Crucible blank requirements. The crucible must be pre-treated before use, and the appropriate baking temperature and time should be controlled. It is generally recommended to bake in a muffle furnace at 1100 ° C for 4 hours, so as to minimize the effect of the crucible blank on the stability of the analysis results.
Another factor that affects the stability of the analysis result is the quality and amount of the flux. The flux is selected from the blank stable, tungsten particle flux for carbon and sulfur analyzer. The effect of the amount of flux added is very prominent when analyzing low-content samples. For example, when analyzing samples with a carbon and sulfur mass fraction of less than 15μg / g, add 1.5g and 2g flux (carbon and sulfur mass fractions in the flux are ≤8μg / g and ≤5μg / g, respectively), because the amount of flux is usually It is not involved in the calculation of the analysis results, so the fluctuation of the carbon and sulfur content in 0.5g of flux was introduced between the two analyses. It is assumed that the content of carbon and sulfur in the flux is 3 μg / g, and the sample weighs 0.5 g. Due to the different amounts of flux added, a deviation of 3 μg / g is introduced. Therefore, when analyzing low-content samples, try to ensure that the amount of flux is consistent, so as to reduce the uncertainties introduced by the flux.
Different samples weigh different amounts of C and S contained in the sample, resulting in different areas where the analysis results fall on the calibration curve of the instrument. Due to the limitation of the linear range of the instrument, this difference in the calibration area will cause fluctuations in the analysis results, especially when the upper and lower limits of the analytical instrument are near.
For low-content samples, higher results are obtained when the sample is weighed larger. For high-content samples, the situation is reversed and results are lower.
In addition, the difference in sample weighing directly affects high frequency induction combustion. The combustion temperature and state of the carbon-sulfur meter are not only related to the power of the high-frequency furnace itself, but also to the amount of magnetically-removed material that is induced internally. The combustion temperature is not continuously constant. As the substance melts and burns, the amount of induction gradually decreases. For instruments from different manufacturers, the linear range and calibration curve characteristics are different, and the implementation method of the high-frequency control part is different. Therefore, the influence of the sample weighing on the accuracy and reliability of the analysis results is different. For specific instruments. You need to be familiar with its characteristics through a large number of experiments, and choose an appropriate weighing sample to avoid the impact as much as possible.
4.Sampling order of samples and flux
The influence of the stacking order of samples and fluxes on the stability of sample analysis results can not be ignored. During the analysis, the stacking order of samples and fluxes directly affects the combustion results and analysis stability. The co-solvent not only has the effect of increasing the magnetically conductive substance in the sample and the combustion temperature, but also has the effect of increasing the fluidity of the sample and diluting the sample. The sample was placed on the bottom layer and tungsten particles were placed on the upper layer. After the analysis, the quartz tube in the combustion chamber was very clean, and there was no metal melt splash on the ceramic thermal protective sleeve, and the analysis result was stable. For example, iron-based samples are combusted by high-frequency induction directly under oxygen, which is reflected violently and splashes severely after melting, which may easily cause damage to the quartz tube of the combustion chamber and pollution of the ceramic protective sleeve. Replaced with tungsten particles as the base, and the sample was placed on the upper layer. It was found that the quartz tube industry in the combustion chamber was quickly contaminated. A thick layer of iron melt was stuck on the ceramic protective sleeve, which was difficult to clean, which not only affected the combustion tube. The service life also hinders the supply of oxygen, which directly affects the stability of the analysis results.
There are many factors affecting the stability of the analysis results of carbon and sulfur analyzers. During the analysis, especially when analyzing low-content samples, the influence of these factors can be considered comprehensively, so that the analysis results can be accurately evaluated. Avoids affecting the analysis results and progress due to incorrect estimation of the problem and increasing the maintenance cost of the instrument.