JP5020613B2 - Laser processing apparatus and processing method - Google Patents

Description

  The present invention relates to a laser processing apparatus and a processing method for performing microhole processing on the surface of a rolling roll of a metal steel strip using a laser oscillator such as a semiconductor laser excitation solid-state laser oscillator.

  For example, [Patent Document 1] discloses a processing technique that significantly improves the rolling life of a roll by performing dimple-shaped dull processing on the surface of the rolling roll of a metal steel strip with a pulse laser. Furthermore, [Patent Document 2] discloses a dimple-like hole machining apparatus and method on the surface of a rolling roll using a semiconductor laser pumped solid-state laser.

In [Patent Document 3], by selectively blocking the irradiation at the rising or falling part of the laser oscillation, the shape of the side surface of the hole is formed in the drilling process of the epoxy material or the like of the printed circuit board to be processed. A processing technique for forming a mold close to a straight line is disclosed.
JP-A-8-155506 JP 2006-136920 A JP 2004-82131 A

  As will be described later, the roll surface is subjected to dimple-shaped dull processing by a pulse laser, and the rolling life of the roll is determined by the amount of roll regrind performed to remove the fatigue layer on the roll surface after rolling. It is important to take into account the so-called roll basic unit to reduce the cost of the rolling roll for rolling. If the dimple hole processing depth is too deep, it is necessary to perform grinding more than necessary, that is, grinding more than removing the fatigue layer, to reach the lower limit of the roll radius that can be used in the rolling mill. Until then, the number of repeated use of rolling, grinding, and dimple hole processing is reduced, resulting in deterioration of the roll basic unit. Even if the rolling life is extended by dimple drilling and the frequency of roll replacement and roll grinding is reduced, the effect is offset by an increase in the amount of grinding performed at one time. Does not lead to reduction. However, the above [Patent Document 1] and [Patent Document 2] do not describe a technique for controlling the depth of a dimple hole to be processed in order to improve the roll unit.

  Further, the processing technique described in [Patent Document 3] is not a processing technique for controlling the pulse width of the laser beam to be irradiated and controlling the depth of the processed hole. Furthermore, in the above [Patent Document 3], when laser processing is performed on the workpiece surface over a wide range, the positional relationship between the laser beam deflection direction and the laser beam scanning direction is not clearly shown. When the laser beam is deflected by using a deflecting element in the latter half of the pulse oscillation during irradiation of the pulse laser and the latter half of the pulse oscillation is interrupted, the laser optical axis changes according to the beam deflection operation. The laser condensing position on the workpiece surface by the lens changes.

  Furthermore, the above is applied to roll processing. The dimple hole processing is performed by irradiating the rotating roll surface with laser light. For this reason, as shown in FIG. 6, when the direction of change of the condensing position of the laser beam due to deflection is not parallel to the roll circumferential direction (arrow direction shown in FIG. 6), for example, parallel to the roll axis direction, dimples are used. (Processing hole) 40 is processed in the roll axis direction. FIG. 6 is a view of the processed portion of the roll surface as viewed from above. The dimple opening 40 in which processing is progressing moves in the direction of the arrow as the roll rotates. At this time, the laser beam spot focused and irradiated on the roll surface moves from the irradiation position SP1 to the irradiation position SP2 by deflection scanning.

  As shown in FIG. 6, the irradiation position SP <b> 2 on the rolling roll advances in a direction perpendicular to the direction in which the drilling progresses (the direction of the arrow shown in FIG. 6), and so to speak, is at the side part of the drilling. That is, the beam that is moving at high speed on the surface of the roll is scanned by deflection with respect to the new surface after grinding of the roll in which the drilling has not progressed. In such a case, since processing with an inappropriate laser intensity density is performed (FIG. 6), the amount of melt generated in the laser irradiation portion increases and a rim is formed around the dimples. When rolling a metal steel strip with a roll having a lot of melted rims attached thereto, problems such as generation of wrinkles on the surface of the metal steel strip and failure to obtain a good metal steel strip occur.

  The present invention has been made in view of the above problems, and when performing dimple-like drilling on a rolling roll surface of a metal steel strip using a pulse laser, the amount of grinding for roll wear by rolling and removal of the fatigue layer In view of the above, a laser processing method and a laser processing apparatus for controlling the processing depth of the dimple-shaped processing hole are provided in order to extend the rolling life of the roll and maximize the roll basic unit.

In order to solve the above-mentioned problem, according to the present invention, in the laser processing method of a rolling roll, the surface of the rolling roll for rolling a metal steel strip is irradiated with laser light to form a processing hole in the rolling roll. N is a positive integer which is the number of times of rolling, δ is a reduction amount of roll radius caused by wear by rolling the metal steel strip by a specified amount by the rolling roll, and the rolling roll is rolled by the metal steel strip. Provided is a laser processing method for a rolling roll, characterized in that a processing hole having a processing depth h defined by the following formula (1) is formed with the thickness of the fatigue layer formed on the surface as ε.
N × δ + (N−1) × ε <h <N × (δ + ε) (1)

  In the laser processing method, the processing depth at the time of forming the processed hole may be controlled by controlling the irradiation time of the laser light applied to the surface of the rolling roll.

  In the above laser processing method, laser light oscillated by pulse excitation is used as the laser light, and oscillation is performed from a laser oscillator that outputs laser light when controlling the irradiation time of the laser light irradiated on the surface of the rolling roll. It is determined that the pulse energy from the start of oscillation has reached a preset value by integrating the waveform of the relaxation oscillation pulse, and the latter half of the relaxation oscillation pulse that the laser beam continues is cut off, The irradiation time may be controlled.

  In the laser processing method, when controlling the irradiation time of the laser beam irradiated on the surface of the rolling roll, the laser beam is changed so that the irradiation position of the laser beam on the surface of the rolling roll changes in the circumferential direction of the roll. The irradiation time of the laser beam may be controlled by deflecting and switching between the laser beam blocking state and the non-blocking state.

  Moreover, according to the present invention, there is provided a laser processing apparatus for a rolling roll that irradiates a surface of a rolling roll for rolling a metal steel strip with laser light to form a processing hole in the rolling roll, and outputs the laser light. A laser oscillator that performs a relaxation oscillation of the laser oscillator by pulse excitation, deflects the laser light output, a damper that blocks the laser light deflected by the deflection element, and a relaxation oscillation of the laser light A detector that detects the start, an integrator that integrates the signal of the detector, and a control system that controls the deflection element based on a trigger signal from the integrator, and the deflection element comprises: A laser processing apparatus for a rolling roll, characterized in that, when the laser light is deflected, the irradiation position of the laser light on the surface of the rolling roll is arranged to change in the circumferential direction of the roll. It is provided.

  By the processing method and processing apparatus of the present invention, it is possible to extend the rolling life of the rolling roll of the metal steel strip, minimize the rolling roll grinding amount after rolling, and greatly reduce the roll cost related to the rolling of the metal steel strip. it can.

  First, the depth of a processed hole when forming a processed hole on the surface of a rolling roll using a laser beam by the processing method according to the embodiment of the present invention will be described.

  In the processing techniques of Patent Document 1 and Patent Document 2 described above, since the frictional force necessary for rolling is ensured by the peripheral edge portion of the dimple-shaped processing hole on the roll surface, the roll surface is worn by continuing rolling, Before the dimple-like processed hole disappears, the rolling roll is replaced as the rolling life. At that time, a fatigue layer of about 20 to 30 μm (roll radius value) is formed on the roll surface layer after rolling by rolling. Even if dimple holes remain, grip force is ensured and stable rolling is possible, there is a risk of rolling trouble such as cracks on the roll surface due to the fatigue layer and wrinkling on the steel sheet surface. Therefore, even when the grip force is maintained, it is necessary to perform roll exchange after rolling a certain amount of steel sheet. The surface of the roll used for rolling is used again for rolling after removing the fatigue layer by grinding.

  The size that can be used by the rolling mill is determined as the diameter of the rolling roll used in the rolling mill. The smaller the amount of roll grinding after rolling, the more times the roll is repeatedly used. The so-called roll basic unit is reduced, and the manufacturing cost of the metal steel strip can be reduced. When the dimple-like hole depth remaining at the end of rolling is larger than the fatigue layer thickness, grinding that removes only the fatigue layer results in a dimple mark remaining on the roll surface. If the dimple drilling by laser is performed again in a superposed manner, the roll has a large friction coefficient exceeding the friction coefficient suitable for rolling, and cannot be used for rolling a steel sheet. Therefore, in this case, it is necessary to make the amount of reduction of the roll radius by grinding larger than the fatigue layer thickness, and to perform roll grinding to a depth at which the dimple marks disappear by laser processing, and the grinding amount per time increases. The roll basic unit deteriorates.

  On the other hand, in the processing method according to the embodiment of the present invention, the amount of decrease in the roll radius by grinding is reduced to the fatigue layer thickness ε so as to minimize the roll regrind amount after completion of rolling and improve the roll basic unit. To be equal. For this purpose, the dimple hole depth to be imparted to the roll surface is the sum of the reduction amount δ of the roll radius due to wear caused by rolling and the reduction amount ε of the roll radius due to grinding (δ + ε) at the end of the intended rolling. Need to be smaller than. On the other hand, when the dimple-like hole depth h remaining at the end of rolling is shallower than the roll radius reduction amount δ due to wear caused by rolling, the rolling grip force of the roll is reduced during rolling and rolling is unstable. become. The dimple hole depth needs to be deeper than the roll radius reduction amount δ due to wear caused by rolling.

Therefore, in the series of cycles in which the ground surface of the roll is dimpled with a laser, the metal strip is rolled, and the fatigue layer is removed again, the depth of the dimpled hole that is most effective for improving the roll basic unit is obtained. It is desired that the range is defined by the following formula. That is, the dimple hole depth h is required to have an accuracy of about 10 to 30 μm, which is the same as the fatigue layer thickness ε expressed by the following equation (2).
[delta] <h <[delta] + [epsilon] (2)

In the above description, the case where the dimple-like hole processing by laser is performed again for each roll surface grinding after the end of rolling has been described. However, if the depth of the dimple hole drilled by laser remaining after grinding only after rolling is deeper than the amount of roll radius reduction due to wear caused by the next rolling, the roll surface by the laser after grinding It is possible to maintain the rolling grip force without performing dimple-like hole machining on the steel sheet. That is, the next rolling can be performed without performing dimple-shaped hole machining. If the dimple depth h by laser processing satisfies the following equation (3) using the equation, rolling N times can be continued.
N × δ + (N−1) × ε <h <N × (δ + ε) (3)

  Here, N is a positive integer. The left side of the above equation (3) is the sum of the roll wear amount N × δ generated by N rollings and the grinding amount (N−1) × ε performed at the end of each rolling, and the N rolling end point (N The amount of decrease in the roll radius is shown before grinding after the second rolling). The right side of the above equation (3) is a reduction amount of the roll radius caused by N times of rolling and grinding.

  As described above, when the dimple hole depth h by laser processing satisfies the above formula (3), only roll grinding for removing the fatigue layer on the roll surface is repeated by laser processing on the roll surface once. This means that the rolling can be performed N times in the treatment, and the laser processing frequency on the roll surface can be reduced to 1 / N. In this case, the steps related to laser processing can be omitted, and the cost for roll maintenance can be greatly reduced.

  Even in this case, the laser dimple hole depth h is required to have a processing depth accuracy equivalent to the fatigue layer thickness ε due to rolling, which is the difference between the left side and the right side of the above equation (3). Furthermore, the amount of wear on the surface of the rolling roll varies depending on the amount of reduction, and in a tandem rolling mill, generally the wear of the former roll is large and the wear of the latter roll is small. Therefore, the roll radius reduction amount δ due to wear defined by the above formula (2) differs for each stand of the tandem rolling mill, and the ideal dimple processing depth h differs for each stand used. In a typical 5 to 6 stand tandem rolling mill, the amount of wear for each stand differs by about 10 μm per rolling unit.

  Therefore, in order to maximize the rolling life of each stand and minimize the roll basic unit, it is necessary to have process controllability that creates a dimple hole depth with an accuracy of about 10 μm. Great effect on cost reduction.

  Next, when carrying out the laser processing method of the present invention, the dimple hole depth h is controlled to the above target value by using the laser processing apparatus 100 according to the embodiment of the present invention instead of the conventionally known processing apparatus. The reason why this is possible will be described below.

  According to the results of investigations of conventionally known processing techniques by the inventors, in a semiconductor pumped solid-state laser having an output of 100 to 1 kW class necessary for processing a rolling roll, the pumping semiconductor laser is driven by pulse oscillation to drive a solid-state laser. In the method of relaxing oscillation, the variation of the relaxation oscillation pulse is large. 3A and 3B are signals obtained by detecting a relaxation oscillation pulse under the same excitation condition with a photodiode, and the vertical axis is a detection signal level (mV) of the photodiode. The energy in the relaxation oscillation pulse shown in FIGS. 3A and 3B is proportional to the area of the signal waveform. The detection signal intensity corresponding to the laser intensity density contributing to the processing is S1, and the signals exceeding S1 are integrated for the waveforms in FIGS. 3A and 3B, and Ea and Eb in FIG. (Broken line). From FIG. 3 (c), it can be seen that in the pulses of FIG. 3 (a) and FIG. 3 (b), there is almost twice the energy difference in the laser energy contributing to processing.

  On the other hand, if the condensing state of the laser beam at the processing point is the same, the removal volume of the processed dimple hole is proportional to the energy in the relaxation oscillation pulse to be irradiated. Furthermore, when the condensing of the laser beams is the same, the opening diameters of the dimple holes are almost the same, so that the processing depth is almost proportional to the irradiation energy. This is because the dimple hole depth varies about twice in the dimple hole processing of the roll in the relaxation oscillation pulses shown in FIGS. 3 (a) and 3 (b). That is, when FIGS. 3A and 3B show the maximum and minimum pulse output of the relaxation oscillation pulse, when the dimple hole processing with the processing depth of 60 μm is performed on the roll surface, the processing depth is This means that variations in depth of about 40 μm to about 80 μm and about 40 μm occur. If the integrated value of the signal intensity corresponding to the machining energy required to obtain the target machining depth is Eo, in FIG. 3C, the pulse width τa in the waveform of FIG. In the waveform b), it is necessary to block the laser pulse with the laser pulse width τb.

  As described above, the processing depth of the dimple hole on the roll surface described above can be set to an accuracy of about 10 μm only by controlling the driving time width of the excitation semiconductor laser as in the case of using a conventionally known processing technique. It is impossible to control. Therefore, in the present embodiment, the processing method of the present invention is implemented using a laser processing apparatus 100 according to the embodiment of the present invention described below.

  FIG. 1 shows a partial configuration diagram on the laser oscillation side of a laser processing apparatus 100 according to an embodiment of the present invention. As the laser oscillator, a semiconductor laser pumped YAG laser oscillator 1 which is a semiconductor laser pumped solid-state laser that has come to be widely used in industry is used. The drive current of the pumping semiconductor laser of the YAG laser oscillator 1 is controlled as an approximately rectangular current by a controller (not shown) by ON / OFF control or switching control of two current levels. An acousto-optic element (hereinafter referred to as an AO element) is used as the YAG laser beam deflecting element 14.

  Laser light 3 emitted from the YAG laser oscillator 1 is transmitted by transmission mirrors 4 and 5. An ND filter 7 and a narrow-band optical filter 6 that transmits the YAG laser wavelength light and blocks the pumping semiconductor laser light and a photodiode 10 are installed behind the rear mirror 2 of the oscillator 1 to detect the oscillation of the YAG laser pulse. To do. The detection signal of the photodiode 10 is amplified by the amplifier circuit 11 and transmitted to the integrator 12. The integrator 12 integrates a detection signal having a value equal to or larger than a preset threshold value, and controls the AO element 14 as a trigger signal that becomes an end signal when the integral value reaches a predetermined value. The driving power is supplied to the AO element 14 from the driver 13 based on the trigger signal, and the AO element 14 is operated. The AO element 14 is installed in the laser beam path, and the beam damper 15 is installed in the vicinity of the laser beam path.

  The AO element 14 is normally stopped, and the laser beam path (optical axis) is set to the non-blocking position L shown in FIG. In the position L in the non-blocking state, the laser beam can reach the rolling roll 30 via the transmission mirror 5 without being blocked. The AO element 14 is configured to be switchable so as to deflect the laser beam optical axis from the position L to a position L ′ that is in a cut-off state. In the present embodiment, the AO element 14 is driven only for the time during which the drive signal of the driver 13 is input, and is switched to the position L ′ where the laser beam is in a cutoff state. When the optical axis of the laser beam is deflected to the position L ′ by driving the AO element 14 in this way, the laser beam is interrupted by the damper 15, so that the irradiation of the laser beam to the rolling roll 30 is interrupted.

  The threshold value is set when integrating the detection signal of the relaxation oscillation pulse from the photodiode 10 in order to integrate only the energy of the relaxation oscillation pulse portion that has a certain output intensity and contributes to the processing.

  The laser beam 3 emitted at the position L is transmitted by the transmission mirror 21, guided to the condenser lens 22, and condensed as shown in the partial configuration diagram of the apparatus 100 on the laser irradiation side shown in FIG. The surface of the rolling roll 30 is irradiated. A processing assist gas such as dry air is injected from the processing nozzle 23 coaxially with the laser beam 3.

  The rolling roll 30 is rotated at a constant rotational speed by a rotating device, and the transmission mirror 21, the condenser lens 22, and the processing nozzle 23 are moved at a constant speed by a uniaxial moving table 31 that moves parallel to the axial direction of the rolling roll 30. In addition, fine hole processing can be performed on the entire surface of the rolling roll 30.

  The XYZ axes are appended to FIGS. 1 and 2, but in FIG. 1, the deflection direction of the optical axis L and the optical axis L ′ is the XZ plane. The beam deflection in the XZ plane in FIG. 1 is converted into the deflection in the XY plane by the transmission mirror 12 in FIG. 2, and thus is parallel to the roll circumferential direction. The fluctuation direction of the condensing laser is also parallel to the roll circumferential direction.

  At this time, as explained in the above [Background Art], the laser beam in the deflection process is also condensed on the bottom of the hole due to the multiple reflection on the side surface of the dimple hole, so Even if the state of the laser beam changes, the dimple hole is processed well.

  FIG. 5 is a schematic diagram showing a state in which the direction in which the irradiation position of the laser light moves on the surface of the rolling roll is the same as the roll rotation by deflection scanning. Fig.5 (a) is the figure which looked at the process part of the roll surface from upper direction. FIG. 5B is a cross-sectional view of FIG. The dimple opening 40 in which processing is progressing moves in the direction of the arrow as the roll rotates. As described above, when the direction of change of the laser beam condensing position due to deflection is parallel to the roll circumferential direction, the roll surface has already been drilled and the beam position moves in the same direction as the drilling. . At this time, the laser beam spot focused and irradiated on the roll surface moves from the position of the irradiation position SP1 to the position of the irradiation position SP2 by deflection scanning, and the laser beam moves from the position L to the position L ′ by deflection scanning. Moving.

  When the optical axis of the laser beam is moved to the position L ′ by deflection scanning, it is displaced from the axis immediately above the hole. However, as shown in FIG. The beam reaches the bottom of the hole while being condensed due to multiple reflection at the side of the hole where the propagation has progressed. For this reason, even if the beam output in the process of blocking the latter half of the pulse oscillation is lower than that during processing, sufficient laser intensity density is ensured for processing, good hole processing is maintained, and the dimple hole shape is processed There is no particular problem. That is, the dimple hole is not elongated and better processing is performed.

  Even if the deflection scanning direction of the laser beam is opposite to that in FIG. 5, that is, when the beam moving direction is opposite to the rotation direction of the roll, the processed dimple opening is larger than the irradiation beam diameter and the side surface is Since the laser beam is inclined, the laser beam is condensed at the bottom of the hole by multiple reflection and contributes to the hole processing as in FIG. In this case, the dimple opening is slightly elongated as compared with the processing of FIG. 5 and does not adversely affect the subsequent metal steel strip.

  FIG. 4 is the timing chart described above. (A) is a driving current of a semiconductor laser, (b) is a relaxation oscillation pulse waveform of a YAG laser detected by a photodiode, (c) is an integrated value of (b) by an integrator, and (d) is an AO element It is a drive waveform. If the integrated value of the pulse energy for obtaining the target processing depth is Eo, and the detection level corresponding to the threshold value of the laser pulse having the laser intensity density contributing to the processing is S1, the integrated value in the integrator is Eo. At the point of time (relaxation oscillation pulse P1 portion), the AO element is driven. The duration τ3 of the drive signal for the AO element is set sufficiently long with respect to the difference (τ1−τ2) between the drive current duration τ1 of the semiconductor laser and the pulse width τ2 of the relaxation oscillation pulse used for processing.

  By the above mechanism, the pulse of the P1 portion at time τ2 (the first half portion of the YAG laser pulse oscillation) in the YAG laser pulse train of FIG. 4B is irradiated along the optical axis L to the surface of the rolling roll, and FIG. The pulse of P2 part (second part of the YAG laser pulse oscillation) of b) is deflected in the direction of the optical axis L ′, blocked by the beam damper 15, and irradiated to the roll surface to increase the dimple hole depth excessively. Absent.

  When the value of the integrator reaches Eo, the drive current of the pumping semiconductor laser is turned off, and the relaxation oscillation of the YAG laser itself is not stopped. The heat load on the YAG laser crystal is changed by changing the pumping intensity itself. To stabilize the YAG laser oscillation, stabilize the quality of the YAG laser beam, stabilize the condensing state of the YAG laser beam at the processing point, and make the processing shape uniform. It is. In the present invention, since the pulse width of the relaxation oscillation pulse is adjusted by an external mechanism, the excitation intensity to the YAG laser is averagely constant, the thermal load to the YAG laser is constant as the time average, and the oscillation of the YAG laser is performed. And beam quality can be stabilized.

  In the above example, the laser optical axis when the AO element is stopped is used as the L axis for processing, and the laser light when the AO element is driven is deflected to the L ′ axis and blocked by the beam damper. This is because efficient dimple hole processing is performed by using the head portion of the relaxation oscillation pulse having the highest output peak for processing. Since the time required to drive and stop the AO element is generally on the order of microseconds, it is assumed that the optical axis when the AO element is driven is the L axis, the laser optical axis when the AO element is stopped is the L ′ axis, and YAG In the configuration in which the latter half of the laser pulse oscillation is used for processing, the AO element is driven after detecting the start of relaxation oscillation, and the laser optical axis is deflected and scanned to the L axis used for processing. This is because the leading pulse cannot be guided to the roll surface.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, this invention is not limited to the example which concerns. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims, and of course, the technical scope of the present invention is also possible. It is understood that it belongs to.

  In the embodiment described above, the case where the semiconductor laser pumped YAG laser oscillator which is a semiconductor laser pumped solid state laser oscillator is used as the laser oscillator 1 has been described, but other laser oscillators may be used.

  In embodiment mentioned above, although the case where it processes on the surface of the rolling roll 30 which rolls a metal steel strip was demonstrated, another rolling roll may be used. Further, for example, microhole processing may be performed on the surface of another cylindrical metal body such as a thin plate continuous casting drum.

  The rolling roll for cold rolling was processed. The semiconductor laser excitation YAG laser 1 was oscillated with a pulse oscillation duration of about 40 μs by controlling the driving current of the pumping semiconductor laser of the laser oscillator 1 at 5 A at 0 A (zero ampere) and 45 A. The drive time of the drive current was 65 μs. The average energy of the relaxation oscillation pulse was 40 mJ, and when the pulse waveform detected by the photodiode was examined closely, the energy variation for each relaxation oscillation pulse was in the range of 35 mJ to 55 mJ.

  The above-described YAG laser oscillation is set to N = 1 in the equation (2) by the apparatus shown in FIG. 1 and the latter half of the pulse oscillation is cut off, thereby varying the energy between the laser pulses on the roll surface to be processed. Was 25 mJ ± 2 mJ.

  The above-described relaxation oscillation laser pulse with reduced processing energy variation according to the present invention was transmitted to the rolling roll by the apparatus having the configuration shown in FIG. 2, and focused on the surface of the rolling roll by the condenser lens to perform hole processing. A dimple hole with a diameter of 200 μm was formed on the entire surface of the rolling roll. When the dimple hole depth h was measured, the value of h was 50 to 60 μm, and the variation was 10 μm.

  When a metal steel strip was rolled 6000 tons using a rolling roll processed under the above conditions, the radius of the rolling roll was reduced by 40 μm due to wear, and a fatigue layer of 25 μm was formed on the surface of the rolling roll. After rolling, the rolling roll was ground with a radius of 25 μm, which was the same as the fatigue layer thickness, and the surface of the rolled roll after removing the fatigue layer was observed. The trace was completely removed together with the fatigue layer, and the roll surface became a uniform new surface.

  The present invention is particularly useful for a laser processing apparatus that performs micro-hole processing on the surface of a rolling roll of a metal steel strip using a laser oscillator such as a semiconductor laser excitation solid-state laser oscillator.

It is a partial block diagram which shows the structure of the laser oscillator periphery (laser oscillation side) of the processing apparatus of this invention. It is a partial block diagram which shows the structure in the laser irradiation side of the processing apparatus of this invention. It is an example of a relaxation oscillation pulse waveform (a, b) and its integrated waveform (c) of a semiconductor excitation solid-state laser. It is a timing chart which shows the processing method of the present invention. It is a schematic diagram of the processing part vicinity which shows the processing method of this invention. It is a schematic diagram which shows the laser beam behavior near the process part at the time of the beam deflection to an improper direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor laser excitation solid-state laser 2 Resonator rear mirror of semiconductor laser excitation solid-state laser 3 Laser light 4, 5, 21 Transmission mirror 6 Narrow band filter 7 ND filter 10 Photodiode (solid-state laser light detection element)
11 Amplifier circuit 12 Integrator 13 Deflection element drive circuit (AO element driver)
14 Deflection element (AO element; acousto-optic element)
DESCRIPTION OF SYMBOLS 15 Beam damper 16 Laser oscillator peripheral part 22 Condensing lens 23 Processing nozzle 30 Roll roll 31 Single axis | shaft stage (Single axis moving table)
40 Dimple hole opening 100 Laser processing equipment L, L 'Laser optical axis (position)
SP1, SP2 Laser focusing spot (irradiation position of laser beam)

Claims (5)

In the laser processing method of a rolling roll, forming a processing hole in the rolling roll by irradiating the surface of the rolling roll with a laser beam for rolling a metal steel strip,
N is a positive integer which is the number of times of rolling, δ is a reduction amount of roll radius caused by wear by rolling the metal steel strip by a specified amount by the rolling roll, and the rolling roll is rolled by the metal steel strip. A laser processing method for a rolling roll, characterized in that a processing hole having a processing depth h defined by the following formula (1) is formed, where ε is the thickness of the fatigue layer formed on the surface.
N × δ + (N−1) × ε <h <N × (δ + ε) (1)   2. The laser of the rolling roll according to claim 1, wherein a processing depth in forming the processed hole is controlled by controlling an irradiation time of the laser beam applied to the surface of the rolling roll. 3. Processing method.   When the laser beam oscillated by pulse excitation is used as the laser beam and the irradiation time of the laser beam irradiated onto the surface of the rolling roll is controlled, the relaxation oscillation pulse oscillated from the laser oscillator that outputs the laser beam is controlled. By integrating the waveform, it is determined that the pulse energy from the start of oscillation has reached a preset value, and the laser light irradiation time is controlled by blocking the latter half of the relaxation oscillation pulse that the laser light continues. A laser processing method for a rolling roll according to claim 2, wherein:   When controlling the irradiation time of the laser light applied to the surface of the rolling roll, the laser light is deflected so that the irradiation position of the laser light on the surface of the rolling roll changes in the circumferential direction of the roll. The laser processing method for a rolling roll according to claim 2 or 3, wherein the irradiation time of the laser beam is controlled by switching between a blocking state and a non-blocking state. A laser processing apparatus for a rolling roll, which forms a processing hole in the rolling roll by irradiating the surface of the rolling roll for rolling a metal steel strip with a laser beam,
A laser oscillator that outputs laser light; a deflection element that deflects the laser light that is output by relaxing oscillation of the laser oscillator by pulse excitation; a damper that blocks the laser light deflected by the deflection element; and the laser light A detector that detects the start of relaxation oscillation of the detector, an integrator that integrates the signal of the detector, and a control system that controls the deflection element based on a trigger signal from the integrator,
The deflection element is arranged such that when the laser beam is deflected, the irradiation position of the laser beam on the surface of the rolling roll is changed in the circumferential direction of the roll. Laser processing equipment.

Images