4J29 seamless tubes are precision-engineered from the iron-nickel-cobalt alloy 4J29 (Kovar) to meet the ultra-fine, high-performance demands of critical industries. These tubes offer exceptional thermal expansion compatibility with glass, ceramics, and specific stainless steels, making them ideal for applications requiring hermetic seals and dimensional stability. With a unique composition of 29% nickel, 17% cobalt, and trace elements, 4J29 has a controlled CTE that closely matches borosilicate glass and alumina ceramics, eliminating mechanical stress during temperature changes. Capillary tubes made from 4J29 are cold-drawn to achieve inner diameters as small as 0.1 mm, with tolerances within ±0.005 mm and a surface finish of Ra ≤ 0.4 μm, preventing fluid turbulence and particulate entrapment. Advanced annealing techniques optimize ductility without compromising thermal properties, enabling complex forming for medical and aerospace applications.
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