JP5794614B2 - Furnace roller - Google Patents

Description

  The present invention relates to a heating furnace roller that is disposed in a furnace body that is a core of equipment for continuously or intermittently heating and heat-treating strip-like or lump-like materials such as steel plates and conveys materials. Furthermore, there are also rollers that come into contact with high-temperature products such as heated materials and rollers that operate in a heated atmosphere, such as transport rollers for glass production, pinch rolls used to form heated steel sheets, and support rolls. included.

  In a furnace for heating and heat-treating the metal strip, a roller for transporting the strip is provided. Frequently, the surface of the strip is damaged due to wear of the roller surface due to oxide scale on the surface of the strip heated in a high-temperature furnace, rough skin, and the transfer of the scale to the rough skin (build-up). Roller replacement is required. For this reason, a roller formed with a ceramic sprayed coating layer that is excellent against wear and seizure, and a ceramic roller have been used for some of the rollers.

  FIG. 10 is a conceptual diagram of an in-furnace transport roller (also referred to as a hearth roller) installed in a heating furnace according to the prior art. In the figure, a roller for conveying a material to be heat-treated includes a body sleeve, a shaft made of heat-resistant steel concentrically fitted on the inner peripheral surface thereof, and a bearing made of heat-resistant steel provided at both ends of the shaft. It consists of a part. This in-furnace transport roller is disposed so as to penetrate a heating furnace wall made of a refractory, and is configured to be rotationally driven through a bearing provided outside the furnace wall. The atmosphere in the furnace is usually air or an inert gas at a temperature of 800 to 1250 ° C. A shaft center hole penetrating the shaft member and the bearing portion is provided, and the water is cooled through the shaft center hole. The ceramic roller shown in the figure is overwhelmingly superior in terms of roll durability than the ceramic spray roller, but in the method of joining the body sleeve and shaft (or synchronizing the rotation) There is a big problem, and ceramicization is not progressing.

  In the case of the most durable roller made of ceramic, in order to synchronize the rotation of the body sleeve and the shaft material, the body sleeve is fixed to the shaft material by pressing the flange sleeve on both sides of the body sleeve via a spring. (Patent Document 1, Patent Document 2) Method of providing a groove on the end of the body sleeve and transmitting the rotation from the shaft material to the body sleeve by a protrusion (key, cotter, etc.) fixed to the shaft material (Patent Documents 3 and 4) are common. This kind of rotation synchronization method has been adopted because of the general interference fit (typically represented by shrinkage fit) as a body sleeve fitting technique, due to the difference in thermal expansion between ceramics and metal. This is because the derived problem could not be solved. The problems in each of the above joining techniques will be described below.

  In the method of synchronizing the rotation of the body sleeve with the shaft member via the spring by the flange (Patent Documents 1 and 2), the temperature difference between the body sleeve and the shaft member is changed, and the spring exposed to a high temperature is used. There is a problem that the body sleeve is slippery due to deterioration with time. If the spring force is increased to prevent slipping, a large pressing force acts on the end face of the body sleeve, and the risk of destruction at the end of the body sleeve sleeve made of ceramic increases.

  In the method of fixing to a shaft member with a key, a cotter pin, or a bolt (Patent Documents 3 and 4), stress concentration occurs in the key groove or hole peripheral portion formed in the end portion of the brittle ceramic body sleeve. In addition, when considering the case of the key, due to the large gap provided in the fitting part between the key and the key groove (the allowance set based on the difference in thermal expansion coefficient several times between ceramics and metal), Impact force is generated when starting and stopping. Due to this impact force, there is a weak point in which the key or hole of the trunk sleeve is liable to crack or break.

  When such a fixing method is adopted, a structure in which a solid shaft penetrates the inside of the trunk sleeve in the axial direction or a hollow shaft (shaft sleeve) is arranged inside the trunk sleeve is generally used. Is. As described above, in the structure in which a hollow or solid metal or nonmetallic shaft material (Patent Document 4) is arranged in a heating furnace and heated, problems caused by the shaft material are inevitable. One is that the hollow inner surface is cooled with water in order to cool the hollow metal shaft. For this reason, the body sleeve is also cooled through the metal shaft, and the plate surface temperature on the roller side in contact with the product is lowered. Furthermore, the loss of heat energy due to water cooling is not small. The other is that solid shafts made of metal or carbon-based materials suffer from reduced strength due to high-temperature heating and inherently fragile materials, so there is a risk of shaft eccentricity / deformation and even destruction.

  In order to avoid a structure in which the shaft material penetrates through the furnace, Patent Document 5 is a structure in which the inside of the shaft is hollow, and the steel hollow shaft is fixed by a heat-resistant adhesive at the end portion of the body sleeve. Yes. This adhesive layer is also expected as a buffer layer against cracking stress caused by the difference in thermal expansion between the shaft member and the body sleeve. However, there is a limit to the strength of the adhesive against the limit of the heat-resistant temperature of the adhesive, the shearing force acting on the adhesive layer due to the difference in thermal expansion between the shaft member and the body sleeve, and further to the compression force. The problem of looseness from the adhesive layer is inevitable for use in a high temperature exceeding ℃ or in a heating furnace where a large bending load is applied to the roller. For this reason, when using at high temperature and high load, constant cooling inside the shaft is necessary. In the case of water cooling, in addition to the loss of heat energy, the problem of water leakage from the adhesive layer Occurs.

  To solve the problem of differential thermal expansion, a method has been devised in which a low thermal expansion metal that has a thermal expansion close to that of ceramics is used for the shaft material. However, even in that case, the thermal expansion coefficient is about twice that of ceramics. Since metal is extremely expensive, it has not been put into practical use.

JP-A-62-280324 JP-A-8-295948 JP-A-3-249122 JP-A-10-183260 JP 2000-249472 A

Elastic mechanics, Kei Murakami, Yokendo, 2008, p.48-50 Casting Engineering Data Book II, High Temperature Properties of Cast Steel, Composite Casting Center, 1981, p87

  An interference fit can be considered as a method of firmly joining the ceramic body sleeve and the metal shaft, but a metal shaft having a large thermal expansion is disposed inside the ceramic sleeve having a small thermal expansion. Especially the source of the problem. Although it is generally well known that a reliable technology that can solve the problem caused by the difference in thermal expansion has not been devised, this shrink fitting method has not been adopted for high-temperature rollers. It can be said that it is a big reason.

Specifically, the problem of the difference in thermal expansion is that the thermal expansion coefficient of the brittle ceramic is 3 × 10 ⁻⁶ 1 / ° C. (Si ₃ N ₄ ceramics), and the thermal expansion of the metal shaft disposed inside the ceramic shaft. The coefficient is 12 × 10 ⁻⁶ 1 / ° C. (Cr, Mo alloy carbon steel) or 17 × 10 ⁻⁶ 1 / ° C. (austenitic stainless steel), which is 4 times or more different. For example, consider a case where a metal shaft sleeve is fitted to the end of a ceramic sleeve at room temperature. When both sleeves are heated to the same temperature in a heating furnace, the ceramic sleeve is pushed out from the shaft sleeve by a large expansion more than four times that of the body sleeve, and a large cracking stress (circumferential stress) is generated. Arise. If this cracking stress exceeds the fracture strength of ceramics, the ceramic sleeve will break, and if it occurs in the furnace during operation, the operation of the heating and heat treatment furnace and all its front and rear equipment will be forced to be interrupted, It will cause a lot of product defects and a large loss of operation.

  In order to alleviate the difference in thermal expansion, a buffer layer has been introduced into the fitting part or a method of fitting via an adhesive has been implemented. No technology has been established as a technique that can reliably transmit to the body sleeve while maintaining a constant bending rigidity.

  As another measure for avoiding the difference in thermal expansion, a method of transmitting rotation by a key has been devised, but in this method, the key groove processed at the end of the ceramic sleeve becomes a source of stress concentration, which causes the destruction of the fragile ceramic sleeve It becomes. What can be a stress concentration source includes not only key grooves but also all shapes that are not smooth and have some irregularities such as tapped holes and stepped processing. In addition, since there is a gap for allowing a difference in thermal expansion at the site of these stress concentration sources, the structure is often applied with a force that causes an impact, and the ceramic sleeve is destroyed. It will be accelerated.

  Since the shaft member of the ceramic sleeve having such a structure is disposed on the inner surface side of the ceramic sleeve over the entire length of the sleeve, it is heated by radiant heat and heat transfer from the ceramic sleeve heated in a high temperature furnace. For this reason, eccentricity and deformation such as bending of the shaft material are likely to occur, and stable operation may not be possible. In order to prevent the temperature of the shaft material from increasing, it is common to provide an inner hole in the shaft center or to form a hollow sleeve so that the water inside the shaft is cooled. Shaft material deformation / eccentricity is improved by water cooling, but as a result of cooling the ceramic sleeve and cooling the transported strip, etc., the plate shape becomes unstable, and the heat in the furnace together with water Since it is discharged, it has become an obstacle to thermal efficiency.

  Therefore, the present invention makes use of the advantages of ceramics in heating furnace rollers, and the joining of the ceramic body sleeve and the shaft sleeve is stable and reliable without being affected by the difference in thermal expansion even in a high temperature atmosphere. It aims at providing the roller for heating furnaces with high property.

Furnace rollers of the present invention includes a furnace wall, so as to penetrate the furnace wall, comprising a ceramic body part sleeve, from each end portion inner periphery fitting the joined metal shaft sleeve of that A rotatable structure is provided, a bearing for the rotatable structure is provided outside the furnace wall, and an internal anhydrous cooling structure is provided. The shaft sleeve is fitted and joined to the inner peripheral side of the end portion of the body sleeve by an interference fit. The shaft sleeve is configured by using the same metal and connecting a hollow sleeve portion to be fitted to the body sleeve and a hollow sleeve-shaped bearing portion. The end portion of the sleeve portion extends outward from the end portion of the trunk sleeve. A bearing that rotatably supports the bearing portion of the shaft sleeve is provided.

The bearing portion than the sleeve portion and the small diameter, you connected integrally to the flange portion is interposed therebetween.

  The length N of the end portion of the sleeve portion extending outward from the end portion of the body sleeve is set to be twice or more longer than the thickness H of the shaft sleeve portion. You may comprise the air cooling means for sending cooling air with the air cooling pipe provided in the center of a flange part and a bearing part, and the hole provided in multiple numbers in the flange part. Further, a partition wall that receives cooling air and appropriately shields internal air that has become hot at the body sleeve portion may be provided inside the sleeve portion.

The body sleeve is selected from the group consisting of Al ₂ O ₃ , ZrO ₂ , SiO ₂ , SiC, Si ₃ N ₄ , Y ₂ O ₃ , TiO ₂ , Cr ₂ O ₃ , MgO, and CeO _2. A ceramic sintered body composed of the above components. The metal shaft sleeve is selected from carbon steel, alloy steel, or heat resistant steel.

  The wall thickness of the sleeve portion is designed so as not to exceed the breaking strength of the body sleeve in a high temperature operating state. In the fitting portion between the trunk sleeve and the shaft sleeve, a heat insulating layer may be interposed between them. In the fitting portion between the body sleeve and the shaft sleeve, thread groove processing may be performed on the outer diameter of the shaft sleeve so that the thread portion has a ratio of 0.5 or less of the non-thread portion. In order to relieve local strong pressure generated at the inner end of the trunk sleeve, the inner end of the trunk sleeve may be chamfered with a large curvature.

  In the fitting portion between the body sleeve and the shaft sleeve, a taper that increases the wall thickness at the end side on the outer diameter side of the shaft sleeve, or a wall thickness at the end side on the inner surface of the body sleeve end is thin. Such a taper may be formed.

  The roller for the heating furnace of the present invention uses a ceramic body sleeve having heat resistance and rough skin resistance (build-up resistance) on the outermost surface where the furnace atmosphere and the steel sheet to be heated are in contact, so the surface quality of the steel sheet The stable operation period until the surface quality begins to deteriorate can be extended several times or more as compared with a roller with a conventional ceramic coating. Therefore, it is possible to produce a steel sheet with excellent surface quality while maintaining high operation efficiency of heating and heat treatment.

  In addition, by adopting the heating furnace roller of the present invention, stable operation is maintained and maintained without any problems such as cracks during operation of the ceramic body sleeve and eccentricity or deformation of the roller. it can. Moreover, in the heating furnace roller of the present invention, since it is not necessary to perform water cooling inside the roller, the thermal energy efficiency of the heating / heat treatment furnace can be improved as compared with the conventional internal water cooling system. Thus, it can be said that the heating furnace roller of the present invention is friendly to the global environment in addition to stabilization of product quality and improvement of operation efficiency.

  Further, according to the present invention, since the sleeve portion of the shaft sleeve and the bearing portion are connected, there is a risk of cracking of the body sleeve due to the difference in thermal expansion between the ceramic body sleeve and the metal shaft sleeve. It becomes possible to carry out shrink fitting without using. Therefore, in order to synchronize the rotation of the body sleeve with the shaft material, a method using a heat-resistant adhesive, a method using a spring, a method of fixing to the shaft material with a key, a cotter pin or a bolt, etc. The effect that the roller for a heating furnace which does not produce the various problems which arise by a law can be provided arises.

(A) is a general view of the roller for carrying a strip according to the present invention installed in a heating furnace, and (B) is a detailed view showing an end thereof. (A) is a figure which illustrates the shaft sleeve of another example different from FIG. (B) is a figure which shows the reference example which can be used when the diameter of a sleeve part is comparatively small. It is a figure explaining the chamfering given to the inner surface edge part of the trunk | drum sleeve. It is a figure explaining the taper given to the shaft sleeve fitting part outer diameter. 6 is a graph (simple calculation) showing the relationship of the maximum stress on the inner surface of the body sleeve with respect to the change in the temperature of the shaft sleeve when the temperature of the body sleeve is 800 ° C. (A) is a longitudinal sectional view of a shaft sleeve provided with air cooling means, (B) is a side view seen in the direction of arrow XX shown in (A), and (C) is an arrow Y shown in (A). It is the side view seen in -Y direction. 6 is a graph showing the examination results of the thickness of a shaft sleeve that is safe against cracking at a trunk sleeve temperature of 800 ° C. and a shaft sleeve temperature of 500 ° C. FIG. This graph shows the circumferential compressive stress generated in the shaft sleeve when the shaft sleeve is heated to 600 ° C with respect to the body sleeve temperature of 800 ° C, and the shaft sleeve thickness is changed from solid to 5 mm. is there. It is a graph which shows the examination result of the shaft sleeve thickness safe with respect to a crack at the time of a trunk | drum sleeve temperature of 1000 degreeC and a shaft sleeve temperature of 500 degreeC, when a shaft material is changed into austenitic stainless steel. It is a conceptual diagram of the in-furnace conveyance roller equipped in the heating furnace of a prior art.

  Hereinafter, the present invention will be described based on examples. FIG. 1 (A) is an overall view of a belt conveying roller of the present invention installed in a heating furnace, and FIG. 1 (B) is a detailed view showing an end portion thereof. As shown in the drawing, a metal shaft sleeve (metal hollow shaft) is fitted and joined to both ends of a ceramic body sleeve to form an internal anhydrous cooling structure. The shaft sleeve is fitted and joined to the end of the body sleeve by an interference fit (shrink fit or cold fit). However, in this fitting part, you may interpose a heat insulation layer among them. The fitting between the body sleeve and the shaft sleeve is based on the direct contact between them and the smooth rotation is synchronized and the shaft center is kept straight. However, it is necessary to have a heat insulation effect from the body sleeve to the shaft sleeve. If present, a thin and strong heat insulating layer may be interposed in the fitting portion. Further, in the fitting portion between the body sleeve and the shaft sleeve, it is also possible to perform thread groove processing on the outer diameter of the shaft sleeve so that the thread portion has a ratio of 0.5 or less of the non-thread portion. .

  Further, as shown in FIG. 3, in order to relieve local strong pressure generated at the inner end portion of the trunk sleeve, it is possible to chamfer the inner end portion of the trunk sleeve with a large curvature. Further, as shown in FIG. 4, in order to uniformize the axial distribution of the contact pressure generated between the body sleeve and the shaft sleeve, the wall thickness on the end side is increased at the outer diameter of the shaft sleeve fitting portion. It is also possible to apply such a taper. Alternatively, the taper (not shown) can be formed on the inner surface side of the end portion of the body sleeve so that the thickness of the end portion is reduced.

The shaft sleeve illustrated in FIGS. 1A and 1B shows an example in which the bearing portion is smaller in diameter than the sleeve portion and the two are integrally connected by a flange portion. The thickness M of the flange portion is not necessarily the same as the thickness H of the sleeve portion, and the illustrated example shows a case where M> H. A body sleeve fitted with a metal shaft sleeve is rotatably supported by bearings located on both sides. A rotatable gap is formed between the trunk sleeve and the furnace wall. The body sleeve is one or more selected from Al ₂ O ₃ , ZrO ₂ , SiO ₂ , SiC, Si ₃ N ₄ , Y ₂ O ₃ , TiO ₂ , Cr ₂ O ₃ , MgO, CeO ₂ It consists of a ceramic sintered body composed of The shaft sleeve is made of carbon steel unless the heating temperature is high, and is made of Cr, Mo alloy steel, and heat resistant steel such as stainless steel and SCH in the region where the heating temperature is high and permanent deformation of the shaft sleeve occurs.

Shaft sleeve, using the same metal, a hollow sleeve portion a thin fitted into the barrel sleeve, you to the structure connecting the bearing portion of the thin-walled hollow sleeve shape. If the diameter of the sleeves portion is larger shape relatively, the bearing portion than the sleeve portion and the small diameter, you connected integrally to the flange portion is interposed therebetween. If the diameter of the sleeves portion is relatively small, as shown in FIG. 2 (B), the sleeve portion and the bearing portion may be a straight sleeve shape having the same diameter.

FIG. 2 (A) illustrates the shaft sleeve of different Another example that of FIG. 2 (A) is, Ru der that linearly changed in a tapered shape the diameter of the flange portion connecting sleeve portion and the bearing portion. FIG. 2B is a diagram illustrating a reference example in which a sleeve portion and a bearing portion are directly connected without providing a flange portion.

  In any of the shaft sleeve configurations shown in FIGS. 1 and 2, not only the flange portion but also the bearing portion is provided with a shaft center hole penetrating the center thereof, so that the air inside the roller can be ventilated. . A part of the sleeve portion extends to the outside of the furnace wall. A bearing part and a flange part will be located in the furnace wall exterior side. Furthermore, as will be described later with reference to FIG. 6, an air cooling tube (air cooling means) for sending a cooling gas may be provided. This bearing part is a part of the shaft sleeve, which is a cylindrical part provided on the outer periphery of the shaft sleeve and used for rotation of the roller. What is a hollow and thin sleeve part to be fitted to the body sleeve? Different functions.

  In FIG. 1B, the length of the sleeve portion is indicated by L, the thickness of the sleeve portion is indicated by H, and the distance between the end portion of the trunk sleeve and the flange portion at the back of the shaft sleeve is indicated by N. The distance N between the end of the body sleeve and the flange portion is longer than the thickness H of the shaft sleeve portion, and preferably twice or more. The temperature of the sleeve portion is several hundred degrees lower than the temperature in the furnace because heat transfer is blocked by the furnace wall.

  In the fitting part where the shaft sleeve is fitted inside both ends of the body sleeve, the body sleeve and the shaft sleeve are coupled, and the integral rotation of the shaft sleeve and the body sleeve and the bending rigidity in the axial direction can be maintained. The tightening allowance is set as follows. This fitting part has a structure in which a cracking stress (circumferential stress) acts from a shaft sleeve having a large thermal expansion coefficient against a ceramic body sleeve that is more fragile than metal. Therefore, there is a demand for a design that does not damage the ceramic body sleeve and does not destroy the ceramic body sleeve. Tensile cracking stress is determined by thermal expansion corresponding to the body sleeve temperature and thermal expansion coefficient of the fitting part and the shaft sleeve temperature and thermal expansion coefficient of the fitting part under operating conditions from room temperature to high temperature. Therefore, it is obtained as a circumferential stress generated in the body sleeve according to each thickness and elastic modulus. By determining the wall thickness of the shaft sleeve so that this stress does not exceed the breaking stress of the trunk sleeve, the trunk sleeve can be used in a high temperature range without being broken. In a simple manner, the thickness of the shaft sleeve suitable for the conditions can be obtained by taking an example of a roller specification as shown in FIG.

  With such an internal anhydrous cooling structure, it is possible to provide a ceramic roller having excellent durability and reliability that is excellent in rough skin resistance and contributes to the thermal energy efficiency of the heating furnace. When synchronizing the rotation of the body sleeve and the shaft sleeve, if the two are directly firmly joined and the bending rigidity is maintained, a notch is formed at the end of the body sleeve, or a metal is formed inside the body sleeve. There is no need to penetrate the shaft. In strong fitting and joining, the biggest problem is a technique for avoiding the risk of destruction of the body sleeve due to the difference in thermal expansion between ceramics and metal. Since the thermal expansion of the shaft sleeve fitted to the inside of the body sleeve is large, the shaft sleeve swells larger, and a cracking stress is generated in order to push the ceramic body sleeve from the inside. In this case, if the shaft to be expanded is easily deformed, the force to be expanded becomes smaller.

  FIG. 5 shows the relationship of the maximum stress on the inner surface of the body sleeve with respect to the change in the shaft sleeve temperature at a temperature of 800 ° C. of the body sleeve at the joint (set higher than the actual value from the viewpoint of safety design). (Simple calculation) graph. In order to see the effect of the thickness of the shaft sleeve on the cracking stress of the trunk sleeve, when the trunk sleeve temperature is 800 ° C., the circumferential stress on the inner surface of the trunk sleeve against the shaft sleeve temperature (cracking crack) Stress). Assuming that the cylinder was infinitely long and each sleeve was heated to a uniform temperature, the thickness of the shaft sleeve was calculated for each of 5 mm, 10 mm, 20 mm, 30 mm, and solid shaft. From this figure, as the temperature of the shaft sleeve increases, the circumferential stress increases linearly. The stress is maximum for the solid shaft (the ratio is 1.0), and decreases as the thickness of the hollow shaft decreases. When the thickness is 10 mm or less, the stress is 1/4 (ratio 0.25). It is shown that it decreases below.

  As shown in FIGS. 1 (B), 2 (A), and 2 (B), the tip of the metal sleeve is P, the terminal end of the body sleeve is Q, and the inner diameter at the back of the shaft sleeve starts to decrease. Is R. When the thickness of the shaft sleeve is 15 mm, the inner surface stress of the trunk sleeve is on the safe side even at 500 ° C. as can be seen from FIG. When the end portion Q of the body sleeve is set to 30 mm, the temperature is considerably lowered. However, when viewed in FIG. 5, the internal stress of the body sleeve is on the sufficient safety side even at 350 ° C. or higher. In the vicinity of the wall R at the back of the shaft sleeve, the temperature of the portion corresponding to the real shaft is further lowered, but even at 300 ° C., it is on the safe side as the real shaft.

  Although the temperature of the trunk sleeve rises first, such as at the start of operation of the high-temperature furnace, there is a possibility that the problem of adhesion between the trunk sleeve and the shaft sleeve (cannot transmit rotational force) may occur. In the present invention, when the temperature of the trunk sleeve first rises at the start of operation and the inner diameter becomes larger, the expansion of the inner diameter of the trunk sleeve precedes the tip portion P of the shaft sleeve. Even if loose fitting occurs, the end portion Q of the body sleeve is still not sufficiently thermally conductive, and the expansion of the inner diameter of the body sleeve is delayed, so that they are in close contact. When the vicinity of the end portion Q of the body sleeve expands, the temperature rise also follows the temperature of the P portion of the shaft sleeve to achieve sufficient fitting. When the operation is stopped, the rate of temperature decrease is slow, and the temperature difference is small and there is no concern about cracking. In short, it can be seen that when the vicinity R (end portion of the sleeve portion) of the shaft sleeve is further extended outward from the terminal portion Q of the body sleeve, the portion that inhibits the deformation of the shaft sleeve becomes far and good results are obtained. .

  6A is a longitudinal sectional view of a shaft sleeve provided with air cooling means, FIG. 6B is a side view seen in the direction of arrow XX shown in FIG. 6A, and FIG. 6C is shown in FIG. It is the side view seen in the arrow YY direction. The flange portion and the bearing portion can be provided with an air cooling pipe (air cooling means) for sending cooling air. Cooling air can be sent from an air cooling tube provided at the center of the flange portion and the bearing portion and can be discharged to the outside through a plurality of holes provided in the flange portion of the shaft sleeve. At this time, the partition provided inside the sleeve portion receives the cooling air, and appropriately shields the internal air that has become hot at the trunk sleeve portion. Several such partitions are fixed inside the shaft sleeve. In the example shown in FIG. 6, four locations are fixed to the sleeve portion of the shaft sleeve by welding. As the partition wall, a steel plate having a thickness of 1 to 2 mm formed by pressing or the like is sufficient. The left and right positions of the partition wall shown in FIG. 6A may be closer to the bearing portion than shown. Even if cooling air is not sent, by providing a partition wall to properly shield the internal air, it is further passed through this hole by rotating the roller outside the several holes provided in the flange part of the shaft sleeve. By attaching a plate that allows air to enter, the internal air of the roller can be ventilated. As an effect, the air inside the shaft sleeve is cooled. This is sufficient for a relatively low temperature blast furnace.

FIG. 7 is a graph showing the examination results of the thickness of the shaft sleeve that is safe against cracking at a trunk sleeve temperature of 800 ° C. and a shaft sleeve temperature of 500 ° C. As an example of severe thermal conditions among in-furnace transport rollers (hearth rollers), numerical analysis is performed for slab soaking furnaces, assuming that the heating temperatures of the body sleeve and shaft sleeve are more severe than the actual conditions. Perform strength evaluation. Since the assumption conditions are strictly estimated in this way, the evaluation based on the analysis result can be judged as an evaluation on the safety side of the actual equipment.

In this analysis, the temperature of both the body sleeve and the shaft sleeve is given and the stress under each temperature is obtained. As in the actual case, from the heating and heat conduction from the ambient temperature. Not what you want. It must be refused that it is an approximate analysis for relatively comparing the influence of the thickness of the shaft sleeve on the cracking stress caused by thermal expansion.

Furnace temperature: 1200 ° C (not used directly in the calculation here, but shown for reference), roller end, that is, the temperature of the body sleeve (silicon nitride) fitted with the shaft sleeve: 800 ° C ( Actually, this part is covered with the furnace wall insulation of the heating furnace, so there is an example of measurement that is significantly lower than the furnace temperature and below 400 ° C, but here it was set quite high)) Shaft sleeve (heat-resistant steel) temperature: RT (room temperature) to 600 ° C, body sleeve outer diameter, length, wall thickness: 300, 2600, 30 mm, shaft sleeve outer diameter: 240 mm, elastic modulus: (ceramics) 300 MPa, (the shaft sleeve heat-resistant steel) 210 MPa, the thermal expansion coefficient :( ceramics) 3 × 10 ^-6 (a shaft sleeve heat resistant ^{steel) 11 × 10 -6 1 / ℃} , shrink fitting ratio δ / 2b: 2 × 10 ^{- It was 6} . Here, δ is a shrinkage allowance, and 2b is a cylinder sleeve inner diameter or a shaft sleeve outer diameter.

  Under the above conditions, change the thickness of the shaft sleeve to 120 (solid), 30, 20, 10, 5 mm, and analyze the circumferential stress (cracking stress) generated on the inner surface of the body sleeve did. The formula used for the analysis is shown below (see Non-Patent Document 1).

The maximum value of the circumferential stress of the body sleeve is generated on the inner surface,
σ _1θb = (d ² + b ² ) p / (d ² −b ² ) (1)
The maximum circumferential stress of the shaft sleeve occurs at the outer diameter,
σ _2θb = (b ² + a ² ) p / (b ² −a ² ) (2)
Is required. Here, the pressure p of the contact portion is
p = E ₁ E ₂ (d ² −b ² ) (b ² −a ² ) {δ / 2b + (α ₂ ΔT ₂ −α ₁ ΔT ₁ )} / [E ₂ (b ² −a ² ) {(d ² + b ² ) + ν ₁ (d ² −b ² )} − E ₁ (d ² −b ² ) {(a ² + b ² ) + ν ₂ (b ² −a ² )}]
Is required. 2d: outer diameter of the body sleeve, 2b: same inner diameter or outer diameter of the shaft sleeve (δ is negligible), 2a: inner diameter of the shaft sleeve, E ₁ , E ₂ : longitudinal length of the body sleeve and the shaft sleeve Elastic modulus, ν ₁ , ν ₂ : Poisson's ratio of each of the body sleeve and the shaft sleeve, ΔT ₁ , ΔT ₂ : Temperature increase from room temperature of each of the body sleeve and the shaft sleeve, α ₁ , α ₂ : Body sleeve The linear expansion coefficient of each shaft sleeve.

  FIG. 7 shows the stress on the inner surface of the trunk sleeve obtained using the equation (1). This stress is related to the cracking of the ceramic and is always generated during the steady operation of the roller. In actuality, in addition to this stress, a stress on the body sleeve due to the weight of the transported material also acts, but it is negligibly small and is not considered.

  In FIG. 7, 300 MPa was used as the design strength for the tensile strength of 400 MPa of silicon nitride ceramics. In consideration of the high temperature strength characteristics of the shaft sleeve, 500 ° C. was made the service life limit. Since there are many shaft materials that can withstand temperatures higher than this, there is still room for judgment from the viewpoint of cost and effectiveness. From FIG. 7, when the shaft temperature reaches 500 ° C., the ceramic strength exceeds the thickness of 30 mm (same thickness as that of the body sleeve), but the shaft sleeve can be used with a thickness of 20 mm or less.

  On the other hand, there is a concern that the strength of the shaft sleeve itself may decrease due to the thinning of the shaft sleeve. The strength analysis of the shaft sleeve itself can be evaluated by equation (2). When the temperature of the shaft sleeve is raised to 600 ° C. with respect to the body sleeve temperature of 800 ° C., the thickness of the shaft sleeve is changed from solid to 5 mm, and the circumferential compressive stress generated in the shaft sleeve is obtained. Shown in In the figure, the design strength (yield point) of the shaft material is quoted from (Non-Patent Document 2), and it was considered that it can be used below this limit line. In FIG. 8, as in the case of the body sleeve, it can be said that the shaft sleeve can be used with a shaft sleeve thickness of 5 mm at a service life limit temperature of 500 ° C. or less. Furthermore, it is a matter of course that the reliability can be further improved by using a material having a high temperature strength.

  Regarding the strength of the shaft sleeve, in addition to this, it is necessary to consider the influence of the stress applied each time the roller rotates due to the gravity of the conveying material. The maximum stress in this case is an axial stress σzb generated by bending the shaft sleeve, and is generated at the shaft outer diameter at the end of the body sleeve. This bending stress is obtained by the following equation (3).

σzb = 32bPl / π (b ⁴ −a ⁴ ) (3)
However, P: gravity of the conveying material applied to the roller × 4 (impact coefficient) 5760 kg, l: distance from the end of the trunk sleeve to the center of the bearing, 525 mm. The axial stress is calculated to be 69.5 MPa from Equation (3), which is about 10% of the axial circumferential compressive stress at the same position at 500 ° C obtained from Equation (2), and the effect is ignored. it can.

  As described above, it has been found that by reducing the thickness of the shaft sleeve, specifically, by reducing the thickness to 5 mm from the solid, the cracking stress of the ceramic can be reduced to about 1/5.

FIG. 9 is a graph showing the examination results of the shaft sleeve thickness that is safe against cracking when the shaft material is changed to austenitic stainless steel at a trunk sleeve temperature of 1000 ° C. and a shaft sleeve temperature of 500 ° C. Since this embodiment 2 uses an austenitic heat-resistant material that is higher in temperature and superior in heat resistance to the shaft material as compared with the first embodiment, the thermal expansion coefficient of the shaft sleeve becomes larger, and cracking tends to occur. It is a condition. Only changes from Example 1 are shown.

Roller end, that is, the temperature of the body sleeve (silicon nitride) at the fitting portion with the shaft sleeve: 1000 ° C (set to be considerably higher than the actual condition), thermal expansion coefficient: (ceramics) 3 × 10 ^-6 (heat-resistant steel of the shaft sleeve) ) 17 × 10 ⁻⁶ 1 / ° C.

  As shown in FIG. 9, the thickness of the shaft sleeve that satisfies the heat resistance limit of 500 ° C. of the shaft sleeve and the ceramic design strength of 300 MPa is 10 mm or less (the thickness of the body sleeve is 30 mm). It can be seen that if a thin shaft material is used, it can be used even in this case. However, even in that case, in order to keep the shaft sleeve at a low temperature of 500 ° C. or less with respect to the temperature of the body sleeve 1000 ° C., it is desirable to introduce an appropriate heat insulating material on the fitting surface.

Claims (11)

Comprising a furnace wall, so as to penetrate the furnace wall, with comprises a ceramic barrel sleeve, a rotatable structure comprising at both ends in the peripheral-side fitting joined to a metallic shaft sleeve of that, the furnace In the heating furnace roller provided with a bearing for the rotatable configuration on the outside of the wall and having an internal anhydrous cooling structure,
The fitting joining of the shaft sleeve is joined by an interference fit to the inner peripheral side of the end of the trunk sleeve,
The shaft sleeve has a structure in which a hollow sleeve portion that is fitted to the body sleeve and a hollow sleeve-shaped bearing portion that is rotatably supported by the bearing are connected using the same metal, and the sleeve The bearing part is made smaller in diameter than the part, and a flange part is interposed between the two, and they are integrally connected,
Furnace rollers consisting in extended outward from an end portion of said barrel sleeve an end of the sleeve portion. 2. The heating furnace roller according to claim 1, wherein a length N of an end portion of the sleeve portion extending outwardly from an end portion of the body sleeve is at least twice a thickness H of the sleeve portion . The heating furnace roller according to claim 1, wherein an air cooling means for sending cooling air is constituted by an air cooling pipe provided in the center of the flange part and the bearing part and a plurality of holes provided in the flange part. The roller for a heating furnace according to claim 3, wherein a partition wall that receives cooling air and appropriately shields internal air that has become hot at the body sleeve is fixed to the sleeve portion. The body sleeve is selected from the group consisting of Al ₂ O ₃ , ZrO ₂ , SiO ₂ , SiC, Si ₃ N ₄ , Y ₂ O ₃ , TiO ₂ , Cr ₂ O ₃ , MgO, CeO ₂ , one or two. The roller for a heating furnace according to claim 1, wherein the roller is a sintered body of ceramics composed of more than one component. The roller for a heating furnace according to claim 1, wherein the metal shaft sleeve is selected from carbon steel, alloy steel, or heat resistant steel. 2. The heating furnace roller according to claim 1, wherein the thickness of the sleeve portion is designed not to exceed the breaking strength of the body sleeve in a high temperature operation state. The heating furnace roller according to claim 1, wherein a heat insulating layer is interposed between the body sleeve and the shaft sleeve in a fitting portion. The thread groove processing is performed in the fitting portion between the body sleeve and the shaft sleeve so that the threaded portion has a ratio of 0.5 or less of the non-threaded portion to the outer diameter of the shaft sleeve. 2. A heating furnace roller according to 1. Wherein in order to mitigate the local strong pressure generated in the barrel inner surface of the sleeve end, furnace rollers according to claim 1 which has been subjected to surface up to the barrel inner surface of the sleeve end. In the fitting portion between the trunk sleeve and the shaft sleeve, the outer diameter side of the sleeve portion constituting the shaft sleeve is tapered such that the thickness of the end portion side of the sleeve portion is increased, or The roller for a heating furnace according to claim 1, wherein a taper is formed on the inner surface of the end portion of the body sleeve so that the thickness of the end portion side of the body sleeve is reduced.

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