JP7067331B2 - Roll for continuous casting - Google Patents

Description

The present invention relates to a roll for continuous casting, which is installed in a secondary cooling zone of a continuous casting machine and has a plurality of slits formed by grooves extending in the circumferential direction formed on the surface layer portion.

In continuous casting of slabs by a continuous casting machine, the slabs drawn from the mold are water-cooled by a cooling nozzle, transported downward by a roll for continuous casting, and then cut to a predetermined length by a slab cutting machine. Will be done.

In the roll for continuous casting, cracks are generated in the surface layer portion due to thermal stress due to repeated contact with high-temperature slabs and contact with cooling water, and reaction force from the slabs, and the rolls develop into continuous cracks. If cracks grow, the roll for continuous casting may break, and there is also a problem that the roll life is shortened.

To solve the above problems, there is known a technique of providing a slit formed by a groove in the circumferential direction on the surface layer portion of a continuous casting roll. When the slit is provided in the surface layer portion of the roll for continuous casting, the thermal stress due to the expansion and contraction of the surface layer portion of the roll for continuous casting can be reduced, and the generation of cracks can be suppressed. However, there is a problem that a phenomenon called "sagging" occurs in which the convex portion between the slits is crushed by the slab, and the cross section of the slab to be manufactured cannot be kept rectangular, resulting in quality deterioration.

Therefore, Patent Document 1 discloses a roll for continuous casting in which the groove depth of the slits in contact with both ends in the width direction of the slab, which causes a problem of sagging, is shallow and the groove pitch is increased.

JP-A-2015-93302

According to the roll for continuous casting described in Patent Document 1, sagging can be prevented and the occurrence of cracks can be appropriately suppressed. However, cracks are still generated in the roll for continuous casting, and it is desired to extend the roll life by further suppressing the generation of cracks.

The present invention has been made in view of such circumstances, and a roll for continuous casting capable of preventing the sagging of the convex portion between the slits, suppressing the occurrence of cracks, and further extending the roll life. The purpose is to provide.

In order to achieve the above object, the present invention is applied to a roll for continuous casting, which is installed in a secondary cooling zone of a continuous casting machine and has a plurality of slits composed of grooves extending in the circumferential direction formed on the surface layer portion.
A non-slit region without a slit is provided on both sides in the width direction of the slab with the slit region in which the plurality of slits are formed, and the end portions in the width direction of the slab come into contact with each other. Let the length in the width direction be WS
The slit Sc formed at the position closest to the center of the slab width direction length WS of the slit region and the slit Se formed at the position farthest from the center of the slab width direction length WS of the slit region. Slits S1, S2, ..., Sm (m is a natural number) are formed in this order from the slit Se toward the slit Sc, and the groove depth of the slit Sc is set to hc and the groove depth of the slit Se is set to hc. Assuming that the groove depths of the slits S1, S2, ..., Sm are h1, h2, ..., And hm, respectively, 0 <he ≦ h1 ≦ h2 ≦… ≦ hm ≦ hc, and the slits S1, S2, ... At least one of Sm has a groove depth of more than he and less than hc.
Each of the slits is characterized in that the radius of radius of the groove bottom is 2 mm to 6 mm, the groove depth is 3 mm to 30 mm, the groove width is 2 mm to 8 mm, and the groove pitch is 10 mm to 30 mm.

In continuous casting of slabs by a continuous casting machine, unevenness due to bulging may occur at the widthwise end portion of the slab. Therefore, if a slit is provided in the roll portion for continuous casting where the end portion in the width direction of the slab is in contact, it causes sagging. In the present invention, a slit is not provided in the continuous casting roll portion where both ends in the width direction of the slab are in contact with each other to prevent sagging.

Further, in the present invention, the stress concentration due to a sudden change in the groove depth is alleviated by gradually reducing the groove depth of the slit from the center to the end in the slab width direction of the slit region. This makes it possible to suppress the occurrence of cracks as compared with the conventional case.

Further, in the continuous casting roll according to the present invention, it is preferable that m is 3 or more and (h1-he) / h1> (h2-h1) / h2> (h3-h2) / h3. ..

By gradually increasing the rate of change in the groove depth of the slit from the center of the slit region in the width direction of the slab toward the end, it is possible to further obtain the effect of suppressing the occurrence of cracks.

In the roll for continuous casting according to the present invention, a non-slit region without a slit is provided on both sides in the width direction of the slab with the slit region in which the slit is formed, in contact with the end portion in the width direction of the slab. By preventing sagging and gradually reducing the groove depth of the slit from the center of the slit region in the width direction to the end, it is possible to further suppress the occurrence of cracks, so the roll can be compared with the conventional one. The life can be extended.

It is a partial cross-sectional view of the roll surface layer part for continuous casting which concerns on 1st Embodiment of this invention. It is a partial cross-sectional view of the roll surface layer part for continuous casting which concerns on the 2nd Embodiment of this invention. It is a partial cross-sectional view of the roll surface layer part for continuous casting which concerns on 3rd Embodiment of this invention. It is a bar graph which compared the roll axial stress generated in the groove bottom of a slit in the prior art and the Example.

Subsequently, an embodiment embodying the present invention will be described with reference to the attached drawings, and the present invention will be understood.

According to the roll for continuous casting described in Patent Document 1, the present inventors can prevent sagging of the convex portion between the slits, but stress concentration occurs at a portion where the groove depth of the slit changes abruptly, and the stress is concerned. It was discovered that concentration causes cracks and growth in continuous casting rolls. That is, it was discovered that stress concentration may occur depending on the arrangement of the slits that suppress the generation of cracks due to thermal stress, and the life extension effect of the slits may be diminished.
Therefore, if the stress concentration at the portion where the groove depth of the slit changes abruptly can be relaxed, early crack generation can be suppressed and the roll life can be further extended.

In the present invention, in a roll for continuous casting, which is installed in the secondary cooling zone of a continuous casting machine and has a plurality of slits consisting of grooves extending in the circumferential direction formed on the surface layer portion, the protrusions between the slits are prevented from sagging. A non-slit region without a slit is provided on both sides in the width direction of the slab with the slit region in which a plurality of slits are formed in contact with each other in the width direction of the slab. That is, if the slab width is W and the length of the slit region in the slab width direction is WS, WS <W.
The roll for continuous casting according to the present invention is axisymmetric with respect to the central axis of the roll for continuous casting in the slab width direction.

Further, in order to alleviate the stress concentration in the portion where the groove depth of the slit changes abruptly, the slit Sc formed at the position closest to the center in the slab width direction of the slit region and the center of the slit region in the slab width direction. Slits S1, S2, ..., Sm (m is a natural number) are sequentially formed from the slit Se toward the slit Sc between the slits Se formed at the farthest positions. Assuming that the groove depth of the slit Sc is hc, the groove depth of the slit Se is he, and the groove depths of the slits S1, S2, ... ... ≤ hm ≤ hc, and at least one of the slits S1, S2, ..., Sm has a groove depth of more than he and less than hc.

However, the following restrictions are set on the dimensions of the slits Se, S1, S2, ..., Sm, Sc.
The radius radius R of the groove bottom is set to 2 mm or more in order to suppress the generation of cracks due to stress concentration, and 6 mm or less in order to avoid a decrease in the rigidity of the entire continuous casting roll.
The groove depth shall be 3 mm or more, which does not restrain expansion and contraction due to temperature changes and can suppress thermal stress, and 30 mm or less in order to prevent damage to the entire continuous casting roll when a crack is formed at the bottom of the groove.
The groove width B is set to 2 mm or more so that the side surfaces of the grooves do not come into contact with each other due to thermal elongation when the slab comes into contact with the continuous casting roll, and the width of the convex portion between the grooves is secured to maintain rigidity. It should be 8 mm or less.
The groove pitch P (distance between the centers of adjacent grooves) is preferably as small as possible in order to relieve the thermal stress on the outer peripheral surface of the convex portion, but is 10 mm in order to secure the width of the convex portion and secure the rigidity of the convex portion. It is set to ~ 30 mm.

Hereinafter, a specific form of the roll for continuous casting according to the present invention will be described.
[Roll for continuous casting according to the first embodiment of the present invention]
FIG. 1 shows a partial cross-sectional view of the surface layer portion of the continuous casting roll 10 according to the present embodiment.
In the continuous casting roll 10, the length WS in the width direction of the slab of the slit region is set to <W the width of the slab, and the slits in which the end portions in the width direction of the slab come into contact with both sides in the width direction of the slab across the slit region. There is no non-slit area.

The groove depth from the slit Sc formed at the position closest to the center 13 in the slab width direction of the slit region to the slit S2 is hc, and is formed at the position farthest from the center 13 in the slab width direction of the slit region. A slit S1 having a groove depth of more than he and less than hc is formed between the slit Se and the slit S2. That is, the groove depths of the slits formed at both ends in the slab width direction of the slit region gradually become shallower from the center side in the slab width direction to the end side of the slit region.
The radius radius R, the groove width B, and the groove pitch P of the groove bottom of each slit are constant.

[Roll for continuous casting according to the second embodiment of the present invention]
FIG. 2 shows a partial cross-sectional view of the surface layer portion of the continuous casting roll 11 according to the present embodiment.
The continuous casting roll 11 is different from the continuous casting roll 10 in that the groove bottom of the slit S1 is on a straight line connecting the groove bottom of the slit S2 and the groove bottom of the slit Se. That is, the rate of change in groove depth from the slit S2 to the slit Se is constant, (h1-he) / h1 = (h2-h1) / h2.

[Roll for continuous casting according to the third embodiment of the present invention]
FIG. 3 shows a partial cross-sectional view of the surface layer portion of the continuous casting roll 12 according to the present embodiment.
In the continuous casting roll 12, the groove depth change rate at the end in the width direction of the slab in the slit region is not constant, and the groove depth change rate from the slit S4 to the slit Se gradually increases as it approaches the slit Se. Is different from the continuous casting roll 11. (H1-he) / h1> (h2-h1) / h2> (h3-h2) / h3> (h4-h3) / h4, and the groove bottom of the slits S4, S3, S2, S1 and Se has a radius. It is on the curve obtained by inscribed two arcs with R1 = hc × 0.75 and radius R2 = R1 × 16.
The groove depth from the slit Sc to the slit S4 formed at the position closest to the center 13 in the slab width direction of the slit region is constant at hc.

Although the embodiments of the present invention have been described above, the present invention is not limited to the configuration described in the above-described embodiments, and is considered within the scope of the matters described in the claims. It also includes other embodiments and variations thereof. Further, various changes and combinations of the above-described embodiments may be made as long as they do not deviate from the gist of the present invention.
For example, in the above embodiment, the groove depths of the slits S4 to S1 are gradually changed, but the groove depths of the slits Sm to S1 (m is a natural number of 5 or more) may be gradually changed. Alternatively, a region having the same groove depth, that is, a so-called landing, may be provided in the middle of the region where the groove depth is gradually changed. In short, it is sufficient that the groove depth of the slit is not changed suddenly.

A simulation test carried out to verify the effect of the present invention will be described.

The elasto-plastic stress analysis of the roll for continuous casting was performed using the finite element method.
[Analysis model]
-Roll dimensions for continuous casting: diameter 380 mm, body length 2300 mm, distance between bearings 2600 mm
・ Slit dimensions: groove bottom radius radius 3 mm, groove width 6 mm, groove pitch 15 mm
-Length in the width direction of the slab in the slit area: 645 mm
・ Shard width: 1144 mm

The following four cases were set for the groove depth of the slit.
-In the conventional example 1, the groove depth of all the slits is uniformly set to 20 mm.
-In the conventional example 2, he: 5 mm, h1 to h19, hc: 20 mm.
Example 1 is the first embodiment described above, with he: 5 mm, h1: 10 mm, h2 to h19, and hc: 20 mm.
Example 2 is the third embodiment described above, with he: 5 mm, h1: 15.5 mm, h2: 18 mm, h3: 19.2 mm, h4 to h19, and hc: 20 mm.

[Load conditions per continuous casting roll]
-Load load: Straightening reaction force 735.5 kN, molten steel static pressure 430 kN
-Heat load: slab surface temperature 1138K, cooling water temperature 313K

A bar graph of the simulation results is shown in FIG. This bar graph compares the roll axial stress generated at the bottom of the groove of the slit between the conventional example and the embodiment. The roll axial stresses of h5 to h19 are omitted.
The following shows what was found from the simulation test.

The maximum value of the roll axial stress is as large as about 770 MPa in the conventional example 1 and about 750 MPa in the conventional example 2, whereas in the first embodiment, the maximum value of the roll axial stress can be reduced to about 670 MPa. .. When the roll for continuous casting of Example 1 was used in an actual machine (slab width is 1100 mm to 1900 mm, cooling water temperature is 20 to 45 ° C., other conditions are the same as the analysis model conditions), the roll life is the same as that of Conventional Example 1. It became about 1.5 times.

In Example 1, the maximum value of the roll axial stress is reduced by about 10% (decrease from 770 MPa to 670 MPa) as compared with the conventional example 1, whereas the roll life is significantly increased by 50%. The reason for this is thought to be as follows.
Forming a slit in the surface layer of a continuous casting roll is effective in extending the life of the roll because the expansion and contraction of the surface layer of the roll can be alleviated. The mitigation effect is diminished. After colliding with the slab, the cooling water in the continuous casting machine flows toward the end side in the width direction of the slab. Therefore, a product in the casting machine such as a scale invades the slit on the end side in the width direction of the slab.
In the first embodiment, the stress concentration portion is on the center side (for example, the portion of the slit groove depth h2) from the end portion in the slab width direction (the portion of the slit groove depth he). That is, in the first embodiment, the portion where the relaxation effect due to scale intrusion is less diminished (for example, the portion where the groove depth h2 of the slit is small) is the stress concentration portion. As a result, it is considered that the life extension effect is further exhibited and the life extension result of 1.5 times is obtained.

In Example 2, the maximum value of the roll axial stress is about 540 MPa (slit groove depth h1 portion) and 535 MPa (slit groove depth h2 portion), and no remarkable stress peak is observed.
In the second embodiment, the roll axial stress is reduced to about 70% as compared with the conventional example 1 (30% reduction). Therefore, it can be expected that the roll life will be extended by about 2.5 times that of the conventional example 1.

10, 11, 12: Roll for continuous casting, 13: Center in slab width direction, Se, S1, S2, S3, S4, Sc: Slit, R: R radius, he, h1, h2, h3, h4, hc: Groove depth, B: Groove width, P: Groove pitch, W: Slab width, WS: Slit region length in the slab width direction

Claims (2)

In a continuous casting roll installed in the secondary cooling zone of a continuous casting machine and having a plurality of slits consisting of grooves extending in the circumferential direction formed on the surface layer portion.
A non-slit region without a slit is provided on both sides in the width direction of the slab with the slit region in which the plurality of slits are formed, and the end portions in the width direction of the slab come into contact with each other. Let the length in the width direction be WS
The slit Sc formed at the position closest to the center of the slab width direction length WS of the slit region and the slit Se formed at the position farthest from the center of the slab width direction length WS of the slit region. Slits S1, S2, ..., Sm (m is a natural number) are formed in this order from the slit Se toward the slit Sc, and the groove depth of the slit Sc is set to hc and the groove depth of the slit Se is set to hc. Assuming that the groove depths of the slits S1, S2, ..., Sm are h1, h2, ..., And hm, respectively, 0 <he ≦ h1 ≦ h2 ≦… ≦ hm ≦ hc, and the slits S1, S2, ... At least one of Sm has a groove depth of more than he and less than hc.
Each of the slits is a roll for continuous casting, characterized in that the radius of radius of the groove bottom is 2 mm to 6 mm, the groove depth is 3 mm to 30 mm, the groove width is 2 mm to 8 mm, and the groove pitch is 10 mm to 30 mm. In the continuous casting roll according to claim 1, the m is 3 or more, and is (h1-he) / h1> (h2-h1) / h2> (h3-h2) / h3. Roll for casting.

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