SPECTROLABM9 direct reading spectrometer is a photoelectric spectrometer that uses the principle of atomic emission spectrometry to quickly and quantitatively analyze the chemical composition of metal samples such as blocks and rods.
1. Analysis principle
The sample is excited under the excitation light source, and its atoms and ions transition to emit light, which enters the optical system and is dispersed into the spectral lines of the element. Measure the intensity of the selected internal standard line and the analysis line. According to the correlation between the intensity of the element spectrum and the concentration of the measured element, the content of the measured element in the sample is obtained by using the persistent curve method and the control sample method.
2.1 Spectrum: Spectrum refers to the spectrum formed by the electromagnetic radiation arranged in order of wavelength (or frequency).
2.2 Standard sample method: This method is to excite a series of standard samples (requires that the standard sample and the sample have the same smelting process and crystal structure) before each sample analysis to make a calibration curve. Fit and store the working curve according to the correlation between the intensity of the element spectral line and the concentration of the tested element, then excite the sample to be tested, and calculate the concentration of the tested element from the working curve.
2.3 Durable curve method: This method is to prepare a durable calibration curve with the standard sample method in advance. Only the sample to be tested is excited during each analysis, and the concentration of the element to be measured is calculated from the durable curve. Due to environmental changes and various changes in the internal devices of the instrument, the calibration curve will drift. Therefore, in actual analysis, the calibration curve drift must be corrected with a standardized sample every day (each shift), that is, the calibration curve is standardized.
2.4 Control sample method: due to the difference in the metallurgical process and physical state of the analysis sample and the spectral standard sample of the working curve, the analysis result deviates from the actual content. In daily analysis, the control sample and the sample are simultaneously analyzed, and the analysis value of the sample is corrected by the analysis value of the control sample to obtain the analysis result of the sample.
2.5 Standard samples: Standard samples require uniform texture, stability, and accurate chemical composition. Spectral standards are the certified reference materials needed to draw calibration curves for daily analysis. The content of each analytical element in the selected standard sample must have an appropriate gradient.
2.6 Recalibration sample (standardized sample): The measurement result deviates due to the change in the state of the instrument. To directly use the original calibration curve to find an accurate result, use this sample to standardize the instrument and restore the system to the original working curve state. The standardized sample should be close to the standard material with good uniformity. The single-point standardized element content is selected near the upper limit of the calibration curve; the two-point standardized element content is selected near the upper and lower limits of the calibration curve, respectively.
2.7 Control sample: Control sample refers to the internal standard sample obtained from daily production analysis, which has the same material as the sample, basically the same smelting and rolling process, and has accurate chemical composition. Use the control sample to correct the analysis value of the sample.
3. Sampling and sample preparation
3.1 Steel-making smelting samples should be sampled and cast in an even part of the molten steel, cast into a cylinder with Î¦ 40 mm above, Î¦ 30 mm below, and a height of 60-70 mm. Before casting, aluminum deoxidation should be added to the sample spoon, and the amount of aluminum added should be less than 0.30%. The cast samples should be free of pores, inclusions and cracks. Ordinary carbon steel and low alloy steel can be quenched by water cooling, while medium, high carbon and medium and high alloy steel can only be cooled slowly. To analyze the aluminum content in the sample, aluminum cannot be added during casting.
3.2 Steel sampling should be selected at representative locations. The diameter of the round bar sample should be above 5.0mm and the length should be 120-140mm. The diameter of the sheet sample is greater than 16mm, the length direction is more than 60mm, and the thickness is greater than 3mm.
3.3 Preparation of casting samples should be taken at the lower third of the sample to obtain a sample with a diameter of 30 to 35 mm and a height of less than 30 mm. The excitation surface of the sample is smoothed and polished with a grinding wheel or sandpaper with a particle size of 24 to 60 mesh.
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