Research On High Temperature Measurement In Laser Cladding Based On Spectrum

As one of the basic properties of objects, temperature irreplaceable affects the properties of materials in laser cladding. In this process, the organization and the subsequent stress have been affected in large extent by temperature. Meanwhile, with the temperature of pool changed, the pool’s shape, size and the object’s forming accuracy, deposition rate, surface finish, powder adhesion, etc also changed. These factors affected the quality of cladding at last. So with the development of laser cladding technology, the quality control systems were researched extensively and the corresponding results were obtained. But in actual circumstances, because of features of laser cladding such as fast solidification rate of molten pool and small molten pool, the conventional methods of temperature measurement cannot be used effectively. Today, the main temperature measurement in laser cladding is contact measurement with the simulation of temperature field, but this method can’t meet the requirement of laser cladding, although it is instructive for temperature measunng.In order to obtain temperature, the carbon steel was used as the object, CO2laser was used to heat the material, and fiber optic spectrometer was used to gather the material’s spectrum. For the purpose of the exact temperature, the spectrum curves should be treated by noises removing and smooth processing. And infrared temperature measuring instrument and thermocouple were used to inspect error. In the method and theoretical studies of spectral temperature measurement, the innovative work of this paper is listed as follows.1. As for the actual situation of higher temperature measurement during laser manufacturing and remanufacturing processes, the real-time temperature measurement system was designed and set up, in consideration of the effects of background light noise, smoke and the difference between calibration of temperature measurement system and this system.2. Because accrual relationship between emissivity and temperature wavelength cannot be obtained, the mathematical treatment for Wayne blackbody radiation formula was performed in this paper. Through this method, the influence of emissivity to temperature measurement errors has been reduced in maximum extent. And after limiting the waveband, this method can achieve high temperature measuring for most objects. 3. Considering the situation of higher measurement errors of traditional colorimetric temperature measurement system, the improved principle of data processing was proposed, the error sources of traditional system were analyzed, and then the emission rate of a certain type of object in colorimetric measurement system was invited. After experimental verification, the error of this system was confirmed to reduce obviously.4. The error sources of temperature measurement system were analyzed by experimental measurements and experimental data processing theory. In measurement aspect, because of the effect of non-uniform laser beams and environmental noise, the spectrum obtained by the spectrometer contains lots of noise, which causes measurement errors. In date processing aspect, due to the difference between the assume emissivity model and the actual model, the measuring errors were caused. Both of the errors were quantitatively analyzed in this paper.