Solid State Welding Process (Its 4 Types You Should Know!)

solid state welding

What is Solid State Welding? Solid State welding process is a type of welding process in which the welding of metals takes place in its solid state (without melting them.)

More specifically, solid state welding processes are those processes in which the metals require heat below their melting temperatures and the welding occurs without the use of filler rod or filler material.

Types of Solid State Welding Processes

Types of solid state welding processes are mentioned below.

  • Friction welding
    • Inertia friction welding
    • Direct drive friction welding
    • Linear friction welding
    • Friction stir welding
    • Orbital friction welding
  • Ultrasonic welding
  • Explosion welding
  • Forge welding

Let’s discuss each of these solid state welding process one by one.

#1) Friction welding

friction welding

What is Friction Welding? 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.

Friction welding process

As shown in the image, 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.

rotary friction welding

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.

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

For more information on friction welding, refer to the main article: What is friction welding process? (definition, process, types and more)

#2) Ultrasonic welding

ultrasonic welding of metals

What is Ultrasonic Welding? Ultrasonic Welding is defined as a solid state welding process in which the joining of metals occurs due to heat and pressure energy produced by the application of a high frequency vibrator (frequency >20000 Hz).

Ultrasonic welding process

The ultrasonic welding system consists of two main components.

  • Power source and
  • Transducer

The power source used in ultrasonic welding is a frequency converter that converts the input power (having 60 Hz) into a high frequency electric power.

The transducer converts this high frequency electric power into mechanical vibrations.

The ultrasonic vibrations are produced by an oscillator which sets the output frequency.

The amplifier is used in ultrasonic welding in order to step up the input power to as high as 25000 watts. After this, the transducer converts this electrical power into mechanical vibrations.

The sonotrode is connected to the transducer which oscillates at a very high ultrasonic frequency (more than 20000 Hz or 20000 cycles/sec.)

At this time, the pressure is applied to the sonotrode from the top (see diagram).

Due to this pressure and high frequency vibrations of the sonotrode, the metal molecules heat up and they start to deform. 

Because of the pressure acting on the deformed workpiece, the workpiece starts to fuse with each other and finally solid weld is obtained.

For more information on ultrasonic welding, refer to the main article: Ultrasonic welding of metals (definition, process and more)

#3) Explosion welding

explosive welding

What is Explosive Welding? Explosive Welding (also known as explosion welding or explosive bonding or explosive cladding) is a type of solid state welding process in which a controlled explosive detonation is used to force two metals together at high pressure.

Explosion welding process

As shown in the diagram of explosive welding, the two metal plates which are to be welded are initially spaced at a smaller distance.

The frame containing explosive powder is attached to the surface of the upper metal sheet.

The detonator is attached and the setup is now ready for the explosive welding process.

explosion welding process

When the detonator is activated, the explosion takes place and it lasts for only a fraction of a second.

This high explosive force forces the top metal plate on the base metal plate with a very high velocity.

This creates a collision between the upper metal sheet and the base metal (which is at the bottom).

This pressure created by the explosion is higher than the yield strength of the materials, and because of this the welding of metals takes place easily.

For more information on explosive welding, refer to the main article: What is explosive welding? (definition, process and more)

#4) Forge welding

forge welding

What is Forge Welding? Forge welding process is a solid state welding process in which two metals are heated at a high temperature and then they are hammered together to form a single strong joint.

Forge welding process

First of all the parts which are to be welded are heated to a plastic condition.

The heating of these metal parts is done in any furnace suitable for heating the metal.

After the metal parts are heated to their plastic condition, they are hammered together.

This hammering can be performed by hand or machine.

For more information on forge welding, refer to the main article: Forge welding process explained (With 5 Pros and 6 Cons)


External links:
Rotary friction weld: Image by Shanjeevi. C, Satish Kumar. S, Sathiya.P, CC BY-SA 4.0, via Wikimedia Commons
Rotary friction welding steps: Image by Xyz00030280, CC BY-SA 4.0, via Wikimedia Commons
Explosion welding: Image by LaurensvanLieshout, CC BY-SA 3.0, via Wikimedia Commons

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