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Welding and it’s types

Contents Solid state welding Cold welding Ultrasonic welding Friction welding Resistance welding

welding

It is defined as metal pieces or parts that are join together by heating the surfaces to the point of melting with electric arc, hammering etc.

Solid state welding

Def: A group of welding processes that join

metals at temperatures essentially below the melting points of the materials, without the addition of a brazing filler metal. Pressure may or may not be applied to the joint. Examples include cold welding , ultrasonic wielding, friction wielding etc.

1)Cold welding

Cold welding is a solid state process in which pressure is used at room temperature to produce coalescence of metals with substantial deformation at the weld. both butt and lap joints can be cold welded.

Characteristics of cold welding

At least one of the metals must be ductile without excessive work hardening

Total absence of applied heating Dissimiliar metals can be jointed. Surface preparation is important.

Cold welding equipment

A manually operated cold welding equipment

Cold welding process

The parts to be welded are first cleaned

A short section of the part is sheared

The parts are clamped in a die with some initial extention

A forging force is applied to complete welding.

Dies

Workpiece Workpiece

Before welding

After welding

Application of cold welding

Cold welded butt joints are used in the manufacturing of aluminium ,copper ,gold, silver, and platinum wire.

Most commonly, successive reels of wire are joined for continuous drawing to a smaller diameter.

Manufacture of kitchen utensils.

Ultrasonic welding

Def: A solid state welding process in which

coalescence is produced at the faying surfaces by the application of high frequency vibratory energy while the work pieces are held together under moderately low static pressure.

Ultrasonic welding process

Components of ultrasonic welding system include

1)transducer 2)sonotrode 3)anvil

Anvil

Mass

Sonotrode tip

Clampingforce

wedgeTransducer

Force

WeldmentVibration

Mechanism

A static clamping force is applied perpendicular to the interface between the work pieces.

The contacting sonotrode oscillates parallel to the interface.

Combined effect of static and oscillating force produces deformation which promotes welding.

Anvil

Mass

Sonotrode tip

Clampingforce

wedgeTransducer

Force

WeldmentVibration

Advantages

No heat is applied and no melting occurs. Permits welding of thin to thick sections. Welding can be made through some

surface coatings. Pressures used are lower ,welding times

are shorter, and the thickness of deformed regions are thinner than for cold welding.

Limitations

The thickness of the component adjacent to the sonotrode tip must not exceed relatively thin gages because of power limitations of the equipment.

Process is limited to lap joints. Butt welds can not be made because

there is no means of supporting the work pieces and applying clamping force.

Friction welding

Def:Friction welding is a solid state joining process that produces coalescence by the heat developed between two surfaces by mechanically induced surface motion.

Types of friction welding

1)continuous drive friction welding 2)inertia welding

Continuous drive friction welding

One of the work pieces is attached to a rotating motor drive, the other is fixed in an axial motion system.

One work pieces is rotated at constant speed by the motor.

An axial or radial force is applied.

The work pieces are brought together under pressure for a predetermined time, or until a preset upset is reached

Then the drive is disengaged and a break is applied to the rotating work piece.

Workpieces

Non-rotating viseMotor

Chuck

SpindleHydraulic cylinder

Brake

Application

Frequently competes with flash or upset welding when one of the work pieces to be joined has axial symmetry.

Used in automotive industry to manufacture gears, engine valves, and shock absorbers.

Used to join jet engine compressor parts.

Inertia welding process One of the work piece is

connected to a fly wheel; the other is clamped in a non rotating axial drive.

The fly wheel is accelerated to the welding angular velocity.

The drive is disengaged and the work piece are brought together

Frictional heat is produce at the interface. An axial force is required to complete welding.

Spindle

WorkpiecesNon-rotating chuck

Hydraulic cylinder

FlywheelMotor

Chuck

Equipment

Similarities between continuous and inertia drive

In both mechanism welding heat is developed by frictional heat and plastic deformation

Both method use axial force for upsetting purpose.

In both mechanism axial pressure may be changed at the end of the rotation

Difference between continuous and inertia drive

Continuous drive1)One of the work pieces directly connected to a rotating motor drive.2)Rotational speed may be constant until the brake is applied.3)Rotational energy of the work piece dissipates through friction and plastic deformation, producing welding heat.

Inertia drive1)One of the work piece is connected to the fly wheel.2)Rotational speed decreases continuously to zero during the process.3)Kinetic energy of the fly wheel is dissipates through friction and plastic deformation producing heat

Resistance welding

The resistance welding process involves the joining of materials through the resistance of an electrical current.  The electrical current generates heat and pressure which creates bonds between the parts being welded.  Most resistance welding applications are applied to metals, but plastic materials may also be used.  This quick and efficient application uses machines with copper electrodes that inject materials with heat.  Once the desired amount of heat is injected, the materials begin to cool; a bond is formed during the cooling process.  What makes resistance welding different than regular welding is it uses both heat and pressure to weld, while regular welding only used heat.

Types of resistance welding

There are six different resistance welding processes; each process involves the formation of a bond through heat produced by an electrical current and pressure created by the electrodes to hold the materials together. 

Different resistance welding process

1)Resistance Spot Welding- This is when a bond is formed at the joining surface of the material being welded.

2)Projection Welding- This involves the bonding of metal materials.

3)Flash Welding- This is when a bond is formed over the entire area of the welded materials.

4)Upset Welding- This process connects materials progressively along a joint.

5)Percussion Welding- This is the welding of materials through heat produced by an arc due to a rapid discharge of energy.

6)High Frequency Resistance Welding- This is the production of a bind between metals by an alternating current.

Advantages

High speed< 0.1 seconds in automotive spot welds

Excellent for sheet metal applications, < ¼-inch

No filler metal

Disadvantages and limitations

Higher equipment costs than arc welding Nondestructive testing Low tensile and fatigue strength Not portable Lap joint require additional metal.

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