JPH01181947A - Mold for continuous casting - Google Patents

Abstract

PURPOSE:To enable good quality in a cast billet symmetrically forming solidified structure by fitting lining of material having heat resistance at a part of axial direction of inner circumferential wall in a mold and arranging gap part at suitable position of contacting part of the lining with the mold. CONSTITUTION:The mold 1 of copper alloy in the mold-set A forms a cylindrical shape having the diameter estimating shrinkage of the cast billet at the time of cooling to the inner circumferential part and having taper toward the casting direction. Thermocouple 4 is inserted to detect abnormality of breakage, etc., in the cast billet. A part of inner circumferential wall diameter of the mold 1 near the downstream is enlarged, and graphite liner 2 having shallow recessed position 2a is arranged at the outer circumferential wall and connected so as not to exist step difference with the mold 1. Molten metal M flowed from a tundish E to the mold-set A is cooled with the mold 1 to develop solidified shell Ca, and gap G is developed at contact part of the inner circumferential wall in a liner 2. When the molten metal M reaches to the part arranging the gap part 2a, by this heat insulating action, the difference in the cooling intensity is not developed and deformation and biased cooling are not progressed. By this method, the deformation and cracking are restrained at the min. and the cast billet having good quality can be obtd.

Description

Detailed Description of the Invention (Industrial Application Field) This invention relates to a mold that cools and solidifies supplied molten metal in order to continuously cast metal such as steel. The present invention relates to a continuous casting mold that can control the degree of cooling by limiting the amount of heat transfer at any location.

(Prior art) The mold used for continuous casting is formed into a cylindrical body.
This device solidifies the molten metal supplied to the hollow shaft into a slab by cooling its outer peripheral wall (generally water cooling). In the mold, the mold has a hollow shaft part that corresponds to the desired cross-sectional shape and dimensions of the slab, and a cooling water jacket is installed on the outside of the mold, so that cooling water flows along the outer peripheral wall of the mold. has been done.

Therefore, the molten metal loses its heat to the cooling water passing through the mold, is cooled and solidified, and becomes a slab. Continuous casting involves supplying molten metal, which has been stored in a tundish, to such a mold, where it is cooled and reduced to a small amount.
In both cases, a slab is formed whose outer periphery is solidified, and then continuously pulled out using a pulling device installed downstream of the mold. Note that the casting direction (the axial direction of the mold) in continuous casting is not limited to vertical (downward), but may be set horizontally or in an inclined direction, and the hollow axis of the mold is not necessarily straight (it may be curved). There is also.

Classified according to the form of the cylindrical body (mold), there are two types of repulsion: ``huggi''.

a) Mold that integrally forms a cylindrical body: In a mold for obtaining a small cross-section slab, the mold is an integral cylinder or a rectangular cylinder, and in a mold for a large cross-section rectangular slab (slab or bloom), the mold is A cylindrical body is often assembled by closely adhering a plurality of mold elements divided in different directions. The former is called a tubular mold, and the latter is called an assembly mold, but in both cases, the mold is integrally formed, and the hollow shaft part (in the direction perpendicular to the shaft)
has a continuous inner circumferential wall, giving it a so-called closed cross section.

As the slab solidifies and cools, it shrinks and its cross-sectional dimension becomes smaller. Therefore, in order to maintain contact between the mold and the slab, the mold hollow is pre-filled on the downstream side or with a smaller dimension. The part has a taper.

b) Mold in which a cylindrical body is formed by a plurality of mold elements that are separated and independent from each other: In order to obtain a slab with a relatively large cross section, following the mold of a) above, mold elements that are separated and independent from each other, A mold may be provided in which a plurality of mold elements movable in a direction perpendicular to the peripheral wall surface are arranged in a cylindrical shape. In this mold, the inner circumferential walls of each mold element are not brought into close contact with each other as in a) above, but are arranged with a gap between them, and each is pressed against the surface of the slab by the biasing force of a spring or cylinder. For example, when the slab has a rectangular cross section, mold elements are often placed only on the long sides, resulting in an incomplete cylindrical body. This is applicable not only to rectangular slabs but also to slabs with a circular cross section, but since there are gaps between the mold elements, it is possible to apply this to the part after the solidified layer has been formed on the surface of the molten metal, that is, on the downstream side of the mold in a) above. provided.

As mentioned above, the slab contracts as it solidifies and cools, but according to the mold b), each of the divided mold elements is reliably pressed against the surface of the slab, so there is no gap between them. Therefore, the slab can be reliably and uniformly cooled without creating any gaps. That is, this type of mold is provided instead of providing the above-mentioned taper in the hollow part of the mold, and is called a self-chieved mold, adjustable mold, cooling plate, or the like.

By the way, in conventional molds, regardless of whether the shape of the cylindrical body (mold) is a) or b), the mold is formed only of copper or copper alloy, which has high thermal conductivity, or
It was formed by placing a liner made of graphite or the like, which also has high thermal conductivity, in close contact with the inner circumferential wall. This is because unless a material with high thermal conductivity is placed in a state where heat transfers easily, the heat of the molten metal will not transfer to the cooling water.
This is because the mold (especially the inner peripheral wall) may become hot and melt. Regarding the mold a) above, please refer to 12. of "Steel Handbook ■". "continuous casting method" and Japanese Patent Publication No. 49-26812, etc.; on the other hand, b
) for the mold of “World 5teel &
Metalworking"Vol, 4 ・198
2, p. 160, etc.

(Problems to be Solved by the Invention) When performing continuous casting using a conventional mold, the following problem occurs. That is, when forming a cylindrical body (mold) as in a) above, cooling of the slab progresses unevenly, making it easy for the slab to deform and crack. If you try to solve this problem by replacing the mold with a mold, you will sacrifice safety in case the surface of the slab breaks.

This will be explained in detail below.

Generally, in the mold a) in which the mold is integrally formed,
The taper provided in the hollow part of the mold is determined in advance for each metal to be cast based on careful calculations and experiments. this is,
If the taper amount (reduction rate of cross-sectional dimension) of the mold is larger than the degree of shrinkage of the slab, the slab cannot be pulled out smoothly, and conversely, if the taper amount is small, there is a gap between the slab and the mold. This is because camps are formed, which impedes heat transfer and prevents the cooling (solidification) of the slab from proceeding. Since the thermal conductivity of air is several tenths of that of copper, heat transfer is extremely reduced when a cap is formed.

However, when continuous casting is actually performed, it is extremely rare for the slab to shrink along the taper of the mold. In other words, the degree of shrinkage of a slab changes depending on the casting (drawing) speed and the temperature of the molten metal, so even if the type (components) of the cast metal is the same, the degree of shrinkage will change with each casting or as time passes during casting. change. Additionally, as slabs solidify and cool, they rarely shrink in a manner similar to their original cross-section (in most cases, a circular cross-section deforms into an ellipse, or a rectangular cross-section becomes nearly diamond-shaped). Because it does.

As mentioned above, the thermal conductivity of the mold is very high, but if there is a gap between the surface of the slab and the mold, heat transfer is extremely hindered, so the slab deforms as described above and is unevenly molded. If there is contact with the gap, there will be a large deviation in the cooling intensity between the contact area and the gap area. This distribution of cooling intensity causes the slab to shrink so as to promote the above-mentioned deformation, so that partial cooling and deformation progress further by the time the slab leaves the mold. As a result, a non-uniform or asymmetric solidified structure is formed inside the slab, and cracks occur.

The mold in b), which presses the mold elements onto the surface of the slab, is connected downstream of the mold in a) to prevent uneven cooling and deformation of the slab. Because there is a gap between them, it cannot be expected to have the ability to repair breaks on the surface of the slab.In other words, if the surface of the slab (solidified layer) in the mold breaks for some reason during casting, if the mold in a) , - By temporarily stopping the drawing (or reducing its speed), the slab is repaired in the mold and the molten metal inside does not break out, but in case of b), the casting Molten metal flows out through the gaps between the elements. A breakout is extremely dangerous as the hot molten metal can damage molds and other equipment and cause personal injury. .

In order to prevent flake-out, there is a method of constantly measuring the temperature of the mold to detect breakage on the surface of the slab within the mold, but if the mold in a) is short, this method also does not work. There are problems involved. In other words, the broken part is a)
It is necessary to repair this before it comes out of the mold, so in this case, it is necessary to increase the sensitivity of fracture detection and to stop pulling out within a short time.

For example, the length of the mold in a) is 200 mm, the casting (
When the pulling speed is 2 m/min, it is necessary to detect the breakage and stop the pulling out within 6 seconds at the latest from the occurrence of the breakage. Generally, in continuous casting, the slab is pulled out while oscillating the slab or mold, so the temperature of the mold does not maintain a steady value even while casting is being performed normally. However, increasing the detection sensitivity and immediately stopping the drawing increases the chance of erroneous operations, such as stopping the drawing even though the slab is not broken, which worsens operational efficiency.

To summarize the above, conventional molds have problems regardless of the form of the cylindrical body (mold), and it is difficult to prevent breakout and uneven cooling.

(Purpose of the Invention) This invention was made to solve the above-mentioned problems.It has a function of repairing fractures on the surface of the slab, prevents breakouts, and also prevents uneven cooling of the slab. The object is to provide a continuous casting mold that can minimize deformation and cracking.

(Means for Solving the Problems) The gist of the present invention to achieve the above object is to integrally form a cylindrical mold, give its hollow shaft a circular or polygonal cross section, In a continuous casting mold in which the outer peripheral wall of the mold is cooled with a water bath, the molten metal supplied to the hollow shaft is continuously cooled and solidified into slabs, and the shaft of the inner peripheral wall of the mold is An interior material made of a heat-resistant material is attached to a part of the direction, and a gap is provided at an appropriate location at the contact area between the interior material and the mold.

(Function) According to the continuous casting mold of the present invention, at a proper location in the mold, that is, at a location where an interior material is attached and a void is provided at the contact area between the interior material and the mold, the insulation effect of the void allows the casting to be performed. Since heat transfer from the piece to the cooling water is restricted,
Even if the cross section of the slab is deformed and comes into contact with the mold non-uniformly, there will be no extreme deviation in the cooling strength, and the progress of uneven cooling and deformation will therefore be suppressed. Furthermore, since the cylindrical mold is integrally formed, even if the surface of the slab inside the mold breaks for some reason during casting, it can be repaired and breakout can be prevented.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. 1 and 2 are a longitudinal sectional view and a cross sectional view of essential parts of a mold for horizontal continuous casting of steel according to the first embodiment.

As shown in FIG. 1, in horizontal continuous casting, a mold A is connected to a tundish E for storing molten steel M, and a drawing roll F is disposed downstream of the mold A. Therefore, the molten steel M is supplied to the tundish E and once stored there, and then flows into the mold A where it is cooled and turned into a slab C which is continuously drawn out by the rolls F.

At this time, the molten steel M flows into the mold A through the nozzle Ea of the tundish E and the connecting refractory Eb, but from the time it comes into contact with the inner peripheral wall of the mold A, a solidified layer Ca is formed sequentially from the contact surface, that is, from the outer periphery. A slab C is formed.

Since the equipment shown in the figure is for obtaining slabs with a circular cross section, mold 1 of mold A has a diameter on its inner periphery that takes into account shrinkage of the slab during cooling, and a diameter that takes into account shrinkage in the casting direction. It is formed into a cylindrical shape with a taper. Since the mold 1 is a so-called tubular mold formed from a single piece of copper alloy, the hollow shaft portion is a closed circle. Mold A is equipped with a cooling water jacket 3 and a partition pipe 3a on the outside of the mold 1, so that the supplied cooling water flows through the mold 1.
It is designed to flow along the outer peripheral wall of the. In addition, a thermocouple 4 is inserted into the upstream part of the mold 1, and a thermocouple 4 is inserted into the upstream part of the mold 1.
Since the temperature of the slab is measured, it is possible to detect abnormalities such as fractures in the slab.

In this embodiment, a portion of the inner circumferential wall of the mold 1 on the downstream side is enlarged in diameter, and a graphite liner 2 having a shallow recess 2a in the outer circumferential wall is attached thereto. Since the graphite liner 2 has heat resistance and self-lubricating properties, the slab C can be drawn out smoothly.

The inner diameter of the liner 2 was determined to match that of the mold 1, and the portion of the mold 1 where the liner 2 was not attached and the liner 2 were connected so that there were no steps or gaps on the inner peripheral wall. On the other hand, the recesses 2a provided in the outer circumferential wall of the liner 2 were provided on the downstream side of the liner 2, as shown in FIG. Liner 2 is installed by shrink fitting mold 1.
was attached to the enlarged diameter part of the mold 1, so the four convex parts are in close contact with the mold 1, but the remaining recesses 2a are attached to the mold 1 and the liner 2.
There is a gap 2a between the two.

When continuous casting is performed using mold A of this embodiment, cooling of the slab proceeds as follows.

The molten steel M flowing into the mold A from the tundish E is
First, the part where the liner 2 is not installed is strongly cooled by contacting the mold 1 with high thermal conductivity, and a solidified layer Ca is formed on the outer periphery.
generate. As the slab C is pulled out by the rolls F, the solidified layer Ca moves downstream, or by the time it reaches the part where the liner 2 is attached, in many cases the slab C (solidified layer Ca) is slightly deformed and mold 1 (
Alternatively, a cap G is formed on a part of the contact portion with the inner circumferential wall of the liner 2), resulting in an uneven contact state. This solidified layer Ca will soon reach the part where the cavity 2a is provided between the mold 1 and the liner 2, or here, the heat transfer is restricted by the insulation effect of the cavity 2a, so the solidified layer Ca will not reach the part where the cavity 2a is provided between the mold 1 and the liner 2. Even if there is uneven contact with the liner 2, there will be no extreme deviation in the cooling intensity. Therefore, deformation and partial cooling do not proceed beyond this point, and it is therefore possible to obtain a high-quality slab with a cross section that is close to a perfect circle (and an internal solidified structure that is approximately axially symmetrical and free from cracks).

From the above points, it is preferable that the part of mold A without the void 2a be short, or the part with the void 2a should be short.
Since heat transfer is restricted, the required thickness of the solidified layer Ca
It is desirable to make it somewhat longer in the axial direction in order to obtain However, since the deviation in cooling strength is small in the part with the void 2a, even if this is lengthened to extend the entire length of the mold A, deformation and partial cooling will not proceed; on the contrary, the surface of the slab C (solidification Layer C
There is an advantage that it becomes easier to deal with the breakage of a). In other words, even when detecting an abnormality in the temperature of thermocouple 4 or mold l, the breakage can be repaired by stopping (or slowing down) the drawing process before the broken part comes out of mold A, so there is no need to operate incorrectly. breakout can be reliably prevented. Further, since the cooling of the slab C proceeds gradually, it is also suitable for casting high carbon steel or high alloy steel, which are prone to cracking by rapid cooling.

Here, mold 1 (thickness 10 mm) and liner 2 (thickness 10 mm)
Let's quantitatively consider the transfer of heat in the part where the gap 2a (0.3 mm) is provided between the gap 2a and the gap 2a (0.3 mm) based on FIG. FIG. 2 is a cross-sectional view of a portion of the mold A having the cavity 2a, excluding the cooling water jacket 3 and the partition pipe 3a. In this figure, the thickness of the coagulated layer Ca is 10 mm, and it is assumed that the solidified layer Ca is deformed into a slightly oval shape in the vertical direction.

The slab C and the liner 2 are in contact in the vertical direction S1, but in the horizontal direction S2, the thickness is 0.2 mm.
The cap G has occurred.

The heat of the molten steel M is the solidified layer Ca, the gap G (for S2)
, the liner 2, the cavity 2a, and the mold 1, and are transmitted to the cooling water on the outer peripheral wall thereof. The heat transfer coefficient between the molten steel M and the solidified layer Ca is α8, the heat transfer coefficient between the mold l and the cooling water is α,
Solidified layer Ca, gap (air) G, liner (graphite) 2,
Thermal conductivity λ regarding the cavity 2a and the mold (copper alloy) 1
and the thickness t, respectively, [λC, t c] - [25 (kcal/mh'c),
0.01(m)][λ. , t G] −[o, os(
”), o, uo2(〃)] [λL, t L] =
Ctu(〃), Q, Ql('')3[λ, t A]
-[0,05(''), 0.0003('')][λ,,
,,t,] −[2oo(〃), o,ox(”)
] (Accurately speaking, the thermal conductivity λ of each part varies somewhat depending on the temperature, but the above is a typical value at the approximate temperature of = 16 - during casting.) If we consider the cylindrical wall to be a flat plate, then , the heat transfer resistance R from the molten steel M to the cooling water is: R= RM+ Rc+ RG+ Rt, + RA+ R
It is expressed as ffl+Rw. However, the heat transfer resistance of each part is RM=1/α8, Rc=tc/λ. , Rc=tc/λo
1RL"'tL/λ5, RA=tA/λ9, R11, -
7i/λ, R, = 1/α0 In general, the amount of heat proportional to the reciprocal of this resistance R moves from the molten steel M toward the cooling water.

Here, if we enter numerical values into α, λ, and t, RM+Rw=
0.00105 (m'h'c/kcal) Rc=tc
/λc=0.0004 (〃)Ra=ta/λ. -0
,004(〃)・82 direction RL-tL/λ, = 0.0
001 ('')RA-tA/λ=0.006(l/
) R, -t, /λ, n= o, 00005 (〃). From this, the heat transfer resistance R towards S2 is R=0.
0116 (m2h°C 8 cal) On the other hand, R for Sl direction where Rc=O is R = 0.0076 (m”h'c/kcal) That is, the part where slab C and liner 2 are in contact (31 direction) The amount of heat transfer between the two and the part where there is a gap G between the two (S
2 orientation) is 0, 011610.0076
= 1.53, which is small.

If the cavity 2a is not provided in the mold A, the heat transfer resistance R, excluding RA from the above value, is for S2: R=
0.0056 (m2h0c/kcal) For S1
R=0.0016(〃), and the above ratio is as large as 0,005610.0O1B=3°5, resulting in a significant deviation in cooling strength.

In mold A of this example, heat transfer is restricted by the heat insulating effect of the cavity 2a, but this causes the liner 2 to overheat and easily melt (burn out) (this point will be dealt with as follows). (a) If the liner 2 comes into direct contact with the molten steel M without passing through the solidified layer Ca, the liner 2 is likely to overheat, so if the slab breaks, stop drawing as soon as possible to avoid erroneous operation. Repair this. a) When casting with a high drawing speed, a different liner with a smaller area or thickness (depth) of the cavity 2a is installed. c) When increasing the drawing speed further,
When the liner 2 and the cavity 2a are provided in the upstream part of the mold A, the liner (interior material) is made of a ceramic material such as boron nitride or a superalloy material such as Hastelloy, which has higher heat resistance than graphite. Form and install.

Next, a second embodiment of the present invention will be described based on FIGS. 3 to 5.

FIG. 3 relates to a mold for horizontal continuous casting of steel for obtaining slabs with a rectangular cross section.

As in FIG. 1, the left side of the figure is connected to a tundish (not shown), and the slab is pulled out to the right and cast. Figure 4 is a cross-sectional view of section IV-'■ in Figure 3, excluding the cooling water jacket 13 and partition pipe 13a, and Figure 5 is the same view as section IV-V in arrow direction -19-. .

Mold B1 shown in FIG. 3 is a so-called assembled mold, and is formed into a closed cylindrical shape with a rectangular cross section by bringing four mold elements 11a corresponding to the four sides and the same number of mold elements 11b into close contact with each other and physically fastening them. A mold 11 is formed. A cooling structure consisting of a cooling water jacket 13 and a partition pipe 13a is provided on the outside of the mold 11, and the mold element 1
A thermocouple 4 for detecting abnormalities in the slab is inserted into the upstream portion of 1a.

Downstream of mold B1 are the aforementioned adjustable molds, that is, four separate and independent molds as shown in FIG.
A mold B2 in which two mold elements 21 are pressed against four surfaces of a slab by the urging force of a spring 34 whose one end is fixed to a frame 35, and a mold B3 having the same configuration are connected. Note that both molds B2 and B3 have mold elements 21.
31 is equipped with a graphite liner 22, 32 on its inner circumferential wall, and a cooling water jacket 23, 33 and partition pipes 23a, 33a are provided on its outer circumferential wall. With these molds B2 and B3, even if the slab shrinks, the liner 22, 32 always comes into contact with it, so that solidification can proceed uniformly and reliably. Furthermore, compared to cooling by water spray, it is effective in preventing bulging of slabs (bulging due to internal pressure).

The feature of the mold B1 of this embodiment is that a shallow groove-shaped recess 11c along the casting direction is provided on the downstream inner peripheral wall of the downstream mold element 11b of the mold 11, and on the inside thereof,
The graphite liner 12 is installed over the entire length of the mold element 11b. Since the upstream convex portion of the liner 12 is sandwiched between the mold elements 11a and 11b, the installation position will not shift. Further, the inner circumferential wall was designed to have no step or gap between it and the inner circumferential wall of the mold 11a.

FIG. 4 is a cross-sectional view of this part, and as shown in the figure, the liner 12 is also installed so that the four elements are assembled in close contact with each other, like the mold 11.

Moreover, the recess 11c of the mold element 11b is located at 4 in the rectangular hollow part.
They are concentrated near the two corners and the bottom surface, and form a gap 11c with the liner 12. This is because the corners of a rectangular slab are cooled from two orthogonal sides, so if heat transfer is not restricted, the slab will cool too quickly, deforming it into a diamond shape, or causing cracks in the solidified structure. This takes into account the fact that in horizontal continuous casting, only the lower surface of the slab often comes into contact with the liner 12 due to the influence of gravity.

In the mold B1 of this embodiment, as in the case of the previous embodiment, heat transfer in the portion provided with the cavity 11c is restricted, so that the slab is deformed and uneven before it is pulled out and leaves the mold B1. There is no progress in cooling. In other words, even if some diamond-shaped deformation occurs in a part of the slab in the upstream part of the mold B1, and it reaches the liner 12 and comes into contact with the inner circumferential wall unevenly, the part that tends to come into contact (the corner (near the lower surface) is provided with a cavity 11c that has a heat insulating effect.
There is no uneven cooling, and therefore no deformation progresses.

The slab is further pulled out and molds B2 and Mold B
3, each side of the slab except the four corners will be covered with 3
4, the liners 22 and 32 are pressed against each other to uniformly cool the slab, resulting in a high-quality slab with an extremely accurate rectangular cross section, a symmetrical solidified structure inside, and no cracks. be able to.

In the mold Bl, the hollow part of the closed cross section can be lengthened without causing deformation and uneven cooling of the slab, so that even when the surface of the slab breaks, as in the previous embodiment, the thermocouple 4 is connected to the mold 11a. If abnormalities in wet coal are detected, breakouts can be reliably prevented without any erroneous operation.

In this embodiment as well, the cavity 11c can have a different size or be provided at a different location, and the liner 12 can also be made of an interior material made of ceramic or heat-resistant metal other than graphite. Also, mold B1
The molds B2 and B3 following the molds B2 and B3 may be arranged in series at an appropriate distance in the axial direction.

The above two embodiments have been shown for horizontal continuous casting molds for steel, but the continuous casting mold of the present invention can also be of vertical type (vertically oriented) or inclined type, and can also be used for continuous casting of metals other than steel. I can do something. Further, it is also easy to form the hollow shaft portion as a curved mold.

Furthermore, since the cooling intensity at an appropriate location can be adjusted according to the shape of the cross-section of the slab, it is suitable for obtaining slabs with a special cross-sectional shape, not just circular or rectangular shapes.

(Effects of the Invention) The continuous casting mold of the present invention described above provides the following effects.

1) Since partial cooling of the slab is not allowed to progress, deformation and cracking can be minimized, and a high-quality slab with a symmetrically formed solidification structure can be obtained.

2) Since the cylindrical mold is integrally formed, it has the function of repairing breaks on the surface of the slab, making it possible to reliably prevent breakouts.

3) Since the cooling intensity can be freely adjusted by restricting heat transfer, it can also be used for casting metals with high crack susceptibility or slabs with special cross-sectional shapes.

4) It can be easily adapted to changes in casting material and casting speed by simply changing the dimensions and arrangement of the voids.

[Brief explanation of the drawing]

The drawings all show a mold for horizontal continuous casting of steel; FIG. 1 is a vertical sectional view of the mold relating to the first embodiment, FIG. 3 is a vertical sectional view of a mold related to the second embodiment, FIG. 4 is a sectional view of a main part taken along the line IV-IV in FIG. 3, and FIG. 5 is a view taken along the line V-V in FIG. 3. . A, Bl, B2. B3- Mold, C, D
・・Slab, E・・Tendishu, G・Gap, M
... Molten steel, 1, 11-Mold, 2, 12.22.32
= liner, 2a, 1lc-gap (recess), lla
, llb, 2L31-template element.

Claims (4)

[Claims] (1) A cylindrical mold is integrally formed, its hollow shaft is given a circular or polygonal cross section, and the outer circumferential wall of the mold is cooled with a water bath to supply water to the hollow shaft. In continuous casting molds, in which molten metal is continuously cooled and solidified to form slabs, an interior material made of a heat-resistant material is attached to a portion of the inner peripheral wall of the mold in the axial direction. A mold for continuous casting that has voids at appropriate locations where the material and mold come into contact. (2) The continuous casting mold according to claim 1, further comprising a coaxially disposed subsequent mold portion in which a cylindrical mold is formed by a plurality of mold elements that are pressed against the surface of the slab separately and independently from each other. . (3) The continuous casting mold according to claim 1 or 2, wherein the void portion is provided near a corner of the hollow shaft portion. (4) The continuous casting mold according to any one of claims 1 to 3, wherein the gap groove is provided near the lower surface of the hollow shaft portion.