02/08/2026
Our radiator core goes through continuous tunnel furnace for brazing. The furnace size is 65 meters length, 1.8 meters width, valid brazing area is 1.2 meter by 0.25 meter. There are total 5 sections for the furnace: Cleaning--Flux Application--Drying--Brazing--Cooling
1.CLEANING
Prior to fluxing, the assembled (radiator core) typically goes through a cleaning step to remove residual lubricants and forming oils
2.Flux Application
Flux is then applied to assembled units as an aqueous slurry by flooding, spraying or dipping. A surfactant is commonly added to the slurry to aid in wetting and uniformity of flux deposition. Agitation is required to prevent the flux from settling. The slurry concentration, typically in the range of 4 % to 6 %, regulates flux loading. An air “blow-off” step is also typical to remove excess slurry accumulated at the downside of the fluxed part. The goal is to achieve a uniform coating of flux without significant accumulation in any one place.
For core motherboard(header) and tube end, where located in sides and may not be sprayed thoroughly,here is required hand spraying( 2 operating worker standing on both side, and spraying the assembled unit manually (concentration range of 12% to 17%)
*Once molten, the flux works by dissolving the tenacious oxide present on aluminum, and prevents further oxidation.
3.DRYING
After fluxing, the part is then dried, usually at about 200°C. Care is taken not to overheat the the assembled unit as excess heat may cause high temperature oxides to form on aluminum surfaces. The aim here is simply to remove water from the fluxing stage so that the component is completely free of adsorbed water prior to entering the brazing furnace. Since only a light flux loading is required the resultant flux adhesion is quite sufficient.
*after drying, an operating worker who use tools to brush extra flux(white powder) off the assembled unit, is also required.(over fluxing will cause the flux residue remains on the surface of the assembled unit after brazing)
4.BRAZING
The brazing section adopt 6 sub-sections 12 temperature zones for separated control. These 12 temperature zones are engaged in 3 parts of job: Warm Up-Constant Temperature Melting-Solidify. Constant Temperature Melting usually takes time between 4-5 minutes during processing,to make sure clad layer(AA-4343)can be completely melting.
*Aluminum alloys are classified according to their alloying elements. Alloys such as AA-3003(melting point is between 630-660 degree) is commonly used as core materials for NOCOLOK flux brazing.Alloys AA-4343 acts as clad layer (lower melting aluminum -silicon,melting point between 596-600 degree). This thin layer, usually makes up 5 % to 10 % of the total thickness of the brazing sheet.
99.999% pure Nitrogen is introduced in the critical brazing section of the furnace and flows towards the entrance and exit. This prevents the ingress of contaminants from outside the furnace.These conditions are necessary for optimum brazing results.
5.COOLING
In Cooling Section, brazed radiator core has been cooled down to a temperature that operating workers can take the finished product out of the furnace.
