JPS6343171B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a metal tube bending method and an apparatus therefor, and particularly to a cooling method and a method suitable for making the heating width uniform and narrowing the heating width. Regarding the device.

[Background of the invention]

In high frequency induction heating bending processing, the following method is used as a conventional general processing method.

Insert the pipe to be bent into the inside of the heating ring and cooling ring connected to a high frequency power source without touching the rings, fix the rear part of the pipe to be bent to a pushing device, and attach the front part to the arm that determines the bending radius. Clamp. When the high-frequency power is turned on, the portion of the pipe to be bent that is located inside the heating ring is heated by high-frequency induction heating by the heating ring to a temperature suitable for hot working. At the same time, a coolant is injected from the cooling ring to cool the arm side portion of the heating ring of the pipe to be bent, keeping the heating width constant and making it ready for cooling immediately after the bending process. In this state, when the pipe to be bent is slowly pushed straight forward from the rear by the pushing device, a bending moment is generated in the narrow part processed by the heating coil to the hot working area, causing plastic deformation and setting. It is deformed to the specified radius of curvature and immediately cooled in a cooling ring to form the bent part.
This process is repeated continuously to produce a bent pipe.

The heating coil and the cooling ring are set as shown in FIG. 6, and the coolant is uniformly injected from the cooling ring in the circumferential direction. When the coolant is water, the water injected from the nozzle of the cooling ring flows down the tube surface of the tube to be bent due to gravity to the bottom of the tube. The amount of cooling water flowing on the pipe surface is the smallest at the top of the pipe and increases as it goes downwards.The cooling rate, which is one of the factors that determines the material properties of the bent part after bending the pipe to be bent, is lower in the circumferential direction. changes with
This is also a cause of variations in the material properties of bent parts after processing.

In order to equalize the flow rate of cooling water on the pipe surface,
By changing the nozzle diameter and arrangement of the cooling ring circumferentially, increasing the amount of cooling water at the top of the pipe to be processed, and gradually decreasing the amount of cooling water injected from the nozzle, the amount of cooling water flowing on the wall of the pipe to be processed can be reduced. It is possible to try to make it uniform, but to make it completely uniform,
All of the cooling water must be injected at the top of the pipe to be processed, making it difficult to form a narrow heating section, which is the most important processing condition for high-frequency bending. If the pipe narrows at the top and widens downward, or if cooling water is injected from each nozzle, the heating width becomes narrow in the vicinity of the nozzles, resulting in a saw-shaped heating zone, which worsens the high-frequency bending conditions. The result is

When the coolant is in the form of air or mist, it does not flow down the surface of the pipe to be processed like water, and the air or mist that is injected in the axial direction of the pipe above the nozzle mouth of the cooling ring stagnates. It flows away in the axial direction without any movement. However, since compressed air is injected from the nozzle, it is a source of noise. Furthermore, in high-frequency bending, it is necessary to provide a narrow and uniform heating zone, but in the case of air cooling, the cooling capacity is lower than that of water cooling, so the heating zone becomes wider than that of water cooling. In particular, when the bending radius is made as small as that of an elbow joint, unless the heating zone is kept narrower than in the case of large radius bending, buckling will occur during processing, resulting in a bent pipe with wrinkles. Especially in the case of air cooling, it is necessary to consider the cooling capacity and devise a cooling method.

Currently, bending with a bending radius similar to that of an elbow is extremely difficult, and it is necessary to apply a large compressive force in the axial direction of the pipe to be processed in order to prevent significant thinning on the back side of the pipe to be processed. If this compressive force becomes excessive, buckling occurs in the heated portion, and the tube surface becomes uneven. In order to prevent this phenomenon, it is necessary to narrow the heating area as much as possible, and various efforts have been made to date. Below is an example of such an attempt.

JP-A No. 58-138522 discloses a method in which the cross-sectional shape of the heating coil is tapered in order to prevent irregular deformation such as buckling and wrinkles in the bent portion.
A coil shape has been devised in which cooling water is injected toward the tube material from both ends of the inner diameter surface to reduce the heating width (Fig. 10). This configuration is as follows. While heating the tubular material 52, which is the workpiece, with the annular heating coil 51A, a working force is applied to the end surface of the tubular material 52 via the rod 55a by driving the hydraulic cylinder 55, and the arm 58, one end of which is fixed, is moved around the pivot 59. Rotate the guide roller 56
Thereafter, a bending moment is generated to bend the tube material 52. The annular heating coil 51A has a tapered cross-sectional shape that narrows from the outer diameter surface 51a toward the inner diameter surface 51b, and injects cold water 54 onto the pipe material 52 from injection holes 51c provided at both ends of the inner diameter surface 51b to generate high-frequency waves. High frequency power is supplied from the oscillator 57 to heat the tube material 52 in a narrow heating width 61A.

However, depending on the amount of cooling water flowing through the heating coil, most of the internal heat generated in the heating section of the pipe to be processed may be removed by the cooling water, and the hot processing area may not be heated. On the other hand, in order to heat up to the hot working region, it is sufficient to reduce the amount of cooling water flowing through the heating coil, but the heating coil itself may be damaged due to heat generation. In order to heat the heating area to the hot working area and cool it appropriately so that the heating width is as narrow as possible while preventing damage to the heating coil, the diameter and number of holes provided in the heating coil, and the injection angle must be adjusted. The flow rate balance before and after the heating coil is delicately related to each other, making it extremely difficult to manufacture a complete heating coil. Furthermore, if the angle of the cooling nozzle is set deep relative to the surface of the pipe to be processed, the cooling water will be drawn under the coil, making the heating area non-uniform.

Another example of an invention devised as a method for reducing the heating width is JP-A-58-176025. In this example, a water-cooling ring is provided on both sides of the heating coil with injection holes formed on its inner diameter surface for injecting coolant toward the pipe material. Inventing the shape. The hot tube bending machine has an annular heating coil 51 on the outer periphery of the bending portion of the tube material 52, and supplies high frequency power from a high frequency oscillator 57 to this to heat the bending portion while heating the arm 58. Rotate to bend the tube. A water cooling ring 62 is provided on both sides of the heating coil 51, and the water cooling ring 62 has injection holes 62c formed on the inner diameter surface 62b for injecting cooling water toward the tube material 52. Cooling water is injected toward the tube material 52 from the injection hole 62c to cool the tube material 52, narrowing the heating width and preventing irregular deformation such as buckling and wrinkles.

However, if the angle of the cooling nozzle is made deep with respect to the surface of the pipe to be processed, the cooling water will flow toward the heating coil, resulting in an uneven heating area. In addition, similar to the conventional high-frequency bending method, in this example as well, the amount of cooling water flowing on the outer surface of the pipe to be processed increases from the top to the bottom of the pipe to be processed. This causes variations in the cooling rate.

[Purpose of the invention]

An object of the present invention is to provide a bending method and apparatus using a heating/cooling ring structure that can uniformly and narrowly heat the width in the circumferential direction in high-frequency induction heating bending.

[Summary of the invention]

In contrast to the conventional method of cooling by spraying a coolant near the high-frequency induction heating section, the present invention provides a method of forcibly cooling air by sucking air in a ring shape near the heating section, and a sandwich cooling method that uses a suction type cooling ring and a heating ring. The present invention provides a device having a heating/cooling ring structure that can make the heating width uniform and narrow, and a high-frequency induction heating method using the same.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.

The pipe to be bent 1 is inserted into a high-frequency induction heating coil 3 connected to a high-frequency power source 2 and a suction-type cooling ring 9 without contacting them. An arm 7 fixed at one end to a pushing device 4 that moves in the axial direction of the tube to be processed, passes through a guide roller 5, and is rotatable around a pivot 6 to define the bending radius of the tube.
It is fixed to the clamp device 8 of.

The high-frequency induction heating coil 3 is designed to prevent thermal damage that occurs when high-frequency current flows through the coil.
It is connected to a water supply pump 10 via a water supply pipe 11, and is always cooled by this cooling water when high frequency current is applied. After the cooling water flows through the high frequency induction heating coil, it is drained through the drain pipe 12.

The cooling ring 9 prevents air from flowing in from the space of the high-frequency induction heating coil 3 when the water suction pump 13 sucks air around the pipe surface of the pipe to be bent through the suction pipe 14 into the cooling ring. A valve 15 is provided.

At the same time that a high frequency current is applied from the high frequency power supply 2 to the high frequency induction heating coil 3, the supply of cooling water from the water supply pump 10 to the high frequency induction heating coil 3 is started, and cooling of the high frequency induction heating coil 3 is started. Also, the suction pump 13 starts and the cooling ring 9
Suction of surrounding air starts from then, and cooling of the arm 7 side of the high frequency induction heating coil 3 or the arm 7 side and the pushing device side starts. As a result, the portion of the pipe wall of the pipe to be bent 1 directly below the high frequency induction heating coil 3 is heated to a temperature of 850 to 1050° C. by the hot processing machine. As the temperature begins to rise, the pipe to be bent 1
is pushed forward in the axial direction of the pipe to be bent by the feeding device 4, and rotated around the pivot 6 of the arm 7, which has a set bending radius, as the rotation center to generate a bending moment in the heated part of the pipe to be bent 1. The bending process is then started.

In this embodiment, as shown in FIG. 2, the high-frequency induction heating coil 1 has a structure in which the heat generated in the high-frequency induction coil 1 itself generated when high-frequency current is applied is removed by cooling water supplied from the water supply pipe 2. The cooling ring 4 is sandwiched between the front and rear of the cooling ring 4, which is structured so that air can be sucked from inside the cooling ring 4 through the suction pipe 3. This cooling ring 4 is made of a material such as ceramic that can withstand high temperatures of about 1200°C, and the high-frequency induction heating coil 1 side is composed of the high-frequency induction heating coil 1, the cooling ring 4, and the pipe to be bent 5 during cooling. In order to prevent air from flowing into the cooling ring 4 from the space in which the heating occurs, and to ensure that there is no or very slight cooling of the heated part directly under the high-frequency induction heating coil 1, a valve 6 made of heat-resistant cloth made of ceramic fiber or the like is installed. is attached to the cooling ring 4. Further, gaps Δt ₁ and Δt ₂ are provided between the high-frequency induction heating coil 1 and the opposite side of the cooling ring 4 between the bending process.
Air is forcibly sucked in through this gap, and inside the cooling ring 4, the surface of the pipe to be bent 5 is forcibly cooled. When the gaps Δt ₁ and Δt ₂ are widened or narrowed, the flow rate and flow rate of the air flowing in through the gaps change, and it is possible to change the heat transfer coefficient in forced convection. By changing the heat transfer coefficient, the cooling capacity on the surface of the pipe to be bent 5 can be changed.

Utilizing this property, it is possible to easily perform the next temperature difference imparting bending process. Bending with a temperature difference is characterized in that as the bending radius becomes smaller during bending, the thickness decrease increases on the back side of the bent part, so this is one method to prevent or reduce the degree of thickness loss on the back side of the bent part. known as. In other words, the temperature on the back side of the bending part during bending is
When the temperature is low, such as 500°C, the processing resistance is made higher than the ventral side, thereby reducing the degree of processing thickness loss.

When performing this temperature differential bending process using the present invention, the cooling ring may be set as follows. In other words, as shown in Fig. 4, the cooling rings 2 set on both sides of the high-frequency induction heating coil 1 have a wide gap between the surface of the pipe to be bent and the cooling ring 2 on the back side A of the bending part, and a narrow gap on the ventral side B. By doing so, the amount of air sucked from the back side of the bending part is increased, and the air is sucked intensively on the back side, thereby increasing the cooling ability on the back side. Furthermore, in order to prevent air from flowing into the cooling ring from the high-frequency induction heating coil 1 side, the valve 3 provided on the back side is removed to allow air to flow in from the coil side as well, and to prevent air from flowing into the cooling ring from the high-frequency induction heating coil 1 side. The structure is designed to cool the Thereby, the temperature can be set low on the back side of the bending part and high on the ventral side, and a bending process that imparts a temperature difference can be achieved.

In addition, in the present invention, as shown in FIG.
It is possible to obtain Figures 6 and 7 show the positional relationship and structure of the heating coil and cooling coil when using the conventional cooling method.In the case of the conventional method of injecting coolant from a nozzle, On the other hand, since the coolant is injected from the cooling ring 17 at an angle, the heating part width t of the high-frequency induction heating coil 1 can be narrowed.
It is impossible to cool the tube to be bent until the coolant comes into contact with the tube surface, and an area wider than the coil width is heated to the hot-worked area due to heat conduction from the high-frequency induction heating section. It turns out. FIG. 8 shows an example of measuring the temperature distribution around the high frequency induction heating coil during heating and cooling by air cooling. Even if the width of the heating coil is narrowed to about 6 mm by high-frequency induction, the hot working area in the pipe to be bent will be about 36 mm. Moreover, FIG. 9 is an experimental example showing the deformation resistance of various materials at various temperatures. Processing temperature is 700℃
When it exceeds , the deformation resistance becomes very small, and the heated part is in a state where it deforms more easily than the non-heated part around it. Therefore, with the conventional technology, if we take Figure 9 as an example, a deformation area of about 60 mm is created for a coil width of 6 mm, and for those with a small wall thickness/diameter ratio, buckling or irregularities occur in the heated part during bending. This is a factor that causes deformation.

On the other hand, in the present invention, as shown in FIG. 2, a cooling ring 4 is set immediately next to the high-frequency induction heating coil 1, and the structure is forcedly cooled within the cooling ring, so that the heating width is adjusted according to the coil width. l can be realized.
That is, since cooling is performed from very close to the heating coil as shown in FIG. 5, the hot working area has a width almost close to the width of the heating coil, and the area with low deformation resistance can also be set to a sufficiently narrow width. Buckling and irregular deformation can be prevented.

Although this embodiment shows a sandwich structure of the high-frequency induction heating coil 1 and the cooling ring 4, it is also possible to use this cooling ring in place of a conventional cooling ring, or to change the suction amount of the front and rear cooling rings. By providing a gap between the coil and the cooling ring, it is possible to easily expand the heating section beyond the width of the coil.

FIG. 3 shows an embodiment in which forced cooling is performed by injecting air from the suction port of a suction type cooling ring. This is also possible if the valve is made longer.

〔Effect of the invention〕

According to the present invention, by making the cooling ring a suction type cooling ring structure during high-frequency induction heating and cooling, it is easy to obtain a heating width that corresponds to the coil width, and temperature difference imparting bending processing is realized. Compared to conventional coolant injection methods, there is no local cooling due to coolant scattering, and a uniform heated area can be obtained. Further, by changing the interval between the high frequency induction heating coil and the cooling ring, it is possible to easily change the heating width. Further, even if the width of the high-frequency induction heating coil is the same as the conventional one, it is possible to further cool the width corresponding to the set width of the cooling nozzle, and the heating width can be further narrowed.

[Brief explanation of drawings]

1 and 2 are diagrams showing an embodiment of the present invention,
Figure 3 is a diagram showing an example of use as an air blowing type;
FIG. 4 is a diagram showing a state where the pipe to be bent and the heating coil are eccentric, FIG. 5 is a diagram showing a specific example of the heating width, FIGS. 6 and 7 are diagrams showing a conventional cooling method,
Figure 8 is a diagram showing a specific example of the conventional heating width, Figure 9 is a diagram showing the deformation resistance of various materials, Figures 10 and 1
FIG. 1 is a diagram showing a known processing device. 1... Pipe to be bent, 2... High frequency power supply, 3...
...High frequency induction heating coil, 4...Pushing device, 5...
... Guide roller, 6 ... Pivot, 7 ... Arm, 8 ... Clamp device, 9 ... Cooling ring, 1
0... Water pump, 11... Water pipe, 12... Drain pipe, 13... Suction pump, 14... Suction pipe, 1
5... Valve, 16... Heating section.

Claims (1)

[Claims] 1. A pipe to be bent, whose rear part is fixed by a pushing device and whose front part is clamped by an arm that determines the bending radius, is inserted into the inside of a heating ring connected to a high-frequency power source without touching the ring. , applying high-frequency current to the heating ring to high-frequency heat the portion of the pipe to be bent located inside the heating ring;
The pipe to be bent is pushed forward by a pushing device,
In high-frequency induction heating bending process, which bends a pipe by rotating the arm around the center of rotation with a set bending radius to generate a bending moment in the pipe to be bent, air is formed into a ring shape near the high-frequency induction heating part. A high-frequency induction heating bending method characterized by blowing and processing while forced cooling. 2 In claim 1, the pipe to be bent and the heating ring are eccentrically arranged so as to provide a temperature difference between the bent side and the back side, and the amount of intake air is changed between the bent side and the back side. A high frequency induction heating bending method characterized by: 3. The tube to be bent, whose rear part is fixed by a pushing device and whose front part is clamped by an arm that determines the bending radius, is inserted inside the heating ring connected to a high-frequency power source without touching the ring, and a high-frequency current is applied to the heating ring. is applied to high-frequency heat the part of the pipe to be bent located inside the heating ring, and
The pipe to be bent is pushed forward by a pushing device,
In high-frequency induction heating bending equipment that bends pipes by rotating the arm around the center of rotation with a set bending radius to generate a bending moment in the pipe to be bent, air is forced to be sucked in near the high-frequency induction heating section. A high-frequency induction heating bending device characterized by air-cooled suction type cooling rings attached to both sides of a heating coil in the axial direction. 4. A high-frequency induction heating bending device according to claim 3, characterized in that a valve for blocking air flow is provided on the heating coil side of the inner periphery of the suction type cooling ring. 5. Claim 4 is characterized in that when the pipe to be bent and the heating ring are eccentrically placed so as to provide a temperature difference between the ventral side and the dorsal side, the valve near the dorsal side is removed. High frequency induction heating bending equipment.