous substance having a thermal conductivity different from that of the mold plate is formed.
The cooling water channel on the back surface of the mold plate corresponding to the region where the dissimilar substance filling portion is formed is formed with a water flow disturbing portion that disturbs the water flow and increases the surface area of the cooling water channel. Casting mold.
[2] The above-mentioned [1], wherein a plurality of the water flow disturbing portions are arranged along the flow direction of the water flow and are composed of protrusions extending in the mold width direction of the cooling water channel and the thickness direction of the cooling water channel. Mold for continuous casting of steel.
[3] The mold for continuous casting of steel according to the above [1], wherein the water flow disturbing portion is composed of a plurality of protrusions arranged in a staggered arrangement in the cooling water channel.
[4] The dissimilar substance filling portion includes a plurality of circular recesses or pseudo-circular recesses, and is formed in a plurality.
In the region from the upper end to the lower end of the plurality of dissimilar substance filling portions on the surface of the mold plate, the plurality of dissimilar substances so that the heat flux on the inner wall surface of the mold from the inner wall surface of the mold to the cooling water channel changes periodically. The mold for continuous casting of steel according to any one of the above [1] to [3], wherein a material filling portion is formed.
[5] The above-mentioned [4], wherein the dissimilar substance filling portion and the cooling water channel are formed so as to satisfy at least one of the following equations (1) to (3). Mold for continuous casting of steel.
d <P ≦ S ……… (1)
e ≦ L ≦ 1000 × Vc / f ……… (2)
F ≤ L ……… (3)
Here, in the equations (1) to (3), each symbol represents the following.
d; Width of dissimilar substance filling portion in the mold width direction (mm)
P; Spacing distance (mm) in the mold width direction between adjacent parts filled with different substances
S; Spacing distance (mm) in the mold width direction between adjacent cooling water channels formed on the back surface of the mold plate.
e; Width (mm) of dissimilar substance filling part in the slab drawing direction
L; Spacing distance (mm) in the slab drawing direction between adjacent parts of the filling part of different substances
Vc; slab drawing speed (m / min) in the continuous steel casting process
f; Vibration frequency (1 / min) of the mold for continuous casting in the continuous casting process of steel
F; Distance between adjacent protrusions arranged in the cooling water channel in the slab drawing direction (mm)
[6] The mold for continuous casting of steel according to the above [4] or the above [5], wherein the dissimilar substance filling portion is formed so as to satisfy the condition of the following formula (4).
0.5 ≦ t ≦ d ……… (4)
Here, in the equation (4), each symbol represents the following.
t; Filling depth of dissimilar substances in dissimilar substance filling part (mm)
d; Width (mm) of dissimilar substance filling portion in the mold width direction
[7] The mold for continuous casting of steel according to any one of the above [1] to [6], wherein a plating layer is formed on the surface of the mold plate so as to cover the dissimilar substance filling portion.
[8] The method for continuous steel casting using the steel continuous casting mold according to any one of the above [1] to [7], wherein the water flow is formed at a position in the cooling water channel where a water flow disturbing portion is formed. A method for continuous casting of steel, in which cooling water is supplied to the continuous casting mold so that the flow becomes turbulent.

The mold for continuous casting of steel according to the present invention is provided with a water flow disturbing portion that disturbs the water flow and increases the surface area of the cooling water channel in the cooling water channel in the range corresponding to the region where the dissimilar substance filling portion is formed. .. As a result, in the cooling water channel in that range, the heat transfer coefficient between the water flow and the cooling water channel increases, the amount of convection heat transfer increases, and the heat of the mold plate in the region where the dissimilar substance filling portion is formed can be effectively removed. It is supposed to be. By effectively cooling the dissimilar substance filling portion and the mold plate, the thermal stress generated at the boundary portion between the mold plate and the dissimilar substance filling portion can be effectively suppressed. As a result, it is possible to prevent cracking on the surface of the slab of the steel grade accompanied by the peritectic reaction and to extend the number of times the mold with the different substance filling portion is formed, that is, to extend the life.

FIG. 1 is a perspective view of a mold for continuous casting of steel. FIG. 2 is a diagram showing an example of the surface of a mold plate constituting the long side of the mold according to the embodiment of the present invention. FIG. 3 is a diagram showing the structure of the long side of the mold of the portion surrounded by the quadrangle (□) in FIG. FIG. 4 is a diagram showing the back surface of a mold plate according to another embodiment of the present invention. FIG. 5 is a vertical cross-sectional view of the long side of the mold according to another embodiment of the present invention.

Hereinafter, the present invention will be specifically described with reference to the accompanying drawings.

Before explaining the present invention, a method for continuous casting of steel will be briefly described. A perspective view of the mold for continuous casting is shown in FIG. The continuous casting mold 1 for continuous casting of slab slabs (hereinafter, also simply referred to as "mold 1") is a pair of mold long sides 2 facing each other and a pair of molds sandwiched between the mold long sides 2 and facing each other. It has a short side 3. A tundish (not shown) for accommodating the molten steel 4 is arranged above the mold 1, and a dipping nozzle 5 is installed at the bottom of the tundish. A rectangular internal space is formed in the mold 1 by a pair of mold long sides 2 and a pair of mold short sides 3, and a dipping nozzle 5 is inserted in this internal space. As will be described later, the side of the mold long side 2 and the mold short side 3 in contact with the molten steel 4 is composed of a copper alloy mold plate, and a backup plate is arranged on the back surface of the mold plate.

The copper alloy mold plate constituting the mold long side 2 and the mold short side 3 has a cooling water channel formed on the back surface of the surface in contact with the molten steel 4, and the cooling water is passed through the cooling water channel to pass the cooling water to the mold. 1 is being cooled. In the continuous steel casting operation, the molten steel 4 is injected into the internal space of the mold 1 via the dipping nozzle 5, the molten steel 4 is cooled by the mold 1 and solidified, and a solidified shell is formed on the contact surface with the mold 1. .. A slab in which the solidified shell is used as an outer shell and the inside is made of unsolidified molten steel 4 is continuously drawn from the mold 1 in the slab drawing direction A which is downward in the vertical direction to manufacture a slab slab of steel. In the mold 1, the surface temperature of the mold plate (the temperature on the side in contact with the molten steel) rises due to contact with the molten steel 4 and the high-temperature slab, and the position of the meniscus M (the molten steel surface in the mold) in the mold. Shows the highest value in the vicinity. In FIG. 1, the position of the meniscus M is indicated by a chain double-dashed line.

Although it depends on the steel type, it is particularly desirable to uniformly remove heat from the solidified shell in the slab drawing direction A and the mold width direction B at the position of the meniscus M on the inner wall surface of the mold. This is because the uniform growth of the solidified shell thickness can be promoted. Here, the slab drawing direction A and the mold width direction B are orthogonal to each other. Further, as the mold plate, a copper alloy having high deformation resistance to thermal stress and having high thermal conductivity capable of enhancing the cooling effect by cooling water is used.

A plurality of slab support rolls (not shown) are arranged below the mold 1, and a water spray nozzle or an air mist spray nozzle is arranged between the adjacent slab support rolls. Cooling water is sprayed onto the surface of the slab through a water spray nozzle or an air mist spray nozzle to cool the slab, and the slab is pulled out while being supported by the slab support roll, and after solidification is completed to the center of the slab. , Cut the slab to a predetermined length.

As described above, steel slabs having a predetermined length to be hot-rolled in the next step are manufactured.

In the present invention, the heat transfer coefficient between the cooling water channel and the cooling water is increased by providing a member for disturbing the water flow and increasing the surface area of the cooling water channel in the cooling water channel for cooling the mold plate provided with the dissimilar substance filling portion. Increase and effectively remove heat from the mold plate. As a result, the temperature of the dissimilar substance filling portion and the surrounding mold plate is lowered, the thermal stress generated at the boundary portion between the mold plate and the dissimilar substance filling portion is suppressed, and the life of the continuous casting mold is extended.

An example of the embodiment of the continuous casting mold according to the present invention will be described. The long side 2 and the short side 3 of the mold constituting the mold 1 for continuous casting each have a mold plate on which the front surface forms an inner wall surface of the mold and a cooling water channel is formed on the back surface, and bolts and nuts on the mold plate. Has a backup plate and is attached by.

FIG. 2 shows an example of the surface of the mold plate constituting the mold long side 2. On the surface of the mold plate 21, a dissimilar substance filling portion 22 filled with a dissimilar substance having a thermal conductivity different from that of the mold plate 21 is formed in a recess (dent portion) formed in a region containing the meniscus M. .. The dissimilar substance filling portion 22 is formed in the slab drawing direction A and the mold width direction B in the vicinity of the meniscus containing at least the meniscus M. It is possible to process a dissimilar substance into a shape that fits into the recess and fit it into the recess to fill the dissimilar substance, but it is also possible to fill the recess with the dissimilar substance by plating means, thermal spraying means, or the like. .. When the recess is filled with a dissimilar substance by a plating means, a thermal spraying means, or the like, it is possible to prevent the formation of a void between the recess and the dissimilar substance.

A plurality of circular recesses are formed on the surface of the mold plate 21, and the circular recesses are filled with different substances to form a plurality of different substance charging portions 22 independent of each other. In that case, it is preferable to regularly arrange each of the dissimilar substance charging portions 22 so that the heat flux on the inner wall surface of the mold from the inner wall surface of the mold to the cooling water channel changes periodically.

By arranging a plurality of different substance filling portions 22 in the region including the vicinity of the meniscus M, the thermal resistance of the mold plate 21 in the slab drawing direction A and the mold width direction B in the region including the vicinity of the meniscus M is regular and It is increased or decreased periodically. As a result, the heat flux from the solidified shell to the mold plate 21 in the vicinity of the meniscus M, that is, at the initial stage of solidification, increases and decreases regularly and periodically. The regular and periodic increase and decrease of the heat flux reduces the stress and thermal stress generated by the transformation from δ iron to γ iron, and the deformation of the solidified shell caused by these stresses is reduced. By reducing the deformation of the solidified shell, the non-uniform heat flux distribution caused by the deformation of the solidified shell is made uniform, and the generated stress is dispersed to reduce the individual strain amount. As a result, the occurrence of surface cracks on the surface of the solidified shell is prevented.

The concave portion may have a pseudo-circular shape (referred to as a “pseudo-circular concave portion”) instead of a perfect circular shape (referred to as a “circular concave portion”) on the surface of the mold plate 21. The pseudo-circle is a shape having no corners, such as an ellipse, a square or a rectangle whose corners are circles or ellipses. Further, it may have a shape like a petal pattern.

In order to ensure that the change in heat flux on the inner wall surface of the mold is periodic, it is preferable that the intervals between the adjacent dissimilar substance filling portions 22 are the same. Further, the thermal conductivity of the dissimilar substance is preferably 80% or less or 125% or more with respect to the thermal conductivity of the mold plate constituting the mold long side 2 and the mold short side 3. The thermal conductivity of different substances changes as the atmospheric temperature changes. Therefore, the thermal conductivity of different substances and the mold plate is based on the room temperature (normal temperature) at the time of manufacturing the mold. If there is a difference of about 20% in the thermal conductivity of dissimilar substances with respect to the thermal conductivity of the mold plate at room temperature, the heat flux on the inner wall surface of the mold will increase and decrease regularly and periodically, and the heat flux will increase from δ iron to γ. It is possible to reduce the stress and thermal stress generated by the transformation to iron. However, the thermal conductivity of different substances does not necessarily have to be in the above range, as long as it is possible to reduce the stress generated by the above-mentioned transformation and prevent surface cracking of the slab. The spacing between the filling portions 22 does not necessarily have to be the same.

Examples of dissimilar substances having a thermal conductivity of 80% or less with respect to the thermal conductivity of the mold plate include plating, Ni (thermal conductivity; about 90 W / (m × K)) and Ni alloy (heat conductivity; Thermal conductivity; about 40-90 W / (m × K)) can be used. A copper alloy (thermal conductivity; about 100 to 385 W / (m × K)) is used for the mold plate, for example, a high thermal conductivity type copper alloy (thermal conductivity; about 318 W / (m × K)) or electromagnetic waves. A low thermal conductivity type copper alloy for stirring (thermal conductivity; about 119 to 239 W / (m × K)) can be used. However, metals other than Ni alloys and copper alloys can be used for dissimilar substances and mold plates.

As the mold plate, pure copper (thermal conductivity; about 398 W / (m × K)) or the above-mentioned copper alloy may be used. In particular, when the molten steel in the mold is electromagnetically agitated, in order not to attenuate the magnetic field strength from the coil into the molten steel, a copper alloy having a low conductivity due to the addition of several mass% of components other than the copper component is used. It is preferable to use it. The thermal conductivity of copper alloy is lower than that of pure copper. That is, it is desirable to appropriately select a different substance and / or a material of the mold plate according to the use of the mold 1 to adjust the thermal conductivity of the different substance and the mold plate.

Similar to the mold long side 2, a dissimilar substance filling portion may be formed on the surface of the mold short side 3 for which illustration and description are omitted. However, in the slab slab, stress concentration is likely to occur in the solidified shell on the long side surface side due to its shape, and surface cracking is likely to occur on the long side surface side. Therefore, it is necessary to install a dissimilar substance filling portion on the long side of the mold for continuous casting for slab slabs, but it is not always necessary to install a dissimilar substance filling portion on the short side of the mold.

Considering the effect on initial solidification, dissimilar substances are found in the region of the inner wall surface of the mold from the upper position Q away from the position of the meniscus M during steady casting to the lower position R away from the meniscus. It is preferable to provide the filling portion 22. The distance Q is any value greater than zero. The distance R can be calculated from the following equation (5).

R (mm) = 2 x Vc x 1000/60 ……… (5)
Here, Vc is a slab drawing speed (m / min) in the continuous steel casting process.

The distance R is related to the time for the solidified shell (slab) after the start of solidification to pass through the region where the dissimilar substance filling portion 22 is formed. It is preferable that the solidified shell (slab) stays in the region where the dissimilar substance filling portion 22 is installed for at least 2 seconds after the start of solidification. In order for the solidified shell (slab) to exist in the region where the dissimilar substance filling portion 22 is installed for at least 2 seconds after the start of solidification, the dissimilar substance is filled to a distance R or more lower than the meniscus M by the formula (5). It is necessary to install the unit 22.

If the time for the slab to stay in the region where the dissimilar substance filling section 22 is installed after the start of solidification is secured for 2 seconds or more, the cycle of heat flux from the inner wall surface of the mold to the cooling water channel by the dissimilar substance filling section 22. The effect of the change can be fully obtained. That is, by setting the staying time in the region of the dissimilar substance filling portion 22 of the solidified shell to 2 seconds or more, the surface cracking of the slab can be prevented even during high-speed casting where surface cracking is likely to occur or during casting of medium carbon steel. The effect is obtained. However, in order to stably obtain the effect of the periodic change of the heat flux by the dissimilar substance filling section 22, the time required for the solidified shell to pass through the region where the dissimilar substance filling section 22 is installed should be 4 seconds or more. Is more preferable. On the other hand, in the case of the thin slab continuous casting machine, since the slab drawing speed is high, the distance R is large, the range of the slab drawing direction A in which the dissimilar substance filling portion 22 should be installed becomes large, and the processing cost of the mold increases. In some cases. Even in such a case, if the time for passing through the dissimilar substance filling portion 22 is secured for 1 second or more, the effect of periodically changing the heat flux corresponding to the time can be obtained.

The upper end of the region where the dissimilar substance filling portion 22 is formed is not particularly limited as long as it is above the meniscus M. Therefore, the distance Q is an arbitrary value exceeding zero. However, since the meniscus M fluctuates in the vertical direction during casting, the meniscus M is filled up to a position about 10 mm above the meniscus M so that the upper end of the region of the dissimilar substance filling portion 22 is always above the meniscus M. It is preferable to form the portion 22. It is preferably up to about 20 mm above. The position of the meniscus M is generally 60 to 150 mm below the upper end of the long side 2 of the mold, and the region for forming the dissimilar substance filling portion 22 may be determined accordingly.

In the continuous steel casting process, the temperature of the mold plate rises because the hot molten steel is injected into the internal space of the mold. Therefore, a cooling water channel is formed in the mold plate constituting the long side and the short side of the mold, and the cooling water is passed through the cooling water channel to cool the mold plate, thereby maintaining the shape of the mold. is doing. However, the thermal expansion rate of the dissimilar substance filling portion 22 is different from the thermal expansion rate of the mold plate 21, and therefore, the surface of the mold plate (the inner wall surface of the mold) is cracked due to the thermal stress concentrated on these boundaries. It can occur.

Therefore, in the present invention, a water flow disturbing portion that disturbs the water flow and increases the surface surface of the cooling water channel is formed in the range of the cooling water channel that correspondingly cools the region where the dissimilar substance filling portion 22 of the mold plate 21 is formed. Then, the heat transfer coefficient between the cooling water channel and the water flow at the site is increased. This promotes heat removal from the mold plate in the region where the dissimilar substance filling portion 22 is formed.

The water flow disturbance part will be described. FIG. 3 shows the structure of the long side of the mold of the portion surrounded by the quadrangle (□) shown in FIG. In FIG. 3, (a) is a plan view showing the front surface of the mold plate, and (b) is a plan view showing the back surface of the mold plate. (C) is a vertical cross-sectional view of the long side of the mold of the portion, and (d) is a horizontal cross-sectional view of the long side of the mold of the said portion. As shown in FIGS. 3 (c) and 3 (d), a backup plate 23 is attached to the back surface of the mold plate 21 so as to cover the cooling water channel 31 formed in the mold plate 21.

As shown in FIG. 3B, a cooling water channel 31 is formed on the back surface of the mold plate 21. The cooling water channel 31 is composed of a plurality of vertically elongated grooves extending along the slab drawing direction A, and the plurality of grooves are aligned in the mold width direction B. Due to the vertically long shape, the linear flow velocity in the cooling water channel 31 can be easily increased even if the flow rate of water supplied to the cooling water channel 31 is reduced, the temperature of the water flow can be easily kept low, and the mold plate 21 can be efficiently cooled. ..

In the continuous casting mold 1 according to the present invention, a water flow disturbing portion that disturbs the water flow is formed in the cooling water channel 31 on the back surface of the mold plate 21 corresponding to the region where the dissimilar material filling portion 22 is formed. As shown in FIGS. 3 (b) to 3 (d), the water flow disturbing portion can be composed of, for example, protrusions 32 that are installed so as to extend in the mold width direction B of the cooling water channel 31 and the thickness direction of the cooling water channel 31. .. That is, the protrusion 32 reduces the flow path area of the cooling water channel 31 and becomes an obstacle to the water flow flowing through the cooling water channel 31 in the mold width direction B of the cooling water channel 31 and the thickness direction of the cooling water channel 31. It is spread out and installed.

In order to further disturb the water flow in the cooling water channel and further increase the surface area of the cooling water channel 31, this protrusion 32 is provided in the cooling water channel 31 along the flow direction of the water flow (the direction opposite to the slab drawing direction A). It is preferable to arrange more than one. The protrusion 32 can be installed by fitting it into a groove (not shown) provided in the cooling water channel 31, joining it to the mold plate 21 by welding, joining it to the mold plate 21 with an adhesive, or the like.

The water flow flowing through the cooling water channel 31 collides with the protrusion 32 and is disturbed, the degree of turbulence increases in the water flow in the region where the protrusion 32 is provided, and the thickness of the boundary layer of the water flow (turbulent flow) in contact with the cooling water channel 31 increases. Become thin. As a result, the heat transfer coefficient from the cooling water channel 31 to the water flow becomes large, and the mold plate 21 in the region where the dissimilar substance filling portion 22 is formed can be effectively cooled. Further, since the surface area where the cooling water comes into contact with the mold plate 21 is increased by the protrusion 32, it is possible to more effectively cool the mold plate 21 in the region where the dissimilar substance filling portion 22 is formed.

Here, it is preferable that the protrusion 32 has a length of 1/3 or more of the width (length in the mold width direction) of the cooling water channel 31 and not more than the entire width direction of the mold in the mold width direction B. Further, in the thickness direction of the cooling water channel 31, it is preferable that the height (length) is 1 mm or more from the back surface of the mold plate 21 (bottom surface of the cooling water channel 31) and ½ or less of the thickness w of the cooling water channel 31. .. In FIG. 3, the protrusion 32 is formed at a position on the back surface of the mold plate 21 corresponding to the region where the dissimilar substance filling portion 22 is formed, but the cooling water channel 31 from the upper end to the lower end of the mold plate 21 is formed. The protrusion 32 may be provided on the surface. Further, FIG. 3 shows an example in which the protrusion 32 is formed so as to cover the entire cooling water channel 31 in the mold width direction.

The degree of turbulence of the water flow flowing through the cooling water channel 31 or whether the water flow is a laminar flow can be determined by using a known Reynolds number Re as an index. Generally, the density of water flow (kg / m ³ ), the linear velocity of water flow (m / s), the characteristic length (m) such as the distance through which water flows, and the viscosity coefficient of water flow (Pa × s). From, the Reynolds number Re can be calculated. In the continuous casting mold according to the present invention, the Reynolds number Re is calculated by adopting the thickness w (see FIG. 3C) of the cooling water channel 31 when there is no protrusion 32 as the “characteristic length (m)”. do it. If the cooling water is supplied to the cooling water channel 31 under the condition that the Reynolds number Re calculated assuming that there is no protrusion 32 exceeds 2300, the thickness of the cooling water channel 31 is reduced by the protrusion 32 in the region where the protrusion 32 is formed. Therefore, the water flow that collides with the protrusion 32 can be regarded as a turbulent flow.

In the mold for continuous casting according to the present invention, the dissimilar substance filling portion 22 and the cooling water channel 31 are formed on the mold plate 21 so as to satisfy at least one of the following equations (1) to (3). It is preferable that it is.

d <P ≦ S ……… (1)
e ≦ L ≦ 1000 × Vc / f ……… (2)
F ≤ L ……… (3)
Here, in the equations (1) to (3), each symbol represents the following.

d; Width of dissimilar substance filling portion in the mold width direction (mm)
P; Spacing distance (mm) in the mold width direction between adjacent parts filled with different substances
S; Spacing distance (mm) in the mold width direction between adjacent cooling water channels formed on the back surface of the mold plate.
e; Width (mm) of dissimilar substance filling part in the slab drawing direction
L; Spacing distance (mm) in the slab drawing direction between adjacent parts of the filling part of different substances
Vc; slab drawing speed (m / min) in the continuous steel casting process
f; Vibration frequency (1 / min) of the mold for continuous casting in the continuous casting process of steel
F; Distance between adjacent protrusions arranged in the cooling water channel in the slab drawing direction (mm)
The "interval distance" refers to the distance between the centers in the slab drawing direction A or the mold width direction B of two adjacent parts of each part (see FIG. 3).

Further, in the continuous casting mold according to the present invention, it is preferable that the dissimilar substance filling portion 22 is formed on the mold plate 21 so as to satisfy the condition of the following formula (4).

0.5 ≦ t ≦ d ……… (4)
Here, in the equation (4), t; the filling depth (mm) of the different substance in the different substance filling portion, and d; the width (mm) of the different substance filling portion in the mold width direction.

In the mold for continuous casting, since the cooling water channel 31 is formed on the back surface of the mold plate 21, the portion of the mold plate 21 near the cooling channel 31 is cooled more than the portion far away, and the surface of the mold plate 21 is cooled. The degree of cooling tends to be uneven. It is preferable to satisfy the equation (1) in order to suppress the influence of the cooling by the cooling water channel 31 on the periodic increase / decrease in thermal resistance by the dissimilar substance filling portion 22. That is, it is preferable that the spacing distance P in the mold width direction B of the dissimilar substance filling portion 22 is equal to or greater than the width d of the dissimilar substance filling portion 22 and equal to or less than the spacing distance S of the cooling water channel 31 (see FIG. 3D). ).

Further, since the mold plate 21 is cooled by the cooling water flowing through the cooling water channel 31 on the back surface of the mold plate 21, the mold plate 21 is radially discharged from the cooling water channel 31. Therefore, on the surface of the mold plate 21, cooling unevenness occurs between the portion near the cooling water channel 31 and the portion far from the cooling water channel 31. In order to further exert the effect of reducing the stress and thermal stress generated by the transformation from δ iron to γ iron by the periodic increase / decrease of the thermal resistance by the dissimilar substance filling portion 22, the interval distance S of the cooling water channel 31 is used. It is preferable to generate a heat flux difference at small intervals. Therefore, it is preferable to have the equation (1), that is, it is preferable that the spacing distance P in the mold width direction B of the dissimilar substance filling portion 22 is equal to or less than the spacing distance S of the cooling water channel 31, and the width d of the dissimilar substance filling portion 22 is. It is preferably less than the interval distance P.

The width d of the dissimilar substance filling portion 22 is preferably 2 to 20 mm. When the dissimilar substance filling portion 22 is a pseudo-circular shape, a circle-equivalent diameter obtained from the following equation (6) may be adopted as the width d.

Circle equivalent diameter = (4 x S / π) ^1/2 ……… (6)
Here, in the equation (6), S is the area (mm ² ) of the dissimilar substance filling portion 22.

By setting the width d or the equivalent diameter of the circle to 2 mm or more, it becomes easy to fill the circular or pseudo-circular recesses by the plating means or the thermal spraying means. On the other hand, by setting the width d and the equivalent circle diameter to 20 mm or less, the decrease in the heat flux in the dissimilar substance filling portion 22 is suppressed, that is, the solidification delay in the dissimilar substance filling section 22 is suppressed, and the solidification delay at that position is suppressed. Stress concentration on the solidified shell is prevented, and it becomes easy to prevent the occurrence of surface cracks in the solidified shell.

Further, in the continuous steel casting method, when injecting molten steel into a mold, it is common to vibrate the mold while pouring mold powder onto the molten steel surface in order to prevent seizure of the molten steel on the mold. be. It is known that oscillation marks are periodically formed on the surface of the slab due to this vibration in the slab withdrawal direction A, and the thickness of the slab is periodically increased in the slab withdrawal direction A. Tends to change.

The width e (mm) of the dissimilar substance filling portion 22, the spacing distance L (mm) between the adjacent dissimilar substance filling portions 22, the slab drawing speed Vc (m / min), and the vibration frequency f (1 / min) of the mold. ) And satisfy the equation (2), so that lateral cracking of the slab can be suppressed. That is, if the width e of the dissimilar substance filling portion 22 in the slab drawing direction A becomes smaller than the length (pitch) of one cycle in the slab pulling direction A of the thickness of the slab that increases or decreases due to the oscillation mark. , Lateral cracking of the slab can be suppressed.

When the spacing distance F between the adjacent protrusions 32 and the spacing distance L in the slab drawing direction A of the adjacent dissimilar substance filling section 22 satisfy the equation (3), the dissimilar substance filling section adjacent to the slab drawing direction A is satisfied. It means that the protrusion 32 is formed at the position corresponding to the portion between 22. As a result, the surface area of the cooling water channel in that portion increases by the surface area of the protrusion, and the water flow tends to be turbulent in the cooling water channel. As a result, the heat of the mold plate 21 is removed more effectively.

In addition, in order to satisfy the equation (4), it is preferable that the filling thickness t of the different substances is 0.5 mm or more and dmm or less. If the filling thickness t (see FIG. 3D) of the dissimilar substance filling portion 22 is less than 0.5 mm, the fluctuation amount of the heat flux in the dissimilar substance filling portion 22 may be insufficient. On the other hand, if the filling thickness t is too large, it becomes difficult to fill the recesses with different substances. Therefore, it is preferable that the filling thickness t is equal to or less than the width d (mm) of the dissimilar substance filling portion in the mold width direction. Further, the filling thickness t is preferably 10 mm at the maximum. This is because if the filling thickness t exceeds 10 mm, it becomes difficult to fill different substances.

As shown in FIG. 4, a plurality of protrusions 42 may be arranged in a staggered arrangement in the cooling water channel 31. As a result, as in the case of FIG. 3, the water flow of the cooling water channel 31 provided with the protrusion 42 tends to be turbulent. If the protrusion 42 is formed into an ellipsoid formed by cutting a rugby ball in half, for example, the water flow has a stronger degree of turbulence, the heat transfer coefficient between the mold plate 21 and the water flow becomes higher, and the dissimilar substance filling portion. It is possible to effectively cool the region of the mold plate 21 on which the 22 is formed. Here, the "staggered arrangement" means that the group of protrusions 42 arranged side by side in the mold width direction B are arranged side by side in the upper and / or lower mold width direction B adjacent to the slab drawing direction A. It is arranged at a position half of the widthwise pitch of the group of protrusions 42 with respect to the group of protrusions 42. In the present specification, the case where one protrusion 42 is arranged side by side in the mold width direction B is also referred to as a “group”.

In FIG. 3, the protrusion 32 is provided on the mold plate 21 side of the cooling water channel 31, that is, on the bottom surface side of the cooling water channel 31, but the protrusion 32 may be provided on the backup plate 23 side of the cooling water channel 31. In that case, although the surface area of the mold plate 21 facing the cooling water becomes smaller, the water flow tends to be turbulent in the cooling water channel, and the heat of the mold plate 21 can be removed more effectively. It is possible and the effect of the present invention is fully exhibited.

As shown in FIG. 5, the plating layer 51 may be formed on the surface of the mold plate 21 so as to cover the dissimilar substance filling portion 22. As a result, it is possible to suppress wear due to the solidified shell and cracking of the mold surface due to heat history. The plating layer 51 is formed by plating or spraying a commonly used nickel or nickel-containing alloy, for example, a nickel-cobalt alloy (Ni—Co alloy) or a nickel-chromium alloy (Ni—Cr alloy). Can be formed with.

Using the continuous casting mold described above, the steel that casts the slab by supplying cooling water to the continuous casting mold so that the water flow becomes turbulent at the position where the water flow disturbing part is formed in the cooling water channel. In particular, when the molten steel is medium carbon steel, continuous casting can be carried out for a long period of time by effectively preventing cracks on the surface of the slab and using the same mold.

Although the mold for continuous casting has a dissimilar substance filling portion formed on the inner wall surface of the mold as shown in FIG. 2, the protrusions 32 shown in FIGS. 3 (b) to 3 (d) are not formed in the cooling water channel. A mold for continuous casting was prepared, and continuous casting of steel was performed using this mold (comparative example). The prepared mold for continuous casting is a mold having a rectangular inner surface space having a mold long side length of 2.1 m and a mold short side length of 0.22 m, and is a mold plate constituting the mold long side and the mold short side. Was made of a copper alloy having a thermal conductivity of about 380 (W / (m × K)) at room temperature.

As the target steel type for continuous casting, the chemical composition is C; 0.08 to 0.17% by mass, Si; 0.10 to 0.30% by mass, Mn; 0.50 to 1.20% by mass, P; 0.010 to 0.030% by mass, S; 0.005 to 0.015% by mass, Al; 0.020 to 0.040% by mass, the balance Fe and medium carbon steel which is an unavoidable impurity. The mass of molten steel per charge is 300 tons. In the comparative example, while injecting molten steel of medium carbon steel into the prepared mold, the mold is cooled while vibrating the mold in the direction of drawing out the slab to form a solidified shell, and the solidified shell is pulled out to form a slab slab. Cast. The slab drawing speed Vc was 2.0 (m / min).

In the continuous casting operation, mold powder was poured onto the molten steel in the vibrating mold to prevent seizure of the molten steel in the mold. As the mold powder, a mold powder having a basicity ((mass% CaO) / (mass% SiO ₂ )) of 1.1 and a melting temperature of 1210 ° C. and a viscosity of 0.15 Pa × s at 1300 ° C. was used.

In the continuous casting operation, the goal was to perform continuous casting of 3000 charges without changing the mold, and the surface cracks on the long side of the mold were investigated after every 100 charges of casting. It was decided to visually inspect whether there were cracks on the surface of the long side of the mold, and if cracks were confirmed, stop the continuous casting operation at that point. The surface cracks of the slab were investigated for each continuous casting. For surface cracks in the slab, the surface of the slab subjected to the penetrant inspection (color check) was visually inspected, and vertical cracks along the slab drawing direction and horizontal cracks along the slab width direction were confirmed.

In the mold of the comparative example, a plurality of circular recesses are formed in the mold plate constituting the long side of the mold, and a nickel alloy (thermal conductivity at room temperature; 80 (W / (m ×)) is used as a dissimilar substance by using plating means inside the concave portions. K))) was filled to form a heterogeneous substance filling part. Further, a plating layer 51 as shown in FIG. 5 was provided on the inner wall surface of the mold. The same nickel alloy as the dissimilar substance was used as the material.

Further, as shown in FIG. 2, a mold for continuous casting in which the dissimilar substance filling portion 22 is formed on the surface of the mold plate 21 and the protrusions 32 as shown in FIG. 3 are formed in the cooling water channel is prepared, and the mold is used. A continuous casting operation of steel was carried out (Example 1 of the present invention). In Example 1 of the present invention, the filling depth t of a different substance is set to 1 mm, and the different substance filling portion 22 and the protrusion 32 are installed so as to satisfy the equations (1), (2) and (3).

In the mold of Example 1 of the present invention, the plating layer 51 was provided as in the comparative example, and a nickel alloy was used as the material thereof as in the comparative example. In Example 1 of the present invention, the continuous casting operation of steel was carried out under the same conditions as in the comparative example except for the mold for continuous casting used. For example, the speed at which the cooling water is supplied to the mold in the comparative example is the speed at which the Reynolds number Re of the water flow in the cooling water channel becomes turbulent in the mold in which the protrusions are not formed. The cooling water was supplied to the mold so as to be the same as the supply speed of the cooling water in.

Further, in Example 1 of the present invention, it is aimed to perform continuous casting of 3000 charges without exchanging the mold, and as in the comparative example, surface cracks on the long side of the mold are investigated after each 100 charge of casting is completed. If cracks were found on the surface of the long side of the mold, continuous casting was stopped at that point. In addition, surface cracks in the slab were investigated for each continuous casting.

In the comparative example, surface cracks were found in the mold plate constituting the long side of the mold at the end of casting of 2400 charges. On the other hand, in Example 1 of the present invention, surface cracking did not occur in the mold plate constituting the long side of the mold even at the end of casting of 3000 charges. That is, in Example 1 of the present invention, continuous casting could be performed a target number of times without causing surface cracks in the mold plate constituting the long side of the mold.

In the comparative example, regarding the life of the mold, it was found that the mold plate constituting the long side of the mold had surface cracks in the investigation after the completion of continuous casting of 2400 charges. On the other hand, in Example 1 of the present invention, continuous casting of 3000 charges of the target number of times could be performed without replacing the mold, and the service life of the mold could be improved as compared with the comparative example. This is because the protrusion 32 (water flow disturbing part) made the water flow more turbulent than in the comparative example, and also increased the surface area of the cooling water channel to cool the mold more efficiently. it is conceivable that.

It was investigated whether the slabs of Comparative Example and Example 1 of the present invention had surface cracks, but no surface cracks were confirmed in either of them. In any mold, the dissimilar material filling section can effectively prevent surface cracking caused by the non-uniform solidification shell thickness caused by the transformation from δ iron to γ iron that occurs in medium carbon steel casting. It is expected that the surface cracking of the slab could be prevented.

The continuous casting operation of steel was carried out in the same manner as in Example 1 described above (Examples 2 to 21 of the present invention). In Example 2, the number of casting charges in one example of the present invention was set to 5 charges. Further, in each of Examples 2 to 21 of the present invention, the width d (mm) of the dissimilar substance filling portion 22 in the mold width direction and the spacing distance P (mm) of the dissimilar substance filling portion 22 in the mold width direction shown in FIG. ), The width e (mm) of the dissimilar substance filling portion 22 in the slab drawing direction A, and the like, and further, the vibration frequency (1 / min) and the slab drawing speed Vc (m / min) were changed.

In each operation, a continuous casting operation of 5 charges is performed once, and in the mold used, each of the plurality of dissimilar substance filling portions 22 in the vicinity of the meniscus M and each of the intermediate points of the adjacent dissimilar substance filling portions 22. Thermocouples were embedded in the thermocouples and their temperatures were measured with the thermocouples. The temperature was measured at 1 second intervals and the temperature data was recorded. The distance from the temperature measuring point of the thermocouple to the surface of the mold plate 21 on the molten steel side is 15 mm. Based on the heat transfer model, the surface temperature of the mold plate 21 was calculated from the measured temperature data.

In the examples of the present invention excluding the example 19 of the present invention, as shown in FIG. 3, the protrusion 32 is provided on the mold plate 21 side of the cooling water channel 31. On the other hand, in Example 19 of the present invention, the protrusion 32 is provided on the backup plate 23 side of the cooling water channel 31.

Table 1 shows the width d, the interval distance P (mm), and the calculated temperature in Examples 2 to 21 of the present invention.

In Table 1, the items of the formulas (1) to (3) are provided. When each item of the formulas (1) to (3) is "○", it means that the condition of the formula of each item is satisfied, and when it is "x", it means that the condition is not satisfied.

Further, in Table 1, the average temperature of the surface temperature of the mold plate 21 obtained based on the heat transfer model is calculated from the temperature data measured at the plurality of different substance filling portions 22 and the plurality of intermediate points, and then the average temperature is calculated. The value calculated by further averaging the average temperature with the number of data samples within the steady operation time of 5-charge continuous casting is described as "meniscus position temperature". Further, Table 1 shows the surface temperature of the mold plate 21 similarly calculated from the temperature data measured at the plurality of dissimilar substance filling portions 22 and the plurality of intermediate points within the steady operation time of the continuous casting of 5 charges. , The maximum value among the absolute values of the difference from the "meniscus position temperature" is described as the "maximum temperature amplitude".

The lower the "meniscus position temperature" in Table 1, the cooler the surface of the mold plate at the meniscus M position, and the smaller the "maximum temperature amplitude", the lower the meniscus M position. It means that the cooling unevenness is suppressed in the mold width direction.

Also in Example 2, surface cracks in the slab were investigated for each continuous casting operation. Since 10 slab slabs can be produced in a 1-charge continuous casting operation and 5 charges are continuously cast in one example of the present invention, 50 slab slabs can be produced in one example of the present invention. Will be done. All of these slabs were subjected to a penetrant inspection, and the surface of the slabs subjected to the penetrant inspection was visually inspected to investigate cracks on the surface of the slabs. If horizontal cracks and / or vertical cracks are found on the surface of the slab, count the slabs and divide the total number of slabs (= 50) by the percentage of the total number of slabs found with cracks. Table 1 shows the "vertical crack occurrence rate" (%) and "horizontal crack occurrence rate" (%) for each crack. Even if the crack occurrence rate is not zero (= 0), even if very fine cracks are visually found, the slabs are counted, so if the crack occurrence rate is 15% or less, it is practically. no problem.

When the meniscus position temperature is 300 ° C. or lower and the maximum temperature amplitude is 40 ° C. or lower, it can be said that cooling is generally stable. Further, if the dissimilar substance filling portion is formed on the mold surface, it is possible to prevent the surface cracking of the slab in most cases.

In Examples 2 to 12 of the present invention satisfying the formulas (1) to (3), surface cracking could be prevented in all the slabs obtained in one continuous casting operation. Further, in the mold, the meniscus position temperature was 300 ° C. or lower and the maximum temperature amplitude was 40 ° C. or lower, so that it was confirmed that the mold could be cooled more effectively.

In Examples 13 to 16 of the present invention, the equation (3) is satisfied, and it can be seen that the cooling is generally effective, but the equations (1) and / or the equation (2) are not satisfied, so that 50 sheets are satisfied. Some of the slab slabs had vertical and / or horizontal cracks.

In Example 17 of the present invention, since the equations (1) and (2) were satisfied, there was no slab having surface cracks, but since the equation (3) was not satisfied, the meniscus position temperature exceeded 300 ° C. It can be seen that the cooling effect is inferior to that of Example 3 of the present invention. In Example 18 of the present invention, the maximum temperature amplitude is 22 ° C., and the cooling unevenness along the mold width direction is smaller than that of Example 3 of the present invention. However, the meniscus position temperature is higher than that of Example 3 of the present invention, and the cooling of the meniscus is inferior to that of Example 3 of the present invention. Further, in the example 18 of the present invention, since the filling depth t is less than 0.5, the amount of periodic fluctuation in thermal resistance becomes smaller than in the case of other examples of the present invention, and the equation (1) is satisfied. However, vertical cracks occurred.

In Example 19 of the present invention, steel is continuously cast under the same conditions as in Example 5 of the present invention except that the protrusion 32 is provided on the backup plate 23 side. In Example 19 of the present invention, the rate of occurrence of surface cracks in the slab was zero as in Example 5 of the present invention, but the meniscus position temperature was slightly higher than that of Example 5 of the present invention. It is presumed that this is because the protrusion 32 is provided on the backup plate 23 side, so that the surface area of the mold plate 21 facing the cooling water channel 31 is smaller than that in the case of Example 5 of the present invention.

Example 20 of the present invention satisfying the equation (3) has a maximum temperature amplitude smaller than that of Example 3 of the present invention. However, in Example 20 of the present invention, the meniscus position temperature is higher than that of Example 3 of the present invention. Higher meniscus position temperature means higher temperature at any position along the mold width direction, resulting in maximum temperature amplitude (difference between highest or lowest temperature and average temperature). Is presumed to be smaller. Since Example 21 of the present invention does not satisfy the equation (3), the meniscus position temperature exceeds 300 ° C. and the maximum temperature amplitude exceeds 40 ° C.

As can be seen from the above results, according to the present invention, the occurrence of surface cracks in the slab of medium carbon steel can be suppressed, and the temperature of the mold plate near the meniscus portion in which the dissimilar substance filling portion is formed can be effectively lowered. I was able to confirm that it was possible. According to the present invention, it is possible to achieve a long life of a mold in which a different substance filling portion is formed.

1 Mold for continuous casting 2 Mold long side 3 Mold short side 4 Molten steel 5 Immersion nozzle 21 Mold plate 22 Dissimilar substance filling part (circular)
23 Backup plate 31 Cooling water channel 32 Protrusion (water flow disturbing part)
42 Protrusions (water flow disturbance part)
51 Plating layer

Claims (7)

A copper alloy mold plate with a front surface forming the inner wall surface of the mold and a cooling water channel formed on the back surface.
A mold for continuous casting of steel comprising a backup plate attached to the mold plate so as to cover the cooling water channel.
In the recess formed on the surface of the mold plate at least in the region containing the meniscus, a heterogeneous substance filling portion filled with a heterogeneous substance having a thermal conductivity different from that of the mold plate is formed.
In the cooling water channel on the back surface of the mold plate corresponding to the region where the dissimilar substance filling portion is formed, a water flow disturbing portion that disturbs the water flow and increases the surface area of the cooling water channel is formed .
The dissimilar substance filling portion includes a plurality of circular recesses or pseudo-circular recesses, and is formed in a plurality.
The water flow disturbing portion is composed of a plurality of protrusions arranged along the flow direction of the water flow.
The dissimilar substance filling portion and the cooling water channel are formed so as to satisfy at least one of the following equations (1) to (3) below, which is a mold for continuous casting of steel.
d <P ≦ S ……… (1)
e ≦ L ≦ 1000 × Vc / f ……… (2)
F ≤ L ……… (3)
Here, in the equations (1) to (3), each symbol represents the following.
d; Width of dissimilar substance filling portion in the mold width direction (mm)
P; Spacing distance (mm) in the mold width direction between adjacent parts filled with different substances
S; Spacing distance (mm) in the mold width direction between adjacent cooling water channels formed on the back surface of the mold plate.
e; Width (mm) of dissimilar substance filling part in the slab drawing direction
L; Spacing distance (mm) in the slab drawing direction between adjacent parts of the filling part of different substances
Vc; slab drawing speed (m / min) in the continuous steel casting process
f; Vibration frequency (1 / min) of the mold for continuous casting in the continuous casting process of steel
F; Distance between adjacent protrusions arranged in the cooling water channel in the slab drawing direction (mm) The mold for continuous casting of steel according to claim 1 , wherein the water flow disturbing portion is composed of protrusions extending in the mold width direction of the cooling water channel and the thickness direction of the cooling water channel. The mold for continuous casting of steel according to claim 1, wherein the water flow disturbing portion is composed of a plurality of protrusions arranged in a staggered arrangement in the cooling water channel. In the region from the upper end to the lower end of the plurality of dissimilar substance filling portions on the surface of the mold plate, the plurality of said so that the heat flow on the inner wall surface of the mold from the inner wall surface of the mold to the cooling water channel changes periodically. The mold for continuous casting of steel according to any one of claims 1 to 3, wherein a dissimilar substance filling portion is formed. The mold for continuous casting of steel according to any one of claims 1 to 4, wherein the dissimilar substance filling portion is formed so as to satisfy the condition of the following formula (4).
0.5 ≦ t ≦ d ……… (4)
Here, in the equation (4), each symbol represents the following.
t; Filling depth of dissimilar substances in dissimilar substance filling part (mm)
d; Width of dissimilar substance filling portion in the mold width direction (mm) The mold for continuous casting of steel according to any one of claims 1 to 5 , wherein a plating layer is formed on the surface of the mold plate so as to cover the dissimilar substance filling portion. The method for continuous casting of steel using the steel continuous casting mold according to any one of claims 1 to 6 , wherein the water flow is turbulent at a position in the cooling water channel where a water flow disturbing portion is formed. A method for continuous casting of steel, in which cooling water is supplied to the continuous casting mold so as to be.

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