Diffusion welding is unfamiliar to us, it refers to the solid state welding method in which the workpiece is pressurized at high temperature without visible deformation and relative movement. The following will give you a brief introduction to the working principle and advantages of diffusion welding.

First, the working principle of diffusion welding:

Diffusion welding is a kind of pressure welding. It refers to the contacting surfaces, under the action of high temperature pressure, the connected surfaces are close to each other, and local plastic deformation occurs. process of reliable connection. The diffusion welding process can be roughly divided into three stages. The first stage is the physical contact stage. Under the action of pressure and temperature, there are always some points on the connected surface that first reach plastic deformation. Under the action of continuous pressure, the contact area gradually expands. Reliable contact on the entire surface is achieved; the second stage is the mutual diffusion of atoms at the contact interface to form a firm bonding layer; the third stage is the bonding layer formed in the contact part, which gradually develops towards the volume direction to form a reliable connection joint.

Of course, these three processes are not completely separated, but intersect with each other, and finally form solid metallurgical bonds in the joint connection area due to processes such as diffusion and recrystallization, which can generate solid solutions and eutectics, and sometimes generate intermetallic compounds, forming Reliable connection. The selection of welding parameters is to control these factors and finally obtain joints with good comprehensive properties. Not only the interaction between atoms formed by diffusion, but also the properties of interface products should be considered.

The main parameters of diffusion welding are: temperature, pressure, time, gas medium, surface state and the choice of the intermediate layer. The main ones are temperature, pressure and time. Temperature affects the yield strength of the material to be welded and the diffusion behavior of atoms, and plays a decisive role in eliminating voids. The empirical formula for diffusion temperature is T = (0. 6～0. 8) Tm , where Tm is the amount of the material in the material to be welded. **Melting point.

Second, the advantages of diffusion welding:

Diffusion welding can weld almost all metals or non-metals without reducing the performance of the material to be welded because the matrix is not overheated or melted, especially suitable for fusion welding and other materials that are difficult to weld, such as active metals, heat-resistant Alloys, ceramics and composites, etc. Diffusion welding is a suitable welding method for the same materials with poor plasticity or high melting point, as well as dissimilar materials that are immiscible or produce brittle intermetallic compounds during fusion welding.

The quality of the diffusion welded joint is good, and its microstructure and properties are close to or the same as those of the base metal. There is no fusion welding defect in the weld, and there is no overheated structure and heat affected zone. Welding parameters are easy and precise to control, and joint quality and performance are stable during mass production.

The weldment has high precision and small deformation. Due to the small pressure applied during welding, the workpiece is mostly heated as a whole and cooled with the furnace, so the overall plastic deformation of the weldment is very small, and the workpiece after welding is generally no longer machined.

The large-section workpiece j I can be welded because the welding pressure is not large, so the tonnage of the equipment required for the large-section welding is not high, and it is easy to realize.

Workpieces with complex structures, inaccessible joints and large thickness differences can be welded, and many joints in the assembly can be welded simultaneously.