Overview
ISO 20202:2004 specifies a standardized laboratory method for preparing and baking green test specimens made from cold and tepid carbonaceous ramming pastes used in aluminium production, and for determining their loss on baking (relative mass loss). The standard defines the baking program, required apparatus and measurement accuracy, and the way to report and express results for consistent quality control and comparative testing.
Key topics and requirements
- Scope: Preparation of baked test pieces from compacted ramming pastes and determination of mass loss after baking for subsequent property tests (e.g., apparent density, crushing strength, porosity).
- Apparatus:
- Balance accurate to 0.1 g.
- Electrically heated muffle or chamber furnace with temperature control.
- Baking container with cover made of heat‑resistant steel (example: X15CrNiSi2521), with at least 10 mm spacing between specimens and container walls.
- Packing material: electrographite or calcined petroleum coke, maximum particle size 1 mm.
- Temperature‑measuring device (thermocouple type K or S) capable of ±5 °C accuracy up to 1 000 °C, calibrated per ASTM E 220.
- Baking program:
- Heat from room temperature to 500 °C at 35 ± 5 °C·h−1.
- Continue from 500 °C to 1 000 °C at 100 ± 10 °C·h−1.
- Hold at 1 000 ± 10 °C for 2 hours, then cool to room temperature.
- Measurement & calculation: Measure specimen mass before and after baking to 0.1 g. Calculate loss on baking as the relative mass loss: (mass before − mass after) / mass before × 100%, rounded to the nearest 0.1 % (absolute).
- Precision: Repeatability r = 0.9 % (absolute); reproducibility R = 2.3 % (absolute). Variability of materials influences precision.
- Reporting: Test reports must reference ISO 20202, identify the sample, record specimen preparation temperature, results (loss on baking), test date, and note any unusual features or deviations.
Practical applications
- Routine quality control of cold/tepid ramming pastes in aluminium smelters and refractory manufacturing.
- Preparation of standardized baked specimens for downstream tests (apparent density, crushing strength, porosity) used in product development and acceptance testing.
- Comparative evaluation of raw materials, paste formulations and baking behavior for process optimization and failure investigation.
Who should use this standard
- Materials and metallurgical laboratories in the aluminium industry
- QA/QC engineers at smelters and foundries
- Refractory manufacturers and suppliers of carbonaceous ramming pastes
- Research organizations studying refractory performance and paste formulations
Related standards
- ISO 14422 (sampling of cold‑ramming pastes)
- ISO 14427 (preparation of unbaked specimens and apparent density)
- ISO 4955 (heat‑resisting steels)
- ISO 5725‑2 (precision of measurement methods)
- ASTM E 220 (thermocouple calibration)
Keywords: ISO 20202:2004, loss on baking, carbonaceous materials, cold ramming pastes, aluminium production, baked test specimens, ramming paste testing.