JPH09253810A - Roll for carrying in continuous casting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the service life of a roll and further, reduce the maintenance cost of the roll by efficiently cooling to restrain the temp. raising of the roll. SOLUTION: In the roll 1 for carrying insertedly fitting a sleeve 3 to a roll core part 2, a material excellent in the structural strength to the roll core part 2 and a material layer excellent in wear resistance and corrosion resistance to the sleeve 3, are used, and a material having different thermal conductivity is inserted or applied to coat on the fitting surface between the sleeve 3 and the roll core part 2 to form a heat conductive control layer 4. Choking flowing water passage-like cooling water passages 5 are arranged as axially symmetrical state near the surface layer of the roll core part 2, and slitting recessed parts are arranged on the outer surface of the sleeve 3. By this constitution, the development of crack on the sleeve is restrained and even in the case of developing of the cracking, the propagation of the cracking to the core part is prevented to prevent the breakage of the roll. The wear and the corrosion on the roll surface are prevented to extend the service life of the roll, and the deformation and the fall-out of the sleeve are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
In addition, the present invention relates to a transfer roll of a continuous casting device used in a corrosive environment.

[0002]

2. Description of the Related Art In a continuous casting machine, high temperature slabs and the like are continuously drawn from a mold immediately below a tundish, and are conveyed while cooling along a line, such as pinch rolls and guide rolls. The heating by contact with the slab and the cooling by cooling water or cooling are repeated.

The cause of the deterioration of the rolls used in continuous casting and the like is due to wear and cracks due to thermal stress. Conventionally, as a material that withstands this thermal stress, the roll main body surface is It has been used that the surface of which is heat-resistant, wear-resistant, and oxidation-resistant is improved by coating with a cladding layer made of a stainless steel alloy material.

With respect to the progress of cracks and corrosive wear on the roll surface due to repeated heating and cooling and thermal stress, control limits for crack length and wear amount are set, periodic inspections, etc. are carried out, and rolls exceeding the limit values are reached. For, regarding the replacement of rolls and weld overlay repair.

Further, as one of the important causes of the generation of cracks on the roll surface, there is the generation of excessive thermal stress on the roll surface which occurs when the continuous casting machine operates at an extremely low speed or when the casting is completely stopped. This is because the continuous casting machine must be operated at an extremely low speed or the casting machine must be completely stopped due to replacement of the tundish nozzle or tundish, or breakout of the slab during casting. This is because the roll surface in contact with the slab at this time is subjected to excessive temperature rise and thermal stress.

[0006]

To solve these problems, as conventional examples, JP-A-57-89462 and JP-A-5-89462 are cited.
Cr-based weld overlays disclosed in JP-A-4-69522,
There is a method of hardening the roll surface by heat treatment or the like, but these techniques have an effect of abrasion resistance but insufficient crack resistance, and in reality, thermal cracks occur.

Japanese Patent Laid-Open Nos. 55-68160 and 6
In the technique disclosed in JP-A-2-244559, a sleeve is fitted on the roll surface to improve maintainability and prevent crack growth. However, the temperature of the sleeve rises as a whole, and the slab contacts with the center of the roll. The sleeve could not freely expand and contract in the axial direction due to the thermal expansion due to the temperature difference between the ends, and the sleeve bulged out.

Japanese Unexamined Patent Publication (Kokai) No. 58-20938 discloses a technique for preventing the sleeve from bulging out due to central welding, but the thermal stress generated is large and cracks occur at the welded portion, which causes the roll core portion. Progressed, there was no effect of fitting the sleeve.

JP-A-55-81050 and JP-A-5-
Japanese Patent Laid-Open No. 8-93549 discloses a technique for preventing the sleeve from bulging out by ensuring the degree of freedom of thermal expansion of the sleeve, but the temperature rise of the sleeve cannot be suppressed, and the sleeve can be prevented from slipping out and idling. There wasn't.

Further, the above-mentioned JP-A-55-81050,
The technique disclosed in Japanese Patent Application Laid-Open No. 58-93549 is intended to further reduce the heat load by the surface concave groove and improve the cooling efficiency by improving the sleeve fitting adhesion, but the effect of suppressing the temperature rise of the sleeve is not provided. It was insufficient.

Further, in the techniques disclosed in JP-A-4-251644 and JP-A-56-99060, a cooling water passage is secured near the surface layer of the roll to enhance cooling, but the roll surface temperature decreases. However, on the contrary, the temperature gradient with the inside of the roll becomes large, the occurrence of thermal cracks cannot be completely prevented, and water leakage easily occurs when the cracks propagate because the water channel is close to the roll surface. In the latter case, the structure of the cooling pipe is complicated, the manufacturing cost is high, and high-pressure water is used. Therefore, it is difficult to apply it to the actual machine.

In addition, when the continuous casting machine operates at an ultra-low speed or when the casting is completely stopped, a severer heat load than that during normal operation causes a large thermal stress on the roll surface, resulting in cracks on the roll surface. On the other hand, there is no effective measure for reducing the heat load and thermal stress on the contact surface between the slab and the roll, and the roll life is extremely short.

In view of the above-mentioned problems, the present invention provides a transfer roll for a continuous casting apparatus, in which the temperature rise of the roll is suppressed by efficient cooling, the life of the roll is extended, and the maintenance cost of the roll is reduced. .

[0014]

According to the present invention, in a transport roll of a continuous casting apparatus in which a sleeve is fitted in a roll core, a plurality of closed cooling water channels are provided near the surface layer of the roll core. It is a roll for conveyance of a continuous casting device characterized by the above.

In the above-mentioned carrying roll, the sleeve is provided with a material layer having excellent wear resistance and corrosion resistance, and the roll core is made of a material having excellent structural strength.

Further, in each of the above-mentioned carrier rolls, a material having different thermal conductivity is inserted or coated on the fitting surfaces of the sleeve and the roll core to form a heat conduction control layer. is there.

In each of the above-mentioned carrying rolls, the carrying roll of the continuous casting apparatus is provided with a groove-shaped recess on the outer surface of the sleeve.

The dimension of the sleeve is generally a cylindrical body having an outer diameter of about 500 mm × length of 2000 mm × thickness of about 20 mm, and the required material layer having excellent wear resistance and corrosion resistance is Ni. -Cr stainless steel, Cr-based stainless steel, or Ni-Cr, Cr-based stainless build-up on the surface, Ni-based, Co-based self-fluxing alloy sprayed.

Materials for the roll core having excellent structural strength include Ni-Cr steel, Ni-Cr-Mo steel and Cr-Mo.
Steel and cast forged steel may be mentioned.

As a material for forming the heat conduction control layer, alumina type, zirconia type, sialon thermal spraying, C
Examples include r-plating, Ni-plating, glass-based, and SiO ₂ -based fiber sheets, which are formed to have a thickness of 0.1 to 1.0 mm.

The groove-shaped recess provided on the outer surface of the sleeve is
It is a recess provided with a required width, depth and pitch in the roll axis direction. The groove-shaped recess can be provided continuously or intermittently in the circumferential direction of the sleeve. Moreover, it is preferable that the concave portion has a curvature.

With this structure, cracks generated in the sleeve on the surface of the roll are prevented from propagating to the core of the roll, breakage of the roll is prevented, and the life of the roll is extended. The sleeve is prevented from being deformed or slipped out, and even if a crack is generated in the sleeve, the crack is not transmitted to the roll core portion, and further water leakage of the cooling water is prevented. Prevents wear and corrosion on the roll surface,
Prevents wear and tear and maintains a predetermined roll diameter to extend roll life. The excessive cooling of the roll surface layer is suppressed, the rapid decrease of the temperature of the conveyed slab is suppressed, and the quality is maintained.

Further, by providing groove-shaped recesses on the outer surface of the sleeve, it is possible to reduce the excessive heat load that the roll receives at the contact surface with the slab during ultra-low speed casting or when the casting is completely stopped. By reducing the contact area with the roll, the amount of heat transferred from the slab to the roll is reduced, and the thermal expansion of the roll at the convex portion, which is the contact portion between the slab and the roll, is facilitated.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a conveying roll of a continuous casting apparatus according to the present invention will be described with reference to FIG.

This transport roll 1 uses the above-mentioned material as a material layer also having excellent wear resistance and corrosion resistance in the roll core portion 2 which uses the above-mentioned material as a material having excellent structural strength. A sleeve 3 is fitted in the sleeve 3, and if necessary, the above-mentioned materials having different thermal conductivities are inserted into the fitting surfaces of the roll core 2 and the sleeve 3 as the heat conduction control layer 4, or these materials are inserted. To coat.

The roll core 2 is provided with a plurality of closed flow channels 5 for cooling the roll near the surface of the roll core 2. Each of the water channels 5a and the drain channel 5b is provided vertically through the main shaft. Connected.

Here, the sleeve has an outer diameter of about 500 m.
m × length 2000 mm × thickness 20 mm cylindrical body,
As a material layer having excellent abrasion resistance and corrosion resistance, Ni-Cr stainless steel, Cr-based stainless steel, or Ni-Cr Cr-based stainless overlay, N
The i-type and Co-type self-fluxing alloys may be sprayed.

The size of the roll used to convey the high temperature material for continuous casting has a diameter of 250 to 500 mmφ,
The roll width is about 1800 to 2200 mm, and the cooling holes 5 provided in the axial direction inside the roll 1 are 25
It is suitable to provide 4 to 10 revolver type cooling holes of ˜35 mmφ in axial symmetry.

With the above-mentioned structure, thermal cracks are generated on the sleeve surface due to, for example, contact of the high temperature slab with the rolls and cooling, and repeated cracking stresses applied to the rolls during conveyance of the slabs cause cracks in the deep part of the sleeve. Even if it may enter, since there is a structurally discontinuous heat conduction control layer between the sleeve and the roll core, cracks do not propagate to the roll core even if they penetrate the sleeve, Therefore, roll breakage due to cracks can be prevented, and the cooling water passage is provided as a closed flow passage in the core of the roll, so that the water passage is not damaged and leaks.

Next, the temperature of the roll core and the sleeve is effectively lowered by the effect of a plurality of cooling water passages arranged axially symmetrically on the roll core, and swelling due to expansion due to temperature rise of the sleeve, slipping out, idling, etc. Prevents accidents, maintains the strength of the entire roll, and prevents bending and breakage of the roll.

Conventionally, the material of the roll surface had to have a plurality of characteristics of crack resistance, abrasion resistance and corrosion resistance, but the present invention uses a discontinuous heat conduction control layer for crack propagation. It is structurally prevented, and the sleeve material has high corrosion resistance,
Since it is possible to focus on materials with high wear resistance, the life due to wear and corrosion is also improved.

The temperature of the sleeve surface can be controlled while maintaining the strength of the entire roll by inserting a material for controlling the amount of cooling water and heat transfer to the inner surface of the sleeve and the surface of the roll core, or by coating such as thermal spraying or plating.

Considering the optimum arrangement of the cooling holes as the transport roll, the cooling capacity (A) by the cooling holes and the surface cooling area (B) of the roll including the sleeve are shown in the following [Equation 1]. ] And [Equation 2] are used for the calculation.

[0034]

## EQU1 ## A = n × a ₀ × v _S × K where a ₀ : area of one cooling hole (mm ² ) n: number of cooling holes v _S : flow rate of cooling water (0.1-0. 3 m / s) K: heat transfer coefficient

[0035]

[Number 2] ^{B = π (D 2 -d 2} ) where D: Roll diameter d: the center diameter of the cooling holes are arranged axisymmetrically

Therefore, in order to sufficiently cool the sleeve to 300 to 200 ° C. or less, the constant value (v _S , K) is removed from the value of A / B obtained from the equation (3) (equation 4).
It is necessary to determine n, a ₀ , and d ² so that the value of the surface cooling effect coefficient (C) shown by the formula is 1/100 or more.

[0037]

(Equation 3)

[0038]

(Equation 4)

Here, further consideration will be given to the equation (4).

[0040]

D ² ≧ D ² − (100 / π) n × a ₀

On the other hand, to arrange the cooling holes in the roll core,
Since the condition of d ≦ D−2t (t is the thickness of the sleeve) must be satisfied, the range of the center diameter “d” of the cooling hole is expressed by the formula [6].

[0042]

(Equation 6)

2 (a), (b), (c), and (d) show a transport roll in which a groove-shaped recess 6 is provided on the outer surface of the sleeve of the transport roll having the roll core shown in FIG. It is the side view which showed the example. In FIG. 2A, the groove-shaped recess 6 is provided in the sleeve 3
2B is an example in which the groove-shaped concave portions 6 are intermittently provided in the circumferential direction of the sleeve 3. In these examples, the groove-shaped recesses are not continuous in the axial direction of the roll, but as shown in FIGS. 2 (c) and 2 (d), the groove-shaped recesses are continuous in the axial direction of the roll. That is, they may be arranged in a spiral shape.

FIG. 2 (e) is an enlarged sectional view showing the groove-shaped recess. In providing the groove-shaped recess 6, the groove-shaped recess 6 is set to 40 to 60% of the contact area between the slab and the sleeve 3 so that the sleeve 3 can stably support the slab. To do. Also, the depth of the recess h
Is preferably 3 mm or more in consideration of wear of the sleeve surface. Further, the pitch P and the width B of the recess are P =
It is desirable to set B / (0.4 to 0.6) based on the above area ratio. Further, it is preferable that the concave portion has a curvature R in order to avoid concentration of stress on the concave portion. Therefore, R ≧ B = (0.4 to 0.6) P
It is desirable to select the width B, the pitch P, and the height h so that >> h.

[0045]

EXAMPLE As Example 1, n = 8, a ₀ = (π / 4)
When x25 ² , D = 360, and d = 275, the surface cooling effect coefficient (C value) according to the equation [4] is 0.02.
3, the cooling capacity is judged to be sufficient.

As a second embodiment, n = 10 and a ₀ = (π /
4) When x35 ² , D = 400 and d = 300,
The surface cooling effect coefficient (C value) according to [Equation 4] is 0.04.
The cooling capacity is 3 and it is similarly judged that the cooling capacity is sufficient.

As a third embodiment, a transport roll having a groove 6 as shown in FIG. 2A on the outer surface of the sleeve of the transport roll having the roll core shown in FIG.
The heat load on the sleeve surface was analyzed. The groove-shaped recesses provided on the surface of the sleeve are as follows. Pitch P =
When the thermal stress of this sleeve was calculated with 80 mm, width B = 40 mm, depth h = 3 mm, and radius of curvature R = 68.2 mm of the recess, it was found that the thermal stress was about 10% lower than that of a normal sleeve having no groove-shaped recess. It was found that it was alleviated by 10%.

[0048]

As described above, the transport roll of the present invention has a roll core by arranging cooling water channels in the form of closed flow channels in the axially symmetrical manner near the surface layer of the roll core and by providing a heat conduction control layer. Parts and sleeves are cooled appropriately, and excessive cooling of the roll surface layer is suppressed to prevent a sharp drop in the temperature of the conveyed slab, while maintaining the quality of the slab and preventing the sleeve from deforming or coming off. The groove-shaped recess provided on the outer surface suppresses the occurrence of cracks at the contact surface with the slab, and even if cracks occur in the sleeve, they do not propagate to the roll core, thus affecting the cooling water channel. It will not cause water leakage. Further, it is possible to prevent wear and corrosion of the roll surface, suppress wear and maintain a predetermined roll diameter, and reduce maintenance cost and extend roll life.

[Brief description of drawings]

FIG. 1 shows an example of the form of a transport roll of a continuous casting apparatus according to the present invention. FIG. 1 (a) is a longitudinal sectional view of the roll and FIG. 1 (b) is a transverse sectional view of the roll.

2A and 2B show another example of the form of a transfer roll of the continuous casting apparatus of the present invention, in which FIGS. It is a figure which shows a shape.

[Explanation of symbols]

 1 Transport Roll 2 Roll Core Part 3 Sleeve 4 Heat Conduction Control Layer 5 Cooling Water Channel 5a Water Supply Channel 5b Drain Channel 6 Groove-shaped Recess

Claims (4)

[Claims] 1. A continuous casting apparatus having a plurality of cooling water passages in the form of closed flowing water passages provided in the vicinity of the surface layer of the roll core in a transport roll of a continuous casting apparatus having a sleeve fitted to the roll core. Transport roll. 2. The transfer roll of a continuous casting apparatus according to claim 1, wherein the sleeve is provided with a material layer having excellent wear resistance and corrosion resistance, and the roll core is made of a material having excellent structural strength. 3. The continuous casting apparatus according to claim 1, wherein a heat conduction control layer is formed by inserting or coating materials having different thermal conductivities on the fitting surfaces of the sleeve and the roll core. Transport roll. 4. The transfer roll for a continuous casting apparatus according to claim 1, 2 or 3, wherein a groove-shaped recess is provided on the outer surface of the sleeve.