Nickel brazing fillers are used where a joint needs properties or service temperatures beyond many common copper- or silver-based fillers. The table compares six selected BrazeLet products by the AWS A5.8 classification identified on the manufacturer’s product page, along with nominal composition, melting range, minimum brazing temperature, and recommended joint clearance. These are product examples, not a replacement for the current AWS specification or an approved brazing procedure.

Nickel brazing filler metal classification

What the classification tells you

The BNi designation identifies a nickel-based brazing filler classification in the AWS A5.8 system. A classification is not a complete process recipe: the product form, base-metal combination, atmosphere, joint fit, heating cycle, and service environment still matter. The selected manufacturer data also lists corresponding ISO and AMS specifications for some products. Check the applicable edition and purchasing requirements rather than assuming that specification names are interchangeable in every contract.

Solidus is where melting begins and liquidus is where the filler is fully liquid. The interval between them can affect flow and how a joint is heated. The listed minimum brazing temperature is a distinct manufacturer recommendation; it is not obtained by adding a fixed offset to the melting range. The recommended gap is also product-specific. A clearance range from one filler should not be transferred to another alloy or base-metal system.

Comparing selected BrazeLet grades

For example, the manufacturer lists BrazeLet BNi2 as nominal Ni-7Cr-4.5Si-3Fe-3B, with a 970–1,000 °C melting range and 30–100 μm recommended gap clearance. BNi3 is a different chemistry, Ni-4.5Si-3.2B, with a 980–1,040 °C melting range and a 0–50 μm recommended gap. The overlap in melting ranges does not make the two products interchangeable: composition, wetting, joint gap, atmosphere, and intended application differ.

Manufacturer application notes identify BNi1 and BNi1A for stainless steels and nickel-based superalloys in vacuum or protective atmospheres. BNi2 is described for stainless steel in vacuum or protective atmospheres, while BNi4 is chromium-free and described for nickel-based superalloys and stainless components. Read the product page for the specific application notes and restrictions; the table is not a universal compatibility matrix.

The nominal chemistry helps distinguish classifications, but it is not a batch certificate. For example, the manufacturer lists carbon in BNi1 and describes BNi1A as a lower-carbon product with its own melting interval and applicable specification. A buyer should order against the required standard and inspect the supplied certification, not infer the exact product from the BNi number alone. If a specification calls out a particular AWS, ISO, or AMS designation, confirm that the chosen product and form meet the contract revision.

Use a qualified joining procedure

Before selecting filler, identify both base metals and the required joint properties. Confirm cleaning, atmosphere, flux requirements, gap at brazing temperature, thermal expansion, corrosion exposure, and service temperature. Nickel fillers may contain boron, silicon, and other alloying elements; verify any material, health, and process controls required by the product documentation.

Use a qualified procedure and representative test joints when strength, fatigue, pressure containment, or safety depends on the result. Melting temperature and classification alone do not predict joint strength, code acceptance, or interchangeability. Verify the lot certificate and current technical data sheet before production.

Brazing joins components by melting filler while keeping the base material below its own melting point. The listed minimum brazing temperature is therefore a process threshold for the named product, not the temperature to apply blindly to a torch or furnace. Heat transfer, joint mass, atmosphere, clearance, and thermal uniformity affect the real cycle. Use the procedure’s qualified heating profile and measure the relevant part temperature where required.

Source

Classifications, nominal chemistries, melting ranges, minimum brazing temperatures, clearance recommendations, and process notes are from Höganäs BrazeLet nickel-based brazing filler metal product data. The table is a selected subset of that page.