A temperature measurement system and method for a powder bed laser fusion melt pool

Abstract

The application discloses a kind of powder bed laser melting pool temperature measurement system and method, belong to the technical field of additive manufacturing.The system includes: powder bed laser melting device, including forming cavity, forming platform and continuous fiber laser, continuous fiber laser is used to generate laser, laser is irradiated on metal powder, melts metal powder, to form molten pool;Molten pool temperature measuring device, including dichroic mirror, beam splitter, first infrared narrowband filter, second infrared narrowband filter, first photodiode and second photodiode;The thermal radiation infrared light beam emitted outward by molten pool is reflected after dichroic mirror, reaches beam splitter, and the light beam is divided into two ways by beam splitter;Two light beams reach two photodiodes respectively;Data processing device is used to obtain molten pool temperature according to the signal calculated by two photodiodes acquisition.The absolute temperature of molten pool is measured by two photodiodes, with the advantages of high sampling frequency, high measurement accuracy and low cost.

Description

Technical Field

[0001] This invention relates to the technical field of additive manufacturing, and in particular to a temperature measurement system and method for a powder bed laser melting pool. Background Technology

[0002] Laser powder bed fusion (LPBF) scans metal powder on a powder bed according to a planned 3D model, selectively melting and solidifying the powder to form a solid metal object. This technology offers high forming precision and excellent mechanical properties, and is currently widely used in aerospace, biomedical, and automotive industries.

[0003] The heat source is the driving force for LPBF forming, where metal powder melts and solidifies layer by layer to form parts with metallurgical strength. Heat distribution and heat transfer are key factors affecting the quality of the formed parts; therefore, it is necessary to measure the molten pool temperature in real time during the forming process. Non-contact temperature measurement methods are generally used to measure the molten pool temperature. Currently used instruments include infrared thermal imagers and pyrometers; however, these instruments have low sampling frequencies and are expensive, making them unsuitable for industrial production.

[0004] In addition, since the accuracy of the instrument will decrease after a period of use, it is necessary to calibrate the temperature measuring instrument to ensure its measurement accuracy. Since powder bed laser melting non-contact temperature measuring instruments are often coaxially mounted and difficult to disassemble, it is necessary to study in-situ traceability devices. Summary of the Invention

[0005] In order to at least partially solve one of the technical problems existing in the prior art, the purpose of this invention is to provide a temperature measurement system and method for a powder bed laser melting pool.

[0006] The technical solution adopted in this invention is:

[0007] A temperature measurement system for a powder bed laser melting pool includes:

[0008] A powder bed laser melting device includes a forming cavity, a forming platform, and a continuous fiber laser. The forming cavity is equipped with a powder spreading unit, and the forming platform includes a forming cylinder. The powder spreading unit is used to spread metal powder onto the forming cylinder. The continuous fiber laser is used to generate laser light, which irradiates the metal powder to melt the metal powder and form a molten pool. During selective laser melting, the forming platform is positioned below the forming cavity.

[0009] A molten pool temperature measuring device includes a dichroic mirror, a beam splitter, a first infrared narrowband filter, a second infrared narrowband filter, a first photodiode, and a second photodiode. The infrared beam of thermal radiation emitted from the molten pool is reflected by the dichroic mirror and then reaches the beam splitter, which divides the beam into two paths. One path passes through the first infrared narrowband filter to reach the first photodiode, and the other path passes through the second infrared narrowband filter to reach the second photodiode. The center wavelengths of the first and second infrared narrowband filters are different.

[0010] A data processing device, connected to the first photodiode and the second photodiode, is used to calculate the molten pool temperature based on the signals collected by the two photodiodes.

[0011] Furthermore, the temperature measurement system also includes a traceability device, which includes a blackbody radiation source used to generate a preset temperature;

[0012] When tracing the temperature measurement value, the continuous fiber laser is turned off, and the tracing device is placed below the molding cavity;

[0013] The thermal radiation infrared beam generated by the blackbody radiation source is reflected by the dichroic mirror and reaches the beam splitter, which splits the beam into two paths; one beam passes through the first infrared narrowband filter and reaches the first photodiode, and the other beam passes through the second infrared narrowband filter and reaches the second photodiode.

[0014] The temperature value of the blackbody radiation source is calculated based on the signals collected by the two photodiodes. The photodiodes are calibrated based on the calculated temperature value and the preset temperature value to achieve traceability of the temperature measurement value.

[0015] Furthermore, the data processing device calculates the molten pool temperature using the following formula:

[0016]

[0017] Where λ1 is the center wavelength of the first infrared narrowband filter, λ2 is the center wavelength of the second infrared narrowband filter, M1 is the product of the output signal of the first photodiode and the spectral emissivity of the actual object at wavelength λ1, and M2 is the product of the output signal of the second photodiode and the spectral emissivity of the actual object at wavelength λ2; C2 is the second radiation constant, C2=hc / k=1.438769×10 -2 (M×Kelvin), where k is Boltzmann's constant, h is Planck's constant, and c is the speed of light.

[0018] Furthermore, the powder bed laser melting device also includes a field mirror, a galvanometer, and a collimator;

[0019] The laser emitted by the continuous fiber laser is collimated by the collimator, transmitted by the dichroic mirror, positioned by the galvanometer, and focused by the field mirror before reaching the forming cylinder.

[0020] The infrared beam of thermal radiation emitted from the molten pool passes sequentially through the field mirror, the galvanometer, and the dichroic mirror before being reflected onto the beam splitter.

[0021] Furthermore, the powder spreading unit includes a powder spreading cart, a powder spreading guide rail, and an air intake guide rail;

[0022] The powder spreading cart is used to scrape metal powder from the powder cylinder and drop it after reaching a preset position along the powder spreading guide rail;

[0023] The air inlet guide rail is used to input protective gas. During the LPBF molding process, it is necessary to ensure that the molding cavity is filled with inert protective gas to prevent oxidation of the processed material. The air inlet guide rail can make the protective airflow into the molding cavity more uniform.

[0024] Furthermore, the wavelength of the laser generated by the continuous fiber laser is 1064 nm; the shortest transmission wavelength of the dichroic mirror is greater than 1000 nm and less than 1064 nm; and the shortest reflection wavelength of the dichroic mirror is less than 800 nm.

[0025] Furthermore, the beam splitter has a beam splitting ratio of 1:1.

[0026] Furthermore, the center wavelength of the first infrared narrowband filter is 800nm, and the center wavelength of the second infrared narrowband filter is 900nm.

[0027] Furthermore, the forming platform is disposed within the first unit cavity, and the blackbody radiation source is disposed within the second unit cavity;

[0028] The first unit cavity and the second unit cavity are integrally formed and movably installed below the forming cavity. During laser selective melting, the first unit cavity is moved below the forming cavity; when tracing the temperature measurement value, the second unit cavity is moved below the forming cavity.

[0029] Furthermore, the first unit cavity is also equipped with a powder cylinder and a powder recovery cylinder. The powder cylinder is used to hold metal powder, and the powder recovery cylinder is used to collect waste powder.

[0030] Furthermore, the blackbody radiation source is determined based on the temperature measurement range.

[0031] Another technical solution adopted in this invention is:

[0032] A method for measuring the temperature of a powder bed laser melting pool, applied to the system described above, includes the following steps:

[0033] A laser is irradiated onto metal powder to melt the powder and form a molten pool.

[0034] The infrared beam of thermal radiation emitted from the molten pool is reflected by the dichroic mirror and reaches the beam splitter, which splits the beam into two paths; one beam passes through the first infrared narrowband filter and reaches the first photodiode, and the other beam passes through the second infrared narrowband filter and reaches the second photodiode.

[0035] The signals collected by the two photodiodes are acquired, and the temperature of the molten pool is calculated based on the acquired signals.

[0036] Furthermore, the temperature measurement method also includes a step of tracing the temperature measurement values:

[0037] Turn off the continuous fiber laser, place the blackbody radiation source below the forming cavity, and control the blackbody radiation source to generate a preset constant temperature.

[0038] The thermal radiation infrared beam generated by the blackbody radiation source is reflected by the dichroic mirror and reaches the beam splitter, which splits the beam into two paths; one beam passes through the first infrared narrowband filter and reaches the first photodiode, and the other beam passes through the second infrared narrowband filter and reaches the second photodiode.

[0039] The temperature value of the blackbody radiation source is calculated based on the signals collected by the two photodiodes. The photodiodes are calibrated based on the calculated temperature value and the preset temperature value to achieve traceability of the temperature measurement value.

[0040] Furthermore, the temperature measurement method also includes a step of calibrating the temperature measuring components within the temperature measurement system, the temperature measuring components including a thermal imager and a pyrometer.

[0041] The beneficial effects of this invention are: this invention measures the absolute temperature of the molten pool using two photodiodes, and has the advantages of high sampling frequency, high measurement accuracy and low cost.

[0042] In addition, this invention enables in-situ measurement and traceability of molten pool temperature within the same system, avoiding the problems of low efficiency, low accuracy and high cost associated with traditional offline traceability. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following description is provided with accompanying drawings of the relevant technical solutions in the embodiments of the present invention or the prior art. It should be understood that the accompanying drawings described below are only for the purpose of clearly illustrating some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the structure of a temperature measurement system for a powder bed laser melting pool according to an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of the traceability device in an embodiment of the present invention;

[0046] Figure 3 This is a flowchart illustrating the steps of a method for measuring the temperature of a powder bed laser melting pool according to an embodiment of the present invention;

[0047] Figure 4 This is a flowchart illustrating the implementation method of a non-contact powder bed laser melting pool temperature in-situ measurement and traceability system in an embodiment of the present invention.

[0048] Reference numerals in the attached figures: 1-Powder spreading cart; 2-Galvanometer; 3-Field lens; 4-Dichroic mirror; 5-Beam splitter; 6-First infrared narrowband filter; 7-First focusing lens; 8-First photodiode; 9-Second infrared narrowband filter; 10-Second focusing lens; 11-Data acquisition card; 12-Second photodiode; 13-Collider; 14-Continuous fiber laser; 15-Powder spreading guide rail; 16-Air inlet guide rail; 17-Blackbody radiation source; 18-Forming cylinder; 19-Powder cylinder. Detailed Implementation

[0049] The embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. The step numbers in the following embodiments are set only for ease of explanation, and there is no limitation on the order between the steps. The execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0050] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0051] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0052] Furthermore, in the description of this invention, unless otherwise stated, "multiple" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0053] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0054] like Figure 1 As shown, this embodiment provides a temperature measurement system for a powder bed laser melting pool, including:

[0055] A powder bed laser melting device includes a forming cavity, a forming platform, and a continuous fiber laser 14. The forming cavity is equipped with a powder spreading unit, and the forming platform includes a forming cylinder 18. The powder spreading unit is used to spread metal powder onto the forming cylinder 18. The continuous fiber laser 14 is used to generate laser light, which irradiates the metal powder to melt the metal powder and form a molten pool. During selective laser melting, the forming platform is positioned below the forming cavity.

[0056] The molten pool temperature measuring device includes a dichroic mirror 4, a beam splitter 5, a first infrared narrowband filter 6, a second infrared narrowband filter 9, a first photodiode 8, and a second photodiode 12. The infrared beam of thermal radiation emitted from the molten pool is reflected by the dichroic mirror 4 and then reaches the beam splitter 5, which splits the beam into two paths. One path passes through the first infrared narrowband filter 6 to reach the first photodiode 8, and the other path passes through the second infrared narrowband filter 9 to reach the second photodiode 12. The center wavelengths of the first infrared narrowband filter 6 and the second infrared narrowband filter 9 are different.

[0057] A data processing device, connected to the first photodiode 8 and the second photodiode 12, is used to calculate the molten pool temperature based on the signals collected by the two photodiodes.

[0058] The working principle of the temperature measurement system in this embodiment is as follows: The powder spreading unit in the forming cavity acquires metal powder from the powder cylinder and spreads the metal powder at a preset position on the forming cylinder 18. The laser beam selectively melts the powder on the plane of the forming cylinder 18, thereby forming a molten pool. After the metal solidifies, powder spreading and melting continue, eventually forming a processed product. As an optional implementation, the powder spreading cart scrapes the powder from the powder cylinder onto the top of the forming cylinder and spreads it evenly using a scraper below it. For each layer formed, the powder cylinder moves up one layer and the forming cylinder moves down one layer, and the powder spreading cart spreads powder once, repeating the cycle. As another optional implementation, the metal powder is placed in a powder cylinder located near the forming platform. Metal powder is sucked up through a powder suction nozzle or other powder suction components, and the sucked metal powder is transported to the top of the forming platform for spreading via a moving platform. As an alternative implementation, the metal powder is placed in a powder bottle located outside the forming cavity. The powder bottle is connected to a powder dispensing nozzle located inside the forming cavity via a pipe. Air pressure forces the metal powder from the powder bottle onto the powder dispensing nozzle, which is then moved to a preset position by a motion platform for powder application. See also... Figure 1 In this embodiment, the powder spreading unit includes a powder spreading cart 1, a powder spreading guide rail 15, and an air inlet guide rail 16. The powder spreading cart 1 is used to scrape metal powder from the powder cylinder 19 and spread it to the forming cylinder 18 via the powder spreading guide rail 15.

[0059] In some embodiments, the laser emission can be controlled by the laser head, and the laser irradiation position can be changed so that the laser irradiates different positions on the molding platform; in other embodiments, the molding platform can be moved in a two-dimensional direction so that the laser irradiates different positions on the molding platform.

[0060] The infrared radiation beams emitted from the molten pool are reflected by dichroic mirrors 4 and then split into two beams by a beam splitter 5. These beams propagate through two separate optical paths: one consisting of a first infrared narrowband filter 6 and a first focusing lens 7, and the other consisting of a second infrared narrowband filter 9 and a second focusing lens 10. The latter two beams are then received by a first photodiode 8 and a second photodiode 12, respectively, and the converted signals are transmitted to a data acquisition card 11 for storage. Based on the emissivity of the material and using Wayne's offset law, the absolute temperature of the molten pool is calculated. In this embodiment, a focusing lens is placed between the infrared narrowband filter and the photodiode to ensure better illumination of the photodiode.

[0061] The formula for calculating the molten pool temperature is as follows:

[0062]

[0063] See Figure 1 and Figure 2 In some optional embodiments, the temperature measurement system further includes a traceability device, which includes a blackbody radiation source 17 for generating a preset temperature.

[0064] When tracing the temperature measurement value, the continuous fiber laser 14 is turned off, and the tracing device is placed below the molding cavity;

[0065] The thermal radiation infrared beam generated by the blackbody radiation source 17 is reflected by the dichroic mirror 4 and reaches the beam splitter 5, which splits the beam into two paths; one path passes through the first infrared narrowband filter 6 and reaches the first photodiode 8, and the other path passes through the second infrared narrowband filter 9 and reaches the second photodiode 12.

[0066] The temperature value of the blackbody radiation source 17 is calculated based on the signals collected by the two photodiodes. The two photodiodes are calibrated based on the calculated temperature value and the preset temperature value to achieve traceability of the temperature measurement value.

[0067] The temperature measurement system includes an additive manufacturing mode and a traceability mode. As described above, in additive manufacturing mode, the forming platform is located directly below the forming cavity to heat the metal powder. In traceability mode, the forming platform is moved out, and the blackbody radiation source 17 is moved below the forming cavity. Specifically, the opening at the top of the blackbody radiation source 17 must be coaxial with the galvanometer 2.

[0068] It should be noted that when the temperature measurement system is in traceability mode, the blackbody radiation source 17 can be used not only to calibrate photodiodes, but also to calibrate temperature measuring components such as thermal imagers and pyrometers, and avoids the need to disassemble the system, greatly improving efficiency and accuracy.

[0069] See Figure 1 In some optional embodiments, the powder bed laser melting device further includes a field mirror 3, a galvanometer 2, and a collimator 13; the laser emitted by the continuous fiber laser 14 is collimated by the collimator 13, transmitted by the dichroic mirror 4, positioned by the galvanometer 2, and focused by the field mirror 3 before reaching the forming cylinder 18.

[0070] The infrared beam of thermal radiation emitted from the molten pool passes sequentially through the field mirror 3, the galvanometer 2, and the dichroic mirror 4, and is reflected onto the beam splitter 5.

[0071] In this embodiment, the continuous fiber laser 14 and the molten pool temperature measuring device share a single set of field mirror 3 and galvanometer 2, effectively reducing costs. In the optical path emitted by the continuous fiber laser 14, the laser beam is collimated by collimator 13, then transmitted through dichroic mirror 4, and subsequently passes through galvanometer 2 and field mirror 3 before reaching the forming cylinder 18 to heat the metal powder. Simultaneously, the thermal radiation infrared beam emitted from the molten pool passes through field mirror 3 and galvanometer 2 before reaching dichroic mirror 4, where it is reflected and reaches beam splitter 5. As an optional implementation, the beam splitter 5 has a 1:1 splitting ratio. As an optional implementation, the dichroic mirror is a long-pass dichroic mirror. As an optional implementation, when the temperature measurement system is in traceability mode, the center of the forming cylinder 18 should be coaxial with the field mirror 3.

[0072] In some optional embodiments, the wavelength of the laser generated by the continuous fiber laser 14 is 1064 nm; the shortest transmission wavelength of the dichroic mirror 4 is greater than 1000 nm and less than 1064 nm; the shortest reflection wavelength of the dichroic mirror 4 is less than 800 nm; the center wavelength of the first infrared narrowband filter 6 is 800 nm, and the center wavelength of the second infrared narrowband filter 9 is 900 nm.

[0073] See Figure 1 In some optional embodiments, the forming platform is disposed in the first unit cavity, and the blackbody radiation source 17 is disposed in the second unit cavity;

[0074] The first unit cavity and the second unit cavity are integrally formed and movably installed below the forming cavity. During laser selective melting, the first unit cavity is moved below the forming cavity; when tracing the temperature measurement value, the second unit cavity is moved below the forming cavity.

[0075] The first and second unit cavities can slide along the bottom of the forming cavity. Optionally, when the temperature measurement system is in traceability mode, the blackbody radiation source 17 slides to the bottom of the forming cavity, and its upper opening is coaxial with the galvanometer 2. When the temperature measurement system switches between different operating modes, only the first or second unit cavity needs to be switched, making control simple, convenient, and easy to operate. In addition, different blackbody radiation sources 17 can be replaced according to the temperature measurement range.

[0076] In summary, compared with the prior art, the temperature measurement system of this embodiment has at least the following advantages and beneficial effects:

[0077] (1) This application integrates in-situ temperature measurement and traceability technology of molten pool, which can realize high-precision and high-real-time in-situ dynamic temperature measurement of molten pool during the powder bed laser melting process, and provide a temperature measurement range that meets the measurement accuracy requirements, thereby verifying the temperature measurement level of the developed measuring device.

[0078] (2) This application integrates a molding platform and a blackbody radiation source in the same work station and in situ, realizing high-precision, high-real-time and traceable in-situ temperature measurement, which can avoid the problems of reduced efficiency and increased cost caused by disassembling temperature measuring components for calibration.

[0079] (3) This application uses two temperature detectors to collect the radiation light from the molten pool, and through spectral splitting, filtering, noise reduction and other processing, it uses dual-color light to calculate the dynamic temperature of the additive molten pool with high precision and high real-time performance. It can replace relatively expensive temperature measuring instruments such as colorimetric pyrometers, greatly reducing the cost of instruments and is suitable for industrial production applications.

[0080] See Figure 3 Based on the temperature measurement system described above, this embodiment also provides a method for measuring the temperature of a powder bed laser melting pool, including the following steps:

[0081] S301. The laser is irradiated onto the metal powder to melt the metal powder and form a molten pool;

[0082] S302. The infrared beam of thermal radiation emitted from the molten pool is reflected by the dichroic mirror and reaches the beam splitter, which splits the beam into two paths; one path of the beam passes through the first infrared narrowband filter and reaches the first photodiode, and the other path of the beam passes through the second infrared narrowband filter and reaches the second photodiode.

[0083] S303. Acquire the signals collected by the two photodiodes and calculate the molten pool temperature based on the collected signals.

[0084] The above method will be explained in detail below with reference to the accompanying drawings and specific embodiments.

[0085] See Figure 4This embodiment provides a method for implementing a non-contact powder bed laser melting pool temperature in-situ measurement and traceability system, including the following steps:

[0086] S401, Additive manufacturing: The laser emitted by the continuous laser is collimated and galvanometer and then selectively irradiates the powder bed to form a molten pool, which is then melted and shaped to complete the additive manufacturing process of the part.

[0087] S402, Signal Acquisition: During the processing, the thermal radiation light in the molten pool is reflected by the galvanometer and the long-pass dichroic mirror and the surface of the beam splitter. The beam splitter splits the beam into two paths, which are then filtered by a narrow-band filter and focused by a long-focusing lens and captured by two photodiodes respectively.

[0088] S403. Calculate the molten pool temperature: Substitute the emissivity of the material to be processed and the collected optical signal into Wayne's offset law to perform photoelectric signal-temperature signal conversion and calculate the molten pool temperature.

[0089]

[0090] S404. In-situ traceability of photodiodes: Slide the molding platform along the bottom of the molding cavity and move the traceability device below the galvanometer, so that the opening at the top of the blackbody is coaxial with the galvanometer. Use the photodiode to measure the blackbody at a constant temperature. The photodiode is calibrated according to the difference between the measured temperature value and the actual temperature value of the blackbody, so that the measurement results are traceable.

[0091] S405. Replace the traceability device with a laser selective melting device: After traceability is completed, slide the traceability device out along the bottom of the forming cavity and move the forming platform back to its original position;

[0092] S406. Depending on the different metal alloy materials, repeat steps S401-S405 to complete the traceable in-situ measurement of the absolute temperature of the molten pool during the additive manufacturing process of the parts.

[0093] This application also discloses a computer program product or computer program, which includes computer instructions stored in a computer-readable storage medium. A processor of a computer device can read the computer instructions from the computer-readable storage medium and execute the computer instructions, causing the computer device to perform... Figure 3 and Figure 4 The method shown.

[0094] In the foregoing description of this specification, references to terms such as "one embodiment," "another embodiment," or "some embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0095] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

[0096] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A temperature measurement system for a powder bed laser melting pool, characterized in that, include: A powder bed laser melting device includes a forming cavity, a forming platform, and a continuous fiber laser. The forming cavity is equipped with a powder spreading unit, and the forming platform includes a forming cylinder. The powder spreading unit is used to spread metal powder onto the forming cylinder. The continuous fiber laser is used to generate laser light, which irradiates the metal powder to melt the metal powder and form a molten pool. During selective laser melting, the forming platform is positioned below the forming cavity. The molten pool temperature measuring device includes a dichroic mirror, a beam splitter, a first infrared narrowband filter, a second infrared narrowband filter, a first photodiode, and a second photodiode. The laser emitted by the continuous fiber laser passes through the collimator, the dichroic mirror for transmission, the galvanometer position adjustment, and the field lens for focusing before reaching the forming cylinder. The infrared beam of thermal radiation emitted from the molten pool is reflected sequentially by the field mirror, the galvanometer, and the dichroic mirror before reaching the beam splitter. The thermal radiation infrared beam is split into two paths by a beam splitter: one beam passes through a first infrared narrowband filter and reaches a first photodiode, and the other beam passes through a second infrared narrowband filter and reaches a second photodiode. The center wavelengths of the first infrared narrowband filter and the second infrared narrowband filter are different. The wavelength of the laser generated by the continuous fiber laser is 1064 nm. The shortest transmission wavelength of the dichroic mirror is greater than 1000 nm and less than 1064 nm; the shortest reflection wavelength of the dichroic mirror is less than 800 nm. The center wavelength of the first infrared narrowband filter is 800nm, and the center wavelength of the second infrared narrowband filter is 900nm; A data processing device, connected to the first photodiode and the second photodiode, is used to calculate the molten pool temperature based on the signals collected by the two photodiodes. Source tracing device, including a blackbody radiation source; The molding platform is disposed in the first unit cavity, and the blackbody radiation source is disposed in the second unit cavity; The first unit cavity and the second unit cavity are integrally formed and movably installed below the forming cavity. During laser selective melting, the first unit cavity is moved below the forming cavity. When tracing the temperature measurement value, the continuous fiber laser is turned off, and the second unit cavity is moved below the forming cavity. This allows the thermal radiation infrared beam generated by the blackbody radiation source to be received by the first photodiode and the second photodiode respectively through the same field mirror, galvanometer, dichroic mirror and beam splitter optical path as when measuring the temperature of the molten pool, so as to perform in-situ coaxial calibration.

2. The temperature measurement system for a powder bed laser melting pool according to claim 1, characterized in that, The data processing device calculates the molten pool temperature using the following formula: in, The second radiation constant, The center wavelength of the first infrared narrowband filter. The center wavelength of the second infrared narrowband filter. The output signal of the first photodiode and the actual object at a wavelength The product of spectral emissivity, The output signal of the second photodiode is compared with the actual object at wavelength. The product of the lower spectral emissivity.

3. The temperature measurement system for a powder bed laser melting pool according to claim 1, characterized in that, The powder spreading unit includes a powder spreading cart, a powder spreading guide rail, and an air intake guide rail; The powder spreading cart is used to scrape metal powder from the powder cylinder and drop it after reaching a preset position along the powder spreading guide rail; The air intake rail is used to input protective gas.

4. The temperature measurement system for a powder bed laser melting pool according to claim 1, characterized in that, The beam splitter has a beam splitting ratio of 1:

1.

5. A method for measuring the temperature of a powder bed laser melting pool, applied to the system described in any one of claims 1-4, characterized in that, Includes the following steps: A laser is irradiated onto metal powder to melt the powder and form a molten pool. The infrared beam of thermal radiation emitted from the molten pool is reflected by the dichroic mirror and reaches the beam splitter, which splits the beam into two paths; one beam passes through the first infrared narrowband filter and reaches the first photodiode, and the other beam passes through the second infrared narrowband filter and reaches the second photodiode. The signals collected by the two photodiodes are acquired, and the temperature of the molten pool is calculated based on the acquired signals.

6. The method for measuring the temperature of a powder bed laser melting pool according to claim 5, characterized in that, The temperature measurement method also includes a step of tracing the temperature measurement values: Turn off the continuous fiber laser, place the blackbody radiation source below the forming cavity, and control the blackbody radiation source to generate a preset constant temperature. The thermal radiation infrared beam generated by the blackbody radiation source is reflected by the dichroic mirror and reaches the beam splitter, which splits the beam into two paths; one beam passes through the first infrared narrowband filter and reaches the first photodiode, and the other beam passes through the second infrared narrowband filter and reaches the second photodiode. The temperature value of the blackbody radiation source is calculated based on the signals collected by the two photodiodes. The photodiodes are calibrated based on the calculated temperature value and the preset temperature value to achieve traceability of the temperature measurement value.

7. The method for measuring the temperature of a powder bed laser melting pool according to claim 5, characterized in that, The temperature measurement method further includes a step of calibrating the temperature measuring components in the temperature measurement system, including a thermal imager and a pyrometer.

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