FRICTION WELDING
Friction Welding
• Friction Welding is a Solid State Welding
process, in which two cylindrical parts are
brought in contact by a friction pressure when
one of them rotates.
• Friction between the parts results in heating
their ends.
• Forge pressure is then applied to the pieces
providing formation of the joint.
• Carbon steels, Alloy steels, Tool and die steels,
Stainless steels, Aluminum alloys, Copper
alloys, Magnesium alloys, Nickel alloys,
Titanium alloys may be joined by Friction
Welding.
Diffusion Welding
• Diffusion Welding is a Solid State Welding process, in which pressure
applied to two work pieces with carefully cleaned surfaces and at an
elevated temperature below the melting point of the metals. Bonding
of the materials is a result of mutual diffusion of their interface atoms.
• In order to keep the bonded surfaces clean from oxides and other air
contaminations, the process is often conducted in vacuum.
• No appreciable deformation of the work pieces occurs in Diffusion
Welding.
• Diffusion Welding is able to bond dissimilar metals, which are difficult
to weld by other welding processes: Steel to tungsten, Steel to
niobium, Stainless steel to titanium, Gold to copper alloys.
• Diffusion Welding is used in aerospace and rocketry industries,
Flame Cutting
• Oxy-fuel
welding
(commonly
called oxyacetylene welding, oxy welding,
or gas welding in the U.S.) and oxy-fuel
cutting are processes that use fuel gases and
oxygen to weld and cut metals, respectively.
• Pure oxygen, instead of air, is used to
increase the flame temperature to allow
localized melting of the workpiece material
(e.g. steel) in a room environment.
• A common propane/air flame burns at
about 2,000 °C (3,630 °F), a propane/oxygen
flame burns at about 2,500 °C(4,530 °F), and
an acetylene/oxygen flame burns at
about 3,500 °C (6,330 °F).
Welding Defects
Soldering
• Soldering and brazing are adhesive bonds,
whereas welding is a cohesive bond.
• Soldering is an operation of two or more
parts together by molten metal.
• Soldering should not be used where much
strength is required, where the joint will be
subjected to vibration or heat.
Classification of Soldering Methods
• Soldering iron methods
• Torch method
• Dip and wave methods
• Induction method
• Resistance method
• Furnace and hot plate method
• Spray method
• Ultrasonic method
• Condensation method
Types of Solder
1. Soft Solder, which is usually a lead-tin
mixture.
2. Hard solders
1.
Brass solders (Copper-zinc alloy)
2.
Silver solders (Copper-silver alloy)
3.
Copper solders
4.
Nickel-silver solders
Flux or Soldering fluid
• During soft soldering flux is necessary to cover the
surface of the components and solder with a film so
that the formation of an oxide is prevented.
• Fluxes are of two kinds:
– Those which not only protect the surface, but play an
active chemical part in cleaning it.
Ex: Zinc chloride(killed sprits), Ammonium chloride.
– Those which protect previously cleaned surface.
Ex: Tallow, resin, vaseline, olive oil. (Fluxite)
Advantages
• Low cost.
• Simplicity and cheapness in equipment.
• Properties of base metal not affected.
APPLICATIONS
• Connection in wireless set(radio), T.V sets.
• Wiring joints in electrical connections,
battery and other terminals.
Brazing
• Brazing is a soldering operation using brass as the joining medium
• It is simply a form of hard soldering using a copper-zinc alloy.
• Brass used for making the joint in brazing is called as “Spelter”
• Three brazing alloys are:
– Copper-70%, Zinc-30%; Melting point-960˚C
– Copper-60%, Zinc-40%; Melting point-910˚C
– Copper-50%, Zinc-50%; Melting point-870˚C
– The filler penetrates the gap by capillary attraction.
Fluxes
• When hard soldering, the chief flux is
borax(Powder, granulated or stick form).
• Action of the flux:
– To prevent an oxide forming.
– A cleansing medium to remove dirt.
– It aids the capillarity of the molten metal.
Brazing Methods
• Torch brazing
• Furnace brazing
• Resistance brazing
• Induction brazing
• Dip brazing
• Laser brazing and Electron beam brazing
Brazing Procedure
• The surfaces to be joined are thoroughly cleaned.
• Then a paste of flux and spelter is kept in the joint.
• Flame is directed over the joint.
• The flux and spelter will soon melt and fill the recess
between the joint.
• When the joint is hot common salt is put to soften
the glossy hard flux.