JP3160467B2 - Laser device for heating tubular body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating apparatus using a laser beam, and more particularly to a laser apparatus for uniformly heating the inner surface of a tubular body such as a heat exchanger tube.

[0002]

2. Description of the Related Art Since a laser can be heated to a high temperature only in a desired narrow portion and does not exert an extra thermal influence on a peripheral portion, it is widely used for welding, surface hardening and the like. In this type of apparatus, generally, laser light is focused on the surface of a work, and the focused point is scanned according to a predetermined path.
Since sufficient light energy is given to the focal point, the temperature is raised or melted to a desired temperature, and if the focal point moves by scanning, it is quickly cooled.

When the inner surface of a thin cylinder or the inner surface of a thin heat transfer tube is heated by using such a laser device, the laser beam is generally guided in the axial direction by an optical transmission body such as an optical fiber, and the laser beam is guided around the axis. In many cases, the laser light is reflected by a rotating mirror, and the reflected laser light is guided in the radial direction to heat the inner surface.

However, such a general laser inner surface heating apparatus as described above is not suitable for uniformly heating a relatively large area to be heated, and requires a mechanism for rotating a mirror. There is a tendency to be complicated.

For this reason, it has been proposed to use a conical mirror instead of a rotating mirror. However, in this case, due to the characteristics of the conical mirror, the light reflected by the cusp is spread over a wide range and is not very effective for heating.

Therefore, when a conical mirror is used, a frusto-conical surface having a predetermined width is used as a reflecting surface, and when a laser beam is irradiated from a plurality of optical fibers arranged on the circumference to the reflecting surface, a headband is formed on the inner surface of the tubular body. A reflected light illuminated surface is formed and heated.

[0007]

With the laser heating apparatus using the conical mirror as described above, it is possible to achieve the intended purpose and to simultaneously heat the area of the inner surface of the tubular body. There are the following problems.

That is, (1) the light emitted from one optical fiber has a large light energy density at the center due to the nature of the light.
Small in the periphery. Therefore, when a plurality of optical fibers are used, a low-temperature region is generated on the head-shaped work surface, and the temperature varies in the circumferential direction. Such a temperature variation is not preferable for a heat treatment requiring a more uniform temperature distribution than a solution treatment or the like.

(2) The reflection angle of the conventional conical mirror is 9
The angle is 0 degree, and the reflected light is incident on the inner surface of the tubular body at an incident angle of 0 degree. Therefore, the reflectance is high, the heat absorption energy used for heating is small, and the energy efficiency is poor.

(3) The width of the object to be heated on the inner surface of the tubular body is uniquely determined from the shape and size of the conical mirror and the relative relationship with the optical fiber, and cannot be adjusted. It is the point which said. Accordingly, it is an object of the present invention to provide a laser heating apparatus free from the above-mentioned problems.

[0011]

In order to achieve the above object, the present invention is configured as follows. That is, in a laser device that guides laser light to a tubular object to be heated and irradiates the inner peripheral surface of the object to be heated, a flexible light guide means for one system for guiding laser light from a laser light source is provided. A lens optical mechanism comprising a convex lens and a concave lens for variably adjusting the spot diameter of the laser light guided by the flexible light guiding means, and an optical axis aligned with the optical axis of the lens optical mechanism; A laser beam whose spot diameter is adjusted by a mechanism is converted into a funnel-shaped optical path, and a conical lens (axicon lens) for emitting laser light for heating is provided.

Further, the conical lens used is such that the incident angle of the laser beam on the inner surface of the tube to be heated is 70 to 80 °. Further, the lens optical mechanism is configured so that the distance between the lenses can be adjusted.

[0013]

In such a configuration, first, after a laser beam transmitted by one optical fiber is enlarged by an optical system,
The laser beam is collimated, converted into a ring-shaped laser beam that expands in a funnel shape by a conical lens (axicon lens), and radiated onto the inner surface of the tube to be heated. Becomes uniform. Therefore, it becomes possible to uniformly heat the irradiation area in the tube of the laser light.

Second, since the beam incident angle at which the reflectivity of the laser beam can be kept low is 70 to 80 degrees, the beam incident angle of the laser beam on the inner surface of the tube to be heated is reduced. The use of a conical lens designed to output a funnel-shaped laser beam at 70 to 80 degrees increases the beam absorptance of the laser beam, enables efficient heating, and enables optical heating. In particular, the distance between the conical lens serving as the laser beam output end to the heated tube and the portion to be heated of the heated tube can be sufficiently separated, and this can improve the beam absorptivity of the laser beam ( That is, the amount of reflected laser light is reduced), so that thermal damage to the optical system can be prevented.

Third, by changing the combination of the distances between the lenses of the optical system, the width of heating of the inner surface of the tube by laser light irradiation can be variably adjusted. Therefore, the heating width is adjusted by adjusting the heating width in accordance with the heat treatment conditions. And heat treatment with high reliability and high accuracy can be performed.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration diagram of a heating head section which is a tip optical system in a laser heating apparatus of the present invention.

FIG. 1 is a front view showing a schematic configuration of a heating head section, in which 1 is an optical fiber, 2 is a conical lens (axicon lens), and pp is a tube to be heated (hereinafter, a tube to be heated). 3 is a heating target portion, 4 is a heating width, 5 is a laser beam, 6a, 6b and 6c are convex lenses, 7
Is a concave lens, and 8a and 8b are distances between lenses.

The optical fiber 1 is a flexible light guiding means for guiding a laser beam from a laser oscillation source (not shown).
An optical path for one system is provided. One end of the optical fiber 1 is connected to a laser oscillation source. The other end of the optical fiber 1 (laser emission end) is connected to the heating head.
The heating head section includes a convex lens 6a, 6b, 6c, a concave lens 7
And a conical lens 2.

Depending on the application, the optical fiber 1 may be a bundle of a plurality of core wires (bundled), such as an optical fiber, or a configuration having only one core wire. The total number of optical paths is one (one system), and a plurality of optical paths,
The adverse effects of using multiple systems have been eliminated.

That is, by adopting a configuration in which laser light is guided by one optical fiber 1, the number of laser light spots obtained by this light guide path is one, and spots can be obtained for each system as in the case of a plurality of systems. This prevents the energy distribution of the laser beam from becoming extremely dense due to the plurality of spots.

The lens group is arranged from the laser light emitting end side of the optical fiber 1 in the order of the convex lens 6a, the convex lens 6b, the concave lens 7, the convex lens 6c, and the conical lens 2 so that the optical axes are aligned. The positions of the convex lens 6a and the conical lens 2 are fixed, while the positions of the convex lenses 6b and 6c and the concave lens 7 can be adjusted in the optical axis direction.
The optical axis of the lens group is aligned with the optical axis on the laser light emitting end side of the optical fiber 1, and the center of the spot of the laser light is aligned with the optical axis of the lens group.

The conical lens 2 is a frusto-conical lens in which one surface is formed as a flat surface and the other surface is formed as a conical shape. It is as the end side.

The convex lens 6a collimates (collimates) the laser light emitted from the optical fiber 1 so as to spread conically, and the convex lens 6b narrows the collimated laser light to reduce the spot diameter. Numeral 7 spreads the narrowed laser light, and convex lens 6c plays a role of collimating the widened laser light and making it collimate.

As described above, in the present apparatus, the convex lens 6a
The distance between the lens and the conical lens 2 is fixed,
b and the convex lens 6c and the concave lens 7 between them have a configuration in which the position can be adjusted between the convex lens 6a and the conical lens 2. The distance between the convex lens 6b and the concave lens 7 is the lens distance 8a, and the concave lens 7 and the convex lens 6c
Is the inter-lens distance 8b.

In such a configuration, the laser light 5 oscillated from the laser oscillation source is guided to the heating head by the optical fiber 1, emitted from the laser light emitting end side of the optical fiber 1, and made incident on the convex lens 6a. . Then, the light passes through the convex lens 6c via the convex lens 6b and the concave lens 7 from the convex lens 6a, and enters the conical lens 2.

The lens system composed of the convex lenses 6a, 6b and the concave lens 7 is for expanding the luminous flux of the laser light, and the laser light expanded through these lens systems is collimated (parallelized) by the convex lens 6c. And is incident on the conical lens 2.

The conical lens 2 is a frusto-conical lens in which one surface is formed as a flat surface and the other surface is formed as a conical shape. It is as the end side. When a parallel ray is incident on the conical lens 2, the light acts on the center line of the cone so as to bend the light in the surrounding area inward. The laser light incident on the lens 2 has a ring-shaped light distribution, and the diameter of the ring increases as the distance from the conical lens 2 increases.

That is, when the collimated laser beam having a circular cross section passes through the conical lens 2, the collimated laser beam is converted into a beam having a ring-shaped cross section that expands in a funnel shape. Therefore, when the heating head is inserted into the heated pipe, the laser beam becomes a light flux having a ring-shaped cross section that spreads in a funnel shape from the heating head and travels toward the inner wall of the heated pipe. When viewed from above, the laser light is incident obliquely, and the absorption efficiency of the laser light to the heated tube is improved.

As described above, in the apparatus of the present invention, the laser beam 5 transmitted from the laser oscillation source by the optical fiber 1 which is one system of flexible light guide means has the spot diameter by the convex lenses 6a and 6b and the concave lens 7. After being enlarged by a convex lens 6c, the conical lens (axicon lens) 2 at the exit end of the optical system in the heating head unit is formed into a laser light having a ring-shaped cross section that expands in a funnel shape, and the inner surface of the heated tube is exposed. The tube 3 is irradiated with the light to be heated, and the tube is heated from the inner surface.

In the apparatus of the present invention, the optical system (particularly, the conical lens 2 at the exit end of the optical system) is protected from the heat reflected or radiated by the laser light reflected from the object 3 to be heated by the laser light. Therefore, the position of the object to be heated 3 in the tube to be heated, which is an object to be heated with respect to the optical system, is separated in the tube axis direction, and the object to be heated 3 is The laser beam 5 is irradiated so as to be adjusted so that the beam incident angle θ is 70 to 80 degrees.

This can be achieved by selecting the angle of the conical surface of the conical lens 2 and selecting and using a conical lens such that the beam incident angle θ of the laser beam 5 to the object to be heated 3 becomes 70 to 80 degrees. Just do it.

FIG. 2 shows the relationship between the beam incident angle θ (degree) of the laser beam 5 and the reflectance (%). FIG. 2 shows the reflectance% on the vertical axis.
And the horizontal axis represents the beam incident angle θ degrees, and the reflectance is measured and plotted for each beam incident angle θ when a laser beam is incident on nickel at θ degrees.

As shown in FIG. 2, the relationship between the beam incident angle θ (degree) and the reflectivity (%) of the laser beam 5 is such that when the beam incident angle θ is less than 70 degrees, the reflectivity increases. It can be seen that the reflectivity sharply increases when the angle exceeds 80 degrees. Therefore, a region exceeding 80 degrees is a region that is difficult to use because the reflectance greatly changes even if the beam incident angle θ deviates even a little. Therefore, a region where the beam incident angle θ of the laser beam 5 to the object to be heated 3 is 70 to 80 degrees is the most efficient region in terms of reflectivity, so this region is used.

However, when the beam incident angle θ of the laser beam 5 on the heating target section 3 becomes small, the distance between the heating head section and the heating target section 3 becomes too long, which is impractical. When the incident angle θ is large, the distance between the heating head unit and the heating target unit 3 is short, and a problem of heat to the optical system occurs. Therefore, the beam incident angle θ of the laser beam 5 to the heating target unit 3 is small. In the range of 70 to 80 degrees, an optimum beam incident angle θ is selected based on such conditions.

For example, if the distance between the optical system and the object to be heated 3 is less than about 20 mm, there is a great risk that the optical system will be damaged by heat reflected or radiated by the reflected laser light from the object 3 to be heated, If released, about 1,15
Even if the cycle of heating and cooling at 0 ° C. was repeated 300 times, the optical system was not damaged, and the transmittance of the optical system was confirmed by experiments to be good without any change. The beam incident angle θ of the laser beam 5 to the section 3 is 70 to 8
The conical lens 2 is selected so that the distance between the optical system and the heating target portion 3 is at least 20 mm within a range of 0 degrees and in consideration of the diameter of the heated tube.

On the other hand, in the optical system of the heating head, the distance 8a between the convex lens 6a and the concave lens 7 and the distance 8b between the concave lens 7 and the convex lens 6c of the optical system can be changed. First
As shown in the table, the heating width W on the inner surface of the tube to be heated by the laser beam 5 can be arbitrarily adjusted.

(Table 1) Distance between lenses 8a Distance between lenses 8b Beam width (L ₁ mm) (L ₂ mm) (W mm) ---------------------------------------------------------- 13.664 22.000 9.70 14 .129 21.000 8.73 14.546 20.000 7.89 14.907 19.000 7.19 15.223 18.000 6.59 15.502 17.000 6.08 15.749 16.000 5.63 15.971 15.000 5.25 16.171 14.000 4.91 16.352 13.000 4.62 16.516 12.000 4.36 16.666 11.000 4.13 16.13. 803 10.000 3.93 16 .930 9.000 3.76 17.047 8.000 3.60 ------------------------- That is, to be heated It can be seen that the heating width W on the inner surface of the tube can be adjusted in the range of 3.6 mm to 9.7 mm in this example as well.

Next, the apparatus according to the present invention employs an outer diameter of 18.8.
The results of heating a Ni—Cr—Fe alloy tube (nickel-chromium-iron alloy tube) having a thickness of 1.20 mm and a thickness of 1.20 mm to a solution treatment temperature of about 1,100 to 1,200 ° C. are shown in FIGS. It is shown in FIG.

FIG. 3 is a characteristic diagram showing the temperature distribution in the axial direction of the heated tube when the heating width W, which is the irradiation width of the laser beam, is changed according to the width of the heating target portion 3 in the heated tube. The temperature is plotted on the vertical axis, and the length in the tube axis direction is plotted on the horizontal axis. FIG. 4 shows the temperature distribution in the circumferential direction of the tube when the heating width W is changed. The vertical axis represents the temperature, and the horizontal axis represents the circumferential angle of the heated tube. is there.

From these figures, it can be seen that uniform heating was obtained both in the axial direction of the heated pipe and in the circumferential direction of the heated pipe. FIG. 6 shows an example of a heating test performed on the heated pipe pp as the test object in the state shown in FIG. 5 by the method of the present invention. 5A is a side cross-sectional view, and FIG. 5B is a front view of the heated pipe pp. In FIG. 5, the area width of the heated portion of the heated pipe pp which is the test object (the area to be heated) The width of the area is 6 mm, and this is 580 W at the tip of the optical system.
The heating was performed with the laser light 5.

The temperature of the heated portion of the pipe pp to be heated was measured at 0 °, 90 °, 1 ° around the heated portion of the pipe pp.
In order to check the reflection output of the laser beam from the position to be heated by the thermocouples T / C provided on the outer peripheral surface at the positions of 80 ° and 270 °, the end of the heated pipe pp has an axis at the pipe axis. And a power meter PWM for measuring the intensity of the reflected output of the laser beam is arranged.

The distance from the position of the conical lens 2 constituting the optical system of the heating head section to the thermocouple T / C installation surface is about 33.
mm and the power meter PW from the thermocouple T / C installation surface.
The distance to the detection surface of M is 61 mm.

Under these conditions, when the pipe pp to be heated is irradiated with the laser beam, the portion to be heated of the pipe pp to be heated does not show much temperature change until about 30 seconds after the start of the irradiation. The temperature gradient suddenly increases until about 80 seconds after the start of irradiation, and the temperature change increases.
Then, the temperature rises to about 1,200 ° C. all at once until about 90 seconds after the start of irradiation. During this time, the reflection output detected by the power meter PWM is about 0 ° C. at the minimum and about 200 ° C. at the maximum, and the tendency of the change is similar to the temperature change characteristic curve of the portion to be heated.

The magnitude of the reflected output detected by the power meter PWM is small, which means that the laser beam is well absorbed by the heating target and the amount of reflection is small. This means that the heating of is efficiently performed.

As a result, about 1,100 to 1,200 ° C.
It can be seen that the temperature is raised in a short time, and that it can be effectively used as various heat sources such as heat treatment and brazing. In addition, the technology of the present invention is applied to a vertical fixed pipe, a horizontal fixed pipe and a vertical fixed pipe.
The present invention can be applied to a horizontal rotating tube or the like according to the situation. In addition, the present invention is not limited to the above-described embodiment, and can be appropriately modified and implemented without departing from the scope of the invention.

As described above, according to the present invention, the heating head section is as follows. (1) One optical fiber (flexible light guide for one system)
After expanding the laser light emitted from the tube, the light was collimated, converted into a ring shape by a conical lens (axicon lens), and irradiated to the front surface in the tube.

(2) The incident angle of the laser beam to the inner surface of the tube is set to 70 to 80 ° by designing a conical lens (axicon lens) of the optical system. (3) The width of heating by laser light irradiation is changed by changing the combination of the distances between the lenses of the optical system.

By doing so, the first
The laser light transmitted by a single optical fiber is expanded by an optical system, collimated, converted into a funnel-shaped ring-shaped laser light by a conical lens (axicon lens), and heated. Since the irradiation is performed on the inner surface of the tube, the intensity distribution of the laser beam on the inner surface of the tube becomes uniform. Therefore, it becomes possible to uniformly heat the irradiation area in the tube of the laser light.

Second, since the beam incident angle at which the reflectivity of the laser beam can be kept low is 70 to 80 degrees, the beam incident angle of the laser beam on the inner surface of the tube to be heated is reduced. The use of a conical lens designed to output a funnel-shaped laser beam at 70 to 80 degrees increases the beam absorptance of the laser beam, enables efficient heating, and enables optical heating. In particular, the distance between the conical lens serving as the laser beam output end to the heated tube and the portion to be heated of the heated tube can be sufficiently separated, and this can improve the beam absorptivity of the laser beam ( That is, the amount of reflected laser light is reduced), so that thermal damage to the optical system can be prevented.

Thirdly, by changing the combination of the distances between the lenses of the optical system, the width of heating of the inner surface of the tube by laser light irradiation can be variably adjusted. Therefore, the heating width is adjusted according to the heat treatment conditions. And heat treatment with high reliability and high accuracy can be performed. Note that the present invention is not limited to the above-described embodiment, and can be implemented with appropriate modifications without departing from the scope of the invention.

[0051]

As described above in detail, according to the present invention, when heating the inner surface of the tube, the laser beam is guided as a single laser beam, which is formed into a ring shape by a conical lens and irradiated onto the inner surface of the tube. As a result, the inner peripheral surface of the tube can be uniformly heated in a ring shape, and the distance between the optical system and the heating unit tube can be increased, so that thermal damage to the optical system due to the heating target part can be sufficiently prevented. In addition, since the beam incident angle of the laser beam on the inner surface of the tube can be set appropriately, the reflectance of the laser beam can be reduced, and the tube can be efficiently heated. Since the heating width of the light can be freely changed, it is possible to obtain the required heating width and achieve an effect such that the heating can be accurately performed.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention,
FIG. 2 is a diagram illustrating a schematic configuration of a heating head unit (tip optical system) in the laser device according to the first embodiment of the present invention.

FIG. 2 is a diagram for explaining an embodiment of the present invention,
FIG. 4 is a diagram illustrating a relationship between an incident angle of a laser beam and a reflectance according to the first embodiment of the present invention.

FIG. 3 is a diagram for explaining an embodiment of the present invention,
The temperature distribution figure of the axial direction of the pipe concerning a 1st example of the present invention.

FIG. 4 is a diagram for explaining an embodiment of the present invention,
FIG. 4 is a diagram of a temperature distribution in a circumferential direction of the tube according to the first embodiment of the present invention.

FIG. 5 is a diagram for explaining an embodiment of the present invention,
The figure for demonstrating the state of the heating test performed with respect to the pipe pp to be heated.

FIG. 6 is a diagram for explaining an embodiment of the present invention,
FIG. 6 is a diagram showing a relationship between a heating time and a heating temperature in a heating test performed by applying the present invention under the situation shown in FIG. 5.

[Description of Signs] 1 ... optical fiber 2 ... conical lens 2a ... conical mirror 3 ... part to be heated W ... heating width 5 ... optical path 6a, 6b, 6c ... convex lens 7 ... concave lens 8a, 8b ... distance between lenses.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI G02B 27/09 G02B 27/00 E // B23K 101: 06 (72) Inventor Hiroyuki Fujiwara Hirokazu Wadazaki, Hyogo-ku, Hyogo-ku, Kobe-shi, Hyogo Chome 1-1, Mitsubishi Heavy Industries, Ltd., Kobe Shipyard (72) Inventor Takashi Akabane 1-1-1, Wadazaki-cho, Hyogo-ku, Kobe, Hyogo Prefecture Mitsubishi Heavy Industries, Ltd.Kobe Shipyard (56) References -170616 (JP, A) JP-A-2-47221 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 26/00-26/073 C21D 1/34 C21D 9/08

Claims (1)

(57) [Claims] 1. A laser device for guiding a laser beam to an annular object to be heated and irradiating the inner peripheral surface of the object to be heated with a flexible device for guiding laser light from a laser light source. A light means, a lens optical mechanism including a convex lens and a concave lens for variably adjusting the spot diameter of the laser light guided by the flexible light guide means, and an optical axis aligned with the optical axis of the lens optical mechanism,
The optical path of the laser beam whose spot diameter is adjusted by the lens optical mechanism is converted into a funnel shape, and the inside of the heated tube is adjusted.
Angle at which the beam incident angle of the laser beam on the surface becomes 70 to 80 °
A conical lens (axicon lens) for converting the laser beam into a laser beam and emitting the laser beam for heating, and a laser device for heating a tubular body.