ISO 3923-1:2018

Overview

ISO 3923-1:2018 specifies the funnel method for determining the apparent density of metallic powders under standardized conditions. The method measures the bulk mass per unit volume (apparent density, g/cm³) of powders that flow freely through a 2.5 mm orifice, and can also be applied to powders that only flow through a 5.0 mm orifice. The standard defines equipment, sample preparation, test procedure, calculation, repeatability/reproducibility limits and reporting requirements for consistent apparent-density (bulk-density) testing in powder metallurgy.

Key topics and requirements

• Scope: Applies to metallic powders that pass through a 2.5 mm or, if required, a 5.0 mm orifice; powders that will not flow through 5.0 mm are covered by ISO 3923‑2.
• Permitted funnels:
  • Hall funnel: 2.5 mm orifice, 60° cone (ISO 4490)
  • Gustavsson funnel: 2.5 mm orifice, 30° cone (ISO 13517)
  • Carney funnel: 5.0 mm orifice, 60° cone (Annex A / ASTM B417)
• Apparatus & dimensions:
  • Cylindrical receiver capacity (25 ± 0.03) cm³; preferred internal diameter (28 ± 0.5) mm (30 ± 1 mm acceptable).
  • Funnel positioned (25 ± 0.5) mm above receiver rim and concentric.
  • Balance accuracy: ±0.01 g.
  • Apparatus made of non-magnetic, corrosion-resistant material with polished interiors.
• Sample & preparation:
  • Minimum sample volume: 100 cm³ (to allow three test runs).
  • Powder normally tested as received; if drying is needed and powder can oxidize, dry under vacuum or inert atmosphere. Do not dry powders containing volatiles.
• Procedure:
  • Pour powder through specified funnel into receiver until overflow, trim flush with a non-magnetic scraper in one pass (no compaction), tap to settle, weigh to ±0.01 g.
  • Perform three determinations.
• Result expression & fidelity:
  • Apparent density ρ = m / V (g/cm³). Report arithmetic mean of three results to 0.01 g/cm³.
  • Flag results if dispersion >1% of mean; repeatability threshold: 0.03 g/cm³ (same operator/equipment); reproducibility threshold: 0.05 g/cm³ (different labs) at 95% confidence.
• Reporting: Must include ISO reference, sample identification, drying method (if used), funnel/orifice/angle, use of any metal wire to initiate flow, results and any deviations/incidents.

Applications and users

• Who uses it: Powder metallurgy labs, quality control technicians, R&D teams, additive manufacturing (metal powder) suppliers and purchasers, and materials testing laboratories.
• Practical uses:
  • Characterizing powder bulk/apparent density for process control (pressing, sintering, powder feeding).
  • Comparing lot-to-lot consistency for metal powders used in additive manufacturing, cold/hot pressing, and thermal spray.
  • Specifying material properties for purchase agreements and quality records.

Related standards

• ISO 3923-2 - Apparent density by Scott volumeter (for non‑flowing powders)
• ISO 4490 - Hall funnel flow time
• ISO 13517 - Gustavsson funnel flow time
• ASTM B417 - Carney funnel dimensions

Keywords: ISO 3923-1:2018, metallic powders, apparent density, funnel method, Hall funnel, Gustavsson, Carney funnel, powder metallurgy, bulk density testing, powder flow.