JP2018062700A - Hearth roll for continuous annealing furnace and manufacturing method of hearth roll for continuous annealing furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hearth roll for a continuous annealing furnace capable of providing stable transportation of a metallic strip and making service life longer, and a manufacturing method of the hearth roll for the continuous annealing furnace.SOLUTION: A hearth roll for a continuous annealing furnace comprises: a cylindrical outer layer sleeve 2 made of heat resistant steel; and a cylindrical inner layer sleeve 3 which is made of a metal having thermal conductivity higher than that of the outer layer sleeve 2 and containing copper, and of which the outer peripheral surface is joined to an inner peripheral surface of the outer layer sleeve 2. An angle θformed by a free edge of an axial direction end part of the outer layer sleeve 2 and a joint boundary 6 between the outer layer sleeve 2 and the inner layer sleeve 3, and an angle θformed by a free edge of an axial direction end part of the inner layer sleeve 3 and the joint boundary 6, satisfy formula (1) and one of formula (2) and formula (3). θ+θ=180° ±10° ...(1), 55°≤θ≤80° ...(2), 125°≤θ<180° ...(3).SELECTED DRAWING: Figure 3

Description

  The present invention relates to a hearth roll for a continuous annealing furnace and a method for manufacturing a hearth roll for a continuous annealing furnace.

  A metal strip work hardened by cold rolling is usually subjected to an annealing (annealing) treatment by heat treatment. In order to improve the workability of the metal strip by removing dislocations by heat treatment, the annealing treatment is inferior in workability such as bending and drawing in the work-hardened state when forming the metal strip with a press or the like. Done. In recent years, high-productivity continuous annealing furnaces are frequently used for annealing metal strips. In a continuous annealing furnace, a plurality of metal strips are annealed continuously while sequentially joining the tail end portion of the coil longitudinal direction and the tip end portion of the next coil delivered from the metal strip coil for a long time. Continuous heat treatment can be performed. Usually, a continuous annealing furnace is composed of a heating zone, a soaking zone and a cooling zone in order from the entrance side of the metal zone, and the temperature is set in each zone according to the heat treatment pattern for the desired annealing treatment. Yes. The metal strip is transported from the heating zone to the cooling zone while changing the plate passing direction in order from the heating zone to the cooling zone by a plurality of conveyance rolls installed at the upper and lower portions of each zone in the furnace.

  Here, taking the continuous annealing treatment of a thin steel plate as an example, in the heating zone, a heat treatment is performed in which the thin steel plate is heated from a normal temperature state to a maximum temperature of about 600 ° C. to 800 ° C. during conveyance. Next, in the soaking zone, soaking is performed near the temperature heated in the heating zone. Further, in the cooling zone, the cooling process is performed until the temperature of the thin steel plate becomes 100 ° C. or less by stepwise temperature pattern setting.

  At this time, the transport roll (hereinafter referred to as “hearth roll”) provided in the furnace for transporting the thin steel sheet is not only heated at the atmospheric temperature of each zone in the furnace, but also the thin steel sheet and the roll temperature. Depending on the temperature difference (generally coincides with the ambient temperature), it is heated or cooled by heat input or heat removal by contact. For this reason, the hearth roll has a temperature distribution in the roll axis direction, and the roll surface changes to a concave shape or a convex shape. When such a roll surface shape change occurs, if the roll surface is concave, the meandering phenomenon of the thin steel sheet, and if the roll surface is convex, the buckling phenomenon of the thin steel sheet (this is a phenomenon in which wrinkle-like wrinkles occur, hereinafter referred to as squeezing). ) Is likely to occur. In response to these phenomena, in actual operations, measures have been taken to reduce changes in roll shape by empirically reducing the sheet feeding speed, which is a major factor in reducing productivity. In recent years, tin gauges used in beverage cans and the like are becoming thinner, and it is important to improve the heat treatment productivity in a continuous annealing furnace by increasing the speed in order to reduce the cost.

  As a method for suppressing the profile change due to the thermal expansion of the hearth roll, a technique for relaxing the temperature distribution in the roll axis direction using a hearth roll for a continuous annealing furnace as a multilayer structure has been proposed (for example, Patent Document 1). The technique of Patent Document 1 is to join an outer layer sleeve made of heat-resistant steel to an inner layer sleeve made of a metal material having higher thermal conductivity than the outer layer sleeve, promote axial heat conduction, and increase the temperature of the entire roll. Distribution, and hence the change in roll thermal expansion profile, can be mitigated. As a method of manufacturing a hearth roll having such a function, a technique (for example, Patent Document 2) in which a high thermal conductive material is melted and bonded has been proposed. Further, a technique (for example, Patent Document 3) is proposed in which an outer layer sleeve made of heat-resistant steel is manufactured by centrifugal casting technology, and then an inner layer sleeve is formed by casting a metal material having high thermal conductivity on the inner surface by centrifugal casting. ing.

Japanese Patent Laid-Open No. 62-127428 Japanese Patent Laid-Open No. 4-247821 JP-A-6-615

By the way, the multi-layered hearth rolls of Patent Documents 1 to 3 are mainly focused on improving a large temperature distribution that occurs in the roll axis direction, and are produced by combining and using metals having different physical properties. No mention is made of the lifetime of the bonding interface.
In a dissimilar material joint in which different materials are joined, when the external force or temperature changes due to material discontinuity on the interface, the stress field is elastic in the vicinity of the joint end (dissimilar material interface end) where the joint interface intersects the free edge. It may show peculiarities that are infinite. When such specificity is exhibited, the strength of the joined body is significantly reduced.

  In other words, the multi-layered hearth rolls of Patent Documents 1 to 3 do not take into account the stress singularity at the edge of the different material interface. In some cases, extremely large stress acts on the edge. In such a case, the bonding interface is peeled off, and the desired soaking effect cannot be obtained. This causes the meandering and squeezing phenomenon of the metal band being transported, which makes stable transport impossible. was there. There is also a problem that the life of the hearth roll is shortened.

  Accordingly, the present invention has been made in view of the above-described circumstances, and enables the continuous conveyance of the metal strip and the extension of the life of the continuous hearth furnace and the hearth for the continuous annealing furnace. It aims at providing the manufacturing method of a roll.

According to one aspect of the present invention, a cylindrical outer layer sleeve made of heat-resistant steel and a metal having a higher thermal conductivity than that of the outer layer sleeve and made of copper, the outer peripheral surface is joined to the inner peripheral surface of the outer layer sleeve. A cylindrical inner layer sleeve, and an angle θ ₁ formed by a free edge of an axial end portion of the outer layer sleeve with respect to the joint interface between the outer layer sleeve and the inner layer sleeve, and the above with respect to the joint interface. The angle θ ₂ formed by the free edge at the axial end of the inner sleeve satisfies the formula (1) and satisfies either the formula (2) or the formula (3). Hearth rolls are provided.
θ ₁ + θ ₂ = 180 ° ± 10 ° (1)
55 ° ≦ θ ₁ ≦ 80 ° (2)
125 ° ≦ θ ₁ <180 ° (3)

According to one aspect of the present invention, a cylindrical outer layer sleeve made of heat-resistant steel, a cylindrical inner layer sleeve having higher thermal conductivity than the outer layer sleeve, and an outer peripheral surface joined to the inner peripheral surface of the outer layer sleeve; A sleeve processing step of machining an axial end portion of a cylindrical sleeve having a multi-layer structure, and an ASKUL joining step of joining the axial end of the outer sleeve to the ASKUL after the sleeve processing step. In the sleeve processing step, an angle θ ₁ formed by a free edge of an axial end portion of the outer layer sleeve with respect to a joining interface between the outer layer sleeve and the inner layer sleeve, and an axis of the inner layer sleeve with respect to the joining interface The outer sleeve and the inner sleeve so that the angle θ ₂ formed by the free edge at the direction end satisfies the formula (1) and satisfies either the formula (2) or the formula (3). The manufacturing method of the hearth roll for continuous annealing furnaces characterized by shape | molding the edge part of the axial direction of this is provided.

  According to one aspect of the present invention, there is provided a hearth roll for a continuous annealing furnace and a method for manufacturing a hearth roll for a continuous annealing furnace that enable stable conveyance of a metal strip and increase the life. .

It is sectional drawing which shows the hearth roll which concerns on one Embodiment of this invention. It is the II sectional view taken on the line of FIG. It is a fragmentary sectional view showing a hearth roll. It is a fragmentary sectional view showing a hearth roll. It is a schematic diagram which shows the dissimilar-material interface edge in a dissimilar-material joined body. It is a graph which shows the appearance and disappearance conditions of stress specificity in a dissimilar material joined body. It is a graph which shows the change with respect to the temperature of the transverse elastic modulus of the heat resistant steel used for the outer layer sleeve of a hearth roll, and the copper used for an inner layer sleeve.

  In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without such specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.

<Configuration of Hearth Roll>
First, with reference to FIGS. 1-4, the structure of the hearth roll 1 which concerns on one Embodiment of this invention is demonstrated. As shown in FIG. 1, which is a cross section passing through the rotation center axis, the hearth roll 1 includes an outer layer sleeve 2, an inner layer sleeve 3, an axle 4, and a shaft portion 5. Further, the hearth roll 1 is used in a continuous annealing furnace in which a metal strip to be heat-treated is a thin steel plate. In such a continuous annealing furnace, excessive force is not required because a large force is not applied to the hearth roll 1 during sheet passing. Further, it is necessary to reduce the rotational inertia in order to cope with the change in the plate passing speed in accordance with the mechanical characteristics and the plate dimensions for each metal band. For this reason, the inside of the hearth roll 1 is hollow.

  The outer layer sleeve 2 has a hollow cylindrical shape and is made of heat resistant steel. The heat resistant steel used for the outer layer sleeve 2 is 25Cr-24Ni steel, has a longitudinal elastic modulus of 214 GPa and a Poisson's ratio of 0.3. The thickness of the outer layer sleeve 2 is, for example, about 15 mm to 30 mm, and is appropriately set according to the temperature conditions, strength conditions, equipment conditions (for example, motor output), and the like. Also, the outer sleeve 2 has a surface whose outer diameter on the center side in the axial direction (left-right direction in FIG. 1) is smaller than the outer diameter on the end side in the axial direction in order to suppress the meandering of the metal strip in the through plate. It has a large convex crown shape. As the convex crown shape, an appropriate crown shape is adopted according to the size of the metal band to be annealed and the position in the furnace where the hearth roll 1 is provided.

  The inner layer sleeve 3 has a hollow cylindrical shape whose diameter is smaller than that of the outer layer sleeve 2, and is made of pure copper such as tough pitch copper, deoxidized copper, oxygen-free copper, or the like. Pure copper used for the inner layer sleeve 3 has a longitudinal elastic modulus of 118 GPa and a Poisson's ratio of 0.34. The thickness of the inner layer sleeve 3 is, for example, about 10 mm to 20 mm, and is appropriately set according to the strength condition, facility condition, etc. of the hearth roll 1. In addition, when the thickness of the inner layer sleeve 3 is as thin as less than 10 mm, the soaking effect of the outer layer sleeve 2 may not be sufficiently obtained. Further, when the thickness of the inner layer sleeve 3 is greater than 20 mm, the weight of the hearth roll 1 becomes too heavy, so that the cost for introducing and maintaining the equipment increases. The inner layer sleeve 3 is disposed in the hollow of the outer layer sleeve 2, and the outer peripheral surface is joined to the inner peripheral surface of the outer layer sleeve 2 by metal bonding. The interface between the outer layer sleeve 2 and the inner layer sleeve 3 is also referred to as a bonding interface 6. The joined body composed of the outer layer sleeve 2 and the inner layer sleeve 3 joined to the outer layer sleeve 2 is also referred to as a multi-layered cylindrical sleeve.

FIG. 3 is a partial cross-sectional view showing the end portions in the axial direction of the outer layer sleeve 2 and the inner layer sleeve 3, which are regions surrounded by a broken line in FIG. 1.
An end portion in the axial direction of the outer layer sleeve 2 is formed to be inclined with respect to the joint interface 6 at an angle θ ₁ formed by a free edge that is an end surface of the end portion in the axial direction of the outer layer sleeve 2. That is, in the example shown in FIG. 3, the outer layer sleeve 2 has a constant thickness on the center side in the axial direction, and an inclined region inclined at an angle θ ₁ formed from the end of the joining interface 6 at the axial end is formed. The The outer layer sleeve 2 is formed with a region having a constant thickness thinner than the center side on the axial end side from the inclined region, and is connected to the axle 4.

On the other hand, the end portion in the axial direction of the inner layer sleeve 3 is formed so as to be inclined with respect to the joint interface 6 at an angle θ ₂ formed by a free edge that is an end surface of the end portion in the axial direction of the inner layer sleeve 3. That is, the inner sleeve 3 has a constant thickness on the center side in the axial direction, and an inclined region inclined at an angle θ ₂ formed by the end face toward the end of the bonding interface 6 is formed at the end in the axial direction.
Further, in the present embodiment, the angles θ ₁ and θ ₂ formed satisfy the following expression (1), and also satisfy the expressions (2) and (3).
θ ₁ + θ ₂ = 180 ° ± 10 ° (1)
55 ° ≦ θ ₁ ≦ 80 ° (2)
125 ° ≦ θ ₁ <180 ° (3)

The example illustrated in FIG. 3 is a case where the angles θ ₁ and θ ₂ formed under the above conditions satisfy the expressions (1) and (3). On the other hand, when the angles θ ₁ and θ ₂ formed satisfy the expressions (1) and (2), the sectional shapes of the axial end portions of the layer sleeve 2 and the inner layer sleeve 3 are as in the example illustrated in FIG. Become. As shown in FIG. 4, when the angles θ ₁ and θ ₂ formed satisfy the expressions (1) and (2), the inclination directions in the inclination regions of the outer sleeve 2 and the inner sleeve 3 are changed.

Here, with respect to the outer layer sleeve 2 and the inner layer sleeve 3 having different physical properties, the shape of the end portions in the axial direction of the outer layer sleeve 2 and the inner layer sleeve 3 is as described above from the viewpoint of peculiarities at the joining end portions. It was found that the lifespan of the hearth roll 1 can be extended by prescribing.
Regarding the conditions for the appearance and disappearance of stress singularities at the dissimilar material interface edge, Kubo et al. (Kubo, “Geometric conditions of dissimilar material joint ends to eliminate free edge stress singularity”, JSME Proceedings (A), Japan Society of Mechanical Engineers, 1991, 57, 535, p. 632-636). According to this finding, a material 7A having an opening angle of θ ₁ and a material 7B having an opening angle of θ ₂ at a point T as shown in FIG. 5 are joined on a line of θ = 0. In this case, the transition condition of the appearance and disappearance of the stress singularity at the edge portion of the dissimilar material interface is expressed by equation (4). In Equation (4), J is defined by Equation (5), J ₀ is defined by Equation (6), s ₁ and s ₂ are defined by Equation (7), and t ₁ and t ₂ are defined by Equation (8). (J = 1, 2). Moreover, (alpha) in (2) Formula and (3) Formula is defined by (9) Formula, (beta) is defined by (10) Formula. Furthermore, κ ₁ and κ ₂ in the equations (9) and (10) are defined by the equation (11) under the plane strain condition (j = 1, 2). Further, μ ₁ and μ ₂ in the equations (9) and (10) are transverse elastic coefficients of the materials 7A and 7B, and the longitudinal elastic coefficients E ₁ and E _{2 of} the materials 7A and 7B and the Poisson's ratio ν ₁ , It is defined by equation (12) using ν ₂ (j = 1, 2).

That is, the stress field at the dissimilar material interface end changes in specificity depending on the shape of the joint end and the elastic constant (longitudinal elastic modulus, Poisson's ratio) of the material, and the distribution form and magnitude of the stress change. Then, by selecting an appropriate combination of material characteristics and end shape, the specificity can be lost.
Based on such knowledge, the present inventors examined the peculiarity of stress at the dissimilar material interface ends of the outer sleeve 2 and the inner sleeve 3. In this study, for the outer layer sleeve 2 and the inner layer sleeve 3 having the shape shown in FIG. 3 or FIG. 4, the values of the angles θ ₁ and θ ₂ that are the shapes of the dissimilar material interface ends, and the lateral elastic modulus μ ₁ , μ of the material The value of ₂ was changed to verify the appearance and disappearance of specificity. In the present study, in order to prevent macro stress concentration, the dissimilar material interface ends are formed in a straight and smoothly continuous shape, and thus the angles θ ₁ and θ ₂ formed satisfy the equation (13). .
θ ₁ + θ ₂ = 180 ° (13)

The result of this study is shown in the graph of FIG. In FIG. 6, the horizontal axis indicates the value of the transverse elastic ratio μ ₂ / μ ₁ , which is the ratio of the lateral elastic modulus μ ₂ of the inner layer sleeve 3 to the lateral elastic coefficient μ ₁ of the outer layer sleeve 2, and the vertical axis indicates the value of the angle θ ₁ formed. . In FIG. 6, the shaded area is a condition in which stress singularity appears at the dissimilar material interface edge. Under this area condition, a very large stress acts near the end of the bonding interface 6. It becomes. On the other hand, the region not shaded is a condition in which the peculiarity of stress disappears at the edge of the dissimilar material interface. Under the condition of this region, a large stress does not act near the end of the joint interface 6. That is, in the graph of FIG. 6, the life of the hearth roll 1 can be extended by controlling the shape of the dissimilar material interface edge so as to satisfy the condition of the region that is not shaded.

FIG. 7 shows the temperature dependence of the transverse elastic coefficients μ ₁ and μ ₂ of the heat-resistant steel used for the outer layer sleeve 2 and the copper used for the inner layer sleeve 3 in the present embodiment. Further, in FIG. 7 shows the transverse elasticity ratio μ _{2 /} μ ₁ of the temperature dependence, which is calculated by dividing the modulus of transverse elasticity mu ₂ of copper modulus of transverse elasticity mu ₁ of heat-resistant steel. It can be confirmed that the transverse elastic ratio μ ₂ / μ ₁ in the temperature range from room temperature to 800 ° C. used in the continuous annealing furnace is in the range of 0.6 to 0.8.

Furthermore, from the range of the transverse elastic ratio and the examination result shown in FIG. 6, the condition for eliminating the peculiarity of stress at the interface between different materials in the outer sleeve 2 and the inner sleeve 3 of the present embodiment is the condition of the equation (13). In addition to the above, it is necessary that the angle θ ₁ formed satisfies the condition of either the expression (2) or the expression (3). By satisfying this condition, the stress acting on the dissimilar material interface end between the outer sleeve 2 and the inner sleeve 3 can be greatly reduced, so that the outer sleeve 2 and the inner sleeve 3 are separated from each other at the axial end. The life of the hearth roll 1 can be extended. As for the condition of the sum of the angle θ ₁ and the angle θ ₂ formed, even if the condition of the expression (13) is expanded to the range of the condition of the expression (1), it is the same as the case of the expression (13). A stress suppressing effect can be obtained. Further, by setting the condition of the expression (1) instead of the expression (13), the processing of the end portions of the outer layer sleeve 2 and the inner layer sleeve 3 described later becomes easy.

And the ASKUL 4 is a substantially frustoconical member and is made of a metal such as refractory steel. The ASKUL 4 is disposed on both axial sides of the outer layer sleeve 2, one end in the axial direction is joined to the end portion of the outer layer sleeve 2 by welding, and the other end is joined to the shaft portion 5 by welding. In FIG. 1, the joining position between the outer sleeve 2 and the axle 4 is indicated by a broken line a, and the joining position between the axle 4 and the shaft portion 5 is indicated by a broken line b.
The shaft portion 5 is a member extending in the axial direction of the outer layer sleeve 2 and is made of a metal such as refractory steel. The shaft portions 5 are respectively arranged on both end sides of the outer layer sleeve 2, and one end in the extending direction is joined to the axle 4.

<Manufacturing method of hearth roll>
Next, the manufacturing method of the hearth roll 1 which concerns on this embodiment is demonstrated. First, the outer sleeve 2 having a rough shape is manufactured by means such as centrifugal casting, and finished to a predetermined dimension by machining such as cutting (sleeve manufacturing process). In the sleeve manufacturing process, the inner layer sleeve 3 is manufactured by the same method as the outer layer sleeve 2.
Next, the inner layer sleeve 3 is arranged inside the outer layer sleeve 2 and subjected to hot isostatic pressing (HIP process), thereby joining the outer layer sleeve 2 and the inner layer sleeve 3 to form a multi-layered cylindrical sleeve. Manufacture (sleeve joining process). In the HIP process, the outer layer sleeve 2 and the inner layer sleeve 3 arranged inside the outer layer sleeve 2 are placed in a high-pressure container, and the high-temperature and high-pressure process is performed to connect the outer layer sleeve 2 and the inner layer sleeve 3 to each other at the bonding interface 6. Combine.

Furthermore, the axial end portion of the cylindrical sleeve having a multilayer structure in which the outer sleeve 2 and the inner sleeve 3 are joined is machined into a desired shape that satisfies the above-described conditions (sleeve processing step).
After that, the axial end of the machined outer layer sleeve 2 and the ASKUL 4 in which the shaft portion 5 is previously bonded by welding are bonded by means such as laser welding (ASKUL bonding process).
Next, the surface of the outer layer sleeve 2 to which the ASKUL 4 is joined is cylindrically ground to ensure roundness (grinding process). In the grinding process, the outer sleeve 2 is ground so that the surface of the outer sleeve 2 has the above-described convex crown shape.
Through the above steps, the hearth roll 1 according to this embodiment can be manufactured.

<Modification>
Although the present invention has been described above with reference to specific embodiments, it is not intended that the present invention be limited by these descriptions. From the description of the invention, other embodiments of the invention will be apparent to persons skilled in the art, along with various variations of the disclosed embodiments. Therefore, it is to be understood that the claims encompass these modifications and embodiments that fall within the scope and spirit of the present invention.

For example, in the above embodiment, the heat resistant steel used for the outer sleeve 2 is 25Cr-24Ni steel, but the present invention is not limited to such an example. The heat resistant steel may be of other commonly used component systems. Although pure copper is used for the inner layer sleeve 3, the present invention is not limited to such an example. The inner layer sleeve 3 may be another metal containing copper such as a copper alloy as long as the thermal conductivity is higher than that of the outer layer sleeve 2. In addition, when the shape of the dissimilar material interface end is defined by the formula (2) or (3), the transverse elastic ratio between the material of the outer sleeve 2 and the material of the inner sleeve 3 in the temperature range used in the continuous annealing furnace Each material is selected so that μ ₂ / μ ₁ is 0.6 or more and 0.8 or less.

Moreover, in the said embodiment, although it was set as the structure which joins the outer-layer sleeve 2 and the inner-layer sleeve 3 using a HIP process, this invention is not limited to this example. The outer layer sleeve 2 and the inner layer sleeve may be formed using other methods such as multi-stage casting using a centrifugal casting method or multi-layering by fitting.
Furthermore, in the said embodiment, although the metal strip was a thin steel plate, this invention is not limited to this example. As long as the metal strip is processed in a continuous annealing furnace, the metal strip may be different in material and thickness.

<Effect of embodiment>
(1) A hearth roll 1 for a continuous annealing furnace according to an aspect of the present invention is a cylindrical outer layer sleeve 2 made of heat-resistant steel, and has a higher thermal conductivity than the outer layer sleeve 2 and is made of a metal containing copper, A cylindrical inner layer sleeve 3 whose outer peripheral surface is joined to the inner peripheral surface of the outer layer sleeve 2, and the axial end portion of the outer layer sleeve 2 is free from the joining interface 6 between the outer layer sleeve 2 and the inner layer sleeve 3. The angle θ ₁ formed by the edge and the angle θ ₂ formed by the free edge at the axial end portion of the inner sleeve 3 with respect to the joining interface 6 satisfy the expression (1) and satisfy the expression (2) or (3). Satisfy either one.

  According to the configuration of (1) above, the peculiarity that the stress field becomes infinite in terms of elasticity disappears in the vicinity of the dissimilar material interface end (the axial end of the bonding interface 6) between the outer sleeve 2 and the inner sleeve 3. Therefore, the stress generated in the vicinity of the dissimilar material interface end due to thermal stress or the like can be reduced. For this reason, peeling of the bonding interface 6 can be prevented, and a soaking effect due to multilayering can be obtained over a long period of time, so that the metal strip can be stably conveyed. In addition, since the peeling of the bonding interface 6 can be prevented, the life of the hearth roll 1 can be extended.

(2) In the configuration of (1), the inner layer sleeve 3 is made of pure copper.
According to the configuration of (2) above, since the thermal conductivity of the inner sleeve 3 is increased, a higher soaking effect can be obtained and the weight of the inner sleeve 3 can be reduced.
(3) The manufacturing method of the hearth roll 1 for a continuous annealing furnace according to one aspect of the present invention has a cylindrical outer layer sleeve 2 made of heat-resistant steel and a higher thermal conductivity than the outer layer sleeve 2. A sleeve processing step for machining an axial end portion of a cylindrical sleeve having a multilayer structure having a cylindrical inner layer sleeve 3 whose outer peripheral surface is joined to the inner peripheral surface, and a shaft of the outer sleeve 2 after the sleeve processing step And an askle joining step for joining the end in the direction and the askle 4. In the sleeve processing step, the free edge at the axial end of the outer sleeve 2 forms the joining interface 6 between the outer sleeve 2 and the inner sleeve 3. The angle θ ₁ and the angle θ ₂ formed by the free edge at the axial end of the inner sleeve 3 with respect to the joining interface 6 satisfy the expression (1) and either the expression (2) or the expression (3) Meet the outer layer The end portions in the axial direction of the tube 2 and the inner layer sleeve 3 are formed.
According to the configuration of the above (3), the same effect as the above (1) can be obtained.

(4) In the configuration of (3), a sleeve joining step of joining the outer peripheral surface of the inner sleeve 3 to the inner peripheral surface of the outer sleeve 2 using a hot isostatic pressing process is further performed before the sleeve processing step. Prepare.
According to the configuration of (4) above, the outer layer sleeve 2 and the inner layer sleeve 3 can be formed by using hot isostatic pressing without causing voids or an alloy layer having low thermal conductivity at the bonding interface 6. Can be joined. For this reason, compared with the other method used when manufacturing the cylindrical sleeve of a multilayer structure, a high soaking | uniform-heating effect can be acquired.

Next, examples performed by the present inventors will be described. In the examples, the hearth roll 1 according to the above embodiment, which was assumed to be introduced into the heating zone of a continuous annealing furnace that performs the annealing treatment of the steel strip, was manufactured, and the effect was verified.
In the embodiment, first, in order to simulate the body portion of the hearth roll 1, an inner layer sleeve 3 made of cylindrical copper (pure copper) is arranged inside the outer layer sleeve 2 made of cylindrical heat resistant steel (25Cr-20Ni steel). A cylindrical sleeve having a multilayer structure was prepared by performing the HIP process in a vacuum at 1000 ° C. The outer layer sleeve 2 of heat resistant steel has a body length of 400 mm, an outer diameter of 350 mm, and a wall thickness of 15 mm. The copper inner layer sleeve 3 has a body length of 400 mm, an outer diameter of 320 mm, and a wall thickness of 10 mm. Next, the multi-layered cylindrical sleeve was cut to a length of 50 mm in the axial direction, and the test piece with the angle of the interface between the dissimilar materials adjusted was created by machining the end face of the heat-resistant steel and copper. did.

  And the test which heat-processes about the created test piece was implemented. In the heat treatment test, the test piece was heated from room temperature to 800 ° C. in an electric heating furnace in a nitrogen atmosphere, and then the heated test piece was subjected to soaking for 1 hour. Subsequently, the power source of the heating furnace was stopped to cool the test piece. Furthermore, about the sample after cooling, the presence or absence of the crack of a dissimilar material interface edge was confirmed. As a result of confirmation, when there was a crack, the test was terminated. On the other hand, as a result of confirmation, when there was no crack, after again applying a heat cycle (heat treatment) from heating to cooling, it was confirmed whether there was a crack at the interface edge of the dissimilar material. The application of the thermal cycle and the confirmation of the crack were repeated in the range of a maximum of 10 thermal cycles until the crack was confirmed.

Table 1 shows the end shape of the test piece used in the test and the result of the test. As an example, a condition in which the formed angles θ ₁ and θ ₂ satisfy the expressions (1) and (3) is defined as example 1, and a condition that satisfies the expressions (1) and (2) is defined as example 2. . Moreover, in the Example, it tested as a comparative example also about the conditions which angle (theta) ₁ and (theta) ₂ made in an edge part shape do not satisfy | fill the conditions of the said embodiment. As a comparative example, a condition in which the angles θ ₁ and θ ₂ formed do not satisfy the expressions (1), (2), and (3) is set as the comparative example 1, the expression (1) is satisfied, and the expression (2) And the conditions which do not satisfy | fill either of (3) Formula were made into Comparative Examples 2-4.

As a result of the test, it was confirmed in Comparative Example 1 that did not satisfy the condition of the expression (1) that a crack occurred at the interface edge of the dissimilar material after one heat treatment. Moreover, in the conditions of Comparative Examples 2 to 4, the number of heat treatments until the cracks were generated increased compared with Comparative Example 1 by satisfying the condition of the expression (1), but the number of heat treatments within 6 times in any condition. It was confirmed that cracks occurred.
On the other hand, in the conditions of Examples 1 and ₂ that satisfy the conditions of the angles θ ₁ and θ ₂ formed in the above embodiment, it was confirmed that cracks did not occur even when heat treatment was performed 10 times.

  That is, according to the hearth roll 1 according to the present invention, it is confirmed that the stress generated at the interface between the different materials can be prevented, so that the bonding interface 6 can be prevented from being peeled off and the soaking effect due to the multi-layering can be obtained over a long period of time. It was. For this reason, the metal belt can be stably conveyed and the life of the hearth roll 1 can be extended.

DESCRIPTION OF SYMBOLS 1 Hearth roll 2 Outer layer sleeve 21 1st area | region 22 2nd area | region 3 Inner layer sleeve 4 ASKUL 5 Shaft part 6 Joining interface

Claims (4)

A cylindrical outer sleeve made of heat-resistant steel;
A cylindrical inner layer sleeve having higher thermal conductivity than the outer layer sleeve, made of a metal containing copper, and having an outer peripheral surface joined to an inner peripheral surface of the outer layer sleeve;
With
An angle θ ₁ formed by the free edge of the axial end of the outer sleeve with respect to the joining interface between the outer sleeve and the inner sleeve, and a free edge of the axial end of the inner sleeve with respect to the joining interface The hearth roll for a continuous annealing furnace characterized in that the formed angle θ ₂ satisfies the formula (1) and satisfies either the formula (2) or the formula (3).
θ ₁ + θ ₂ = 180 ° ± 10 ° (1)
55 ° ≦ θ ₁ ≦ 80 ° (2)
125 ° ≦ θ ₁ <180 ° (3)   The hearth roll for a continuous annealing furnace according to claim 1, wherein the inner layer sleeve is made of pure copper. A multi-layered cylindrical sleeve comprising: a cylindrical outer layer sleeve made of heat-resistant steel; and a cylindrical inner layer sleeve having higher thermal conductivity than the outer layer sleeve and having an outer peripheral surface joined to the inner peripheral surface of the outer layer sleeve. A sleeve machining process for machining the axial end;
After the sleeve processing step, an ASKUL joining step of joining the axial end of the outer layer sleeve and the ASKUL, and
In the sleeve processing step, an angle θ ₁ formed by a free edge of an axial end of the outer layer sleeve with respect to a joining interface between the outer layer sleeve and the inner layer sleeve, and an axial direction of the inner layer sleeve with respect to the joining interface angle theta ₂ formed by the free edge of the end portion, satisfies the equation (1), and (2) or (3) so as to satisfy any one of expressions, the outer sleeve and the axial end of the inner sleeve A method for producing a hearth roll for a continuous annealing furnace, characterized by forming a part.
θ ₁ + θ ₂ = 180 ° ± 10 ° (1)
55 ° ≦ θ ₁ ≦ 80 ° (2)
125 ° ≦ θ ₁ <180 ° (3)   4. The sleeve joining step of joining the outer peripheral surface of the inner layer sleeve to the inner peripheral surface of the outer layer sleeve using a hot isostatic pressing process before the sleeve processing step. The manufacturing method of the hearth roll for continuous annealing furnaces of description.

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