इन्वेस्टमेंट कास्टिंग में कोलॉइडल सिलिका: आयातकों के लिए व्यावहारिक मार्गदर्शिका

## Overview Colloidal silica is the most widely used binder in investment casting shell building. ## Grade selection | Grade | Particle Size | SiO₂ | pH | Primary Use | |-------|--------------|------|-----|-------------| | Standard alkaline | 8–12 nm | 30% | 9.5–10.5 | Primary slurry | | Fine particle | 5–8 nm | 30%–40% | 9.5–10.5 | Facing layers | | Large particle | 20–50 nm | 20%–30% | 9.0–10.0 | Backup layers | ## Slurry preparation checklist 1. Verify SiO₂ concentration — adjust to target (25%–30%) 2. Measure viscosity — target 20–40 seconds (Zahn cup #4) 3. Check pH — maintain 9.0–10.5 4. Add refractory flour gradually 5. Mix 30–60 minutes 6. Degas if needed 7. Test density (1.8–2.2 g/cm³)