JP7410372B2 - Continuous casting roll - Google Patents

Description

The present invention relates to a continuous casting roll used to convey a mold in continuous casting equipment that continuously casts slabs.

In a continuous casting apparatus for producing slabs such as slabs, molten steel injected into a mold is cooled by a cooling means, a solidified shell grows, and the slab is pulled out from below the mold. The slab pulled out from the mold is conveyed while being held between continuous casting rolls.
Here, in the above-mentioned continuous casting roll, since it comes into contact with the hot slab immediately after casting, a heat-resistant layer made of a material with excellent heat resistance is usually provided on the outer peripheral surface of the roll body made of SUS steel or the like. It is said to be a formed structure.

In the continuous casting roll, since it is pressed against the slab while rotating, the above-mentioned heat-resistant layer is subjected to a cold/hot cycle. That is, in the continuous casting roll, thermal expansion when in contact with a hot slab and contraction when not in contact with the slab are repeated, and thermal stress acts on the roll. For this reason, cracks may occur on the surface of the continuous casting roll due to fatigue.
When such cracks occur, the continuous casting roll is reused by removing the crack by grinding the outer peripheral surface of the continuous casting roll, and then re-forming the heat-resistant layer. If the cracks propagate internally and reach the roll body, the amount of grinding will increase significantly, and if the cracks are severe enough, the roll body cannot be reused.

Therefore, various techniques for suppressing the occurrence of cracks on the outer circumferential surface of a casting roll have been proposed, as shown in Patent Documents 1 to 5, for example.
In Patent Documents 1 to 3, by forming a plurality of circumferential grooves extending in the circumferential direction on the outer peripheral surface of the continuous casting roll, heat acting on the vicinity of the outer peripheral surface of the continuous casting roll during cold cycle load is reduced. Techniques have been proposed to reduce stress and suppress the occurrence of cracks.
Further, in Patent Documents 4 and 5, an annular cavity extending in the circumferential direction is provided inward in the radial direction of the outer circumferential surface, and thermal stress that acts in the vicinity of the outer circumferential surface of the continuous casting roll during cold and hot cycle loads is disclosed. Techniques have been proposed to reduce this and suppress the occurrence of cracks.

Utility Model Publication No. 03-024354 Japanese Patent Application Publication No. 10-156499 Japanese Patent Application Publication No. 2015-093302 Japanese Patent Application Publication No. 2004-195517 Japanese Patent Application Publication No. 2007-050430

By the way, recently, in continuous casting of slabs, the casting speed has tended to be increased from the viewpoint of improving production efficiency, and the temperature of the slabs in contact with the continuous casting rolls is high, and The period of heating and cooling cycles for the rolls is also shortened. For this reason, the outer circumferential surface of the continuous casting roll is subjected to severe cooling and heating cycles, and cracks tend to occur easily.
Therefore, it is required to suppress the occurrence of cracks on the outer circumferential surface of continuous casting rolls and the propagation of the cracks inward in the radial direction, more than ever before.

The present invention has been made in view of the above-mentioned situation, and even under severe usage environments, it is possible to suppress the occurrence of cracks on the outer circumferential surface and the propagation of cracks inward in the radial direction, thereby extending the service life. The purpose of the present invention is to provide a roll for continuous casting that can be used for continuous casting.

In order to solve the above problems, the inventors of the present invention have made extensive studies and found that when circumferential grooves are formed on the outer peripheral surface of a continuous casting roll, the circumferential grooves are not formed when a thermal cycle is applied. It was found that, although the thermal stress was relaxed in the area where the circumferential groove was formed, tensile stress was applied radially inward in the flat area where the circumferential groove was not formed, causing the crack to propagate radially inward. In addition, when an annular cavity is provided inside, when a thermal cycle is applied, high stress acts on a certain thickness area of the surface layer, which tends to cause cracks, and these cracks extend all the way to the cavity. I knew it was progressing.
When a circumferential groove is formed on the outer circumferential surface of a continuous casting roll and an annular cavity is provided inside, the radially inward tensile stress is relaxed and the surface layer has high stress areas. It was found that the cracks became thinner, suppressing the occurrence of cracks, and that the cracks did not propagate deeply inward in the radial direction, but instead propagated circumferentially in a range close to the surface layer.

The present invention has been made based on the above-mentioned findings, and the continuous casting roll according to the present invention is a continuous casting roll used for conveying slabs to be continuously cast, and includes a roll body, a heat-resistant layer formed on the outer peripheral surface of the roll body, and a plurality of circumferential grooves extending in the circumferential direction are formed on the outer peripheral surface of the heat-resistant layer in the axial direction of the roll body. The bottom of the circumferential groove is formed in a curved shape in a cross section along the axis of the roll body, and an annular cavity extending in the circumferential direction is provided inside the heat-resistant layer. A plurality of cavities are formed in the axial direction of the roll body, and each of the cavities has a curved bottom portion located radially inward when viewed from a cross section along the axis of the roll body. At least a part of the part is disposed radially inward of the flat area where the circumferential groove is not formed, and the radius of curvature of the groove bottom of the circumferential groove is in the range of 30 mm to 50 mm, and It is characterized in that the radius of curvature of the bottom of the cavity is within a range of 2 mm or more and 3 mm or less .

According to the continuous casting roll having this configuration, a circumferential groove is formed on the outer peripheral surface of the heat-resistant layer, and an annular cavity extending in the circumferential direction is further formed inside the heat-resistant layer, At least a portion of the plurality of hollow portions is disposed radially inward of the flat region where the circumferential groove is not formed, so that the circumferential groove is not formed when a thermal cycle is applied. Because large tensile stress does not act on the radially inward area of the flat area that is not flat, and the thickness of the area with high stress on the surface layer becomes thinner, cracks occur and the cracks move radially inward. Progress can be suppressed. Therefore, propagation of cracks to the roll body is prevented, the depth of the cracks becomes shallow, and the amount of grinding of the outer circumferential surface when the roll is reused can be reduced. Furthermore, the roll body can be reused, and the useful life of the roll body can be extended.

As described above, according to the present invention, continuous casting can suppress the occurrence of cracks on the outer circumferential surface and the propagation of cracks inward in the radial direction even under severe use environments, and can extend the service life. We can provide rolls for

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing an example of continuous casting equipment to which a continuous casting roll according to an embodiment of the present invention is applied. FIG. 1 is a schematic explanatory diagram of a continuous casting roll according to an embodiment of the present invention. FIG. 2 is an enlarged explanatory view of a heat-resistant layer of a continuous casting roll according to an embodiment of the present invention. It is an explanatory view showing a thermal analysis model of a roll for continuous casting. It is an explanatory view showing boundary conditions in thermal analysis of a roll for continuous casting. It is an explanatory view showing the thermal analysis result of a roll for continuous casting. FIG. 3 is an enlarged explanatory view of a heat-resistant layer of a continuous casting roll according to another embodiment of the present invention.

EMBODIMENT OF THE INVENTION Below, the roll for continuous casting which is an embodiment of this invention is demonstrated with reference to the attached drawing. Note that the present invention is not limited to the following embodiments.
First, an example of continuous casting equipment to which a continuous casting roll according to an embodiment of the present invention is applied will be described.

The continuous casting equipment 10 shown in FIG. 1 includes a mold 11, an immersion nozzle 12 for supplying molten steel to the mold, and a plurality of continuous casting rolls 30 located below the mold 11 and supporting a slab 1. It is equipped with group 20.
In addition, in the continuous casting machine 10 of this embodiment, there is a vertical part 14 that pulls out the slab 1 drawn out from the mold 11 downward, a bending part 15 that bends the slab 1, and a vertical part 15 that bends the slab 1. This is a vertical bending type continuous casting machine having a straightening section 16 for returning the slab and a horizontal section 17 for horizontally conveying the slab 1.

The roll group 20 includes a pinch roll part 24 located in the vertical part 14, a bending roll part 25 located in the bending part 15, a straightening roll part 26 located in the straightening part 16, and a horizontal roll part located in the horizontal part 17. It is equipped with 27.
The continuous casting rolls 30 extend in the width direction of the slab 1 and are configured to support the long sides of the slab 1.
Further, between the plurality of continuous casting rolls 30 arranged at intervals in the drawing direction Z of the slab 1, cooling water is jetted toward the long side surface of the slab 1 as a secondary cooling means. A spray nozzle (not shown) is provided.

As shown in FIG. 2, the continuous casting roll 30 of this embodiment includes a roll body 31 and a heat-resistant layer 32 formed on the outer peripheral surface of the roll body 31.
Here, the roll main body 31 is made of, for example, SUS steel, and has a shape along the axis O. Note that a water cooling mechanism (not shown) is provided inside the roll body 31.
The heat-resistant layer 32 is made of a hard material such as SUS steel that has hard properties, and in this embodiment, it is formed by overlaying the above-mentioned hard material on the outer peripheral surface of the roll body 31. ing. Note that the thickness of the heat-resistant layer 32 (thickness at a flat portion 36 described later) is preferably within a range of 27 mm or more and 50 mm or less.

Here, FIG. 3 shows the heat-resistant layer 32 of the continuous casting roll 30 according to this embodiment. In addition, in FIG. 3, the X direction is the axis O direction, and the Y direction is the radial direction.
As shown in FIG. 3, the heat-resistant layer 32 of the continuous casting roll 30 of this embodiment includes a first layer 32A located radially inward, and a layer laminated radially outward of this first layer 32A. A second layer 32B.
In the continuous casting roll 30 of this embodiment, as shown in FIG. A plurality of them are formed along the X direction in FIG.
Further, inside the heat-resistant layer 32, a plurality of annular hollow portions 37 extending in the circumferential direction are formed along the axis O direction of the roll body 31 (X direction in FIG. 3). In addition, in this cavity part 37, the bottom part 37a located radially inward when seen from the cross section along the axis O of the roll main body 31 is formed in the shape of a curved surface.
Note that at least some of the plurality of cavities 37 are arranged radially inward of the flat region 36 in which the circumferential groove 35 is not formed.

Here, in the above-mentioned circumferential groove 35, in the cross section along the axis O, the radius of curvature of the groove bottom is within the range of 30 mm to 50 mm, and the groove depth (radial length of the roll body 31) is 2.5 mm. It is preferable that the distance between the grooves is within the range of 44 mm or more and 80 mm or less.
When the radius of curvature of the groove bottom is within the range of 30 mm or more and 50 mm or less, stress concentration at the groove bottom can be suppressed.
Furthermore, when the groove depth is within the range of 2.5 mm or more and 4.0 mm or less, thermal stress can be sufficiently alleviated, and the rigidity of the flat region 36 in contact with the slab 1 can be ensured. becomes possible.
Furthermore, when the interval between the grooves is within the range of 44 mm or more and 80 mm or less, it is possible to ensure the rigidity of the flat region 36 that contacts the slab 1.

In the cross section along the axis O, the hollow portion 37 has a radius of curvature of the bottom portion 37a within a range of 2 mm or more and 3 mm or less, a height (radial length of the roll body 31) within a range of 20 mm or more and 30 mm or less, and a width interval. is within the range of 15 mm or more and 30 mm or less, the distance from the outer circumferential surface of the flat area 36 to the outer circumferential edge of the hollow portion 37 is within the range of 7 mm or more and 10 mm or less, and the distance from the outer circumferential surface of the roll body 31 to the inner circumferential edge of the hollow portion 37 is within the range of 7 mm or more and 10 mm or less. It is preferable that the distance is within a range of 0 mm or more and 10 mm or less.
When the radius of curvature of the bottom portion 37a in the cross section along the axis O is within the range of 2 mm or more and 3 mm or less, stress concentration in the bottom portion 37a can be suppressed.
In addition, the height is within the range of 20 mm or more and 30 mm or less, the width interval is within the range of 15 mm or more and 30 mm or less, and the distance from the outer peripheral surface of the flat area 36 to the outer peripheral end of the hollow part 37 is within the range of 7 mm or more and 10 mm or less, When the distance from the outer circumferential surface of the roll body 31 to the inner circumferential end of the cavity 37 is within the range of 0 mm or more and 10 mm or less, thermal stress can be sufficiently alleviated.

Here, FIGS. 4 to 6 show the results of heat transfer analysis and elastic analysis performed using the finite element method, and calculation of the thermal stress distribution in the heat-resistant layer during cooling and heating cycle loads.
A continuous casting roll 30 was assumed to have a structure in which a heat-resistant layer 32 with a thickness of 30 mm was formed on the outer peripheral surface of a roll body 31 with a diameter of 345 mm. Here, as shown in Fig. 4, four types of Analysis was performed using the model.
As shown in FIG. 5, the temperature at the center of the water-cooled roll body 31 was set to 30°C, the temperature of the slab 1 was set to 1100°C, and the emissivity was set to 0.4. The thermal boundary conditions on the outer circumferential surface of the rotating continuous casting roll 30 were as shown in FIG. 5, and the thermal stress when the continuous casting roll 30 rotated 10 times was analyzed. The results are shown in FIG.

As shown in FIG. 6, (a) without the circumferential groove and cavity, tensile stress acts widely on the radially inner portion. (b) With only the circumferential groove, tensile stress acts radially inward in the flat region where the circumferential groove is not provided. For this reason, there is a possibility that the crack will develop radially inward. (c) In the cavity alone, the radially inward tensile stress is relaxed, but the surface layer has a thick portion with high stress, and cracks are likely to occur in the surface layer.
On the other hand, in the case (d) with a circumferential groove and a hollow portion, the radially inward tensile stress is relaxed, and the high-stress portion of the surface layer is thinner. As a result, the cracks in the surface layer do not develop inward in the radial direction, but in the circumferential direction, and the cracks remain in the surface layer.

From the above analysis results, in the continuous casting roll 30 of this embodiment, a circumferential groove 35 is formed on the outer peripheral surface of the heat-resistant layer 32, and an annular cavity 37 is formed inside the heat-resistant layer 32. Therefore, the tensile stress in the radially inward direction is relaxed, and the high stress portion of the surface layer becomes thinner, making it possible to suppress the occurrence of cracks and the propagation of the cracks in the radial direction.

Here, the continuous casting roll 30 of this embodiment can be manufactured, for example, by the manufacturing method shown below.
First, the first layer 32A is formed on the outer circumferential surface of the roll body 31 by overlay welding an alloy or the like constituting the heat-resistant layer 32. A slit that will become the cavity 37 is formed by machining or etching from the outer peripheral surface of the first layer 32A. With the slits formed, the second layer 32B is formed by overlay welding the alloy or the like constituting the heat-resistant layer 32. Thereafter, a circumferential groove 35 is formed on the outer peripheral surface of the heat-resistant layer 32 by machining.
Through such steps, it becomes possible to manufacture the continuous casting roll 30 of this embodiment.

According to the continuous casting roll 30 of this embodiment configured as described above, the circumferential groove 35 is formed on the outer peripheral surface of the heat-resistant layer 32, and furthermore, the circumferential groove 35 is formed inside the heat-resistant layer 32 and extends in the circumferential direction. At least a part of the plurality of cavities 37 is disposed radially inward of the flat region 36 where the circumferential groove 35 is not formed, so that cold and heat When a cycle is applied, no tensile stress acts inward in the radial direction, and the thickness of the area with high stress on the surface layer becomes thinner, so cracks occur and the cracks propagate inward in the radial direction. can be restrained from doing so. Therefore, the propagation of cracks to the roll body 31 is prevented, the depth of the cracks becomes shallower, the continuous casting roll 30 can be reused relatively easily, and the service life of the continuous casting roll 30 is extended. It is possible to extend it.

In addition, in this embodiment, in the cross section along the axis O, the radius of curvature of the groove bottom is within the range of 30 mm or more and 50 mm or less, and the groove depth (radial length of the roll body 31) is 2.5 mm or more and 4.0 mm or less. If the groove spacing is within the range of 44 mm or more and 80 mm or less, thermal stress can be sufficiently relaxed to suppress the occurrence of cracks, and the flat area 36 in contact with the slab 1 can be Rigidity can be ensured, and the slab 1 can be transported stably.

Furthermore, in this embodiment, the radius of curvature of the bottom portion 37a of the hollow portion 37 is within the range of 2 mm or more and 3 mm or less, the height (radial length of the roll body 31) is within the range of 20 mm or more and 30 mm or less, and the width interval is within the range of 2 mm or more and 3 mm or less. Within the range of 15 mm or more and 30 mm or less, the distance from the outer circumferential surface of the flat area 36 to the outer circumferential edge of the hollow portion 37 within the range of 7 mm or more and 10 mm or less, the distance from the outer circumferential surface of the roll body 31 to the inner circumferential edge of the hollow portion 37 When it is within the range of 0 mm or more and 10 mm or less, it becomes possible to sufficiently relax thermal stress and suppress the occurrence of cracks.

Although the continuous casting roll which is an embodiment of the present invention has been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical idea of the invention.
For example, although the present embodiment has been described using the continuous casting machine shown in FIG. 1 as an example, the present invention is not limited to this and can be applied to continuous casting machines having other configurations.
Further, in the present embodiment, a structure has been described in which the hollow portion 37 is provided also inward in the radial direction of the circumferential groove 35, but the structure is not limited to this, and as shown in FIG. A structure may be adopted in which the cavity 37 is provided only in the radial direction of the flat region 36 where the groove 35 is not formed.

30 Continuous casting roll 31 Roll body 32 Heat-resistant layer 35 Circumferential groove 36 Flat area 37 Cavity part

Claims (3)

A continuous casting roll used for conveying continuously cast slabs,
It includes a roll body and a heat-resistant layer formed on the outer peripheral surface of the roll body,
A plurality of circumferential grooves extending in the circumferential direction are formed on the outer peripheral surface of the heat-resistant layer in the axial direction of the roll body, and the circumferential grooves are grooves in a cross section along the axis of the roll body. The bottom is formed into a curved shape,
Inside the heat-resistant layer, a plurality of annular hollow portions extending in the circumferential direction are formed in the axial direction of the roll body, and the hollow portion is The bottom part located radially inward is formed into a curved shape,
At least a portion of the plurality of hollow portions are disposed radially inward of the flat region where the circumferential groove is not formed,
A roll for continuous casting, characterized in that the radius of curvature of the bottom of the circumferential groove is in the range of 30 mm to 50 mm, and the radius of curvature of the bottom of the cavity is in the range of 2 mm to 3 mm . 2. The continuous casting roll according to claim 1, wherein the circumferential groove has a radius of curvature at the bottom of the groove in a cross section along the axis of the roll body of 30 mm or more. 2. The roll body according to claim 1, wherein the circumferential groove portions and the flat regions are alternately arranged in the axial direction of the roll body, and the hollow portion is formed only radially inward of the flat region. The continuous casting roll according to claim 1 or claim 2.

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