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.