As a core component of continuous casting equipment, copper mould tubes play a key role in molten steel solidification, shaping and heat transfer. Their performance directly determines continuous casting billet quality and production line stability. During service, they are continuously exposed to harsh conditions such as high temperature, high pressure, intense molten steel scouring and cyclic thermal shock, prone to failures. Below is an analysis of common issues and corresponding scientific selection strategies.

1. Wear Issues

Wear is a common failure mode of copper mould tubes, characterized by uneven or uniform inner wall thinning, increased surface roughness, and even grooves or step-like defects in severe cases. Main causes: high-temperature friction between the solidified billet shell and tube wall during billet pulling, scouring by hard impurities (undissolved alloy particles, refractory debris) in molten steel, as well as improper crystallizer vibration parameters and poor billet-tube lubrication that worsen wear. Selection strategies: Prioritize wear-resistant copper alloys (e.g., Cu-Cr-Zr), and tubes with surface strengthening treatments (hard chrome plating, electroless nickel-phosphorus plating) to enhance surface hardness and smoothness, reducing friction and wear loss.

2. Corrosion Failure

Corrosion failure of copper mould tubes includes chemical and electrochemical types, manifesting as surface pitting, local spalling or penetrating holes. These defects weaken tube strength, shorten service life, and pose cooling water leakage risks. Chemical corrosion results from reactions between active elements (oxygen, sulfur) in molten steel and tube surface copper atoms, and erosion by corrosive ions (chloride, sulfate) in unqualified cooling water. Electrochemical corrosion arises from microbattery formation due to material inhomogeneities and surface defects in cooling water electrolyte. Selection strategies: Choose corrosion-resistant alloys (tin-added, aluminum-added) to enhance corrosion resistance; select inner anti-corrosion coated tubes for poor water quality; ensure uniform material and defect-free surfaces to reduce corrosion initiation.

3. Thermal Fatigue Cracks

Thermal fatigue cracks are typical defects induced by cyclic thermal shock, appearing as fine vertical/horizontal cracks on tube inner and outer walls. With prolonged service, cracks expand and lead to fracture. Root cause: cyclic temperature changes (rapid heating by molten steel, rapid cooling by cooling water) cause alternating thermal expansion and contraction stresses in the tube, leading to local stress concentration and microcrack initiation/expansion. High-temperature gradient areas (e.g., water inlets/outlets) are high-risk zones. Selection strategies: Opt for thermal fatigue-resistant alloys (e.g., Cu-Ni-Si) with good toughness under cyclic thermal conditions; select tubes with uniform wall thickness and smooth transitions to reduce temperature gradients and stress concentration; use aging-strengthened tubes for high-temperature conditions to enhance stability and delay crack initiation.

4. Deformation Issues

Deformation of copper mould tubes includes abnormal inner diameter, taper deviation and bending, seriously impairing billet forming accuracy (irregular cross-sections, dimensional deviations) and exacerbating billet-tube friction, forming a vicious cycle. Causes: thermal stress from constrained high-temperature expansion, and mechanical stress from improper installation/disassembly impact or extrusion, or loose end fixings after long-term use. Selection strategies: Select high-strength, high-elastic-modulus alloys to enhance deformation resistance; match tube taper (parabolic, linear) and dimensional accuracy with mould jacket to reduce assembly constraints; prioritize high-precision, straight tubes and ensure end fixing compatibility to avoid mechanical deformation.

5. Conclusion

Common copper mould tube failures (wear, corrosion, thermal fatigue cracks, deformation) are closely related to working conditions, material properties and process parameters, impacting billet quality, reducing efficiency and increasing costs. Scientific selection is key to mitigating failure risks. Combined with standardized operations, strict cooling water control and regular inspections, it can effectively extend tube service life and ensure stable, efficient continuous casting.