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Test of chemical composition for steel
- May 21, 2018 -

The chemical composition of steel is the basic condition to ensure the properties of steel pipe, and the accuracy of chemical composition analysis in smelting process is necessary for the smelting of high-quality steels. 

In general, the main elements of the analysis include C, Si, Mn, P, S, Cr, Mo, Ni, Cu, Al, W, V, Ti, as, Sn, B, NB and other components. 

(1) Chemical Analysis: the analytical method based on the chemical reaction of matter. 

(2) Instrumental Analysis: An analytical method based on physical and physicochemical properties of matter. 

(3) Error: Refers to the difference between the analysis result and the real value. 

According to its property, it can be divided into random error, systematic error and fault errore. (4) Random error: Also known as accidental tolerance. Due to a series of related factors in the measurement of small random fluctuations in the formation of a mutual compensation error, it determines the precision of the results of determination.

(5) System error: Refers to a certain test conditions by a certain factor in accordance with a certain rule of the formation of the error, in each determination will be repeated, so that the results of the measurement often high or low, it determines the accuracy of the determination results. 

The main sources are method error, instrument error, operation error and reagent error.

(6) Fault error: Refers to a clearly inconsistent with the facts of the error, there is no certain law. 

Regardless of the specific cause of fault error, in the analysis and testing process, as long as the existence of errors, the error must be measured as abnormal value, from a group of measured data. (7) Permissible difference in chemical analysis: in the actual analysis work, according to the standards or the competent departments in accordance with the requirements of production and science and technology development, taking into account the level of analysis technology can be achieved, and to formulate an element in what content range can be allowed to the error value. This allowed error range, customarily referred to as "tolerance", the implementation of GB/T 222 standard. 

The allowable difference stipulated in the method of chemical analysis is the quality standard to measure the result of analysis.