A method for ultrafast laser cutting assisted by chip combustion caused by heat accumulation

Abstract

This application relates to the field of ultrafast laser processing, and specifically discloses an ultrafast laser cutting method, including: determining laser cutting parameters according to the material to be cut, the laser cutting parameters including the equivalent number of spots and the pulse energy flux. The target material in the material to be cut can undergo a combustion reaction with the laser cutting gas atmosphere. The equivalent number of spots corresponds to the mass percentage of the target material in the material to be cut, and the multiple of the pulse energy flux relative to the saturation value of the incubation effect of the removal energy flux threshold of the material to be cut is; performing laser cutting on the material to be cut according to the laser cutting parameters. This application provides a solution for high-carbon-containing materials, and by utilizing the thermal accumulation effect, strong light absorption effect, and the characteristics that carbon chips can burn and the products are gaseous and easy to discharge, it cleverly converts the unfavorable factors in the traditional ultrafast laser cutting technology into favorable factors, realizing narrow-slit high-efficiency cutting and narrow-slit processing with a large depth-to-width ratio.

Description

Technical Field

[0001] This application relates to the technical field of ultrafast laser processing, and particularly to a method for assisting ultrafast laser cutting by chip combustion caused by heat accumulation. Background Art

[0002] Composite materials are widely used in fields such as aerospace due to their excellent mechanical, thermal, and chemical properties, and are beginning to be more and more widely used in civil and military fields such as high-end automobiles, rail transit, and weapons. Especially among them, carbon-containing composite materials have developed multiple series and multi-purpose composite materials represented by carbon-resin, carbon-ceramic, and carbon-carbon. The heterogeneous tissue characteristics, mesoscopic scale anisotropy of composite materials, and the significantly different mechanical, thermal, electrical, and optical properties of the matrix phase and the reinforcing (toughening) phase of most materials make them difficult-to-machine materials, facing prominent problems such as processing damage, processing accuracy, and processing efficiency. The emerging ultrafast laser processing technology in recent years is expected to become a breakthrough to solve the processing bottleneck of traditional methods. However, limited by the average power of the ultrafast laser source, improving its processing efficiency and the processing ability of thick-walled structures is one of the core issues concerned in related research and applications.

[0003] Cutting processing is one of the most important and extensive applications of ultrafast laser manufacturing technology. The application objects of ultrafast laser cutting mainly target related homogeneous materials such as semiconductors, metals, and insulators. An important consideration in the processing process is how to exclude the chips in the cut as much as possible to prevent the reduction of cutting subtraction efficiency or even the inability to cut through caused by difficult chip discharge. For this reason, for the case where the thickness of the material to be cut is greater than the spot size to a certain extent, the cut is generally widened by trajectory filling to assist chip discharge. Trajectory filling means an increase in the total cutting distance and total time compared to the non-filling mode, especially for materials with a larger thickness, and the increase is very obvious. High-carbon materials have their unique physical and chemical properties. How to break through the existing chip removal ideas for high-carbon materials and achieve effective chip discharge with less or no filling, and ensure a rapid increase in cutting depth, that is, improve the cutting efficiency and the ability to cut through thickness, is a technical problem that needs to be solved. Summary of the Invention

[0004] This application provides a method for assisting ultrafast laser cutting by chip combustion caused by heat accumulation. For high-carbon materials, by using the heat accumulation effect, strong light absorption effect, and the characteristics that the chips can burn and the combustion products are easily discharged gases, the adverse factors in the traditional ultrafast laser cutting technology are cleverly transformed into favorable factors to achieve high-efficiency cutting of narrow slots and processing of narrow slots with a large depth-to-width ratio.

[0005] In the first aspect, a laser cutting method is provided, including:

[0006] Determine laser cutting parameters according to the material to be cut. The laser cutting parameters include the equivalent spot number N and the pulse energy flux F. The target material in the material to be cut can undergo a combustion reaction with the laser cutting gas atmosphere. The equivalent spot number N corresponds to the mass percentage of the target material in the material to be cut, and the pulse energy flux F is a multiple of the saturation value F of the incubation effect with respect to the removal energy flux threshold of the material to be cut. th is F r ;

[0007] Perform laser cutting on the material to be cut according to the laser cutting parameters.

[0008] Compared with the prior art, the solution provided by this application at least includes the following beneficial technical effects:

[0009] (1) A method for assisting ultrafast laser cutting by using thermal accumulation-induced chip combustion provided by the present invention utilizes the controllable thermal accumulation effect when ultrashort pulse laser interacts with materials, the strong light absorption effect of high-carbon (taking carbon as an example) debris to be discharged in deep and narrow slits, and the characteristics that the high-carbon debris to be discharged can be oxidized and becomes gaseous after oxidation. Through the controllable thermal accumulation effect, it assists the carbon chips to burn controllably in the oxidizing gas. It not only realizes the discharge of difficult-to-discharge carbon chips in the form of carbon dioxide and carbon monoxide, but also realizes the controllable heat release during the controllable oxidation (combustion) of carbon chips. Furthermore, it solves the difficulties such as cutting depth saturation, reduced material removal efficiency, and inability to cut through thick-walled structures caused by difficult chip removal in deep and narrow slits, and also utilizes the controllable heat release generated by controllable combustion to accelerate the material removal. Therefore, compared with the ordinary methods of traditional ultrafast laser processing materials, it cleverly utilizes the unique physical and chemical effects of high-carbon materials and external auxiliary factors to transform adverse factors into favorable factors, and is a method that can achieve the processing of narrow slits with a large depth-width ratio for high-carbon materials.

[0010] (2) A method for assisting ultrafast laser cutting by using thermal accumulation-induced controllable chip combustion provided by the present invention utilizes the interaction mechanism between ultrashort pulse laser and high-carbon materials. By controlling the value range of the pulse energy flux relative to the material removal threshold, it not only realizes the guarantee of the combustibility of carbon chips in the slit (corresponding to the lower limit of the value range), but also avoids the prominent thermal damage caused by excessive energy density (corresponding to the upper limit of the value range). Therefore, it realizes the balance among the combustibility of carbon chips, the material removal efficiency of the laser itself, and the thermal damage of the formed interface after material removal; by using the precise controllability of the ultrafast laser thermal accumulation effect, it can achieve the controllable auxiliary processing effect of "stopping the local combustion when the light stops". Therefore, it is an efficient, precise, and reliable cutting method for high-carbon materials.

[0011] (3) Meanwhile, the device relied on by the present invention is highly compatible with existing industrialized ultrafast laser processing equipment, and the dust suction and exhaust device and the air blowing device can be continued to be used without incurring additional hardware costs. Therefore, the present invention is a method with good economy, simple method steps, and easy to implement.

[0012] In combination with the first aspect, in some implementation manners of the first aspect, the method further includes:

[0013] When the thickness of the material to be cut is greater than or equal to a first preset thickness, a combustion-supporting gas is applied to the cutting area during the laser cutting process.

[0014] A method for using heat accumulation to achieve controllable chip combustion-assisted ultrafast laser cutting provided by the present invention utilizes the entrapment effect of deep and narrow gaps on processing debris and the suppression of the escape of combustion-supporting gas, determines whether to apply combustion-supporting gas according to the preset processing depth, and avoids waste caused by the ineffectiveness of using combustion-supporting gas in gaps with poor depth and narrowness; utilizes the characteristics that carbon debris is highly flammable at high temperatures and has low requirements for oxygen content, and only applies combustion-supporting gas when necessary (such as in deep gaps), and it is not necessary to use high-concentration oxygen but a gas with an oxygen content as low as the oxygen content in the air (i.e., air) is also acceptable.

[0015] In combination with the first aspect, in some implementation manners of the first aspect, the combustion-supporting gas is a nitrogen-oxygen mixed gas with an oxygen concentration ≥ 21% and industrial pure oxygen.

[0016] In combination with the first aspect, in some implementation manners of the first aspect, the laser cutting on the material to be cut includes:

[0017] When the thickness of the material to be cut is greater than or equal to a second preset thickness, reciprocating cutting is performed on the material to be cut along a plurality of filling trajectories in sequence. The plurality of filling trajectories are parallel to each other, the distance between adjacent two filling trajectories is the filling pitch, the total width of the plurality of filling trajectories is the filling width, and the filling width corresponds to the thickness of the material to be cut.

[0018] Only for processing with a relatively large thickness and a great concern for cutting efficiency, it is necessary to appropriately horizontally offset the preset filling pitch and a small number of filling trajectory numbers in a direction perpendicular to the processing depth. It should be noted that the selection of the filling width should correspond to the thickness of the material to be cut. An overly wide filling width may lead to the escape effect of the combustion-supporting gas, causing the combustion-supporting gas to not stay in the laser cutting area. Therefore, generally, the filling width should not be too large according to specific requirements.

[0019] In combination with the first aspect, in some implementation manners of the first aspect, the laser cutting on the material to be cut includes:

[0020] When the thickness of the material to be cut is greater than or equal to the third preset thickness, the beam feed amount is applied when the machining depth reaches the preset depth according to the beam depth of focus and the thickness of the material to be cut.

[0021] In combination with the first aspect, in some implementation manners of the first aspect, the target material is a carbon-containing material, and the carbon therein is non-diamond elemental carbon, and the mass percentage of carbon in the material to be cut is ≥ 55%.

[0022] In combination with the first aspect, in some implementation manners of the first aspect, the material to be cut is graphite, carbon fiber, graphene fiber, carbon-resin composite material, carbon-ceramic composite material, carbon-carbon composite material, carbon-metal composite material, carbon-ceramic-polymer composite material; the forms of carbon existing in the material to be cut include at least one of the following: continuous carbon fiber, short carbon fiber, carbon powder.

[0023] In combination with the first aspect, in some implementation manners of the first aspect, the equivalent number of spots N ∈ [50, 10000].

[0024] In combination with the first aspect, in some implementation manners of the first aspect, the equivalent number of spots N ∈ [50, 150].

[0025] When the mass percentage of the target material in the material to be cut is relatively large, the value range of the equivalent number of spots N can be relatively large. For example, the maximum value of the equivalent number of spots N can be relatively large. When the mass percentage of the target material in the material to be cut is relatively small, the value range of the equivalent number of spots N can be relatively small. For example, the maximum value of the equivalent number of spots N can be relatively small.

[0026] In combination with the first aspect, in some implementation manners of the first aspect, the multiple F r ∈ [5, 60].

[0027] By controlling the equivalent number of spots at the unit spot position on a single spot trajectory within the range of 50 - 150, the nearly linear segment of the "removal depth - number of pulses" curve is utilized and the saturation segment is avoided, maximizing the efficiency of laser energy utilization.

[0028] In combination with the first aspect, in some implementation manners of the first aspect, the single pulse duration of the pulsed laser used in the laser cutting method is ≤ 50 ps, and the pulse repetition frequency is ≥ 0.1 MHz.

[0029] The relatively short single pulse duration is beneficial to reducing heat dissipation, enabling the cutting heat to be concentrated near the cutting area, which is beneficial to increasing the combustion rate of the material to be cut and enabling the material to be cut to burn fully to obtain a relatively fast cutting efficiency.

[0030] In a second aspect, a laser cutting device is provided for performing the method described in any of the implementation manners in the first aspect above. Description of the Drawings

[0031] Figure 1 FIG. is a schematic flow chart of a laser cutting method provided by an embodiment of the present application. Detailed Embodiments

[0032] The present application will be further described in detail below with reference to the drawings and specific embodiments.

[0033] The main objects of traditional ultrafast laser cutting are homogeneous materials such as semiconductors, metals, insulators, etc., and metal matrix composites. An important consideration in the processing process is how to exclude the chips in the cut as much as possible. The traditional method is to use a filling trajectory to expand the slit width to facilitate chip removal (sometimes supplemented by blowing air to remove chips) and optical energy deposition, so as to increase the cutting depth while maintaining a certain cutting efficiency. However, the filling method of expanding the slit width directly causes a sharp increase in the path of the processing beam trajectory (for example, each filling causes the total path of the trajectory to almost double). Although for cutting some materials with a larger thickness, the increase in the depth removal rate caused by the filling trajectory can offset or even overcompensate (so that the effective cutting efficiency does not decrease or even increases instead) the potential effective cutting efficiency reduced by the significant increase in the filling trajectory, for small-width, large-depth cutting with little or no filling, especially narrow-slit large-depth cutting without sacrificing the cutting efficiency, it is still the goal pursued by researchers.

[0034] Different from traditional homogeneous materials and metal matrix composites, composites represented by carbon-resin, carbon-ceramic, carbon-carbon, etc., due to their special material physical and chemical properties, provide the possibility to break through the above traditional processing ideas. Studying how to use the characteristics of related high-carbon materials to achieve narrow-slit large-depth cutting or narrow-slit high-efficiency cutting with little or no filling has innovative value and practical value.

[0035] Figure 1 is a schematic flow chart of a laser cutting method provided by an embodiment of the present application.

[0036] 110. According to the material to be cut, determine the laser cutting parameters. The laser cutting parameters include the equivalent spot number N and the pulse energy flux F. The target material in the material to be cut can have a combustion reaction with the laser cutting gas atmosphere. The equivalent spot number N corresponds to the mass percentage of the target material in the material to be cut, and the multiple of the pulse energy flux F relative to the saturation value F of the incubation effect of the removal energy flux threshold of the material to be cut is F th of F r .

[0037] Since the material to be cut contains a target material that can undergo a combustion reaction with the laser cutting gas atmosphere, the laser cutting parameters can be determined based on the properties of the target material and its mass percentage in the material to be cut.

[0038] In some embodiments provided by the present application, the target material can be a carbon-containing material, and the carbon therein is non-diamond elemental carbon, and the mass percentage of carbon in the material to be cut is ≥ 55%. That is to say, the target material can be the material with the highest content in the material to be cut. The material to be cut is, for example, graphite, carbon fiber, graphene fiber, carbon-resin matrix composite, carbon-ceramic composite, carbon-carbon matrix composite, carbon-metal matrix composite, carbon-ceramic-polymer composite; the forms of carbon in the material to be cut include at least one of the following: continuous carbon fiber, short carbon fiber, carbon powder.

[0039] Using the beam in-situ percussion drilling method or the single-pass scribing method, make the total equivalent irradiation pulse number N of the structure to be processed on the material within any value in the interval of [50, 10000] at the spot scale, and determine the material removal energy flux threshold F at this pulse number th , and take it as the saturation value of the removal threshold F th .

[0040] Specifically, the equivalent number of spots at the unit spot position on a single spot trajectory can be estimated by N = 2ω×f / v, and according to the incubation effect of the material processing threshold, only making N ∈ [50, 150] can approximately represent the processing threshold when N ∈ [50, 10000], where v is the scanning speed of the beam relative to the surface of the workpiece material, f is the pulse repetition frequency, and ω is the spot radius. The material processing threshold F th can be accurately determined by methods such as the area extrapolation method and the depth extrapolation method of the common in-situ dotting or scribing methods (especially for Gaussian-distributed laser beams), or can be roughly determined by the trial method. For example, keep the focused spot with a radius of ω at a certain fixed scanning speed v and a fixed pulse repetition frequency f, change the pulse energy E or the average power P, and carry out scribing processing. If a certain P 1 power (corresponding to the pulse energy E 1 ) cannot process a groove visible under high magnification microscopy, but a power P 1 slightly larger than P 2 (corresponding to the pulse energy E 2 ) can just process a groove visible under high magnification microscopy, then the processing power threshold can be roughly taken as P th = (P 1 + P 2 ) / 2. From the pulse energy E th corresponding to the power threshold P th , combined with the spot energy distribution characteristics and the spot radius ω, it can be obtained that for a Gaussian-distributed spot, there is Fth =2×P th / (π×ω 2 ×f)(where ω is "1 / e 2 "The spot radius defined under the definition); for other distributions of spots, such as cylindrical flat-top spots, there is F th =P th / (π×ω 2 ×f).

[0041] In some embodiments, when the target material accounts for a relatively large mass percentage of the material to be cut, the value range of the equivalent spot number N can be relatively large. For example, the maximum value of the equivalent spot number N can be relatively large. When the target material accounts for a relatively small mass percentage of the material to be cut, the value range of the equivalent spot number N can be relatively small. For example, the maximum value of the equivalent spot number N can be relatively small.

[0042] The material removal threshold F through step 1 th , the pulse energy flux to be applied can be obtained as F = F r ×F th , where F r ∈[5,60]. In some embodiments, in order to allow the target material to undergo a complete combustion reaction, F r The value of should not be too low.

[0043] At the same time, referring to the preset processing depth, the equivalent number of spots N and F at the unit spot position on the single spot trajectory to be applied can be determined. r The value range of N or F is as follows: the larger the preset processing depth, the more N or F is required. r The larger the value, the more N∈[50,150] and F r ∈[5,60]. According to the specific properties of the material, laser characteristics (such as wavelength, pulse width, etc.), the average removal depth of each equivalent pulse can be estimated: generally, for ultrafast laser processing of high-carbon materials in the near-infrared and near-ultraviolet bands, this value is on the order of 0.1 to 1μm. The average removal depth of each equivalent pulse can also be more accurately measured by the "removal depth-pulse number" curve, which is nearly linear before the number of pulses does not exceed [50,150]; or it can be determined with the help of other theoretical or experimental tools.

[0044] 120 , performing laser cutting on the material to be cut according to the laser cutting parameters.

[0045] Specifically, the processing dust suction and exhaust device is turned on, and the laser cutting parameters in step 110 are used to reciprocate and cut a predetermined number of times along the material depth direction at the initial single track.

[0046] In some embodiments, the duration of a single pulse of the pulsed laser used in the laser cutting method is ≤50 ps, and the pulse repetition frequency is ≥0.1 MHz. The relatively short duration of a single pulse is conducive to reducing heat dissipation, enabling the cutting heat to be concentrated near the cutting area, which is beneficial to increasing the combustion rate of the material to be cut, allowing the material to be cut to burn sufficiently to obtain a relatively high cutting efficiency.

[0047] If the depth has not reached the preset cutting depth, then horizontally offset the preset filling pitch and the number of filling tracks in the corresponding direction perpendicular to the machining depth, and sequentially repeat the machining at the initial single track at each track until the machining of the last filling track is completed. If the object to be cut is relatively thin, such that the preset cutting depth can be reached after reciprocating engraving a relatively small number of times along the material depth direction at a single track, then filling is not required.

[0048] The part that needs to be retained can be obtained through laser cutting as the body of the preset processing structure. It should be noted that the part with the opposite track filling direction is the retained part and serves as the body of the preset processing structure. Specifically, generally, the part opposite to the horizontal filling direction is taken as the retained part and serves as the body of the preset processing structure. Alternatively, the part with the same horizontal filling direction can be taken as the retained part and serves as the body of the preset processing structure. In this case, the dimensions of the preset structure need to be appropriately converted with reference to the filling width (mainly determined by the filling pitch and the number of filling tracks). Here, the part opposite to the horizontal filling direction is taken as the retained part.

[0049] For example, if the hollow structure obtained after laser cutting a hole is the part that needs to be retained, then the track filling direction is towards the axis of the hole; if the part separated from the cutting hole after laser cutting the raw material is the part that needs to be retained, then the track filling direction is away from the axis of the cutting hole.

[0050] In some embodiments, when the thickness of the material to be cut is greater than or equal to the first preset thickness, a combustion-supporting gas is applied to the cutting area during the laser cutting process. That is to say, when the thickness of the material to be cut is relatively large, a combustion-supporting gas can be applied during the laser cutting process. The combustion-supporting gas is, for example, a nitrogen-oxygen mixed gas with an oxygen concentration ≥21% and industrial pure oxygen.

[0051] Since this method utilizes heat accumulation-induced controllable chip combustion-assisted ultrafast laser, it not only realizes the discharge of difficult-to-discharge carbon chips in the form of carbon dioxide and carbon monoxide, but also realizes the controllable heat release during the oxidation of carbon chips. Therefore, high-carbon materials can be processed with narrow slots having a large depth-to-width ratio. That is, only for processing with a relatively large thickness and a great concern for cutting efficiency, it is necessary to appropriately horizontally offset the preset filling pitch and a small number of filling track numbers along the corresponding direction perpendicular to the processing depth. It should be noted that the selection of the filling width should correspond to the thickness of the material to be cut. An overly wide filling width may lead to the escape effect of the combustion-supporting gas, causing the combustion-supporting gas to not stay in the laser cutting area. Therefore, according to specific requirements, the filling width is generally not too large.

[0052] In some embodiments, when the thickness of the material to be cut is relatively large, it is necessary to apply a beam feed amount when the processing depth reaches a preset depth according to the beam's half focal depth and the thickness of the material to be cut. Specifically, according to the relative magnitudes of the removed depth and the focal depth of the processing beam, it is determined whether to apply a beam feed amount along the processing depth direction, and the above laser cutting process is repeated at the initial track until the cutting reaches the preset depth.

[0053] Since this method utilizes heat accumulation-induced controllable chip combustion-assisted ultrafast laser processing, it is easy to achieve efficient processing of narrow slots with a large depth-to-width ratio. Therefore, according to the light parameters such as the wavelength and spot size of the light source used, only when the cutting depth far exceeds the spot diameter by dozens of times (the specific value depends on the light source parameters) or reaches the order of the beam's focal depth (the specific value depends on the light source parameters), it is necessary to apply a beam feed amount along the processing depth direction. However, it is beneficial to apply a feed whenever the cutting depth reaches the order of the beam's half focal depth (to ensure that the focused spot remains on the cross-section to be removed).

[0054] The embodiments of the present application also provide a laser cutting device for performing the method as Figure 1 shown.

[0055] The present application will be further described in detail in conjunction with the following content.

[0056] Example 1: Cutting of Carbon Fiber Reinforced Epoxy Composite

[0057] The processing target is to process through-hole by reciprocating milling-through cutting (i.e., non-filling cutting) at a single track on a certain brand of high-modulus carbon fiber reinforced resin matrix composite with a thickness ranging from 400μm to 2mm (the carbon content of the material > 55%). The processing method is galvanometer scanning processing. The pulse width of the laser source used is 10ps, the central wavelength is 532nm, and the beam waist diameter of the processing beam 2ω = 30μm.

[0058] First, determine the multi-pulse removal threshold of the material. Set the laser scanning speed v = 0.05m / s across the material surface. At this time, at a pulse repetition frequency of f = 0.2MHz, the equivalent pulse number of a single scan is roughly N = 2ω×f / v = 120. Only scan once. Using the energy trial method, with the help of the 1000-fold microscopic effect of scanning micro scratches, the threshold F of the material removal energy flux can be determined. th (N) about 0.70J / cm 2 .

[0059] Secondly, determine the equivalent number of spots N at the unit spot position on a single spot trajectory, the pulse energy flux F relative to the threshold F th Multiples of F r 、Whether to apply combustion-supporting gas to the cutting area. Set the speed of the laser scanning the material surface v = 0.1m / s, at this time, the equivalent number of spots at the unit spot position on a single spot track N = 2ω×f / v = 60. Under the conditions of average power P = 27W and pulse repetition frequency f = 0.2MHz, it is easy to get the spot center flux of each pulse F = 2×P / (π×ω 2 ×f)=38.2J / cm 2 , which is relative to F th =0.70J / cm 2 About F r =55 times, satisfying F r ∈[5,60]. According to subsequent experiments, if the thickness of the processed material is 400μm, it is not necessary to apply combustion-supporting gas to the cutting area, because the gap depth of ≤400μm during the cutting process has almost no effect on suppressing the escape of combustion-supporting gas, but it is effective for thicker materials.

[0060] Again, turn on the processing dust suction and exhaust device, and use the processing parameters in the previous step to reciprocate and remove a predetermined number of times along the material depth direction at the initial single track. For materials with a thickness of up to 2 mm, fill them horizontally along the direction perpendicular to the processing depth at the same time. The number of filling tracks is 1, 2, and 3, and the filling width between adjacent tracks is set to 20μm.

[0061] Finally, process according to the parameters of the previous step and take The part outside the cutting track (i.e., the part opposite to the horizontal filling direction in the previous step) is the processing target structure. Considering that the focal depth of the beam (i.e., 2 times the Rayleigh length) is about 3mm, which is similar to the 2mm thickness structure in the material thickness range of 400μm-2mm, for the 2mm thickness structure, a beam feed of 0.5mm is applied in the processing depth direction for every 0.5mm depth of processing. The following table 1 shows the beam feed along the Track circle reciprocating etching can just cut through The average number of turns required for the holes. Note that since the scanning speed, average power, and pulse repetition frequency used are all the same, the effective cutting efficiency can be directly judged by the magnitude of the number of turns used.

[0062] Table 1 Machining Efficiency Results

[0063]

[0064] It can be seen that applying auxiliary gas has little improvement effect on the 400-μm thin-wall structure. However, for the 2-mm thick structure, not applying auxiliary gas directly leads to the inability to cut through with the non-fill method. Applying auxiliary gas has obvious improvement: the more oxygen content in the auxiliary gas, the more conducive it is to improving the effective cutting efficiency.

[0065] As another comparison, compared with the results in Table 1 for the 400-μm thick structure without auxiliary gas with v = 0.1 m / s, average power P = 27 W, and pulse repetition frequency f = 0.2 MHz (meeting the equivalent number of spots N ∈ [50, 150] at the unit spot position on a single spot trajectory), if the scanning speed v = 5 m / s is adjusted so that the equivalent number of spots N = 1.2 at the unit spot position on a single spot trajectory, that is then it takes about 2000 turns, that is, 6.3 s to cut through. Compared with the 3.1 s required for 10 turns in Table 1, the effective cutting efficiency is 50% lower. In addition, for the 2-mm wall thickness in Table 1, if appropriate filling is used (for example, the number of filling trajectories is 1, 2, 3 and the filling width between adjacent trajectories is set to 20 μm), there is also the potential to improve the efficiency: it is estimated that the effective cutting efficiency can be increased by more than 50% - 200%. However, when the number of filling trajectories is too large, the effective cutting efficiency decreases again.

[0066] In summary, according to the thickness of the structure to be machined, auxiliary gas can be applied targeted, the oxygen content of the auxiliary gas can be controlled, and an appropriate filling width can be applied, so that the effective cutting efficiency can be significantly improved compared with the traditional ordinary machining method. Especially for thick-wall structures, the problem that the traditional method cannot cut through without filling can be directly solved. A method for auxiliary ultrafast laser cutting using heat accumulation to cause controllable chip combustion provided by the present invention can achieve the processing of narrow slots with large depth-width ratio for high-carbon materials, and is an efficient, precise, and reliable cutting method for high-carbon materials. At the same time, it is highly compatible with existing industrial ultrafast laser processing equipment (the device can be continued to be used), without increasing additional hardware costs, and is a method with good economy, simple method steps, and easy to implement.

[0067] Although the present invention is disclosed above in preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims of the present invention.

Claims

1. A laser cutting method, characterized in that, it includes: According to the material to be cut, the laser cutting parameters are determined, and the laser cutting parameters include an equivalent spot number N and a pulse energy flux F. The target material in the material to be cut can react with the laser cutting gas atmosphere to burn; the equivalent spot number N corresponds to the mass percentage of the target material in the material to be cut, and the equivalent spot number N satisfies: N = 2ω × f / v, and N∈[50,10000]; the pulse energy flux F is relative to the saturation value F of the energy flux threshold hatching effect of the material to be cut. th The multiple of F r ; Material processing threshold F th Determined by the area extension method and depth extension method using in-situ dotting or scribing, F = 2 × P / (π × ω 2 ×f), where ω is the spot radius, f is the pulse repetition frequency, v is the scanning speed of the beam relative to the workpiece material surface, P th is the power threshold, multiple F r ∈[5,60]; Performing laser cutting on the material to be cut according to the laser cutting parameters.

2. The laser cutting method according to claim 1, characterized in that, the method further includes: When the thickness of the material to be cut is greater than or equal to a first preset thickness, applying a combustion-supporting gas to the cutting area during the laser cutting process.

3. The laser cutting method according to claim 2, characterized in that, the combustion-supporting gas is a nitrogen-oxygen mixed gas with an oxygen concentration ≥ 21% and industrial pure oxygen.

4. The laser cutting method according to claim 1, characterized in that, performing laser cutting on the material to be cut includes: When the thickness of the material to be cut is greater than or equal to a second preset thickness, performing reciprocating cutting on the material to be cut along a plurality of filling trajectories in sequence. The plurality of filling trajectories are parallel to each other, the spacing between adjacent two filling trajectories is the filling spacing, the total width of the plurality of filling trajectories is the filling width, and the filling width corresponds to the thickness of the material to be cut.

5. The laser cutting method according to claim 1, characterized in that, performing laser cutting on the material to be cut includes: When the thickness of the material to be cut is greater than or equal to a third preset thickness, applying a beam feed amount when the processing depth reaches a preset depth according to the beam semi-focal depth and the thickness of the material to be cut.

6. The laser cutting method according to claim 1, characterized in that, the target material is a carbon-containing material, and the carbon therein is non-diamond elemental carbon, and the mass percentage of carbon in the material to be cut ≥ 55%.

7. The laser cutting method according to claim 6, characterized in that, the material to be cut is graphite, carbon fiber, graphene fiber, carbon-resin composite material, carbon-ceramic composite material, carbon-carbon composite material, carbon-metal composite material, carbon-ceramic-polymer composite material; the forms of carbon existing in the material to be cut include at least one of the following: continuous carbon fiber, short carbon fiber, carbon powder.

8. The laser cutting method according to claim 1, characterized in that, the equivalent number of spots N ∈ [50, 150].

9. The laser cutting method according to claim 1, characterized in that, the single pulse duration of the pulsed laser used in the laser cutting method ≤ 50 ps, and the pulse repetition frequency ≥ 0.1 MHz.

10. A laser cutting device, characterized in that, it is used to execute the method according to any one of claims 1 to 9.

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