Steel-aluminum composite fin tube for radiator has the advantages of light weight and high heat exchange efficiency, and are widely used in chemical, automotive, aviation, petrochemical, power, medicine, metallurgy and other fields. This type of heat exchanger mainly adopts the brazing technology of steel-aluminum composite plate and aluminum fin...
Steel-aluminum composite fin tube for radiator has the advantages of light weight and high heat exchange efficiency, and are widely used in chemical, automotive, aviation, petrochemical, power, medicine, metallurgy and other fields. This type of heat exchanger mainly adopts the brazing technology of steel-aluminum composite plate and aluminum fin. We study the brazing connection of 3003 aluminum alloy and Q235 steel, 3003 aluminum alloy plate and Q235 steel plate with arc sprayed aluminum, and the related process of contact reaction brazing of 3003 aluminum alloy and 1Cr18Ni9Ti stainless steel:
(1) Using Zn90A14Ag5Ce solder to connect Q235 steel and 3003 aluminum alloy at 520 °C, the shear strength after connection increases first and then decreases with the extension of the holding time. When the holding time is 5min, the maximum value can be reached. The shear strength value can reach 17.6MPa; when the Zn90Al4Ag5Ce brazing filler metal is used for the brazing connection of aluminum and steel dissimilar metals, it has good mutual solubility with the base metal on both sides, and can be used as brazing filler metal for aluminum/steel dissimilar metals; At the bonding interface between Q235 steel and the intermediate weld zone, due to the strong affinity of Ag atoms and Al atoms, the diffusion rate of Al atoms to the steel side is slowed down, and the growth rate of the harmful brittle phase zinc-aluminum solid solution is slowed down, which is beneficial to brazing. The mechanical properties of the welded joint are improved; at the interface between the aluminum and the intermediate weld zone, due to the zinc-rich zinc-silver solid solution—grey-white band-like region, the Al atoms on both sides of the region have a large concentration gradient, which shows that the zinc-silver solid solution has an inhibitory effect. The ability of Al atoms to diffuse towards the steel side.
(2) Using Sn90Ag5Ti5 brazing filler metal at 260 °C while ultrasonically assisted vibration, the connection between Q235 steel and 3003 aluminum alloy by arc spraying was realized. The shear strength after connection increased first and then remained unchanged with the extension of ultrasonic vibration time. When the vibration time is 40s, the maximum shear strength value can be obtained, which can reach 14.3MPa; the main function of ultrasonic-assisted welding is to remove the surface oxide film, improve the wettability of the solder, and promote the liquid solder to the aluminum coating. The penetration of the hole part increases the bonding area of the solder and the aluminum coating, which is beneficial to the improvement of the weld strength. Without ultrasonic assistance, the connection between the two cannot be achieved; due to the low brazing temperature, the diffusion of the brazing filler metal and the metal on both sides is not obvious. During the brazing process, there is a small amount of oxidation in the weld zone.
