In continuous casting at steel plants, copper mould tubes serve as the "key channel" for cooling molten steel into billets. They endure extreme conditions—high temperatures, mechanical wear, and chemical corrosion—yet premature failure can disrupt production and drive-up costs. Most of this early failure traces back to neglecting three critical pre-service tasks. This first part focuses on two foundational steps: choosing the right material and controlling machining precision.

1. Choose the Right Material: Align with Casting Speed

The durability of copper mould tubes begins with material selection, which must match the billet pulling speed (casting speed) to avoid early damage:

-Medium-speed casting (1.2–2.0 m/min): Opt for silver-containing copper tubes (Cu-Ag alloy, 0.03%–0.1% Ag). Compared to pure copper, they deliver 30% higher strength and 2–3 times better resistance to high-temperature cracking, extending service life from 300–350 heats to 500–550 heats.

-High-speed or challenging casting (≥2.0 m/min, e.g., stainless steel or high-carbon steel): Use Cu-Cr-Zr alloy tubes. With a room-temperature strength of 400–450 MPa (80% retained at 300°C), they cut crack rates from 32% (pure copper) to 12% and extend service life from over 200 heats to over 800 heats.

-Ultra-high-speed or stick-prone casting (≥3.0 m/min, e.g., bearing steel): Select nanoparticle-reinforced copper tubes (Cu-Al₂O₃). These offer the highest strength but cost 1.8–2.2 times more than Cu-Cr-Zr alloy, making them suitable only for extreme applications.

Crucially: Keep harmful impurities (Pb, Bi, S) in materials to ≤0.005% (total impurities ≤0.01%)—these weaken tubes under high temperatures.

2. Control Machining Precision: Avoid Small Flaws

Even with the right material, machining flaws speed up wear. Focus on three key areas:

-Inner wall quality: Ensure a mirror-like finish (Ra ≤ 0.4 μm) to prevent molten steel from sticking. Adjust taper based on steel type—0.8%–1.2% per meter for plain carbon steel and 1.0%–1.5% per meter for stainless steel—to match steel shrinkage.

-Thickness uniformity: Maintain an overall thickness deviation of ≤0.1 mm, especially in the "meniscus area" (the 200–300 mm section where molten steel first contacts the tube). The "cold drawing + precision boring" process raises qualification rates from 82% to 98%.

-Tube end treatment: Grind R2–R3 mm arcs on both ends to avoid stress concentration. Keep flange surfaces flat (flatness ≤0.05 mm) to prevent water leakage—leaks cause local temperature spikes (50–100°C) and deformation failure.

What’s Next in Part 2?

Material selection and machining precision lay the groundwork for durable copper mould tubes, but the final pre-service step—proper installation—equally shapes their performance. In Part 2, we’ll dive into installation precision (including central alignment, cooling circuit sealing, and foot roller coordination) and summarize how these three foundational steps work together. We’ll also preview in-service maintenance tips to further extend tube life.