Measuring the ball milling toughness of white fused alumina (WFA) is standardized by national/international protocols, focusing on quantifying its resistance to fragmentation during ball milling. Here’s a step-by-step guide based on core standards like GB/T 2479-2022 (China) and relevant industrial practices:
1. Core Test Standard & Principle
- Reference Standard: Primarily GB/T 2479-2022 Abrasive—White Fused Alumina (China) or ISO 10426-1 (international for abrasive testing).
- Test Principle: Grind a fixed mass of WFA sample in a ball mill for a specified time. The ball milling toughness is evaluated by the mass ratio of “unbroken coarse particles” remaining after milling—higher ratios indicate better toughness.
2. Key Equipment & Materials
- Ball mill: Horizontal ball mill with adjustable speed (standard speed: 60 r/min).
- Milling jar: Wear-resistant steel jar (volume typically 500–1000 mL).
- Grinding media: Steel balls (e.g., 10 mm diameter, total mass matching sample requirements).
- Standard sieves: Specified mesh size (e.g., 40–60 mesh, equivalent to 0.25–0.45 mm) for sample pre-screening and post-milling classification.
- Analytical balance: Precision ≥ 0.01 g for mass measurement.
- Drying oven: To dry samples (if needed) and remove moisture before testing.
3. Step-by-Step Test Procedure
- Sample Preparation
- Weigh 50 g of white fused alumina as the raw sample (mass recorded as \(m_0\)).
- Screen the sample with a 40–60 mesh standard sieve, discard undersized fine powder, and retain only the 40–60 mesh coarse particles (ensure uniform particle size to avoid bias).
- Dry the screened sample at 105±5°C for 2 hours, then cool to room temperature in a desiccator.
- Ball Mill Setup
- Place the dried sample into the milling jar.
- Add steel balls (e.g., 10 pieces of 10 mm diameter steel balls, total mass ~200 g—follow standard requirements for ball-to-sample ratio).
- Secure the milling jar to the ball mill, set the rotation speed to 60 r/min, and set the milling time to 30 minutes (fixed parameters per standard).
- Post-Milling Treatment
- After milling, carefully empty the entire contents of the jar into a clean container.
- Use the same 40–60 mesh standard sieve to sieve the milled mixture, gently tapping the sieve to separate fine powder from unbroken coarse particles.
- Collect all particles remaining on the sieve (unbroken coarse particles) and transfer them to a weighing dish.
- Result Calculation
- Weigh the mass of the unbroken coarse particles (recorded as \(m_1\)).
- Calculate the ball milling toughness index (T) using the formula:\(T = \frac{m_1}{m_0} \times 100\%\)
(e.g., if \(m_1 = 35\) g, \(T = 70\%\)—higher T means better toughness).
4. Critical Notes for Accuracy
- Ensure consistent equipment parameters (speed, ball size/quantity, milling time) across tests—any deviation will affect result comparability.
- Avoid sample contamination: Clean the milling jar, sieve, and weighing tools thoroughly before each test.
- Repeat the test 2–3 times with parallel samples, take the average value as the final result (reduce random errors).
- For samples with different initial particle sizes, adjust the sieve mesh size per standard to match the particle range (e.g., 60–80 mesh for finer raw materials).
