盐浴复合热处理技术是一种新型表面处理技术, 能增强工件的耐磨性、 耐腐蚀性和耐疲劳性, 在金属表面处理中得到广泛的应用。 氮化盐中氰酸根、 氰化物和铁离子的含量对该热处理技术的质量控制十分重要, 因此需要准确测定该三成分的含量以保证金属表面处理的质量。 针对目前业内所采用的化学滴定法难以满足自动化分析的技术要求, 基于分光光度法, 采用510, 620和697 nm三个不同波长的单色LED光源、 耦合光纤、 光电二极管搭建了一台半自动氮化盐三参数分析实验装置, 实现氰酸根、 氰化物和铁离子的快速准确测试。 该半自动实验装置除了光路系统外, 还有搅拌控制系统、 恒温控制系统、 数据采集电路系统。 氰酸盐检测采用间接检测方法, 先通过化学方法把氰酸根转变为铵根, 再根据标准GB 7481—1987水质铵的测定-水杨酸分光光度法, 通过对铵离子的测定(检测波长697 nm)间接测量氰酸根。 氰化物检测依据标准HJ484—2009水质氰化物的测定-异烟酸-巴比妥酸分光光度法(检测波长620 nm)。 铁离子含量的检测依据标准HJ345—2007水质铁的测定-邻菲啰啉分光光度法, 光谱检测特征波长为510 nm。 对LED光源光强稳定性进行了测试, LED光源一开始工作光强即达到稳定值; 测试了耦合光纤对LED光源的光谱影响, 单色光源通过耦合光纤和单光纤的光谱没有发生变化, 只是通过耦合光纤后光强值有所降低; 测试了搅拌对LED光源光强稳定性影响, 搅拌系统对光学系统没有影响。 利用实验装置测量出不同浓度氰酸根标准样品氰酸钾、 氰根标准样品氰化钾、 铁离子标准样品硫酸亚铁的吸光度, 基于朗伯比尔定律, 建立氰酸根、 氰化物和铁离子标样的拟合曲线, 其线性相关度 R²分别为0.990 7, 0.999 6和0.998 1, 线性度高; 氰酸根、 氰根和铁离子的预测样品均值最大相对误差和最大相对标准偏差RSD分别为4.53%和1.04%, 2.29%和0.79%, 4.2%和0.7%, 说明三样品测试结果准确性高、 重复性好; 氰酸根、 氰根和铁离子的最低检出限LOD分别为0.017, 0.009和0.005 mg·L^-1。 比较了用设计的氮化盐三成分半自动检测装置与传统化学滴定法测得的氮化盐样品中的氰酸根、 氰化物和铁离子含量, 设计的检测系统测试结果优于传统的化学滴定法, 其中测试的氮化盐样品的氰酸根、 氰化物和铁离子均值相对误差和相对标准方差RSD分别为4.17%和0.69%, 1%和0.58%, 4%和0.29%。 各项测试结果均达到设计要求, 为盐浴复合热处理技术氮化盐三成分半自动分析仪提供了理论和技术支持。 论文搭建的氮化盐三成分半自动检测装置的光路系统采用单色LED光源、 多进一出耦合光纤对光源分光, 实现多参数的快速准确检测, 整套光学检测系统无任何活动部件, 大大降低了光学检测系统带来的系统误差, 保证了测试的准确度和重复性。

Salt bath compound heat treatment technology is a new kind of metal surface treatment technology, which can enhance the wearability, corrosion and fatigue resistance of workpiece, and it is widely used. In order to guarantee the quality of metal surface treatment, it is very important to accurately determine the content of the Cyanate, Cyanide and Iron ion in nitriding salt. At present, it is difficult for the chemical titration method adopted by industry to satisfy the requirements for the automated analysis. Based on the spectrophotometric method, a semi-automatic nitriding salt parameter detection setup using 510, 620 and 697 nm of three different wavelengths of monochromatic LED light source, a coupling optical fiber and three photodiodes, which can fastly and exactly test the content of the Cyanate, Cyanide and Iron ion. The semi-automatic nitriding salt parameter detection setup includes the Optical system, mixing control system, constant temperature control system and data acquisition circuit. By the indirect method determining the content of Cyanate, converting the Cyanate ions into ammonium ions by chemical method, and then measuring the content of ammonium ions in water according to the national standard GB 7481—1987 Water quality-Determination of ammonium-Spectrophotometric method with salicylic acid, the characteristic absorption wavelength of ammonium is 697 nm. Determining the content of Cyanide according to the national standard HJ 484—2009 Water quality-Determination of Cyanide-Volumetric and Spectrophotometry method, the characteristic absorption wavelength of Cyanide is 620 nm. Determining the content of iron according to the national standard HJ 345—2007 Water quality-determination of Iron-phenanthroline spectrophotometry, the characteristic absorption wavelength of ammonium is 510 nm. In this setup, the light intensity stability of LED light source is tested, and the LED light intensity is a stable value when it starts working. Testing the influence of the coupled optical fibers, the spectrum of the monochromic LED light has not changed between through a coupling fiber and a single fiber, and just the optical intensity decreases a little when the light through the coupling fiber. Testing the stability of the LED light by stirring, the data showed the mixing control system has no effect on the optical system. Using the experimental device to measure the absorbance of Cyanate standard sample-potassium cyanate, Cyanide standard sample-potassium cyanide and iron standard sample-ferrous sulfate, based on the lambert beer’s law, establishing a Cyanate, Cyanide and Iron standard sample fitting curve, whose linear correlation R² is 0.990 7, 0.999 6, 0.998 1, respectively, which has high linearity. The maximum mean relative error and maximum relative standard deviation of Cyanate, Cyanide and Iron in predicted samples were 4.53% and 1.04%, 2.29% and 0.79%, 4.2% and 0.7%, respectively. The limit of detection of Cyanate, Cyanide and Iron were 0.017, 0.009 and 0.005 mg·L^-1, respectively. By contrasting the traditional chemical test method, the experiment setup test the Cyanate, Cyanide and Iron ion in nitriding salt, the test result of the detection system is superior to the traditional chemical titration method, and the maximum mean relative error and maximum relative standard deviation of Cyanate, Cyanide and Iron in nitriding salt sample were 4.17% and 0.69%, 1% and 0.58%, 4% and 0.29%, respectively. The results of these tests meet the design requirements and provide theoretical and technical support for the tri-component semi-automatic analyzer for salt bath compound heat treatment technology. The optical path system of experiment setup includes three monochromatic LEDs light source and a coupling fiber, which realizes the rapid and accurate detection and multi-parameter detection of the light source spectral. The whole optical inspection system has no moving parts, which greatly reduces the system error brought by the optical detection system, which guarantees the accuracy and repeatability of the analyzer test.