SIST EN ISO 4945:2019 PDF

Overview

EN ISO 4945:2018 - titled Steel - Determination of nitrogen - Spectrophotometric method (ISO 4945:2018) - is a CEN-endorsed international standard that specifies a laboratory spectrophotometric procedure for determining nitrogen in steel. The method covers nitrogen mass fractions from 0,0006 % to 0,050 % for low-alloy steels and 0,010 % to 0,050 % for high-alloy steels. It is not applicable to materials containing silicon nitrides or to steels with silicon content above 0,6 %.

Key Topics and Requirements

• Analytical principle: Dissolution of a test portion in hydrochloric acid; fuming of the acid-insoluble residue with sulphuric acid (and potassium sulfate and copper(II) sulfate); alkaline steam distillation to liberate ammonia; trapping ammonia in dilute sulphuric acid; formation of a blue-coloured phenol-based complex (with sodium hypochlorite and sodium nitroprusside); spectrophotometric measurement at about 640 nm.
• Applicable range: 0,0006–0,050 % N (low-alloy steels); 0,010–0,050 % N (high-alloy steels).
• Limitations: Excludes samples containing silicon nitrides or Si > 0,6 %.
• Reagents and preparations: Defines required reagent grades and preparations (e.g., HCl 1+1, fuming H2SO4, NaOH solutions, sodium phenoxide, sodium nitroprusside, standard nitrogen solutions).
• Apparatus: Requires class A volumetric glassware, a spectrophotometer capable of 640 nm readings with 10 mm cells, and a suitable steam distillation setup (examples provided in Annex A).
• Calibration and quality control: Procedure includes blank tests, preparation of calibration solutions from a nitrogen stock/standard, plotting a calibration curve and reporting results. Precision and interlaboratory data are documented in informative annexes.

Applications

• Quality control in steel production: Monitoring nitrogen content to meet material specifications and performance requirements (e.g., mechanical properties, welding behavior).
• Metallurgical laboratories: Routine chemical analysis of low- and high-alloy steels where accurate low-level nitrogen determination is required.
• Third‑party testing and certification: Use in conformity assessment, inspection and verification of delivered steel products.
• Research and development: Studies where controlled nitrogen levels influence microstructure or alloys’ properties.

Who should use this standard

• Steel producers and mills, heat‑treatment shops, analytical laboratories, metallurgists, quality engineers, and standards bodies responsible for chemical analysis of metals.

Related standards

• ISO 14284 - Sampling and preparation of samples for determination of chemical composition
• ISO 3696 - Water for analytical laboratory use
• ISO 648 and ISO 1042 - Laboratory glassware (pipettes, volumetric flasks)
• EN ISO 4945:2018 is the CEN-adopted version of ISO 4945:2018

Keywords: EN ISO 4945:2018, ISO 4945, nitrogen determination, spectrophotometric method, nitrogen in steel, steel analysis, CEN standard.