JP2008105068A - Continuous casting mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous casting mold having a long life by suppressing and preventing a crack from being caused by thermal stress induced by a cyclic load. <P>SOLUTION: This continuous casting mold comprises a pair of short-piece members disposed opposite to each other with a space therebetween, a pair of long-piece members 10, 11 disposed opposite to each other in such a state that the short-piece member is held from both sides in the widthwise direction, and support members 13, 14 fixed to the backside thereof by fastening means 12, 12a. Cooling water is allowed to flow from a water supply part 15 in the lower part of the support members 13, 14 through a water passage part 16 on the backside of the short-piece members and the long-piece members 10, 11 into a water discharge part 17 on the upper part of the support members 13, 14. While cooling and solidifying a molten steel supplied into a region defined by the short-piece members and long-piece members 10, 11, the molten steel is drawn out downward to produce a cast strip. A thin flat plate is adopted in at least the upper side of the cooling member formed of one or both of the short-piece members and long-piece members 10, 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a continuous casting mold used for producing a slab.

Conventionally, molten steel is supplied to a continuous casting mold (hereinafter, also simply referred to as a mold) 80 shown in FIGS. 10 and 11A to 11D to cast a slab. The mold 80 is a state in which a pair of short piece members (also referred to as short side members) 81 and 82 composed of copper plates opposed to each other with a gap therebetween, and the short piece members 81 and 82 sandwiched from both sides in the width direction. And a pair of long piece members (also referred to as long side members) 83 and 84 formed of copper plates opposed to each other.
The short piece members 81 and 82 are mirror-symmetrical and have the same configuration, and a large number of water guide grooves 85 and 86 are provided in the vertical direction on the back surface side. The short piece members 81 and 82 are backed by bolts 87 on the back surface side. Plates (also called support members, cooling boxes, or water boxes) 88 and 89 are fixed. The long piece members 83 and 84 are also provided with a large number of water guide grooves 85 and 86 in the vertical direction on the back surface side, and the back plates 90 and 91 are fixed to the back surface side of the long piece members 83 and 84 by bolts 87. (For example, refer to Patent Document 1).

The mold 80 is configured to include short piece members 81 and 82, long piece members 83 and 84, and respective back plates 88 to 91, and a back plate 90 fixed to the long piece members 83 and 84 disposed to face each other. Bolts 92 are attached to both ends of 91 and fixed with nuts 93 via springs (not shown).
At the time of continuous casting work, as shown in FIG. 11 (B), from the water supply part 94 provided in the lower part of the back plates 88 to 91, a large number of short pieces 81 and 82 and long pieces 83 and 84 are provided. The cooling water is supplied to the drainage part 95 provided in the upper part of the back plates 88 to 91 through the water guide grooves 85 and 86. Thereby, while cooling the short piece members 81 and 82 and the long piece members 83 and 84, the molten steel is poured from above the mold 80 to perform the initial solidification of the molten steel, and the solidified slab is made at a substantially constant speed from below the mold. Drawing continuously to produce slabs.

JP 2003-136204 A

However, when continuous casting is performed with the above-described mold, for example, meniscus cracks (heat cracks generated near the meniscus level: hereinafter also referred to simply as cracks) have occurred in the short piece member and the long piece member. This meniscus crack is caused by, for example, the thermal effects on the mold due to repeated hot (during casting) and cold (after casting), and fluctuations in the mold surface level in the mold (the effects of bulging, nozzle discharge flow, or electromagnetic stirring). It is considered that the stress (plastic strain) amplitude caused by the temperature amplitude due to the above-mentioned fatigue failure (low cycle fatigue) caused by repeated load (thermal stress).
This meniscus crack is not only generated and propagated by mechanical fatigue fracture, but also, for example, a grain boundary crack generated by reaction with a low melting point metal (Zn attack, etc.) or an alloy layer formed by reaction (very brittle) Some of them start from the drop-off part.

Here, a description will be given of a fracture site in a case where a repeated load due to repeated hot and cold is dominant among stress amplitudes caused by temperature amplitudes causing meniscus cracks.
FIG. 12A shows the strain distribution during hot (during casting) of the copper plate constituting the long piece member currently used. The analysis conditions were as follows: bolt mounting interval for fixing the copper plate to the back plate: 120 mm, casting speed: 2.8 (m / min), meniscus level: 100 mm from the upper end of the copper plate, cooling water flow rate: 4000 per copper plate (Liter / minute), cooling water temperature: 40 (° C.), cooling water pressure: 4 (kg / cm ² ), copper plate material: high strength material (CCM-B), plating specification: Co—Ni, copper plate thermal conductivity : 305 (kcal / m ² / hr), Co—Ni plating thermal conductivity: 58 (kcal / m / hr / ° C.), copper plate fastening condition: bolt M20 (SUS), initial fastening force 1600 kg, copper plate fastening surface friction Coefficient: 0.15.

As is clear from FIG. 12A, the amount of strain generated in the portion fixed by the bolt is affected by the restraining force due to the bolt fastening between the portion fixed by the bolt and the portion between the adjacent bolts. It is getting bigger.
Also, the place where the plastic strain is maximum is not about 130 mm from the upper end of the copper plate where the copper plate temperature is maximum, but is about 170 mm below the upper end of the copper plate that becomes the bolt fastening position in the second stage of the copper plate (strong binding force) Part).
In addition, since the location where the plastic strain amplitude (= 1/2 plastic strain width) is maximum corresponds to the location where the plastic strain is maximum, the fatigue life of the above-described location is the shortest (large crack).
However, since many of the crack occurrence locations are shifted to a range close to the meniscus level above the above-described position, it is considered that other amplitude loads are dominant factors of this crack.

Next, a description will be given of a fracture site in a case where the repeated load due to the fluctuation of the molten metal surface level in the mold is dominant among the stress amplitude generated by the temperature amplitude causing the meniscus crack.
FIG. 12 (B) shows the strain distribution of the bolt part when it is assumed that the fluctuation of the molten metal surface level occurs in the range of 100 mm ± 20 mm (80 mm or more and 120 mm or less) downward from the upper end of the copper plate.
The value of the (plastic) strain width curve when the fluctuation of the molten metal surface shown in FIG. 12 (B) is ± 20 mm is the plastic strain width generated between the maximum level and the minimum level of the molten metal surface, and the plastic strain amplitude is also plastic. It occurs according to the strain width.
Further, the location where the maximum strain amplitude is generated due to the fluctuation of the molten metal surface level is around 110 mm below the upper end of the mold under the condition that the fluctuation of the molten metal surface level is in the range of 100 mm ± 20 mm. In the examination example this time, it corresponds almost to the 115 mm level position).

In addition, the examination result shown above uses the simulation by the FEM analysis (analysis using the finite element method) using a computer, and the fatigue (crack) life estimated from the plastic strain amplitude caused by the fluctuation of the molten metal surface level This is done by relative comparison. The fatigue life was determined by Manson's common gradient method (ε _pa = ε f ^0.6 · Nf ^−0.6 / 2).
From the above, the occurrence of meniscus cracks is greatly influenced by the plastic strain amplitude due to the fluctuation of the molten metal surface level, and the repeated load generated by repeated hot and cold is combined with this. It is presumed that they are overlapping.

The present invention has been made in view of the above circumstances, and provides a continuous casting mold capable of suppressing and further preventing the occurrence of cracks due to thermal stress caused by repeated loads and extending the service life. With the goal.

The continuous casting mold according to the present invention that meets the above-mentioned object is a pair of short piece members that are arranged to face each other with a gap therebetween, and a pair of long piece members that are arranged to face each other while sandwiching the short piece members from both sides in the width direction. And a supporting member fixed to the back side of the short piece member and the long piece member by fastening means, and from the water supply portion provided at the lower part of the supporting member, the short piece member and the long piece member Molten steel supplied to the region formed by the short piece member and the long piece member by flowing cooling water to the drainage portion provided at the upper part of the support member through the water passage portion provided on the back side. In a mold for producing a drawn slab downward while cooling and solidifying the short piece member and the long piece member,
At least the upper side of the cooling member composed of one or both of the short piece member and the long piece member was thinned and flattened.

In the continuous casting mold according to the present invention, it is preferable that the thinned flat portion of the cooling member is in a range of 50 mm or more and 600 mm or less from the upper end of the cooling member.
In the continuous casting mold according to the present invention, the thickness of the thinned cooling member is preferably 5 mm or more and 30 mm or less.
In the continuous casting mold according to the present invention, the water flow portion includes a cooling portion formed on a back surface side of the cooling member having a thin flat plate, and a plurality of water guide grooves communicating the cooling portion and the water supply portion. It is preferable to have.

In the continuous casting mold according to the present invention, it is preferable that the cooling portion is a gap formed by disposing a thin plate member in a space portion provided on the back surface side of the thin flat cooling member.
In the continuous casting mold according to the present invention, the cooling section has a flat cross-sectional area equal to the sum of the cross-sectional areas of the water guide grooves communicating with the cooling section or a sum of the cross-sectional areas of the water guide grooves of −50. It is preferable to be within the range of not less than% and not more than 50%.
In the casting mold for continuous casting according to the present invention, the connection portion of the water guide groove communicating with the cooling portion is gradually widened toward the cooling portion with the inner width thereof being larger than the inner width of other portions of the water guide groove. It is preferable.

In the continuous casting mold according to the present invention, it is preferable that the attachment position of the fastening means is a portion excluding a range from the meniscus position of the cooling member to 50 mm below the meniscus position.
In the continuous casting mold according to the present invention, it is preferable that the fastening means located in the vicinity of the meniscus position of the cooling member is provided with a buffer member for adjusting the fastening force of the cooling member with respect to the support member.

In the continuous casting mold according to claims 1 to 9, since at least the upper side of the cooling member is flattened, the upper structure of the cooling member is not provided with the water guide groove (slit) provided in the conventional mold. A thin plate structure can be formed. As a result, the restraining strain of the cooling member itself can be relaxed and the cooling efficiency can be increased as compared with the conventional water guide groove structure, so that the generation of cracks in the cooling member is suppressed (the generated strain is reduced). ) And the life of the mold can be extended.
In the case of the conventional water guide groove structure, the structure itself acts as a rib for preventing deformation of the cooling member, and thus restricts free deformation of the cooling member. For this reason, in the vicinity of the molten metal surface where the heat load is large, the restraint strain of the cooling member increases and the stress state deteriorates, that is, the occurrence of plastic strain increases.
In particular, since the continuous casting mold according to claim 2 defines the position where the cooling member is flattened, the thermal stress can be reliably reduced, and the occurrence frequency of cracks can be further reduced.
Since the continuous casting mold according to claim 3 defines the thickness of the thinned and flattened cooling member, the effect of reducing the thermal stress of the thinned and flattened portion can be further enhanced.

In the continuous casting mold according to claim 4, since the water passing portion is formed by the cooling portion formed on the entire back surface side of the cooling member and the water guide groove communicating therewith, the stress can be relieved with a simple structure. In addition, the cooling efficiency can be improved, the thermal stress can be greatly relieved, and the amount of plastic strain generated can be reduced.
In the continuous casting mold according to the fifth aspect, since the gap serving as the cooling part is formed by a thin plate member disposed in the space part, the structure of the cooling part can be simplified, and the workability at the time of manufacture is also good.
The casting mold for continuous casting according to claim 6 defines the relationship between the flat cross-sectional area of the cooling part and the sum of the flat cross-sectional areas of the water guide grooves, so that the cooling in the water flow part is performed from the lower part to the upper part of the cooling member. The water flow can be stabilized.

The casting mold for continuous casting according to claim 7 can stabilize the flow of the cooling water from the water guiding groove to the cooling part without stagnation by defining the shape of the connecting part of the water guiding groove communicating with the cooling part.
The continuous casting mold according to claim 8 stipulates the attachment position of the fastening means, so that the restraining force by the fastening means at a portion where thermal stress is likely to be generated can be reduced, and the generated thermal stress can be further relaxed. Can do.
In the continuous casting mold according to the ninth aspect, since the buffer member is provided in the fastening means located in the vicinity of the meniscus position where thermal stress is likely to occur, the restraining force by the fastening means can be further reduced.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
As shown in FIGS. 1 to 6, a continuous casting mold (hereinafter also simply referred to as a mold) according to an embodiment of the present invention has a pair of short pieces (not shown) that are arranged to face each other at intervals. Side members), a pair of long piece members (also referred to as long side members) 10 and 11, which are opposed to each other while sandwiching the short piece members from both sides in the width direction, and the back surfaces of the short piece members and the long piece members 10 and 11 It has back plates (also referred to as cooling boxes or water boxes) 13 and 14 which are examples of support members fixed to the side by fastening means 12 and 12a, respectively. Thereby, from the water supply part 15 provided in the lower part of the back plates 13 and 14, the upper part of the back plates 13 and 14 through the water passing part 16 provided in the back surface side of the short piece member and the long piece members 10 and 11 While flowing cooling water to the drainage part 17 provided in the molten steel, the molten steel supplied in the region formed by the short piece members and the long piece members 10 and 11 is cooled and solidified by the short piece members and the long piece members 10 and 11. A downwardly drawn slab (an example of a cast piece) can be manufactured. In addition, since the short piece member and the long piece members 10 and 11 differ only in the width | variety and the other structure is substantially the same, and the long piece members 10 and 11 are mirror-symmetrical, below, FIGS. The long piece member 10 to be shown is a cooling member, and its configuration will be mainly described in detail.

Each short piece member is made of copper or a copper alloy, and has a thickness of about 10 mm to 100 mm, a width of about 50 mm to 300 mm, and a vertical length of about 600 mm to 1200 mm. Each of the long piece members 10 and 11 is made of copper or a copper alloy. For example, the thickness is about 10 mm or more and 100 mm or less, and the width (the width in contact with the cast piece) is about 600 mm or more and 3000 mm or less, and the length in the vertical direction. Is about the same as the short piece member.
Accordingly, the distance between the pair of short piece members arranged to face each other is about 600 mm to 3000 mm, the distance between the pair of long piece members 10 and 11 is about 50 mm to 300 mm, and the length of the mold in the vertical direction. Is about 600 mm or more and 1200 mm or less. In addition, the space | interval of the short piece member arrange | positioned facing can be changed within the above-mentioned range.
Thereby, for example, a slab having a width of about 600 mm to about 3000 mm and a thickness of about 50 mm to about 300 mm can be manufactured.

As shown in FIGS. 1A to 1C, FIG. 2, and FIGS. 3A to 3C, the water flow portion 16 provided on the back surface side of the long piece member 10 is at least of the long piece member 10. On the upper side, a cooling unit 18 and a plurality of water guiding grooves 19 and 20 that communicate with the cooling unit 18 and the water supply unit 15 are provided. The upper side of the long piece member 10 is a range of 50 mm to 600 mm from the upper end of the long piece member 10 (preferably, the upper limit is 500 mm, further 400 mm, the lower limit is 80 mm, and further 100 mm). This is because heat cracks that have conventionally occurred in the range of 80 mm or more and 150 mm or less from the upper end of the long piece member 10 are suppressed and further prevented.
The cooling portion 18 is a gap G formed by disposing the thin plate members 22, 22 a, and 22 b in the space portion 21 provided on the entire upper surface of the long piece member 10. The thin plate members 22, 22 a, 22 b have different shapes at both ends or one end in the width direction depending on the fastening means 12, 12 a. Moreover, the space part 21 is formed over the width direction of the long piece member 10, and the side cross-sectional shape is a ship shape.

The space portion 21 is formed so that the thickness T1 of the long piece member 10 is 5 mm or more and 30 mm or less. As a result, the long piece member 10 in this portion can be flattened.
Here, when the thickness of the long piece member of the thinned flat portion is less than 5 mm, the grinding allowance at the time of repeated use of the long piece member is reduced and the number of times the mold is used is reduced. On the other hand, when the thickness exceeds 30 mm, the thickness becomes too thick, and the amount of plastic strain increases due to an increase in generated temperature due to an increase in mold temperature and fastening constraints.
From the above, the thickness T1 of the thin flat member is 5 mm or more and 30 mm or less, but the upper limit is preferably 20 mm, more preferably 15 mm, and the lower limit is preferably 8 mm, more preferably 10 mm. .
A plurality (two in this case) of fixing parts 24 of screws 23 for attaching the upper part of the thin plate member 22 are provided at an upper position in the space part 21.

As shown in FIGS. 4 (A) and 4 (B), the large number of water guide grooves 19 and 20 communicating with the cooling unit 18 are thin in thickness T2 and T3 from the bottom position to the molten steel cooling surface of the long piece member 10. For example, it is formed so as to be thicker by about 5 mm or more and 20 mm or less than the thickness T1 of the flattened long piece member 10. In addition, the structure of the water guide groove 19 and the water guide groove 20 is the same except that the depth differs (the water guide groove 20 is deeper than the water guide groove 19). The water guide grooves 19 and 20 are linear along the longitudinal direction of the long piece member 10, and are formed at a predetermined pitch (for example, about 6 mm or more and 30 mm or less) in the width direction of the long piece member 10.
Therefore, between the adjacent water guide grooves 19 and 19 and the water guide grooves 19 and 20 becomes a fixing portion 26 of the screw 25 for attaching the lower part of the thin plate members 22, 22 a and 22 b.
Thereby, after arranging the thin plate members 22, 22 a, 22 b in the space portion 21, the upper and lower portions can be fixed to the long piece member 10 by the screws 23, 25. When fixed in this manner, the back surfaces of the thin plate members 22, 22 a, 22 b are arranged on the same plane as the back surface of the portion where the upper end portion of the long piece member 10 and the water guide grooves 19, 20 are formed. It has become.

The thin plate members 22, 22 a, 22 b are made of, for example, copper, copper alloy, aluminum, aluminum alloy, iron, or stainless steel having corrosion resistance, and a plurality (in the present embodiment, 15 in the width direction). ). Each of the thin plate members 22, 22 a, and 22 b has a ship-like cross-sectional shape, and is attached to the thin plate members 22, 22 a, 22 b and includes a plurality of set screws 27 that protrude a predetermined length toward the back side of the long piece member 10. The tip is in contact with the back surface 28 of the long flat member 10 which is thin and flat, and a certain gap G can be formed.
The gap G is, for example, about 2 mm to 7 mm, and cooling water flows through this portion.
5A to 5D show the portion of the water flow portion 16 through which the cooling water flows, but the connection portion 29 of the water guide grooves 19 and 20 communicating with the cooling portion 18 is the cooling portion 18. The inner width is gradually widened more continuously (curved surface) than the inner width (for example, about 1 mm or more and about 5 mm or less) of other portions of the water guide grooves 19 and 20. Moreover, the connection part 29 is gradually made shallower than the depth of the other part of the water guide grooves 19 and 20 toward the cooling part 18.

The flat cross-sectional area of the cooling unit 18 described above is the same as the total of the cross-sectional areas of the water guide grooves 19 and 20 communicating with the cooling unit 18, or −50% or more + 50% of the total of the cross-sectional areas of the water guide grooves 19 and 20. It is within the following range (preferably, the upper limit is + 40% and the lower limit is −30%).
Thereby, although the flow rate of the cooling water flowing through the water flow part 16 can be made substantially uniform from the lower part to the upper part of the long piece member 10, the water guide grooves 19, 20 communicating the plane cross-sectional area of the cooling part 18 with the cooling part 18. It is possible to increase the cooling efficiency in the cooling section 18 by making it smaller than the total of the cross sectional areas of the above.
Further, the plane cross-sectional area of the connecting portion 29 may be set within the range of the cross-sectional area of the water guide grooves 19 and 20 defined as described above.
Note that linear water guide grooves 30 and 31 through which cooling water flows are formed at both ends in the width direction of the long piece member 10, but since this does not communicate with the cooling unit 18, this plane cross-sectional area is as described above. It is not included in the cross-sectional area of the water guide grooves 19 and 20.

On the back side of the long piece member 10 shown above (the side opposite to the cooling surface), a plurality of fastening means 12, 12a are used, for example, a stainless steel back plate 13 (for example, a thickness of 50 mm or more and 500 mm or more). The following is attached). At the time of this attachment, the water supply portion 15, the drainage portion 17 of the back plate 13, and the water passage portions of the long piece member 10 (straight water guides disposed on both sides in the width direction of the long piece member 10) Grooves (not shown) are formed so as to surround 16 (including grooves 30 and 31), and by arranging an O-ring (not shown) here, the adhesion between the long piece member 10 and the back plate 13 is improved, The leakage of the cooling water from the water flow part 16 is prevented.
As shown in FIG. 6, the fastening means 12, 12 a has a female screw portion 32 formed on the long piece member 10 and a male screw 33 that is screwed into the female screw portion 32 and fastens the back plate 13. . Further, in order to attach the male screw 33, a seal washer 35 that can be waterproofed is disposed in advance in the hole 34 formed in the back plate 13, thereby preventing leakage of cooling water from the portion to which the male screw 33 is attached. .

The male screw 33 is attached to the back plate 13 via one or a plurality of springs (an example of a buffer member) 36. The fastening force of the long piece member 10 with respect to the back plate 13 is adjusted, and its movement Is given a degree of freedom.
A plurality of fastening means 12 and 12a are provided at equal pitches in the longitudinal direction of the long piece member 10 (here, 8 locations), but the length of the long piece member 10 from the meniscus position to the lower part of the meniscus position is 50 mm. It is preferred to exclude the range. At this time, the male screw 33 in the range from the meniscus position to 50 mm below the meniscus position may be simply removed. However, the female screw portion is not formed in the long piece member, and the hole is not formed in the back plate. Is preferred. In addition, only the fastening means located near the meniscus position (for example, a range from the meniscus position to 50 mm below the meniscus position) is provided with a spring, and other parts are provided with no spring. You can also
Thereby, the restraining force of the long piece member by the back plate can be further weakened.

Moreover, you may form a coating layer in the surface (molten steel surface) of a long piece member.
For example, a Co alloy such as Co—Ni, a Ni alloy such as Ni—Fe, or Ni plating can be used for the coating layer, but thermal spraying (eg, Ni-based Cr—Si—B alloy) is also used. it can. This coating layer may be formed of the same type of component over the entire surface of the copper plate used for the long piece member, and plural types of components may be formed in different regions in the vertical direction of the copper plate. You may form each according to a function.
Each of the long piece members shown above is manufactured by forming a coating layer on the surface of the copper plate and then performing a conventionally known machining process on a predetermined shape.
As for the shape of the long piece member, the distance between the pair of long piece members may be the same in the drawing direction of the slab, but it is preferable that the long piece member be narrowed according to the solidification shrinkage shape of the slab.

Next, in order to confirm the operation and effect of the present invention, the structure of the cooling member (long piece member) shown in the conventional examples, comparative examples 1 and 2 and examples 1 and 2 is used to perform FEM analysis (finite element method). The results of the analysis using In addition, the cooling member of the conventional example has a water guide groove formed on the entire back surface side of the copper plate and is thick (19 mm) from the bottom of the water guide groove to the molten steel cooling surface. The thickness from the bottom of the water guide groove to the molten steel cooling surface is smaller than the example (15 mm), and the cooling member of Comparative Example 2 is thinner than the comparative example 1 from the bottom of the water guide groove to the molten steel cooling surface (13 mm). On the other hand, the cooling member of Example 1 is formed with a water passage portion having a cooling portion and a water guide groove on the back surface side of the copper plate, and with or without a bolt (male screw) in the second vertical stage of the copper plate. In addition, the cooling member of Example 2 does not use the second-stage bolt (male screw) in the longitudinal direction of the copper plate of Example 1, and further removes this bolt hole (female screw part). These test conditions and test results are shown in Tables 1 and 2. The copper plate material B is a high strength material of Cr-Zr-copper alloy, and the material A is a cold forging treatment applied to the high strength material of material B Cr-Zr-copper alloy. Further, the strength is increased.

Table 3 shows the material characteristics of the copper plate material, and Table 4 shows the results of collecting only the test results of the conventional examples, Comparative Examples 1 and 2, and Examples 1 and 2.

Hereinafter, a description will be given with reference to FIGS. In addition, the temperature distribution of FIG. 7 (A), the displacement distribution of FIG. 7 (B), the plastic strain distribution of FIG. 8 (A), and the plastic strain width of FIG. 9 (A) are plating of the plated copper plate. It is an analysis result on the surface, and the plastic strain distribution in FIG. 8B and the plastic strain width in FIG. 9B are the analysis results at the interface between the plating and the copper plate.

As is apparent from FIGS. 7 to 9 and Table 4, in the conventional example, the thickness of the upper portion of the copper plate is high because the thickness of the copper plate is too thick, and the binding force is also increased. For this reason, the generated plastic strain is large and the fatigue life is short.
Further, as in Comparative Example 1, by reducing the thickness of the copper plate of the meniscus portion, the restraining force was slightly improved and the fatigue life increased to about 1.2 times that of the conventional example, but it was not sufficient. .
Further, as in Comparative Example 2, the thickness of the copper plate at the meniscus portion is further reduced, so that the temperature of the upper portion of the copper plate is improved as compared with the case of Comparative Example 1, and fatigue is reduced due to relaxation of the binding force due to the reduction in thickness. The lifetime has increased to about 1.5 times that of the conventional example. However, remarkable results could not be obtained compared to the conventional case.

On the other hand, in Example 1, the restraining force was sufficiently relaxed by improving the structure of the upper part of the copper plate including the meniscus portion. Moreover, the copper plate temperature was also improved, and the fatigue life of the plating surface was improved to about 2.3 times. In addition, when the second-stage bolt was removed, it was further improved to about 3.4 times.
Moreover, the fatigue life of the base metal surface was improved to about 4.2 times by using a copper plate base material as a high strength material.
Furthermore, in Example 2, in addition to the structural improvement, by removing the second fastening bolt in the longitudinal direction, the restraining force was further improved, and the fatigue life of the plating surface was improved to about 4 times.
Further, the fatigue life of the base metal surface was improved to about 7.7 times by making the copper plate base material a high strength material.
From the above, it has been confirmed that by applying the present invention, the generation of cracks due to thermal stress caused by repeated loads can be suppressed and further prevented, and the life can be extended.

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 long piece member was demonstrated as a cooling member, it is good also considering only a short piece member or both a long piece member and a short piece member as a cooling member.
In the above-described embodiment, the configuration of a mold for manufacturing a slab, which is an example of a slab, has been described. However, a mold for manufacturing another slab having a different shape and size, for example, a billet, a bloom, or a beam blank. Of course, it is possible to apply the present invention.

(A) is a front view of a long piece member of a continuous casting mold according to an embodiment of the present invention, (B) is a cross-sectional view taken along the line aa of (A), and (C) is b of (A). It is -b arrow sectional drawing. It is a partial enlarged front view of the same long piece member. (A)-(C) are cc arrow sectional drawing, dd arrow sectional drawing, and ee arrow sectional drawing of FIG. 1 (A), respectively. (A) is ff arrow directional cross-sectional view of FIG. 2, (B) is gg arrow directional cross-sectional view of FIG. (A)-(D) is the perspective view which looked at the water flow part of the same long piece member from the surface side of the long piece member, respectively, The top view of the connection part of the water guide groove connected to the cooling part of the same long piece member, It is the perspective view which looked at the connection part of the groove | channel from the surface side of the long piece member, and the perspective view seen from the back surface side of the long piece member. It is explanatory drawing of the fastening means in the site | part close | similar to the meniscus position where a big thermal stress tends to generate | occur | produce. (A) is a graph which shows the temperature distribution on the surface of a long piece member, (B) is a graph which shows the displacement distribution on the surface of a long piece member. (A) is a graph which shows the plastic strain distribution in the plating surface of a long piece member, (B) is a graph which shows the plastic strain distribution in the base material surface of a long piece member. (A) is a graph which shows the plastic strain width in the plating surface at the time of the molten metal surface fluctuation | variation of a long piece member, (B) is a graph which shows the plastic strain width in the base material surface at the time of the molten metal surface fluctuation | variation of a long piece member. It is a top view of the casting mold for continuous casting which concerns on a prior art example. (A) is a partial enlarged front view of a short piece member and a long piece member of the casting mold for continuous casting, (B) is a cross-sectional view taken along line l-l in (A), and (C) is a m-m arrow in (A). (D) is a cross-sectional view taken along line nn of (A). (A) is a graph of the strain distribution when the long piece member of the continuous casting mold is hot, and (B) is a graph of the strain distribution when the molten metal level of the long piece member of the continuous casting mold is changed.

Explanation of symbols

10, 11: Long piece member, 12, 12a: Fastening means, 13, 14: Back plate (support member), 15: Water supply part, 16: Water flow part, 17: Drain part, 18: Cooling part, 19, 20 : Water guide groove, 21: space part, 22, 22a, 22b: thin plate member, 23: screw, 24: fixing part, 25: screw, 26: fixing part, 27: set screw, 28: back surface, 29: connection part, 30, 31: linear water guide groove, 32: female screw part, 33: male screw, 34: hole, 35: seal washer, 36: spring (buffer member)

The present invention relates to a continuous casting mold used for producing a slab.

Conventionally, molten steel is supplied to a continuous casting mold (hereinafter, also simply referred to as a mold) 80 shown in FIGS. 10 and 11A to 11D to cast a slab. The mold 80 is a state in which a pair of short piece members (also referred to as short side members) 81 and 82 composed of copper plates opposed to each other with a gap therebetween, and the short piece members 81 and 82 sandwiched from both sides in the width direction. And a pair of long piece members (also referred to as long side members) 83 and 84 formed of copper plates opposed to each other.
The short piece members 81 and 82 are mirror-symmetrical and have the same configuration, and a large number of water guide grooves 85 and 86 are provided in the vertical direction on the back surface side. The short piece members 81 and 82 are backed by bolts 87 on the back surface side. Plates (also called support members, cooling boxes, or water boxes) 88 and 89 are fixed. The long piece members 83 and 84 are also provided with a large number of water guide grooves 85 and 86 in the vertical direction on the back surface side, and the back plates 90 and 91 are fixed to the back surface side of the long piece members 83 and 84 by bolts 87. (For example, refer to Patent Document 1).

The mold 80 is configured to include short piece members 81 and 82, long piece members 83 and 84, and respective back plates 88 to 91, and a back plate 90 fixed to the long piece members 83 and 84 disposed to face each other. Bolts 92 are attached to both ends of 91 and fixed with nuts 93 via springs (not shown).
At the time of continuous casting work, as shown in FIG. 11 (B), from the water supply part 94 provided in the lower part of the back plates 88 to 91, a large number of short pieces 81 and 82 and long pieces 83 and 84 are provided. The cooling water is supplied to the drainage part 95 provided in the upper part of the back plates 88 to 91 through the water guide grooves 85 and 86. Thereby, while cooling the short piece members 81 and 82 and the long piece members 83 and 84, the molten steel is poured from above the mold 80 to perform the initial solidification of the molten steel, and the solidified slab is made at a substantially constant speed from below the mold. Drawing continuously to produce slabs.

JP 2003-136204 A

However, when continuous casting is performed with the above-described mold, for example, meniscus cracks (heat cracks generated near the meniscus level: hereinafter also referred to simply as cracks) have occurred in the short piece member and the long piece member. This meniscus crack is caused by, for example, the thermal effects on the mold due to repeated hot (during casting) and cold (after casting), and fluctuations in the mold surface level in the mold (the effects of bulging, nozzle discharge flow, or electromagnetic stirring). It is considered that the stress (plastic strain) amplitude caused by the temperature amplitude due to the above-mentioned fatigue failure (low cycle fatigue) caused by repeated load (thermal stress).
This meniscus crack is not only generated and propagated by mechanical fatigue fracture, but also, for example, a grain boundary crack generated by reaction with a low melting point metal (Zn attack etc.) or an alloy layer formed by reaction (very brittle) Some of them start from the drop-off part.

Here, a description will be given of a fracture site in a case where a repeated load due to repeated hot and cold is dominant among stress amplitudes caused by temperature amplitudes causing meniscus cracks.
FIG. 12A shows the strain distribution during hot (during casting) of the copper plate constituting the long piece member currently used. The analysis conditions were as follows: bolt mounting interval for fixing the copper plate to the back plate: 120 mm, casting speed: 2.8 (m / min), meniscus level: 100 mm from the upper end of the copper plate, cooling water flow rate: 4000 per copper plate (Liter / minute), cooling water temperature: 40 (° C.), cooling water pressure: 4 (kg / cm ² ), copper plate material: high strength material (CCM-B), plating specification: Co—Ni, copper plate thermal conductivity : 305 (kcal / m ² / hr), Co—Ni plating thermal conductivity: 58 (kcal / m / hr / ° C.), copper plate fastening condition: bolt M20 (SUS), initial fastening force 1600 kg, copper plate fastening surface friction Coefficient: 0.15.

As is clear from FIG. 12A, the amount of strain generated in the portion fixed by the bolt is affected by the restraining force due to the bolt fastening between the portion fixed by the bolt and the portion between the adjacent bolts. It is getting bigger.
Also, the place where the plastic strain is maximum is not about 130 mm from the upper end of the copper plate where the copper plate temperature is maximum, but is about 170 mm below the upper end of the copper plate that becomes the bolt fastening position in the second stage of the copper plate (strong binding force) Part).
In addition, since the location where the plastic strain amplitude (= 1/2 plastic strain width) is maximum corresponds to the location where the plastic strain is maximum, the fatigue life of the above-described location is the shortest (large crack).
However, since many of the crack occurrence locations are shifted to a range close to the meniscus level above the above-described position, it is considered that other amplitude loads are dominant factors of this crack.

Next, a description will be given of a fracture site in a case where the repeated load due to the fluctuation of the molten metal surface level in the mold is dominant among the stress amplitude generated by the temperature amplitude causing the meniscus crack.
FIG. 12 (B) shows the strain distribution of the bolt part when it is assumed that the fluctuation of the molten metal surface level occurs in the range of 100 mm ± 20 mm (80 mm or more and 120 mm or less) downward from the upper end of the copper plate.
The value of the (plastic) strain width curve when the fluctuation of the molten metal surface shown in FIG. 12 (B) is ± 20 mm is the plastic strain width generated between the maximum level and the minimum level of the molten metal surface, and the plastic strain amplitude is also plastic. It occurs according to the strain width.
Further, the location where the maximum strain amplitude is generated due to the fluctuation of the molten metal surface level is around 110 mm below the upper end of the mold under the condition that the fluctuation of the molten metal surface level is in the range of 100 mm ± 20 mm. In the examination example this time, it corresponds almost to the 115 mm level position).

In addition, the examination result shown above uses the simulation by the FEM analysis (analysis using the finite element method) using a computer, and the fatigue (crack) life estimated from the plastic strain amplitude caused by the fluctuation of the molten metal surface level This is done by relative comparison. The fatigue life was determined by Manson's common gradient method (ε _pa = ε f ^0.6 · Nf ^−0.6 / 2).
From the above, the occurrence of meniscus cracks is greatly influenced by the plastic strain amplitude due to the fluctuation of the molten metal surface level, and the repeated load generated by repeated hot and cold is combined with this. It is presumed that they are overlapping.

The present invention has been made in view of the above circumstances, and provides a continuous casting mold capable of suppressing and further preventing the occurrence of cracks due to thermal stress caused by repeated loads and extending the service life. With the goal.

The continuous casting mold according to the present invention that meets the above-mentioned object is a pair of short piece members that are arranged to face each other with a gap therebetween, and a pair of long piece members that are arranged to face each other while sandwiching the short piece members from both sides in the width direction. And a supporting member fixed to the back side of the short piece member and the long piece member by fastening means, and from the water supply portion provided at the lower part of the supporting member, the short piece member and the long piece member Molten steel supplied to the region formed by the short piece member and the long piece member by flowing cooling water to the drainage portion provided at the upper part of the support member through the water passage portion provided on the back side. In a mold for producing a drawn slab downward while cooling and solidifying the short piece member and the long piece member,
A cooling part in which at least the upper side of the cooling member consisting of one or both of the short piece member and the long piece member is flattened, and the water flow part is formed on the entire back surface of the thinned cooling member. And a large number of water guide grooves communicating with the cooling part and the water supply part, and the cooling part is provided on the back surface of the cooling member in a space provided on the back surface side of the thinned flat cooling member. And a portion formed by arranging the surfaces of the thin plate members in parallel, and the attachment position of the fastening means is a portion excluding a range from the meniscus position of the cooling member to the lower side of the meniscus position up to 50 mm. I did .

In the continuous casting mold according to the present invention, it is preferable that the thinned flat portion of the cooling member is in a range of 50 mm or more and 600 mm or less from the upper end of the cooling member.
In the continuous casting mold according to the present invention, the thickness of the thinned cooling member is preferably 5 mm or more and 30 mm or less.

In the continuous casting mold according to the present invention, the cooling section has a flat cross-sectional area equal to the sum of the cross-sectional areas of the water guide grooves communicating with the cooling section or a sum of the cross-sectional areas of the water guide grooves of −50. It is preferable to be within the range of not less than% and not more than 50%.
In the casting mold for continuous casting according to the present invention, the connection portion of the water guide groove communicating with the cooling portion is gradually widened toward the cooling portion with the inner width thereof being larger than the inner width of other portions of the water guide groove. It is preferable.

In the continuous casting mold according to any one of claims 1 to 6 , since at least the upper side of the cooling member is flattened, the upper structure of the cooling member is not provided with the water guide groove (slit) provided in the conventional mold. A thin plate structure can be formed. As a result, the restraining strain of the cooling member itself can be relaxed and the cooling efficiency can be increased as compared with the conventional water guide groove structure, so that the generation of cracks in the cooling member is suppressed (the generated strain is reduced). ) And the life of the mold can be extended.
In the case of the conventional water guide groove structure, the structure itself acts as a rib for preventing deformation of the cooling member, and thus restricts free deformation of the cooling member. For this reason, in the vicinity of the molten metal surface where the heat load is large, the restraint strain of the cooling member increases and the stress state deteriorates, that is, the occurrence of plastic strain increases.
In particular, since the continuous casting mold according to claim 2 defines the position where the cooling member is flattened, the thermal stress can be reliably reduced, and the occurrence frequency of cracks can be further reduced.
Since the continuous casting mold according to claim 3 defines the thickness of the thinned and flattened cooling member, the effect of reducing the thermal stress of the thinned and flattened portion can be further enhanced.

In the casting mold for continuous casting according to claim 1 , since the water passing portion is formed by the cooling portion formed on the entire back surface side of the cooling member and the water guide groove communicating with the cooling portion, the stress can be relieved with a simple structure. In addition, the cooling efficiency can be improved, the thermal stress can be greatly relieved, and the amount of plastic strain generated can be reduced.
Continuous casting mold according to claim 1 is a gap as a cooling part, because it forms a thin plate member disposed in the space portion, easy configuration of the cooling unit, it is also good workability at the time of manufacture.
The continuous casting mold according to claim 4 defines the relationship between the flat cross-sectional area of the cooling part and the sum of the flat cross-sectional areas of the water guide grooves, so that the cooling in the water flow part is performed from the lower part to the upper part of the cooling member. The water flow can be stabilized.

In the continuous casting mold according to the sixth aspect, the flow of the cooling water from the water guiding groove to the cooling part can be stabilized without any stagnation by defining the shape of the connecting part of the water guiding groove communicating with the cooling part.
Since the continuous casting mold according to claim 1 defines the mounting position of the fastening means, it is possible to reduce the restraining force by the fastening means at a portion where thermal stress is likely to occur, and to further reduce the generated thermal stress. Can do.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
As shown in FIGS. 1 to 6, a continuous casting mold (hereinafter also simply referred to as a mold) according to an embodiment of the present invention has a pair of short pieces (not shown) that are arranged to face each other at intervals. Side members), a pair of long piece members (also referred to as long side members) 10 and 11, which are opposed to each other while sandwiching the short piece members from both sides in the width direction, and the back surfaces of the short piece members and the long piece members 10 and 11 It has back plates (also referred to as cooling boxes or water boxes) 13 and 14 which are examples of support members fixed to the side by fastening means 12 and 12a, respectively. Thereby, from the water supply part 15 provided in the lower part of the back plates 13 and 14, the upper part of the back plates 13 and 14 through the water passing part 16 provided in the back surface side of the short piece member and the long piece members 10 and 11 While flowing cooling water to the drainage part 17 provided in the molten steel, the molten steel supplied in the region formed by the short piece members and the long piece members 10 and 11 is cooled and solidified by the short piece members and the long piece members 10 and 11. A downwardly drawn slab (an example of a cast piece) can be manufactured. In addition, since the short piece member and the long piece members 10 and 11 differ only in the width | variety and the other structure is substantially the same, and the long piece members 10 and 11 are mirror-symmetrical, below, FIGS. The long piece member 10 to be shown is a cooling member, and its configuration will be mainly described in detail.

Each short piece member is made of copper or a copper alloy, and has a thickness of about 10 mm to 100 mm, a width of about 50 mm to 300 mm, and a vertical length of about 600 mm to 1200 mm. Each of the long piece members 10 and 11 is made of copper or a copper alloy. For example, the thickness is about 10 mm or more and 100 mm or less, and the width (the width in contact with the cast piece) is about 600 mm or more and 3000 mm or less, and the length in the vertical direction. Is about the same as the short piece member.
Accordingly, the distance between the pair of short piece members arranged to face each other is about 600 mm to 3000 mm, the distance between the pair of long piece members 10 and 11 is about 50 mm to 300 mm, and the length of the mold in the vertical direction. Is about 600 mm or more and 1200 mm or less. In addition, the space | interval of the short piece member arrange | positioned facing can be changed within the above-mentioned range.
Thereby, for example, a slab having a width of about 600 mm to about 3000 mm and a thickness of about 50 mm to about 300 mm can be manufactured.

As shown in FIGS. 1A to 1C, FIG. 2, and FIGS. 3A to 3C, the water flow portion 16 provided on the back surface side of the long piece member 10 is at least of the long piece member 10. On the upper side, a cooling unit 18 and a plurality of water guide grooves 19 and 20 that communicate the cooling unit 18 and the water supply unit 15 are provided. The upper side of the long piece member 10 is a range of 50 mm to 600 mm from the upper end of the long piece member 10 (preferably, the upper limit is 500 mm, further 400 mm, the lower limit is 80 mm, and further 100 mm). This is because heat cracks that have conventionally occurred in the range of 80 mm or more and 150 mm or less from the upper end of the long piece member 10 are suppressed and further prevented.
The cooling portion 18 is a gap G formed by disposing the thin plate members 22, 22 a, and 22 b in the space portion 21 provided on the entire upper surface of the long piece member 10. The thin plate members 22, 22 a, 22 b have different shapes at both ends or one end in the width direction depending on the fastening means 12, 12 a. Moreover, the space part 21 is formed over the width direction of the long piece member 10, and the side cross-sectional shape is a ship shape.

The space portion 21 is formed so that the thickness T1 of the long piece member 10 is 5 mm or more and 30 mm or less. As a result, the long piece member 10 in this portion can be flattened.
Here, when the thickness of the long piece member of the thinned flat portion is less than 5 mm, the grinding allowance at the time of repeated use of the long piece member is reduced and the number of times the mold is used is reduced. On the other hand, when the thickness exceeds 30 mm, the thickness becomes too thick, and the amount of plastic strain increases due to an increase in generated temperature due to an increase in mold temperature and fastening constraints.
From the above, the thickness T1 of the thin flat member is 5 mm or more and 30 mm or less, but the upper limit is preferably 20 mm, more preferably 15 mm, and the lower limit is preferably 8 mm, more preferably 10 mm. .
A plurality (two in this case) of fixing parts 24 of screws 23 for attaching the upper part of the thin plate member 22 are provided at an upper position in the space part 21.

As shown in FIGS. 4 (A) and 4 (B), the large number of water guide grooves 19 and 20 communicating with the cooling unit 18 are thin in thickness T2 and T3 from the bottom position to the molten steel cooling surface of the long piece member 10. For example, it is formed so as to be thicker by about 5 mm or more and 20 mm or less than the thickness T1 of the flattened long piece member 10. In addition, the structure of the water guide groove 19 and the water guide groove 20 is the same except that the depth differs (the water guide groove 20 is deeper than the water guide groove 19). The water guide grooves 19 and 20 are linear along the longitudinal direction of the long piece member 10, and are formed at a predetermined pitch (for example, about 6 mm or more and 30 mm or less) in the width direction of the long piece member 10.
Therefore, between the adjacent water guide grooves 19 and 19 and the water guide grooves 19 and 20 becomes a fixing portion 26 of the screw 25 for attaching the lower part of the thin plate members 22, 22 a and 22 b.
Thereby, after arranging the thin plate members 22, 22 a, 22 b in the space portion 21, the upper and lower portions can be fixed to the long piece member 10 by the screws 23, 25. When fixed in this manner, the back surfaces of the thin plate members 22, 22 a, 22 b are arranged on the same plane as the back surface of the portion where the upper end portion of the long piece member 10 and the water guide grooves 19, 20 are formed. It has become.

The thin plate members 22, 22 a, 22 b are made of, for example, copper, copper alloy, aluminum, aluminum alloy, iron, or stainless steel having corrosion resistance, and a plurality (in the present embodiment, 15 in the width direction). ). Each of the thin plate members 22, 22 a, and 22 b has a ship-like cross-sectional shape, and is attached to the thin plate members 22, 22 a, 22 b and includes a plurality of set screws 27 that protrude a predetermined length toward the back side of the long piece member 10. The tip is in contact with the back surface 28 of the long flat member 10 which is thin and flat, and a certain gap G can be formed.
The gap G is, for example, about 2 mm to 7 mm, and cooling water flows through this portion.
5A to 5D show the portion of the water flow portion 16 through which the cooling water flows, but the connection portion 29 of the water guide grooves 19 and 20 communicating with the cooling portion 18 is the cooling portion 18. The inner width is gradually widened more continuously (curved surface) than the inner width (for example, about 1 mm or more and about 5 mm or less) of other portions of the water guide grooves 19 and 20. Moreover, the connection part 29 is gradually made shallower than the depth of the other part of the water guide grooves 19 and 20 toward the cooling part 18.

The flat cross-sectional area of the cooling unit 18 described above is the same as the total of the cross-sectional areas of the water guide grooves 19 and 20 communicating with the cooling unit 18, or −50% or more + 50% of the total of the cross-sectional areas of the water guide grooves 19 and 20. It is within the following range (preferably, the upper limit is + 40% and the lower limit is −30%).
Thereby, although the flow rate of the cooling water flowing through the water flow part 16 can be made substantially uniform from the lower part to the upper part of the long piece member 10, the water guide grooves 19, 20 communicating the plane cross-sectional area of the cooling part 18 with the cooling part 18. It is possible to increase the cooling efficiency in the cooling section 18 by making it smaller than the total of the cross sectional areas of the above.
Further, the plane cross-sectional area of the connecting portion 29 may be set within the range of the cross-sectional area of the water guide grooves 19 and 20 defined as described above.
Note that linear water guide grooves 30 and 31 through which cooling water flows are formed at both ends in the width direction of the long piece member 10, but since this does not communicate with the cooling unit 18, this plane cross-sectional area is as described above. It is not included in the cross-sectional area of the water guide grooves 19 and 20.

On the back side of the long piece member 10 shown above (the side opposite to the cooling surface), a plurality of fastening means 12, 12a are used, for example, a stainless steel back plate 13 (for example, a thickness of 50 mm or more and 500 mm or more). The following is attached). At the time of this attachment, the water supply portion 15, the drainage portion 17 of the back plate 13, and the water passage portions of the long piece member 10 (straight water guides disposed on both sides in the width direction of the long piece member 10) Grooves (not shown) are formed so as to surround 16 (including grooves 30 and 31), and by arranging an O-ring (not shown) here, the adhesion between the long piece member 10 and the back plate 13 is improved, The leakage of the cooling water from the water flow part 16 is prevented.
As shown in FIG. 6, the fastening means 12, 12 a has a female screw portion 32 formed on the long piece member 10 and a male screw 33 that is screwed into the female screw portion 32 and fastens the back plate 13. . Further, in order to attach the male screw 33, a seal washer 35 that can be waterproofed is disposed in advance in the hole 34 formed in the back plate 13, thereby preventing leakage of cooling water from the portion to which the male screw 33 is attached. .

The male screw 33 is attached to the back plate 13 via one or a plurality of springs (an example of a buffer member) 36. The fastening force of the long piece member 10 with respect to the back plate 13 is adjusted, and its movement Is given a degree of freedom.
A plurality of fastening means 12 and 12a are provided at equal pitches in the longitudinal direction of the long piece member 10 (here, 8 locations), but the length of the long piece member 10 from the meniscus position to the lower part of the meniscus position is 50 mm. It is preferred to exclude the range. At this time, the male screw 33 in the range from the meniscus position to 50 mm below the meniscus position may be simply removed. However, the female screw portion is not formed in the long piece member, and the hole is not formed in the back plate. Is preferred. In addition, only the fastening means located near the meniscus position (for example, a range from the meniscus position to 50 mm below the meniscus position) is provided with a spring, and other parts are provided with no spring. You can also
Thereby, the restraining force of the long piece member by the back plate can be further weakened.

Moreover, you may form a coating layer in the surface (molten steel surface) of a long piece member.
For example, a Co alloy such as Co—Ni, a Ni alloy such as Ni—Fe, or Ni plating can be used for the coating layer, but thermal spraying (eg, Ni-based Cr—Si—B alloy) is also used. it can. This coating layer may be formed of the same type of component over the entire surface of the copper plate used for the long piece member, and plural types of components may be formed in different regions in the vertical direction of the copper plate. You may form each according to a function.
Each of the long piece members shown above is manufactured by forming a coating layer on the surface of the copper plate and then performing a conventionally known machining process on a predetermined shape.
As for the shape of the long piece member, the distance between the pair of long piece members may be the same in the drawing direction of the slab, but it is preferable that the long piece member be narrowed according to the solidification shrinkage shape of the slab.

Next, in order to confirm the operation and effect of the present invention, the structure of the cooling member (long piece member) shown in the conventional examples, comparative examples 1 and 2 and examples 1 and 2 is used to perform FEM analysis (finite element method). The results of the analysis using In addition, the cooling member of the conventional example has a water guide groove formed on the entire back surface side of the copper plate and is thick (19 mm) from the bottom of the water guide groove to the molten steel cooling surface. The thickness from the bottom of the water guide groove to the molten steel cooling surface is smaller than the example (15 mm), and the cooling member of Comparative Example 2 is thinner than the comparative example 1 from the bottom of the water guide groove to the molten steel cooling surface (13 mm). On the other hand, the cooling member of Example 1 is formed with a water passage portion having a cooling portion and a water guide groove on the back surface side of the copper plate, and with or without a bolt (male screw) in the second vertical stage of the copper plate. In addition, the cooling member of Example 2 does not use the second-stage bolt (male screw) in the longitudinal direction of the copper plate of Example 1, and further removes this bolt hole (female screw part). These test conditions and test results are shown in Tables 1 and 2. The copper plate material B is a high strength material of Cr-Zr-copper alloy, and the material A is a cold forging treatment applied to the high strength material of material B Cr-Zr-copper alloy. Further, the strength is increased.

Table 3 shows the material characteristics of the copper plate material, and Table 4 shows the results of collecting only the test results of the conventional examples, Comparative Examples 1 and 2, and Examples 1 and 2.

Hereinafter, a description will be given with reference to FIGS. In addition, the temperature distribution of FIG. 7 (A), the displacement distribution of FIG. 7 (B), the plastic strain distribution of FIG. 8 (A), and the plastic strain width of FIG. 9 (A) are plating of the plated copper plate. It is an analysis result on the surface, and the plastic strain distribution in FIG. 8B and the plastic strain width in FIG. 9B are the analysis results at the interface between the plating and the copper plate.

As is apparent from FIGS. 7 to 9 and Table 4, in the conventional example, the thickness of the upper portion of the copper plate is high because the thickness of the copper plate is too thick, and the binding force is also increased. For this reason, the generated plastic strain is large and the fatigue life is short.
Further, as in Comparative Example 1, by reducing the thickness of the copper plate of the meniscus portion, the restraining force was slightly improved and the fatigue life increased to about 1.2 times that of the conventional example, but it was not sufficient. .
Further, as in Comparative Example 2, the thickness of the copper plate at the meniscus portion is further reduced, so that the temperature of the upper portion of the copper plate is improved as compared with the case of Comparative Example 1, and fatigue is reduced due to relaxation of the binding force due to the reduction in thickness. The lifetime has increased to about 1.5 times that of the conventional example. However, remarkable results could not be obtained compared to the conventional case.

On the other hand, in Example 1, the restraining force was sufficiently relaxed by improving the structure of the upper part of the copper plate including the meniscus portion. Moreover, the copper plate temperature was also improved, and the fatigue life of the plating surface was improved to about 2.3 times. In addition, when the second-stage bolt was removed, it was further improved to about 3.4 times.
Moreover, the fatigue life of the base metal surface was improved to about 4.2 times by using a copper plate base material as a high strength material.
Furthermore, in Example 2, in addition to the structural improvement, by removing the second fastening bolt in the longitudinal direction, the restraining force was further improved, and the fatigue life of the plating surface was improved to about 4 times.
Further, the fatigue life of the base metal surface was improved to about 7.7 times by making the copper plate base material a high strength material.
From the above, it has been confirmed that by applying the present invention, the generation of cracks due to thermal stress caused by repeated loads can be suppressed and further prevented, and the life can be extended.

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 long piece member was demonstrated as a cooling member, it is good also considering only a short piece member or both a long piece member and a short piece member as a cooling member.
In the above-described embodiment, the configuration of a mold for manufacturing a slab, which is an example of a slab, has been described. However, a mold for manufacturing another slab having a different shape and size, for example, a billet, a bloom, or a beam blank. Of course, it is possible to apply the present invention.

(A) is a front view of a long piece member of a continuous casting mold according to an embodiment of the present invention, (B) is a cross-sectional view taken along the line aa of (A), and (C) is b of (A). It is -b arrow sectional drawing. It is a partial enlarged front view of the same long piece member. (A)-(C) are cc arrow sectional drawing, dd arrow sectional drawing, and ee arrow sectional drawing of FIG. 1 (A), respectively. (A) is ff arrow directional cross-sectional view of FIG. 2, (B) is gg arrow directional cross-sectional view of FIG. (A)-(D) is the perspective view which looked at the water flow part of the same long piece member from the surface side of the long piece member, respectively, The top view of the connection part of the water guide groove connected to the cooling part of the same long piece member, It is the perspective view which looked at the connection part of the groove | channel from the surface side of the long piece member, and the perspective view seen from the back surface side of the long piece member. It is explanatory drawing of the fastening means in the site | part close | similar to the meniscus position where a big thermal stress tends to generate | occur | produce. (A) is a graph which shows the temperature distribution on the surface of a long piece member, (B) is a graph which shows the displacement distribution on the surface of a long piece member. (A) is a graph which shows the plastic strain distribution in the plating surface of a long piece member, (B) is a graph which shows the plastic strain distribution in the base material surface of a long piece member. (A) is a graph which shows the plastic strain width in the plating surface at the time of the molten metal surface fluctuation | variation of a long piece member, (B) is a graph which shows the plastic strain width in the base material surface at the time of the molten metal surface fluctuation | variation of a long piece member. It is a top view of the casting mold for continuous casting which concerns on a prior art example. (A) is a partial enlarged front view of a short piece member and a long piece member of the casting mold for continuous casting, (B) is a cross-sectional view taken along line l-l in (A), and (C) is a m-m arrow in (A). (D) is a cross-sectional view taken along line nn of (A). (A) is a graph of the strain distribution when the long piece member of the continuous casting mold is hot, and (B) is a graph of the strain distribution when the molten metal level of the long piece member of the continuous casting mold is changed.

Explanation of symbols

10, 11: Long piece member, 12, 12a: Fastening means, 13, 14: Back plate (support member), 15: Water supply part, 16: Water flow part, 17: Drain part, 18: Cooling part, 19, 20 : Water guide groove, 21: space part, 22, 22a, 22b: thin plate member, 23: screw, 24: fixing part, 25: screw, 26: fixing part, 27: set screw, 28: back surface, 29: connection part, 30, 31: linear water guide groove, 32: female screw part, 33: male screw, 34: hole, 35: seal washer, 36: spring (buffer member)

The present invention relates to a continuous casting mold used for producing a slab.

Conventionally, molten steel is supplied to a continuous casting mold (hereinafter, also simply referred to as a mold) 80 shown in FIGS. 10 and 11A to 11D to cast a slab. The mold 80 is a state in which a pair of short piece members (also referred to as short side members) 81 and 82 composed of copper plates opposed to each other with a gap therebetween, and the short piece members 81 and 82 sandwiched from both sides in the width direction. And a pair of long piece members (also referred to as long side members) 83 and 84 formed of copper plates opposed to each other.
The short piece members 81 and 82 are mirror-symmetrical and have the same configuration, and a large number of water guide grooves 85 and 86 are provided in the vertical direction on the back surface side. The short piece members 81 and 82 are backed by bolts 87 on the back surface side. Plates (also called support members, cooling boxes, or water boxes) 88 and 89 are fixed. The long piece members 83 and 84 are also provided with a large number of water guide grooves 85 and 86 in the vertical direction on the back surface side, and the back plates 90 and 91 are fixed to the back surface side of the long piece members 83 and 84 by bolts 87. (For example, refer to Patent Document 1).

The mold 80 is configured to include short piece members 81 and 82, long piece members 83 and 84, and respective back plates 88 to 91, and a back plate 90 fixed to the long piece members 83 and 84 disposed to face each other. Bolts 92 are attached to both ends of 91 and fixed with nuts 93 via springs (not shown).
At the time of continuous casting work, as shown in FIG. 11 (B), from the water supply part 94 provided in the lower part of the back plates 88 to 91, a large number of short pieces 81 and 82 and long pieces 83 and 84 are provided. The cooling water is supplied to the drainage part 95 provided in the upper part of the back plates 88 to 91 through the water guide grooves 85 and 86. Thereby, while cooling the short piece members 81 and 82 and the long piece members 83 and 84, the molten steel is poured from above the mold 80 to perform the initial solidification of the molten steel, and the solidified slab is made at a substantially constant speed from below the mold. Drawing continuously to produce slabs.

JP 2003-136204 A

However, when continuous casting is performed with the above-described mold, for example, meniscus cracks (heat cracks generated near the meniscus level: hereinafter also referred to simply as cracks) have occurred in the short piece member and the long piece member. This meniscus crack is caused by, for example, the thermal effects on the mold due to repeated hot (during casting) and cold (after casting), and fluctuations in the mold surface level in the mold (the effects of bulging, nozzle discharge flow, or electromagnetic stirring). It is considered that the stress (plastic strain) amplitude caused by the temperature amplitude due to the above-mentioned fatigue failure (low cycle fatigue) caused by repeated load (thermal stress).
This meniscus crack is not only generated and propagated by mechanical fatigue fracture, but also, for example, a grain boundary crack generated by reaction with a low melting point metal (Zn attack etc.) or an alloy layer formed by reaction (very brittle) Some of them start from the drop-off part.

Here, a description will be given of a fracture site in a case where a repeated load due to repeated hot and cold is dominant among stress amplitudes caused by temperature amplitudes causing meniscus cracks.
FIG. 12A shows the strain distribution during hot (during casting) of the copper plate constituting the long piece member currently used. The analysis conditions were as follows: bolt mounting interval for fixing the copper plate to the back plate: 120 mm, casting speed: 2.8 (m / min), meniscus level: 100 mm from the upper end of the copper plate, cooling water flow rate: 4000 per copper plate (Liter / minute), cooling water temperature: 40 (° C.), cooling water pressure: 4 (kg / cm ² ), copper plate material: high strength material (CCM-B), plating specification: Co—Ni, copper plate thermal conductivity : 305 (kcal / m ² / hr), Co—Ni plating thermal conductivity: 58 (kcal / m / hr / ° C.), copper plate fastening condition: bolt M20 (SUS), initial fastening force 1600 kg, copper plate fastening surface friction Coefficient: 0.15.

As is clear from FIG. 12A, the amount of strain generated in the portion fixed by the bolt is affected by the restraining force due to the bolt fastening between the portion fixed by the bolt and the portion between the adjacent bolts. It is getting bigger.
Also, the place where the plastic strain is maximum is not about 130 mm from the upper end of the copper plate where the copper plate temperature is maximum, but is about 170 mm below the upper end of the copper plate that becomes the bolt fastening position in the second stage of the copper plate (strong binding force) Part).
In addition, since the location where the plastic strain amplitude (= 1/2 plastic strain width) is maximum corresponds to the location where the plastic strain is maximum, the fatigue life of the above-described location is the shortest (large crack).
However, since many of the crack occurrence locations are shifted to a range close to the meniscus level above the above-described position, it is considered that other amplitude loads are dominant factors of this crack.

Next, a description will be given of a fracture site in a case where the repeated load due to the fluctuation of the molten metal surface level in the mold is dominant among the stress amplitude generated by the temperature amplitude causing the meniscus crack.
FIG. 12 (B) shows the strain distribution of the bolt part when it is assumed that the fluctuation of the molten metal surface level occurs in the range of 100 mm ± 20 mm (80 mm or more and 120 mm or less) downward from the upper end of the copper plate.
The value of the (plastic) strain width curve when the fluctuation of the molten metal surface shown in FIG. 12 (B) is ± 20 mm is the plastic strain width generated between the maximum level and the minimum level of the molten metal surface, and the plastic strain amplitude is also plastic. It occurs according to the strain width.
Further, the location where the maximum strain amplitude is generated due to the fluctuation of the molten metal surface level is around 110 mm below the upper end of the mold under the condition that the fluctuation of the molten metal surface level is in the range of 100 mm ± 20 mm. In the examination example this time, it corresponds almost to the 115 mm level position).

In addition, the examination result shown above uses the simulation by the FEM analysis (analysis using the finite element method) using a computer, and the fatigue (crack) life estimated from the plastic strain amplitude caused by the fluctuation of the molten metal surface level This is done by relative comparison. The fatigue life was determined by Manson's common gradient method (ε _pa = ε f ^0.6 · Nf ^−0.6 / 2).
From the above, the occurrence of meniscus cracks is greatly influenced by the plastic strain amplitude due to the fluctuation of the molten metal surface level, and the repeated load generated by repeated hot and cold is combined with this. It is presumed that they are overlapping.

The present invention has been made in view of the above circumstances, and provides a continuous casting mold capable of suppressing and further preventing the occurrence of cracks due to thermal stress caused by repeated loads and extending the service life. With the goal.

The continuous casting mold according to the present invention that meets the above-mentioned object is a pair of short piece members that are arranged to face each other with a gap therebetween, and a pair of long piece members that are arranged to face each other while sandwiching the short piece members from both sides in the width direction. And a supporting member fixed to the back side of the short piece member and the long piece member by fastening means, and from the water supply portion provided at the lower part of the supporting member, the short piece member and the long piece member Molten steel supplied to the region formed by the short piece member and the long piece member by flowing cooling water to the drainage portion provided at the upper part of the support member through the water passage portion provided on the back side. In a mold for producing a drawn slab downward while cooling and solidifying the short piece member and the long piece member,
A cooling part in which at least the upper side of the cooling member consisting of one or both of the short piece member and the long piece member is flattened, and the water flow part is formed on the entire back surface of the thinned cooling member. And a large number of water guide grooves communicating with the cooling part and the water supply part, and the cooling part is provided on the back surface of the cooling member in a space provided on the back surface side of the thinned flat cooling member. On the other hand, the front surface of the thin plate member is arranged in parallel , and the tips of a plurality of set screws attached to the thin plate member and projecting to the back surface side of the cooling member are in contact with the back surface of the cooling member. It is a gap, and the attachment position of the fastening means is a portion excluding the range from the meniscus position of the cooling member to 50 mm below the meniscus position.

In the continuous casting mold according to the present invention, it is preferable that the thinned flat portion of the cooling member is in a range of 50 mm or more and 600 mm or less from the upper end of the cooling member.
In the continuous casting mold according to the present invention, the thickness of the thinned cooling member is preferably 5 mm or more and 30 mm or less.

In the continuous casting mold according to the present invention, the cooling section has a flat cross-sectional area equal to the sum of the cross-sectional areas of the water guide grooves communicating with the cooling section or a sum of the cross-sectional areas of the water guide grooves of −50. It is preferable to be within the range of not less than% and not more than 50%.
In the continuous casting mold according to the present invention, it is preferable that a flat cross-sectional area of the cooling portion is smaller than a sum of flat cross-sectional areas of the water guide grooves communicating with the cooling portion.
In the casting mold for continuous casting according to the present invention, the connection portion of the water guide groove communicating with the cooling portion is gradually widened toward the cooling portion with the inner width thereof being larger than the inner width of other portions of the water guide groove. It is preferable.

In the continuous casting mold according to claims 1 to 6, since at least the upper side of the cooling member is flattened, the upper structure of the cooling member is not provided with the water guide groove (slit) provided in the conventional mold. A thin plate structure can be formed. As a result, the restraining strain of the cooling member itself can be relaxed and the cooling efficiency can be increased as compared with the conventional water guide groove structure, so that the generation of cracks in the cooling member is suppressed (the generated strain is reduced). ) And the life of the mold can be extended.
In the case of the conventional water guide groove structure, the structure itself acts as a rib for preventing deformation of the cooling member, and thus restricts free deformation of the cooling member. For this reason, in the vicinity of the molten metal surface where the heat load is large, the restraint strain of the cooling member increases and the stress state deteriorates, that is, the occurrence of plastic strain increases.
In particular, since the continuous casting mold according to claim 2 defines the position where the cooling member is flattened, the thermal stress can be reliably reduced, and the occurrence frequency of cracks can be further reduced.
Since the continuous casting mold according to claim 3 defines the thickness of the thinned and flattened cooling member, the effect of reducing the thermal stress of the thinned and flattened portion can be further enhanced.

In the casting mold for continuous casting according to claim 1, since the water passing portion is formed by the cooling portion formed on the entire back surface side of the cooling member and the water guide groove communicating with the cooling portion, the stress can be relieved with a simple structure. In addition, the cooling efficiency can be improved, the thermal stress can be greatly relieved, and the amount of plastic strain generated can be reduced.
In the continuous casting mold according to the first aspect, since the gap serving as the cooling part is formed by a thin plate member disposed in the space part, the structure of the cooling part can be simplified, and the workability at the time of manufacture is also good.
The continuous casting mold according to claim 4 defines the relationship between the flat cross-sectional area of the cooling part and the sum of the flat cross-sectional areas of the water guide grooves, so that the cooling in the water flow part is performed from the lower part to the upper part of the cooling member. The water flow can be stabilized.

In the continuous casting mold according to the sixth aspect, the flow of the cooling water from the water guiding groove to the cooling part can be stabilized without any stagnation by defining the shape of the connecting part of the water guiding groove communicating with the cooling part.
Since the continuous casting mold according to claim 1 defines the mounting position of the fastening means, it is possible to reduce the restraining force by the fastening means at a portion where thermal stress is likely to occur, and to further reduce the generated thermal stress. Can do.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
As shown in FIGS. 1 to 6, a continuous casting mold (hereinafter also simply referred to as a mold) according to an embodiment of the present invention has a pair of short pieces (not shown) that are arranged to face each other at intervals. Side members), a pair of long piece members (also referred to as long side members) 10 and 11, which are opposed to each other while sandwiching the short piece members from both sides in the width direction, and the back surfaces of the short piece members and the long piece members 10 and 11 It has back plates (also referred to as cooling boxes or water boxes) 13 and 14 which are examples of support members fixed to the side by fastening means 12 and 12a, respectively. Thereby, from the water supply part 15 provided in the lower part of the back plates 13 and 14, the upper part of the back plates 13 and 14 through the water passing part 16 provided in the back surface side of the short piece member and the long piece members 10 and 11 While flowing cooling water to the drainage part 17 provided in the molten steel, the molten steel supplied in the region formed by the short piece members and the long piece members 10 and 11 is cooled and solidified by the short piece members and the long piece members 10 and 11. A downwardly drawn slab (an example of a cast piece) can be manufactured. In addition, since the short piece member and the long piece members 10 and 11 differ only in the width | variety and the other structure is substantially the same, and the long piece members 10 and 11 are mirror-symmetrical, below, FIGS. The long piece member 10 to be shown is a cooling member, and its configuration will be mainly described in detail.

Each short piece member is made of copper or a copper alloy, and has a thickness of about 10 mm to 100 mm, a width of about 50 mm to 300 mm, and a vertical length of about 600 mm to 1200 mm. Each of the long piece members 10 and 11 is made of copper or a copper alloy. For example, the thickness is about 10 mm or more and 100 mm or less, and the width (the width in contact with the cast piece) is about 600 mm or more and 3000 mm or less, and the length in the vertical direction. Is about the same as the short piece member.
Accordingly, the distance between the pair of short piece members arranged to face each other is about 600 mm to 3000 mm, the distance between the pair of long piece members 10 and 11 is about 50 mm to 300 mm, and the length of the mold in the vertical direction. Is about 600 mm or more and 1200 mm or less. In addition, the space | interval of the short piece member arrange | positioned facing can be changed within the above-mentioned range.
Thereby, for example, a slab having a width of about 600 mm to about 3000 mm and a thickness of about 50 mm to about 300 mm can be manufactured.

As shown in FIGS. 1A to 1C, FIG. 2, and FIGS. 3A to 3C, the water flow portion 16 provided on the back surface side of the long piece member 10 is at least of the long piece member 10. On the upper side, a cooling unit 18 and a plurality of water guide grooves 19 and 20 that communicate the cooling unit 18 and the water supply unit 15 are provided. The upper side of the long piece member 10 is a range of 50 mm to 600 mm from the upper end of the long piece member 10 (preferably, the upper limit is 500 mm, further 400 mm, the lower limit is 80 mm, and further 100 mm). This is because heat cracks that have conventionally occurred in the range of 80 mm or more and 150 mm or less from the upper end of the long piece member 10 are suppressed and further prevented.
The cooling portion 18 is a gap G formed by disposing the thin plate members 22, 22 a, and 22 b in the space portion 21 provided on the entire upper surface of the long piece member 10. The thin plate members 22, 22 a, 22 b have different shapes at both ends or one end in the width direction depending on the fastening means 12, 12 a. Moreover, the space part 21 is formed over the width direction of the long piece member 10, and the side cross-sectional shape is a ship shape.

The space portion 21 is formed so that the thickness T1 of the long piece member 10 is 5 mm or more and 30 mm or less. As a result, the long piece member 10 in this portion can be flattened.
Here, when the thickness of the long piece member of the thinned flat portion is less than 5 mm, the grinding allowance at the time of repeated use of the long piece member is reduced and the number of times the mold is used is reduced. On the other hand, when the thickness exceeds 30 mm, the thickness becomes too thick, and the amount of plastic strain increases due to an increase in generated temperature due to an increase in mold temperature and fastening constraints.
From the above, the thickness T1 of the thin flat member is 5 mm or more and 30 mm or less, but the upper limit is preferably 20 mm, more preferably 15 mm, and the lower limit is preferably 8 mm, more preferably 10 mm. .
A plurality (two in this case) of fixing parts 24 of screws 23 for attaching the upper part of the thin plate member 22 are provided at an upper position in the space part 21.

As shown in FIGS. 4 (A) and 4 (B), the large number of water guide grooves 19 and 20 communicating with the cooling unit 18 are thin in thickness T2 and T3 from the bottom position to the molten steel cooling surface of the long piece member 10. For example, it is formed so as to be thicker by about 5 mm or more and 20 mm or less than the thickness T1 of the flattened long piece member 10. In addition, the structure of the water guide groove 19 and the water guide groove 20 is the same except that the depth differs (the water guide groove 20 is deeper than the water guide groove 19). The water guide grooves 19 and 20 are linear along the longitudinal direction of the long piece member 10, and are formed at a predetermined pitch (for example, about 6 mm or more and 30 mm or less) in the width direction of the long piece member 10.
Therefore, between the adjacent water guide grooves 19 and 19 and the water guide grooves 19 and 20 becomes a fixing portion 26 of the screw 25 for attaching the lower part of the thin plate members 22, 22 a and 22 b.
Thereby, after arranging the thin plate members 22, 22 a, 22 b in the space portion 21, the upper and lower portions can be fixed to the long piece member 10 by the screws 23, 25. When fixed in this manner, the back surfaces of the thin plate members 22, 22 a, 22 b are arranged on the same plane as the back surface of the portion where the upper end portion of the long piece member 10 and the water guide grooves 19, 20 are formed. It has become.

The thin plate members 22, 22 a, 22 b are made of, for example, copper, copper alloy, aluminum, aluminum alloy, iron, or stainless steel having corrosion resistance, and a plurality (in the present embodiment, 15 in the width direction). ). Each of the thin plate members 22, 22 a, and 22 b has a ship-like cross-sectional shape, and is attached to the thin plate members 22, 22 a, 22 b and includes a plurality of set screws 27 that protrude a predetermined length toward the back side of the long piece member 10. The tip is in contact with the back surface 28 of the long flat member 10 which is thin and flat, and a certain gap G can be formed.
The gap G is, for example, about 2 mm to 7 mm, and cooling water flows through this portion.
5A to 5D show the portion of the water flow portion 16 through which the cooling water flows, but the connection portion 29 of the water guide grooves 19 and 20 communicating with the cooling portion 18 is the cooling portion 18. The inner width is gradually widened more continuously (curved surface) than the inner width (for example, about 1 mm or more and about 5 mm or less) of other portions of the water guide grooves 19 and 20. Moreover, the connection part 29 is gradually made shallower than the depth of the other part of the water guide grooves 19 and 20 toward the cooling part 18.

The flat cross-sectional area of the cooling unit 18 described above is the same as the total of the cross-sectional areas of the water guide grooves 19 and 20 communicating with the cooling unit 18, or −50% or more + 50% of the total of the cross-sectional areas of the water guide grooves 19 and 20. It is within the following range (preferably, the upper limit is + 40% and the lower limit is −30%).
Thereby, although the flow rate of the cooling water flowing through the water flow part 16 can be made substantially uniform from the lower part to the upper part of the long piece member 10, the water guide grooves 19, 20 communicating the plane cross-sectional area of the cooling part 18 with the cooling part 18. It is possible to increase the cooling efficiency in the cooling section 18 by making it smaller than the total of the cross sectional areas of the above.
Further, the plane cross-sectional area of the connecting portion 29 may be set within the range of the cross-sectional area of the water guide grooves 19 and 20 defined as described above.
Note that linear water guide grooves 30 and 31 through which cooling water flows are formed at both ends in the width direction of the long piece member 10, but since this does not communicate with the cooling unit 18, this plane cross-sectional area is as described above. It is not included in the cross-sectional area of the water guide grooves 19 and 20.

On the back side of the long piece member 10 shown above (the side opposite to the cooling surface), a plurality of fastening means 12, 12a are used, for example, a stainless steel back plate 13 (for example, a thickness of 50 mm or more and 500 mm or more). The following is attached). At the time of this attachment, the water supply portion 15, the drainage portion 17 of the back plate 13, and the water passage portions of the long piece member 10 (straight water guides disposed on both sides in the width direction of the long piece member 10) Grooves (not shown) are formed so as to surround 16 (including grooves 30 and 31), and by arranging an O-ring (not shown) here, the adhesion between the long piece member 10 and the back plate 13 is improved, The leakage of the cooling water from the water flow part 16 is prevented.
As shown in FIG. 6, the fastening means 12, 12 a has a female screw portion 32 formed on the long piece member 10 and a male screw 33 that is screwed into the female screw portion 32 and fastens the back plate 13. . Further, in order to attach the male screw 33, a seal washer 35 that can be waterproofed is disposed in advance in the hole 34 formed in the back plate 13, thereby preventing leakage of cooling water from the portion to which the male screw 33 is attached. .

The male screw 33 is attached to the back plate 13 via one or a plurality of springs (an example of a buffer member) 36. The fastening force of the long piece member 10 with respect to the back plate 13 is adjusted, and its movement Is given a degree of freedom.
A plurality of fastening means 12 and 12a are provided at equal pitches in the longitudinal direction of the long piece member 10 (here, 8 locations), but the length of the long piece member 10 from the meniscus position to the lower part of the meniscus position is 50 mm. It is preferred to exclude the range. At this time, the male screw 33 in the range from the meniscus position to 50 mm below the meniscus position may be simply removed. However, the female screw portion is not formed in the long piece member, and the hole is not formed in the back plate. Is preferred. In addition, only the fastening means located near the meniscus position (for example, a range from the meniscus position to 50 mm below the meniscus position) is provided with a spring, and other parts are provided with no spring. You can also
Thereby, the restraining force of the long piece member by the back plate can be further weakened.

Moreover, you may form a coating layer in the surface (molten steel surface) of a long piece member.
For example, a Co alloy such as Co—Ni, a Ni alloy such as Ni—Fe, or Ni plating can be used for the coating layer, but thermal spraying (eg, Ni-based Cr—Si—B alloy) is also used. it can. This coating layer may be formed of the same type of component over the entire surface of the copper plate used for the long piece member, and plural types of components may be formed in different regions in the vertical direction of the copper plate. You may form each according to a function.
Each of the long piece members shown above is manufactured by forming a coating layer on the surface of the copper plate and then performing a conventionally known machining process on a predetermined shape.
As for the shape of the long piece member, the distance between the pair of long piece members may be the same in the drawing direction of the slab, but it is preferable that the long piece member be narrowed according to the solidification shrinkage shape of the slab.

Next, in order to confirm the operation and effect of the present invention, the structure of the cooling member (long piece member) shown in the conventional examples, comparative examples 1 and 2 and examples 1 and 2 is used to perform FEM analysis (finite element method). The results of the analysis using In addition, the cooling member of the conventional example has a water guide groove formed on the entire back surface side of the copper plate and is thick (19 mm) from the bottom of the water guide groove to the molten steel cooling surface. The thickness from the bottom of the water guide groove to the molten steel cooling surface is smaller than the example (15 mm), and the cooling member of Comparative Example 2 is thinner than the comparative example 1 from the bottom of the water guide groove to the molten steel cooling surface (13 mm). On the other hand, the cooling member of Example 1 is formed with a water passage portion having a cooling portion and a water guide groove on the back surface side of the copper plate, and with or without a bolt (male screw) in the second vertical stage of the copper plate. In addition, the cooling member of Example 2 does not use the second-stage bolt (male screw) in the longitudinal direction of the copper plate of Example 1, and further removes this bolt hole (female screw part). These test conditions and test results are shown in Tables 1 and 2. The copper plate material B is a high strength material of Cr-Zr-copper alloy, and the material A is a cold forging treatment applied to the high strength material of material B Cr-Zr-copper alloy. Further, the strength is increased.

Table 3 shows the material characteristics of the copper plate material, and Table 4 shows the results of collecting only the test results of the conventional examples, Comparative Examples 1 and 2, and Examples 1 and 2.

Hereinafter, a description will be given with reference to FIGS. In addition, the temperature distribution of FIG. 7 (A), the displacement distribution of FIG. 7 (B), the plastic strain distribution of FIG. 8 (A), and the plastic strain width of FIG. 9 (A) are plating of the plated copper plate. It is an analysis result on the surface, and the plastic strain distribution in FIG. 8B and the plastic strain width in FIG. 9B are the analysis results at the interface between the plating and the copper plate.

As is apparent from FIGS. 7 to 9 and Table 4, in the conventional example, the thickness of the upper portion of the copper plate is high because the thickness of the copper plate is too thick, and the binding force is also increased. For this reason, the generated plastic strain is large and the fatigue life is short.
Further, as in Comparative Example 1, by reducing the thickness of the copper plate of the meniscus portion, the restraining force was slightly improved and the fatigue life increased to about 1.2 times that of the conventional example, but it was not sufficient. .
Further, as in Comparative Example 2, the thickness of the copper plate at the meniscus portion is further reduced, so that the temperature of the upper portion of the copper plate is improved as compared with the case of Comparative Example 1, and fatigue is reduced due to relaxation of the binding force due to the reduction in thickness. The lifetime has increased to about 1.5 times that of the conventional example. However, remarkable results could not be obtained compared to the conventional case.

On the other hand, in Example 1, the restraining force was sufficiently relaxed by improving the structure of the upper part of the copper plate including the meniscus portion. Moreover, the copper plate temperature was also improved, and the fatigue life of the plating surface was improved to about 2.3 times. In addition, when the second-stage bolt was removed, it was further improved to about 3.4 times.
Moreover, the fatigue life of the base metal surface was improved to about 4.2 times by using a copper plate base material as a high strength material.
Furthermore, in Example 2, in addition to the structural improvement, by removing the second fastening bolt in the longitudinal direction, the binding force was further improved, and the fatigue life of the plating surface was improved to about 4 times.
Further, the fatigue life of the base metal surface was improved to about 7.7 times by making the copper plate base material a high strength material.
From the above, it was confirmed that by applying the present invention, it was possible to suppress and further prevent the occurrence of cracks due to thermal stress caused by repeated loads, thereby extending the life.

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 long piece member was demonstrated as a cooling member, it is good also considering only a short piece member or both a long piece member and a short piece member as a cooling member.
In the above-described embodiment, the configuration of a mold for manufacturing a slab, which is an example of a cast slab, has been described. Of course, it is possible to apply the present invention.

(A) is a front view of a long piece member of a continuous casting mold according to an embodiment of the present invention, (B) is a cross-sectional view taken along the line aa of (A), and (C) is b of (A). It is -b arrow sectional drawing. It is a partial enlarged front view of the same long piece member. (A)-(C) are cc arrow sectional drawing, dd arrow sectional drawing, and ee arrow sectional drawing of FIG. 1 (A), respectively. (A) is ff arrow directional cross-sectional view of FIG. 2, (B) is gg arrow directional cross-sectional view of FIG. (A)-(D) is the perspective view which looked at the water flow part of the same long piece member from the surface side of the long piece member, respectively, The top view of the connection part of the water guide groove connected to the cooling part of the same long piece member, It is the perspective view which looked at the connection part of the groove | channel from the surface side of the long piece member, and the perspective view seen from the back surface side of the long piece member. It is explanatory drawing of the fastening means in the site | part close | similar to the meniscus position where a big thermal stress tends to generate | occur | produce. (A) is a graph which shows the temperature distribution on the surface of a long piece member, (B) is a graph which shows the displacement distribution on the surface of a long piece member. (A) is a graph which shows the plastic strain distribution in the plating surface of a long piece member, (B) is a graph which shows the plastic strain distribution in the base material surface of a long piece member. (A) is a graph which shows the plastic strain width in the plating surface at the time of the molten metal surface fluctuation | variation of a long piece member, (B) is a graph which shows the plastic strain width in the base material surface at the time of the molten metal surface fluctuation | variation of a long piece member. It is a top view of the casting mold for continuous casting which concerns on a prior art example. (A) is a partial enlarged front view of a short piece member and a long piece member of the casting mold for continuous casting, (B) is a cross-sectional view taken along line l-l in (A), and (C) is a m-m arrow in (A). (D) is a cross-sectional view taken along line nn of (A). (A) is a graph of the strain distribution when the long piece member of the continuous casting mold is hot, and (B) is a graph of the strain distribution when the molten metal level of the long piece member of the continuous casting mold is changed.

Explanation of symbols

10, 11: Long piece member, 12, 12a: Fastening means, 13, 14: Back plate (support member), 15: Water supply part, 16: Water flow part, 17: Drain part, 18: Cooling part, 19, 20 : Water guide groove, 21: space part, 22, 22a, 22b: thin plate member, 23: screw, 24: fixing part, 25: screw, 26: fixing part, 27: set screw, 28: back surface, 29: connection part, 30, 31: linear water guide groove, 32: female screw part, 33: male screw, 34: hole, 35: seal washer, 36: spring (buffer member)

Claims (9)

A pair of short piece members arranged to face each other with a gap, a pair of long piece members arranged to face each other with the short piece members sandwiched from both sides in the width direction, and a back side of the short piece member and the long piece member Each of the support members fixed by the fastening means, from the water supply portion provided in the lower portion of the support member, through the water passing portion provided on the back side of the short piece member and the long piece member, Cooling water is allowed to flow to a drainage section provided at the upper part of the support member, and the molten steel supplied in the region formed by the short piece member and the long piece member is cooled and solidified by the short piece member and the long piece member. While in the mold to produce the drawn slab downward,
A continuous casting mold, wherein at least an upper side of a cooling member composed of one or both of the short piece member and the long piece member is formed into a thin flat plate. 2. The continuous casting mold according to claim 1, wherein the thinned flat portion of the cooling member is in a range of 50 mm to 600 mm from the upper end of the cooling member. 3. The continuous casting mold according to claim 1, wherein the thickness of the cooling member formed into a flat plate is 5 mm or more and 30 mm or less. 4. The continuous casting mold according to any one of claims 1 to 3, wherein the water flow portion includes a cooling portion formed on the entire back surface side of the cooling member that has been flattened, and the cooling portion and the water supply. A continuous casting mold having a plurality of water guide grooves communicating with each other. 5. The continuous casting mold according to claim 4, wherein the cooling part is a gap formed by arranging a thin plate member in a space provided on the back side of the thinned flat cooling member. Continuous casting mold. 6. The continuous casting mold according to claim 4, wherein a planar cross-sectional area of the cooling part is the same as a sum of flat cross-sectional areas of the water guiding grooves communicating with the cooling part, or the water guiding grooves. A continuous casting mold characterized in that it is within a range of -50% or more and + 50% or less of the total cross-sectional area. The continuous casting mold according to any one of claims 4 to 6, wherein the connecting portion of the water guiding groove communicating with the cooling portion is directed toward the cooling portion, and the inner width thereof is the other portion of the water guiding groove. A mold for continuous casting, characterized in that it is gradually widened from the inner width. The casting mold for continuous casting according to any one of claims 1 to 7, wherein the attachment position of the fastening means is a portion excluding a range from the meniscus position of the cooling member to 50 mm below the meniscus position. A mold for continuous casting characterized by 8. The continuous casting mold according to claim 1, wherein the fastening means positioned in the vicinity of the meniscus position of the cooling member includes a buffer member for adjusting a fastening force of the cooling member with respect to the support member. A casting mold for continuous casting, characterized in that is provided.

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