JP7560866B2 - Induction heating method and induction heating device - Google Patents

Description

The present invention relates to an induction heating method and an induction heating device for induction heating a cylindrical workpiece.

An induction heating method for induction heating a cylindrical workpiece is known. In the induction heating method disclosed in Patent Document 1, a heating step is performed to induction heat the workpiece, and then a cooling step is performed to cool the workpiece.

In the heating process, an inert gas is passed along the outer and inner surfaces of the workpiece to render the inside and outside of the workpiece non-oxidizing, and then the workpiece is induction heated by an induction coil.

In addition, in the cooling process, the workpiece is cooled by spraying the cooling liquid supplied from the cooling jacket onto the outer peripheral surface of the workpiece.

JP 2010-24515 A

However, in the cooling process of the conventional induction heating method described above, the oxygen dissolved in the coolant causes oxide scale (oxide film) to form on the outer surface of the workpiece, resulting in a problem of reduced appearance quality of the workpiece.

The present invention aims to solve the above-mentioned problems, and its purpose is to provide an induction heating method and an induction heating device that can suppress the formation of oxide scale on the outer peripheral surface of a cylindrical workpiece during induction heating and cooling of the workpiece.

The induction heating method according to one aspect of the present invention is an induction heating method for induction heating a cylindrical workpiece, and includes the steps of: (a) arranging an induction coil to surround the outer circumferential surface of the workpiece and arranging a partition tube between the outer circumferential surface of the workpiece and the induction coil, and in a state where an inert gas is supplied between the outer circumferential surface of the workpiece and the inner circumferential surface of the partition tube and to the inside of the workpiece ... (b) after (a), cooling the workpiece by supplying a coolant to the inside of the workpiece while supplying an inert gas between the outer circumferential surface of the workpiece and the inner circumferential surface of the partition tube, with the partition tube being arranged between the outer circumferential surface of the workpiece and the induction coil.

According to this aspect, when the workpiece is induction heated, an inert gas is supplied between the outer peripheral surface of the workpiece and the inner peripheral surface of the partition tube, and to the inside of the workpiece. This allows the workpiece to be induction heated in a state where air (oxygen) is blocked between the outer peripheral surface of the workpiece and the inner peripheral surface of the partition tube, and inside the workpiece. As a result, the formation of oxide scale on the outer peripheral surface and inner peripheral surface of the workpiece during induction heating of the workpiece can be suppressed. In addition, when the workpiece is cooled, a coolant is supplied to the inside of the workpiece while supplying an inert gas between the outer peripheral surface of the workpiece and the inner peripheral surface of the partition tube. This allows the workpiece to be cooled in a state where air (oxygen) is blocked between the outer peripheral surface of the workpiece and the inner peripheral surface of the partition tube. As a result, the formation of oxide scale on the outer peripheral surface of the workpiece during cooling of the workpiece can be suppressed. Therefore, the appearance quality of the outer peripheral surface of the workpiece can be improved.

For example, in (b), the workpiece may be cooled by inserting an injection nozzle for injecting the cooling liquid into the inside of the workpiece and injecting the cooling liquid from the injection nozzle toward the inside of the workpiece.

According to this aspect, the workpiece can be cooled efficiently by inserting an injection nozzle for injecting the cooling liquid into the inside of the workpiece.

For example, in (b), the workpiece may be cooled by radially spraying cooling liquid from the outer circumferential surface of the spray nozzle toward the inner circumferential surface of the workpiece.

According to this aspect, the cooling liquid is sprayed radially from the outer circumferential surface of the spray nozzle toward the inner circumferential surface of the workpiece, thereby allowing the workpiece to be cooled more efficiently.

For example, in (a), with the workpiece standing vertically, an inert gas is caused to flow from bottom to top between the outer circumferential surface of the workpiece and the inner circumferential surface of the partition pipe, and inside the workpiece, while in (b), with the workpiece standing vertically, an inert gas is caused to flow from bottom to top between the outer circumferential surface of the workpiece and the inner circumferential surface of the partition pipe.

According to this embodiment, the heat of the workpiece, which is induction-heated by the induction coil, can be used to facilitate the flow of the inert gas from below to above.

For example, the partition tube may be configured as a quartz tube or a ceramic tube.

According to this aspect, the partition tube can be made of a non-magnetic and heat-resistant material.

The induction heating device according to one aspect of the present invention is an induction heating device for induction heating a cylindrical workpiece, and includes an induction coil that is arranged to surround the outer circumferential surface of the workpiece and induction heats the workpiece, a partition pipe arranged between the outer circumferential surface of the workpiece and the induction coil, an inert gas supply unit that supplies an inert gas, and a cooling liquid supply unit that supplies a cooling liquid. When the workpiece is induction heated by the induction coil, the inert gas supply unit supplies inert gas between the outer circumferential surface of the workpiece and the inner circumferential surface of the partition pipe and to the inside of the workpiece, and when the workpiece is cooled, the inert gas supply unit supplies inert gas between the outer circumferential surface of the workpiece and the inner circumferential surface of the partition pipe, and the cooling liquid supply unit supplies cooling liquid to the inside of the workpiece.

According to this embodiment, as described above, it is possible to suppress the formation of oxide scale on the outer peripheral surface of the workpiece during induction heating and cooling of the workpiece, thereby improving the appearance quality of the outer peripheral surface of the workpiece.

According to an embodiment of the induction heating method of the present invention, the formation of oxide scale on the outer peripheral surface of a cylindrical workpiece during induction heating and cooling can be suppressed, thereby improving the appearance quality of the outer peripheral surface of the workpiece.

1 is a perspective view showing an induction heating device according to an embodiment; 2 is a schematic cross-sectional view of a main part of the induction heating device according to the embodiment taken along line II-II in FIG. 1. 3 is a schematic cross-sectional view of a main part of the induction heating device according to the embodiment taken along line III-III in FIG. 1. 4 is a flowchart showing a flow of operations of the induction heating device according to the embodiment. 4 is a schematic cross-sectional view of a main part of an induction heating device according to an embodiment in a heating step. FIG. 4 is a schematic cross-sectional view of a main part of an induction heating device according to an embodiment in a heating step. FIG. 4 is a schematic cross-sectional view of a main part of an induction heating device according to an embodiment in a cooling process. FIG. 4 is a schematic cross-sectional view of a main part of an induction heating device according to an embodiment in a cooling process. FIG. 6 is a photograph showing the appearance of a workpiece induction-heated by each induction heating device according to a comparative example, examples 1 and 2.

The following describes the embodiment in detail with reference to the drawings.

The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection forms, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the scope of the claims. Furthermore, among the components in the following embodiments, components that are not described in an independent claim that represents a top-level concept are described as optional components.

The figures are not necessarily strict illustrations. In each figure, the same reference numerals are used for substantially the same configurations, and duplicate explanations are omitted or simplified.

(Embodiment)
[1. Configuration of induction heating device]
First, the configuration of an induction heating device 2 according to an embodiment will be described with reference to Fig. 1 to Fig. 3. Fig. 1 is a perspective view showing an induction heating device 2 according to an embodiment. Fig. 2 is a schematic cross-sectional view of a main part of the induction heating device 2 according to an embodiment taken along line II-II in Fig. 1. Fig. 3 is a schematic cross-sectional view of a main part of the induction heating device 2 according to an embodiment taken along line III-III in Fig. 1.

In addition, in Figures 1 to 3, the left-right direction of the induction heating device 2 is the X-axis direction, the front-rear direction of the induction heating device 2 is the Y-axis direction, and the up-down direction of the induction heating device 2 is the Z-axis direction. Also, in Figures 1 to 3, the positive side of the Z-axis is the "upward" direction, and the negative side of the Z-axis is the "downward" direction.

The induction heating device 2 is a device for induction heating (so-called high-frequency hardening) the workpiece 4 with high frequencies. High-frequency hardening is a heat treatment that heats and hardens the surface of the workpiece 4 by generating electromagnetic induction at high frequencies, for example, several kHz to several tens of kHz.

The workpiece 4 is a thin-walled, cylindrical, long metal part made of steel or the like, such as the steel shaft of a golf club. The thickness of the workpiece 4 is, for example, 0.2 to 0.5 mm, and the length of the workpiece 4 is, for example, approximately 1000 mm.

As shown in Figures 1 to 3, the induction heating device 2 includes a base section 6, a support unit 8, an air supply section 10, a cooling liquid receiving tank 12, inert gas supply sections 14a and 14b, an exhaust section 16, a receiving jig 18, a cooling liquid supply section 20, an injection nozzle 22, a partition pipe 24, and an induction coil 26.

As shown in FIG. 1, the base 6 is a member that serves as the foundation for the entire induction heating device 2. The base 6 is placed, for example, on the floor surface of a room.

The support unit 8 is a member for supporting the partition pipe 24. As shown in FIG. 1, the support unit 8 has a lower support plate 28, a number of support columns 30, and an upper support plate 32.

The lower support plate 28 is a member for supporting the lower end of the partition pipe 24. As shown in FIG. 1, the lower support plate 28 is a substantially rectangular flat plate, and is disposed at the upper end of the base portion 6. As shown in FIG. 2, a circular opening 34 is formed in the center of the lower support plate 28. Also, as shown in FIGS. 1 and 2, piping plugs 36a, 36b are disposed on the lower support plate 28. The piping plugs 36a, 36b are disposed at positions substantially symmetrical to the opening 34 in the XY plane view, and are disposed so as to penetrate the lower support plate 28.

The multiple support columns 30 are members for supporting the upper support plate 32. The multiple support columns 30 are formed in a long cylindrical shape and stand upright from the upper surface of the lower support plate 28.

The upper support plate 32 is a member for supporting the upper end of the partition pipe 24. As shown in FIG. 1, the upper support plate 32 is a flat plate having a substantially rectangular shape, and is supported by the upper ends of the multiple support columns 30. In other words, the upper support plate 32 is disposed above and facing the lower support plate 28. As shown in FIG. 3, a circular opening 38 is formed in the center of the upper support plate 32.

As shown in FIG. 2, the air supply section 10 is attached to the underside of the lower support plate 28. The air supply section 10 is formed with an air supply/drainage flow path 40 and an air supply flow path 42 that communicate with the opening 34 of the lower support plate 28. The upper end of the air supply/drainage flow path 40 opens on the upper surface of the lower support plate 28, and the lower end of the air supply/drainage flow path 40 opens on the lower surface of the lower support plate 28. Similarly, the upper end of the air supply flow path 42 opens on the upper surface of the lower support plate 28, and the lower end of the air supply flow path 42 opens on the lower surface of the lower support plate 28.

A piping plug 44 that communicates with the air supply passage 42 is attached to the lower end of the air supply section 10. The piping plug 44 is connected to the above-mentioned piping plug 36a via a tube 46.

The cooling liquid receiving tank 12 is a water tank for receiving the cooling liquid (described later) that flows down through the inside of the workpiece 4. As shown in Figs. 1 and 2, the cooling liquid receiving tank 12 is attached to the lower surface of the lower support plate 28, and is positioned so as to cover the air supply section 10 from below. As shown in Fig. 1, a drain pipe 48 is disposed at the lower end of the cooling liquid receiving tank 12 for discharging the cooling liquid that has accumulated in the cooling liquid receiving tank 12 to the outside.

As shown in FIG. 2, the inert gas supply units 14a and 14b are sources that supply inert gas such as nitrogen or argon. The inert gas supply units 14a and 14b are connected to piping plugs 36a and 36b, respectively, via tubes (not shown).

As shown in FIG. 3, the exhaust section 16 is attached to the upper surface of the upper support plate 32. The exhaust section 16 is formed with a first exhaust passage 50, a second exhaust passage 52, and a third exhaust passage 54 that communicate with the opening 38 of the upper support plate 32.

The first exhaust flow path 50 extends from the upper surface to the lower surface of the exhaust section 16. That is, the upper end of the first exhaust flow path 50 opens to the upper surface of the exhaust section 16, and the lower end of the first exhaust flow path 50 opens to the lower surface of the exhaust section 16. In addition, a piping plug 56 is attached to the upper end of the first exhaust flow path 50.

The second exhaust flow path 52 extends from the underside to the side of the exhaust section 16. That is, one end of the second exhaust flow path 52 opens to the underside of the exhaust section 16, and the other end of the second exhaust flow path 52 opens to the side of the exhaust section 16. A check valve may be disposed at the other end of the second exhaust flow path 52.

The third exhaust flow path 54 branches off from the first exhaust flow path 50 and extends laterally. That is, one end of the third exhaust flow path 54 opens to the side of the first exhaust flow path 50, and the other end of the third exhaust flow path 54 opens to the side of the exhaust section 16. A check valve may be disposed at the other end of the third exhaust flow path 54.

The receiving jig 18 is a jig for holding the workpiece 4 in an upright position. As shown in Figures 2 and 3, the receiving jig 18 has a lower receiving jig 58, a lower contact jig 60, an upper receiving jig 62, and an upper contact jig 64.

As shown in FIG. 2, the lower support jig 58 is formed in a cylindrical shape and is made of, for example, resin. The lower support jig 58 stands upright from the upper surface of the air supply section 10 through the opening 34 of the lower support plate 28. The inside of the lower support jig 58 communicates with the air supply/drainage flow path 40 of the air supply section 10 and also communicates with the inside of the workpiece 4. The lower contact jig 60 is formed in a ring shape and is made of, for example, ceramic. The lower contact jig 60 is disposed at the upper end of the lower support jig 58 and detachably supports the lower end of the workpiece 4 standing upright in the vertical direction.

As shown in FIG. 3, the upper support jig 62 is formed in a cylindrical shape and is made of, for example, resin. The upper support jig 62 extends downward from the lower surface of the exhaust section 16 through the opening 38 of the upper support plate 32. The inside of the upper support jig 62 communicates with the first exhaust flow path 50 of the exhaust section 16 and also communicates with the inside of the workpiece 4. The upper contact jig 64 is formed in a ring shape and is made of, for example, ceramic. The upper contact jig 64 is disposed at the lower end of the upper support jig 62 and detachably supports the upper end of the workpiece 4 standing upright in the vertical direction.

As shown in FIG. 3, the coolant supply unit 20 is a supply source that supplies a coolant (quenching liquid) for cooling the induction-heated workpiece 4. The coolant is, for example, an aqueous solution containing a polymer such as PAG (polyalkylene glycol). The coolant supply unit 20 is connected to a piping plug 56 via a tube (not shown).

3, the injection nozzle 22 is a long nozzle for injecting the cooling liquid. The upper end of the injection nozzle 22 is attached to the inner peripheral surface of the piping plug 56 via a packing 66. This allows the injection nozzle 22 to communicate with the piping plug 56. The injection nozzle 22 extends downward from the piping plug 56, and a part of it is inserted into each of the upper receiving jig 62 and the upper contact jig 64, and into the workpiece 4 held upright by the receiving jig 18. As shown in FIG. 2, the lower end of the injection nozzle 22 is located slightly above the lower end of the workpiece 4. In the area of the outer peripheral surface of the injection nozzle 22 that is inserted into the workpiece 4, a plurality of nozzle holes (not shown) for radially injecting the cooling liquid toward the inner peripheral surface of the workpiece 4 are formed.

The partition tube 24 is a member for separating the outer peripheral surface of the workpiece 4 held in an upright position by the receiving jig 18 from the induction coil 26, and is formed in a thin-walled cylindrical and long shape. The partition tube 24 is made of a non-magnetic and heat-resistant material, such as a quartz tube or a ceramic tube. As shown in FIG. 2, the lower end of the partition tube 24 is attached to the inner peripheral surface of the opening 34 of the lower support plate 28. Also, as shown in FIG. 3, the upper end of the partition tube 24 is attached to the inner peripheral surface of the opening 38 of the upper support plate 32. As a result, the partition tube 24 is arranged to surround the receiving jig 18 and the outer peripheral surface of the workpiece 4 held in an upright position by the receiving jig 18.

The induction coil 26 is for induction heating the workpiece 4 and is electrically connected to a power circuit (not shown). As shown in FIG. 1, the induction coil 26 is a so-called multi-turn coil formed, for example, by winding a copper pipe in a spiral shape. The induction coil 26 is supported by coil supports 68 attached to a plurality of support columns 30 and is arranged to surround the outer circumferential surface of the partition tube 24. That is, as shown in FIG. 2 and FIG. 3, the induction coil 26 is arranged to surround the outer circumferential surface of the workpiece 4 over the entire length of the workpiece 4, and the partition tube 24 is arranged between the outer circumferential surface of the workpiece 4 and the induction coil 26.

2. Operation of induction heating device
Next, the operation of the induction heating device 2 according to the embodiment will be described with reference to Fig. 4 to Fig. 8. Fig. 4 is a flowchart showing the flow of the operation of the induction heating device 2 according to the embodiment. Figs. 5 and 6 are schematic cross-sectional views of the main parts of the induction heating device 2 according to the embodiment in the heating process. Figs. 7 and 8 are schematic cross-sectional views of the main parts of the induction heating device 2 according to the embodiment in the cooling process.

[2-1. Heating process]
As shown in FIG. 4, first, a heating step is performed in which the workpiece 4 is induction-heated by the induction coil 26 (S1).

In the heating process, the raw material of the workpiece 4 to be induction heated is held upright in the vertical direction by the receiving jig 18. As a result, the induction coil 26 is positioned to surround the outer periphery of the workpiece 4, and the partition tube 24 is positioned between the outer periphery of the workpiece 4 and the induction coil 26. In this state, as shown in FIG. 5, both inert gas supply units 14a and 14b are turned on, and as shown in FIG. 6, the cooling liquid supply unit 20 is turned off.

As shown by the arrows in FIG. 5, the inert gas from the inert gas supply unit 14a is supplied between the outer circumferential surface of the workpiece 4 and the inner circumferential surface of the partition tube 24 through (a1) the piping plug 36a, (a2) the tube 46, (a3) the piping plug 44, (a4) the air supply passage 42 of the air supply unit 10, (a5) the opening 34 of the lower support plate 28, and (a6) the gap between the outer circumferential surface of the lower support jig 58 and the inner circumferential surface of the partition tube 24.

Then, as shown by the arrows in Figure 6, the inert gas flows from bottom to top between the outer circumferential surface of the workpiece 4 and the inner circumferential surface of the partition tube 24, and is exhausted to the outside through (a7) the opening 38 of the upper support plate 32 and (a8) the second exhaust flow path 52 of the exhaust section 16.

As shown by the arrows in Figure 5, the inert gas from the inert gas supply unit 14b is supplied to the inside of the workpiece 4 through (b1) the piping plug 36b, (b2) the coolant receiving tank 12, (b3) the air supply/drainage flow path 40 of the air supply unit 10, (b4) the opening 34 of the lower support plate 28, and (b5) the inside of the lower receiving jig 58.

Then, as shown by the arrows in FIG. 6, the inert gas flows from bottom to top inside the workpiece 4 and is exhausted to the outside through (b6) the opening 38 in the upper support plate 32, (b7) the first exhaust passage 50 in the exhaust section 16, and (b8) the third exhaust passage 54 in the exhaust section 16.

In this manner, inert gas is supplied between the outer circumferential surface of the workpiece 4 and the inner circumferential surface of the partition tube 24, and to the inside of the workpiece 4. As a result, the inert gas blocks air (oxygen) between the outer circumferential surface of the workpiece 4 and the inner circumferential surface of the partition tube 24, and inside the workpiece 4.

In this state, a high-frequency current generated by the power supply circuit is supplied to the induction coil 26 for a predetermined time, and the workpiece 4 is inductively heated by the induction coil 26 over the entire length of the workpiece 4. At this time, as described above, air (oxygen) is blocked between the outer peripheral surface of the workpiece 4 and the inner peripheral surface of the partition tube 24, and inside the workpiece 4, so the workpiece 4 can be inductively heated in a so-called non-oxidizing state.

At this time, the inert gas flowing between the outer peripheral surface of the workpiece 4 and the inner peripheral surface of the partition pipe 24, and inside the workpiece 4, can rise smoothly due to the heat of the induction-heated workpiece 4. In addition, by induction-heating the workpiece 4, the oil vapor generated from the outer peripheral surface and inner peripheral surface of the workpiece 4 is discharged to the outside through the second exhaust passage 52 and the third exhaust passage 54 of the exhaust section 16, just like the inert gas.

After the above-mentioned predetermined time has elapsed, the supply of high-frequency current to the induction coil 26 is stopped, and the induction heating of the workpiece 4 by the induction coil 26 is stopped.

[2-2. Cooling process]
As shown in FIG. 4, after the heating step (S1) is performed, a cooling step is performed (S2) to cool the induction-heated workpiece 4.

In the cooling process, continuing from the heating process, the induction-heated workpiece 4 is held upright in the vertical direction by the receiving jig 18. In this state, as shown in FIG. 7, the inert gas supply unit 14a is turned on, the inert gas supply unit 14b is turned off, and as shown in FIG. 8, the cooling liquid supply unit 20 is turned on.

As shown by the arrows in FIG. 7, the inert gas from the inert gas supply unit 14a is supplied between the outer circumferential surface of the workpiece 4 and the inner circumferential surface of the partition tube 24 through (c1) the piping plug 36a, (c2) the tube 46, (c3) the piping plug 44, (c4) the air supply passage 42 of the air supply unit 10, (c5) the opening 34 of the lower support plate 28, and (c6) the gap between the outer circumferential surface of the lower support jig 58 and the inner circumferential surface of the partition tube 24.

Then, as shown by the arrows in Figure 8, the inert gas flows from bottom to top between the outer circumferential surface of the workpiece 4 and the inner circumferential surface of the partition tube 24, and is exhausted to the outside through (c7) the opening 38 of the upper support plate 32 and (c8) the second exhaust passage 52 of the exhaust section 16.

Note that the inert gas supply unit 14b is turned off, so no inert gas is supplied to the inside of the workpiece 4.

As shown by the arrows in FIG. 8, the cooling liquid from the cooling liquid supply unit 20 is supplied to the injection nozzle 22 through the piping plug 56. The cooling liquid supplied to the injection nozzle 22 is sprayed radially from the multiple nozzle holes toward the inner surface of the workpiece 4 while flowing down inside the injection nozzle 22. As a result, the workpiece 4 is cooled by the cooling liquid over its entire length. At this time, as described above, air (oxygen) is blocked between the outer surface of the workpiece 4 and the inner surface of the partition pipe 24, so the workpiece 4 can be cooled in a so-called non-oxidizing state.

The steam generated on the inner circumferential surface of the workpiece 4 during cooling of the workpiece 4 is discharged to the outside through the third exhaust passage 54. As a result, even if the supply of inert gas to the inside of the workpiece 4 is stopped, the high-temperature steam generated on the inner circumferential surface of the workpiece 4 is discharged to the outside, so that air (oxygen) is prevented from flowing back into the inside of the workpiece 4, and an oxidation-free state can be maintained.

As shown in FIG. 7, the cooling liquid that has cooled the workpiece 4 flows through the inside of the lower receiving jig 58 and the air supply/drainage flow path 40 of the air supply section 10, and is stored in the cooling liquid receiving tank 12. The cooling liquid that has accumulated in the cooling liquid receiving tank 12 is discharged to the outside through the drainage pipe 48 (see FIG. 1).

3. Effects
As described above, in the heating process, the workpiece 4 can be induction heated in a state in which air (oxygen) is blocked between the outer circumferential surface of the workpiece 4 and the inner circumferential surface of the partition pipe 24 and inside the workpiece 4. This makes it possible to suppress the formation of oxide scale on the outer circumferential surface and inner circumferential surface of the workpiece 4 in the heating process.

In addition, in the cooling process, the workpiece 4 can be cooled while air (oxygen) is blocked between the outer peripheral surface of the workpiece 4 and the inner peripheral surface of the partition tube 24. This makes it possible to suppress the formation of oxide scale on the outer peripheral surface of the workpiece 4 in the cooling process.

Therefore, the formation of oxide scale on the outer peripheral surface of the workpiece 4 during induction heating and cooling of the workpiece 4 can be suppressed, and the appearance quality of the outer peripheral surface of the workpiece 4 can be improved.

4. Examples and Comparative Examples
The following experiment was carried out to confirm the effect of this embodiment, that is, the effect of suppressing the formation of oxide scale on the outer peripheral surface of the workpiece 4 during induction heating and cooling of the workpiece 4. Fig. 9 is a photograph showing the appearance of the workpieces induction heated by the induction heating devices according to the comparative example, examples 1 and 2.

In a comparative example, the raw material of a cylindrical steel workpiece shown in FIG. 9(a) was induction heated in the atmosphere at a high frequency of 8 kHz, and then the workpiece was cooled in the atmosphere. As a result, as shown in FIG. 9(b), an oxide scale was formed on the outer peripheral surface of the workpiece, and the outer peripheral surface of the workpiece turned black.

In Example 1, the raw material of a cylindrical steel workpiece shown in FIG. 9(a) was induction heated in a nitrogen atmosphere at a high frequency of 42 kHz, and then the workpiece was cooled in the nitrogen atmosphere. As a result, as shown in FIG. 9(c), no oxide scale was formed on the outer peripheral surface of the workpiece, and the outer peripheral surface of the workpiece maintained the luster of the raw material.

In Example 2, the raw material of a cylindrical steel workpiece shown in FIG. 9(a) was induction heated in a nitrogen atmosphere at a high frequency of 8 kHz, and then the workpiece was cooled in the nitrogen atmosphere. As a result, as shown in FIG. 9(d), almost no oxide scale was formed on the outer peripheral surface of the workpiece, and the outer peripheral surface of the workpiece maintained a luster close to that of the raw material.

From the above, it has been confirmed that the induction heating device 2 according to the embodiment has the effect of suppressing the formation of oxide scale on the outer peripheral surface of the workpiece 4 during induction heating and cooling of the workpiece 4.

(Modifications, etc.)
Although the induction heating device according to one or more aspects of the present invention has been described based on the above-mentioned embodiment, the present invention is not limited to the above-mentioned embodiment. As long as it does not deviate from the spirit of the present invention, various modifications conceived by a person skilled in the art to this embodiment and forms constructed by combining components in different embodiments may also be included within the scope of one or more aspects of the present invention.

In the above embodiment, the induction coil 26 is a multi-turn coil, but this is not limited thereto, and it may be, for example, a so-called line coil formed by bending a copper pipe.

In addition, in the above embodiment, a portion of the injection nozzle 22 is inserted into the workpiece 4, but it does not necessarily have to be inserted into the workpiece 4. In this case, the lower end of the injection nozzle 22 is positioned above the upper end of the workpiece 4, and the cooling liquid injected downward from the lower end of the injection nozzle 22 is supplied to the inside of the workpiece 4 through an opening at the upper end of the workpiece 4.

The present invention can be applied to induction heating devices for high-frequency hardening of metal parts, for example.

Reference Signs List 2 Induction heating device 4 Work 6 Base 8 Support unit 10 Air supply section 12 Cooling liquid receiving tank 14a, 14b Inert gas supply section 16 Exhaust section 18 Receiving jig 20 Cooling liquid supply section 22 Spray nozzle 24 Partition pipe 26 Induction coil 28 Lower support plate 30 Support column 32 Upper support plate 34, 38 Openings 36a, 36b, 44, 56 Piping plug 40 Air supply/drain passage 42 Air supply passage 46 Tube 48 Drain pipe 50 First exhaust passage 52 Second exhaust passage 54 Third exhaust passage 58 Lower receiving jig 60 Lower contact jig 62 Upper receiving jig 64 Upper contact jig 66 Gasket 68 Coil support

Claims (5)

An induction heating method for induction heating a cylindrical workpiece, comprising:
(a) standing the workpiece vertically, arranging an induction coil to surround the outer circumferential surface of the workpiece, and arranging a partition pipe between the outer circumferential surface of the workpiece and the induction coil, and in a state where an inert gas is supplied between the outer circumferential surface of the workpiece and the inner circumferential surface of the partition pipe and into the inside of the workpiece so as to flow from below to above , the step of inductively heating the workpiece by the induction coil;
(b) after (a), standing the workpiece upright and disposing the partition pipe between the outer peripheral surface of the workpiece and the induction coil, supplying an inert gas between the outer peripheral surface of the workpiece and the inner peripheral surface of the partition pipe so as to flow from below to above , while supplying a cooling liquid into the inside of the workpiece to cool the workpiece. 2. The induction heating method according to claim 1, wherein in (b), the workpiece is cooled by injecting a cooling liquid from an injection nozzle toward the inside of the workpiece while the injection nozzle is inserted into the inside of the workpiece. The induction heating method according to claim 2 , wherein in (b), the workpiece is cooled by radially spraying the cooling liquid from an outer circumferential surface of the spray nozzle toward an inner circumferential surface of the workpiece. The induction heating method according to any one of claims 1 to 3 , wherein the partition tube is a quartz tube or a ceramic tube. An induction heating device for induction heating a cylindrical workpiece,
An induction coil arranged to surround an outer peripheral surface of the workpiece and inductively heats the workpiece;
A partition pipe disposed between an outer peripheral surface of the workpiece and the induction coil;
an inert gas supply unit for supplying an inert gas;
a coolant supply unit that supplies a coolant,
When the workpiece is induction-heated by the induction coil, the inert gas supply unit supplies inert gas to flow from the bottom to the top between the outer peripheral surface of the workpiece and the inner peripheral surface of the partition pipe, and into the inside of the workpiece, with the workpiece standing upright .
When cooling the workpiece, the workpiece is held upright, and the inert gas supply unit supplies inert gas between the outer peripheral surface of the workpiece and the inner peripheral surface of the partition pipe so that the inert gas flows from below to above , and the cooling liquid supply unit supplies cooling liquid to the inside of the workpiece.

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