Vacuum Brazing Process

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Vacuum brazing can be divided into high vacuum brazing and partial vacuum brazing according to different vacuum conditions. High vacuum brazing is suitable for brazing filler metals and base metals that contain less volatile elements and are difficult to decompose oxides.

If the solder contains more volatile elements, in order to reduce the vapor pressure of these elements in the solder and base metal at the brazing temperature and improve the quality of brazing, partial vacuum brazing with a certain partial pressure of argon can be used technology.

During the heating process of brazing, the minimum pressure at which the brazing filler metal and base metal can maintain the solid or liquid phase is determined by calculation or experience. In the heating process of brazing in high vacuum state, a certain amount of high-purity argon is introduced when the temperature is just lower than the temperature at which the vaporization starts (liquidus temperature). in order to balance the vapor pressure of volatile metals at the temperature at which vaporization begins. With this technology, the evaporation of solder and base metal can be reduced, thereby greatly expanding the range of materials that can be soldered by vacuum brazing. In particular, it contains volatile elements such as manganese and phosphorus, and the effect is more obvious.

The partial vacuum brazing process can be summarized as two times of argon filling. The first time to fill with argon (argon partial pressure control), when the temperature is close to the welding temperature, fill with argon for 10 to 15 minutes, and the argon pressure is 40kPa. The second time to fill with argon (quick cooling), start the quick cooling when the temperature drops to 500°C, and the argon pressure is 70-80kPa.

The rapid development and application of vacuum brazing technology is mainly due to a series of advantages compared with other welding methods.

(1) During the whole brazing process, the parts to be brazed are under vacuum conditions (10-2Pa ~ 10Pa range), and there will be no oxidation, increase in connection, decarburization and pollution deterioration. The cleanliness and strength of the welded joints higher.

(2) During brazing, the whole part is heated evenly, the thermal stress is small, and the deformation can be controlled to a minimum, which is especially suitable for the brazing of precision products.

(3) The low pressure around the base metal and the brazing filler metal can eliminate all volatile gases and impurities released at the brazing temperature, improve the performance of the base metal, and obtain a very bright joint.

(4) Since there is no brazing flux, there will be no defects such as pores and inclusions, which can save the process of cleaning the residual flux after brazing, save time, improve working conditions, and have no pollution to the environment.

(5) The heat treatment process of the parts can be completed at the same time during the brazing process. By selecting appropriate brazing process parameters, brazing can also be arranged as the final process to obtain brazed joints whose performance meets the design requirements.

(6) Multiple adjacent welds can be brazed at one time, or multiple components can be brazed in the same furnace. High welding efficiency.

(7) There are many kinds of basic metals that can be brazed, especially suitable for brazing aluminum and aluminum alloys, titanium and titanium alloys, stainless steel, high temperature alloys, etc. It is also suitable for brazing connections of the same or dissimilar metals such as titanium, zirconium, niobium, molybdenum, tungsten, tantalum, etc. For the joining of refractory metals, vacuum brazing is one of the best ways to produce flawless joints. It is also suitable for composite materials, ceramics, graphite, glass, diamond and other materials.

(8) The product design approach is broadened, and it can be used for parts with narrow grooves, extremely small transition tables, blind holes, closed containers, and parts with complex shapes, without considering the corrosion and cleaning caused by brazing flux, etc. , damage, etc.

Equipment selection: The RHVB-H series vacuum brazing furnace produced by SIMUWU is a high-quality product for the vacuum brazing process of tools and molds. The good temperature control accuracy and temperature control uniformity ensure the effective progress of the vacuum brazing process. SIMUWU specializes in the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum air quenching furnace, vacuum oil quenching furnace, vacuum annealing furnace, etc., which are widely sold in developed and developing countries.