JPH0428766B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a heat-resistant roll used for charging, moving, and unloading materials to be heated, such as steel plates, in heating furnaces, heat treatment furnaces, and the like.

(Prior art) A heating furnace or a heat treatment furnace, for example, a reduction furnace for reduction treatment performed prior to hot-dip galvanizing, a continuous annealing furnace for electrical steel sheets, an annealing and pickling furnace for stainless steel sheets, etc. Rolls for use, movement within the furnace, or export (hereinafter simply referred to as "transfer" or "transfer") are generally kept at a temperature of 500 to 1300℃.
Rolls with heat resistance are used because they are exposed to a heated atmosphere. Hereinafter, this will be referred to as a heat-resistant roll.

Conventionally, heat-resistant rolls are made of Ni-Cr or Co-
Support rolls made of heat-resistant alloys such as Cr-based ones, or those with ceramic materials such as alumina or zirconia sprayed on the outer peripheral surface of the support rolls have been used. In the case of heat-resistant steel rolls, there is a problem in that deposits from the material to be heated are fused and deposited on the surface of the roll during use (this is called build-up), and this causes indentation scratches on the surface of the material to be heated. Products sprayed with ceramic materials do not have such problems, but peeling of the sprayed layer is observed and the service life is 2 to 30 minutes.
Not only is it a short period of three months, but once the sprayed layer peels off, foreign matter can adhere to the exposed surface, causing indentation defects and other problems.

In recent years, in order to solve the above-mentioned problems, ceramic sleeves (hereinafter simply referred to as ceramic sleeves) manufactured by molding and sintering ceramic materials have been attached and fixed to support rolls with keys, pins, etc. A heat-resistant roll has been proposed in which the support roll and the sleeve are integrally configured to orbitally rotate (that is, rotation in which the peripheral speed of the roll and the conveyance speed of the material to be heated are synchronized). Many ceramic materials have been proposed, including alumina, silicon carbide, and silica.

However, although it has already been more than 10 years since such ceramic sleeves were first proposed, cracks and peeling have been observed due to the lack of mechanical strength of the ceramic material and the difference in thermal expansion coefficient with the metal roll body. However, it has drawbacks such as being susceptible to heat shock and has not yet been put into practical use. That is, in the heat-resistant roll described above in which a ceramic sleeve is integrally fitted onto the support roll, axial deflection occurs due to the difference in thermal expansion between the support roll and the sleeve, and the sleeve is made of a material such as ceramic that is easily broken. As a result, the sleeve is damaged and becomes unusable. In addition, if a ceramic sleeve is fitted onto the support roll and fixed with keys, pins, etc., cracks may occur near the key hole and pin hole due to the impact during rotation, and the sleeve may be damaged. Put it away.

For example, Japanese Patent Publication No. 55-51007 discloses a heat-resistant roll comprising a support roll and a porous sleeve of fused silica formed on the outer peripheral surface of the support roll. However, the support roll and sleeve are integrally connected via a keyway so that they operate as one unit. Therefore, cracks are inevitably generated from the key groove portion, and despite the many advantages of fused silica sleeves in addition to the advantages of ceramic sleeves, they have not yet been put into practical use.

On the other hand, in the case of Special Publication No. 55-48086, similarly,
A heat-resistant roll composed of a support roll and a ceramic sleeve externally fitted and fixed to the support roll is disclosed, but this is a sintered body of powder with an average particle size of 5 to 10 μm, so-called fine ceramic. The ceramic sleeve is divided into multiple parts in the direction of the roll axis and a clear lath is provided at the end to cope with thermal expansion. This is also absorbed by providing a constant clearance along the entire circumference between the support roll and the sleeve. In particular, in order to absorb thermal deformation or deflection in the radial direction of the support roll, it is essential to provide a certain clearance as described above also on the upper surface of the roll.

However, such a configuration is difficult to realize in practice, resulting in the adoption of an unnecessarily complicated structure, which is also not practical.

(Summary of the Invention) An object of the present invention is to provide a heat-resistant roll that can be put to practical use by eliminating the above-mentioned drawbacks of ceramic sleeves.

Another object of the present invention is to provide a heat-resistant roll that, despite its extremely simple structure, can exhibit superior performance compared to any conventional roll.

Still another object of the present invention is to provide a heat-resistant roll that is particularly suitable as a transfer roll in a reduction furnace for reduction treatment performed prior to hot-dip galvanizing, a continuous annealing furnace for electrical steel sheets, etc., or an annealing and pickling furnace for stainless steel sheets. It is to be.

In all of the several products proposed so far, the support roll and the ceramic sleeve are integrally configured by locking them together with a key or a pin. When it is stopped, the vicinity of the key hole is damaged during rotation, and when it is pinned, cracks in the pin hole become noticeable, so in many cases it becomes unusable within a few days. After conducting various experiments focusing on these points, we found that it was extremely difficult to solve the problem.In fact, we found that the rotational force could be sufficiently transmitted from the support roll to the ceramic sleeve without providing such a fixing means. As we continued our research and development thinking that there must be a way to obtain this, we discovered that it was sufficient to loosely fit a ceramic sleeve onto the support roll, which is completely contrary to conventional technical common sense, and we developed the present invention. It was completed. Here, ``play fit'' refers to fitting with so-called play (clearance), that is, fitting loosely.

As mentioned above, ceramic materials do not have sufficient mechanical strength, so if they are loosely fitted, they are not only expected to cause breakage, but also because they are simply loosely fitted.
It was predicted that the rotational force of the support roll would not be transmitted to the ceramic sleeve by simply doing so, or even if it were transmitted, it would not be transmitted smoothly as rotation of the ceramic sleeve without slipping. .

However, it has been found that according to the present invention, excellent results can be obtained which are completely contrary to such expectations.

That is, the present invention provides a heat-resistant roll comprising a support roll and a ceramic sleeve externally fitted on the support roll, wherein even when the support roll exhibits maximum thermal expansion in the axial and radial directions, the ceramic sleeve remains This is a heat-resistant roll characterized in that it is configured such that it is installed in a loosely fitted manner.

In the present invention, in order to smoothly transmit the rotational force of the rotating support roll to the outer ceramic sleeve, at least one of the contact surfaces between the two, for example, the inner circumferential surface of the ceramic sleeve, is finished to an appropriate roughness. At that time, it is sufficient that the surface roughness is Rmax≧25 μm. More preferably, both contact surfaces, that is, the inner circumferential surface of the sleeve and the outer circumferential surface of the support roll, are finished to the above-mentioned surface roughness.

Regarding this point, the idea of transmitting the rotational force of the roll to the sleeve by the frictional force between the ceramic sleeve and the roll has been proposed in the past, but this alone would cause the inner surface of the sleeve to wear out immediately. Transmission of rotational force becomes impossible. However, according to the present invention, unexpectedly, by significantly increasing the surface roughness, surface wear is no longer observed, and rotational force transmission can be ensured over a long period of time.

Generally, the material of the ceramic sleeve is not limited, but in consideration of its use in the heating furnace and heat treatment furnace as described above, it is preferable that the ceramic sleeve is made of fused silica.

Note that the ceramic sleeve is manufactured by appropriately molding and sintering ceramic powder. For example, when it is made of fused silica, an appropriate binder is added to fused silica powder, molded, and sintered.

In the present invention, as a result of loosely fitting the sleeve to the outside of the support roll, there is always a certain clearance (gap) between the two, and this clearance absorbs the amount of thermal expansion of the support roll. However, the bending stress δ (Kgf/mm ² ) applied to the support roll at that time and the average clearance (distance between the outer peripheral surface of the support roll and the inner peripheral surface of the sleeve when the support roll is placed at the center of the outer sleeve) , hereinafter the same) α preferably satisfies α≧1 and δ≦4.0. More preferably, the above bending stress (δ)
And the average clearance (α) is set to satisfy the formula: α≧0.2δ ² +1.

Here, the bending stress δ is the own weight of the support roll,
The amount is determined by the weight of the sleeve, the weight of the material to be heated (steel plate), the diameter of the support roll, etc., and can be obtained from the following formula: Bending stress δ=Mmax/Z Mmax=l ₁ / 2 (w ₁ l ₁ /2 + w ₂ l ₂ /2 + w ₃ l ₃ /2) Z = π / 32 [(d _p1 ⁴ − d _i1 ⁴ ) / d _p1 ] However, w ₁ , w ₂ and w ₃ are each The weight of the support roll, the weight of the sleeve, and the weight of the steel plate are each calculated using the following formula.

w ₁ (Kgf/mm) = π/4 (d _p1 ² − d _i1 ² ) r ₁ w ₂ (Kgf/mm) = π/4 (d _p2 ² − d _i2 ² ) r ₂ w ₃ (Kgf/mm )=s×r ₃ ×t l ₁ : Distance between roll bearings l ₂ : Sleeve length l ₃ : Steel plate width d _p1 : Support roll outer diameter d _i1 : Support roll inner diameter (if hollow) d _p2 : Sleeve outer diameter d _i2 : Sleeve inner diameter r ₁ : Support roll specific gravity r ₂ : Sleeve specific gravity r ₃ : Steel plate specific gravity t: Steel plate thickness s: Roll span Thus, according to the present invention, the ceramic sleeve is moved in the axial and radial directions of the support roll. By fitting the support roll loosely so as to absorb the thermal expansion of the support roll, the deflection during use of the support roll and the difference in thermal expansion between the two can be absorbed into the gap between the two. Even in such cases, since no means for fixing the sleeve is used, problems such as breakage or cracking of the sleeve from the location where such a fixing means is provided do not occur.

Furthermore, according to the present invention, by configuring the support roll to be forcibly driven and orbitally rotated in accordance with the line speed, the rotation of the support roll is followed by the frictional force between the outer peripheral surface of the support roll and the inner peripheral surface of the sleeve. On the other hand, if the support roll is not forcibly driven, the entire heat-resistant roll including the support roll is rotated by the transferred material, preventing scratches on the strip surface. do. In addition, when rapidly accelerating or decelerating a steel plate, that is, the material to be heated, or suddenly stopping a support roll, etc., since the sleeve is loosely fitted, misalignment (sliding) occurs between the sleeve itself and the roll shaft body, and the sleeve directly No impact force that would cause breakage is transmitted to the product, and no cracks will occur.

(Aspects of the Invention) Next, the specific structure of the heat-resistant roll according to the present invention will be further explained with reference to the accompanying drawings.

FIG. 1 is a side view schematically explaining the case where the heat-resistant roll according to the present invention is applied to a hearth roller heating furnace, FIG. 2 is a partially enlarged view of the heat-resistant roll, and FIG.
The figure is a cutaway view taken along the - line in Figure 2 and the 4th line.
The figure is a graph showing the relationship between the bending stress of the support roll and the average clearance.

In addition, in the drawings, the same reference numerals indicate the same members.

In the figure, the hearth roller heating furnace 1 includes a chain,
A series of heat resistant rolls 3 are provided which can be orbitally rotated by a suitable drive mechanism 2 such as a sprocket. According to the present invention, the heat resistant roll 3
The support roll 4 is forcibly driven in accordance with the line speed, and the heat-resistant ceramic sleeve 6 is loosely fitted around the outer peripheral surface of the body 5 of the support roll 4.

The material to be heated (not shown) placed on the heat-resistant roll 3 is transferred over the ceramic sleeve 6 which rotates following the rotation of the support roll 4.

Completely different from the conventional method, in the present invention, the rotational force of the support roll 4 is transmitted by the frictional force with the ceramic sleeve 6, and is not transmitted through a pin or key as in the conventional method. Therefore, there is no problem of damage or cracking in that part. At this time, the surface roughness of at least one of both contact surfaces shall be Rmax 25 μm or more. In this way, by appropriately adjusting the surface roughness of the outer surface of the body 5 of the support roll 4 or the surface roughness of the inner surface of the sleeve 6, or by adjusting the weight of the sleeve, a sufficient frictional force can be generated. orbital rotation becomes possible. Therefore, there is no breakage of the sleeve due to impact during driving, which occurs when the sleeve is driven via a key, pin, etc.

In the present invention, the surface roughness of the inner surface of the ceramic sleeve 6 as described above may be adjusted by, for example, selecting the roughness of the raw material powder and/or roughening the surface of the mold in advance. Rmax
≧25 μm is a considerable surface roughness, and even with ceramics, such a rough surface cannot be achieved through normal manufacturing processes.

Furthermore, according to the present invention, an outer circumferential clearance 7 is provided between the support roll 4 and the ceramic sleeve 6, which prevents thermal expansion of the support roll in the radial direction and axial deflection of the support roll due to the thermal expansion of the support roll. Absorb. On the other hand, in the axial direction of the support roll 4, as shown in FIG. The range of movement of this ceramic sleeve in the axial direction can be set appropriately. The size of this annular clearance is necessary and sufficient to absorb axial thermal expansion when the support roll 4 is used.

Here, the average value of the outer circumferential clearance 7 in the radial direction, that is, the average clearance, is generally calculated by adding 1 as a margin in addition to the thermal expansion and deflection that can be obtained by calculation.
The same applies to the annular clearance 8 in the longitudinal direction. However, the annular clearance 8 can always be adjusted by appropriately changing the setting position of the stopper 9 mentioned above.

Figure 4 shows the bending stress (due to the weight of the support roll and sleeve) that the support roll receives during use, that is, at the furnace temperature under a constant load, using the heat-resistant roll according to the present invention shown in Figures 1 to 3. ) and the above-mentioned average clearance. These are the results when the heat-resistant rolls in the furnace were inspected every month under continuous use conditions, and the black circles in the figure indicate the first month's inspection. At times, the sleeves showed breakage, and the white circles indicate those that did not show any cracking even after 1 year and 6 months. The half-black circles indicate those for which breakage was first observed at the 6th month inspection. The area indicated by the hatched line is a more preferable safe area.

Compared to conventional ceramic sleeves that became unusable after a few days, the fact that they can be used continuously for even a month is a major improvement over conventional ceramic sleeves.
Furthermore, the fact that no cracking was observed even after 1 year and 6 months is a great practical benefit.

The roll material and other materials used at this time were as follows.

Ceramic sleeve: Material: Fused silica sintered body ( _SiO2 : 99.7%,
Al ₂ O ₃ : 0.05%) Thickness: 50mm Inner diameter: 200mm Outer diameter: 300mm Length: 1800mm Surface roughness: 30-50μm Support roll: Material: Ni-Cr alloy (Ni: 50%, Cr: 35%, w:
15%) Outer diameter: 176 to 195 mm Body length: 2500 mm (distance between bearings) Surface roughness: 15 to 25 μm From the shown results, the bending stress δ (Kgf/mm ² ) applied to the support roll and the average clearance α
Sleeve cracking can be prevented by selecting the average clearance in the radial direction (mm) to satisfy α≧1 and δ≦4.0. Preferably, more satisfactory results can be obtained by setting the above clearance according to the following formula.

Formula: α≧0.2δ ² +1 A series of experiments conducted by the inventors has shown that the above relationship between bending stress (δ) and average clearance (α) holds true for heat-resistant sleeves with commonly used shapes and dimensions. It was confirmed that In addition, from the viewpoint of the material of the support roll, it was confirmed that the above-mentioned condition of δ≦4Kgf/mm ² can be sufficiently satisfied by using conventional Ni-Cr heat-resistant alloys, stainless steel, etc.

As already mentioned, the stopper 9 may be a crown-shaped one that is easy to remove, or a fixed flat one that can be positioned, and its use is arbitrary. The range of movement of the ceramic sleeve 6 in the axial direction is determined by the distance between the crown stopper 9 and the body 5 of the support roll 4, as shown in FIG. By interposing an annular spacer 10 of an appropriate thickness between the clasps 11, the thickness can be set to any desired range.

Further, the support roll 4 may be provided with a fluid passage for cooling the support roll so as to extend over the entire longitudinal direction of the central part of the support roll, and a cooling fluid such as water, etc. may be supplied from the outside into this fluid passage. By supplying the support roll, the axial deflection of the support roll may be reduced as much as possible.

Furthermore, the ceramic sleeve 6 may be divided into appropriate sizes and arranged along the axial direction in order to prevent damage due to bending due to thermal expansion. The short and small cylindrical divided sleeves are each chamfered on both end faces so that they can be divided into required lengths, and these are continuously attached to the outer circumferential surface of the body 5 of the support roll 4 in a loose fit manner. You can do it like this.

Thus, unlike conventional heat-resistant rolls, the heat-resistant roll according to the present invention can substantially safely prevent damage to the sleeve due to roll deflection or impact, thereby making it possible to use the sleeve for a long period of time. It is a highly valuable product that is technically and economically excellent, making it possible to put it into practical use.

[Brief explanation of drawings]

Fig. 1 is a schematic sectional view showing a heat-resistant roll according to the present invention applied to a hearth roller heating furnace; Fig. 2 is a partially enlarged view thereof; Fig. 3 is a -
and FIG. 4 are graphs showing the relationship between the bending stress of the support roll and the average clearance. 1: Hearth roller heating furnace, 3: Heat resistant roll,
4: Support roll, 5: Body, 6: Ceramic sleeve, 7: Peripheral clearance, 8: Annular clearance, 9: Stopper.

Claims (1)

[Scope of Claims] 1. A heat-resistant roll comprising a support roll and a ceramic sleeve externally fitted onto the support roll, wherein the support roll exhibits maximum thermal expansion in the axial and radial directions. The ceramic sleeve is configured to be loosely fitted to the support roll, and at least one of the contact surfaces between the outer peripheral surface of the support roll and the inner peripheral surface of the ceramic sleeve is roughened.
Rmax≧25 μm, the bending stress applied to the support roll during use is δ (Kgf/mm ² ), and the average radial clearance between the support roll and the ceramic sleeve is α (mm), then α≧1 and A heat-resistant roll that satisfies δ≦4.0. 2. The heat-resistant roll according to claim 1, wherein the ceramic sleeve is made of fused silica. 3. The heat-resistant roll according to claim 1 or 2, wherein the bending stress (δ) and the average clearance (α) satisfy the formula: α≧0.2δ ² +1.