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.Solid State Welding 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. Carbon steelsAlloy steelsTool and die steels Stainless steelsAluminum alloysCopper alloysMagnesium alloysNickel alloys Titanium alloys

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.Solid State Weldingdiffusion 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, electronics, nuclear applications, manufacturing composite materials.composite materials

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.weld 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.airflame temperature 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.