What’s Friction Welding? (Definition, Process, Types & More)

friction welding

What is Friction Welding?
Definition: Friction Welding is defined as a type of welding process in which the joining of metals takes place due to heat produced by the mechanical friction.

(Remember: Friction Welding process is not a fusion welding process, but it is a type of solid state welding process. This is because in friction welding, the melting of metals does not take place, but it is like forging of metals with each other when they are plastically deformed.)

Principle of Friction Welding

principle of friction welding

Friction Welding Principle: 
Friction Welding works on the principle of heat generated due to friction. 
The workpieces which are to be welded are rubbed against each other at a very high speed and because of this friction, the heat is generated. 
This heat is enough to deform the metal. 
At this stage, the external uniform pressure is applied to the deformed workpiece, which ultimately welds the metal pieces with each other.

Friction Welding Process (How does friction welding work?)

friction welding process diagram

You can clearly see the line diagram of friction welding machine in the above image.

As shown in the diagram, the parts which are to be welded are aligned in a friction welding machine.

One part is stationary while the other part is rotating which is mounted in the chuck spindle.

The metal part which is mounted in the chuck is rotated at high speed, and at the same time the stationary part is pushed towards the rotating part.

friction welding process

Because of this, frictional heat is produced which is so high that it can deform the metal to its plastic conditions.

At this temperature, the interface of workpiece surface increases and at this time, the forging of workpieces takes place.

The rotation of the workpiece is stopped and the external pressure is increased which completes the weld.

The welding time can vary from 2 to 30 seconds depending upon the material to be welded. 

The pressure required for friction welding process is as high as 70 MPa and this may reach upto 140 MPa at the end.

Friction welding process is mostly suitable for welding of circular parts like pipes, tubes, etc.)

By using a friction welding process, dissimilar metal can also be welded.

I hope you have clearly understood how friction welding works. Now let’s see the types of friction welding.

Types of friction welding

There are 5 main types of friction welding process.

  1. Inertia friction welding
  2. Direct drive friction welding
  3. Linear friction welding
  4. Friction stir welding
  5. Orbital friction welding

Let’s discuss each of these friction welding one by one.

#1) Inertia friction welding

Inertia friction welding is a type of friction welding process in which the flywheels are with the chuck of the friction welding machine.

The spindle shaft is connected to the electric motor.

In the beginning of the friction welding process, the motor is connected with the spindle shaft which rotates the chuck, flywheel and other parts attached with the spindle.

After achieving the desired speed, the electric motor is disconnected and the chuck keeps on rotating due to the insert of the flywheel and other parts attached with it.

During this rotating stage of inertia friction welding, the metal pieces are brought in contact with each other which further generates heat and welding of metals takes place.

#2) Direct drive friction welding

In direct drive friction welding process, the electric motor drive continuously remains attached to the spindle shaft.

Rest of the process is similar as mentioned above in the rotary friction welding process.

#3) Linear friction welding

linear friction welding

Linear friction welding is similar to the inertia friction welding process, but the only difference is that the chuck oscillates in linear motion instead of spinning.

The workpiece which are to be welded using linear friction welding should have good shear strength.

Also the main advantage of using this process is that the metals other than circular shapes can also be welded easily.

The workpiece needs to be held rigidly in the position and very complicated machinery is used for this process.

#4) Friction stir welding (FSW)

friction stir welding

Friction stir welding is a type of friction welding process in which a non-consumable tool is used to join the workpiece.

The non-consumable tool rotates and generates the heat which deforms the workpiece material.

During the deformed stage of the workpiece, the pressure is applied along the joint line and the joining of metal takes place.

#5) Orbital friction welding

Orbital friction welding is similar to rotary friction welding, but the difference is that both the welding parts are rotated in the same direction at the same speed with their axis offset by up to ⅛”.

As the plastic deformation of metal takes place, the rotation is slowed down and both the workpieces are brought in the same axis and pressure is applied to join them.

Having discussed this, now let’s see the advantages and disadvantages of friction welding process.

Advantages of Friction Welding

Advantages of friction welding are mentioned below.

  • Time consumption for welding is very less.
  • Cleaning of surface is not necessary.
  • High quality weld is obtained by using a friction welding process.
  • Dissimilar metals can also be joined using a friction welding process (for example, steel can be welded with titanium, aluminum, and zinc).
  • Friction welding process is economical in terms of energy consumption.

Disadvantages of Friction Welding

Disadvantages of friction welding are mentioned below.

  • Friction welding is suitable only for circular butt weldings.
  • Initial equipment cost is higher.
  • Non forgeable materials cannot be welded using the friction welding process.

Applications of Friction Welding

Applications of friction welding are mentioned below.

  • Welding of gas turbine shafts.
  • Welding of pipes.
  • Welding of engine drive shafts.
  • Welding of refrigerator tubes with dissimilar metals.
  • Steering columns used in machinery, etc.

External links:
Friction welding principle: Image by Colinvella, CC BY-SA 3.0, via Wikimedia Commons
Linear friction welding and friction stir welding: Image credits – wikimedia commons

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