Nickel and nickel alloy strips for vacuum devices
Nickel and nickel alloy ribbon for vacuum devices is a thin ribbon material used as electrodes, leads, or shielding components in devices such as vacuum tubes, kinescopes, and vacuum capacitors. Leveraging the high electrical and thermal conductivity, low vapor pressure, and excellent high-temperature stability of nickel and nickel alloys, it enables current transmission and signal shielding in high-vacuum environments. Its thickness typically ranges from 0.01 to 0.5 mm, and its width ranges from 5 to 200 mm. Materials primarily include pure nickel ribbon (N4, N6), nickel-iron alloy ribbon (Permalloy), and nickel-chromium alloy ribbon (Inconel 718). Pure nickel ribbon is suitable for general vacuum applications, while alloy ribbon is used in applications requiring magnetic shielding or high-temperature oxidation resistance.
The production of nickel and nickel alloy strips for vacuum devices requires precision processes including vacuum melting, ingot casting, hot rolling, cold rolling, bright annealing, and finishing. First, high-purity nickel plates (≥ 99.95% ) or alloy raw materials are melted in a vacuum induction furnace at a vacuum of ≤ 5×10⁻⁴Pa and a melting temperature of 1400-1500 °C. Fine-tuning the composition ensures that the nickel content of the pure nickel strip is ≥ 99.5% , and that the tolerance of key elements (such as iron and chromium) in the alloy strip is ≤ ± 0.05% . The ingots are then cast using a vacuum consumable remelting process, resulting in flat ingots 50-100mm thick . This process reduces gas and inclusions, keeping the oxygen content below 0.003% . Hot rolling heats the ingot to 900-1100 °C and then undergoes multiple hot rolling passes to a strip thickness of 2-5mm. The reduction and cooling rate are controlled during rolling to avoid scale and cracking. Cold rolling is the core process for producing ultra-thin strip. This process is performed using a multi-roll mill (such as a 20-roll Sendzimir mill) with a reduction of 15%-25% per pass at a speed of 50-100m/min. Rolling oil (such as alkyl salicylate) is used for lubrication and cooling, ensuring a thickness tolerance of ≤±0.001mm, a width tolerance of ±0.1mm, and a surface roughness Ra ≤0.02μm (mirror grade). Bright annealing is performed under hydrogen protection. Pure nickel strips are heated to 650-750°C, and alloy strips are heated to 800-950°C. After holding for 0.5-1 hour, they are rapidly cooled to reduce the strip hardness to HV70-100 and achieve an elongation of 35% or more, meeting the requirements of subsequent stamping and forming. Finally, the strips are slitting, cleaning, and packaging to ensure that the surface is free of oil stains and scratches.
The performance advantages of nickel and nickel alloy strips for vacuum devices make them irreplaceable in the vacuum field. First, they have excellent vacuum performance. Nickel and nickel alloys have extremely low vapor pressure at high temperatures ( the vapor pressure of pure nickel at 1000 °C is ≤ 5×10⁻⁵Pa ). In a high vacuum environment of 1×10⁻⁷Pa , they release almost no gas, thus avoiding contamination of the vacuum cavity and ensuring the service life of electronic devices. Second, they have excellent electrical and thermal conductivity. The electrical conductivity of pure nickel strip is ≥ 22% IACS and the thermal conductivity is ≥ 70W/(m・K) . They can quickly conduct the heat generated by the electrodes and prevent local overheating. Third, they have good high-temperature strength. The tensile strength of Inconel 718 alloy strip remains ≥ 800MPa at 650 °C , which can withstand the thermal stress of vacuum devices during operation and avoid deformation. Fourth, they have excellent formability. The elongation of annealed nickel strip is ≥ 35%. , it can be made into electrodes or shielding covers of complex shapes through stamping, bending and other processes, and the minimum bending radius can reach 1 times the thickness of the strip; fifthly, special functional characteristics, the magnetic permeability of Permalloy strip is ≥ 8000μ₀ , which is suitable for magnetic shielding components of vacuum devices to reduce external magnetic field interference; the oxidation resistance temperature of NiCr alloy strip can reach 1200 ℃, which is suitable for heating elements of high-temperature vacuum furnaces.
Nickel and nickel alloy ribbons for vacuum devices are key materials for a variety of high-end electronic devices. In broadcasting and television, the shadow masks and electron gun electrodes of color picture tubes utilize 0.05-0.1mm thick pure nickel ribbon, leveraging its excellent formability and low magnetic properties to ensure image clarity. In microwave communications, the collectors and couplers of klystron tubes utilize Inconel 718 alloy ribbon, 0.1-0.3mm thick, designed to withstand temperatures exceeding 600°C and high-frequency electric fields. In medical equipment, the anode target connection ribbons of CT machines utilize pure nickel ribbon, ensuring high thermal conductivity and vacuum tightness. In semiconductor manufacturing, the vacuum valve sealing tape of ion implanters utilizes ultra-thin 0.01-0.05mm pure nickel ribbon for high-precision sealing. In aerospace, traveling wave tubes in satellite communications utilize Permalloy ribbon, 0.1-0.2mm thick, for magnetic shielding, achieving a shielding effectiveness of ≥80dB, ensuring signal transmission quality. With the development of 5G communications and space exploration technology, the performance requirements for nickel and nickel alloy strips are becoming increasingly stringent.
Industry trends indicate that nickel and nickel alloy ribbons for vacuum devices are moving toward ultra-thinness, ultra-high purity, and functional integration. Breakthroughs in ultra-thin ribbon production technology have enabled the stable production of pure nickel ribbon as thin as 0.005mm , suitable for micro vacuum sensors. Ultra-high-purity nickel ribbon (nickel content ≥ 99.99% ), produced through zone melting technology, has an impurity content ≤ 10ppm , further reducing its vapor pressure and meeting the requirements of ultra-high vacuum ( 1×10⁻¹⁰Pa ) devices. Functional composite ribbons (such as nickel – copper composite ribbons and nickel – ceramic coated ribbons) integrate electrical and thermal insulation, expanding their application scenarios. Furthermore, precision rolling technology upgrades, employing online thickness monitoring and shape control, have achieved thickness tolerances within ±0.0005mm . Green production processes are being promoted, using biodegradable rolling oil and hydrogen recovery systems to reduce environmental impact. In the future, with the development of fields such as quantum communication and deep space exploration, the demand for nickel and nickel alloy strips for high-performance vacuum devices will continue to grow, driving the industry to make greater breakthroughs in material purification, precision processing and performance optimization.
