GB/T 223.5-2008 in English

《GB/T 223.5-2008钢铁 酸溶硅和全硅含量的测定 还原型硅钼酸盐分光光度法》由TC183（全国钢标准化技术委员会）归口，TC183SC5（全国钢标准化技术委员会钢铁及合金化学成份测定分会）执行，主管部门为中国钢铁工业协会。
GB/T 223的本部分修改采用ISO 4829-1：《钢和铸铁 全硅含量测定 还原型硅钼酸盐分光光度法 第1部分：硅含量0.05%~1.0%》和ISO 4829-2：1988《钢铁 全硅含量测定 还原型硅钼酸盐分光光度法 第2部：0.01%~0.05%》整合成一个标准。
GB/T 223的本部分规定了用还原型硅钼酸盐分光光度法测定钢铁中酸溶硅和全硅含量。
本部分适用于钢钢铁中质量分数为0.010%~1.00%的硅含量测定。
本标准代替GB/T 223.5-1997相比较，主要做了以下修改：
――扩大了适用范围；
――增加了全硅含量的测定方法；
――显色时用抗坏血酸作还原剂，原标准采用硫酸亚铁铵作还原剂。

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.

Contents
Foreword I
1 Scope
2 Normative References
3 Principles
4 Reagents and Materials
5 Instruments and Equipments
6 Sampling and Sample Preparation
7 Analysis Procedures
8 Expression of Results
9 Test Report
Appendix A (Informative) Additional Information for Internationally Common Test
Appendix B (Informative) Diagram of Precision Data