快速凝固过程中的温度测量

Temperature Measurement during Rapid Solidification

设计了一种适用于深过冷液态金属快速凝固研究的宽量程简易红外温度计，其测量范围为９２３～２２７３Ｋ，响应时间小于１ｍｓ，最小目标Φ１．４ｍｍ，精度可达１％～２％。提出了一种分步恒温标定方法，在七种不同实验条件下对这一简易红外温度计和高精度ＮＱＯ７／１３ＣＩＶ１２５－２Ｍ－ＥＳＰＵ红外测温系统进行了标定，由此导出一种简易标定法，并分析了提高快速凝固过程中测温精度的途径。

An infrared pyrometer with simple construction(named DIY type) was designed, which showed a measurment range of 923￣2 273K, a response time of less than 1 ms, a minimum target size of 41.4 mm, and an accuracy of 1%￣2%. As RF induction melting was widely applied in rapid solidification processing, a low-pass RC filter was also contrived to reduce the 300￣500 kHz high frequency disturbance by 42￣51 dB. A stepwise isothermal calibrating procedure was developed during which a pyomctcr was calibrated against a standard thermocouple or another well calibrated pyrometer under isothermal conditions at a succssion of temperatures. Both the DIY pyrometer and a commercial high-accuracy Yunnan-Land NQO7/ 13C1V125-2M-ESPU infrared temperature-sensing system were calibrated with this method under seven different experimental conditions characteristic of the undcrcooling processing by glass fluxing. It was found that the output voltage E of DIY pyrometer varied cxponentially with sample temperature-E=Ac-B/T-and that the rcgrcssion line Inn￣T-1 maintained an approximately constant slope under different experimental conditions for a certain metal or alloy. Similarly, during glass fluxing undcrcooling experiments the slope of the linear calibration line T=c+kE of Yunan-Land NQO7/ 13C1V125-2M-ESPU system did not vary with the compositon of the molten inorganic glass surrounding a metallic sample. Based upon this discovery,a simplified calibration method was proposed. For a given metallic material, if the slopes (B or k) of the calibration curves of the infrared thermometers under one experimental condition had been determined through stepwise isothermal calibration, their calibration curves for any other experimental conditions could be simply obtained by the relations where Em represented the thermometer output at the material melting point Tm under the changed experimental conditions. Both experimental investigations and theoretical analyses indicated that the key step to enhancing temperature measurement accuracy was to keep calibration conditions in strict consistency with the actual situation of rapid solidification processing.