The term friction welding is quite straightforward: using friction to obtain a weld. Asperities is an important phrase as it is a smooth surface containing many microscopic projections. These smooth surfaces interact when moved relatively. This simple principle is used to obtain friction welds.
Friction welding is a solid-state metal joining process that produces high-integrity, and full-contact joints. This is achieved by rotating one workpiece relative to another under a compressive axle force. The friction generated between the two surfaces produces intense heat, resulting in the plasticity of the material.
Well, in this reading, we’ll explore what friction welding is, its applications, diagrams, techniques, and how it works. We’ll also discuss the advantages and disadvantages of friction welding.
Let’s Get Started!
What is Friction Welding?
Similar to forge welding, friction welding is a solid-state welding process that generates heat through mechanical friction between the workpieces in relative motion with one another. The addition of literal forces helps to obtain the weld. Friction welding is used with metals and thermoplastics in a wide variety of aviation and automotive applications.
The friction welding process is different from fusion welding but more like forge welding because no melting occurs. The weld is obtained because of the thermomechanical treatment at the contact surface.
As earlier mentioned, in the work of friction welding, heat is generated at the melting part of the workpiece so that it can fuse (weld) when external pressure is applied. The friction takes place between the parts until it turns plastic, normally at 900–1300 centigrades of steel.
At this point, a uniformly increasing pressure force is applied to the workpiece, and a permanent joint is obtained. Generating friction is the force-resisting motion between two or more interacting surfaces. The interaction of these asperities through elastic and plastic yielding generates heat. Friction welding utilizes this event for joining applications.
Applications of Friction Welding
The applications of friction welding are vast in today’s world of manufacturing. This is because friction is used in welding tubes and shafts. It is also widely used in the aerospace, marine, oil, and automobile industries to weld machine parts. It is also applicable to components like gears, axle tubes, drivelines, valves, etc.
Applications of friction welding are also used to join hydraulic piston rods, truck rollers bushes, etc. It is used to weld drill bits, connecting rods, gear levers, etc. Finally, friction welding processes are widely used in the electrical industry for welding copper and aluminum equipment.
Diagram
What are the Techniques of Friction Welding?
The techniques of friction welding are rotary, linear, friction stir, and friction surfacing friction welding.
Rotary friction welding
Rotary friction welding (RFW) is one of the most common methods of friction welding. One part of the material is rotated by the other and pressed down. The heating of the material is caused by friction work and creates a permanent weld. This method of welding is shown in the video below.
Linear friction welding
Linear friction welding (LFW) is achieved by moving one of the parts to be welded in a linear reciprocating motion across the face of a stationary part.
Friction stir welding
In this method of friction welding, a non-consumable tool is used to join the two-facing workpieces. This is solid-state welding and does not melt the workpiece material. The friction between the rotating tool and the material generates heat.
Friction surfacing
Friction surfacing is a method derived from friction welding where a coating material is applied to a substrate. Mechtrode is the name of the rod that contains the coating material. It is rotated under pressure generating a plasticized layer in the rod at the interface with the substrate.
How Does Friction Welding Works
Before any operation will be performed in friction welding, the surface of the workpieces must be prepared. One of the workpieces is mounted on a driven rotor and the other remains in a stationary position.
The rotor rotates the workpiece against the other in order to create friction between them. It rotates at a high speed and a little pressure force is applied toward the stationary workpiece, which is done takes away dirt from the workpiece surface. The rotor stopped when the temperature reaches its limit.
At this point, very high pressure is forced through the stationary workpiece when they are already in plastic form. The pressure is applied continuously until the whole weld is formed. Now, let’s explain the working of friction welding in stages:
In the first stage heat is generated between the workpiece surface by sliding friction and the torque reaches its maximum value. During the second stage where heat is generated by mechanical dissipation in the plasticize material and softened material flows radially outwards.
In the third stage, a steady-state situation is attained and the torque, rate of axial shortening and temperature distributioin are constant. At the fourth stage, the rotation between the workpieces are terminated. And stage five is where upsetting occur.
In friction welding, before joining or forming of item becomes a usable product, there must be industrial standard for various applications. Other parameters in friction welding method like rotational speed, friction time, friction pressure, forging time, and forging pressure must be put to consideration.
Advantages of Friction Welding
Now you can see that this type of welding applies to different fields and can be used to weld different items. This is because it helps in reducing grain growth in engineering materials such as high-strength heat-treatment steel. And because no melting is involved. Dissimilar materials can be joined In this type of welding. That is why it is applicable in aerospace, where lightweight materials like aluminum and high strength are to be joined.
Another advantage is that the weld surface is cleaned due to the motion between the materials that are joined and full strength is obtained in the joint with no additional weight to the workpiece.
Friction welding is also used with thermoplastic materials. It uses very low heat and pressure on the materials. This is why friction welding can be used to join metals to plastics with the metal interface being machined. Well, the following are some other advantages of friction welding:
- It is an environmentally friendly process. That is, the welding operation can be performed anywhere as it generates no smoke, flame, light, etc.
- No filler material is required.
- The welding process is fast.
- It is easily automated.
Disadvantages
Below are the limitations of friction welding:
- Friction welding equipment is of high cost.
- Materials that cannot be forged won’t weld. finally,
- One of the greatest disadvantages of friction welding is that it has limitations to workpiece dimensions. In the sense that round bars with similar cross-sections are restricted, joint designs are limited and the workpieces need to be fixed.