Hot-Finished Process Technology Achieves Continuous Breakthroughs, Nickel-Based Alloy Seamless Pipe Manufacturing Advances Toward Precision

The manufacturing of hot-finished nickel-based alloy seamless pipes involves a complete process chain from melting, hot piercing/extrusion, to subsequent cold working and heat treatment. The melting stage generally employs a duplex process combining vacuum induction melting and electroslag remelting to achieve precise composition control and deep material purification. For high-alloyed grades such as N06690, hot working breakdown is typically performed at elevated temperatures between 1100 and 1200 degrees Celsius to break down the coarse as-cast structure and form a fine, uniformly distributed grain structure.

Hot extrusion technology is one of the core hot-working methods for producing nickel-based alloy seamless pipes. This process shapes heated billets into hollow shells through an extrusion press, which can then undergo cold working and heat treatment to precisely control final dimensions and properties. In terms of alloy grades, nickel-based alloy seamless pipes cover a diverse product range, including hot-finished seamless pipes under ASTM B423 for nickel-iron-chromium-molybdenum-copper alloys (UNS N08825, N08221, N06845) intended for general corrosive service, as well as nickel 201 low-carbon grade products meeting specific high-temperature requirements. ASTM B829, the general specification, provides a unified mandatory requirements framework for various nickel and nickel-alloy seamless pipes and tubes.

Substantial progress has also been achieved in academic research regarding process optimization for typical nickel-based alloy grades. A study on UNS N06625 alloy proposed an integrated preparation process covering cold rolling, intermediate heat treatment, and final heat treatment. By utilizing the time-insensitive characteristics of recrystallization grain growth, the process achieved intergranular corrosion rates below 0.5 mm/year through final heat treatment at 1150 to 1180 degrees Celsius, while maintaining excellent comprehensive mechanical properties. These technological breakthroughs provide a solid process foundation for the reliable application of hot-finished nickel-based alloy seamless pipes in high-end sectors such as nuclear power, chemical processing, and aerospace.