JPH10272534A - Induction heating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently heat a billet by reducing radiation loss at the time of induction-heating the billet. SOLUTION: An inner tube body 11a and an outer tube body 11b constituted with a refractoriness ceramic tube to both, are arranged in concentric-state with a fixed interval to constitute a furnace center tube 11. The outer tube 11b is covered with a heat insulating material 12 and a coil conduit tube 13 is wound on the heat insulating material 12. In the inner tube body 11a of the furnace center tube 11, the billet 20 as a material to be heated, is carried and heated with electromagnetic induction by energizing to the coil conduit tube 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing various parts such as automobiles, construction machines, electric products, and agricultural machines by, for example, forging (plasticity) processing. The present invention relates to an induction heating furnace used for heating.

[0002]

2. Description of the Related Art When manufacturing various machine parts by hot forging, a billet material to be heated is preliminarily prepared.
After being heated by the heating furnace, forging is performed. As such a forging heating furnace, an induction heating furnace is widely used instead of a combustion heating furnace. The induction heating furnace is configured by winding a coil around a furnace tube through which the billet material is conveyed. When the coil is energized, the billet material conveyed in the furnace tube is electromagnetically heated.

[0003] In an induction heating furnace, a furnace tube for transferring a billet material is made of a refractory ceramic as disclosed in, for example, Japanese Utility Model Publication No. 2-4120 and Japanese Utility Model Publication No. 62-13722. It is common to use a single tube. The furnace tube constituted by one ceramic tube is excellent in fire resistance and wear resistance in a heated atmosphere, and moreover,
Since it has high thermal conductivity and emissivity, it is suitable as a furnace tube of an induction heating furnace for forging.

[0004]

However, since the core tube constituted by a single ceramic tube is usually formed to have a constant thickness over the entire length, the heating efficiency at the time of induction heating of the billet material is increased. Is not always enough. For example, when a billet material conveyed in a furnace tube is heated to a high temperature of 1200 ° C. or higher, the temperature in the furnace tube is low at the beginning of heating, and a large temperature difference occurs between the material and the billet material. As a result, heat radiation loss from the billet material is large, and the heating efficiency of the billet material is deteriorated. The temperature in the core tube subsequently rises due to heat radiation from the billet material, and the radiation loss of heat from the billet material decreases as the temperature of the core tube rises. The loss level and the core tube temperature level are balanced and stabilized. As described above, in order to heat the billet material at a predetermined stable high temperature, if the heat capacity of the furnace tube is large, it takes a relatively long time, and at the beginning of heating, heating due to insufficient heating of the billet material It is necessary to eliminate defective billet materials and to control the amount of current supplied to the coil for a long time.

[0005] Also, when the billet material is conveyed in the furnace tube in a discontinuous state with reduced processing, the radiation loss ratio of heat increases and the heating efficiency decreases.

The present invention has been made to solve such a problem, and an object of the present invention is to suppress the radiation loss of heat and, therefore, to provide an induction heating method which is excellent in heating efficiency of a material to be heated such as a billet material. To provide a furnace.

[0007]

The induction heating furnace of the present invention comprises:
A plurality of tubes constituted by a refractory ceramic tube have a core tube arranged and arranged concentrically at an appropriate interval.

[0008] A heating element may be provided between the tubes, and an inner peripheral surface of the tube disposed outside may be coated with a refractory having a large heat reflectance. .

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an example of an embodiment of an induction heating furnace according to the present invention. For example, this induction heating furnace is configured to heat by electromagnetic induction in order to forge a billet material 20 which is a bar having a circular cross section as a material to be heated, and a plurality of heating blocks 10 are horizontally arranged. It is arranged and configured. Each heating block 10
The heating core 10 has a furnace tube 11 laid horizontally with respect to the outer shell 14, and the heating blocks 10 are arranged so that the furnace tubes 11 of the heating blocks 10 are concentric. And the heating block 10 arranged at one end
The billet material 20 as a material to be heated is sequentially pushed into the core tube 11 by a pusher, a pinch roller, or the like, and the inside of the core tube 11 of each heating block 10 is
Each billet material 20 is sequentially passed. Billet material 20
Is transported in a double-pipe structure by a pair of pipes each made of refractory ceramic.

FIG. 2 is a cross-sectional view of the furnace tube 11. The core tube 11 has an inner tube 11a through which the billet material 20 passes, and an outer tube 11b fitted concentrically to the inner tube 11a at a constant interval.
And Inner tube 11a and outer tube 11b
Are each formed in a tubular shape by the same silicon carbide refractory ceramic. Inner tube 11a and outer tube 11b made of refractory ceramic
Each have extremely high thermal conductivity and high strength, are excellent in abrasion resistance to alkali, aluminum, carbon dioxide, oxidizing atmosphere and the like, and have high emissivity.

As shown in FIG. 1, the inner pipe 11a has a flange 1 at the end on the entrance side where the billet material 20 is carried in.
1c is provided, and a portion other than the portion provided with the flange portion 11c has a constant thickness having a constant inner diameter and an outer diameter. It is not always necessary to provide such a flange portion 11c in the inner pipe 11a. As shown in FIGS. 1 and 2, the outer tube 11b has a constant thickness having a constant inner diameter and an outer diameter throughout, and a constant gap with the outer peripheral surface of the inner tube 11a. Are formed. The outer peripheral surface of the outer tube 11b is entirely covered with a heat insulating material 12.

Between the inner tube 11a and the outer tube 11b, three spacers 11d extending along the entire length of the inner tube 11a in the axial direction are provided so as to keep the two tubes concentric.
They are provided at equal intervals in the circumferential direction. Each spacer 11d is made of a heat insulating material such as alumina cement having excellent heat resistance, and is formed in a strip shape having a constant thickness over the entire length.

The inner diameter of the inner tube 11a is, for example, about 8 mm larger than the outer diameter of the billet material 20 having a circular cross section.
In the case of mm, it is 73 mm. Inner tube 11
a has a thickness of 4 mm, so that the inner tube 11
The outer diameter of a is 81 mm. Also, the inner tube 1
The gap between the outer tube 1a and the outer tube 11b is 4 mm,
b has a thickness of 6 mm, so that the outer tube 11
b has an inner diameter of 89 mm and an outer diameter of 101 mm.

As shown in FIG. 1, the outer tube 11b has
A coil coil 13 made of copper is wound. The coil conduit 13 is in the shape of a hollow pipe having a rectangular cross section, and an insulating material is wound on the outer peripheral surface thereof. Coil conduit 1
Cooling water is allowed to flow through the inside of the nozzle 3.

The furnace tube 11, in which the ceramic inner tube 11a and the outer tube 11b are concentric, is installed horizontally in the center of an outer shell 14 made of a heat-resistant material such as non-asbestos. Each end is fixed to the outer shell 14 by alumina cement 15.

Each heating block 10 in which the furnace tube 11 is erected in the center of the outer shell 14 in a horizontal state, has a predetermined number and a predetermined length so that the billet material 20 is heated to a predetermined temperature. For example, six pieces are continuously arranged in the horizontal direction so that the respective core tubes 10 are concentric.

In the induction heating furnace having such a configuration, the billet material 20 is sequentially fed into the furnace tube 11 of the heating block 10 located on the inlet side by a pusher or the like, and the coil conduit 13 is energized. The billet material 20 is heated by electromagnetic induction. Then, the billet material 20 is sequentially heated by sequentially passing through the inside of the core tube 11 of each heating block 10, and is heated to a high temperature of 1200 ° C. inside the core tube 11 of the last heating block 10.

In this case, the core tube 1 of each heating block 10
1, the inner tube 11a and the outer tube 11b
Since each is made of a thin silicon carbide refractory ceramic, the billet material 20 to be heated is
Is efficiently heated. The thickness of each of the inner tube 11a and the outer tube 11b is about half of the thickness of a conventional core tube constituted by one ceramic tube,
Moreover, due to the double tube structure, the radiation loss of heat from the billet material 20 at the beginning of heating is reduced to about half as compared with the conventional core tube. Moreover, the inner tube 11a
Since the outer tube 11b and the outer tube 11b are arranged concentrically with a certain interval, the heat loss of the inner tube 11a is suppressed by the air layer formed therebetween, and the billet material 20 The heat transfer loss of the billet material 20 through the contacting inner tube 11a is suppressed. As a result, heat radiation loss and heat transfer loss in each furnace tube 11 are significantly reduced, and the heating efficiency of billet material 20 passing through furnace tube 10 is significantly improved. In addition, the temperature in the inner tube 11a having a small heat capacity rises in a short time even in comparison with the furnace tube constituted by one conventional ceramic tube. The billet material 20 is stabilized at the heating temperature in a short time. Therefore, at the beginning of heating, there is no possibility of the billet material being removed due to insufficient heating, and the yield is significantly improved. Further, the control of the amount of current flowing through the coil conduit 13 can be performed in a relatively short time, and the workability is significantly improved.

As described above, in the induction heating furnace of the present invention, the billet material 20 that passes through the furnace tube 11 of each heating block 10 is heated stably at a high temperature of 1200 ° C. or more by low electric power. become able to. Further, the induction heating furnace of the present invention has the same structure as the conventional induction heating furnace except that the furnace core tube 11 has a double tube structure formed by an inner tube 11a and an outer tube 11b formed of a refractory ceramic tube. Since the configuration is the same as that described above, the conventional induction heating furnace can be coped with only by changing only the core tube portion.

The outer tube 11 constituting the furnace tube 11
The inner peripheral surface of b may be coated with a refractory having a higher thermal reflectance than the outer tube 11b. When the inner peripheral surface of the outer tube 11b is coated with a refractory having a high thermal reflectance as described above, heat loss of the outer tube 11b can be reduced. The heating efficiency of 20 will be further improved.

FIG. 3 is a cross-sectional view showing another embodiment of the furnace tube 11 used in the induction heating furnace of the present invention. In the core tube 11, a pair of hollow pipe-shaped skid rails 11e are arranged along the axial direction at a lower portion inside the inner tube body 11a. Each skid rail 11e is arranged at regular intervals in the width direction so that the billet material 20 as the material to be heated can be placed and slid, and cooling water is provided in each skid rail 11e. It is made to flow. Other configurations are shown in FIGS. 1 and 2.
Has the same configuration as the core tube 11 shown in FIG.

FIG. 4 is a cross sectional view showing still another example of the embodiment of the furnace tube 11 used in the induction heating furnace of the present invention. In the furnace tube 11, the inner tube 11a has a regular hexagonal cross section, and each corner on the outer peripheral surface of the inner tube 11a contacts the inner peripheral surface of the outer tube 11b along the axial direction. Each side surface of the inner tube 11a is spaced apart from the inner peripheral surface of the outer tube 11b by a predetermined distance without providing a spacer. An inner tube 11 is provided on the upper and lower portions of the outer tube 11b.
The opposing corners in a are arranged respectively, and the inner pipe 11a and the outer pipe 11b have substantially the same thickness. Other configurations are the same as the core tube 11 shown in FIGS. 1 and 2.

In the core tube 11 having such a configuration, the billet material 20 is conveyed in a state of being in contact with a pair of side surfaces located at a lower portion of the inner tube body 11a, and the relatively lightweight billet material 20 is efficiently heated. can do.

As shown in FIG. 5, a semi-cylindrical upper half may be used in place of the upper half of the inner tube 11a having a regular hexagonal cross section.

Further, as shown in FIG.
a, the upper end of the lower half having a semi-hexagonal cross section is inclined so that the upper half of the lower half contacts the inner peripheral surface of the outer tube 11b. The edges may be abutted. In this case, the upper half of the inner tube 11a having a semi-cylindrical cross section is the outer tube 1
The inner peripheral portion of the upper half of the outer tube 11b is cut off over a half circumference so that a constant interval is formed with the inner peripheral surface of the outer tube 1b. In the furnace tube 11 having such a configuration, even the relatively heavy billet material 20 can be efficiently heated.

As shown in FIG. 7, the inner pipe 11a
Has the same configuration as the lower half of the inner tube 11a shown in FIG. 6, and the upper half is obtained by bisecting a cylinder having a regular dodecagonal cross section along the axis. It may be configured as a half and abutted against the lower half. In this case, the outer tube 11b is formed to have a constant thickness over the entire circumference so that the relatively lightweight billet material 20 can be efficiently heated, and the upper half and the lower portion of the inner tube 11a are formed. The halves have the same thickness. In the core tube 11 having such a configuration, the coil wound around the outer peripheral surface of the outer tube 11b is reduced in diameter, and the electromagnetic coupling efficiency is improved.

Further, as shown in FIG.
a has the same cross-sectional shape as the inner tube 11a of the core tube 11 shown in FIG. 7, the thickness of the upper half is made smaller than the thickness of the lower half, and the vertical line symmetry of the upper half is obtained. A strip-shaped heating element 1 extending along the axial direction between each of the side surfaces arranged at two positions and the inner peripheral surface of the outer tube 11b.
1f, and a strip-shaped heat generation extending in the axial direction also between each side surface of the lower half, which is disposed at two vertically symmetrical positions, and the inner peripheral surface of the outer tube 11b. The body 11f may be arranged.

In the core body 11 having such a configuration, each heating element 11f is heated just before heating by energizing the coil wound on the outer peripheral surface of the outer tube 11b.
The inner tube 11a is preheated. Then, when an appropriate time has passed since the preheating of the inner tube 11a by each heating element 11f, the outer tube 1
1b is energized and the billet material 20
Is inserted and heated. Due to heat radiation from each of the heating elements 11f and the billet material 20, the inner tube body 11a is heated to a temperature equal to the surface layer temperature of the billet material 20 without limit. In this way, the preheating of the inner tube body 11a by each heating element 11f allows the billet material 20 to be heated.
Becomes a stable high temperature state from the beginning of heating, and radiation loss of heat from the surface of the billet material 20 is significantly reduced. Therefore, the heating efficiency of the billet material 20 by the coil is further improved.

[0030]

As described above, in the induction heating furnace of the present invention, a plurality of pipes made of refractory ceramic tubes are concentrically arranged at appropriate intervals to form a furnace tube. In addition, the radiation loss of heat from the material to be heated during induction heating by the coil is significantly reduced, and the heating efficiency of the material to be heated is significantly improved. In addition, by providing a heating element between the tubes, the tubes located inside can be preheated, so that the heating efficiency of the material to be heated is further improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of an embodiment of an induction heating furnace of the present invention.

FIG. 2 is a cross-sectional view of a furnace tube used in the induction heating furnace.

FIG. 3 is a cross-sectional view showing another example of the core tube.

FIG. 4 is a cross-sectional view showing still another example of the furnace tube.

FIG. 5 is a cross-sectional view showing still another example of the furnace tube.

FIG. 6 is a cross-sectional view showing still another example of the furnace tube.

FIG. 7 is a cross-sectional view showing still another example of the furnace tube.

FIG. 8 is a cross-sectional view showing still another example of the furnace tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Heating block 11 Furnace tube 11a Inner tube 11b Outer tube 11d Spacer 11e Skid rail 11f Heating element 12 Insulation material 13 Coil conduit 14 Outer shell 20 Billet material

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification code FI H05B 6/10 331 H05B 6/10 331

Claims (3)

[Claims] 1. An induction heating furnace characterized in that a plurality of tubes constituted by refractory ceramic tubes have a core tube arranged and arranged concentrically at appropriate intervals. 2. The induction heating furnace according to claim 1, wherein a heating element is provided between the tubes. 3. A refractory having a high thermal reflectance is coated on an inner peripheral surface of a tube disposed outside.
2. The induction heating furnace according to item 1.