WARNING: The personnel using this Part of GB/T 223 shall have practical experiences in regular laboratory work. This Part does not point out all the possible safety problems. Users have the responsibility to take appropriate safety and health measures and also ensure meeting the conditions specified in relevant regulations of the State.
1 Scope
This Part of GB/T 223 specifies the determination of acid-soluble silicon and total silicon content in steel and iron with reduced molybdosilicate spectrophotometric method.
This Part is applicable to the determination of silicon content, the mass fraction of which is 0.010 %~1.00% in steel and iron.
2 Normative References
The following standards contain provisions which, through reference in this part of GB/T 223, constitute provisions of this Part. For dated reference, subsequent amendments to (excluding correction to), or revisions of, any of these publications do not apply. However, the parties whose enter into agreement according to this Part are encouraged to research whether the latest editions of these references are applied or not. For undated references, the latest edition of the normative document is applicable to this Part.
GB/T 6379.1 “Accuracy(trueness and precision) of Measurement Methods and Results—Part 1: General Principles and Definitions” (GB/T 6379.12004; ISO 5725-1:1994, IDT)
GB/T 6379.2 "Accuracy (Trueness and Precision) of Measurement Methods and Results-Part 2: Basic Method for the Determination of Repeatability and Reproducibility of a Standard Measurement Method" (GB/T 6379.2-2004, ISO 5725-2:1994, IDT)
GB/T 20066 "Steel and Iron-Sampling and Preparation of Samples for the Determination of Chemical Composition" (GB/T 20066-2006, ISO 14284: 1996, IDT)
3 Principles
Dissolve the sample with sulfuric acid-nitric acid or hydrochloric acid-nitric acid in proper proportion and then fuse the acid insoluble residues with mix flux of sodium carbonate and boric acid. In weakly acidic solution, oxidized molybdosilicate (molybdosilicate yellow) is generated by silicic acid and molybdate. Increase the sulfuric acid concentration and add oxalic acid to eliminate the interference of phosphorus, arsenium and vanadium, ascorbic acid is adopted to carry out selective reduction and then molybdosilicate is reduced to blue reduced molybdosilicate (molybdosilicate blue).
At 810 nm wavelength, spectrophotometric determination is carried out for blue reduced molybdosilicate.
