KR100730534B1 - Laser heat treatment apparatus and method - Google Patents

Abstract

The present invention relates to a laser heat treatment apparatus and method which can obtain a sufficient heat treatment depth in a short time without melting the surface by a laser beam when laser-heating a round bar such as a valve spool, the laser heat treatment according to the present invention. The apparatus comprises a bed in which a control device and a measuring device are housed; A support installed on one side of the bed to support one side of a workpiece having a circular rod shape; A rotating spindle installed on the other side of the bed so as to face the support, supporting the other side of the workpiece, and being driven to rotate; And a laser oscillation unit which moves along the longitudinal direction of the bed between the support and the rotating spindle, and is provided with a laser for thermally processing a workpiece to be rotated by being supported by the support and the rotating spindle. The laser oscillation part is heat treated by repeatedly performing a predetermined number of times of irradiating and stopping the laser beam for a predetermined time at a temperature below the melting temperature for one heat treatment point while the workpiece is rotated.

Laser heat treatment, valve spool, rotary headstock,

Description

Laser heat treatment apparatus and method

1 is a schematic perspective view of a valve spool heat treated for use in a hydraulic system of heavy equipment such as an excavator.

2 is a schematic perspective view of a laser heat treatment apparatus according to the present invention;

Figure 3 is a graph showing the relationship between the irradiation time and the laser beam of the laser heat treatment method according to the present invention.

4 is a graph showing the relationship between the heat treatment temperature and the time of the heat-treated material according to the irradiation of the laser beam as in FIG.

5 is a graph similar to FIG. 4 according to an experimental example of a laser heat treatment apparatus and method according to the present invention;

(Explanation of symbols for the main parts of the drawing)

1: bed 2: support

3: rotating headstock 4: laser oscillator

5: rail support part 6: rail

7: cylinder 8: piston

9: protruding bearing 10: protruding pin

11, 15: motor 12: mounting base

13: lead screw 14: carriage

16: V block 100: valve spool

The present invention relates to a laser heat treatment apparatus and method, and more particularly, to a laser heat treatment apparatus and method for heat-treating the surface of the bar, such as round bar.

In general, hydraulic systems used in heavy equipment, such as excavators, must provide greater power, so parts such as valve spools used in hydraulic systems of excavators are heat-treated to some depth from the surface. The heat treatment of the valve spool used in the hydraulic system of such an excavator is heat treated by a laser beam.

Laser heat treatment is in principle identical to other heat treatment methods in that it changes the mechanical properties of the steel through heating and cooling. However, due to the skin effect, a heat source called a laser beam is heated to the austenite formation temperature by rapidly heating the material only on the surface, and turning off the laser or moving the material no longer causes the laser energy source. In this case, there is a large difference in that the self-cooling is rapidly caused by the conduction into the material rather than the other effects.

By the laser heat treatment in this manner, the valve spool 100 used in the hydraulic system of the excavator is heat treated intermittently (lattice-shaped) or continuously (strap-shaped) rather than heat-treating the entire surface as shown in FIG. That is, as shown in FIG. 1, the valve spool 100 may be divided into a heat treated portion 101 and an unheated portion 102 in FIG. 1. In the heat treatment of the valve spool 100 by the laser beam, as can be seen from FIG. 1, the part opening and closing the valve port is heat-treated in the entire circumference, but the other parts are heat-treated in the form of a lattice. The heat treatment depth of the valve spool 100 by the laser beam has a depth of approximately 0.6 to 0.7 mm, and the size of the grating has a size of 2 × 2 mm and 3 × 3 mm.

Conventionally, the lattice-shaped laser heat treatment of the valve spool has a problem that the surface of the valve spool is melted by the laser beam when heat-treating the surface of the valve spool to obtain a sufficient heat treatment depth from the surface of the valve spool. In the case of heat-treating the surface of the material at a temperature below the melting temperature of the material to solve the problem of surface melting by the beam, there is a problem that the heat treatment does not reach a sufficient depth with much time.

Accordingly, an object of the present invention is to provide a laser heat treatment apparatus and method capable of obtaining a sufficient heat treatment depth in a short time without melting the surface by a laser beam when a round bar such as a valve spool is laser heat treated.

An object as described above includes a bed in which a control device and a measurement device are accommodated; A support plate installed on one side of the bed to support one side of a workpiece having a circular rod shape; A rotating spindle installed on the other side of the bed so as to face the support, supporting the other side of the workpiece, and being driven to rotate; And a laser oscillation unit which moves along the longitudinal direction of the bed between the support and the rotating spindle, and is provided with a laser for thermally processing a workpiece to be rotated by being supported by the support and the rotating spindle. The laser oscillation part is heat treated by repeatedly performing a predetermined number of times of irradiation and irradiation stop of the laser beam for a predetermined time at a temperature below the melting temperature with respect to one heat treatment point while the workpiece is rotated. It can be achieved by the laser heat treatment apparatus according to an aspect of the present invention.

Alternatively, the laser heat treatment apparatus according to the present invention may further include a V block installed to be moved on a bed between the support and the rotating headstock.

In the above, the laser oscillator preferably has a 50 s first laser beam irradiation and 10-15 s multiple laser beam irradiation operations, and a laser beam irradiation stop method of 10-15 ms between each laser beam irradiation times. Driven by.

The support is provided with a protruding pin that is elastically pressed by a compression spring in the center.

Alternatively, the object as described above comprises the steps of: first irradiating the laser beam for a predetermined time at a temperature below the melting temperature with respect to the first heat treatment point of the first section in the circumferential direction of the workpiece of the circular rod shape; After irradiating the laser beam with the laser beam, the irradiation of the laser beam is stopped for a time shorter than the first laser beam irradiation time, and then the heat treatment point following the primary beam is irradiated in the same manner as the first laser beam irradiation step. Investigating for; After the irradiation of the laser beam is stopped for the time as much as the stop time, another period of the invention is repeated for the first and the next heat treatment points at the same temperature during the first laser beam irradiation. It can be achieved by the laser heat treatment method according to the aspect.

In the above, the irradiation time of the laser beam other than the primary laser beam irradiation is shorter than the irradiation time of the primary laser beam.

In the above, the primary laser beam irradiation time is 50 ms, the subsequent laser beam irradiation time is 10-15 ms, and the laser beam irradiation stop time between each laser beam irradiation times is 10-15 ms.

The laser beam is irradiated to the rotating workpiece, moves in the longitudinal direction of the workpiece after heat treatment of the first section in the circumferential direction, and the above steps are repeated.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

2 is a schematic perspective view of a laser heat treatment apparatus according to the present invention. As shown in FIG. 2, the laser heat treatment apparatus according to the present invention is installed on one side of the bed 1 and the bed 1 to support a workpiece having a circular rod shape, that is, one side of the valve spool 100. Is installed on the other side of the bed (1), the rotary spindle (3) for supporting the other side of the valve spool 100, the bed (between the support (2) and the rotary spindle (3) And a laser oscillation part 4 moving along the longitudinal direction of 1). The bed 1, the support 2, the rotating headstock 3 and the laser oscillation portion 4 as described above are configured in a modular manner, the structure of which can be independently changed as necessary.

The bed 1 is made in the form of a table, as shown in the drawing, in which a control device and a measuring device for controlling the laser heat treatment device according to the present invention are accommodated. The support 2, the rotating spindle 3 and the laser oscillation part 4 are controlled by the control apparatus accommodated in the bed 1.

The support 2 has a protruding bearing 9 for supporting the end face of the valve spool 100 at the inner end face center portion and extends in the longitudinal direction of the bed 1 from one side of the bed 1. In the rail support part 5 installed, it is slidably installed in the longitudinal direction of the bed 1. That is, the support 2 is slidably coupled with the rail 6 installed on the rail support 5, and one end surface of the support 2 is a piston of the cylinder 7 fixed on the rail support 5. Connected to (8). The protruding bearing 9 is elastically pressed by a compression spring (not shown) built in the support 2 to elastically press and support one end of the valve spool 100.

Rotating headstock (3) installed on the bed (1) facing the support (2) is a protruding pin protruding to a length of about 10 mm to support the other end surface of the valve spool 100 in the center portion thereof ( 10 is provided and rotatably installed on the mount 12 to be rotated by the motor 11. Therefore, when the valve spool 100 is installed between the rotation headstock 3 and the support 2, the rotational force of the rotation headstock 3 rotated by the motor 11 is transmitted to the valve spool 100. The valve spool 100 is rotated at a predetermined rotational speed. When the valve spool 100 is rotated by the drive of the rotary headstock 2, since the protruding bearing 9 is provided in the support 2 which supports one end of the valve spool 100, the valve spool ( 100 may be prevented from rotating resistance by the support (2).

On the other hand, the laser oscillation part 4 provided between the support stand 2 and the rotating spindle 3 is installed in the carriage 14 provided in the lead screw 13 provided along the longitudinal direction of the bed 1. The lead screw 13 is rotated by the motor 15, and the carriage 14 moves in the longitudinal direction of the bed 1 by the rotation of the lead screw 13.

On the other hand, when the valve spool 100 is loaded on the rotary headstock 3 and the support 2, the valve spool 100 is placed on the V block 16 located in the bed 1 between the rotary headstock 3 and the support 2. Is located. When the valve spool 100 is located in the V block 16, the V block 16 is raised or moved forward or backward so that the valve spool 100 can be loaded by the support 2 and the rotary spindle 3. In movement, the center of the valve spool 100 is positioned to coincide with the center of the protruding pin 10 of the rotary spindle 3 and the protruding bearing 9 of the support 2. This V block 16 may be appropriately selected depending on the diameter of the valve spool 100 to be heat treated.

Irradiation of the laser beam to the valve spool 100 by the laser oscillation unit 4 is made when the valve spool 100 is rotated at a predetermined speed in a state supported by the rotating spindle 3 and the support 2. . The intensity of the laser beam is such that the valve spool 100 is not melted by the laser beam. For example, as shown in FIG. 1, when the portion to be heat-treated in the L1 section of the valve spool 100 is five lattice portions, the laser oscillation part 4 is rotated without being fed by the rotation of the lead screw 13. Heat treatment is performed in the L1 section of the valve spool 100.

The heat treatment of the L1 section by the laser oscillation section 4 is performed by the operation of the laser oscillation section 4, as shown in FIG. 3, when the heat treatment section 101 is heat treated, and the laser oscillation section 4 is stopped. In the state where the heat treatment is not performed, the laser oscillation part 4 is operated again, so that the next part is heat treated.

As described above, the laser oscillator 4 repeats operation and stop of the predetermined time in order to heat-treat the valve spool 100 in a lattice shape. That is, the laser oscillation part 4 is, for example, to prevent the surface melting of the valve spool 100 due to heat treatment as shown in FIG. It is driven in the manner of irradiation stop (cooling) of irradiation time and 10-15 ms time between each irradiation time. The surface temperature of the valve spool 4 by the laser beam irradiation in the first section t1 of FIG. 3 is heated to a temperature near the melting point of the valve spool 100. However, the temperature of a predetermined depth from the surface of the valve spool 4 does not reach the heat treatment temperature and is heated to a temperature below the heat treatment temperature.

In this state, the laser oscillator 4 is momentarily stopped from operating, and the valve spool 100 is rotated so that when the section t2 reaches the position of the laser oscillator 4, the laser oscillator 4 is predetermined. Operating for a time, the laser beam is irradiated so that the laser beam performs heat treatment on the section t2 in the same manner as the section t1. Therefore, the section t2 also has a temperature of a predetermined depth from the surface of the valve spool 4, but does not reach the heat treatment temperature, and is heated to a temperature lower than the heat treatment temperature, so that the laser beam irradiation from the laser oscillator 4 And the irradiation stop is repeated. By the laser heat treatment apparatus and method according to the present invention as described above, although there is a difference depending on the material of the valve spool 100, it takes about 1 minute 30 seconds to heat-treat one valve spool 100.
That is, the laser oscillation unit 4 summarizes the process of heat-treating each section of the valve spool 100 as follows.
In FIG. 1, the laser oscillator 4 (see FIG. 2) is first positioned in the L1 section. At this time, the laser oscillation unit 4 is irradiated and stopped irradiating the laser beam for a predetermined time as shown in Fig. 3, the valve spool 100 is circumferentially by the rotating spindle (3, see Fig. 2) In the direction of rotation, the L1 section is the heat treatment place 101 and the non-heat treatment place 102 will appear repeatedly. Next, the laser oscillation part 4 moves to the L2 section of the valve spool 100 by the rotation of the lead screw 13 (refer FIG. 2). Similarly to the above, in the L2 section, the valve spool 100 rotates in the circumferential direction, and the laser oscillation unit 4 irradiates the laser beam at a predetermined time interval as shown in FIG. do.

FIG. 4 is a graph showing a relationship between heat treatment temperature and time of a material to be treated according to irradiation of a laser beam as in FIG. 3.

As shown in FIG. 4, when the laser beam is irradiated once to the first section t1 of the valve spool 100 by the operation of the laser oscillator 4, the surface of the valve spool 100 is irradiated with the laser beam. While heated to a heat treatment temperature without melting by means, the first depth portion of a certain depth, for example, 0.25 mm deep and the second depth portion 0.6 mm, is heated to a constant temperature without reaching the heat treatment temperature. It can be seen that. The first depth portion below the surface of the valve spool 100 is heated to a temperature higher than the second depth portion below it.

In this state, by the rotation of the valve spool 100, the laser oscillator 4 is operated to perform heat treatment for the next section t2 to irradiate the laser beam to the next section t2. Accordingly, in the section t2, like the section t1, the surface of the valve spool 100 is heated to a heat treatment temperature without melting by irradiation of a laser beam, while the first and second depth portions from the surface It is heated to a constant temperature without reaching the heat treatment temperature.

On the other hand, after the operation of the laser oscillator 4 is stopped, the valve spool 100 is continuously rotated while being supported by the rotation spindle 3 and the support 2, whereby the laser beam is spooled 100. Are repeatedly irradiated to the intervals t1, t2 ..). While the laser beam is repeatedly irradiated to the sections t1, t2 ..., the surface of the valve spool 100 is irradiated with the laser beam repeatedly while the surface of the valve spool 100 is maintained at the heat treatment temperature without melting by the initial laser beam. The first and second depth portions of the valve spool 100 may be heated to the heat treatment temperature, thereby heat treatment to the required heat treatment depth.

On the other hand, the irradiation and stop time of the laser beam as described above is made for a time of ㎳ unit, the number of irradiation is determined according to the material to be heat-treated, that is, the material of the valve spool 100, the transfer of the laser oscillation portion (4) It is also determined according to the material of the valve spool 100 and laser heat treatment conditions. Therefore, the laser oscillation part 4 continuously moves in the longitudinal direction of the bed 1 by the drive of the lead screw 13 while irradiating the laser beam to the valve spool 100 which is rotating the laser beam.

Experimental Example

The inventor of the present invention, in order to increase the productivity of the laser heat treatment, after heating as close to the melting point of the valve spool 100 of the maximum temperature, that is, the workpiece as soon as possible with the maximum output power of the laser heat treatment apparatus according to the present invention, the valve spool 100 When the surface temperature of the? Reaches near the melting point, the operation of the laser oscillator 4 is stopped, and after thermal energy of the surface of the valve spool 100 diffuses into the valve spool 100, the laser oscillator 4 is again turned on. A method of irradiating a laser beam to the valve spool 100 by driving was applied. At this time, the intensity of the laser beam was 60 W / mm 2.

The maximum temperature by the irradiation of the laser beam is that the melting temperature of the valve spool 100 having a carbon content of 0.40 to 0.43% is about 1470 ° C and the thermal effect accumulated due to laser heat treatment is in the range of about 50 ° C to 100 ° C. In consideration, 1300 ° C. was assumed as the upper limit temperature in order to prevent surface melting of the valve spool 100. Under these conditions, the first laser beam irradiation time for one point (3 x 3 mm) of the valve spool 100 was 50 ms, and the irradiation of the laser beam was stopped (cooled) for 5 ms after the first irradiation. Afterwards, the laser beam was irradiated for 15 ms again, and the laser beam was irradiated several times in this manner, and as a result, temperature changes occurred at the surface and the first and second depths as shown in Tables 1 and 5. .

TABLE 1

Time order From FEM results From the interpolation calculation result surface First depth 2nd depth 0.3 mm 0.35 mm 0.4 mm Maximum temperature of the first irradiation (50㎳) 1273.3 791.1 467.6 742.5 694.0 645.4 Maximum temperature of secondary irradiation (5 + 15 = 70㎳) 1374.8 885.2 536.6 832.9 780.6 728.3 3rd irradiation maximum temperature (5 + 15 = 90㎳) 1470.5 974.2 596.3 917.5 860.8 804.1 Maximum temperature of secondary irradiation (5 + 15 = 110㎳) 1554.4 1058.4 651.3 997.3 936.3 875.2 Maximum temperature of secondary irradiation (5 + 15 = 130㎳) 1627.8 1137.0 705.5 1072.3 1007.5 942.8

As can be seen from the experimental results, since the laser energy is excessively irradiated in this experiment, a problem has already arisen that the surface exceeds the melting temperature in the fourth laser beam irradiation, and for this reason, the first laser beam irradiation time It is preferable not to exceed 50 Hz. On the other hand, since the surface of the valve spool 100 receives sufficient energy, the temperature increase of the second depth is very fast, and as a result, at a depth of 0.3 mm, the temperature has already reached a temperature sufficient for heat treatment only by the secondary laser beam irradiation, and 0.35 mm. In, it can be seen that the heat treatment temperature is reached during the third laser beam irradiation. In the 4th laser beam irradiation, it reached a temperature sufficient for heat treatment to a depth of 0.45 mm, but since the surface has already reached the melting temperature, it is not meaningful, but it can be seen that the heat treatment temperature reaches a sufficient depth in a short time.

According to the laser heat treatment apparatus and method according to the present invention as described above, when the heat treatment of the round bar, such as the valve spool in the form of a lattice, it is possible to obtain a sufficient heat treatment depth in a short time without melting the surface by the laser beam.

Claims (8)

A bed in which the control device and the measurement device are accommodated; A support installed on one side of the bed to support one side of a workpiece having a circular rod shape; A rotating spindle installed on the other side of the bed so as to face the support, supporting the other side of the workpiece, and being driven to rotate; And A laser oscillation unit moving along the longitudinal direction of the bed between the support and the rotating spindle, and provided with a laser to heat-treat the workpiece rotated by being supported by the support and the rotating spindle; The laser oscillation part is heat treated by repeatedly performing a predetermined number of times of irradiation and irradiation stop of the laser beam for a predetermined time at a temperature below the melting temperature with respect to one heat treatment point while the workpiece is rotated. Laser heat treatment device. The laser heat treatment apparatus according to claim 1, further comprising a V block installed to be moved on a bed between the support and the rotating spindle. 2. The laser oscillation unit according to claim 1, wherein the laser oscillation unit stops 50 ms of primary laser beam irradiation and 10-15 ms of multiple laser beam irradiation operations, and 10-15 ms of laser beam irradiation between respective laser beam irradiation times. Laser heat treatment apparatus characterized in that driven in a manner. The apparatus of claim 1, wherein the support is provided at a central portion thereof with a protrusion pin elastically pressed by a compression spring. Firstly irradiating a laser beam for a predetermined time at a temperature below a melting temperature with respect to the first heat treatment point of the first section in the circumferential direction of the circular rod-shaped workpiece; After the laser beam irradiation of the laser beam is stopped, the irradiation of the laser beam is stopped for a time shorter than the first laser beam irradiation time, and then, in the same manner as the first laser beam irradiation step, the laser beam is moved to the next heat treatment point. Investigating; And after the irradiation of the laser beam is stopped for the time as much as the stop time, the laser heat treatment method is repeated a predetermined number of times for the first and the next heat treatment points at the same temperature during the first laser beam irradiation. The laser heat treatment method according to claim 5, wherein an irradiation time of a laser beam other than the primary laser beam irradiation is shorter than an irradiation time of the primary laser beam. The method of claim 5 or 6, wherein the first laser beam irradiation time is 50 ms, the subsequent laser beam irradiation time is 10-15 ms, the laser beam irradiation stop time between each laser beam irradiation times is 10 Laser heat treatment method characterized in that -15㎳. 6. The laser heat treatment method according to claim 5, wherein the laser beam is irradiated to the rotating workpiece and moved in the longitudinal direction of the workpiece after the heat treatment of the first section in the circumferential direction, wherein the steps are repeated.

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