We talk about flux cored alloys when flux, an essential element for the success of brazing processes, is located inside the alloys. Recently developed, flux cored alloys are an alternative to traditional processes, that require flux separated from alloy, or flux coated rods. The aims are to increase the quality of final results, to reduce costs and to safeguard operators’ health.
This technology is especially suitable for silver and aluminium alloys, but also for brass and copper alloys, in rods, wires and preforms from wire (rings) make-ups. By its very nature, it can’t be used with very thin wires (less than 1 mm in diameter).
In cored alloys, the flux is in powder presentation form, in order to avoid oxidation, and it is along the entire lenght of wire.
This new approach is still not very popular, but it is destinated to spread to the most important applications, where quality of final result and safety of operators are priorities. We can easily understand that innovation of brazing comes this way.
TRADITIONAL METHODS OF BRAZING: STRONG POINTS AND LIMITATIONS
The most familiar method for brazing consists in using flux separated from alloy. This process is very versatile: it is suitable to join every alloy, of any make-up, size and material, with every flux, in powder, past or liquid form. The most important weakness of this method concerns final results, that are linked closely to the technical skills of operator. The common trend to use more flux than necessary can affect the quality of final product and, in any case, it involves high cost for post-braze cleaning. Another limitation is about the safety of operator: during the process of brazing, he is in contact with chemicals and exposed by fumes of flux.
The use of alloys covered by flux is certainly less versatile (it is suitable only for rods), but very frequent, too. Maintainers and installers, who often operate in situations of low practicability, tend to choose this convenient method. The use of coated rods has the same limitations of separated flux. The final resut depends on operator, who must avoid inclusions caused by the large amount of flux around the alloy. For this reason, post-braze cleaning is an expensive process. Then, this method of brazing is unhealthy for the operator, who has to protect himself from physical contact of chemicals and from flux inhalation.
FLUX CORED ALLOYS: STRONG POINTS AND LIMITATIONS
Problems of traditional brazing methods can be overcome by the use of flux cored alloys. In fact, thanks to flux cored alloys, we can obtain these advantages:
- QUALITY IMPROVEMENT AND STABILITY: inside the alloy, there is the right amount of flux (the quantity you need), that is released when the alloy starts to melt (when you need) and, with appropriate tips, only in predetermined points (where you need). So, flux inclusions are reduced and quality of joints doesn’t depend on operator’s expertise anymore.
- COST SAVINGS: minimum amount of flux means minimum costs for post braze cleaning, too.
- MORE ATTENTION TO HEALTH: with the use of cored alloys, safety risks are minimized. The operator is no more in contact with the flux, which is inside the alloy, and less fumes are released.
The main weak point of flux cored alloys is the high cost of production, much higher than separated alloys and coated rods. By the way, you should remember that this technology guarantees top quality of final results, and reduces failures, reworks, scraps and post-braze cleaning.
APPLICATIONS AND FUTURE PERSPECTIVES
Now, flux cored alloys are used in cutting-edge fields, where high-quality standards are required. In particolar, we are talking about aerospace, automotive, refrigeration and appliances and electrical industries.
For the important advantages on productivity and safety, we are sure that the future of brazing will follow this path, both in fields that already use this tecnology and in new areas that are looking for high performances.
Are you interested in flux cored alloys or would you like to have more information about products and applications? Contact your sale technician or send and email to info@stella-welding.com.