Metal additive manufacturing molten pool temperature calibration method

Abstract

The invention provides a metal additive manufacturing molten pool temperature calibration method. The method comprises the following steps that dynamic temperature information of a molten pool in the metal additive manufacturing process is monitored through infrared thermal imaging equipment; the monitored dynamic temperature information of the molten pool is imported into a computer with data processing software, and the temperature of the molten pool is calibrated through the solid-liquid phase line temperature of the molten pool; and the temperature field information of the dynamic molten pool of the whole molten pool in the metal additive manufacturing process is obtained based on the molten pool solid-liquid phase line temperature. According to the method, the measurement precision of the thermal infrared imager on the temperature of the molten pool is improved, the trafficability and flexibility of the thermal infrared imager in the field of metal additive manufacturing are improved, a large amount of data about the temperature of the molten pool and emissivity changes can be generated in the temperature calibration process, and the accuracy of temperature calibration is improved. The data can provide rich information for researching thermophysical phenomena, material phase change and the like in the metal additive manufacturing process, and the additive manufacturing process can be deeply understood and optimized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of additive manufacturing of metal materials, and particularly relates to a molten pool temperature calibration method for metal additive manufacturing. BACKGROUND

[0002] Metal additive manufacturing technology has been widely used in aerospace, biomedical and many other fields due to its short production cycle and high material utilization. However, the molten pool in the metal additive manufacturing process is in an extreme metallurgical environment with ultra-high temperature gradient and ultra-fast solidification rate. The complex molten pool behavior can lead to the generation of internal defects in the metal additive component. Infrared thermal imaging has unique advantages in temperature distribution monitoring and process quality control of metal additive manufacturing process due to its non-contact measurement, fast response speed and temperature difference identification.

[0003] Emissivity is an important parameter related to the post-processing of infrared thermal imaging temperature data, which represents the thermal radiation characteristics of an object and is affected by parameters such as material type, temperature and surface roughness. However, the molten pool temperature changes dynamically during the metal additive manufacturing process, resulting in changes in the emissivity of the molten pool. Most infrared thermal imaging monitoring systems have a default emissivity value, which greatly affects the accuracy of the monitored temperature.

[0004] Therefore, a molten pool temperature calibration method for metal additive manufacturing is proposed to reduce the cost of temperature distribution monitoring and process quality control in metal additive manufacturing process and to expand the application scenarios of infrared thermal imaging in the field of additive manufacturing. SUMMARY

[0005] The technical problem to be solved by the application is to provide a molten pool temperature calibration method for metal additive manufacturing to solve the problems in the background art.

[0006] To solve the above technical problems, the technical solution adopted by the application is as follows: a molten pool temperature calibration method for metal additive manufacturing, comprising the following steps: S1, monitoring the dynamic temperature information of the molten pool in the metal additive manufacturing process by using an infrared thermal imaging device; S2, importing the monitored dynamic temperature information of the molten pool into a computer with data processing software, and calibrating the molten pool temperature by using the solid-liquid phase line temperature of the molten pool; S3, obtaining the temperature field information of the dynamic molten pool in the metal additive manufacturing process based on the solid-liquid phase line temperature of the molten pool.

[0007] As a further description of the application, the infrared thermal imaging device is specifically an infrared thermal imager, which is installed in front of the observation window of the additive manufacturing field of view, and records the straight-line distance from the infrared thermal imager to the additive manufacturing field of view.

[0008] As a further illustration of the present application, the infrared thermal imager has a temperature measurement range not less than the melting point of the metal material, and a spatial resolution of at least 15 microns.

[0009] As a further illustration of the present application, the monitoring width of the infrared thermal imager is not less than 1 mm, and the monitoring length is not less than 2 mm.

[0010] As a further illustration of the present application, the infrared thermal imager is a high-speed infrared thermal imager, and the acquisition frequency meets the high scanning speed sample temperature field evolution monitoring requirement.

[0011] As a further illustration of the present application, before metal additive manufacturing, the measured environmental parameters, the linear distance from the infrared thermal imager to the additive manufacturing field of view, and the optical transmittance of the observation window material are input into the data processing software to obtain the dynamic temperature information of the molten pool in the additive manufacturing process.

[0012] As a further illustration of the present application, the environmental parameters are specifically air temperature, relative humidity, and visibility.

[0013] As a further illustration of the present application, the observation window material is quartz glass.

[0014] As a further illustration of the present application, the temperature of the molten pool boundary pixel point is recorded as the molten pool temperature.

[0015] As a further illustration of the present application, the material emissivity value in the data processing software is corrected after the temperature data.

[0016] Compared with the prior art, the present application has the following advantages: The present application improves the measurement accuracy of the infrared thermal imager for the molten pool temperature, and improves the passability and flexibility of the infrared thermal imager in the field of metal additive manufacturing. During the temperature calibration process, a large amount of data about the molten pool temperature and the change of emissivity will be generated. These data can provide rich information for the research of thermal physical phenomena and material phase change in the metal additive manufacturing process, and help to understand and optimize the additive manufacturing process. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a molten pool temperature distribution diagram of the metal additive manufacturing process without correction; Figure 2 is a molten pool temperature distribution diagram of the metal additive manufacturing process after non-uniform treatment; Figure 3 is the temperature of the molten pool boundary pixel area after calibration; Figure 4 is a molten pool temperature distribution diagram of the metal additive manufacturing process after correcting the emissivity. DETAILED DESCRIPTION

[0018] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects clearer, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. The specific embodiments described herein are only used to explain the present application, and are not used to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0019] It should be further explained that the drawings and embodiments of the present application mainly describe the concept of the present application. On the basis of the concept, some specific forms and settings of connection relationship, position relationship, power mechanism, power supply system, hydraulic system and control system, etc. may not be completely described, but those skilled in the art can realize the above-mentioned specific forms and settings by using well-known methods on the premise of understanding the concept of the present application.

[0020] When an element is referred to as being "fixed" or "set" on another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or indirectly connected to the other element.

[0021] The orientation words "inner, outer" refer to the inner and outer relative to the contour of each component itself. The orientation or position relationship indicated by the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner" or "outer" is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0022] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways, and the spatial relative descriptions used herein will be interpreted accordingly.

[0023] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, and "several" means one or more, unless otherwise explicitly specified.

[0024] Unless otherwise specified, the materials, tools, and equipment used in the embodiments of this invention are all commercially obtained.

[0025] like Figures 1-4 As shown, the present invention provides a technical solution: a method for calibrating the molten pool temperature in metal additive manufacturing. Specifically, the metal material used is TC4 titanium alloy powder with a particle size distribution conforming to normal distribution, and its particle size range is 15-53μm. The additive manufacturing is carried out using selective laser melting process with BLT-S210 equipment. The observation window of the BLT-S210 equipment is replaced with quartz glass, with an infrared transmittance of over 90%. A single-pass forming experiment is conducted with a laser power of 300W, a scanning rate of 1200mm / s, and a powder layer thickness of 40μm. Includes the following steps: S1. Utilize infrared thermal imaging equipment to monitor the dynamic temperature information of the molten pool during the metal additive manufacturing process. As one possible implementation method in this embodiment, the infrared thermal imaging device is an infrared thermal imager; Specifically, the FLIR X8580 Mid-Wave (MWIR) thermal imager was selected, with a temperature measurement range of 0~2500℃, a temporal resolution of 1KHz, a spatial resolution of 15μm, and a 2×2mm square area for monitoring field of view. The infrared thermal imager is mounted in front of the observation window of the additive manufacturing field of view via a triangular support frame, and the straight-line distance from the infrared thermal imager to the additive manufacturing field of view is recorded. In this embodiment, the straight-line distance between the infrared thermal imager and the additive manufacturing field of view is 0.1m.

[0026] Before performing metal additive manufacturing, the measured environmental parameters, including air temperature, relative humidity and visibility, the straight-line distance from the infrared thermal imager to the additive manufacturing field of view and the optical transmittance of the observation window material, are input into the data processing software to obtain dynamic temperature information of the molten pool during the additive manufacturing process. A single-pass forming experiment was conducted to correct the position of the infrared thermal imager, enabling it to additively manufacture the field of view. The straight-line distance parameter from the infrared thermal imager to the additive manufacturing field of view was then updated in the data processing software.

[0027] Obtain dynamic temperature information of the molten pool during additive manufacturing, such as Figure 1 The image shows a preliminary, uncorrected temperature distribution diagram of the molten pool during the metal additive manufacturing process.

[0028] S2. Import the monitored dynamic temperature information of the molten pool into a computer with data processing software, and calibrate the molten pool temperature using the solid-liquid phase temperature of the molten pool. In this embodiment, Reveal IR is selected as the data processing software. Environmental parameters, including air temperature, relative humidity, visibility, the straight-line distance from the infrared thermal imager to the additive manufacturing field of view, and the optical transmittance of the observation window material are input into the data processing software for non-uniformity preprocessing to remove the influence of background and noise.

[0029] The non-homogenization processing result in this embodiment is as follows: Figure 2 As shown; In this embodiment, the molten pool temperature is calibrated using the solid-liquid phase temperature of the molten pool as follows: The temperature of the outermost pixel is defined as the melting point temperature. In this embodiment, the melting point temperature of the selected TC4 titanium alloy is 1660~1690℃. Figure 3 The image shows the temperature of the molten pool boundary pixel region after calibration in this example. After homogenization, the molten pool boundary consists of the numerical region and the background region.

[0030] The temperature increases sequentially from the edge of the molten pool to the center. The pixels in the red box are the outermost pixels, and the average temperature of the outermost pixels is 1672.7℃, which meets the melting temperature range of titanium alloy.

[0031] S3. Based on the solid-liquid phase temperature of the molten pool, obtain the dynamic temperature field information of the entire molten pool during the metal additive manufacturing process.

[0032] According to the calibration results of the solid-liquid phase line temperature of the molten pool, the material emissivity value in the temperature data post-processing software is corrected, the temperature field information of the dynamic molten pool in the whole metal additive manufacturing process is obtained, and the final result is as shown in Figure 4

[0033] It should be noted that, in this document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0034] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, alternatives, and variations can be made in the embodiments without departing from the spirit and scope of the present application as defined by the appended claims and their equivalents.​

Claims

1. A metal additive manufacturing melt pool temperature calibration method, characterized by: The method comprises the following steps: S1, monitoring the dynamic temperature information of the molten pool in the metal additive manufacturing process by using an infrared thermal imaging device; S2, importing the monitored dynamic temperature information of the molten pool into a computer with data processing software, and calibrating the molten pool temperature by using the solid-liquid phase line temperature of the molten pool; S3, obtaining the temperature field information of the dynamic molten pool in the metal additive manufacturing process based on the solid-liquid phase line temperature of the molten pool.

2. A metal additive manufacturing melt pool temperature calibration method according to claim 1, wherein, The infrared thermal imaging device is specifically an infrared thermal imager, which is installed in front of the observation window of the additive manufacturing field of view, and records the straight-line distance from the infrared thermal imager to the additive manufacturing field of view.

3. A metal additive manufacturing melt pool temperature calibration method according to claim 2, wherein, The temperature measurement range of the infrared thermal imager is not less than the melting point of the metal material, and the spatial resolution of the infrared thermal imager is at least 15 μm.

4. The method of claim 2, wherein: The monitoring width of the infrared thermal imager is not less than 1 mm, and the monitoring length is not less than 2 mm.

5. The method of claim 2, wherein: The infrared thermal imager is a high-speed infrared thermal imager, and the acquisition frequency meets the temperature field evolution monitoring requirements of high scanning rate samples.

6. The method of metal additive manufacturing melt pool temperature calibration of claim 2, wherein, Before the metal additive manufacturing is performed, the measured environmental parameters, the straight-line distance from the infrared thermal imager to the additive manufacturing field of view, and the optical transmittance of the material of the observation window are input into the data processing software to obtain the dynamic temperature information of the molten pool in the additive manufacturing process.

7. A metal additive manufacturing melt pool temperature calibration method according to claim 6, wherein, The environmental parameters are specifically air temperature, relative humidity, and visibility.

8. The method of metal additive manufacturing melt pool temperature calibration of claim 6, wherein, The material of the observation window is quartz glass.

9. The method of metal additive manufacturing melt pool temperature calibration of claim 1, wherein, The temperature of the molten pool boundary pixel point is recorded as the molten pool temperature.

10. The method of metal additive manufacturing melt pool temperature calibration of claim 1, wherein, In S3, the boundary temperature is calibrated to the solidus temperature according to the solid-liquid phase line temperature calibration result of the molten pool, and the material emissivity value in the data processing software is corrected after correcting the temperature data according to the material emissivity of the material.

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