JP2022125490A - Induction heating furnace and manufacturing method thereof - Google Patents

Abstract

To provide an induction heating furnace and a manufacturing method thereof that can extend the life of a heat-resistant member by enabling removal of oxide scale adhering to the heat-resistant member.SOLUTION: A manufacturing method of a heat-resistant member 2 which is composed of a cylindrical member extending in a horizontal direction and configured such that a billet 4 as an object to be heated can pass through the inner peripheral surface side includes a manufacturing step of molding and hardening the heat-resistant member 2 from concrete or ceramics, and then a coating step of applying a heat-resistant paint to at least a part of the inner peripheral surface of the heat-resistant member 2 to form a coating film portion 7.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an induction heating furnace for heating billets and a method for manufacturing a heat-resistant member installed in the induction heating furnace. It is about.

Various induction heating furnaces have been proposed (see Patent Document 1, for example). Patent Literature 1 discloses an induction heating furnace equipped with an air injection nozzle. In this induction heating furnace, after the plate-shaped object to be heated has passed, air is injected from the air injection nozzle, so that the oxide scale that has fallen inside the heat-resistant member can be blown off and removed.

However, in induction heating furnaces that target billets as objects to be heated, air injection nozzles cannot be used. A heat-resistant member in an induction heating furnace, in which a cylindrical billet is transported in its axial direction, has a relatively small opening and is relatively long in the transport direction. Therefore, the air injected from the air injection nozzle did not reach the inside of the heat-resistant member, and the oxide scale could not be removed.

Inside the induction heating furnace, the billets are conveyed by pushing the preceding billet with the subsequent billet. A plurality of billets are continuously supplied to an induction heating furnace and heated. Since the billet was not interrupted inside the induction heating furnace, there was no opportunity to inject air from the air injection nozzle. If air is injected while the billet is inside the induction heating furnace, the temperature of the billet inside the induction heating furnace drops. Since the billet is partially cooled by the jetted air, the quality of the forged product is degraded. Oxidized scale could not be removed in an induction heating furnace for heating billets.

In the induction heating furnace for heating the billet, it was difficult to achieve a long service life of the heat-resistant member because the oxide scale adhering to the heat-resistant member could not be efficiently removed.

Japanese Patent Publication No. 2000-003779

The present invention has been made in view of the above problems, and an object of the present invention is to enable the removal of oxide scale adhering to the heat-resistant member, thereby realizing a longer life of the heat-resistant member, and the production of the heat-resistant member. to provide a method.

An induction heating furnace for achieving the above object is composed of a cylindrical member extending in a horizontal direction, and a heat-resistant member formed so that a billet, which is an object to be heated, can pass through the inner peripheral surface side. and a heating coil arranged on the outer peripheral surface side of the heat-resistant member, wherein the heat-resistant member is made of concrete or ceramics, and at least a part of the inner peripheral surface is formed of heat-resistant paint. It is characterized by having a coating film portion.

A method for manufacturing a heat-resistant member for achieving the above object is a heat-resistant member which is composed of a cylindrical member extending in a horizontal direction and configured so that a billet, which is an object to be heated, can pass through the inner peripheral surface side. In the member manufacturing method, a manufacturing step of molding and hardening the heat-resistant member from concrete or ceramics, and then applying a heat-resistant paint to at least a part of the inner peripheral surface of the heat-resistant member to form a coating film portion. and a coating step.

According to the present invention, the inner peripheral surface of the heat-resistant member can be made smooth by arranging the coating film portion. After the heat-resistant member is cooled, it becomes possible to easily remove the oxide scale adhering to the inner peripheral surface of the heat-resistant member. This is advantageous for achieving longer life of heat-resistant members.

It is explanatory drawing which illustrates an induction heating furnace in a cross section. It is an explanatory view illustrating a cylindrical heat-resistant member in a perspective view. It is an explanatory view illustrating a heat-resistant member having an inclined portion in a perspective view. FIG. 3 is an explanatory diagram illustrating an AA arrow view of FIG. 2; It is explanatory drawing which illustrates the state where an oxide scale is removed from a heat-resistant member. FIG. 3 is an explanatory diagram illustrating a modification of the heat-resistant member of FIG. 2; FIG. 7 is an explanatory diagram illustrating the BB arrow view of FIG. 6; FIG. 8 is an explanatory diagram illustrating an enlarged example of a coating film portion and a heat-resistant sheet in FIG. 7 ; FIG. 9 is an explanatory diagram illustrating a modification of FIG. 8;

Hereinafter, an induction heating furnace and a method for manufacturing a heat-resistant member will be described based on embodiments shown in the drawings. In the drawing, the extending direction of the cylindrical heat-resistant member is indicated by the arrow x, the width direction perpendicular to the extending direction x is indicated by the arrow y, and the vertical direction is indicated by the arrow z.

As illustrated in FIG. 1 , an induction heating furnace 1 includes a cylindrical heat-resistant member 2 extending in the horizontal direction, and a heating coil 3 arranged on the outer peripheral surface side of the heat-resistant member 2 . A passage 5 is formed on the inner peripheral surface side of the heat-resistant member 2 as a space for allowing a billet 4 to be heated to pass through. A skid rail 6 consisting of a pair of rod-shaped members for supporting the billet 4 from below, for example, is arranged in the passage 5 . The induction heating furnace 1 of the present invention is not limited to the configuration provided with the skid rails 6 . At least the passage 5 formed on the inner peripheral surface side of the heat-resistant member 2 and capable of conveying the billet 4 may be provided.

In this embodiment, the induction heating furnace 1 is composed of three units 1a, 1b, and 1c along the extending direction x of the heat-resistant member 2. As shown in FIG. The three units 1a-1c are configured to be separable from each other along the extending direction x.

As illustrated in FIG. 2, the heat-resistant members 2a arranged in the first unit 1a and the second unit 1b are formed in a cylindrical shape. The heat-resistant member 2a may be formed in a shape other than the cylindrical shape, such as a square tube shape. As illustrated in FIG. 3, the heat-resistant member 2b arranged in the third unit 1c is formed in a shape having an inner peripheral surface that widens downward toward the outlet of the induction heating furnace 1. As shown in FIG. This heat-resistant member 2b has an inclined portion for conveying the billet 4 with a downward inclination.

The heat-resistant member 2 is made of concrete, for example. In this specification, concrete means a mixture of cement with coarse aggregate such as gravel and water, a mixture of cement with water (cement paste), and a mixture of cement with fine aggregate such as sand ( It is a concept that also includes mortar. Concrete may contain well-known additives and the like.

The heat-resistant member 2 may be made of ceramics. In this specification, the term "ceramics" is a concept that includes materials obtained by mixing silicon carbide, alumina (aluminum oxide), etc. with water, as well as materials obtained by mixing aggregates. Ceramics may contain well-known additives and the like.

As illustrated in FIGS. 2 and 3, a coating film portion 7 is arranged on the inner peripheral surface of the heat-resistant member 2 . The coating film portion 7 is formed by applying heat-resistant paint to the inner peripheral surface of the heat-resistant member 2 . The coating film portion 7 is made of, for example, a heat-resistant paint containing zirconia (zirconium dioxide) as a main component.

The configuration of the coating film portion 7 is not limited to the above. The coating film portion 7 may have a heat resistant temperature that can withstand the temperature rise in the induction heating furnace 1 . For example, a heat resistant paint having a heat resistant temperature of 1300° C. is used. For example, the coating film portion 7 can be made of a heat-resistant paint containing silicon, silica, alumina (aluminum oxide), or a mixture thereof as a main component. The coating film portion 7 may be composed of a heat-resistant paint whose main component is a mixture containing zirconia. The main component of the heat-resistant paint used for forming the coating film portion 7 can be appropriately selected according to the temperature of the billet 4 heated in the induction heating furnace 1 .

The heat-resistant paint may have a structure capable of reducing the surface roughness of the inner peripheral surface of the heat-resistant member 2 by being applied. The coating film portion 7 is formed by the heat-resistant paint flowing into fine concave portions formed on the inner peripheral surface of the heat-resistant member 2 and by covering the fine convex portions with the heat-resistant paint. The inner peripheral surface of the heat-resistant member 2 can be made smooth by arranging the coating film portion 7 .

FIG. 4 shows a cross section of the cylindrical heat-resistant member 2a in a direction orthogonal to the axial direction (extending direction x) of the heat-resistant member 2a. As illustrated in FIG. 4, the coating film portion 7 is arranged in the vicinity of the lower end of the inner peripheral surface of the heat-resistant member 2a. In this specification, the vicinity of the lower end refers to a range of 45° or less to the left and right of a virtual line extending from the center O of the cylindrical heat-resistant member 2a to the lower end P1 of the inner peripheral surface in FIG. In FIG. 4, for the sake of explanation, a virtual line extending from the center O to the lower end P1 is indicated by a dashed dotted line, and a portion of 45° left and right from the center O is indicated by a broken line. The vicinity of the lower end is the range between the pair of dashed lines. Also, the vicinity of the lower end may be in a range below the center of the heat-resistant member 2 in the vertical direction z. In other words, the vicinity of the lower end may be a range below the virtual line extending in the width direction y from the center O in FIG. The coating film portion 7 may be arranged not only near the lower end of the inner peripheral surface but also on the entire inner peripheral surface. It is desirable that the coating film portion 7 be arranged in a range where the oxide scale generated from the billet 4 can adhere to the inner peripheral surface of the heat-resistant member 2a.

The thickness of the coating film portion 7 is appropriately set. For example, the thickness of the coating film portion 7 is set in the range of 0.1 mm or more and 3.0 mm or less. Since the coating film portion 7 is not intended for a heat resistance effect, there is no problem even if the thickness is set to be relatively thin. As the thickness of the coating film portion 7 is reduced, cracking in the coating film portion 7 due to thermal expansion and contraction can be suppressed. Moreover, peeling of the coating film portion 7 from the heat-resistant member 2 can be suppressed. The thicker the coating film portion 7, the easier it is to hide irregularities on the inner peripheral surface of the heat-resistant member 2 and make the inner peripheral surface smooth. Moreover, it becomes easy to suppress that an oxide scale contacts the heat-resistant member 2 directly.

When manufacturing the heat-resistant member 2, raw materials for concrete or ceramics and water are mixed to prepare unhardened concrete or ceramics. Concrete or the like before hardening is molded into a cylindrical shape or the like and hardened. Hereinafter, the process of manufacturing the heat-resistant member 2 may be referred to as a manufacturing process. Concrete or the like before hardening is poured into a mold or the like and shaped. When the material forming the heat-resistant member 2 is concrete, it is cured by drying. When the material is ceramics, it is sintered by heat treatment.

After the manufacturing process, a heat-resistant paint is applied to at least a part of the inner peripheral surface of the heat-resistant member 2 to form the coating film portion 7 . This process may be hereinafter referred to as a coating process. After the application step, a drying step of drying the coating film portion 7 and a baking step of baking the dried coating film portion 7 at, for example, 800° C. may be performed.

In the induction heating furnace 1 in which the heat-resistant member 2 is installed, the coating film portion 7 may be baked when the billet is heated. Since the manufacturing of the heat-resistant member 2 can be completed by the application step of applying the heat-resistant paint and the drying step of drying the heat-resistant paint, it is advantageous for reducing the manufacturing cost of the heat-resistant member 2 . On the other hand, when performing up to the baking step, the coating film portion 7 can be baked by setting an appropriate heating time and heating rate according to the properties of the heat-resistant paint. This is advantageous for improving the quality of the coating film portion 7 .

FIG. 5 shows a cross section of the heat-resistant member 2a in a direction parallel to the extending direction x of the cylindrical heat-resistant member 2a. When performing maintenance work on the heat-resistant member 2, first, the heat-resistant member 2 is removed from the induction heating furnace 1 after it has cooled sufficiently. As illustrated in the upper part of FIG. 5, the oxide scale 8 adheres to the inner peripheral surface of the heat-resistant member 2a.

When the inner peripheral surface of the heat-resistant member 2a is rubbed with a wire brush such as an iron brush, the oxide scale is separated from the inner peripheral surface. As shown in the lower part of FIG. 5, the oxide scale can be easily removed from the heat-resistant member 2a. Oxidized scale is recovered in powder form. The heat-resistant member 2a is placed in the induction heating furnace 1 with the coating film portion 7 facing downward, and the maintenance work is completed.

Since the heat-resistant member 2 has the coating film portion 7 arranged on the inner peripheral surface, it is possible to easily remove the adhering oxide scale. This is advantageous for realizing a long life of the heat-resistant member 2 .

In a heat-resistant member that does not have the coating film portion 7, the oxide scale flows into and adheres to the unevenness of the inner peripheral surface of the heat-resistant member. Therefore, when trying to remove the oxide scale after cooling the heat-resistant member, it was necessary to scrape off the chisel or the like brought into contact with the oxide scale by hitting it with a hammer. There was a risk that the heat-resistant material would crack due to the impact of the hammer.

In contrast, in the present invention, the coating film portion 7 makes the inner peripheral surface of the heat-resistant member 2 smooth, so that the oxide scale can be easily removed by rubbing with an iron brush or the like. The heat-resistant member 2 is not subjected to impact or the like, and there is no fear of the heat-resistant member 2 being damaged.

In addition, the coating film portion 7 can prevent the oxide scale from coming into direct contact with the heat-resistant member 2 . The coated film portion 7 inhibits the chemical reaction between the oxide scale and the heat-resistant member 2 to firmly bond the oxide scale to the heat-resistant member 2 . Therefore, it becomes easy to remove the oxide scale from the heat-resistant member 2 .

When the main component of the coating film portion 7 is zirconia, the coefficient of thermal expansion of the coating film portion 7 is closer to that of the oxide scale than the heat-resistant member 2 . Therefore, the coating film portion 7 shrinks together with the oxide scale during cooling. The stress exerted on the heat-resistant member 2 from the oxide scale that shrinks during cooling is reduced by the coating film portion 7 . It is possible to suppress the problem that the heat-resistant member 2 is cracked. This is advantageous for realizing a long life of the heat-resistant member 2 .

The coating film portion 7 can be arranged by applying heat-resistant paint. Even in the heat-resistant member 2 formed long in the axial direction, the coating film portion 7 can be easily arranged over the entire axial direction. The range in which the oxide scale can be removed from the heat-resistant member 2 is not affected by the length of the heat-resistant member 2 in the axial direction. The coating film portion 7 can be arranged on the heat-resistant member 2 of any shape to make the oxide scale easy to remove.

After cooling the heat-resistant member 2, the oxide scale can be removed. Unlike the conventional technology in which air is jetted during heating to remove oxidized scale, there is no impact on the product such as a drop in the temperature of the billet.

The coating film portion 7 may be formed on the entire inner peripheral surface of the heat-resistant member 2 . Even if oxide scale scatters and adheres to the upper and side surfaces of the inner periphery of the heat-resistant member 2, the oxide scale can be easily removed.

When returning the cylindrical heat-resistant member 2a to the induction heating furnace 1 after removing the oxide scale, the heat-resistant member 2a can be disposed regardless of the direction. Workability of maintenance work can be improved. In addition, by arranging the heat-resistant member 2a in the induction heating furnace 1 so that the coating film portion 7, which was on the lower side before the maintenance work, is placed on the upper side, the coating film portion 7 is hardly affected by the oxide scale. can be used as the lower side. This is advantageous for suppressing the influence of oxide scale on the heat-resistant member 2 . For example, by rotating the heat-resistant member 2a by 90° around the extension direction x of the heat-resistant member 2a at each maintenance work and placing it in the induction heating furnace 1, the heat-resistant member can be maintained in a good state for a long period of time. 2a can be used. This is extremely advantageous for prolonging the life of the heat-resistant member 2a.

When returning the heat-resistant member 2 to the induction heating furnace 1, the heat-resistant paint may be reapplied. Since the coating film portion 7 can be re-formed, the influence of the oxide scale on the heat-resistant member 2 can be suppressed.

As illustrated in FIGS. 6 and 7, a heat-resistant sheet 9 may be arranged on the inner peripheral surface of the heat-resistant member 2 . An example in which the heat-resistant sheet 9 is arranged on the cylindrical heat-resistant member 2a will be described below, but the heat-resistant sheet 9 can be similarly arranged on the heat-resistant member 2b having an inclined portion.

The heat-resistant sheet 9 is made of, for example, a fabric having a mesh. The heat-resistant sheet 9 can be made of fibers containing alumina and silica as main components, for example. The main component of the heat-resistant sheet 9 is not limited to this, as long as it is made of a material that can withstand high temperatures of 700°C to 1300°C. The main component of the heat-resistant sheet 9 can be appropriately selected according to the temperature of the billet 4 heated in the induction heating furnace 1 . FIG. 6 illustrates a state in which the fabric forming the heat-resistant sheet 9 is partially exposed from the inner peripheral surface of the heat-resistant member 2 . The heat-resistant sheet 9 is not limited to woven fabric. It may be composed of a non-woven fabric.

The heat-resistant sheet 9 is arranged substantially parallel to the extending direction x of the heat-resistant member 2 . It can also be said that the heat-resistant sheet 9 is arranged so as to be substantially parallel to the inner peripheral surface of the heat-resistant member 2 . A configuration in which the heat-resistant sheet 9 is arranged in an inclined state with respect to the extending direction x, such as an upward inclination or a downward inclination along the extending direction x, is not excluded.

As illustrated in FIG. 7, the heat-resistant sheet 9 is arranged in the vicinity of the lower end of the inner peripheral surface of the heat-resistant member 2a. In this embodiment, the heat-resistant sheet 9 is arranged in the same range as the coating film portion 7 is arranged. That is, in FIG. 7, the heat-resistant sheet 9 is arranged within a range of 45° or less to the left and right of an imaginary line extending from the center O of the heat-resistant member 2a to the lower end P1 of the inner peripheral surface. Also, the vicinity of the lower end may be in a range below the center of the heat-resistant member 2 in the vertical direction z. In other words, the vicinity of the lower end may be a range below the virtual line extending in the width direction y from the center O of FIG. The heat-resistant sheet 9 may be arranged not only in the vicinity of the lower end of the inner peripheral surface but also on the entire inner peripheral surface. The range in which the heat-resistant sheet 9 is arranged may be wider than or narrower than the coating film portion 7 .

As shown in FIG. 8, the heat-resistant sheet 9 is partially buried in the concrete or ceramics forming the heat-resistant member 2, and the rest of the heat-resistant sheet 9 is exposed from the concrete or the like. In this embodiment, the heat-resistant sheet 9 is arranged so that most of the heat-resistant sheet 9 is buried in concrete or the like, and a part of the heat-resistant sheet 9 is exposed on the inner peripheral surface side of the heat-resistant member 2 . When the heat-resistant sheet 9 is made of woven fabric, the mesh size d is, for example, 1-10 mm. It is the interval between the threads 9a forming the heat-resistant sheet 9, and the mesh size d is the length from the side end of one thread 9a to the side end of the other thread 9a.

The heat-resistant sheet 9, which is partially embedded in the heat-resistant member 2 and integrated with the heat-resistant member 2, can suppress the occurrence and expansion of cracks in the vicinity of the lower end of the heat-resistant member 2. FIG. The force that tends to expand the crack causes the heat-resistant sheet 9 to generate force in the tensile direction. This makes it easier to avoid the problem of cracks occurring in the heat-resistant member 2 and oxide scale entering into the cracks.

When the coating film portion 7 is arranged on the inner peripheral surface side of the heat-resistant sheet 9 , it is possible to suppress the problem that the oxide scale adheres to the heat-resistant sheet 9 . By combining the heat-resistant sheet 9 and the coating film portion 7, it is possible to suppress the problem that cracks occur in the inner peripheral surface of the heat-resistant member 2 and the coating film portion 7, and oxide scale adheres inside the cracks. Since the generation and growth of cracks can be suppressed, it is advantageous for achieving a longer life of the heat-resistant member 2 .

The heat-resistant sheet 9 may be attached to the inner peripheral surface of the heat-resistant member 2 with an adhesive or the like. However, the configuration in which at least a part of the heat-resistant sheet 9 is embedded in the heat-resistant member 2 is more advantageous because separation from the heat-resistant member 2 can be suppressed. When the heat-resistant sheet 9 separates from the heat-resistant member 2, it becomes impossible to prevent the occurrence and growth of cracks. In some cases, the heat-resistant member 2 needs to be replaced.

When the heat-resistant sheet 9 is attached to the heat-resistant member 2 , the entire heat-resistant sheet 9 is exposed from the heat-resistant member 2 .

The heat-resistant sheet 9 may be arranged such that the entire heat-resistant sheet 9 is buried in the heat-resistant member 2 . The heat-resistant sheet 9 can suppress the growth of cracks inside the heat-resistant member 2 . Even if the heat-resistant sheet 9 is not exposed from the heat-resistant member 2 at all, the occurrence of cracks on the surface is suppressed if the heat-resistant sheet 9 is arranged at a position close to the inner peripheral surface of the heat-resistant member 2. It is desirable because it can be done.

The heat-resistant sheet 9 may be arranged along the entire circumference of the inner peripheral surface of the heat-resistant member 2 . The heat-resistant sheet 9 is arranged not only near the lower end of the inner peripheral surface of the heat-resistant member 2 but also over the entire circumference from the side to near the upper end. The heat-resistant sheet 9 is arranged around the entire circumference of the passage 5 .

When the heat-resistant member 2 is manufactured, after the heat-resistant sheet 9 is arranged on the heat-resistant member 2 in the manufacturing process, the heat-resistant paint is applied in the coating process to form the coating film portion 7 .

Even when a part of the thread 9a of the heat-resistant sheet 9 is exposed on the inner peripheral surface of the heat-resistant member 2 as illustrated in FIG. 9, the coating film portion 7 is formed on the surface of the thread 9a. Therefore, it is possible to avoid the problem that the oxide scale adheres to the thread 9a and is difficult to remove.

1 induction heating furnace 1a first unit 1b second unit 1c third unit 2 heat-resistant member 2a (cylindrical) heat-resistant member 2b (having inclined portion) heat-resistant member 3 heating coil 4 billet 5 passage 6 skid rail 7 coating film 8 Oxide scale 9 Heat-resistant sheet 9a Yarn x Extension direction y Width direction z Vertical direction O Center P1 Bottom end d Mesh size

Claims (8)

A heat-resistant member composed of a cylindrical member extending in a horizontal direction and formed so that a billet, which is an object to be heated, can pass through the inner peripheral surface side, and a heater arranged on the outer peripheral surface side of the heat-resistant member. In an induction heating furnace comprising a coil,
1. An induction heating furnace, wherein said heat-resistant member is made of concrete or ceramics, and has a coating film formed of heat-resistant paint on at least a part of an inner peripheral surface thereof. 2. The induction heating furnace according to claim 1, wherein said coating film portion is made of a heat-resistant paint containing zirconium dioxide as a main component. 3. The induction heating furnace according to claim 1, wherein the coating film portion is arranged in the vicinity of the lower end of the inner peripheral surface of the heat resistant member. 3. The induction heating furnace according to claim 1, wherein the coating film portion is arranged on the entire inner peripheral surface of the heat-resistant member. In a method for manufacturing a heat-resistant member which is composed of a cylindrical member extending in a horizontal direction and configured so that a billet, which is an object to be heated, can pass through the inner peripheral surface side,
a manufacturing step of molding and hardening the heat-resistant member from concrete or ceramics;
A method for manufacturing a heat-resistant member, further comprising: thereafter, applying a heat-resistant paint to at least a part of the inner peripheral surface of the heat-resistant member to form a coating film portion. 6. The method of manufacturing a heat-resistant member according to claim 5, wherein the coating film portion is made of a heat-resistant paint containing zirconium dioxide as a main component. After the coating step,
7. The method for manufacturing a heat-resistant member according to claim 5, further comprising a baking step of baking the coating film portion. The method for manufacturing a heat-resistant member according to any one of claims 5 to 7, wherein in the coating step, a heat-resistant paint is applied to the entire inner peripheral surface of the heat-resistant member to form the coating film portion.

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