FA7999 is characterised by a high post braze strength and good corrosion properties. The alloy form large grains during brazing. The optimized alloy composition contribute to a high strength after brazing allows for a high amount of recycled raw material. The corrosion resistance of the fin alloys is good, with a low self corrosion rate. FA7999 is available with different zinc levels to allow for a tailored cathodic protection of tubes and fillets.
Pre braze grain structure.
Post braze grain structure.
The sagged distance is measured in a CAB batch furnace using a braze cycle with 20 minutes to 600 °C and 3 minutes dwell time. The sagging value is strongly influenced by both the gauge of the material and whether the sample is clad or not. The beam length is varied between 25 and 60 mm to accommodate for this.
Delivery condition temper and properties
Typical properties after brazing
* Measured on 70 μm material, 35 mm beam.
An important aspect of fins is that they should provide a cathodic protection of the tubes, due to a suitable potential difference between the tube and the fin. However, even though the fin has a low potential it should not corrode too fast, i.e. its self corrosion rate should be low.
9h SWAAT, low self corrosion rate, uniform corrosion.
The corrosion potential (ASTM G69) was measured on brazed unclad fin material.
* Can be adjusted to meet corrosion potential requirements.
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