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A picture to understand the vacuum diffusion welding furnace

August 03,2022

1. Vacuum Diffusion Welding:

Vacuum Diffusion Welding refers to a welding method in which the closely attached components are kept at a certain temperature and pressure for a period of time in a vacuum environment, so that the atoms between the contact surfaces diffuse each other to form a connection. It can not only realize the connection between the same kind of dissimilar metal materials, but also realize the connection between metal and ceramic materials, composite materials and so on.

2. The advantages of vacuum diffusion welding:

Low welding temperature and wide range of applicable materials. During diffusion welding, the matrix does not melt or overheat, which can realize the connection of materials that are difficult to achieve by other methods.
High welding strength and good joint quality. The structure and performance of the welded joint are close to the base material, and the quality of the joint is stable.
The welding process is irreplaceable. Components with complex structures and large thickness differences can be welded, and multiple welds can be welded at the same time.
Small welding deformation, suitable for the manufacture of structure-function integrated precision products.

3.The formation process of vacuum diffusion welding joint:

Assembly at room temperature
Stage 1: Contact Deformation
Arbitrary deformation of surface particles (microscopic roughness) and films to form an initial degree of mechanical contact.

Stage 2: Diffusion Interface Transition
The interface deforms over time, further forming a tight interface at the interface.

Stage 3: Disappearance of interfaces and holes
By continuing to diffuse, the formed connection is further strengthened, the firm connection surface is enlarged, the interface hole is eliminated, and the joint organization and composition are homogenized.

4.The main process factors affecting vacuum diffusion welding

Temperature: affects the rate of atomic diffusion, which in turn affects the strength of the weld joint, generally 0.5 to 0.8 times the melting point of the material.
Pressure: Expand the effective contact area of the substrate and promote the plastic deformation of the joint surface.
Vacuum degree: degassing, anti-oxidation, and improving weldment performance.
Diffusion time: Appropriate diffusion time helps to improve the uniformity of joint tissue.

5. Strict requirements for vacuum diffusion welding equipment:

Sufficient effective heating interval
High vacuum degree
High temperature control accuracy
Good uniformity of furnace temperature
High pressure control accuracy
The equipment is safe and reliable
 Vacuum diffusion welding furnace is an important precision instrument.
The correct use of vacuum diffusion welding furnace plays an important role in ensuring the quality of diffusion welding, prolonging equipment life and reducing production costs.
Multi-stage control of pressure accuracy, self-adaptation of pressure head and field promotion are the development directions of vacuum diffusion welding furnace in the future

6. Application of vacuum diffusion welding furnace

6.1 Metal Materials
The same material: vacuum diffusion welded titanium alloy hollow rectifier blades and aluminum alloy water-cooled plates are used for aero-engine systems and air cooling systems respectively.

Different materials: bimetallic components formed by vacuum diffusion welding of copper and steel are widely used as hydraulic pump cylinders, oil distribution pans, coal drilling rig oil jackets, bimetallic rotors, etc.

6.2 Non-metallic materials
α-Al2O3 ceramics and metallic nickel; high-entropy alloy CoCrFeMnNi and stainless steel;
WC-Co cemented carbide and aluminum, etc.; Ni3Al intermetallic compound, single crystal alloy, etc.
application:Electronic packaging; high temperature structural parts, etc.
Features:Overcome the differences between materials and combine their excellent properties to expand the application range of materials.

7. Vacuum Diffusion Welding Equipment

7.1 Structure diagram of vacuum diffusion welding furnace 

7.2 Advantages of ACME Vacuum Diffusion Welding Furnace
The press is integrated with the heating chamber.
High precision of pressure control and displacement control, and good equipment reliability.
Good uniformity of furnace temperature and high quality of diffusion welding products.
Conventional cooling and rapid cooling are optional, and the equipment has strong applicability.
The indenter is easy to install and disassemble, and it can also be used as an independent brazing furnace without pressurization, and the equipment has strong versatility.

7.3 Technical Features of ACME Vacuum Diffusion Welding Furnace
The heating element is modularized, controlled by PID multi-stage program, and the temperature uniformity is good.
Equipped with 0.001 grade German imported pressure sensor, high pressure control accuracy; equipped with 10um high-precision displacement sensor, accurate displacement control;
Independent supplementary pressure control system to ensure accurate constant pressure of diffusion pump.
Professional dynamic sealing structure ensures stable operation under vacuum and high pressure without leakage.
The pressure field is verified by finite element simulation, the upper/lower indenter has sufficient safety margin, there is no slight deformation under high temperature, and the base surface of the pressed workpiece is flat.

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