Stainless steel has excellent corrosion resistance and is widely used in many fields of society. With the development of society, there are more and more types of stainless steel. At present, the main analysis methods used for stainless steel composition analysis are handheld X-ray fluorescence analysis, wet analysis, system spectrum analysis, X-ray fluorescence spectrometer analysis, and ICP-AES method.
Handheld X-ray fluorescence analysis:
Handheld X-ray fluorescence spectrometer is an effective analysis method for non-destructive, rapid, and semi-quantitative analysis. It is often used in the process of quickly determining the material on site, distinguishing waste materials without damage, and qualitatively determining the type of metal materials. Its disadvantages are that the accuracy of the analysis is not high, and trace elements cannot be analyzed. Therefore, this method is generally not used for accurate analysis of stainless steel products.
Wet analysis method:
The wet analysis method uses a single-element analysis method, and the operation process is cumbersome; if the same sample is tested for multiple elements, it takes a long time, and more reagents are used in the analysis process. Some reagents are still toxic and harmful, which are harmful to the test personnel and the environment to a certain extent. With the rapid development of instruments, trace elements in stainless steel can be replaced by instrumental analysis, but the analysis of high-content elements still requires wet analysis.
Direct reading spectral analysis:
Direct reading spectrometer has the advantages of fast analysis speed, high accuracy, simple operation, and small sample consumption. However, the measurement precision of spectral quantitative analysis of high-content elements is relatively low, and the accuracy is not high. There are several reasons: First, the high content of alloy elements in stainless steel will affect the content of non-metallic elements. In this case, the measurement results of non-metallic element content will be inaccurate; secondly, in the process of detecting the composition of stainless steel, the analysis channel of non-metallic elements will fall into the ultraviolet region, in this case, it will cause deviations in the analysis results; finally, in the process of detecting different types of stainless steel, since the instrument used is the same spectrometer, in this case, it will cause the analysis electrode of the operating table to be contaminated, resulting in a high detection result of the alloy element content, resulting in inaccurate detection results. Another limiting factor of the direct reading spectrometer is that the position of the exit slit used by each instrument has been set before leaving the factory and is not easy to change. This is convenient for routine analysis of fixed elements, but it has poor adaptability to changes in analysis tasks.
X-ray fluorescence spectrometer analysis:
X-ray fluorescence spectrometry has the characteristics of fast analysis speed, relatively simple sample processing, small accidental error, and high analysis accuracy, and has been widely used in steel analysis. X-ray fluorescence spectrometry (XRF) has the advantages of a wide analysis content range and high accuracy when used for stainless steel analysis. Wang Huaming et al. used the basic parameter method and the empirical coefficient method of pH mode to determine Si, Mn, P, S, Ni, Cr, Cu, Mo, V, Ti, Nb, Co, and W in chromium stainless steel and nickel-chromium stainless steel series by X-ray fluorescence spectrometry. The empirical coefficient method and the basic parameter method were combined to correct the absorption-enhancement effect and Puxian overlapping interference between coexisting elements, and the steel spectrum standard sample was determined by X-ray fluorescence spectrometry. The calibration curve was established to complete the quantitative analysis of 15 elements including Al, Si, P, Ti, Cr, Mn, V, Co, Ni, Cu, W, As, Sn, Mo, and Pb. The determination of spectral background, calculation of spectral overlap between coexisting elements, and correction of matrix absorption-enhancement effect in the process of method establishment were discussed. Compared with the literature, this literature adds the analysis of two elements, Sb, and expands the measurement range of elements such as Si, Mn, W, and Ni by 7 times. Due to the characteristics of the X-ray fluorescence spectrometer itself, the accuracy of the detection results of elements with a content of less than 0.01% in stainless steel is not high. In addition, the matrix of the X-ray fluorescence spectrometer has a great influence on the analysis results, and the adaptability of the working curve is poor. If the material changes slightly, the working curve needs to be redrawn, and more standard steel is required.
ICP-AES analysis:
Inductively coupled plasma atomic emission spectrometer (ICP-AES) can simultaneously determine multiple elements in a complex iron matrix. It has the advantages of high sensitivity, low detection limit, good stability, elimination of background interference, wide linear range of element analysis detection, fast analysis speed, and simultaneous determination of multiple elements. It is widely used in chemical element analysis of metal materials. It can analyze elements with a content of less than 0.001% in stainless steel. The main work of ICP-AES determination of the chemical composition of each element in stainless steel is: first, to solve the sample dissolution problem, requiring all the elements to be measured to be dissolved and not affecting the atomization efficiency of the ICP-AES torch and nebulizer; second, to solve the matrix interference, we can use the matrix matching method to solve the matrix interference; finally, to select the analysis line and reduce the spectral line interference, and the interference factor correction (IEC) and multi-line fitting technology can be used to reduce the impact of spectral interference.
By comparing the analysis methods of various elements in stainless steel, it is found that each method has its advantages and insurmountable disadvantages. With the development of stainless steel materials, it has been more and more widely used in nuclear reactor engineering. With the continuous development of nuclear reactor engineering technology, new requirements are put forward for stainless steel materials, and the content of various elements in the material directly affects its performance. There are more and more trace elements required to be analyzed, such as Pb, As, Sn, Sb, Bi, Hg, Cd, Zn, Ce, La, etc. The common characteristics of these elements are more interference, low sensitivity, and extremely low content in stainless steel, and there is a certain difficulty in analysis. Compare and select the chemical analysis methods of various elements in stainless steel. ICP-AES can analyze these elements simultaneously to meet the requirements of steel nuclear power products.
