ã€China Aluminum Industry Network】 1. Process Requirements In the production of aluminum extrusion, the larger output is mainly determined by the extrusion speed, and the quality of the profile depends on the profile extrusion temperature. With the extrusion speed increasing, the extrusion temperature of the profile will increase significantly. When the temperature exceeds a certain value, various problems will occur in the aluminum structure and surface quality. Therefore, the aluminum outlet temperature must be monitored at any time. Testing to ensure a better match between extrusion yield and profile quality.
2. Instrument Introduction Temperature detection is divided into contact and non-contact two categories. In aluminum extrusion production, it is common practice to use rapid thermocouple contact to detect the temperature of the aluminum material. During the extrusion process, the profile is always moving. The detection element must move along with the profile and cannot be monitored online. Different methods, the profile immediately after the die cooling, resulting in a large deviation of the detection temperature detection, it is difficult to get an accurate match between temperature and speed. At this time, often through the past experience, the operator visually inspects the surface quality of the profile, and determines the extrusion speed of the profile in conjunction with temperature detection. The instability of the human operation also leads to instability of the product quality and output.
In order to eliminate the above-mentioned conventional thermocouple contact methods to detect defects, many factories began to look for online temperature detection methods. Because of the characteristics of production, online monitoring can only be detected by non-contact methods. At present, the infrared temperature detector is used successfully. The principle is that all objects radiate infrared rays. The size of infrared radiation energy and its distribution according to wavelength are closely related to the surface temperature of the object. Therefore, by measuring the infrared temperature, the surface temperature can be accurately determined. Generally, the emissivity of a general object is stable. When the temperature of the target is measured with an infrared radiation thermometer, the infrared radiation amount of the target in its wavelength range is measured, and the temperature of the measured target can be calculated.
For aluminum alloy profiles, due to its low emissivity and large fluctuations, resulting in large fluctuations in infrared radiation, coupled with the influence of smoke and dust in the environment, the profile is shaken after ejection, and the traditional single-wavelength measurement cannot be used to obtain an accurate temperature. In order to accurately measure the temperature, it is necessary to use a multi-wavelength method to measure, and the change of the emissivity with a special calculation and compensation can be solved. The compensation calculation method must take into account changes in the profile section and alloy composition.
We conducted field test tests on various infrared thermometers and found that many infrared thermometers claim to be able to detect aluminum profiles. In fact, they can only detect certain profiles with simple cross-sections, and only overcome the emissivity of aluminum caused by surface light. In the low case, when the section of the profile changes, the parameters of the instrument must be manually set to obtain the accurate temperature value, and intelligent correction of the parameters cannot be performed according to the actual situation. Therefore, the range of use is narrow. One of the key issues is that such pyrometers do not take effective measures to eliminate the interference caused by the multiple changes in the shape of the aluminum cross section and its own reflection of the radiant energy, especially for profiles with more fins or grooves. This interference is obvious. After comparative tests, it is currently available for aluminum extrusion on-line testing, and only those infrared thermometers that have specialized software to effectively filter or suppress the above interference.
3. In the same industry promotion The infrared temperature measuring instrument used by our company adopts multi-wavelength detection method. The infrared thermometer of the instrument consists of optical system, photodetector, signal amplifier, signal processing and display output. The optical system collects the infrared radiation energy and emissivity of the band measured by the target in the field of view, and then converts the photodetector and converts it into a corresponding electrical signal. The signal passes through the amplifier and the signal processing circuit, and is converted into the temperature value of the measured target after being calibrated according to the algorithm and the target emissivity of the meter. The instrument default algorithm is its special compensation calculation software. During the measurement, after taking into account the infrared radiation energy, emissivity, and measured wavelength of the measured aluminum material, the accurate temperature is calculated by a special compensation operation.
4. Summary The above compensation calculation is based on the actual production data of a large number of profiles and is essentially a complete and effective database collected for different profiles and conditions. When used, the detected signals will be stored in the database. Comprehensive comparison of the given data makes it possible to accurately determine the measured surface temperature of the profile. This operation is also equipped with a high signal dilution factor, which effectively overcomes the attenuation of the infrared thermometer optical system due to lens contamination, smoke, and water vapor, adapts to various cross-sectional forms, especially multiple fin forms, and improves anti-interference ability. At the same time give users intelligent tips for maintenance.
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