Overview
ISO 4829-2:2016 - Steels - Determination of total silicon contents - Reduced molybdosilicate spectrophotometric method - Part 2: Silicon contents between 0,01 % and 0,05 % defines a chemical test method for measuring low levels of total silicon in steels. The procedure uses a reduced molybdosilicate color reaction and spectrophotometric measurement to determine silicon mass fractions in the range 0,01 % to 0,05 %.
This standard is intended for laboratory quality control and compositional analysis where accurate determination of low silicon content is required.
Key topics and technical requirements
- Analytical principle: Dissolve the steel sample in hydrochloric/nitric acid, fuse the acid-insoluble residue with sodium peroxide, form an oxidized molybdosilicate complex and selectively reduce it with ascorbic acid to produce a blue complex measured spectrophotometrically (about 810 nm).
- Measurement: Absorbance measured at ~810 nm using a 4 cm optical path cell. Spectrophotometer spectral bandwidth ≤10 nm; wavelength accuracy ±2 nm; repeatability of max-absorbance measurement ≈ ±0,3 % (relative).
- Reagents and contamination control: Use analytical-grade reagents and grade 2 water (ISO 3696). Avoid ion-exchange demineralized water due to colloidal silica risk. Freshly prepare solutions and use polypropylene/PTFE containers to reduce contamination.
- Interference control: Oxalic acid is added to suppress interferences from phosphorus, arsenic and vanadium; potassium permanganate and hydrogen peroxide steps control organic/manganese interferences.
- Quality checks: Run duplicate blanks in parallel (using low-silicon pure iron) and monitor blank absorbance - recommended blank absorbance not to exceed 0,050 (equivalent to ~0,008 % Si with a 4 cm cell).
- Sample size & sampling: Typical test portion is 0,50 ± 0,01 g of fine chips/turnings/filings. Sampling and sample preparation follow ISO 14284.
Practical applications and users
- Steel manufacturing and processing plants for quality control (ensuring alloying and deoxidation targets).
- Metallurgical laboratories and third‑party testing labs performing chemical composition analysis of steels.
- R&D and failure‑analysis teams needing accurate low‑level silicon quantification.
- Certification bodies and suppliers verifying compliance with material specifications.
Related standards
- ISO 4829-1 - Part 1 covers silicon contents between 0,05 % and 1,0 %.
- ISO 14284 - Sampling and preparation of samples for chemical composition.
- ISO 3696 - Water for analytical laboratory use.
- ISO 385, ISO 648, ISO 1042 - Laboratory glassware specifications used in the method.
Keywords: ISO 4829-2:2016, steels, total silicon determination, reduced molybdosilicate spectrophotometric method, silicon 0.01–0.05%, spectrophotometry, steel quality control.
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