Overview
ISO 3995:2023 - Metallic powders - Determination of green strength by transverse rupture of rectangular compacts - defines a standardized laboratory method to measure the green strength of compacts pressed from metallic powders. The test determines transverse rupture strength by loading rectangular test pieces as simple beams on two supports and applying a central transverse load until fracture. This standard is essential for powder metallurgy quality control, material development and supplier–customer specification agreements.
Key topics and technical requirements
- Test principle: Break a rectangular compact under a uniformly increasing transverse force and calculate green strength from the flexure formula.
- Specimen geometry: Three specimens per test - width 10–13 mm, length ≥30 mm, thickness 5.5–6.5 mm; thickness uniformity within 0.1 mm between supports.
- Compacting: Green strength is reported at a specified compacting pressure or target density. Recommended compacting pressures are 400 N/mm² or 600 N/mm² (or mutually agreed values). When pressed to a target density, the three specimens must be within ±0.05 g/cm³ of the target.
- Apparatus tolerances:
- Press capable up to ~300 kN with ±2% accuracy; force increase rate ≤ 50 kN/s.
- Transverse rupture fixture: support and load rollers 3.0 mm ±0.1 mm diameter; span 25.0 mm ±0.2 mm or 25.4 mm ±0.2 mm.
- Breaking force determined to ±2 N; fracture duration not less than 10 s.
- Measuring instruments: balance to ±0.01 g; micrometer to ±0.01 mm.
- Lubrication options: die wall lubrication, admixed powder lubrication (e.g., 0.5–1.5% solid lubricant such as zinc stearate or synthetic wax), or combinations. Reporting of lubrication technique and details is mandatory.
- Procedure notes: die/punch cleaning, sample filling, pre‑compaction, final compaction and ejection (automated sequences allowed if rate controls are met).
- Results & reporting: calculate density and green strength (S) from test force and specimen dimensions; report arithmetic mean of three measurements and include test details - lubrication, die material, density/pressure, deviations, and any unusual occurrences.
Applications and users
- Who uses it: powder metallurgy labs, materials engineers, R&D teams, production quality control, and suppliers/clients specifying powder compaction performance.
- Applications: material development, process optimization (lubrication, compaction pressure), production acceptance testing, comparative evaluation of powder batches, and ensuring repeatable green strength for downstream handling and sintering.
Related standards
- This standard was prepared by ISO/TC 119 (Powder metallurgy). For comprehensive conformity, consult other ISO powder metallurgy test methods and guidance from ISO/TC 119 for sampling, density and sintered property standards.