Strip and sheet for HVACR

Aluminium brazing sheet is often used for tubes (0.25–0.60 mm), headers (1.2–1.6 mm) and side plates (1.0–1.6 mm) or as clad fins (0.08–0.10 mm) in all-aluminium brazed aluminium heat exchangers.

Manufacturing

Aluminium brazing sheet is manufactured by roll-bonding techniques to clad a core alloy ingot on one side or both sides with a low melting AlSi alloy. As an alternative, one side can be clad with a non-braze alloy, e.g. Zn-containing alloy. 

• Depending on the desired final properties, the core is either homogenized or not before the cladding operation

• The whole package is subjected to preheating, hot rolling and cold rolling down to the final thickness of the respective products

Depending on the requested final properties, the material is subjected to final annealing and / or intermediate annealing operation(s).

The core provides structural integrity. It is common to use a variety of aluminium alloys, examples being
• AA 3xxx (AlMn), more particularly
AA 3003, AA 3005, AA 3105 and modified versions of AA 3003 or AA3005 (long life alloys)
• AA 6xxx (Mg- and Si-containing)

The most common core alloys used in brazing sheets for aluminium heat exchangers are of AA 3xxx series.

Braze clad with a typical thickness of 5–to-15 percent of the total sheet thickness melts and flows during the brazing process, to provide upon cooling a metallic bond between the components. It is common that the braze clad alloy are from the AA 4xxx series or more particularly
• AA 4343 (Al-6.8~8.2 wt.% Si)
• AA 4045 (Al-9.0~11.0 wt.% Si)
• AA 4047 (Al-11.0~13.0 wt.% Si)
• AA 4343+Zn or AA 4045+Zn
• AA 4104 (vacuum braze with Mg)

Waterside alloy
• AA 7072 is often used on coolant side of heat exchanger components to provide sacrificial corrosion protection to the core.