Overview
ISO 4490:2018 - Metallic powders - Determination of flow rate by means of a calibrated funnel (Hall flowmeter) specifies a standardized laboratory method to measure the flowability of freely flowing metallic powders. The test measures the time required for 50 g of powder to pass through a calibrated funnel (Hall flowmeter) and is intended for powders used in powder metallurgy, including powders for hard metals.
Key topics and requirements
- Principle: Measure elapsed time for 50 g ±0.1 g of powder to flow through a standardized orifice; report results as seconds per 50 g (s/50 g).
- Apparatus:
- Calibrated funnel (Hall flowmeter) made from non‑magnetic, corrosion‑resistant metal with standardized dimensions.
- Rigid stand and vibration‑free base.
- Balance with accuracy ±0.05 g and timing device with accuracy ±0.1 s.
- Reference grit for calibration (specified in the standard).
- Calibration:
- Manufacturer calibration procedure yielding an average reference flow stamped on the funnel; reference target is 40.0 s ±0.5 s for the reference grit.
- User verification recommended; if measured flow differs, a correction factor = 40.0 / measured_value is applied. Funnels should be retired if reference flow falls below 37 s.
- Sampling and test portions:
- Test sample mass ≥ 200 g; perform three determinations on 50 g portions.
- Powder usually tested as‑received; drying only by agreement (vacuum/inert gas if oxidation risk).
- Procedure and reporting:
- Start timing when orifice opens and stop when last powder exits; a single slight tap to start flow is permitted.
- Report arithmetic mean of three runs, rounded to the nearest second; note any optional steps (e.g., drying, tapping).
- Precision:
- Inter‑laboratory data indicate reproducibility on the order of ~3 s for powders tested (values vary by powder type).
Applications and who uses it
- Quality control in powder production for metal injection molding, pressing and sintering, and hard‑metal manufacture.
- Incoming inspection for powder suppliers and buyers to verify flowability specifications.
- R&D and process development teams assessing powder handling, feeding, and die filling characteristics.
- Independent testing laboratories performing standardized powder characterization for certification or procurement.
Keywords: ISO 4490:2018, metallic powders, flow rate, Hall flowmeter, calibrated funnel, powder flowability, powder metallurgy, testing method, calibration, precision.
Related standards
- ISO 5725‑2 - Accuracy (trueness and precision) of measurement methods and results (referenced for the precision statement in ISO 4490:2018).