Application of vacuum brazing on aluminum honeycomb panels of railway vehicles

---

As an important lightweight material, aluminum honeycomb panels are widely used in the aviation manufacturing industry, and have long been used in foreign railway vehicles. Its uses are quite wide, such as the French TGV series and the Italian ETR series high-speed trains. The domestic use of aluminum honeycomb panels has only been in recent years. Although it has achieved certain results, its application scope is still limited. The understanding of the characteristics and application scope of honeycomb sandwich materials needs to be further strengthened and expanded.

Aluminum honeycomb panel is a composite material made by bonding aluminum honeycomb core material and surface material. In summary, aluminum honeycomb panel has the following basic characteristics:

(1) Light weight, high strength, especially high bending rigidity, the bending rigidity of the same quality aluminum honeycomb panel is about 5 times that of aluminum alloy.

(2) It has extremely high surface flatness and high temperature stability, easy to shape and not easy to deform. Aluminum honeycomb panels can not only be made into flat panels, but also can be made into double-curved and single-curved panels, and then disassembled after making vehicle parts Convenience.

(3) Excellent corrosion resistance, insulation and environmental adaptability, which can adapt to various harsh operating environments of railway EMUs and passenger cars; in addition, according to needs, this type of board can be treated with surface painting or surface sticking fireproof board to achieve Good decoration and fire resistance.

(4) Unique resilience, can absorb vibration energy, has good sound insulation and noise reduction effect.

(5) The fire protection level is high, meeting the requirements of Class A in the International Intermodal Transport Fire Protection Standard UIC564-2-199l “Fire Protection and Fire Protection Rules for Railway Passenger Cars or Similar Vehicles Used by the International Union”.

(6) After encountering a fire, the smoke density meets the high-level international railway fire protection standards, and has good self-extinguishing; low heat release value, can form a refractory layer, can reduce the emitted smoke and toxic gases, and has excellent environmental performance .

(7) Excellent molding and manufacturing process, which can meet the requirements of complex shapes and high stability requirements of internal parts of railway vehicles.

In foreign countries, the TGV series in France and the ETR series in Italy have long used honeycomb sandwich structure composite materials to make interior wall panels and roof panels. Subsequently, many railway vehicle manufacturers in Europe have adopted aluminum honeycomb panels to manufacture railway vehicles. Components, the scope of application covers the side wall panels, inner roof panels, partition panels, floor panels, door panels of interior and exterior doors, luggage racks and other components in the interior structure. Among them, Italy is relatively leading in the application of aluminum honeycomb panels. Italy has long used aluminum honeycomb panels to manufacture structural parts such as luggage racks with complex shapes and inner wall panels with curved windows.

In China, the earliest application of aluminum honeycomb panels was to manufacture the partition walls of 25A soft-sleeper passenger cars. Due to the inadequate manufacturing technology at that time, the application effect was not very satisfactory. Therefore, it failed to continue to promote the application on subsequent 25-type passenger cars. At the end of the 20th century, due to the high requirements for lightweight vehicles during the development of EMUs, aluminum honeycomb panels were first used to make partitions, flat roof panels and door panels on domestic EMU prototypes, which achieved good results. Subsequently, aluminum honeycomb panels were widely used. At that time, aluminum and aluminum honeycomb panels were not only used to manufacture partition walls, flat roof panels, undercarriage equipment compartment bottom panels and various door panels. Aluminum honeycomb panels are also used to manufacture air-conditioning ducts and air-conditioning unit shrouds. Among them, the application effect of interwall, flat roof, air-conditioning ducts and air-conditioning unit shrouds is the most significant, which greatly reduces the cost of related parts. Quality, to achieve the overall lightweight of the vehicle, and to improve the manufacturing accuracy and quality of parts, thereby improving the manufacturing quality of the entire vehicle.

However, the real breakthrough in the application of aluminum honeycomb panels is the CRH series of EMUs. The breakthrough progress mentioned here is mainly reflected in two aspects:

(1) The aluminum honeycomb panel is used on the CRH series EMUs to manufacture the inner wall panel with complex shapes, manufacturing tolerances and high appearance quality requirements. It breaks through that the aluminum honeycomb panel can only be used to manufacture planar structures or only in one direction. The design concept of bending parts makes its application scope break through the application scope of interior floor, partition wall, various interior and exterior door panels and air supply duct of air conditioning system.

(2) Aluminum honeycomb panels are used on CRH series EMUs to make luggage racks that are not only complex in shape, but also have high load-bearing and wear resistance requirements, breaking through the tradition that aluminum honeycomb panels cannot be used to manufacture important load-bearing components of vehicle interior structures The design concept has expanded its application scope to a new field, and the domestic aluminum honeycomb panel application technology has entered a new stage.
With the continuous deepening of the localization of CRH series EMUs in recent years, it has been possible to use aluminum honeycomb panel forming and processing technology to manufacture parts with complex shapes in China, which has reached a high level in the field of aluminum honeycomb panel forming and application. However, in order to further improve the application level of aluminum honeycomb panels and improve the rationality, maturity and reliability of the design and manufacture of parts, the characteristics and applicability of aluminum honeycomb panels, application design methods, manufacturing technology and specific manufacturing Methods and means to further strengthen research, truly master the characteristics of aluminum honeycomb panels and application design methods, in order to further expand the application range of aluminum honeycomb panels, and promote further lightweight railway vehicles.

Manufacturing of aluminum honeycomb panel
In the manufacturing process of aluminum honeycomb panels, after the preliminary cutting process, the bonding process of aluminum honeycomb panels is a very important process. Aluminum has low hardness and low melting point, and the integrity of aluminum must be ensured during heat treatment.
The vacuum brazing furnace has been the choice of more and more consumers in recent years. Because the vacuum brazing furnace has many advantages that the general brazing furnace can not reach during the brazing process, it has become a trend in the development of the industry.

Advantages of vacuum brazing furnace:
1. Adopt zone heater layout to make the temperature uniformity in the heating zone uniform.

2. Brazing in a vacuum atmosphere can keep the workpiece clean and bright.

3. Heating in a vacuum state can remove grease and oxide film on the surface of the workpiece, so the surface of the part has high brightness, no flux, and no cleaning after welding.

Because of the stable quality and good durability of the workpieces manufactured in the vacuum environment of the vacuum brazing furnace, it is a very good heat treatment option for aluminum honeycomb panels.

Edited by: Ryan Wu
Copyright: SIMUWU Vacuum Furnace

Related products:
Vacuum brazing furnace
High temperature vacuum brazing furnace