Overview
ISO 2738:1999 defines standardized test methods for determining density, oil content and open porosity of permeable sintered metal materials (excluding hardmetals). It applies in particular to porous metal bearings and structural parts made by pressing and sintering metal powders. The standard describes sample preparation, measurement procedures, calculation methods and reporting requirements to ensure consistent, comparable results in powder metallurgy testing.
Key topics and technical requirements
- Measured properties: dry density, fully impregnated (wet) density, oil content (V/V and as % of open porosity) and open porosity (V/V).
- Test sequence: initial mass → oil extraction (modified Soxhlet or equivalent) → drying and mass after extraction → full oil impregnation under vacuum → mass of impregnated piece → volume determination by hydrostatic weighing.
- Equipment: analytical balance (0.01% accuracy), Soxhlet extractor or equivalent solvent-extraction setup, vacuum impregnation apparatus, immersion/ weighing device for air and water, impregnation oil of known density, wetting agent for water.
- Volume determination: hydrostatic weighing in water (or other liquid of known density) after partial or full impregnation or surface coating to prevent water ingress. The standard includes methods for suspension and corrections for supports/wires and provides recommended test temperature (typically 18–22 °C) and water density references.
- Surface treatments: guidance on preventing water entry (petroleum jelly, silicones, paraffin wax) when partial impregnation is used for volume determination.
- Precision: for ferrous sintered parts the standard reports repeatability and reproducibility intervals - repeatability: 0.06 g/cm3 for density and 1.6 percentage points for porosity; reproducibility: 0.085 g/cm3 for density and 2.4 percentage points for porosity.
- Reporting: required items include reference to ISO 2738, sample identification, whether pieces were subdivided, methods used, oil density source, deviations or optional operations, and any occurrences affecting results.
Applications and users
ISO 2738 is used by:
- Quality-control and testing laboratories in the powder metallurgy and bearing industries
- Materials engineers and metallurgists characterizing porous sintered components
- R&D groups developing sintered filters, bearings, and other permeable metal components
- Suppliers and purchasers who need agreed measurement methods for contract testing and acceptance
Typical applications include verification of manufacturing consistency, validation of impregnation and lubrication processes, and specification compliance for porous bearing materials.
Related standards
- ISO 13944 - modified Soxhlet extraction method for lubricant content
- ISO 758 - density determination of liquids at 20 °C (used for oil density)
- ISO 3448 - viscosity classification (referenced for oil viscosity guidance)
Keywords: ISO 2738, sintered metal materials, permeable sintered metal materials, density measurement, oil content, open porosity, powder metallurgy testing, Soxhlet extraction, vacuum impregnation.
Open preview (PDF)Sintered metal materials, excluding hardmetals — Permeable sintered metal materials — Determination of density, oil content and open porosity