Overview
ISO 18515:2014 specifies a standardized method for determining the compressive strength of solid carbon and graphite materials used in aluminium production - specifically cathode blocks and baked anodes. The procedure applies at room temperature (10 °C to 35 °C) and defines specimen geometry, test apparatus, test procedure, calculation, precision and reporting requirements for consistent measurement of compressive strength (expressed in MPa).
Key topics and requirements
- Scope: Compressive strength test method for carbonaceous materials used in aluminium production (cathode blocks and prebaked anodes).
- Specimens: Cylindrical or cubic specimens with plane-parallel end planes. Minimum dimension rules:
- Smallest dimension ≥ three times the diameter of the largest structural constituent, and not less than 5 mm.
- For cylinders: height = diameter (isometrical cylinders). For hollow cylinders: height = outer diameter.
- Sampling and preparation: Sampling per ISO 8007 series (parts 1–3) or by agreement with the applicant; number of specimens depends on material homogeneity.
- Apparatus:
- Compression testing machine meeting class 2 requirements of ISO 7500-1.
- Two pressure plates with cardanic suspension to ensure uniform load.
- Dimensional measuring device (e.g., vernier caliper per ISO 13385-1) with specified accuracy.
- Procedure:
- Test at room temperature (10 °C to 35 °C).
- Centre specimen and apply load uniformly and shock-free at about 5 mm/min until fracture.
- Record the maximum force (Fmax).
- Calculation: Compressive strength σdB = Fmax / A, where A is the initial cross-section (mm²). Results expressed in MPa, rounded to 0.1 MPa.
- Precision: Repeatability r = 5.7 MPa; reproducibility R = 9.8 MPa (95% confidence).
- Reporting: Report must reference ISO 18515:2014 and include specimen designation, dimensions, number of specimens, individual and mean compressive strength values, test date and any deviations.
Applications and who uses it
- Aluminium producers, materials laboratories, quality control teams, R&D departments and third‑party testing bodies use ISO 18515:2014 to:
- Verify mechanical integrity of cathode blocks and baked anodes.
- Compare material batches, support purchasing specifications, and ensure process control.
- Provide reproducible data for failure analysis and product development.
Related standards
Using ISO 18515:2014 ensures consistent, comparable compressive strength data for carbonaceous materials in aluminium production, supporting quality assurance and material specification compliance.