Overview
EN ISO 13944:2012 (published by CEN/ISO) specifies a standardized Soxhlet extraction method for determining the lubricant content of lubricated metal‑powder mixes. The method removes organic lubricants from powder samples so lubricant percentage can be measured and so that downstream analyses (for example, graphite or oxygen determinations) are not interfered with by residual lubricant. A prerequisite is that a suitable solvent for the lubricant is known and available.
Key topics and requirements
- Principle: extract the lubricant from a weighed test portion with an appropriate solvent; reweigh and calculate percentage mass loss.
- Equipment: Soxhlet extractor (150–200 ml), Allihn condenser, sintered‑glass filter crucible (porosity grade P160), round‑bottom flask (≈500 ml), heating mantle (evaporation ≥25 ml/min). An automated Soxhlet system may be used as an alternative.
- Solvent: must be compatible with the lubricant; examples include xylene, toluene and petroleum ether. Warning: organic solvent vapours can be hazardous.
- Test portions: two replicate portions per determination - typically ≈50 g if lubricant ≤2% or ≈25 g if >2%.
- Extraction time: establish by preliminary test; generally less than 30 minutes. Example: 0.8% zinc stearate with toluene required ~10–20 min.
- Calculation: lubricant content (%) = (m2 − m3) / (m2 − m1) × 100, where:
- m1 = mass of crucible + filter paper + glass wool,
- m2 = mass before extraction (crucible + filter + test portion + glass wool),
- m3 = mass after extraction (crucible + contents).
- Accuracy and reporting: maximum allowable difference between replicates is 0.10% (m/m). Report the arithmetic mean rounded to the nearest 0.05% (m/m). Test report must list solvent used, extraction time and any deviations.
Applications
- Quality control in powder metallurgy and metal‑powder production to verify lubricant dosing.
- Sample preparation for elemental analyses (e.g., carbon/graphite or oxygen determinations) where lubricants would interfere.
- Process development and R&D for powder‑based components (pressing/sintering) to ensure consistent powder flow and compacting behavior.
- Compliance testing and supplier verification of lubricated metal powders.
Who should use this standard
- Materials testing laboratories and QC/QA teams in powder metallurgy and metal‑powder manufacturing.
- Engineers and technicians performing sample preparation for elemental analysis.
- R&D teams optimizing lubricant formulations and process parameters.
Related standards
- ISO 4491 series (methods for oxygen determination in metallic powders) - referenced for post‑extraction elemental testing.
- EN ISO 13944:2012 supersedes earlier editions (e.g., EN ISO 13944:2006).
Keywords: EN ISO 13944:2012, Soxhlet extraction, lubricated metal‑powder mixes, lubricant content determination, powder metallurgy, solvent extraction, sample preparation, graphite determination, oxygen determination.