As we covered in Part 1, copper mould tube curvature is key to compensating steel shrinkage and regulating friction. Beyond these, it also extends tube life and stabilizes the whole casting system—here’s how.

1. Reduces Stress to Lengthen Tube Life

Copper mould tubes (lasting 300–1,500 casts) fail mostly from wear or cracking, often due to curve flaws:

• Local curve deviations (±0.2mm+ bulges/dents) create uneven billet contact, generating repeated impact stress. This speeds up wear by 2–3x and cuts tube life by 20–30%.

• Unbalanced stress also harms billets: Tube bulges push too hard on hot steel (weak at 1,100°C+), causing hidden cracks—over 60% become scrap during rolling.

Keeping curvature within ±0.1mm (industry standard) distributes stress evenly. This slows wear by 40%, extends tube life by 20%, and drops billet cracks below 0.5%.

Inspector Tip: Check the “stress zone” (200–300mm from tube bottom) for wear. If wall thickness is 20% thinner than new, discard the tube. Keep records for 2+ years for audits.

2. Works with Taper to Stabilize Production

Curve (compensates lengthwise shrinkage) and “taper” (tube narrows top-to-bottom, compensates widthwise shrinkage) work together:

• Taper specs: 0.5–1.0%/m for square billets; 0.8–1.5%/m for slabs.

• Mismatch risk: Wrong curve-taper pairing causes uneven contact (gaps + tight spots), leading to uneven heat transfer or jams.

Tune curve with taper, casting speed, and molten steel temp (15–30°C above melting point). Test new pairs with 10 trial casts first.

Engineer Tip: Speeding up production? Increase curve slightly (0.1–0.2mm/m) to match faster cooling.

Final Recap

The curve’s full value:

• Quality: <0.3% surface defects, even steel structure;

• Efficiency: 99.8% casting continuity, 95%+ tube uptime;

• Cost: 15–20% lower tube costs, <0.5% scrap.

Use a laser profiler (±0.02mm accuracy) to check curves. Replace tubes if deviations exceed 0.2mm.

Quick Daily Checklist

1. Pre-cast: Confirm curve matches steel grade + taper;

1. During cast: Alert if pulling force spikes;
2. Post-cast: Log defects linked to curve;
3. Weekly: Calibrate curve and save data.