The Role Of Vacuum Induction Melting (VIM) in Pipe Processing

In pipe processing, vacuum induction melting (VIM) is a key link in the preparation of raw materials for high-end pipes such as nickel-based alloys and titanium alloys. By combining high-temperature melting with a vacuum environment, it can achieve multiple goals: first, it can precisely control the alloy composition. It melts metal raw materials by heating them with an electromagnetic field, accurately adds alloying elements, strictly controls the proportion of components (with an error of ≤0.05%), avoids impurities such as S and P (with a content of ≤0.001%), and ensures the uniformity of trace element addition; second, it can remove gases and volatile impurities. In a vacuum environment of ≤10⁻³ Pa, it effectively removes gases such as H₂, N₂, and O₂ (with H₂ ≤1ppm and O ≤50ppm) as well as low-melting-point impurities, preventing the formation of pores and cracks during hot processing of pipes, and reducing oxide inclusions to improve fatigue life; third, it can reduce secondary pollution. The closed vacuum environment isolates the influence of air and furnace lining materials, avoiding the formation of nitride and oxide inclusions; fourth, it lays a foundation for subsequent processing. It uses induction stirring to ensure the uniformity of the composition and temperature of the melt, reduces component segregation, refines the ingot grains (from the mm level to the μm level) by controlling the cooling rate, and improves hot working plasticity.