Carbon silicon furnace analyzer
The carbon-silicon pre-fired analyzer is of great significance for the production of cast iron parts. When producing cast iron parts, the appropriate chemical composition is selected according to the wall thickness of the casting and the casting conditions to ensure the required mechanical properties. Carbon equivalent when other conditions are the same
(C+Si/3)
It has a decisive influence on the metallographic structure, casting properties and mechanical properties of cast iron.
Carbon-silicon furnace pre-analyzers and photoelectric direct-reading spectrometers are now widely used. The meaning of the accuracy of spectral quantitative analysis is described below.
Why quantitative analysis has the problem of accuracy, because quantitative analysis is a measurement, and as any measurement, there must be an error. Accuracy and error are actually two arguments for the same problem, the error is small, that is, the accuracy is high, the error is large, that is, the accuracy is low.
There are two ways to express the analysis error: one is absolute error; the other is relative error. We can distinguish between two kinds of errors from practical examples. For example, the content of chromium in tungsten or stainless steel in high speed steel is
18%
Left and right, the error in the analysis before the furnace is about
Is ±
0.20%
Absolute error is
±
0.20%
Usually
σ
Said that the relative error is (
±
σ/C onc
)×
100%
,among them
C onc
For the content. Therefore the relative error of the above example is (
±
0.2/18
)
×
100%
About
±
1.1%,
For example, analyzing the range of manganese content in carbon steel
0.17%-0.37%
Absolute error of analysis
±
0.005%
,Relative error
±
1.35%
. Another example is the analysis of the content of an element.
0.003%
Absolute error
±
0.0005%
,Relative error
16.6%
. These examples illustrate an inherent law of the spectrum analyzer that the relative error increases as the content decreases.
The deviation between the analytical result and the actual content is the error. The error of the analysis results can be derived from several aspects. In terms of spectral analysis, the distribution of the components of the standard sample and the analysis sample may be uneven, and the properties of the standard sample and the analysis sample are inconsistent, and the source light source may be unstable. It can be derived from the deviation of the spectroscopic system and the exit slit.
The causes of errors caused by normal operation and instrument working conditions can be classified into two categories: system error and accidental error (or random error). How do you distinguish between the two? The systematic error is biased to one side, or it is often too high, or often low. The nature of the standard sample and the analytical sample mentioned above are inconsistent, resulting in systematic errors in the analysis results. The use of consistent samples can eliminate such errors. Accidental errors are not biased toward one side, and positive and negative errors have similar opportunities. For example, the unevenness of the sample, the instability of the light source, etc., accidental errors cannot be eliminated, but measures can be taken to improve the conditions and can be reduced.
Therefore, the accuracy of the analysis includes two aspects, one is the correctness of the analysis, and the other is the reproducibility (repetition) of the analysis. The system error is small, the accuracy is high, the accidental error is small, and the reproducibility is high (repetitive). The systematic error is smaller than the accidental error, and the reproducibility (repetition or precision) is equal to the accuracy.
The carbon-silicon pre-fired analyzer is of great value for pre-furnace analysis of cast iron, and the photoelectric direct reading spectrometer is widely used due to various advantages. The above is an introduction to the accuracy of spectral quantitative analysis, and it is hoped that it will benefit everyone.
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