Why choose vacuum brazing

What is brazing?

There are many ways to permanently join one metal part to another without the use of fasteners. The most common methods include soldering, welding, and brazing. Soldering Most people have seen or actually used soldering in their lives. A common experiment is to drip molten metal solder on copper wire to connect a battery to a light bulb. In this experiment, a solder containing an alloy, which is usually made mainly of tin and mixed with other metals such as copper, antimony, or silver, is heated with a soldering iron. The alloy is suspended in a flux, which helps the solder flow and keeps the surfaces of the components being soldered clean and free of oxides. The flux then evaporates, leaving only the desired tin or metal alloy. Due to the properties of the flux and alloy, the solder melts at a lower temperature than the copper wire, so it can be used like glue and can hold the two wires together after cooling. Due to the metallic properties of the alloy, the solder can also conduct electricity at the joint. Soldering Soldering goes a step further in joining metals. Soldering not only heats the filler metal, but also heats the two pieces of metal to be joined together to fuse the two metals together. You may have seen welders at work in a car repair shop.

A car accident may deform metal parts in parts of the car body that need to be removed and replaced, so the repair shop technicians use acetylene cutting to cut away the damaged parts and replace them with new ones, cut and match the original parts, and weld them into place. Welding two metals together creates a strong bond because the metals of the two parts have been fused together at the junction. The crystal structures of the two different parts merge into each other and behave as if they were part of the same structure. The strength of the weld depends on whether the two parts being welded have similar original crystal structures, which usually means that the same or similar metal alloys work best.

Brazing
Brazing is between soldering and welding. Like soldering, brazing uses a filler material that melts and cools to join the two parts together along the seam or to fully fill a gap by capillary action. According to the American Welding Society (AWS), soldering uses filler materials that melt at 840 degrees Fahrenheit (450 degrees Celsius) or lower, while brazing uses filler metals that require higher temperatures to melt and flow. However, the temperature of brazing is not so high that the crystal structure of the base material is melted and fused together. The filler metal for brazing is generally of similar material to the base material, but is alloyed in such a way that it has a slightly lower melting point. To ensure that the filler metal does not change the structure of the base material when it melts, the brazing process places higher demands on temperature uniformity and process control. With precise control, the filler metal can be melted at the exact temperature set, using capillary action to evenly fill the joint or void to form a strong, airtight connection. Brazing can form clean, beautiful joints, usually without a lot of additional processing. After the parts are brazed, no further heat treatment is required to restore the original metal properties of the parts, because only the filler metal is heated to the point of solid-liquid transition – the integrity of the metal crystal structure in the base material is not affected. Brazed parts usually have rounded corners at the joint. This rounded corner design increases the stability of the part, reduces stress concentrations and improves the fatigue characteristics of the joint.

Why choose vacuum brazing?
Vacuum brazing can be brazed with fillers that do not require flux to prevent oxidation. And the vacuum is maintained throughout the brazing process, which can prevent oxygen from entering the brazing process to the greatest extent. These characteristics are very important for some customers who process special parts, when processing these parts, the chemicals or metals contained in the flux may produce unwanted impurities in the final brazed joint. Therefore, the parts after vacuum brazing are very clean. Because vacuum furnaces are designed with temperature control in mind, metallurgical experts know that vacuum furnaces can accurately, evenly and repeatably heat the brazing material and the parts to be joined. Complex structural parts that need to be connected in hard-to-reach places, or assemblies with a large number of joints, are more easily brazed in a vacuum furnace environment. Vacuum brazing also works well when two parts with thin or thick cross-sections need to be connected with a certain structural integrity. Thin plate workpieces need to rely on precise temperature control to avoid deformation, while thicker cross-section workpieces need to rely on workpiece thermocouple monitoring to ensure appropriate holding time so that the workpieces are heated evenly.

Advantages of Vacuum Brazing Furnaces
The atmosphere and temperature control in vacuum furnaces can achieve high temperature consistency for parts with complex surfaces. By heating and quenching the parts at a controlled rate, vacuum furnaces can precisely convert the brazing material to a liquid state without deforming the body of the parts to be brazed due to high temperatures, providing excellent control. Another significant advantage of using a vacuum brazing solution is the ability to control process byproducts. Vacuum furnace systems are significantly better than comparable salt bath or atmosphere furnaces in controlling and treating exhaust gases, and do not require harsh chemicals or molten salts that must be carefully controlled and handled. The vacuum brazing process also does not require additional post-processing and cleaning, which also reduces chemical waste generation.

Vacuum Brazing Furnace