Copper tube brazing principle is briefly introducedc

1.brazing principle

Copper tube brazing is a welding method in which liquid filler metal is used to fill the clearance surface of brazing metal bonding surface to form a firm joint. The process has two basic conditions:

(1) The liquid filler metal can wet the brazing metal and densely fill all the gaps;

(2) The necessary physical and chemical reactions between liquid filler metal and brazing metal are carried out to achieve good metal-to-metal bonding.

2. Joint filling principle of liquid solder

During brazing, the liquid filler metal flows between brazing joints by capillary action. The ability of the liquid filler metal to infiltrate and attach to the base metal is called wettability. The better the wettability of the liquid solder to the brazed metal, the stronger the capillary action, so the filling will be more sufficient. The factors affecting the wettability of solder alloy are as follows:

3. Influence of metal composition of solder and weldment

If the solder and brazing metal are not mutually soluble in liquid and solid state, nor do they form compounds, the wettability between them is very poor. If they can be mutually soluble in liquid, solid or compound, the wettability between them is very good.

4.the influence of brazing temperature

The wettability can be improved obviously with the increase of temperature. However, if the temperature is too high and the wettability is too good, it will cause loss of solder and corrosion phenomenon due to fire. Therefore, in the brazing process, it is very important to choose the appropriate brazing temperature.

5. metal surface cleanliness of weldment

The oxides, oil stains and other impurities on the metal surface will hinder the contact between the solder and the metal of the welding part, so that the liquid solder becomes spherical and difficult to spread. Therefore, it is necessary to ensure the surface of the metal joint of the welding part is clean when brazing.

6.Metal surface roughness of weldment

Generally, the wettability of solder on rough surface is better than that on smooth surface. This is due to the special capillary effect of the crisscrossing grain on the liquid solder.