15038_modern welding processes2

Plasma Arc Welding

PLASMA ARC WELDING

PLASMA ARC WELDING

PLASMA ARC WELDING

Inner orifice-Argon gas-plasmaArc- concentrated and straightNozzle-squeezing actionConstricted Arc – 11,000 ⁰CKeyhole technique – downhand weldingHigh metal deposition rateLess HAZExpensive equipmentFrequent replacement of nozzle

FRICTION WELDING

SolidState

Welding

Electrical

Chemical

Mechanical

Friction Pressure &Deformation

FrictionWeld

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

Definition of Friction Welding

Continuous drive

Inertia

Categories of Friction Welding

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

One workpiece is rotated at constant speed by the motor.

An axial or radial force is applied.

Continuous Drive

WorkpiecesNon-rotating viseMotor

ChuckSpindle Hydraulic cylinder

Brake

Continuous Drive Friction Welding

The work pieces are brought together under pressure for a pre-determined time, or until a preset upset is reached.

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

Continuous Drive

WorkpiecesNon-rotating viseMotor

ChuckSpindle Hydraulic cylinder

Brake

Continuous Drive Friction Welding

One of the work pieces is connected to a flywheel; the other is clamped in a non-rotating axial drive

The flywheel is accelerated to the welding angular velocity.

The drive is disengaged and the work pieces are brought together.

Frictional heat is produced at the interface. An axial force is applied to complete welding.

Inertia Drive

Spindle

WorkpiecesNon-rotating chuck

Hydraulic cylinder

FlywheelMotor

Chuck

Inertia Welding Process Description

Friction Welded Hand Tools A Jet Engine Compressor Wheel Fabricated by Friction Welding

Applications

Courtesy AWS handbook

Friction Welds

Aluminum to Steel Friction Weld

Dissimilar Metals – Friction Welded

One of the work pieces is connected to a flywheel; the other is clamped in a non-rotating axial drive

The flywheel is accelerated to the welding angular velocity.

The drive is disengaged and the work pieces are brought together.

Frictional heat is produced at the interface. An axial force is applied to complete welding.

Inertia Drive

Spindle

WorkpiecesNon-rotating chuck

Hydraulic cylinder

FlywheelMotor

Chuck

Inertia Welding Process Description

Titanium Engine Valve

Titanium AluminidesorTitanium Borides(Brittle at RT)

Titanium Alloy(Ductile)

Inertia Weld

Jette, P , Sommer, A., “Titanium Engine Valve”, US Patent 5,517,956 May 21, 1996

Diffusion Welding

A solid-state welding process that produces coalescence of the faying surfaces by the application of pressure at elevated temperature.

The process does not involve macroscopic deformation, or relative motion of the workpieces.

A solid filler metal may or may not be inserted between the faying surfaces.

Work pieces

Schematic representation ofdiffusion welding using electrical resistance for heating

A

B

Force

Diffusion Welding

Welding ProcessesDiffusion Welding

• Parts forced together at high temperature (< 0.5Tm absolute) and pressure

Kalpakjian, S., Manufacturing Engineering & Technology, p. 889, 1992

• Atoms diffuse across interface

• After sufficient time the interface disappears

• Good for dissimilar metals

• Heated in furnace or by resistance heating

• Bond can be weakened by surface impurities

1st stagedeformation forming

interfacial boundary.2nd stage

Grain boundary migration and pore elimination.

3rd stageVolume diffusion and

pore elimination.

asperities come into contact.

2nd stage grainboundary migrationand pore elimination

1st stage deformationand interfacial boundary formation

3rd stage volumediffusion poreelimination

Diffusion Welding Working Principles

J1

= - D 1dcdx

Mass L2t

L2 t

Mass/L3 L

2 MethodsInert gasDead weights (for ferrous metals)

Features & ApplicationsMetallurgically soundNo further processingLarge area-making laminates

Plate/Fin heat exchanger (Titanium alloy)

History of Explosive weldingDuring the first world war it was observed

that fragments of steel shells of bombs occasionally stuck to metallic objects in the vicinity of the explosion. This, had it been realized, was an example of explosive welding.

Explosive welding was perhaps first noted by Carl in 1944.

Principle of ExplosionCladder metal can be placed parallel or

inclined to the base plateExplosive material is distributed over top of

cladder metalUpon detonation, cladder plate collides with

base plate to form weld

AdvantagesNo heat-affected zone (HAZ)Only minor meltingMaterial melting temperatures and

coefficients of thermal expansion differences do not affect the final product

The shock front compresses and heats the explosive material which exceeds the sonic velocity of undetonated explosives

AdvantagesSimplicity of the process.Welds can be produced on heat treated

metals without affecting their microstructures.

Lack of porosity, phase changes and structural changes impart better mechanical properties to the joints.

Limitations • In industrial areas use of explosives will be

severely restricted by the noise and ground vibration caused by explosion.

• Metals to be bonded by this process must possess some ductility and some impact resistance. Metals harder than about 50RC are extremely difficult to weld.

• Metal thickness grater than 62mm of each alloy cannot be joined easily and require high explosive loads.

ApplicationsCan weld large areas of metalCan weld inside and outside surfaces of pipesTransition joints can be made

Common industries that use explosion welding

• Chemical ProcessingPetroleum RefiningHydrometallurgyAluminum SmeltingShipbuildingElectrochemicalOil & GasPower GenerationCryogenic ProcessingPulp & PaperAir conditioning & ChillersMetal Production

Examples

Examples

3” Diameter AI/SS Ring Copper/Stainless 12” UHV Assembly