The relationship between the detection results of the handheld spectrometer and the surface cleanliness of the sample

The handheld spectrometer, also known as the handheld X-ray fluorescence spectrometer analyzer, uses X-ray fluorescence technology to perform non-destructive testing and prepare a smooth and clean detection surface, which is beneficial for testing but not conducive to the in-situ and on-site rapid detection advantages of the handheld spectrometer. However, the state of the sample also directly affects the final detection result of the handheld spectrometer.

Whether the surface of metallic materials is oxidized or rusted is related to the material's material quality, heat treatment state, surface condition, environment, time, etc. A dense oxide film is formed on the surface of high-chromium-nickel stainless steel, which prevents the oxidation reaction from developing in depth. Even if the surface is not polished, it does not significantly affect the test. The surfaces of carbon steel, cast iron and some alloy steels are oxidized. Even if there is no rust on their surfaces, it will interfere with the test. Light non-ferrous metals are reactive and prone to oxidation, while heavy non-ferrous metals have better chemical stability.

The handheld spectrometer directly tests the surfaces of medium and low alloy steels that are constantly naturally oxidized and the surfaces that have produced floating rust. The content of Mn increases, while the contents of Cr and V decrease. When testing the dense rust layer after removing the floating rust, the contents of Cr, Mo and v often increase significantly. Forced oxidation of medium and low alloy steel such as normalizing and tempering will form oxide scale. The outer surface of the oxide scale has no Cr or V, while the contents of Cr, Mo, V and Nb on the inner surface of the oxide scale increase several times. The contents of Cr, Mo and v on the outer surface of the sample after the oxide scale is removed also increase significantly. Tests show that oxidation or rusting is the main factor affecting the test results, while surface treatments such as nitriding have no significant impact on the tests.

Depending on the degree of oxidation or rusting of the material and the subsequent precision requirements, angular polishing machines, files, sandpapers, (metallographic) sandpapers, scrapers, etc. can be selected to process the material onto the main body as the inspection surface. Chemical treatment can also be selected. After the surface of metal materials is processed to the body, they are usually inspected immediately. For surfaces that have been manually or mechanically processed, it is advisable to inspect within one day. For some alloy steels that have been stored for a relatively long time, such as KI2F54B alloy steel, inspection after 30 days has not shown any significant impact.

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Plate-shaped, block-shaped, strip-shaped, square tubular, medium-sized columnar and conical (cross-section) materials, etc. are easy to obtain detection surfaces that can completely cover the measurement window (and contact window), thereby achieving the best detection results. When testing circular tubular (columnar), conical tubular and other materials, axial testing is superior to tangential testing. When the diameter is greater than 11 mm, The detection results in the two directions are basically consistent (when the diameter is between 12 and 63 mm, there is no induction in the tangential direction of the contact window). When testing small-sized columnar, tubular and filamentous materials, appropriately extending the testing time and calibrating with physical samples of fixed values is conducive to improving the accuracy.

The characteristic X-rays of light elements have low energy and low fluorescence yield, and are easily absorbed by the air. The detection of light elements has high requirements for HXRFS and the surface of the sample. Although there is still room for improvement in terms of enhancing the accuracy and precision of the detection results of light elements, the detection results are basically satisfactory.

With the advancement of hardware technology, analysis software technology and application technology of handheld X-ray fluorescence spectrometers, HXRFS has gradually moved from the qualitative and semi-quantitative analysis stages such as waste sorting, mixed material screening, batch spot checks, product screening and census, and metal material grade identification to the era of quantitative analysis.