Welding Technology Parameters of Diffusion Welding between Different Metals ( or Alloys )
1.Process Overview
Diffusion welding is the name given to a solid state welding process that occurs when two metal elements or alloys are joined together under pressure. The precise properties of the metal elements or alloys involved determine the degree to which the metal melts and fuses together, and their atomic structure and crystalline composition also impacts on the welding process.
Diffusion welding is a solid state welding process as noted above, but it can also be used as a means of metal fabrication due to the precise nature of the materials involved. The process is often used when two metal elements must be joined together, such as aluminum and brass for a structural product, for example.
As the area to be joined is clamped together, a form of rapid heating is applied to the items in question. During this rapid heating process a diffusion bond is created at an molecular level so that the two metals in question ‘melt’ together. This is essentially a chemical reaction between the two materials, and forms a bond that is both strong and of a precise nature.
2. Process Parameters
The process parameters for diffusion welding between different metals or alloys can vary significantly depending on the materials used, as well as the application or purpose to which it is being used. Generally there are five different areas that must be considered when preparing the welding process, as summarized below:
How the parts are to be clamped together: The type of clamp used, the pressure applied and the position of the workpiece relative to the clamps all affect the process parameters. It is also important to consider if additional materials such as shims or spacers will be used to ensure the two parts are held together correctly.
The temperature gradient: It is essential that a temperature gradient be maintained during the welding process. This can be achieved by providing additional heat sources, such as an induction coil, or by controlling the temperature of the atmosphere around the welding area.
The heating rate: The rate at which the material is heated is important as this will determine the speed of the diffusion welding process. It is important that the rate of heating is controlled and not overexerted, as this can lead to microscopic weaknesses in the weld.
The pressure applied: The pressure applied to the workpiece is also important in the diffusion welding process. This helps ensure that the two elements are held together firmly during the process, and also ensures that the diffusion bond is formed correctly.
The type of atmosphere: The atmosphere around the workpiece is also important in the diffusion welding process, as this will help control the heat and prevent any adverse reaction between the metals. A vacuum is often used for this purpose, and must be controlled within certain parameters.
3. Conclusion
In conclusion, diffusion welding between different metals or alloys is a precise and advanced welding process with a number of different process parameters that must be taken into consideration. The materials used along with the exact application or purpose of the weld must be taken into account, and the correct facilities and atmosphere must be used in order to achieve the best results.
