Band tool induction preheating-laser selective strengthening process method

Abstract

The application provides a strip-shaped cutter induction preheating-laser selective strengthening process method, which comprises the following steps: determining the array arrangement form of a strengthening unit according to a strengthening target parameter of a cutter to be processed; obtaining a circular flat-top double-beam by using a light spot homogenization shaping system; arranging an induction heating coil before and after the circular flat-top double-beam, and using the induction heating coil to preheat a hardening unit before laser selective quenching; performing laser selective strengthening, and ensuring that the laser strengthening unit always remains in an austenite phase region during laser irradiation; and finally performing post-heating type low-temperature tempering. The process method can obtain a depth of 2.2-3.1 mm of a selective hardening layer, and the hardness value of the hardened area reaches 740HV-860HV. The heterogeneous structure formed by laser selective strengthening treatment, which is a soft phase-hard phase composite, can solve the problems of easy cracking and surface peeling under the condition of full-area laser strengthening treatment, and significantly improve the wear resistance and service life of the cutter.

Description

Technical Field

[0001] This invention belongs to the field of tool surface strengthening, specifically relating to a strip tool induction preheating-laser selective strengthening process. Background Technology

[0002] Cutting tools are essential tools in production and daily life. Their use is crucial for reducing labor intensity and improving the quality of industrial products. The quality of cutting tools directly affects the production efficiency and product quality of related manufacturing processes, impacting all aspects of the production chain. Currently, strip cutting tools typically require surface strengthening treatment to improve their cutting performance and extend their service life.

[0003] Currently, surface strengthening of strip cutting tools mainly relies on induction hardening. The quality of induction hardening is greatly affected by changes in the distance between the tool and the induction coil. The relative movement between the tool and the induction coil inevitably causes variations in this distance, resulting in an uneven hardened layer on the strip cutting tool. Furthermore, induction hardening suffers from the drawback of high temperature at the tool's center and low temperature at the edges, failing to achieve a balance between cutting edge hardness and overall tool strength and toughness. Insufficient hardening leads to low cutting edge hardness and poor wear resistance, while over-hardening results in excessively high overall tool hardness, making it prone to fracture. These two drawbacks of induction hardening severely impact the cutting performance and service life of strip cutting tools. Therefore, researchers have proposed using laser hardening to achieve surface strengthening of these tools. For example, patent application number ZL202010149426.9 proposes a laser hardening process for thin-bladed cutting edges, using a continuous laser to form a laser-hardened layer with a thickness of 0.05–0.3 mm at the cutting edge. Patent application number ZL201810330408.3 proposes a cutting edge treatment method, which uses laser hardening to strengthen high-carbon tool steel cutting edges, causing a hardened layer with a depth of 0.2–1 mm to form on the cutting edge surface. However, the hardened layer depth obtained by the above patents is relatively shallow, and the two side cutting surfaces of the tool are not hardened. Furthermore, full-area laser hardening generally suffers from a large difference in hardness between the martensitic layer and the material substrate, leading to problems such as easy cracking and peeling of the tool surface.

[0004] Therefore, a surface strengthening method for strip tools with a soft-hard phase composite, a deep treatment layer, and an adjustable laser-strengthened area has not yet been reported, and it is also a key technology for improving the performance and service life of strip tools. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for induction preheating and selective laser strengthening of strip-shaped cutting tools. This method utilizes an induction coil to preheat the cutting tool strip, followed by simultaneous selective scanning of both sides of the strip-shaped tool using a circular homogenized dual-beam laser. This results in a selectively hardened layer with a depth of 2.2–3.1 mm and a hardness of 740 HV–860 HV in the hardened area. The heterogeneous soft-hard phase composite structure formed through selective laser strengthening solves problems such as easy cracking and surface peeling that occur under full-area laser strengthening conditions, and significantly improves the wear resistance and service life of the cutting tool.

[0006] The technical solution of the present invention is as follows:

[0007] A method for induction preheating and laser selective enhancement of a strip-shaped cutting tool includes the following steps:

[0008] (1) Determine the array arrangement of the strengthening units according to the strengthening target parameters of the tool to be processed. That is, first select the position and size of the laser strengthening area on the workpiece surface, and then design the laser strengthening unit array within the selected area, including designing the shape, arrangement and size of the laser selective strengthening units.

[0009] (2) Using a beam homogenization and shaping system, combined with a beam splitter and a mirror, a circular flat-top double beam is obtained, with the diameter of the circular homogenized beam ranging from 0.5 to 1.8 mm.

[0010] (3) Perform induction preheating. Induction heating coils are set in front of and behind the circular flat-top double beam to perform induction preheating on the hardening unit before laser selective quenching. The induction preheating temperature is 450-700℃.

[0011] (4) Perform selective laser strengthening. Use a circular flat-top double beam to perform synchronous selective laser scanning quenching on the two sides of the strip tool. Use a dual-color pyrometer to perform closed-loop temperature control on the selective laser strengthening unit to ensure that the laser strengthening unit remains in the austenitic phase region during laser irradiation.

[0012] (5) Perform post-heating low-temperature tempering. Use the induction heating coil set in step (3) and the bicolor pyrometer to perform temperature closed-loop controllable low-temperature tempering. The low-temperature tempering temperature is 170-240℃.

[0013] Furthermore, in step (1), the shape of the laser selective enhancement unit is elongated or circular; the arrangement includes dot matrix, stripe, or dot matrix and stripe superposition.

[0014] Furthermore, in step (2), when the laser selective enhancement unit is circular, the circular homogenizing spot is required to completely cover a single laser selective enhancement unit; when the laser scanning enhancement unit is elongated, the circular homogenizing spot is required to cover the laser selective enhancement unit through continuous displacement along the width direction.

[0015] Furthermore, in step (4), when the laser selective reinforcement unit is circular, a pulsed dual-beam irradiation heating method is adopted. That is, if the paraxial pyrometer detects that the temperature of the laser irradiation area continues to rise to the preset upper temperature limit, i.e., 1000-1050℃, the laser is turned off to cool the laser irradiation unit. When the temperature of the laser irradiation unit drops to the preset lower temperature limit, i.e., 800-830℃, the laser irradiation heating is started. Through pulsed laser energy injection, it is ensured that the circular reinforcement unit always remains in the austenitic phase region during the laser irradiation process. The number of pulsed laser irradiations is 3-20 times. When the laser selective reinforcement unit is elongated, a scanning dual-beam irradiation heating method is adopted. That is, based on the temperature closed-loop control system of the laser irradiation area, the heating temperature of the laser irradiation area is controlled at 800-1050℃ by controlling the laser power.

[0016] Furthermore, the distance error between the strip cutter and the induction coil at each position is controlled within ±0.05mm.

[0017] Furthermore, the interval between adjacent laser selective enhancement units is greater than 3mm.

[0018] Furthermore, in step (4), the scanning path of the flat-top laser beam gradually moves from the blade edge to the back of the blade.

[0019] Furthermore, induction preheating, laser selective enhancement, and post-heating cryogenic tempering are carried out in an argon atmosphere.

[0020] The present invention has the following beneficial effects:

[0021] (1) Advantages of selective laser hardening: This invention proposes a selective laser hardening process for cutting tools, which involves selectively strengthening certain areas of the tool under machining using laser technology. Different strengthening zones, laser scanning densities, and scanning speeds are planned based on the different mechanical properties required for the cutting edge and back of the tool, thereby achieving a reasonable distribution of hardness between the cutting edge and back of the tool. This significantly improves the overall performance of the strip tool. Furthermore, this process improves the strength and toughness of the tool by constructing a heterogeneous structure, solving the problem of easy cracking and peeling of the full-area hardened layer.

[0022] (2) Advantages of induction-assisted heating: This invention proposes a tool induction-assisted heating process, which uses an induction coil to perform induction preheating and induction postheating on the strip tool to be processed. On the one hand, the preheating increases the starting temperature of laser quenching, thereby enabling the laser energy to be transferred to a deeper layer of the material, achieving a hardened layer with a depth of 2.2 to 3.1 mm. On the other hand, the induction postheating process performs low-temperature tempering on the laser selective strengthening area of ​​the tool, reducing brittleness.

[0023] (3) Precise and controllable microstructure evolution during selective heat treatment: This method utilizes the precise temperature measurement and control technology of induction-laser composite heat source to achieve controllable surface heating temperature of strip tool during induction preheating-laser selective heat treatment-induction postheating low temperature tempering process, thereby precisely controlling the microstructure evolution under the synergistic effect of induction-laser composite heat source. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of dot matrix processing.

[0025] Figure 2 This is a schematic diagram of the horizontal stripe processing.

[0026] Figure 3 This is a schematic diagram of the longitudinal stripe processing. Detailed Implementation

[0027] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0028] This invention provides a method for induction preheating and laser selective enhancement of a strip-shaped cutting tool, comprising the following steps:

[0029] (1) Determine the array arrangement of the strengthening units according to the strengthening target parameters of the tool to be processed. That is, first select the position and size of the laser strengthening area on the workpiece surface, and then design the laser strengthening unit array within the selected area, including the shape, arrangement and size of the laser selective strengthening units. The shape of the laser selective strengthening units includes strip, circle, etc.; the arrangement includes dot matrix, stripe, dot matrix and stripe superposition, etc.

[0030] (2) Using a beam homogenization and shaping system, combined with a beam splitter and a mirror, a circular flat-top double beam is obtained, with the diameter of the circular homogenized beam ranging from 0.5 to 1.8 mm. When the laser selective enhancement unit is circular, the circular homogenized beam can completely cover a single laser selective enhancement unit; when the laser scanning enhancement unit is elongated, the circular homogenized beam must be able to cover the laser selective enhancement unit through continuous displacement along the width direction.

[0031] (3) Induction heating coils are set before and after the flat-top laser beam to induction preheat the hardened unit before laser selective quenching. The induction preheating temperature is 450-700℃. In order to ensure the effect of induction preheating and induction heating, the distance error between each position of the strip tool and the induction coil is required to be controlled within ±0.05mm.

[0032] (4) Perform selective laser strengthening. Use a circular flat-top double beam to perform synchronous selective laser scanning quenching on the two sides of the strip tool. Use a dual-color pyrometer to perform closed-loop temperature control on the selective laser strengthening unit to ensure that the laser strengthening unit remains in the austenitic phase region during laser irradiation.

[0033] Specifically, when the laser selective reinforcement unit is circular, a pulsed dual-beam irradiation heating method is adopted. That is, if the paraxial pyrometer detects that the temperature of the laser irradiation area continues to rise to the preset upper temperature limit (1000~1050℃), the laser is turned off to allow the laser irradiation unit to cool down. When the temperature of the laser irradiation unit drops to the preset lower temperature limit (800~830℃), the laser irradiation heating is started. Through pulsed laser energy injection, it is ensured that the circular reinforcement unit remains in the austenite phase region during the laser irradiation process. The number of pulsed laser irradiations is 3 to 20 times.

[0034] When the laser selective hardening unit is elongated, a scanning dual-beam irradiation heating method is adopted, which is based on a closed-loop temperature control system for the laser irradiation area. By controlling the laser power, the heating temperature of the laser irradiation area is ensured to be controlled between 800 and 1050°C. At the same time, the depth of the laser hardening layer can be increased by increasing the number of continuous scans.

[0035] (5) Perform post-heating low-temperature tempering. Use the induction heating coil set in step (3) and the bicolor pyrometer to perform temperature closed-loop controllable low-temperature tempering. The low-temperature tempering temperature is 170-240℃.

[0036] According to the above technical solution, in the preferred case, in step (1) to reduce the tempering softening caused by heat conduction between strengthening units, the spacing between adjacent strengthening units is greater than 3mm.

[0037] According to the above technical solution, in the preferred case, the scanning path of the flat-top laser beam in step (4) gradually moves from the blade edge to the back of the blade.

[0038] According to the above technical solution, in a preferred embodiment, the present invention is equipped with three off-axis pyrometers to measure the heating temperature of the induction preheating coil, the circular flat-top dual beam, and the induction postheating coil, respectively. Combined with a temperature closed-loop control system, the induction current and laser power are controlled online in a closed loop to ensure that the temperature control error of the induction / laser heating area is controlled within ±3℃.

[0039] According to the above technical solution, in a preferred embodiment, induction heating and laser selective enhancement are performed in an argon atmosphere.

[0040] Figure 1 , Figure 2 , Figure 3 There are three types of enhanced selection patterns, where the shaded areas are enhanced units. Figure 1 The pattern is a dot matrix, with the strengthening unit being circular in shape. The density distribution of the dot matrix is ​​from sparse on the back of the blade to dense on the edge, thereby achieving the effect of increasing hardness from the edge to the back of the blade. This pattern is suitable for the dual-beam pulse irradiation heating method. Figure 2 The pattern is a horizontal stripe pattern, the reinforcing unit is long and strip-shaped, and the reinforcing unit is distributed with sparse reinforcement on the back of the blade and dense reinforcement on the edge. This type of pattern is suitable for the dual-beam scanning irradiation heating method. Figure 3 The pattern is a mixture of dot matrix and stripe distribution, where the dot matrix and long stripes are used to strengthen the back of the blade, and the dense short stripes are used to strengthen the edge of the blade. This type of pattern is suitable for use in conjunction with dual-beam pulse / scanning irradiation heating methods.

[0041] Example 1:

[0042] This embodiment uses the above method to process the strip-shaped tool. The specific steps of induction preheating-laser selective enhancement are as follows:

[0043] (1) A strip-shaped cutting tool made of T10 steel is selected. The laser strengthening area is planned, and the strengthening array is distributed in a dot matrix. The strengthening unit is a circle with a diameter of 0.5mm. The arrangement of the strengthening units is as follows: Figure 1 As shown;

[0044] (2) Set the diameter of the circular homogenized dual-beam laser spot to 0.5 mm;

[0045] (3) Induction preheating: Place the tool to be processed in an argon atmosphere, select a copper induction coil with a diameter of 50 mm, and the distance between the coil and the tool is 1 mm. The preheating set temperature is 450℃. Use a two-color pyrometer with a temperature measurement accuracy of ≤ ±0.5% and a response time of ≤ 100 μs to detect the surface temperature of the preheating area. When the surface temperature reaches the set temperature, reduce the current of the induction coil and keep the preheating area warm for 60 s.

[0046] (4) Selective laser strengthening is performed. For the circular strengthening unit, a dual-beam pulse irradiation heating method is used. A dual-color pyrometer with a temperature measurement accuracy ≤ ±0.5% and a response time ≤ 100 μs is used for closed-loop temperature control of the strengthening unit. For a specific strengthening unit, laser irradiation is stopped when the surface temperature of the laser-irradiated area reaches 900℃; when the surface temperature of the laser-irradiated area is below 800℃, laser irradiation of the strengthening unit is resumed, and this process is repeated 3 times. For the entire laser-strengthened lattice, the laser irradiation sequence is left-right, blade-back. The entire process is carried out in an argon atmosphere.

[0047] (5) Post-heating low-temperature tempering: using the same coil and bicolor pyrometer as in (3) induction preheating, low-temperature tempering with closed-loop temperature control is performed. The post-heating temperature is set to 170°C and the duration is 60s.

[0048] (6) Based on the above parameters, the workpiece was processed using an induction preheating-laser selective hardening process. After cooling, the hardness and service life of the workpiece were tested. The hardness of the hardened area at the cutting edge was 740 HV, the depth of the hardened layer was 2.2 mm, and the service life was increased by 31% compared to the induction hardened tool.

[0049] Example 2:

[0050] This embodiment uses the above method to process the strip-shaped tool. The specific steps of induction preheating-laser selective enhancement are as follows:

[0051] (1) A strip-shaped cutting tool made of T10 steel is selected. The laser strengthening area is planned, and the strengthening array is distributed in a dot matrix pattern. The strengthening unit is a circle with a diameter of 1.8mm. The arrangement of the strengthening units is as follows: Figure 1 As shown;

[0052] (2) Set the diameter of the circular homogenized dual-beam laser spot to 1.8 mm;

[0053] (3) Induction preheating: Place the tool to be processed in an argon atmosphere, select a copper induction coil with a diameter of 50 mm, the distance between the coil and the tool is 0.5 mm, the preheating set temperature is 700℃, use a two-color high temperature meter with a temperature measurement accuracy of ≤±0.5% and a response time of ≤100μs to detect the surface temperature of the preheating area, when the surface temperature reaches the set temperature, reduce the current of the induction coil and keep the preheating area warm for 60s.

[0054] (4) Selective laser strengthening is performed. For the circular strengthening unit, a dual-beam pulse irradiation heating method is used. A dual-color pyrometer with a temperature measurement accuracy ≤ ±0.5% and a response time ≤ 100 μs is used for closed-loop temperature control of the strengthening unit. For a specific strengthening unit, laser irradiation is stopped when the surface temperature of the laser-irradiated area reaches 1050℃; when the surface temperature of the laser-irradiated area is below 950℃, laser irradiation of the strengthening unit is resumed, and this process is repeated 10 times. For the entire laser-strengthened lattice, the laser irradiation sequence is left-right, blade-back. The entire process is carried out in an argon atmosphere.

[0055] (5) Post-heating low-temperature tempering: using the same coil and bicolor pyrometer as in (3) induction preheating, low-temperature tempering with closed-loop temperature control is performed. The post-heating temperature is set to 170°C and the duration is 60s.

[0056] Based on the above parameters, an induction preheating-laser selective hardening process was used to process the workpiece. After cooling, the hardness and service life of the workpiece were tested. The hardness of the hardened area at the cutting edge was found to be 823 HV, the depth of the hardened layer was 3.1 mm, and the service life was improved by 34% compared to induction hardening tools.

[0057] Example 3:

[0058] This embodiment uses the above method to process the strip-shaped tool. The specific steps of induction preheating-laser selective enhancement are as follows:

[0059] (1) A strip-shaped tool made of T10 steel is selected. The laser strengthening area is planned, and the strengthening array is distributed in a striped array. The strengthening unit is a long strip with a width of 0.5mm. The arrangement of the strengthening units is as follows: Figure 2 As shown;

[0060] (2) Set the diameter of the circular homogenized dual-beam laser spot to 0.5 mm;

[0061] (3) Induction preheating: Place the tool to be processed in an argon atmosphere, select a copper induction coil with a diameter of 50 mm, the distance between the coil and the tool is 0.5 mm, the preheating set temperature is 450℃, use a two-color high temperature meter with a temperature measurement accuracy of ≤±0.5% and a response time of ≤100μs to detect the surface temperature of the preheating area, when the surface temperature reaches the set temperature, reduce the current of the induction coil and keep the preheating area warm for 90s.

[0062] (4) Selective laser enhancement is performed. For the circular enhancement units, a dual-beam scanning irradiation heating method is used. A dual-color pyrometer with a temperature measurement accuracy of ≤±0.5% and a response time of ≤100μs is used to perform closed-loop temperature control of the enhancement units. For a certain enhancement unit, when the surface temperature of the laser irradiated area reaches 1050℃, the laser beam scanning speed is increased; when the surface temperature of the laser irradiated area is below 1000℃, the scanning speed is decreased. For the entire laser enhancement array, the laser irradiation sequence is left-right, blade-back. The entire process is carried out in an argon atmosphere.

[0063] (5) Post-heating low-temperature tempering: using the same coil and bicolor pyrometer as in (3) induction preheating, low-temperature tempering with closed-loop temperature control is performed. The post-heating temperature is set to 170°C and the duration is 60s.

[0064] Based on the above parameters, the workpiece was processed using an induction preheating-laser selective hardening process. After cooling, the hardness and service life of the workpiece were tested. The hardness of the hardened area at the cutting edge was 860 HV, the depth of the hardened layer was 2.8 mm, and the service life was increased by 37% compared with the induction hardening tool.

[0065] Example 4:

[0066] This embodiment uses the above method to process the strip-shaped tool. The specific steps of induction preheating-laser selective enhancement are as follows:

[0067] (1) A strip-shaped tool made of T10 steel is selected. The laser strengthening area is planned, and the strengthening array is distributed in a striped array. The strengthening unit is a long strip with a width of 1.8mm. The arrangement of the strengthening units is as follows: Figure 2 As shown;

[0068] (2) Set the diameter of the circular homogenized dual-beam laser spot to 1.8 mm;

[0069] (3) Induction preheating: Place the tool to be processed in an argon atmosphere, select a copper induction coil with a diameter of 50 mm, and the distance between the coil and the tool is 1 mm. The preheating set temperature is 450℃. Use a two-color pyrometer with a temperature measurement accuracy of ≤ ±0.5% and a response time of ≤ 100 μs to detect the surface temperature of the preheating area. When the surface temperature reaches the set temperature, reduce the current of the induction coil and keep the preheating area warm for 60 s.

[0070] (4) Selective laser strengthening is performed. For the circular strengthening unit, a dual-beam scanning irradiation heating method is used. A dual-color pyrometer with a temperature measurement accuracy of ≤±0.5% and a response time of ≤100μs is used to perform closed-loop temperature control of the strengthening unit. For a certain strengthening unit, when the surface temperature of the laser irradiated area reaches 850℃, the laser beam scanning speed is increased; when the surface temperature of the laser irradiated area is lower than 800℃, the scanning speed is decreased. For the entire laser strengthening array, the laser irradiation sequence is left-right, blade-back. At the same time, the interval irradiation method is used for strengthening units with a spacing of less than 3mm. The entire process is carried out in an argon atmosphere.

[0071] (5) Post-heating low-temperature tempering: using the same coil and bicolor pyrometer as in (3) induction preheating, low-temperature tempering with closed-loop temperature control is performed. The post-heating temperature is set to 200℃ and the duration is 60s.

[0072] Based on the above parameters, an induction preheating-laser selective hardening process was used to process the workpiece. After cooling, the hardness and service life of the workpiece were tested. The hardness of the strengthened area at the cutting edge was 794 HV, the strengthened layer depth was 2.7 mm, and the service life was improved by 31% compared to induction hardening tools.

[0073] Example 5:

[0074] This embodiment uses the above method to process the strip-shaped tool. The specific steps of induction preheating-laser selective enhancement are as follows:

[0075] (1) A strip-shaped tool made of T10 steel is selected. The laser strengthening area is planned, and the strengthening array is a mixture of striped array and dot array. The strengthening unit is a strip with a width of 1.8 mm or a circle with a diameter of 0.5 mm. The arrangement of the strengthening units is as follows: Figure 3 As shown;

[0076] (2) Set the diameter of the circular homogenized dual-beam laser spot to 1.8 mm;

[0077] (3) Induction preheating: Place the tool to be processed in an argon atmosphere, select a copper induction coil with a diameter of 50mm, and the distance between the coil and the tool is 1mm. The preheating set temperature is 700℃. Use a two-color pyrometer with a temperature measurement accuracy of ≤±0.5% and a response time of ≤100μs to detect the surface temperature of the preheating area. When the surface temperature reaches the set temperature, reduce the current of the induction coil and keep the preheating area warm for 60s.

[0078] (4) Selective laser enhancement is performed. For the circular enhancement unit, a hybrid heating method of dual-beam scanning and pulsed irradiation is used. A dual-color pyrometer with a temperature measurement accuracy of ≤±0.5% and a response time of ≤100μs is used for closed-loop temperature control of the enhancement unit. For a certain elongated enhancement unit, when the surface temperature of the laser irradiated area reaches 850℃, the laser beam scanning speed is increased; when the surface temperature of the laser irradiated area is lower than 800℃, the scanning speed is reduced. For a certain circular enhancement unit, when the surface temperature of the laser irradiated area reaches 800℃, laser irradiation is stopped; when the surface temperature of the laser irradiated area is lower than 850℃, laser irradiation of the enhancement unit is resumed, and this process is repeated 15 times. For the entire laser enhancement array, the laser irradiation sequence is left-right, blade-back. The entire process is carried out in an argon atmosphere.

[0079] (5) Post-heating low-temperature tempering: using the same coil and bicolor pyrometer as in (3) induction preheating, low-temperature tempering with closed-loop temperature control is performed. The post-heating temperature is set to 240℃ and the duration is 60s.

[0080] Based on the above parameters, an induction preheating-laser selective hardening process was used to process the workpiece. After cooling, the hardness and service life of the workpiece were tested. The hardness of the reinforced area at the cutting edge was found to be 763 HV, the reinforced layer depth was 2.4 mm, and the service life was improved by 27% compared to induction hardening tools.

[0081] Example 6:

[0082] This embodiment uses the above method to process the strip-shaped tool. The specific steps of induction preheating-laser selective enhancement are as follows:

[0083] (1) Select a strip-shaped tool made of T10 steel, plan the laser strengthening area, and the strengthening array is a mixture of striped array and dot array. The strengthening unit is a strip with a width of 1mm or a circle with a diameter of 1mm. The arrangement of the strengthening units is as follows: Figure 3 As shown;

[0084] (2) Set the diameter of the circular homogenized dual-beam laser spot to 1 mm;

[0085] (3) Induction preheating: Place the tool to be processed in an argon atmosphere, select a copper induction coil with a diameter of 50 mm, the distance between the coil and the tool is 0.5 mm, the preheating set temperature is 600℃, use a two-color high temperature meter with a temperature measurement accuracy of ≤±0.5% and a response time of ≤100μs to detect the surface temperature of the preheating area, when the surface temperature reaches the set temperature, reduce the current of the induction coil and keep the preheating area warm for 60s.

[0086] (4) Selective laser enhancement is performed. For the circular enhancement unit, a hybrid heating method of dual-beam scanning and pulsed irradiation is used. A dual-color pyrometer with a temperature measurement accuracy of ≤±0.5% and a response time of ≤100μs is used for closed-loop temperature control of the enhancement unit. For a certain elongated enhancement unit, when the surface temperature of the laser-irradiated area reaches 1050℃, the laser beam scanning speed is increased; when the surface temperature of the laser-irradiated area is lower than 1000℃, the scanning speed is reduced. For a certain circular enhancement unit, when the surface temperature of the laser-irradiated area reaches 1050℃, laser irradiation is stopped; when the surface temperature of the laser-irradiated area is lower than 950℃, laser irradiation of the enhancement unit is resumed, and this process is repeated 20 times. For the entire laser enhancement array, the laser irradiation sequence is left-right, blade-back. The entire process is carried out in an argon atmosphere.

[0087] (5) Post-heating low-temperature tempering: using the same coil and bicolor pyrometer as in (3) induction preheating, low-temperature tempering with closed-loop temperature control is performed. The post-heating temperature is set to 170°C and the duration is 60s.

[0088] Based on the above parameters, the workpiece was processed using an induction preheating-laser selective hardening process. After cooling, the hardness and service life of the workpiece were tested. The hardness of the hardened area at the cutting edge was 850 HV, the depth of the hardened layer was 3.1 mm, and the service life was increased by 38% compared with the induction hardening tool.

[0089] It will be apparent to those skilled in the art that the present invention can be modified in various ways, and such modifications are not considered to depart from the scope of the invention. All such modifications that are obvious to those skilled in the art are included within the scope of the claims.

Claims

1. A method for induction preheating-laser selective enhancement of a strip-shaped cutting tool, characterized in that, Includes the following steps: (1) Determine the array arrangement of the strengthening units according to the strengthening target parameters of the tool to be processed. That is, first select the position and size of the laser strengthening area on the workpiece surface, and then design the laser strengthening unit array within the selected area, including designing the shape, arrangement and size of the laser selective strengthening unit; the shape of the laser selective strengthening unit is a strip or a circle; the arrangement includes dot matrix, stripe or dot matrix stripe superposition. If the reinforcing unit is circular in shape and arranged in a dot matrix pattern, the density distribution of the dot matrix is ​​from sparse on the back of the blade to dense on the edge; if the reinforcing unit is elongated in shape and arranged in a horizontal stripe pattern, the distribution of the reinforcing unit is from sparse on the back of the blade to dense on the edge. If the arrangement is a dot matrix stripe overlay, the dots and long stripes are used to strengthen the back of the blade, while the dense short stripes are used to strengthen the edge of the blade. (2) Using a beam homogenization and shaping system, combined with a beam splitter and a mirror, a circular flat-top double beam is obtained, with the diameter of the circular homogenized beam ranging from 0.5 to 1.8 mm. When the laser selective enhancement unit is circular, the circular homogenized beam must be able to completely cover a single laser selective enhancement unit. When the laser scanning enhancement unit is elongated, the circular homogenized beam must be able to cover the laser selective enhancement unit through continuous displacement along the width direction. (3) Perform induction preheating. Induction heating coils are set in front of and behind the circular flat-top double beam to perform induction preheating on the hardening unit before laser selective quenching. The induction preheating temperature is 450~700℃. (4) Perform selective laser strengthening. Use a circular flat-top double beam to perform synchronous selective laser scanning quenching on the two sides of the strip tool. Use a dual-color pyrometer to perform closed-loop temperature control on the selective laser strengthening unit to ensure that the laser strengthening unit remains in the austenitic phase region during laser irradiation. (5) Perform post-heating low-temperature tempering. Use the induction heating coil set in step (3) and the bicolor pyrometer to perform temperature closed-loop controllable low-temperature tempering. The low-temperature tempering temperature is 170~240℃.

2. The method for induction preheating-laser selective enhancement of strip-shaped cutting tools according to claim 1, characterized in that, In step (4), when the laser selective reinforcement unit is circular, a pulsed dual-beam irradiation heating method is adopted. That is, if the paraxial pyrometer detects that the temperature of the laser irradiation area continues to rise to the preset upper temperature limit, i.e., 1000~1050℃, the laser is turned off to allow the laser irradiation unit to cool down. When the temperature of the laser irradiation unit drops to the preset lower temperature limit, i.e. 800~830℃, the laser irradiation heating is started. Through pulsed laser energy injection, it is ensured that the circular reinforcement unit always remains in the austenitic phase region during the laser irradiation process. The number of pulsed laser irradiations is 3~20 times. When the laser selective reinforcement unit is elongated, a scanning dual-beam irradiation heating method is adopted. That is, based on the temperature closed-loop control system of the laser irradiation area, the heating temperature of the laser irradiation area is controlled at 800~1050℃ by controlling the laser power.

3. The method for induction preheating-laser selective enhancement of strip-shaped cutting tools according to claim 2, characterized in that, The distance error between the strip cutter and the induction coil at each position is controlled within ±0.05mm.

4. The method for induction preheating-laser selective enhancement of strip-shaped cutting tools according to claim 3, characterized in that, The interval between adjacent laser selective enhancement units is greater than 3mm.

5. The method for induction preheating-laser selective enhancement of strip-shaped cutting tools according to claim 4, characterized in that, In step (4), the scanning path of the flat-top laser beam gradually moves from the blade edge to the back of the blade.

6. The method for induction preheating-laser selective enhancement of strip-shaped cutting tools according to claim 5, characterized in that, Induction preheating, laser selective enhancement, and post-heating cryogenic tempering were carried out in an argon atmosphere.

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