FA7850 is a high performance tube and manifold alloy that is designed to have a high post-braze strength, with additional strength from heat treatment or natural ageing during operations. The FA7850 product is suitable in a controlled atmosphere brazing process, and optimum strength is obtained with a carefully controlled cooling rate after brazing. With a suitable combination of the FA7850 tube, fin and header, the resulting heat exchanger easily exceeds 40 days in SWAAT.
Grain structure after brazing.
Delivery condition temper and properties
Typical strength after brazing
* After brazing with cooling at minimum 1 ˚C/s and 14 days of natural ageing.
** As brazed.
Corrosion potential after brazing –710 mV (SCE). Corrosion on FA7850 tube after >40 days SWAAT (ASTM G85) brazed in combination with FA6815 fin. Only superficial corrosion was found.
Gränges has developed the tube slitting process into excellence. This ensures very high quality slit edges on tube strips, which is crucial in order to form and weld tubes with high quality and a high production yield.
Typical strength after brazing and ageing at room temperature
The graph shows the natural ageing behaviour of the FA7850 alloy. Also after extended operation at elevated temperatures (120 ºC), the material will not over-age.
Fatigue data, FA7850 + 10 % AA4343 + 10 % FA6815, naturally aged.
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