Vacuum brazing technology and industry applications

1. Introduction

Vacuum brazing technology has become a very promising welding technology since the 1940s. It first appeared in the electronics industry to braze copper and stainless steel parts. Later, with the rapid development of aviation industry, electronics industry, automobile industry, oxygen generator industry and rocket missile technology, vacuum brazing technology has also been developed accordingly. Vacuum brazing technology is widely used in the manufacture of honeycomb sandwich structure wall panels, jet engines and rocket missile device assemblies, metal filters, waveguides and various radiators.

 

2. What is vacuum brazing

Vacuum brazing refers to a process method of brazing in a high vacuum environment without brazing flux using welding metal brazing filler metal.

Working principle:
The brazing filler metal is applied to the surface of the parts to be vacuum brazed, and then placed in a vacuum brazing furnace. The vacuum system starts to work and the air is extracted. When the vacuum degree reaches 10-3Pa, it starts to heat. When the heating reaches the brazing temperature required by the process, the brazing filler metal begins to melt, and the liquid brazing filler metal wets the base metal and fills the gap of the brazing tip under the capillary action. At the same time, the brazing filler metal elements diffuse into the base metal, and the base metal dissolves in the liquid brazing filler metal to form a high-quality brazed joint.

 

 

3 Advantages of vacuum brazing 

 

1. During the vacuum brazing process, the workpieces being brazed are in vacuum conditions, and there will be no oxidation, carbonization, decarburization, pollution and deterioration. The welded joints are clean and strong.
2. During brazing, the brazing temperature is lower than the melting point of the base metal, which has little effect on the base material. The overall heating of the parts is uniform, the thermal stress is small, and the deformation can be controlled to a minimum, which is particularly suitable for the brazing of precision products.
3. The low pressure (vacuum) around the base metal and the brazing filler metal can eliminate the volatile gases and impurities released by the metal at the brazing temperature, which can improve the performance of the base metal.
4. It has broadened the design path of products. Brazed parts are allowed to have narrow grooves, extremely small transitions, blind holes, etc., which are particularly suitable for closed containers and parts with complex shapes. It can also braze multiple adjacent brazing seams at a time, or braze multiple components in the same furnace. The brazing efficiency is high, and there is no need to consider corrosion, cleaning, damage and other problems caused by brazing agents.
5. The heat treatment process of the workpiece can be completed simultaneously during the brazing process. By selecting appropriate welding process parameters, brazing can also be arranged as the final process to obtain a brazed joint with performance that meets the design requirements.
6. There are many types of metals that can be brazed, especially suitable for 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 different metals such as titanium, zirconium, niobium, molybdenum, and tungsten; it is also suitable for composite materials, ceramics, graphite, glass, diamond and other materials.

 

4. Main applications of vacuum brazing technology

 

01)  Aircraft engines
Vacuum brazing is widely used in honeycomb structures as sealing components of various types of aircraft engines. The honeycomb structure brazing process is to pre-place the brazing material in the honeycomb core grid, then assemble the honeycomb and the shell, and finally use the vacuum brazing method for brazing. The strength of the brazed joint is about 50% of the parent material. The grouped stator blades of the aircraft engine compressor are also manufactured by this brazing method. It consists of inner and outer rings and more than 10 blades connected as a whole by vacuum brazing.
In addition, vacuum brazing is also used in the manufacture of turbine guide vanes, guide vanes, diffusers, flame tubes, oil filters and other components in aircraft engines.

 

 

 

02) AMB ceramic substrate
The AMB (active metal brazing) process is a further development of the DBC process technology. It uses a small amount of active elements Ti and Zr contained in the brazing material to react with ceramics to form a reaction layer that can be wetted by liquid brazing material, thereby realizing a method of bonding ceramics and metals. It not only has higher thermal conductivity and better copper layer bonding, but also has the advantages of lower thermal resistance and higher reliability. It is more suitable for preparing ceramic copper-clad substrates for IGBT module packaging in electric vehicles and power locomotives. Especially in important fields such as wind energy, solar energy, heat pumps, hydropower, biomass energy, green buildings, new energy equipment, electric vehicles, and rail transit, the rapid development of power electronics technology will form a huge demand for ceramic copper-clad substrates, which are the key materials for IGBT module packaging.

 

 

 

03) Diamond tools
Brazed diamond tools are divided into two categories: surface-mounted and impregnated. Surface-mounted tools are used to braze diamond directly on the surface of the substrate, and impregnated tools are used to sinter diamond and other materials into a composite. The sintering process of the diamond composite is essentially the diffusion brazing process between the diamond and the substrate material. The brazing of diamond tools is divided into three categories: single-layer diamond tool brazing, diamond tool head brazing, and PDC composite sheet brazing. It has been widely used in many industries such as stone tools, woodworking tools, aerospace and military industries.

 

 

04) Vehicles and ships
Vacuum brazed plate-fin oil coolers are used in vehicles and ships. The plate-fin oil cooler has the characteristics of high heat transfer efficiency, compact structure and light weight. It is an updated product of diesel engine coolers today and has been widely used in automobiles, tractors, marine diesel engines and other fields.

 

 

05) Air separation equipment
The vacuum brazing technology used in the impeller of the air separation equipment greatly improves the manufacturing accuracy of the narrow channel impeller, thus not only ensuring the design performance indicators, but also reducing the manufacturing cost and shortening the production cycle.

Quanzhou Huice Company supplies vacuum brazed diamond tools, mainly used for material processing in fields such as stone, ceramic tiles, ceramics, and construction engineering. Our company adopts the second-generation vacuum brazing technology, which greatly enhances the grip on diamond abrasive particles, making our diamond tools not only sharper but also greatly improving their service life