Background knowledge

It is necessary for manufacturers of brazing technology to learn more about brazing and technical foundations during use, so that they can solve problems or create conditions for process progress when needed. The following are the background knowledge we consider to be more critical. Many of these noun explanations come from textbooks and literature, as well as our own understanding from an application perspective.  

Liquid and solid phase lines  

For a certain substance or mixed crystal substance (brazing material or flux), the meaning of the liquid phase line is the temperature at which the substance is at when it completely changes from solid to liquid during the temperature rise, or when the temperature drops, when solid appears in the liquid for a while. Similarly, the meaning of the solid phase line is the temperature when the liquid appears in the solid for a while during the temperature rise, or when the temperature drops, the liquid completely becomes solid.  

For the application of solder alloys or fluxes, the liquid phase line means that the solder or fluxes have reached the starting temperature of activity, and the solid phase line means that the temperature at which the substance has just begun to melt. During the brazing operation, the temperature difference between our solid and liquid phase lines has a significant impact on the operation. In the production of flux, we try to minimize the temperature difference between the solid and liquid phase lines.  

More readings: http://baike.baidu.com/view/1277122.htm 

More readings: http://baike.baidu.com/view/973809.htm  

Eutectic dot  

Eutectic point refers to the melting point of an alloy when the solid and liquid phase lines of substances meet (both the same temperature) under a certain ratio. When the material on the eutectic point melts, it will reach an active spreading point in an instant and completely liquefied.  

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Active temperature  

The active temperature is often for flux. Active temperature refers to the temperature point where an active ingredient in the flux has sufficient activation energy to achieve the first few effects. When the flux is completely melted, its active temperature may not be reached. The process of the effective substances in the flux need to have sufficient activation energy. The molecules of these effective substances are active through the acquisition of activation energy. The required reactions are more likely to occur and have high brazing properties, so that brazing can be completed.  

The combination of a good flux and a solder requires that the material designer combines the active temperature of the flux with the liquid phase of the solder. In the production of flux, we try to increase the active temperature range of the flux, so that this flux can be combined with more types of brazing materials, and it can be convenient for the brazer to operate.  

Surface tension  

Surface tension is the tension that acts on any boundary along the surface caused by the uneven molecular gravity of the liquid surface layer.  

Surface tension is a harmful property in brazing, which causes the solder melt liquid to fail to spread and fill the joints. One of the functions of flux is to break this surface tension.  

More readings: http://baike.baidu.com/view/263802.htm 

Oxidation film  

An oxide film refers to a thin film formed on the metal surface by the oxide produced by the action of metal elements with oxygen and water vapor in the air. The oxide film formed on some metal surfaces is very dense and can play a protective role. For example, a dense translucent oxide film formed on the surface of the aluminum material has a protective effect on the very active aluminum metal. Without this oxide film, aluminum would not be able to be used.  

During brazing, oxide film is a harmful substance. It hinders the adhesion, fluidity and spreading ability of metal brazing. One of the functions of flux is to remove the oxide film of metal, so that brazing can be completed.