EN ISO 4491-2:2023 PDF

Overview

EN ISO 4491-2:2023 - "Metallic powders - Determination of oxygen content by reduction methods - Part 2: Loss of mass on hydrogen reduction (hydrogen loss)" - specifies a laboratory method to measure the relative loss of mass a metallic powder undergoes when heated in a stream of pure, dry hydrogen under defined conditions. The test evaluates a chemical characteristic important to powder metallurgy and is not intended to quantify individual element contents. This third edition (2023) updates and supersedes earlier versions and includes a precision statement.

Key topics and technical requirements

• Scope and limitations
  • Applicable to unalloyed, partially alloyed and fully alloyed powders of the metals listed in the standard’s Table 1.
  • Not applicable to lubricated powders or to mixtures of metal powders.
  • Test is for characterizing powder behavior (hydrogen loss), not for element-specific analysis.
• Reagents and gases
  • Hydrogen: maximum oxygen 0.005% mass fraction; dew point ≤ −45 °C.
  • Nitrogen or argon (for purging/backing): same purity limits as hydrogen.
• Apparatus essentials
  • Laboratory balance capable of ±0.1 mg.
  • Electrically heated tubular furnace with temperature control for the sample zone.
  • Gas-tight tube (quartz or dense alumina), inside diameter 25–40 mm.
  • Totally enclosed thermocouple (e.g., Pt/Pt–Rh) with max error ±5 °C.
  • Sample boat (preferably high‑alumina ceramic); powder layer thickness ≤ 3 mm.
  • Gas supply unit with pressure gauges and flow meters.
• Sampling and procedure
  • Test powder in as-received condition.
  • Perform two determinations per test sample; typical test portion ~5 g (reduced for low apparent density powders).
  • Follow reduction temperatures/times from Table 1 (examples given: tin bronze 750 ±15 °C, 30 min; tin 425 ±10 °C, 30 min). Reduction times may be adapted per apparatus if proven sufficient.
• Results and reporting
  • Calculation expresses relative mass loss (hydrogen loss).
  • The standard includes guidance on interpretation (Annex A) and specifies precision data.

Applications and users

• Who uses it
  • Powder metallurgy laboratories, quality control/assurance teams, material suppliers, R&D groups developing powders and sintered components.
  • Industries: automotive, aerospace, tooling, additive manufacturing and any sector relying on controlled powder chemistry for sintering and performance.
• Why it matters
  • Hydrogen loss reflects oxide reduction and oxygen-related powder characteristics that affect sintering behavior, densification and final part properties.

Related standards

• ISO 4491 series (see ISO 4491-1 referenced for additional interpretation and element determination guidance).
• National adoptions: EN ISO 4491-2:2023 (CEN endorsement) - implementable as a national standard across CEN member bodies.

Keywords: EN ISO 4491-2:2023, metallic powders, hydrogen loss, loss of mass on hydrogen reduction, oxygen content determination, powder metallurgy, test method.