BrazeLet^® Ni7R-9003

The nickel-based brazing alloy BrazeLet BNi7 is a free-flowing material suitable for brazing stainless steels. It is suitable for brazing in vacuum or protective atmospheres (dry hydrogen or argon). It allows brazing at lower temperatures than most of the other nickel-based brazing alloys. It is particularly suitable for brazing deep narrow joints as it maintains the excellent flowability with limited P diffusion into most base materials. It is recommended that gaps do not exceed 30 µm as wider gaps risk the formation of a crack-sensitive brittle centre line. Typical applications for this brazing alloy include thin-walled components such as honeycomb seals, industrial heat exchangers and tubular heating elements for drinking water applications.

The brazing paste BrazeLet Ni7R-9003 can be used for roller coating fins or structured plates, typically found in flat heat exchanger designs. Depending on type of roller used the paste can be applied with thin layers either on top or on the side of the fin tips. Gap size between the paste roll and the scraper of 0.08 – 0.12 mm is recommended. The amount of paste is controlled by weight and is a function of the fins or structured plate design. BrazeLet Ni7R-9003 properties allow reliable application in a wide range of coating speeds, tested with good results from 3 m/min up to 20 m/min. The oil-based paste ensures reliable coating over time without drying on the roll. BrazeLet Ni7R-9003 has higher metal content and lower binder content compared to standard roller coating pastes, which decreases packaging and transportation needs for the same amount of brazing filler metal.

The coated fins can be dried with standard drying process (hot air) at 120 – 170 °C. The drying time depends on thermal mass, parts design and the used furnace and thus needs to be established. When dried, the paste has excellent adhesion to the metal sheet.