How to eliminate gas porosity in beryllium copper castings? The core lies in two key factors: vacuum melting degassing and the pouring temperature window.

1. Vacuum Melting: The First Line of Defense

Why Vacuum Is Non-Negotiable

Non-vacuum induction melting of BeCu causes severe beryllium oxidation and gas absorption, leading to porosity and slag inclusions. Ningxia Zhongse New Materials' retrofit case: switching to vacuum induction melting virtually eliminated porosity issues.

Our lesson (2022): A batch of electrode castings was poured after only 5 min settling post-vacuum melt. X-ray showed 2.5% porosity area — total scrap. Extending to 20 min dropped it to <0.5%.

2. Pouring Temperature: The Second Line of Defense

_{Higher Temp = More Porosity (Counter-Intuitive)}

We dropped temp from 1180°C to 1120°C and scrap fell from 8% to 3%. Higher temp = more gas absorption = more gas evolution during solidification.

The Sweet Spot

• Sand / investment casting: 1120–1150°C

• Semi-continuous ingot: 1100–1120°C

• Mold preheat: ≥500°C (reduces chill porosity)

• Ladle lip height: ≤150 mm (higher entrains air)

Control tips: Thermocouple monitoring with ±2°C accuracy; ladle lidded for heat retention; avoid extended open-air holding.

6. FAQ

Q: How low must vacuum be?<1 Pa is baseline; <0.1 Pa is better. Dropping from 10 Pa to 1 Pa cuts porosity defects ~40%.

Q: Can existing porosity be repaired?Surface pores: weldable with CuBe2 filler, then age. Internal minor pores: HIP (hot isostatic pressing) can close them. Severe pores: scrap. Prevention beats repair by 100×.

Q: What if we can't afford a vacuum furnace?Minimum viable: dry and preheat charge; charcoal cover to block water vapor; argon bottom-blow degas 15–20 min; settle ≥15 min; pour at 1120–1150°C. Gets scrap from 15% to ~5%.

One-sentence summary: Vacuum <1 Pa + rotary degas 20 min + settle 15 min + pour at 1120–1150°C = porosity scrap <2%

Based on 20 years of copper alloy casting experience. Questions welcome.