JP2006346734A - Continuous casting mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous casting mold, which produces a cast slab of good quality by suppressing, further preventing, generation of cracks in a cooling plate and stably maintains quality for a period longer than those of conventional continuous casting molds. <P>SOLUTION: The casting mold comprises a cooling plate 11, which is provided with a large number of water guiding grooves 20 on its back surface, and a supporting member 19, which is fixed to the back surface side of the cooling plate 11 via O-rings 23 surrounding the water guiding grooves 20 by fitting means 13-18 provided at predetermined intervals in a vertical direction. The mold produces a cast slab by cooling the cooling plate and further cooling molten steel by allowing cooling water to flow into each of water guiding grooves 20 through water feeding parts 21 and water discharging parts 22 of the supporting member 19. The fitting means 13-18 are formed so as to avoid a meniscus part 12 of the cooling plate 11. The fitting interval D between fitting means 13, 14, which are positioned above and under the meniscus part 12, are made wider than the fitting intervals on the other part of the plate 11. Further, recessed parts corresponding to a thermal expansion amount of the meniscus part 12 at the time of producing the cast slab are formed on the surface side of the meniscus part 12 of the cooling plate 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a continuous casting mold for casting molten steel.

Conventionally, a continuous casting mold (hereinafter also simply referred to as a mold) used in a continuous casting facility has a pair of narrow cooling members (also referred to as short piece members) sandwiched between the short side members. A long side member (also referred to as a long piece member) that is a pair of wide cooling members that are arranged, bolts are attached to both ends of the opposing long side member, and the short side member is fixed with a nut via a spring It has a structure.
As shown in FIGS. 5 (A) and 5 (B), the long side member has a copper plate (an example of a cooling plate) 81 in which a large number of water guide grooves 80 are provided in the vertical direction on the back surface, and a predetermined length on the back surface side of the copper plate 81. And a back plate (also referred to as a cooling box) 82 which is an example of a support member fixed by bolts provided at a mounting interval of. A drainage portion 83 and a water supply portion 84 are respectively provided at the upper end portion and the lower end portion of the back plate 82 on the side in contact with the copper plate 81, and the cooling water flowing in from the water supply portion 84 is passed through the water guide groove 80 to the drainage portion 83. To cool the copper plate 81. In addition, an O-ring 85 is disposed between the copper plate 81 and the back plate 82 so as to surround the water guide groove 80, the drainage part 83, and the water supply part 84, thereby preventing water leakage from the long side member. The short side member also has substantially the same configuration as the long side member except that its width is different, and the mold body is composed of the copper plates of the long side member and the short side member (for example, patents) Reference 1).
Then, the molten metal is supplied to the mold having such a configuration, and the slab is manufactured by blowing cooling water while continuously drawing the slab formed by solidification in the mold downward.

JP 2003-136204 A

However, the above-described continuous casting mold has the following problems.
As shown in FIG. 5A, a conventional copper plate of a mold, particularly a thin copper plate such as a magnetic stirring mold, has a dense pitch (for example, 50 mm or more and less than 150 mm) for the purpose of preventing thermal deformation. The bolt is fastened with the back plate. For this reason, restraint distortion generate | occur | produced in the copper plate and it was easy to generate | occur | produce a crack.
Further, in recent years, the heat load on the meniscus portion of the copper plate has increased more than before due to the increase in casting speed or the influence of electromagnetic stirring. Therefore, in the overtightened bolt fastening structure, a large restraint strain is applied to the meniscus portion of the copper plate. It was easy to generate a crack.
Thus, when a crack generate | occur | produces in a copper plate, there existed a possibility of reducing slab quality and a mold lifetime significantly, for example.

The present invention has been made in view of such circumstances, and can suppress the generation of cracks in the cooling plate, further prevent it, manufacture a slab of good quality, and maintain stable quality for a longer period of time than before. An object of the present invention is to provide a continuous casting mold.

The continuous casting mold according to the present invention that meets the above object includes a cooling plate provided with a plurality of water guide grooves on the back surface, and a plurality of mounting means provided at predetermined mounting intervals in the vertical direction of the cooling plate. A support member fixed on the back side of the plate via an O-ring surrounding the water guide groove, and flowing cooling water to each water guide groove through a water supply portion and a drainage portion provided on the support member. In the continuous casting mold for producing the slab by cooling the cooling plate and cooling the molten steel,
The attachment means is provided avoiding the meniscus portion of the cooling plate, the attachment interval of the attachment means positioned above and below the meniscus portion is wider than the attachment interval of other portions, and the meniscus of the cooling plate On the surface side of the part, dent processing corresponding to the thermal expansion amount of the meniscus part at the time of manufacture of the slab is made.

In the continuous casting mold according to the present invention, it is preferable that the meniscus portion is in a range of 50 mm or more and 150 mm or less downward from an upper end position of the cooling plate.

In the continuous casting mold according to the present invention, the attachment position of the attachment means located above the meniscus portion is preferably within a range of 60 mm downward from the upper end position of the cooling plate.

Furthermore, in the continuous casting mold according to the present invention, it is preferable that an attachment interval of the attachment means positioned above and below the meniscus portion is 150 mm or more and 250 mm or less.

The continuous casting mold according to any one of claims 1 to 4 can be provided by providing a mounting interval between the mounting means positioned above and below the meniscus portion without providing the mounting means on the meniscus portion that becomes a high heat load. The restraining force by the support member of the meniscus portion of the cooling plate can be relaxed, and the amount of the cooling plate that can be freely deformed can be made larger than before. Thereby, generation | occurrence | production of the restraint distortion in the meniscus part of a cooling plate can be relieve | moderated, and generation | occurrence | production of the crack of a meniscus part can be suppressed.
In addition, by performing dent processing corresponding to the thermal expansion amount of the meniscus part at the time of casting on the surface side of the meniscus part of the cooling plate, it can be deformed to the target shape even when using a continuous casting mold. And a slab with good quality can be manufactured.

In particular, since the continuous casting mold according to claim 2 defines the position of the meniscus portion, the attachment means can be provided at an appropriate position where the influence of restraint strain can be suppressed.

According to the third aspect of the present invention, the continuous casting mold prescribes the mounting position of the mounting means positioned above the meniscus portion, so that the influence of restraining strain on the cooling plate by the mounting means can be suppressed.

The continuous casting mold according to claim 4 regulates the mounting interval of the mounting means positioned above and below the meniscus portion, so that the influence of restraining strain on the cooling plate by the mounting means can be further suppressed, and the cooling plate for the support member Can be installed securely.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1A is a rear view of the cooling plate of the long side member of the continuous casting mold according to the embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along the line aa in FIG. FIG. 2 is an explanatory view showing a cooling plate shape when casting a slab using a continuous casting mold.

As shown in FIGS. 1A and 1B, a continuous casting mold (hereinafter also simply referred to as a mold) according to an embodiment of the present invention is a pair of narrow cooling members (short pieces). And a long side member (also referred to as a long piece member) 10 which is a pair of wide cooling members, and the long side member 10 is configured when the slab is manufactured. This suppresses the generation of cracks in the meniscus portion 12 (near the molten steel surface) of the cooling plate 11. The long side member 10 and the short side member of the continuous casting mold have substantially the same configuration, and the cooling plate 11 of the long side member 10 and the cooling plate of the short side member constitute a mold body. Therefore, the long side member 10 will be described in detail below.

The long side member 10 includes a cooling plate 11 and a back plate (also referred to as a cooling box or a water box) 19 which is an example of a support member fixed to the back side of the cooling plate 11 by a plurality of attachment means 13 to 18. ing.
The cooling plate 11 (for example, about 10 mm to 100 mm in thickness) is made of copper or copper alloy, which is an example of a metal having good thermal conductivity, and a large number of water guide grooves 20 (here, on the back side). 11) are provided. Each water guide groove 20 is formed at a predetermined pitch (for example, about 10 mm or more and 40 mm or less) in the width direction of the cooling plate 11, and the depth thereof is, for example, 1/3 or more and 2/3 of the thickness of the cooling plate 11. It is about the following.

The back plate 19 (for example, about 50 mm or more and 500 mm or less in thickness) is made of, for example, stainless steel, and a water supply unit 21 and a drainage unit 22 are provided at a lower part and an upper part of the back plate 19 on the side where the cooling plate 11 contacts. Grooves are formed around the cooling plate 11 side of the back plate 19 so as to surround the water supply portion 21, the drainage portion 22 of the back plate 19, and the water guide groove 20 of the cooling plate 11, and an O-ring 23 is disposed in this groove. is doing.
The cooling plate 11 has a female screw portion, and a back plate 19 is fixed to the back side of the cooling plate 11 by a male screw (for example, a bolt) that is screwed into the female screw portion. In addition, a seal washer that can be waterproofed is disposed in advance in a hole (not shown) formed in the back plate 19 for attaching the male screw. The female screw portion and the male screw constitute attachment means 13 to 18 (18 places in total here), and the plurality of attachment means 13 to 18 are provided at predetermined attachment intervals in the width direction and the vertical direction of the cooling plate 11. It has been.

Here, the determination method of the attachment position of the some attachment means 13-18 is demonstrated.
As shown in FIG. 2, the thermal stress of the cooling plate is generated when there is a temperature difference between the front surface and the back surface and the back surface side is constrained (displacement constrained). Here, a thermal stress solution σt of a flat plate in which the surface of the cooling plate is set to a high temperature and the back surface is set to a low temperature, and the bending of the back side of the cooling plate is completely prevented is shown below.
σt = ± β · ΔT · E / 2 (1-ν)
β: Linear expansion coefficient (1 / ° C)
ΔT: (surface temperature)-(back surface temperature) (° C)
E: Young's modulus (kg / mm ² )
ν: Poisson's ratio Here, the surface of the cooling plate has a value of “−” and compressive stress acts, and the back surface has a value of “+” and tensile stress acts.
In addition, even if there is a temperature difference between the front and back, if there is no constraint on the back, there will be free deformation and no stress will be generated.

In addition, the occurrence of cracks in the meniscus portion of the cooling plate is presumed to be governed by low cycle fatigue failure. In particular, in a mold that receives a high thermal load in the vicinity of the meniscus portion of the cooling plate, such as a high-speed casting mold or an electromagnetic stirring mold, the stress state on the surface of the cooling plate during casting reaches the normal plastic region. The mold is repeatedly exposed to a hot state and a cold state, and the stress amplitude is repeated due to the fluctuation of the molten metal surface during casting. For this reason, it is estimated that the cooling plate surface is in a low cycle fatigue state (fatigue life: 10 ³ <Nf <10 ⁵ ).
In this low cycle fatigue state, since the fatigue life Nf is dominated by plastic strain, the following Manson-Coffin equation (1) holds.

εp · Nf ⁿ = Cp (1)
εp: plastic strain amplitude n, Cp: material constant Nf: fatigue life (times)
This equation (1) is arranged for the fatigue life Nf.
Nf ⁿ = Cp / εp (1 ′)
From equation (1 ′), it can be seen that the greater the plastic strain amplitude εp, that is, the greater the absolute value of the thermal stress solution σt, the shorter the fatigue life Nf and the earlier cracking occurs.

Here, as a structural measure for extending the fatigue life Nf, a method of reducing the temperature difference between the front and back surfaces of the cooling plate by reducing the thermal stress solution σt, that is, by performing strong cooling to reduce ΔT. And there is a method of loosening the bending restraint on the back side.
In the cooling plate of the electromagnetic stirring mold, a thin cooling plate is used in order to suppress eddy current loss, and large thermal deformation is likely to occur in the cooling plate. And in order to prevent this thermal deformation, the number of bolt fastening is increased and the bolt pitch is made dense. In this way, by arranging the fastening bolts in an overly dense manner, the bending restraint on the back surface of the cooling plate is strengthened and the stress state is deteriorated, so the plastic strain of the cooling plate is increased and the fatigue life is also shortened. .
Therefore, of the two methods described above, an effective method for solving this is to reduce the number of attachment means in the vicinity of the meniscus portion that becomes a high stress portion.

As shown in FIG. 1A, the attachment means 13 located above the cooling plate 11, that is, above the meniscus portion 12, is provided within a range X from the upper end position P of the cooling plate 11 to 60 mm downward. Here, the meniscus portion 12 is located within the range of 50 mm or more and 150 mm or less downward from the upper end position P of the cooling plate 11 (preferably, the lower limit is 70 mm and the upper limit is 130 mm). The attachment position of the attachment means 13 is set above. Thereby, the restraint distortion by the attachment means 13 can be prevented from affecting the meniscus part 12.
From this, the range X of the mounting position of the mounting means 13 is preferably set to 50 mm downward from the upper end position P of the cooling plate 11.

Further, the mounting interval D between the mounting means 13 and the mounting means 14 positioned above and below the meniscus portion 12 is set to 150 mm or more and 250 mm or less. This avoids the meniscus portion 12 of the cooling plate 11 by the mounting means 13 and 14 positioned above and below the cooling plate 11 and reduces the influence of the restraining strain on the meniscus portion 12 by the mounting means 13 and 14.

In addition, each attachment of other attachment means 14,15, attachment means 15,16, attachment means 16,17, attachment means 17,18 except the attachment space | interval D of the attachment means 13 and 14 located in the upper side of the cooling plate 11 is carried out. The interval is the same as that of the conventional cooling plate, for example, 50 mm or more and less than 150 mm.
In addition, since the thermal load is not applied at the end of the cooling plate of the long side member (outside the alignment position of the short side member that is a portion where the molten steel does not contact), each mounting interval of the mounting means is the same as the conventional mounting interval. The same level is acceptable.
As described above, the number of attachment means in the vicinity of the meniscus portion 12 is reduced, and the attachment interval D of the attachment means 13, 14 is made wider than the attachment interval of the other attachment means 14 to 18, thereby reducing the stress of the cooling plate 11. It becomes possible.

However, by reducing the number of attachment means for attaching the cooling plate 11 to the back plate 19, the restraining force of the cooling plate 11 is reduced, and the deformation amount of the cooling plate is increased. Therefore, a recess 24 is formed on the surface side of the meniscus portion 12 of the cooling plate.
The recess 24 has a cooling plate surface so that the meniscus portion 12 is thermally expanded during casting, and as a result, the surface of the cooling plate 11 has a target profile (a shape inclined downward toward the center of the mold). It is formed by performing profile processing (dent processing) in which thermal deformation is canceled on the side. The recess 24 is provided with an abrupt recess (for example, a depth of about 0.05 mm or more and 1.0 mm or less from the surface of the cooling plate 11 on which the recess processing is not performed) at the hot water surface position, and toward the lower side of the cooling plate 11. It is a shape that gently reduces the amount of dents.
Note that this profile processing can be performed by predicting the deformation amount of the cooling plate 11 by numerical analysis based on the known operating conditions during casting and cooling conditions of the cooling plate.
Thereby, the shape (taper) collapse of the cooling plate 11 due to thermal deformation can be prevented.

Using the continuous casting mold having the above-described configuration, cooling water is supplied to each water guide groove 20 from a water supply port (not shown) provided in the water supply section 21 on the lower side of the back plate 19, and the cooling plate 11. Cooling water (for example, industrial water) that flows from the lower side to the upper side is discharged from a drain port (not shown) provided in the drainage unit 22 on the upper side of the back plate 19 to cool the cooling plate 11. Yes. At this time, since the adhesion between the cooling plate 11 and the back plate 19 is improved by the O-ring 23, the leakage of the cooling water from the water guide groove 20 when discharging from the drainage part 22 is prevented.
Thus, while suppressing the generation | occurrence | production of the crack to the cooling plate 11, while cooling the cooling plate 11, while cooling molten steel, a slab with favorable quality can be manufactured.

Next, FEM improvement examination results (hereinafter referred to as improvement examples) performed to confirm the operational effects of the present invention will be described. 3A is a partial perspective view of a cooling plate for a continuous casting mold according to an improved example of the present invention, and FIG. 3B is a partial perspective view of a cooling plate for a continuous casting mold according to a conventional example. (A) is explanatory drawing of the analysis result of a cooling plate thermal deformation at the time of changing the attachment position of a volt | bolt, (B) is explanatory drawing of the analysis result of the thermal influence by the dent process to the meniscus part of a cooling plate.

As shown in FIG. 3A, bolts 31 to 33 are provided in the vertical direction on the upper side of the cooling plate 30 of the mold according to the improved example, and the bolt 31 is 40 mm from the upper end of the cooling plate 30 (in the above-mentioned range X). ) At the lower position, the distance between the bolt 31 and the bolt 32 is 170 mm (within the mounting distance D), and the distance between the bolt 32 and the bolt 33 is 100 mm. On the other hand, as shown in FIG. 3B, bolts 35 to 38 are provided in the vertical direction above the cooling plate 34 of the mold according to the conventional example, and the bolt 35 is mounted at a position 40 mm below the upper end of the cooling plate 34. The intervals between the bolts 35 and 36, the bolts 36 and 37, and the bolts 37 and 38 were 60 mm, 100 mm, and 100 mm, respectively.

As described above, the bolts 31 to 33 located on the upper side of the mold cooling plate 30 according to the improved example are removed from the second stage bolt 36 of the mold cooling plate 34 according to the conventional example, and the meniscus of the cooling plate 30 is removed. The portion 39 (here, a position of 100 mm downward from the upper end of the cooling plate 30) is avoided, and the mounting interval between the bolts 31 and 32 positioned above and below the portion is wider than the interval between the bolts 32 and 33. The meniscus portion 39 of the mold cooling plate 30 according to the improved example is recessed to form a recess.

First, the influence of the mounting position of the bolt will be described. Here, the bolt is provided at the same position as the cooling plate 30 according to the improved example, and the concave portion is not provided in the meniscus portion so that other factors do not affect. I am using something.
As shown in FIG. 4 (A), by using a cooling plate (solid line) in which the upper and lower bolts of the meniscus are widened, it is possible to eliminate the restraint of the cooling plate by the meniscus bolt. The amount of thermal deformation (free deformation) can be made larger than that of the cooling plate 34 of the mold according to (dotted line). Therefore, the cooling plate having a wider bolt mounting interval can relieve the plastic strain than the cooling plate 34 of the mold according to the conventional example, and its fatigue life is equal to the fatigue life of the cooling plate 34 of the mold according to the conventional example. It is estimated that it can be improved about 1 time.

Next, the influence of the recess processing of the cooling plate 30 of the mold according to the improvement example will be described with reference to FIG. Here, the cold state (dashed line) means the surface shape of the cooling plate 30 at room temperature, and the casting (hot state: solid line) means the surface shape of the cooling plate 30 that is thermally expanded during casting. Means.
As shown in FIG. 4 (B), the deformation amount of the cooling plate 30 is numerically analyzed on the basis of the previously known operating conditions during casting, and dent processing is performed. Without generating a local thermal expansion portion, it is possible to ensure a predetermined shape, that is, a shape in which the inner width of the cooling plates arranged opposite to each other is reduced toward the lower side of the mold.
Thereby, a cast with good quality can be manufactured by using this mold.

As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, the case where the continuous casting mold of the present invention is configured by combining some or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention.
Moreover, in the said embodiment, although the attachment position of the attachment means of a long side member was demonstrated, attachment of the attachment means only about both a long side member and a short side member, or only a short side member was demonstrated as needed. It is also possible to set the position. Here, when the long side member is wide, if necessary, the meniscus portion is removed at the height position of the cooling plate corresponding to the meniscus portion, and the attachment means is attached only to both ends in the width direction of the long side member. It is also possible to provide. The same applies to the short side member.

(A) is a rear view of the cooling plate of the long side member of the casting mold for continuous casting according to an embodiment of the present invention, and (B) is a cross-sectional view taken along the line aa in FIG. It is explanatory drawing which shows the cooling plate shape at the time of casting a slab using the casting mold for continuous casting. (A) is a partial perspective view of a cooling plate of a continuous casting mold according to an improved example of the present invention, and (B) is a partial perspective view of a cooling plate of a continuous casting mold according to a conventional example. (A) is explanatory drawing of the analysis result of a cooling plate thermal deformation at the time of changing the attachment position of a volt | bolt, (B) is explanatory drawing of the analysis result of the influence by the dent process to the meniscus part of a cooling plate. (A) is a rear view of the long side member of the casting mold for continuous casting according to the conventional example, and (B) is a cross-sectional view taken along the line bb in FIG. 5 (A).

Explanation of symbols

10: Long side member, 11: Cooling plate, 12: Meniscus part, 13 to 18: Mounting means, 19: Back plate (support member), 20: Water guide groove, 21: Water supply part, 22: Drain part, 23: O Ring, 24: recessed portion, 30: cooling plate, 31-33: bolt, 34: cooling plate, 35-38: bolt, 39: meniscus portion

Claims (4)

A cooling plate provided with a large number of water guide grooves on the back surface and a plurality of attachment means provided at predetermined mounting intervals in the vertical direction of the cooling plate via an O-ring surrounding the water guide grooves on the back surface side of the cooling plate. The cooling plate is cooled and the molten steel is cooled by flowing cooling water into each of the water guide grooves through a water supply portion and a drainage portion provided on the support member. In a continuous casting mold for producing a slab by performing
The attachment means is provided avoiding the meniscus portion of the cooling plate, the attachment interval of the attachment means positioned above and below the meniscus portion is wider than the attachment interval of other portions, and the meniscus of the cooling plate The mold for continuous casting is characterized in that a dent processing corresponding to the amount of thermal expansion of the meniscus portion at the time of manufacturing the slab is made on the surface side of the slab. 2. The continuous casting mold according to claim 1, wherein the meniscus portion is within a range of 50 mm or more and 150 mm or less downward from an upper end position of the cooling plate. 3. The continuous casting mold according to claim 1, wherein an attachment position of the attachment means located above the meniscus portion is within a range of 60 mm downward from an upper end position of the cooling plate. A mold for continuous casting, characterized in that there is. The continuous casting mold according to any one of claims 1 to 3, wherein a mounting interval of the mounting means positioned above and below the meniscus portion is 150 mm or more and 250 mm or less. .

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