Friction welding

MEANING:

In the joining processes, the energy required for welding (typically chemical, electrical, or ultrasonic energy) is supplied from external sources.

In this process, the heat requirement for welding is generated from the friction at the interface of the two components being joined.

We can prove the tremendous rise in temperature due to the friction by rubbing your hands together or by sliding down a rope rapidly.

With the help of a good amount of joint strength solid or tubular parts can be joined.

Shape of the fusion zones in friction welding
Fig. 1 Shape of the fusion zones

The size of solid steel bars up to 100 mm (4 in.) in diameter and pipes up to 250 mm (10 in.) in outside diameter have been friction welded successfully.

The surface speed of the rotating member may be as high as 15 m/s (3000 ft/
min).

The interface in frictional welding develops a flash by plastic deformation of the heated zone due to the combination of heat and pressure.

From the process of machining or grinding it becomes easy to remove the flash.

After individual cycle times for the complete operation are set properly then the operator skill required get minimum as the machines are fully automated.

It is defined as a solid-state welding process in which this process generates heat through mechanical friction between workpieces in relative motion to one another.

With the help of the addition of a lateral force called upset to plastically displace and fuse the materials.

Because of the above reason no melting occurs in this process.

It is not a fusion welding process, but a solid-state welding technique more like forge welding.

For the purpose of a wide variety of aviation and automotive applications, this process is used with metals and thermoplastics.

It is also observed that this process had been done on wood.

ISO norm is EN ISO, there is information about basic terms and definitions and table of weldability of metals and alloys.

HISTORY OF WELDING PROCESS:

The patents and application which was connected with friction welding were dated back to the turn of the century.

From this, rotary friction welding is identified as one of the oldest methods.

W. Richter patented the method of (LFW) process which was developed in 1924 in England.

And in 1929 in Germany, the same process in the USSR 1924 was patented by vauge and H.klopstock.

In the Soviet Union in 1956 the first description and experiments related to rotary friction welding took place.

After the scientific studies, the machinist  A.J. Chadikov has realized that this method can be used for commercial processes.

In USA in 1960 first time this process has been introduced.

Today, the research materials for this process come from many places around the world, including Africa, South America, North America, Europe and Asia, and Australia.

TYPES OF METAL TECHNIQUE USED:

ROTORY FRICTION WELDING

Rotary friction welding  is one of the methods of friction welding.

In short this is also called as RFW.

In this process, one welded element is rotated around the other and pressed down.

The heating of the material is caused because of the friction work.

LINEAR FRICTION WELDING

Linear friction welding is similar to spin welding, except that the moving chuck oscillates laterally instead of spinning.

In short it is defined as LFW.

FRICTION STIR WELDING

Friction stir welding
Fig.2 Friction stir welding

The solid-state joining process is of the friction stir welding.

For joining of two facing workpieces without melting a non-consumable tool is used on the workpiece.

At the surrounding of the Friction stir welding tool, heat is generated because of the friction between the rotating tool and the workpiece material, which leads to a softened region.

It mechanically intermixes the two pieces of metal, and forges the hot and softened metal by the mechanical pressure when the tool is traversed along the joint line.

FRICTION SURFACING

A rod that is mostly made of the coating material (called a mechtrode) is rotated under pressure, generating a plasticized layer in the rod at the interface with the substrate.

TYPES OF THERMOPLASTIC TECHNIQUE USED:

LINEAR VIBRATION WELDING

The materials are placed in contact and put under pressure in linear vibration welding.

ORBITAL FRICTION WELDING

The spin welding looks similar to friction welding.

In this process, more complex machines are needed for producing an orbital motion in which the moving part rotates in a small circle, much smaller than the size of the joint as a whole.

LIST CONNECTED TO FRICTION WELDING:

Forge welding.

Friction stir welding.

Friction stir spot welding.

Linear friction welding.

Friction welding of pipeline girth welds.

Friction hydro pillar overlap processing.

Friction hydro pillar processing.

Linear vibration welding.

Low force friction Welding.

ADVANTAGES:

During the short time cycle it can produce high quality welds.

There is no requirement of filler metal and also flux is not used.

For welding most of the common metals this method plays an important role.

For joining of many combinations of dissimilar metals this method is mostly preferred.

For this, it requires a relatively expensive apparatus similar to a machine tool.

Easy to operate equipment which is not time-consuming.

Low levels of oxide films and surface impurities.

DISADVANTAGES:

This process only limited to angular and flat butt welds.

Only used for smaller parts.

This method gets much complicated when it is used for tube welding, it gets much hard to remove flash when working with high carbon steel.

For creating high thrust pressure it requires heavy rigid machine.

APPLICATIONS:

Tongs hold to critical aircraft engine components.

Automotive parts like engine valve and shock absorber.

Hydraulic piston rod and track roller in agricultural equipment.

Friction welded assemblies are often used to replace expensive casting and forgings.

For the purpose of building better industrial rollers, tubes, and shafts this method is suitable.

For the manufacturing of the subassemblies for industrial printers, material handling equipment this method is mostly used.

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