1. ELECTRON BEAM WELDING 2. FRICTION WELDING 3. FRICTION STIR WELDING

INTRODUCTION : EBW : “Fusion Welding Process in which a beam of high velocity electrons is applied to materials being joined”. Kinetic energy of electrons is transformed in to Heat Energy. Work pieces melt due to heat and joining occurs. Molten metal will flow to fill the gap.

DIAGRAM :

ELECTRON BEAM WELDING The electron beam gun has a tungsten filament which is heated, freeing electrons. The electrons are accelerated from the source with high voltage potential between a cathode and anode. The stream of electrons then pass through a hole in the anode. The beam is directed by magnetic forces of focusing and deflecting coils. This beam is directed out of the gun column and strikes the workpiece. The potential energy of the electrons is transferred to heat upon impact of the workpiece and cuts a perfect hole at the weld joint. Molten metal fills in behind the beam, creating a deep finished weld.

WORKING : Current is given to cathode in vacuum chamber and heated up to 2000 °C. So, electrons are emitted and will be attracted towards anode. Electrons are accelerated due to potential between anode and cathode. Electrons will pass through the hole and form a beam of high intensity.

Electron beam having High Power Density can be controlled by focusing coil. Electron beam will struck on work piece with high velocity and produce heat energy. So, metal will meltdown and molten liquid metal will flow in the gap. Thus , welding is performed and metals can be joined.

STEPS USED IN EBW PROCESS : Joint Preparation Cleaning of work pieces Fixturing of work pieces De-magnetization of work pieces Setting up work pieces in chamber Pump down air from chamber Carry welding process

ADVANTAGES : It is high quality welding. Very less defective because electron beam covers sharp area on metal which is being heated. Welding on reactive metal can be done easily in vacuum chamber. Butt joint process can be done without edge preparation in pieces having width up to 6 mm.

DISADVANTAGES : Primary costs are high. Transportation of equipments are not easy. Vacuum is required every time in chamber. Skilled persons are needed for process. Space in chamber is very small so cant useful for larger piece. Manipulation of work piece needs special care & instruments in chamber. Electron beam flows in straight line so if obstacle comes then welding will stop.

APPLICATION : Welding of reactive and refractory metal. For welding of two different metals like steel, copper, titanium etc. Automobile and aircraft

2. FRICTION WELDING

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

Categories of Friction Welding Continuous drive Inertia

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 piece is rotated at constant speed by the motor. An axial or radial force is applied. Workpieces Non-rotating vise Motor Chuck Spindle Hydraulic cylinder Brake

Contd.., The work pieces are brought together under pressure for a pre deter-mined time, or until a preset upset is reached. Then the drive is disengaged and a break is applied to the rotating work piece.

Friction Welding Variables (Continuous Drive) Rotational speed Heating pressure Forging pressure Heating time Braking time Forging time

Direct Drive Machine Courtesy AWS handbook